DE102007020321A1 - Method for operating pneumatic controlling device for supplying specified controlled air pressure into consumer line, involves guiding consumer line to user - Google Patents

Abstract

The method involves guiding a consumer line to a user. A ventilation level (VS) is provided with an input valve (12), which is connected to a supply line (P) for aeration of the consumer line. An outlet valve (14) is provided for deaeration (R) between the consumer lines.

Description

The The invention relates to a method for operating a pneumatic device for providing a predeterminable Ansteuerluftdrucks in one leading to a consumer Consumer line and an associated pneumatic control device.

Such Pneumatic control devices are used in particular there, where a particular not constant supply air pressure in a prescribed, in particular over the time changing Control air pressure for to convert a consumer. As a consumer, in particular a retarder may be considered as a wear-resistant retarder in trucks and buses may be provided. Such retarders are with a predefinable, from the operation dependent on the brake Controlled control air pressure, wherein the predetermined Ansteuerluftdruck or over a corresponding amount of air a proportional amount of oil in the working space of the retarder between a rotor and a stator packed becomes. Depending on the amount of oil between rotor and stator is then a deceleration of the rotor and so that the entire vehicle.

Just at over a driving air pressure to be controlled consumers on board of a vehicle must, on the one hand, usually vary widely Supply pressure constant and on the other dependent on the respectively predetermined Control air pressure changed become. Especially for larger vehicles are driving air pressures reached up to 8 bar, with a comparatively accurate regulation the pressures in particular in the range of ± 0.1 bar possible should be. In addition, in the consumer line in comparatively a short time a high pressure increase or a high pressure reduction can be achieved, so that the Consumers react comparatively quickly.

Of the The present invention is therefore based on the object, a method or a pneumatic control device of the aforementioned To provide type, at relatively high Ansteuerluftdrücken, in particular at 8 or more bar, allow a comparatively simple control.

These The object is achieved by a method having the features of the claim 1 solved.

One Such method for operating a pneumatic control device, a connectable to a supply line inlet valve for ventilation of the Consumer line and one between the consumer line and one vent has provided drain valve, characterized in that the inlet valve is pulsed at a predetermined drive frequency is controlled and the drain valve proportional to the specified Control air pressure is controlled.

special Advantage of such a method is that the consumer line pressure although in dependence the respective predetermined control air pressure, but independent of the knowledge of the actual Consumer line pressure can be regulated. In this respect, additional Pressure measuring means or additional control means, the the inlet valve and the drain valve depending on the actual Control consumer air pressure, omitted.

One Such method also has the advantage that in the pneumatic control device the high, on the supply line pending air pressure over the pulsed controlled inlet valve is lowered and then the Discharge valve proportional only to this lowered air pressure must be moved to the specified control air pressure. Due to the lower pressures In the device, the control of the drain valve can be easier and more accurately, as if a constantly high air pressure at the drain valve is applied. In addition, the air consumption due to the reduced air pressure reduced overall.

Further is advantageous if the drive frequency of the intake valve so chosen is that occurring at the discharge valve pressure fluctuations the valve body of the Keep drain valve at least largely in constant motion. This has the advantage that no frictional forces are to be overcome when starting up of the valve body are available from a rest position. This can give a higher overall accuracy the driving air pressure ensured become.

In a particularly preferred embodiment of the invention, it is provided that the method described is used only in an emergency operation of the pneumatic control device, in which the actual actual consumer line pressure, for example due to a failure of a pressure measuring sensor in the Verhaucherleitung, unknown, and that in a normal operation of Pneumatic control device, in which the respective actual consumer air pressure is known, depending on the respectively predetermined Ansteuerluftdruck and the respective consumer line pressure, the inlet valve for increasing the pressure with a closed discharge valve is driven in particular pulsed. In order to reduce the pressure, the discharge valve can also be actuated in a pulsed manner, in particular when the inlet valve is closed. Namely, the method described above has the advantage that, independently of the knowledge of the actual consumer line pressure, it controls the control of the consumer line pressure proportio Nal to the predetermined control air pressure allows.

Further is advantageous if the input stage downstream of a main stage is, in normal operation of the pneumatic control device when exceeded a first threshold of a control pressure in a fast ventilation position and / or falls below a second threshold value of the control pressure switches to a quick exhaust position, in emergency operation, the drive frequency of the intake valve so chosen is that the pressure fluctuations arising in the consumer line are so small that the first threshold is not exceeded and / or the second Threshold is not fallen below. This ensures a total, in providing such a main stage, these are not due to the pulsed activation of the intake valve unintentionally opens or closes.

at a further embodiment The invention provides that the control pressure from the difference between that of a throttling point provided in the consumer line upstream air pressure and the throttle point downstream air pressure is formed. The choice of such a control air pressure has the Advantage that this independent of absolute pressure values, because it is a pure differential pressure.

In addition, according to the invention be provided that in normal operation for quick ventilation when exceeded of the first threshold opens a main stage inlet valve, thereby the supply line, bypassing the throttle point with the Consumer line is connected, due to the by the Quick ventilation taking place pressure equalization falls below the first threshold or another threshold closes the main stage inlet valve again and / or in normal operation for quick exhaust when falling below the second Threshold opens a main stage drain valve, causing the consumer line bypassing the throttle point is connected to the vent, wherein due to the pressure equalization due to the quick exhaust when exceeding the second threshold or other threshold, the main stage drain valve closes again. In such a normal operation, a comparatively accurate Regulation of the air pressure, in particular in the range of +/- 0.1 bar take place, in addition, a rapid pressure build-up or a quick pressure relief due to the purely pressure-controlled Main stage inlet valve and the likewise purely pressure-controlled main stage drain valve allows becomes.

The Main stage inlet valve is thus designed so that it is in normal operation while a compressed air supply to the consumer when a first threshold is exceeded the control pressure from a closed normal position in one Quick venting position switches, in which the supply line, bypassing the throttle point connected to the consumer line, due to the by the quick ventilation taking place pressure equalization falls below in particular the first threshold, or other threshold, the main stage inlet valve closes again.

The Hauptstufe drain valve is in contrast designed such that at a compressed air discharge from the consumer falls below a second threshold of the control pressure it from a closed Normal position switches to a quick exhaust position, in the consumer line bypassing the throttle point with connected to the vent is. Due to the quick exhaust, pressure equalization takes place and exceeds this in particular the second threshold or another threshold, includes the main stage drain valve again.

A Such control device has the advantage that on the one hand in the Normal position of the main stage with the main stage inlet closed and exhaust valve the pressure control over the input stage very exactly, in particular in the range of ± 0.1 bar, can be done.

There after a successful quick ventilation the main stage inlet valve due to the pressure equalization taking place closes again, can immediately after the fast ventilation a fine control of the Consumer pressure on the higher Pressure level over a corresponding control of the input stage done.

The same applies to a quick exhaust. As with the quick exhaust due to the pressure equalization taking place, the main stage drain valve closes can also be a fine control of the consumer air pressure on the lower pressure level exclusively via a corresponding control the input stage done.

Basically the closing the main stage intake valve at one of the first threshold, in which the main stage inlet valve is opened, different threshold respectively. Accordingly, basically, the main stage drain valve at a different threshold from the second threshold at which it is opened getting closed. In practice, however, has been beneficial exposed when closing the respective main stage valve then takes place when the threshold, where it opened is reached again after pressure equalization.

The object mentioned at the outset is also achieved by a method according to the invention leading or to carry out pneumatic control device having an input stage having a connectable to a consumer line inlet valve for ventilation of the consumer line and a lying between the consumer line and a vent relief valve for venting the consumer line and solved with an electronic control unit for controlling the intake valve and the exhaust valve.

In the case, that the pneumatic control device in a normal mode and a Emergency operation is operable, is then to determine the consumer line pressure a pressure sensor is provided, wherein in normal operation, the inlet valve and the drain valve depending the consumer line pressure is controlled by the control unit become.

to fast ventilation or venting can be provided that the pneumatic control device also a the main stage downstream main stage with a main stage inlet valve and a main stage drain valve formed in such a manner are that in normal operation of the pneumatic control device when exceeded a first control pressure in a fast ventilation position and / or at Fall below a second control pressure in a venting position.

Further is advantageous if the consumer line a throttle point provides, the control pressure from the difference between the Throttle upstream air pressure and the throttle point downstream air pressure is formed.

The Main stage inlet valve and main stage drain valve are included Preferably designed such that in normal operation for quick ventilation when exceeded of the first threshold opens the main stage inlet valve, thereby the supply line, bypassing the throttle point with the Consumer line is connected, due to the by the Quick ventilation taking place pressure equalization falls below the first threshold or another threshold closes the main stage inlet valve again, and / or that in normal operation for quick exhaust when falling below the second threshold opens the main stage drain valve, causing the Consumer line, bypassing the throttle point connected to the vent is due to the pressure equalization taking place due to the rapid venting when crossing the second threshold or other threshold, the main stage drain valve closes again.

to pure pressure control of the main stage inlet valve in normal operation This can be a two-sided pressurizable main stage piston have an upstream of the throttle point upstream air pressure associated first control surface and an air pressure downstream of the throttle point, smaller than the first control surface formed second control surface having a main stage piston indirectly or directly towards the first control surface acting spring element is provided such that the first threshold dependent from the quotient of the two control surfaces and the spring force of the Spring element is. The first threshold is then through The relationship the two control surfaces and predetermined by the spring force of the spring element or adjustable.

It is also advantageous if the main stage drain valve has a pressure control on both sides a pressurizable control piston, the one upstream of the throttle air pressure associated, a control pressure chamber limiting first control surface and the throttle body downstream associated, smaller than the first control surface formed second control surface, wherein the second threshold value is dependent on the quotient of the two control surfaces. On the interpretation of the geometry of the control surfaces, therefore, the second threshold value of the control pressure can be specified. If the pressure on the side upstream of the throttle point decreases by the second threshold value relative to the side downstream of the throttle point, the control piston is actuated due to the exceeding of the second threshold value, whereby air can flow out of the consumer line, bypassing the throttle point. Advantageously, the second threshold value is less than or equal to the product of the respective upstream air pressure with k-1, where k is the quotient of the larger control surface and the smaller control surface of the control piston; this means: p S2 ≤ p 1 (k - 1), where p _{1 is} the respective pressure prevailing in front of the throttle point air pressure.

In order to ensure that the main stage outlet valve remains closed even at maximum consumer pressure, it can be provided that the difference between the two control surfaces that are decisive for the control piston is smaller than or at least equal to the quotient of the spring force of the spring element and the maximum permissible consumer pressure. If the control surface associated with the upstream of the throttle point is denoted by F ₁ and the second control surface assigned to the throttle point is denoted by F ₂ , the spring force of the spring element by F _S and the maximum permissible consumer pressure are designated by p _max , the following preferably applies: F 1 - F 2 ≤ F S / p Max ,

at A further embodiment provides that the control piston and the main stage piston in a common cylinder space, the however, have different geometries and / or diameter can, are arranged axially one behind the other, wherein the control piston one between its two control surfaces forming the throttle point Breakthrough and wherein the main stage piston, the connection hollow with the consumer line is axially from the spring element acted upon against the control piston is arranged such that he crosses the main stage piston the first threshold against the spring force of the spring element from the normal position to the fast ventilation position. The for the Mainstay piston authoritative, the throttle point upstream control surface is in this embodiment formed by the throttle body upstream control surface of the control piston. Due to the axial movement of the control piston with pressure increase in the control pressure chamber over the first threshold will therefore be the main stage piston from the spool actuated, whereby the main stage inlet valve is opened.

Of the Main stage piston is preferably arranged such that he in the fast ventilation position a closed in the normal position, leading to the consumer and opens the throttle body immediate consumer line strand.

A Further advantageous embodiment results when the control piston falls below the second threshold in the control pressure chamber facing direction moves into the quick exhaust position, wherein a stop is provided which controls the movement of the main stage piston in the direction of the control pressure chamber out so limited that the control piston lifts off the main stage piston and compressed air between the spool and the main stage piston from the interior of the main stage piston, and thus from the consumer line, in a vent line flow out can. As already stated, Therefore, the second threshold is reached when the product the air pressure on the side downstream of the throttle and the associated control surface of the control piston higher is as the product of the air pressure upstream of the throttle point Page with the associated control surface of the control piston. Falling below the second threshold moves consequently the spool in the direction of the control pressure chamber. Because of the The main stage piston can stop the movement of the control plunger not follow its normal position in the quick exhaust position. By lifting the control piston from the main stage piston can consequently for quick exhaust Air out of the consumer line.

Especially is advantageous if the consumer line strand due to the Concerns the Hauptstufenkolbens on the stop is closed and when lifting the main stage piston from the stop is open. The stop thus has a double function; on the one hand he serves for axial movement limit of the main stage piston and the other to open or closing the the supply line to the consumer line connecting consumer line.

at Another advantageous embodiment is not only that Hauptstufeneinlass- and the main stage drain valve axially adjacent arranged, but also the inlet valve and drain valve. Preferably are all Valves in a common, one or more parts trained casing accommodated.

According to one advantageous embodiment is at least largely airtight Sealing between the control piston and the surface of the cylinder chamber at least one ring or membrane seal provided. Especially the provision of a membrane seal has the advantage that an effective Sealing is achievable, as the seal is firmly attached to the relative to each other moving parts is arranged.

Around a comparatively accurate pressure setting in the consumer line to enable is advantageous if the inlet valve and the drain valve of the Input stage are designed as pulsed controllable valves. Due to the pulsed control, the pressure in the consumer line can be gradual elevated or be lowered until the predetermined control air pressure is reached. The valves are preferably electromagnetic controllable, wherein the inlet valve in its rest position, ie with inactive control, closed and the drain valve open is. This ensures that in non-operation of the pneumatic control device the supply line is vented is.

Preferably the drain valve is also an electrically actuated pressure relief valve designed with the maximum allowable consumer line pressure is limited. This can be ensured that in the Consumer line not inadmissible high pressure occurs, which could lead to damage to the consumer.

An advantageous embodiment provides that at least the discharge valve of the input stage is designed as a controllable proportional to the required Ansteuerluftdruck valve. Preferably, such a drain valve is selected, on the one hand pulsed and proportional to the other. Proportional operation is required in emergency mode.

Further Details and advantageous embodiments of the invention are the following description, based on which the in The embodiments illustrated in the figures closer to the invention described and explained are.

It demonstrate:

1 a schematic representation of a pneumatic control device according to the invention;

2 a longitudinal section of a first embodiment of a pneumatic control device according to the invention in the normal position;

3 the device according to 2 in the fast ventilation position;

4 the device according to 3 in the quick exhaust position; and

5 a longitudinal section through a second pneumatic control device according to the invention.

Like in the 1 illustrated circuit diagram of a pneumatic control device 10 shows, includes the pneumatic control device 10 an input stage VS and one of the input stage downstream main stage HS. The input stage VS as such is provided by an inlet valve 12 and a drain valve 14 educated. The inlet valve 12 is connected to a compressed air supply P and supplies in the open state leading to a consumer A consumer line 16 , The drain valve 14 connects the consumer line when open 16 with a vent R.

In the consumer line 16 is a throttle point 18 provided, the front of the throttle 18 prevailing pressure in the consumer line with p ₁ and the throttle point 18 downstream pressure with p ₂ is called.

The main stage HS in turn comprises a main stage inlet valve 20 and a main stage drain valve 22 , Both valves 20 . 22 are purely pressure-controlled valves, which depend on one from the differential pressure between the throttle point 18 upstream air pressure p ₁ and the throttle point 18 downstream air pressure p ₂ control pressure p _S (p _S = p ₁ - p ₂ ) switch.

In the 1 is the pneumatic control device 10 shown in rest position, not only that of the throttle point 18 upstream consumer line string vented, but also the throttle point 18 downstream consumption ladder is vented.

The main stage inlet valve 20 , which is closed in its normal position, switches when its first normal value p _{S1 is} exceeded from its closed normal position to a rapid ventilation position in which the supply P bypasses the throttle point 18 with the throttle point 18 downstream section of consumer guidance 16 is connected. The first threshold value p _S1 is dependent in particular on the size of a first control surface F _{3 of} the valve 20 that of the throttle point 18 associated upstream air pressure p ₁ , the size of a second control surface F _{4 of} the valve 20 that of the throttle point 18 downstream air pressure p _{2 is} assigned, and the spring force Es a spring element 24 which is the main stage inlet valve 20 in its closed normal position urges.

This is parallel to the main stage inlet valve 20 switched main stage drain valve 22 , which is closed in its normal position, connects in its open quick exhaust position of the throttle point 18 downstream consumer management 16 with a vent R. The main stage drain valve 22 includes a consumers line air pressure p ₁ associated control surface F _1, and the consumer line pressure p ₂ associated control surface F _2, which is made smaller than the control surface F ₁ on. Due to the differently sized selected control surfaces F ₁ and F ₂ , a second threshold value p _{S2 of} the control pressure p _{S is} given, when it exceeds the main stage drain valve 22 closed or when it falls below the main stage drain valve 22 is opened.

The device 10 further includes one of the throttle point 18 downstream consumer line pressure p ₂ detecting pressure sensor 28 , which is the actual value of a control unit 30 telling. The control unit 30 then controls the function of the measured pressure p ₂ and depending on the control variable of the predetermined Ansteuerluftdrucks p _soll the inlet valve 12 and the drain valve 14 in such a way that, in the ideal case, the respective predetermined control air pressure p _soll prevails in order to control the consumer A.

With the device 10 Consequently, a supply line air pressure p _{2 which is} substantially constant and dependent on the predetermined control air pressure p _{soll can} be made available to the consumer even if the input pressure of the compressed air supply fluctuates greatly.

In normal operation, in which the respective actual air pressure p ₂ in the consumer line is known, is used to increase the pressure in the consumer line 16 the drain valve 14 closed and the intake valve in particular pulsed as long driven until the predetermined control air pressure p _{soll is reached} in the consumer line. To reduce the air pressure p ₂ in the consumer line 16 becomes the inlet valve 12 closed and the drain valve 14 in particular pulsed so driven until the respectively desired consumer line air pressure prevails. In this way, the consumer line air pressure p _{2 can be set} very precisely, in particular in the range of 0.1 bar.

Now occurs the case that, in particular due to the control input quantity p _soll, the pressure in the consumer line 16 should increase sharply, so increases the throttle point 18 upstream air pressure p ₁ due to a corresponding control of the input valve 12 opposite to the throttle point 18 downstream air pressure p ₂ strong.

When the threshold value p _{S1 is} exceeded, the inlet valve then switches 20 the main segment HS from the closed normal position to the fast ventilation position. Due to the bypass of the throttle point 18 finds a rapid pressure increase in the throttle point 18 downstream consumer management 16 instead of. The decrease in the pressure difference between p ₁ and p _{2 occurs} ; If the threshold value p _S1 falls below again, the main stage inlet valve switches 20 back to its normal closed position. A fine adjustment of the pressure p ₂ can then take place via the particular stepwise increase or decrease of the pressure p ₁ by means of the input stage VS.

As when ventilating the consumer line 16 the pressure p _{1 is} always greater than the pressure p ₂ , is the main stage drain valve 200 in its closed position. Even if the air pressure p _{1 is} slightly below the air pressure p ₂ , the main stage drain valve is 22 closed because the button f _{1 is made} larger than the button f ₂ .

If now the air pressure p _{2 is} to be lowered comparatively quickly on the basis of the predetermined control input value p _soll , then it drops due to the closed inlet valve 12 and the correspondingly long or frequent opening of the drain valve 14 the throttle point 18 upstream air pressure p ₁ strong. When the air pressure p ₁ drops below the second threshold value p _S2 , which is dependent on the quotient of the button F ₁ to the button F ₂ , the main-stage drain valve then switches 22 in the quick exhaust position, in the downstream of the throttle point consumer line 16 Air bypassing the throttle 18 can flow directly to the vent R. Due to the concomitant pressure equalization before the throttle and after the throttle point closes the drain valve 22 as soon as the second threshold value p _S2 is exceeded again. With the drain valve closed 22 and also closed inlet valve 20 can then via the throttle point 18 a fine control of the pressure p ₂ in the consumer line 16 by appropriate activation of the inlet valve 12 or the drain valve 14 be achieved.

With the described device 10 consequently, can be a very finely adjustable user line pressure p made available ₂ and, on the other still rapid ventilation or venting and thus a rapid pressure rise or pressure drop of the consumer line pressure p ₂ can be realized.

In order to prevent an inadmissible overpressure in the system leading to damage, in particular at the consumer A, the drain valve is 14 also designed as a pressure relief valve. The inlet valve 14 opens automatically when the maximum allowable load line pressure, which may be in particular in the range of 8 bar, is achieved.

In the 2 - 4 are different switching positions of a pneumatic control device 50 shown according to the in the 1 Scheme works.

The pneumatic control device 50 includes a housing 52 in which the input stage VS with the inlet valve 54 and axially next to the drain valve 56 is arranged. The inlet valve 54 and the drain valve 56 are each about magnets 59 separately controllable. To the inlet valve 54 leads a coming from a pressure supply P supply line 58 , That the inlet valve 54 facing free end 60 the supply line 58 forms a valve seat 74 who is in the in 2 shown position of an axially movable valve body 62 or from one into the valve body 62 recessed sealing element 64 is closed.

When controlling the magnet 59 of the inlet valve 54 thus becomes the valve body 60 against the spring force of a valve spring 66 so moved that he has the free end 60 the supply line 58 releases. When the inlet valve is open 54 can then the coming of the compressed air supply P compressed air via a connecting line 68 in a control pressure chamber 70 stream. The control pressure chamber 17 is also via the connection line 68 and over in the valve body 62 provided axial bores 72 via the drain valve 56 connected to the vent R The drain valve 56 is in principle the same as the inlet valve 54 , It also sees a valve body 60 with a sealing element 64 in front, that in the closed position against a valve seat 74 acts. Also the valve body 60 the drain valve 56 is spring loaded - but he will not, as in the intake valve 54 in the closed, but in the open position urged - and by the associated electromagnet 59 controllable. The valve body 60 the drain valve 54 also sees drilling in the axial direction 72 which, with the drain valve open, an axial connection 76 between the inlet valve 54 and the drain valve 56 with the vent R connects.

The spring elements 66 are at the inlet valve 54 and at the drain valve 56 mounted such that in a non-energized position of the valves, as shown in the 2 is shown, the inlet valve 54 is closed and the drain valve 56 is open. Consequently, in this position, air from the control pressure chamber 70 on the consumer line 68 , the axial bore 72 of the valve body 60 of the inlet valve 54 , the axial connection 76 , the valve seat 74 the drain valve 56 , the axial bores 72 the drain valve 56 and a vent line 78 towards the vent R.

On the inlet valve 54 opposite side of the connecting line 68 a main stage HS is provided, one in a cylinder chamber 80 slidably mounted, the control pressure chamber 70 limiting spool 82 a main stage drain valve 81 includes. The control piston 82 has a breakthrough in the axial direction 84 with a throttle point 86 forming bottleneck. On the control pressure chamber 70 opposite side of the control piston 82 is a likewise displaceably mounted in the axial direction main stage piston 88 a main stage intake valve 89 arranged. The main stage piston 88 is hollow and connects the interior 84 of the control piston 82 with a consumer line leading to consumer A. 99 , The main stage piston 88 gets from one to the case 52 supporting spring element 90 in the direction of the control piston 82 applied. In the in the 2 shown switching position is the control piston 82 facing end face 91 of the main stage piston 88 at one in the control piston 82 recessed sealing element 92 airtight, leaving no inside the control piston 82 or the main stage piston 88 existing air between the spool 82 and the main stage piston 88 can flow out radially outward.

The main stage piston 88 sees on his the control piston 82 opposite side a circumferential shoulder 94 before, at the a circumferential sealing element 96 is admitted. This sealing element 96 works in the in the 2 shown position due to the spring bias of the spring element 90 airtight against a housing-side stop 98 , As a result, a coming from the compressed air supply P, bypassing the throttle point 86 in the consumer line A leading consumer 99 opening consumer line 100 locked.

In the 2 is the main stage HS or are the two main-stage valve 81 and 89 in a closed normal position S ₁ , in which the consumer line pressure on the activation of the inlet valve 54 or the drain valve 56 is finely adjustable.

To increase the pressure of the consumer line pressure p ₂ , the inlet valve 54 with the drain valve closed 56 preferably driven pulsed. Due to the pulsation, the pressure p ₁ in the control pressure chamber 70 and the pressure p ₂ on the throttle point 86 downstream side of consumer guidance 99 be increased finely dosed. To reduce the pressure p ₂ in the consumer line 99 becomes the inlet valve 54 closed and the drain valve 56 controlled in particular so pulsed that the pressure drops finely dosed. The control piston 82 as well as the main stage piston 88 is located in the in the 2 shown closed normal position.

Now occurs the case that for controlling the consumer A in a short time, a high driving air pressure in the consumer line 99 is to be made available, then the inlet valve 54 with the drain valve closed 56 controlled such that in the control pressure chamber 70 the existing air pressure p ₁ rises sharply. Due to the throttle point 86 can on the downstream side of the throttle point of the air pressure p _{2 increase} only delayed. Upon reaching a first threshold value p _{S1 of} the air pressure difference between the throttle point 68 upstream air pressure p ₁ and the throttle point 86 downstream air pressure p ₂ is the control piston 82 including main stage piston 88 against the spring force F _{S of} the spring 90 in the axial direction such that the shoulder 94 or the sealing element 92 from the stop 98 takes off and the consumer line 100 is opened. The main stage inlet valve 81 Switches into the in the 3 shown quick ventilation position. Compressed air can then be supplied from the compressed air supply P via the consumer line 100 bypassing the throttle 86 directly into the consumer line 99 flow. This is a rapid pressure increase in the consumer line 99 connected.

The first threshold value p _{S1 of} the control pressure is in this case in particular via the spring force F _{S of} the spring element 90 and the one for the main stage piston 88 adjustable buttons adjustable. As the main stage piston 88 over the control piston 82 is moved into its open position, which is for the Main stage piston 88 the authoritative button facing the air pressure p _1, the button F _{1 of} the control piston 82 , The for the throttle point 86 downstream air pressure p ₂ relevant button of the main stage piston 88 is in the 2 denoted by F ₃ . The first threshold value p _S1 is consequently dependent on the quotient k = F ₁ / F ₃ and on the spring force F _{S of} the spring element 90 ,

Due to the opening of the main stage inlet valve 89 quickly finds a compressed air compensation between the throttle point 86 upstream pressure p ₁ and the throttle point 86 downstream pressure p ₂ instead. If the differential pressure falls _below the first threshold value p _S1 , the main stage inlet valve closes 89 it automatically and as described, a fine adjustment of the consumer line pressure p ₂ via the throttle point 86 respectively.

In the event that the supply line 99 should be vented quickly, the inlet valve 54 closed and the drain valve is controlled so that in the control pressure chamber 70 a strong pressure drop by opening the drain valve accordingly 56 takes place.

If the differential pressure p ₁ - p ₂ falls below the second threshold value p _S2 , then the control piston moves 82 in the axial direction to the inlet valve 54 ; the main stage drain valve 81 Switches into the open quick exhaust position as shown in 4 is shown.

The sealing element 92 lifts from the front 91 of the main stage piston 88 off, removing air from the consumer line 99 between the spool 82 and the main stage piston 88 radially outward in a vent line 102 , like in the 4 shown, can flow.

If the second threshold value p _S2 is exceeded again due to the pressure equalization taking place in the quick exhaust position, the main stage drain valve switches 81 back to its closed normal position. A fine adjustment of the consumer line pressure p ₂ can then via the input stage VS or the throttle point 86 respectively.

The second control pressure p _S2 results from the quotient of the control room 70 facing control surface F ₁ and the throttle point 86 remote, smaller control surface F _{2 of} the control piston 82 , wherein in particular: p _S2 ≦ p ₁ (F ₁ / F ₂ - 1).

How to 1 are explained in the embodiment according to the 2 - 4 the inlet valve 54 and the drain valve 56 depending on the in the consumer line 99 prevailing consumer line pressure p ₂ and depending on the controlled variable p _soll controlled. The consumer line pressure p ₂ is via a pressure sensor, as in the 1 with the reference number 28 is provided, measured. If the case arises that the respective current consumer line pressure should not be known, for example in the case of a defective pressure sensor, then the pneumatic control device can 50 switch to an emergency mode in which the intake valve 54 permanently open and the drain valve 56 proportional to the predetermined Ansteuerluftdruck, ie to p _soll , is controlled. The drain valve 56 is then operated as a proportional valve and no longer as in the normal operating mode as a pulsed valve.

To the pressure difference between the inlet side and the discharge side of the drain valve 56 However, it is provided that the inlet valve 54 is pulsed driven with a largely fixed drive frequency. As a result, the mean pressure in the connecting line 68 and in the axial connection 76 and thus the valve seat 74 the drain valve 56 lowered. For proportional operation of the drain valve 60 lower forces then suffice than with a permanently open inlet valve 54 , Overall, this allows a much more accurate adaptation of the respectively desired supply line pressure p ₂ can be achieved.

The drive frequency of the intake valve is advantageously chosen so that the discharge valve 56 occurring pressure fluctuations keep the valve body of the main stage drain valve in constant motion, whereby a friction in the valve is reduced.

The activation frequency of the intake valve is to be selected so that the resulting pressure fluctuations on the side of the consumer line upstream of the throttle point are so small that the first threshold value p _{1 is} not exceeded. This ensures that when providing a main stage described above, a lifting of the main stage piston from the stop does not occur and thereby the Verbraucherleitungsstrang remains closed. Overall, a comparatively accurate control of the control air pressure can thereby be achieved in an air-saving manner.

The in the 5 shown further embodiment of a pneumatic control device according to the invention 110 corresponds in the functioning of the device 50 according to the 3 - 4 , wherein corresponding components are provided with corresponding reference numerals.

Substantial difference of the device 110 opposite the institution 50 is that the one direction 110 a membrane seal 112 between the spool 82 and the housing 52 as well as between the main stage piston 88 and the housing 52 has, whereby an air outlet between the control piston 82 or the main stage piston 88 and the housing 52 effectively prevented.

The inlet valve 54 sees in the embodiment according to 5 an additional spring element 114 before, with the hitting the sealing element 64 against the valve seat 74 resulting pressure surges are cushioned.

Claims (9)

Method for operating a pneumatic control device ( 10 . 50 . 110 ) for providing a predeterminable control air pressure (p _soll ) in a consumer line leading to a consumer (A) ( 16 . 99 ), with an input stage (VS), which is connected to a supply line (P, 58 ) connectable inlet valve ( 12 . 54 ) for ventilation of the consumer line ( 16 ) and between the consumer line ( 16 ) and a vent (R) provided drain valve ( 14 . 56 ), wherein the inlet valve ( 12 . 54 ) is pulsed with a predetermined drive frequency and the drain valve ( 14 . 56 ) proportional to the predetermined control air pressure (p _soll ) is controlled. A method according to claim 1, characterized in that the driving frequency of the inlet valve ( 12 . 54 ) is selected so that the drain valve ( 14 . 56 ) occurring pressure fluctuations the valve body of the drain valve ( 14 . 56 ) at least largely keep in constant motion. Method according to one of claims 1 or 2, characterized in that the method only in an emergency operation of the pneumatic control device ( 10 . 50 . 110 ), in which the actual actual consumer line pressure (p ₂ ) is unknown, is used and that in a normal operation of the pneumatic control device ( 10 . 50 . 110 ), in which the respective actual consumer line pressure (p ₂ ) is known, in dependence on the respective predetermined control air pressure (p _soll ) and on the respective consumer line pressure (p ₂ ) the inlet valve ( 12 . 54 ) for increasing the pressure with the drain valve closed ( 14 . 56 ) is driven. A method according to claim 3, characterized in that the input stage (VS) is followed by a main stage (HS), which in the normal operation of the pneumatic control device ( 10 . 50 . 110 ) when a first threshold value (p _S1 ) of a control pressure in a fast ventilation position and / or falls below a second threshold value (p _S2 ) of the control pressure in a quick exhaust position, wherein in emergency operation, the drive frequency of the intake valve ( 12 . 54 ) is chosen in such a way that those in the consumer 16 . 99 ) are so small that the first threshold (p _S1 ) is not exceeded and / or the second threshold (p _S2 ) is not exceeded. A method according to claim 4, characterized in that the control pressure (p _s ) from the difference between the one in the consumer line ( 16 . 99 ) provided throttle point ( 18 . 86 ) upstream air pressure (p ₁ ) and the throttle point ( 18 . 86 ) downstream air pressure (p ₂ ) is formed. A method according to claim 4 or 5, characterized in that in normal operation for rapid ventilation when the first threshold value (p _S1 ) is exceeded, a main stage inlet valve ( 20 . 80 ), whereby the supply line (P, 58 ) bypassing the restriction ( 18 . 86 ) with the consumer 16 . 99 ), wherein due to the taking place by the rapid venting pressure equalization falls below the first threshold (p _S1 ) or another threshold, the main stage inlet valve ( 20 . 89 ) closes again, and / or that in normal operation for quick exhaust when falling below the second threshold (p _S2 ), a main stage drain valve ( 22 . 81 ), causing the consumer line ( 16 . 99 ) bypassing the restriction ( 18 . 86 ) is connected to the vent (R), wherein due to the taking place by the quick vent pressure equalization at the second threshold (p _S2 ) or another threshold, the main stage drain valve ( 22 . 81 ) closes again. A pneumatic control device which carries out or carries out the method according to at least one of claims 1 or 2 ( 10 . 50 . 110 ), with an input stage (VS), which is connected to a supply line (P, 58 ) connectable inlet valve ( 12 . 54 ) for ventilation of the consumer line ( 16 ) and between the consumer line ( 16 ) and a vent (R) lying drain valve ( 14 . 56 ) for venting the consumer line ( 16 ) and with an electronic control unit ( 30 ) for controlling the inlet valve ( 12 . 54 ) and the exhaust valve. A method implementing the method according to claim 3 or intended for the implementation of pneumatic control device ( 10 . 50 . 110 ) according to claim 8, comprising a pressure sensor for determining the consumer line pressure (p ₂ ), wherein in normal operation the inlet valve ( 12 . 54 ) and the drain valve ( 14 . 56 ) as a function of the consumer line pressure (p ₂ ) from the control unit ( 30 ). A method according to claim 4, 5 or 6 carrying out or intended to carry out pneumatic control device ( 10 . 50 . 110 ) according to claim 9, comprising a main stage (HS) arranged downstream of the input stage (VS) with a main stage inlet valve (HS). 20 . 80 ) and a main stage drain valve ( 22 . 81 ), which are designed such that they switch in normal operation of the pneumatic control device when the first control pressure (p _S1 ) in a fast ventilation position and / or falls below the second control pressure (p _S2 ) in a quick exhaust position.