DE4238790A1 - Air suspension unit - Google Patents

Description

The invention relates to an air suspension unit with a Spring strokes changing their main chamber volume, e.g. B. air bellows used to change the progressiveness of the spring Forces of the air suspension unit with a one essentially constant volume additional chamber via a valve connectable or lockable against this chamber.

Air suspension units are used on motor vehicles, in particular also used on trucks, when a special one high comfort can be guaranteed and if necessary above In addition, the ground clearance of the Vehicle adapted to different operating conditions to change. Changing the ground clearance is more common shows that additional air in the air suspension unit introduced or air is discharged from the spring assembly. The air supply or discharge is usually also used to change the progressivity of the spring forces, by, for example, strong air deflection strokes pressure in the spring assembly increased and excessive rebound is lowered.

However, it must be accepted that when driving operation requires a lot of energy.  

In order to keep this energy expenditure as low as possible, it is generally known in the above For example, a head that changes its volume during spring strokes Chamber of the air suspension unit with a one essentially to combine constant volume having additional chamber and the connection of both chambers by means of a valve Taxes. The addition that can be locked off from the main chamber chamber offers the possibility of the spring-effective air volume to change. If the said valve between the main and Additional chamber assumes its open end position large total volume available, which is at Fede the stroke of the air suspension unit changes relatively little, because the volume change compared to the size of the total volume has only a relatively small dimension. This means that the air pressure with the valve open during the spring tion strokes changes only moderately and the air suspension unit a spring detection with relatively low progressivity points. This makes driving particularly comfortable possible. If necessary - for example if a jounce stroke exceeds a predetermined threshold - can the Additional chamber quickly blocked off from the main chamber so that only the air volume in the main chamber becomes effective. This is equivalent to the fact that Ratio between the Ver occurring in suspension strokes changes in the spring-effective air volume and the total volume in the main chamber reached a relatively large value and the air suspension unit accordingly with clearly ver works more progressively, d. H. with increasing on suspension stroke becomes a significantly increasing support force of the spring assembly reached.  

In addition, the spring detection when closed Valve comparatively lower due to supply and discharge Air volumes in and out of the main chamber comparatively be greatly changed. Corresponding air suspension units are, for example, in the following publications described: JP-A 61-180034, DE-A 40 18 712, DE-A 34 44 577, DE-B 10 81 780, DE-B 11 44 127, DE-A 15 30 632 and EP-A 01 66 702.

According to the last-mentioned document, the valve either as a simple changeover valve or as a controllable one Throttle valve to be formed. In the former case is only a comparatively quick switch between the full constantly open and completely closed possible. In the latter case, the air flow rate of the Control valves.

With a throttled open position of the valve however, take into account that the influence of the auxiliary chamber on the progressiveness of the feather detection can, because the suspension strokes in the main chamber occurring dynamic pressure changes practically not can reproduce more on the additional chamber. Much more the additional chamber becomes dynamic from the main chamber throttled connection "decoupled".

An air spring unit is known from US-A 48 44 428, in which a main and an additional chamber constantly over a throttled line are connected and between the  a displaceable piston is arranged in both chambers, the adjustment of which increases the volume one chamber and at the same time a reduction of the Volume of the other chamber causes. That way too can change the progressiveness of the spring reach identifier.

The object of the invention is now the operating behavior an air suspension unit of the type specified at the outset to improve significantly.

This object is achieved in that the valve between the main and auxiliary chamber in its open end position a practically throttle-free connection with a large flow cross-section between main and additional chamber produces, from its open position relatively quickly is switchable to its closed position, but when opening works with delay by first delaying it a pressure equalization between the main and additional chamber a pre-opening phase that allows only low currents goes through.

The invention is based on the general idea between Main and additional chamber a valve with asymmetrical operation order to behave in order to quickly close and on the other hand to allow delayed opening. By quick closing of the valve between main and additional If necessary, the suspension can be chambered without noteworthy Performance harden bumplessly, because on the one hand spring-acting air volume changes quickly and on the other hand  no pressure simply from the closing movement of the valve Change occurs in the main chamber.

The delayed opening of the valve takes into account that with the valve closed between the main and auxiliary chamber - Depending on the suspension stroke - relatively large pressure differences can occur when the throttle-free opening of the Valves can cause sudden forces. By now the invention provides that the valve when opening first goes through a pre-opening phase in which only minor Currents are made possible, d. H. between main and Additional chamber only a relatively severely throttled connection is present, even under unfavorable conditions adequate adjustment of the pressures in the main and additional chamber ensured before the two chambers again throttle-free are interconnected.

According to a preferred embodiment of the invention the valve in the pre-opening phase for pulsed opening can be controlled before the fully open end position for is set for a long time.

It is also advantageous if the valve as a seat valve is designed such that the sealing surfaces on the valve seat and on the valve body in the opening or closing direction of the valve overlap relatively far in the closed state, whereby the overlap area should be shaped so that when Opening stroke of the valve is initially only a throttle gap opens.  

It can also be conveniently provided that Control of the valve fluidically, in particular pneumatically, to make, in such a way that to control the valve a fluidic displacement unit is used, which for Opening the valve with fluid pressure or to Closing the valve is relieved of the fluid pressure, the pressure being applied via a throttled and the pressure relief takes place via an unthrottled line. In this way the opening stroke of the valve is slowed down. Nevertheless, quick closing remains possible.

Otherwise, the preferred features of the Invention on the claims and the following explanations tion of advantageous embodiments referenced are shown in the drawing.

It shows

Fig. 1 is a schematic sectional view of a contemporary air spring assembly Invention,

Fig. 2 is a schematic sectional view of a pneumatically controlled valve for the connection between the main and auxiliary chamber,

Fig. 3 is a sectional view of the sealing surfaces of the seat and valve body of the aforementioned valve and

Fig. 4 is a circuit diagram representation of the control of the aforementioned valve.

FIG. 1 is disposed between a sprung mass 1, which is formed in a vehicle by the vehicle body and an unsprung mass 2, which tool, in the case of a driving wheel or by u Achsführungselemente. Like. Is formed, an air suspension unit 3 is arranged, which consists essentially in a generally known manner of a bellows 4 arranged on the sprung mass 1 and a rolling piston 5 which can be inserted therein and which is arranged on the unsprung mass 2 .

In suspension strokes, the volume of the bellows 4 changes , so that the air pressure in the bellows 4 increases during deflection strokes and decreases during rebound strokes.

Compressed air from a pressure source, not shown, for example from a compressor, can be introduced into the bellows 4 or discharged to the outside via a control valve (not shown). In this way, an additional pressure increase or pressure reduction in the bellows 4 can be achieved.

The interior of the bellows 4 forms a volume-variable main chamber of the spring assembly 3 and can be connected via a valve 6 , which releases a large flow cross section when fully open, with an additional chamber 7 , which has a substantially constant volume and in cavities of the rolling piston 5 or communicating cavities of unsprung mass 2 .

A further additional chamber 9 can optionally be connected by means of a further valve 8 of the same type.

If both valves 6 and 8 are open, a large spring-effective air volume is available, the total volume being changed relatively little during suspension strokes. Accordingly, the pressure changes caused by the suspension strokes of the pressure in the bellows 4 and in the additional chambers 7 and 9 trapped air are relatively low, ie the air suspension unit 3 works with low progressivity. Depending on whether only the valve 8 or the valve 6 is closed, the spring-effective air volume can be reduced to a greater or lesser extent, with the result that the changes in the spring-effective air volume caused by Fede strokes are correspondingly large compared to the total spring-effective air volume and the air suspension unit works with greater progressiveness.

In Fig. 2 the valve 6 is now shown schematically.

Referring to FIG. 2, the valve 6 controls an opening 10 with a large cross-section in a wall between the interior space F of the spring bellows 4 and the inner space K of the rolling piston 5 underweight body part attached to the auxiliary chamber 7.

For this purpose, the valve 6 has a plate-shaped valve body 11 which, in the closed state shown, rests on a valve seat 12 arranged at the edge of the opening 10 .

By means of a slidably guided in a guide 13 rod 14 of the valve body 11 is connected to a plate-like piston which is slidably guided in a respective cylinder and on its side facing the valve body 11 side by the pressure p _K in the auxiliary chamber 7 and at its from the valve body 11 opposite side is acted upon by a control pressure p _S in a control chamber 17 .

The effective area of the piston 15 facing the valve body 11 is larger than the end face of the valve body 11 facing the piston 15 , which in the closed state of the Ven tiles 6 is acted upon by the pressure p _K in the additional chamber. Thus, the pressure p _K always causes a force in the closing direction of the valve body 11 .

The other side of the valve body 11 is acted upon by the pressure p _F in the interior of the bellows 4 . This pressure p _F is practically the same as the pressure p _K when the valve 6 is fully open.

If the control pressure p _S in the control chamber 17 has a sufficiently large value, piston 15 and valve body 11 are raised from the position shown in FIG. 2, so that the valve 6 opens. If the pressure in the control chamber 17 falls below the pressure p _K in the additional chamber 7 or the pressure p _F in the bellows 4 by a sufficient amount, the valve 6 closes.

The control circuit shown in FIG. 4 serves to control the pressure in the control chamber 17 . Depending on the switching position of a switching valve 18 , the control chamber 17 is connected to a pneumatic pressure source or a compressor 19 or - as shown in Fig. 4 - with an air outlet 20 . Between the switching valve 18 and the control chamber 17 , a throttle 21 and a check valve 22 are arranged parallel to one another, which is opened by the pressure in the control chamber 17 as soon as the switching valve 18 is brought into the position shown. The control chamber 17 can thus be relieved of the pneumatic pressure practically without throttling as soon as the changeover valve 18 is brought into the position shown. If, on the other hand, the changeover valve 18 is switched to its other position, the check valve 22 closes, and the compressed air from the pressure source 19 can only flow into the control chamber 17 via the throttle 21 . Accordingly, the pressure build-up in the control chamber 17 is delayed.

Accordingly, it is achieved with the arrangement shown in Fig. 4 that the valve 6 opens relatively slowly when switching the Umschaltven tiles 18 in its position, not shown, but can quickly close when switching the switching valve 18 in the position shown.

In this way, on the one hand a quick closing and on the other hand a delayed opening of the valve 6 is achieved with a pre-opening phase, in which only a possibly small opening cross section is released by the valve body 11 , so that initially only a throttled connection between the additional chamber 7 and the main chamber 4 is released and a slow pressure equalization between these two chambers is made possible.

The control of the changeover valve 18 is constantly checked for correct function. If a malfunction is found, the changeover valve 18 is disconnected from its energy supply, for example an electrical power source, so that it is inevitably brought into the position shown by a return spring or the like, in which the control chamber 17 remains practically depressurized. Thus the valve 6 inevitably assumes its closed position, so that in such cases only the air volume in the bellows 4 is spring-effective and the spring assembly 3 operates with a correspondingly high degree of progressiveness. This ensures safe operation of the air suspension unit 3 in any case - even if with reduced comfort.

Referring to FIG. 3, the valve body 11 and the valve seat 12 of the valve 6 may have each other in the closed position of this valve 6 axially overlapping sealing rings 23 and 24 which are formed such that at incipient opening stroke of the valve body 11 initially only a very narrow gap with a pronounced Throttle effect is opened. In this way it is ensured that only a delayed pressure equalization between the interior spaces F and K is made possible when the valve 6 is opened.

In the example shown in FIG. 3, the sealing ring 23 , which is arranged as part of the valve seat 12 , is designed as a metal ring which is screwed to a support part. The sealing ring 24 on the valve body 11 consists of an elastomer material and is inserted into a groove in the valve body 11 . An annular disk 25 and a locking ring 26 serve to hold or fix the sealing ring 24 . In order to avoid that the sealing ring 24 traps air inside the groove in the valve body 11 , which could then prevent the sealing ring 24 from seating correctly in the groove, several small bores 27 are arranged in the valve body 11 for venting the said groove .

Claims (5)

1. Air suspension unit with a main chamber (F) changing its volume during spring strokes, e.g. B. air bellows, the spring unit to change the progressiveness of the spring forces of the air with a substantially constant volume having additional chamber (K) via a valve ( 6 ) connectable or lockable with respect to this chamber, characterized in that the valve in its open end position creates a practically throttle-free connection ( 10 ) with a large flow cross-section between the main and additional chamber (F, K), can be switched from its open position to its closed position relatively quickly, but works with a delay when opening by first delaying pressure equalization between the main - and the additional chamber (F, K) passes through a pre-opening phase that allows only low flows. 2. Air suspension unit according to claim 1, characterized, that the valve 6 can be actuated for pulsed opening. 3. Air suspension unit according to one of claims 1 or 2, characterized in that the valve ( 6 ) is designed as a seat valve and on the seat ( 12 ) and on the valve body ( 11 ) closely overlapping sealing surfaces or sealing rings ( 23 , 24 ) are arranged which initially only release one throttle gap when the opening stroke begins. 4. Air suspension unit according to one of claims 1 to 3, characterized in that for actuating the valve ( 6 ), a pneumatic control is arranged by means of pneumatic displacer, which is acted upon by pneumatic pressure for opening the valve ( 6 ) and relieved of the pneumatic pressure for closing is, the pressure being applied via a throttled and the pressure relief via an unthrottled line ( 21 , 22 ). 5. Air spring unit according to one of claims 1 to 4, characterized in that the additional chamber (K) in the piston ( 5 ) of an air spring bellows ( 4 ) or in the piston connectable or communicating cavities is arranged.