DE4104044C1 - Pneumatic switching valve for raising and lowering aircraft fuselage - has pressure-operated control chamber coupled to return pocket via magnetic valve during switch=over to stop position - Google Patents

Abstract

Air suspension is used to control positions for lift, lower, go and stop. A throttle (32) for narrowing the flow cross-section is provided in the pipe (31) leading from the return space (27) to atmosphere. The control chamber (26) is connected via the magnetic valve (34) to the return space on switching to the stop positioon. ADVANTAGE - Danger of over-control avoided.

Description

The invention relates to a pneumatic switching valve with the features specified in the preamble of claim 1.

Such pneumatic switching valves are often used in conjunction with level control valves on air-sprung vehicles with corresponding air bellows and a control device used for arbitrary control of the switching valve.

A pneumatic switching valve of the type described in the introduction is known from DE-PS 34 24 670. On the valve housing this Switching valve are two over the control device controllable solenoid valves are provided which are connected to a Compressed air supply are connected and not excited State control chambers of two separately controllable Shut off the switching piston from the compressed air supply and the Control chambers via their own, provided on the solenoid valves Vent the vents into the atmosphere. The two Shift pistons, which are telescoped and sealed in the housing are slidably mounted, have a common back space connected to the atmosphere is to move the switching piston in the housing of the Switching valve the necessary air exchange with the To ensure atmosphere. There is also a on the housing Outlet provided for the ventilation of the air bellows, the is usually comparatively large in cross section quick ventilation of the air bellows if necessary enable. It is also possible to go to the Air spring bellows leading a quick release valve turn on and then through the outlet on the housing vent the corresponding control line.

Such pneumatic switching valves are one Compressed air supply connected, depending on the training of the  Vehicle at a more or less high maximum Pressure level can work. So this can be maximum Pressure level in the range between 6.5 and 13 bar lie.

The two shift pistons are for their own purposes Return on one or more return springs supported, which are tuned to the lowest pressure level must be with which, as expected, the switching valve to be operated.

With a usual assignment of the four Positions of the switching pistons relative to one another to the positions Lifting, lowering, driving and stopping it is necessary for the The control chambers move from one position to the other must be alternately aerated and / or vented. A such switching state occurs in particular at the end of one Lowering movement of the vehicle body when out of position Lowering to the stop position is switched like this for example when lowering a vehicle body Adaptation to the height of a fixed ramp when loading or Discharge processes is the case.

With less favorable geometric dimensioning and when supplying the Solenoid valves over a particularly high pressure level there may be a risk of overdriving that at the transition between the lower and stop positions a relative position of the Switching piston and thus the individual slide (s) occurs, which is assigned to the lifting position. This in mind an intermediate position that occurs is overdriven always taken for a very limited time only; she is however, when it occurs, bothersome and u. Maybe even dangerous.

Furthermore, the majority of this known switching valve of the ventilation openings on the housing or on the Solenoid valves disadvantageous because they are increased Risk of contamination in the sense of the ingress of dust and Place foreign objects in the interior of the housing. Also entice such vents to introduce  Antifreeze and other lubricants, but one proper functioning of the switching valve is a hindrance are.

The switching valve has at least one single slide, but preferably two or three individual slides, which expediently together through the two switching pistons in the different relative positions are applied or guided.

From DE-PS 39 15 826 or DE-PS 39 15 827 Similar switching valves are known, in which also the There is a risk of overdriving. Although with these Switching valves connecting the common back space to the Atmosphere and the ventilation opening for the air bellows in a common outlet on the housing of the switching valve assembled, however, the two solenoid valves have continue to each have a separate and independent Vent.

The invention has for its object a pneumatic Switching valve of the type described in the introduction further training that eliminates the risk of oversteer and the switching valve is nevertheless of different heights Reservoir pressures can be operated.

According to the invention, this is indicated by that in claim 1 Characteristics achieved.

The one that narrows the flow cross-section Element can have a constant, narrowed cross section provide; it can be adjustable. Furthermore, it can also be designed so that in time Sequence of different flow cross sections provided are, from a closed position to in an open, throttling position.

At least the outlet of the in the lower position of the solenoid valve is not more than additional outlet provided, but leads from it one Line connection to the rear of the control piston, and the A line leading from the back room to the atmosphere also serves from the solenoid valve, which is in the lower position  is excited to drain from the relevant tax chamber To release control air into the atmosphere.

One becomes expedient but do not treat the solenoid valves differently, but also the vent line of the other solenoid valve lead over the back room. So that the number of openings reduced on the valve body.

At least that Vent line of the solenoid valve that is in the position Lowering (and also lifting) is excited, but advantageously both Vent lines of the solenoid valves are direct or indirectly to the common rear space of the two switching pistons connected, in such a way that that from a control chamber escaping compressed air by switching the solenoid valve the control chamber is transferred to the common rear area and in this way an additional force to Support of the return spring for the switching pistons represents.

This has the advantage that the Return spring or the return springs for the switching pistons can be interpreted relatively weaker. The occurs further advantage that the switching valve its individual Switch positions more reliable and also faster in time occupies than before. The fits in together Rear space acting on the switching piston, the corresponding counter-force on the control chamber side is automatically increased in height, and that when that Switching valve is used in vehicles whose Compressed air procurement facilities to different heights maximum supply pressures are designed.

The constricting element can be used as a throttle, check valve, Overflow valve, pressure retention valve or the like be. Training as a double check valve is also possible. A choke can be, for example, by the Realize arrangement of a nozzle or the like. The Check valve is installed so that it is in the outlet direction opens. An overflow valve is a valve which at increasing pressure is initially closed and only  above, d. H. after reaching a corresponding one Pressure level opens. A pressure retention valve can have preloaded pistons and only at higher pressure to open. The through the bias of such a valve the trapped air in the rear area on the control pistons acting force supports the force of the return springs, because it works in the same sense. In general it is included pressure to supply pressure, however, comparatively small and is only a fraction of a bar.

The line leading from the back room to the atmosphere, the loading and Vent lines for the control chambers and the Outlet lines for venting the air bellows can end at the outlet on the housing, this outlet being the only one forms a common ventilation opening on the housing. This provides the advantage that the risk of pollution, with the arrangement of several ventilation openings is connected, is significantly reduced. Even such a common one Outlet can also be of relatively large cross-section and e.g. B. can be used to arrange a silencer. This is an additional protection against that Penetration of dirt is provided at this single outlet, and without much effort.

The two solenoid valves can be in a common block be provided and their two ventilation lines can already be merged into the block, so that so that cable length is saved within the housing.

Both combined ventilation lines can to the from Line leading to the atmosphere must be connected, so that part of this line in both flow directions is used. It goes without saying that this connection must be in the direction of flow before the constricting element.  

Both solenoid valves can with their in the common outlet venting lines for the control chambers via the Be led back room. This comes from constructive Reasons.

The invention is based on preferred exemplary embodiments further explained and described. Show it:

Fig. 1 shows a section through the switching valve in a first embodiment with indication of connections in the drive position,

Fig. 2 shows a section through the switching valve of FIG. 1 in the lowering position,

Fig. 3 shows a section through the switching valve of FIG. 1 in the stop and position

Fig. 4 shows a section through the switching valve in a second embodiment in the driving position.

The pneumatic switching valve has a suitably multi-part housing 1 , in which two individual slides 2 , 3 are provided in the manner shown and are slidably mounted. The single slide 2 is slidably mounted in a stepped bore 4 and the single slider 3 in a stepped bore 5 . It would also be possible to provide only one single slide or, for example, three individual slides in this manner, which is basically illustrated. The diameters of the individual slides 2 and 3 are stepped over the length and adapted to the stepped formation of the bores 4 and 5, respectively. The individual slides 2 and 3 each have a thickening 6 with a seal 7 at their lower end. A further thickening 9 with a seal 10 adjoins a part 8 tapered in diameter. Relative to this, a third thickening 12 with a seal 13 is provided with the interposition of a further tapered part 11 . The individual slides 2 and 3 are of identical design and are arranged coaxially next to one another.

The bore 4 merges into an outlet 14 at its lower end. This outlet 14 represents the only ventilation opening on the housing 1. Below the bore 5 , a storage chamber 15 is provided, in which compressed air from a compressed air reservoir 18 is present via a connection 20 and a line 17 . Between the storage chamber 15 and the bore 5 , an inlet valve 19 , 20 is provided from a valve body 20 pressed resiliently against a housing edge 19 . The valve body 20 or the inlet valve 19 , 20 is normally closed and is actuated by the lower end of the single slide 3 . In the lower region, the two bores 4 and 5 are connected to one another by a channel 21 which extends through the housing 1 .

To drive the two individual slides 2 and 3 , a piston arrangement comprising two switching pistons 23 and 24 is provided in the housing 1 in a cylindrical bore 22 or is mounted in a sealed manner with the aid of the seals shown. The two switching pistons 23 and 24 are arranged telescopically one inside the other and divide a first control chamber 25 in the housing and a second control chamber 26 between the switching pistons 23 and 24 . A common rear space 27 is formed on its rear side, in which a common return spring 28 is also arranged. The switching piston 24 is movable in the switching piston 23 , its stroke by a stop 29 , for. B. in the form of a retaining ring is limited. A stop 30 on the housing 1 limits the stroke of the switching piston 23 . As can be seen, the strokes are designed differently so that a total of four different positions result from corresponding actuation or actuation of the control chambers 25 and 26 , which positions are assigned to the positions of lifting, lowering, travel and stop. In Fig. 1 the position driving is shown. Fig. 2 shows the lowering position and Fig. 3 shows the stop position.

The rear space 27 is connected to the outlet 14 via a line 31 . In this line 31 an element 32 narrowing the cross section, here in the form of a choke, is arranged. Instead of a throttle, a check valve 33 ( FIG. 4), an overflow valve, a pressure retention valve or the like can also be provided.

For the actuation of the two switching pistons 23 and 24 or the individual slide 2 and 3 in the four positions of lifting, lowering, driving and stopping, a control device (not shown in detail) is provided, which has two solenoid valves 34 and 35 as essential components, the cores 36 and 37 are accommodated in corresponding recesses in a common block 38 as part of the housing 1 . This block 38 is usually flanged to the housing 1 . The cores 36 and 37 form, with seats 39 and 40 , inlet valves 36 , 39 and 37 , 40 , respectively, at which compressed air from the compressed air reservoir 18 is present via a branching line 41 . A line 42 leads from the solenoid valve 34 to an annular space 43 on the housing 1 , which is arranged between the two seals of the switching piston 23 . One or more openings 44 in the switching piston 23 make it possible to act on the control chamber 26 .

A line 45 leads from the solenoid valve 35 to the control chamber 25 of the first switching piston 23 . Seats 46 and 47 form outlet valves 36 , 46 and 37 , 47 on the two solenoid valves 34 and 35 with the cores 36 and 37 . A vent line 48 leads from the seat 46 and a vent line 49 leads from the seat 47 to the common rear space 27 on the one hand and to the outlet 14 via the narrowing element 32 . For this purpose, the two ventilation lines 48 and 49 are combined in one ventilation line 50 , which, seen in the outflow direction, is connected to the line 31 in front of the constricting element 32 . So that both vent lines 48 and 49 of the two solenoid valves 34 and 35 are connected to the common rear space 27 and the outlet 14 and thus the atmosphere.

A line 52 branches off from a connection 51 , which branches off from the bore 4 at the position shown, ie (in the travel position) between the seals 7 and 9 , to an air bellows 53 . Correspondingly, with respect to the individual slide 3 , a line 55 is connected to a connection 54 , which leads to an air bellows 56 . The two air suspension bellows 53 and 56 can be assigned to different axles, different vehicle sides or the like.

A first level control valve 57 is supplied with compressed air via a compressed air reservoir 58 and a line 59 . From it, a line 60 leads to a connection 61 on the bore 4 of the single slide 2 . Correspondingly, for the second air spring circuit, a level control valve 62 , which is supplied with compressed air via a line 63 , is connected by means of a line 64 to a connection 65 , which is arranged at the position shown in the bore 5 of the individual slide 3 .

In Fig. 1 the travel position of the switching valve is shown, ie the two solenoid valves 34 and 35 are not energized, so that the inlet valves 36 , 39 and 37 , 40 are closed and the outlet valves 36 , 46 and 37 , 47 are open. So that the two control chambers 25 and 26 of the switching pistons 23 and 24 are vented, so that the force of the return spring 28 is sufficient to hold the two switching pistons 23 and 24 in their upper position in contact with the housing 1 , so that the individual slide 2 and 3 Take the relative position in question in the housing 1 , in which only the seals 7 and 13 fulfill their sealing function, while the seal 9 does not fulfill a sealing function. Thus the bores 4 and 5 are closed at the bottom, but the connection 61 is connected to the connection 51 and there is also a connection between the connection 65 and the connection 54 . The required pressure in the air bellows 53 and 56 is thus controlled in the travel position via the level control valves 57 and 62 .

In order to lower the vehicle body, for example on a ramp for the purpose of loading or unloading, the lower position is activated, which is shown in FIG. 2. For this purpose, the solenoid valve 34 is energized, while the solenoid valve 35 remains de-energized. As a result, the inlet valve 36 , 39 on the relay valve 34 is opened and the outlet valve 37 , 47 is closed. As a result, compressed air can get from the compressed air reservoir 18 via the lines 41 and 42 into the control chamber 26 , so that the switching piston 23 maintains its starting position according to the travel position, but the switching piston 24 executes its stroke, so that both individual slides 2 and 3 together in the reach position shown in FIG. 2.

The displacement of the individual slide 2 and 3 results in connection with the stepped bores 4 and 5 such a relative position, in which the seals 9 and 13 fulfill the sealing function, while the seals 7 reach an enlarged area of the channel 21 , so that they are there do not perform a sealing function. As a result, the level control valves 57 and 59 are shut off, while the air bellows 53 and 56 are vented via the common outlet 14 . The vehicle body therefore drops as long as the lowering position is maintained. As soon as the desired lowered position is reached, the solenoid valves 34 and 35 are reversed so that the switching valve assumes its stop position shown in FIG. 3. By reversing the solenoid valve 34 during the transition from the lower position to the stop position, its previously open inlet valve 36 , 39 is closed and its previously closed outlet valve 36 , 46 is opened, so that the control air previously located in the control chamber 26 corresponds to the maximum operating pressure can flow out of the compressed air reservoir 18 , and not, as previously, directly into the atmosphere, but by connecting the ventilation line 48 to the line 42 via the ventilation line 50 and part of the line 31 into the common rear space 27 . It is important that in the flow direction into the atmosphere of the constricting element 32 at the point shown, that is to say in any case after the connection of the vent line 50 to the line 31 , so that a corresponding pressure build-up takes place in the rear space 27 and the force of the return spring 28 supporting actuating force for the relative displacement of the switching piston 24 to the switching piston 23 is used. This at the same time prevents an oversteer that could lead to the intake valve 19 , 20 being unintentionally pushed open briefly by the individual slide 3 . The maximum operating pressure in the compressed air reservoir 18 can, depending on the vehicle and design, be set approximately in the order of magnitude between 6 and 13 bar, so that, in relation to the geometric conditions, the return spring 28 must in any case be designed so weakly that a low operating pressure for actuating the Shift pistons 23 and 24 are sufficient. At low operating pressures, there is far less risk of oversteering than at high operating pressures.

In the stop position, all lines in the area of the individual slide 2 and 3 are closed.

It is understood that in the lifting position, not shown, the individual slides 2 and 3 assume their fourth position, in which the two strokes of the two switching pistons 23 and 24 add up, so that the inlet valve 19 , 20 is pushed open from the lower end of the single slider 3 and in this way compressed air from the compressed air reservoir 18 can flow into the air bellows 53 and 56 . This will raise the vehicle body. Such a lifting movement is in turn ended by activating the stop position according to FIG. 3.

Fig. 4 shows a further embodiment of the switching valve in the driving position. Here only the vent line 48 is led to the common rear space 27 . The vent line 48 is connected directly to the rear space 27 , that is to say without prior connection to the line 31 . Of course, the narrowing element, for. B. in the form of the check valve 33 , provided in the line 31 . The vent line 49 of the solenoid valve 35 is led directly to the connection 14 and ends there in a transverse bore 66 . In all embodiments of the switching valve, only a single outlet 14 , which is used for ventilation, is provided. The air bellows 53 and 56 as well as the solenoid valves 34 and 35 and also the rear space 27 are vented in this way.

Claims (6)

1.Pneumatic switching valve for systems for lifting and lowering the vehicle body of air-sprung vehicles with a control device for the positions lifting, lowering, travel and stop, in which in one housing two switching pistons can be controlled separately via two solenoid valves with different switching paths for the common, same-directional actuation of At least one control spool assigned to an air spring circuit is provided, the switching pistons in the housing on the upstream side dividing two separate control chambers which can be acted upon by one of the two solenoid valves and an associated ventilation line and on the back a common rear chamber connected to the atmosphere via a line and an outlet for venting the air bellows is provided on the housing, characterized in that in the line ( 31 ) leading from the rear space ( 27 ) to the atmosphere, an element ( 32 ) narrowing the flow cross-section is provided and that at least the control chamber ( 26 ) pressurized in the lower position is connected to the rear space ( 27 ) via the associated solenoid valve ( 34 ) when switching to the stop position. 2. Switching valve according to claim 1, characterized in that the constricting element ( 32 ) is designed as a throttle, check valve ( 33 ), overflow valve, pressure retention valve or the like. 3. Switching valve according to claim 1 or 2, characterized in that from the rear space ( 27 ) leading to the atmosphere line ( 31 ), the ventilation lines ( 42 ; 48 ; 45 ; 49 ) for the control chambers ( 26 ; 25 ) and the outlet lines for venting the air bellows ( 53 ; 56 ) end at the outlet ( 14 ) on the housing and this outlet ( 14 ) forms the only common vent opening on the housing ( 1 ). 4. Switching valve according to one or more of claims 1 to 3, characterized in that the two solenoid valves ( 34 , 35 ) are provided in a common block ( 38 ) and their two ventilation lines ( 42 ; 48 ; 45 ; 49 ) are brought together in the block ( 38 ). 5. Switching valve according to claim 4, characterized in that the two merged ventilation lines ( 42 ; 48 ; 45 ; 49 ; 50 ) are connected to the line ( 31 ) leading from the rear space ( 27 ) to the atmosphere. 6. Switching valve according to one of the preceding claims 1 to 5, characterized in that both solenoid valves ( 34 ; 35 ) with their in the common outlet ( 14 ) ending ventilation lines ( 48 ; 49 ) for the control chambers ( 26 ; 25 ) via the rear space ( 27 ) are performed.