DE102007056684B4 - accumulator - Google Patents

Abstract

Pressure accumulator (2) having a housing (9), a displaceable element (8) arranged within the housing (9) and a force accumulator (23),
Wherein the displaceable element (8) has a first pressure surface (10),
• wherein the first pressure surface (10) and the housing (9) at least partially limit a storage space (12) and
• wherein the displaceable element (8) can be displaced by pressure medium loading of the storage space (12) against the force of the force accumulator (23), characterized in that
The displaceable element (8) has a second pressure surface (11),
Wherein the second pressure surface (11) and the housing (9) at least partially delimit a control space (13),
• wherein the displaceable element (8) by pressurizing the control chamber (13) also against the force of the force accumulator (23) can be moved and
• wherein the pressure accumulator (2) is designed such that a pressure medium flow within the pressure accumulator (2) between the control chamber (13) and the reservoir (12) is locked at least in the direction of the control chamber (13) or can be locked.

Description

Field of the invention

The invention relates to a pressure accumulator having a housing, a displaceable element disposed within the housing and a force accumulator, wherein the displaceable element has a first pressure surfaces, the first pressure surface and the housing at least partially delimit a reservoir and wherein the displaceable element by pressurizing the Vorratsraums can be moved against the force of the energy storage.

Background of the invention

Accumulators are used in a variety of applications to take during operation of the application pressure medium, which is supplied by a pressure source, such as a pressure medium pump, and to provide this when needed the application again. Conceivable applications in vehicle technology are, for example, automated transmissions, automatic transmissions, hydraulically actuated, shiftable valve train components (rocker arms, support elements, cup or roller tappets), camshaft adjusters, brake systems or the like.

Such an accumulator is for example from the DE 42 02 905 A1 known. The accumulator has a formed in a housing made of aluminum, blunt-ended cylinder bore. In the cylinder bore a longitudinally movable pressure piston is added. This separates a pressure medium receiving, variable volume reservoir, which is formed within the housing, from a breathing chamber in communication with the atmosphere. In the reservoir opens a connection hole through which pressure medium can be moved. The breathing chamber is closed by a cap inserted into the cylinder bore. In the housing, a helical compression spring is also included. This engages in the pressure piston and is supported with bias on the one hand at the bottom of the pressure piston and on the other hand indirectly via the closure cap on the housing. The compression spring supports the delivery of pressure medium received in the storage space and returns the pressure piston to the initial position in which the storage space has a minimal volume. If the force acting on the pressure piston and resulting from the pressure prevailing in the hydraulic system, greater than the counteracting force of the compression spring, so the pressure accumulator fills. In this case, the pressure piston is displaced within the housing against the force of the compression spring, whereby the volume of the reservoir increases. If the pressure in the hydraulic system decreases, the pressure piston is displaced by the compression spring in the direction of the starting position until the opposing forces acting on the pressure piston are balanced. As a result, the pressure medium stored in the reservoir is returned to the hydraulic system. In this case, the pressure provided by the pressure accumulator at the beginning of its emptying corresponds to the pressure which prevailed directly before the start of emptying in the hydraulic system. A disadvantage of this embodiment is that the pressure support of the application, which is associated with the pressure accumulator, can not take place beyond the pressure value, which has prevailed directly before the start of the pressure support in the hydraulic system. In order to ensure the functional safety of the application, the pressure medium pump, which is assigned to the hydraulic system, must be designed for the peak requirements of the applications. Especially in applications in which no approximately constant load prevails, but short-term demand peaks, the pressure medium pump must be designed for this, whereby the pressure medium pump is oversized for the vast majority of the operation. It would also be conceivable to use a controllable pressure medium pump, which promotes pressure medium according to the current needs of the application or provides the required system pressure. Both solutions increase the cost of the application and require more space. At the same time due to the larger design of the pressure medium pump, the efficiency of the application.

The DE 40 32 875 A1 shows a hydraulic accumulator for a hydraulic system, in particular brake system, with a accumulator piston which defines a storage space with a front side, a vacuum piston which defines an atmospheric space with its one end face (pressure side) and with its other end face (negative pressure side) defines a vacuum space, wherein Vacuum piston and accumulator piston are connected to each other such that during a displacement of the vacuum plunger in the sense of reducing the atmosphere space of the accumulator piston is moved so that the storage space is increased, the atmosphere space is connected via a port constantly connected to the atmosphere, and that the vacuum chamber so is sealed, that no air intake is possible.

The DE 38 29 646 A1 shows reservoir for a pressure medium circuit with a first and a second working piston, which seal a first pressure chamber and second pressure chamber, wherein the effective area of the first piston is significantly smaller than the second pressure chamber relative to a second effective area of the second piston and in the first pressure chamber ruling first pressure is much higher than the second pressure in the second pressure chamber and wherein the first piston is connected to the second piston via a piston rod, wherein the piston rod consists of at least two telescopically displaceable part rods.

Object of the invention

The invention has for its object to provide a pressure accumulator, which eliminates the aforementioned disadvantages, with a reliable operation of the application is to be ensured in each phase of operation. It should also be possible to dispense with an oversizing of the pressure medium pump (design to the expected peak loads), as well as the use of variable pressure medium pumps.

The object is achieved in a pressure accumulator according to the preamble of claim 1 according to the invention, that the displaceable element has a second pressure surface, wherein the second pressure surface and the housing limit a control space at least partially, wherein the displaceable element by pressurizing the control chamber also against the force of Force accumulator can be moved and wherein the pressure accumulator is designed such that a pressure medium flow is locked within the pressure accumulator between the control room and the storage space at least in the direction of the control room or can be locked.

It can be provided that the storage room communicates with a consumer. Alternatively it can be provided that the storage space can be connected to a consumer. In one embodiment of the invention, the control chamber can be connected without pressure to a tank. It can be provided that the storage space does not communicate with the tank at the same time. Likewise conceivable are embodiments in which the control room can be emptied independently of the storage space. Advantageously, the control room can be selectively connected to a pressure source or a tank during operation of the application. In this case, control means may be provided, wherein the control chamber can be selectively connected by means of the control means with a tank or a pressure source. In a concretization of the invention it is provided that a pressure medium loading of the storage space displaces the displaceable element in the same direction as a pressurizing of the control chamber. Furthermore, it can be provided that the storage space is at least connectable to a consumer, the control space can be connected to a tank and the ratio between the minimum flow cross section between the control space and the tank and the minimum flow cross section between the storage space and the consumer is greater than the ratio between the surface area of the second printing surface and the surface area of the first printing surface. In one embodiment of the pressure accumulator is provided that within the pressure accumulator no connection between the reservoir and the control room exists, d. H. the storage room and the control room within the pressure accumulator do not communicate with each other. The displaceable element may be formed, for example, as a pressure piston which can be displaced within a housing against the force of a force accumulator designed as a spring element. Alternatively, other forms of energy storage can be used, for example, reversibly deformable body, for example made of elastomers, or gas-filled bubbles. Due to the design of the pressure accumulator with a displaceable element, which partially isolated spaces within the pressure accumulator, these two spaces can be controlled separately, d. H. filled and / or emptied. Apart from any leakage occurring there is no connection between the rooms. For example, different pressure sources for filling the storage space and the control room can be used. Alternatively, a pressure medium connection between the reservoir and the control chamber can be provided within the pressure accumulator. Pressure medium which is supplied to the control room, can get over this pressure medium connection in the storage room. However, it must be ensured that a reverse flow of pressure medium is prevented from the storage space into the control space. This can be realized for example via a pressure medium channel in the pressure piston or the housing of the pressure accumulator, in which a check valve is arranged. In this case, the filling of the storage space and the control room can be done solely by the filling of the control room. If the accumulator is emptied, the control room is switched to tank. The storage room empties into the hydraulic system, the control room depressurized into the tank. A transfer of pressure medium from the reservoir into the control chamber is prevented by the check valve.

If it is provided that a pressurization of the storage space displaces the displaceable element in the same direction as a pressurizing of the control space, the control space can support the filling of the storage space. For this purpose, the control chamber is also filled with pressure medium during the filling process of the storage space. As a result, a force acts on both pressure surfaces of the pressure piston, whereby a higher force is stored in the energy store (the spring element is compressed more strongly). If the filled pressure accumulator receives the command to support the application assigned to the pressure accumulator, then the control space can be independent be emptied from the storage room. That is, while the reservoir is being drained into the application's hydraulic system, thereby assisting the hydraulic system, the control chamber may be vented against atmospheric pressure into a tank. The tank may be the pressure medium reservoir of the application or another buffer. By suitable design, the venting of the control chamber can be done faster than the emptying of the reservoir into the hydraulic system. Thus, the entire force that was stored in the energy storage acts on the first pressure surface on the pantry. As a result, the pressure at the beginning of the assist process can be reduced by up to a factor of A₁ + A₂ / A₁ increase, depending on the load that acts on the energy storage at this time. Here A ₁ corresponds to the surface area of the first pressure surface and A ₂ corresponds to the surface area of the second pressure surface. If, for example, a spring element is used as the force store, the pressure at the start of the assistance process increases by the full factor A₁ + A₂ / A₁ as long as the spring has not yet reached its maximum compressed state. The maximum compressed state may be defined, for example, by one or more stops within the housing or the maximum compression travel of the spring.

The invention is based on the fact that a displaceable element of the pressure accumulator delimits at least two separate spaces which can be acted upon by pressure medium in the direction of displacement of the element. At least one of the rooms (storage room) is connected or connectable to the hydraulic system of the application. Furthermore, at least one additional space (control chamber) is also subjected to pressure medium during the filling process of the storage space and emptied faster than this during the emptying process of the storage space. This can be done, for example, against atmospheric pressure, in a tank. Thus, the control chamber supports the filling process such that the displaceable element is deflected more than would be the case without pressurizing the control chamber.

By increasing the pressure provided by the pressure accumulator, the pressure accumulator can intercept peak consumption, so that the pressure medium pump can be designed for the normal operation of the application. There are no oversized or regulated pressure medium pumps needed to ensure a reliable and fast response to the pressure medium requirement of the application.

As a pressure source, which acts on the control chamber with pressure medium, for example, the hydraulic system or its pressure medium pump or a separate source, for example, serve a separate pressure medium pump. In the second case, the pressure accumulator can be completely filled even in operating phases with low system pressure. The selective connection to a pressure source or the tank is established via control means, for example a 3/2-way valve in the form of a switching valve (for example a seat valve) or a proportional valve (for example a slide valve). Alternatively, two control means come into consideration, one of the control means the connection pressure source -> control room and the other control means the connection control room -> tank locks or releases. The control means may be, for example, electromagnetically actuated hydraulic valves, such as directional control valves (for example switching or proportional valves), pilot operated check valves or the like. These control means receive from a controller of the application control signals according to which the pressure accumulator is filled or emptied. Thus, a variety of support strategies can be realized.

Advantageously, a check valve can be provided in the hydraulic system between the control chamber and the pressure source, which blocks a pressure medium flow from the control chamber in the direction of the pressure source. Thus, the pressure medium volume located in the control chamber is trapped until it is connected to a tank. As a result, the displaceable element is held in the deflected position, even if the system pressure drops and thus prevents unwanted emptying of the storage space.

The pressure support of the pressure accumulator can be activated by simply switching one or more control means. In this case, the pressure medium volume is provided, which is stored in the operating phases of the application with low pressure medium consumption in the storage space. Depending on the embodiment, the pressure maintained by the pressure accumulator either corresponds to the current system pressure multiplied by a factor which can amount to 1 + A ₂ / A ₁ (embodiment without check valve) or a maximum system pressure present during the filling phase multiplied by the same factor (embodiment with check valve). The full factor 1 + A ₂ / A ₁ is always present when the full storage capacity of the energy storage has not been exhausted, for example. The spring element is not yet compressed to block or the displaceable element is still applied to the attacks.

In a development of the invention, it is provided that the displaceable element has a third pressure surface which at least partially delimits a counter-pressure space, wherein a pressurization of the counterpressure space displaces the displaceable element in the opposite direction displaced, such as a pressurizing of the control room or the storage room. Thus, the force exerted on the displaceable element by the force accumulator is increased by the force caused by the pressure in the counterpressure chamber.

Brief description of the drawings

Further features of the invention will become apparent from the following description and from the drawings in which embodiments of the invention are shown in simplified form. Show it:

1 a hydraulic system containing a first embodiment of a pressure accumulator according to the invention,

2 A second embodiment of a pressure accumulator according to the invention,

3 a further hydraulic system containing a further embodiment of a pressure accumulator according to the invention.

Detailed description of the drawings

1 shows a hydraulic system 1 a first embodiment of a pressure accumulator according to the invention 2 assigned. The hydraulic system 1 has a consumer 3 on, from a pressure source, which in the illustrated embodiment as a pressure medium pump 7 is executed, via a pressure medium line 4 can be acted upon with pressure medium. To a backflow of pressure medium from the consumer 3 to the pressure medium pump 7 To prevent it is a check valve 5a in the pressure medium line 4 provided, which a pressure medium flow from the pressure medium pump 7 to the consumer 3 allows, but blocks an opposite pressure medium flow. There is also a tank 6 provided, from which the pressure medium pump 7 Supplied pressure medium and in the pressure medium from the consumer 3 can be dissipated. The hydraulic system 1 is a pressure accumulator 2 assigned to the one as a pressure piston 8th executed displaceable element comprising a housing and a power storage. The pressure piston 8th is inside the case 9 arranged and can be moved against the force of a force accumulator. In the illustrated embodiment, the energy accumulator is a spring element 23 executed. However, other types of energy stores are also conceivable, for example suitably shaped elastomer bodies or gas-filled bubbles. The pressure piston 8th has two pressure surfaces 10 . 11 on. Together with the case 9 limits the first pressure area 10 a pantry 12 , wherein the first pressure surface 10 the pantry 12 in the direction of displacement of the pressure piston 8th limited. The housing 9 and the plunger 8th limit a control room 13 , wherein the second pressure surface 11 the control room 13 also in the direction of displacement of the pressure piston 8th limited. Here are the pressure piston 8th and the case 9 designed such that within the pressure accumulator 2 no connection between the two rooms 12 and 13 consists. Apart from leakage, there is no pressure medium exchange between these pressure chambers in this embodiment 12 . 13 instead of. In the illustrated embodiment, the pressure surfaces 10 . 11 in the direction of displacement of the pressure piston 8th arranged offset to one another, wherein the first pressure surface 10 in the plane, that of the direction of displacement of the pressure piston 8th is pierced vertically, from the second pressure surface 11 is enclosed. The first printing surface 10 is circular and the second pressure surface 11 ring-shaped. By pressurizing the rooms 12 . 13 becomes the pressure piston 8th against the force of the spring element 23 shifts, reducing the volume of the rooms 12 . 13 increases. The way the pressure piston 8th against the spring element 23 is displaced by stops 14 limited within the housing 9 are formed. The attacks 14 are arranged such that a connection of the storage space 12 with the control room 13 is prevented.

The spring element 23 relies on the one hand at the pressure chambers 12 . 13 opposite side of the pressure piston 8th and on the other hand at the pressure chambers 12 . 13 opposite side of the housing 9 from. In this case, the spring element with bias in the accumulator 2 mounted so that the volume of the pressure chambers 12 . 13 is minimal at low system pressure. In this initial position, the pressure piston is located 8th on whose the spring element 23 opposite side to the housing 9 at.

Between the pantry 12 and the hydraulic system 1 is stock management 15 intended. The supply line 15 opens on the one hand downstream of the check valve 5a in the hydraulic system 1 and on the other hand via a first pressure medium connection 24 in the pantry 12 , The control room 13 can optionally with a tank 6 or by means of a control line 16 be connected to a pressure source. In the illustrated embodiment serves as a pressure source, the pressure medium pump 7 of the hydraulic system 1 , The control line 16 opens on the one hand upstream of the check valve 5a in the pressure medium line 4 and on the other hand via a second pressure medium connection 25 in the control room 13 , Also conceivable are embodiments in which a different pressure source, for example a separate pressure medium pump is used.

To the pressure medium flow to and from the control room 13 to control is a control means 17 in the form of a directional valve 18 intended. The directional valve 18 has a pressure port P, a control room port A and a drain port T up. The pressure port P is connected to the pressure medium pump 7 of the hydraulic system 1 connected. The control room connection A is with the control room 13 and the drain port T to the tank 6 connected. In a first control position of the directional control valve 18 the control room terminal A is connected to the pressure port P, while the drain port T communicates with none of the other ports P, A. In a second control position of the directional control valve 18 the control room terminal A is connected to the drain port T, while the pressure port P communicates with none of the other ports T, A. In addition, another check valve 5b be provided, which in the control line 16 is arranged and a backflow of pressure medium from the control room 13 for pressure medium line 4 prevented.

wobei A₁ dem Flächeninhalt der ersten Druckfläche 10, A₂ dem Flächeninhalt der zweiten Druckfläche 11, p_max dem während der Befüllphase maximal auftretenden Systemdruck und D der Federkonstante des Federelements 23 entspricht. Dabei ist der maximale Verschiebeweg durch die Anschläge 14 begrenzt. Unter der Ausgangsstellung ist der Zustand des Druckkolbens 8 zu verstehen, in der das Federelement 23 maximal entspannt ist. Übersteigt das von dem Verbraucher 3 angeforderte Druckmittelvolumen bzw. der benötigte Druck die Kapazität der Druckmittelpumpe 7, so wird das Wegeventil 18 in dessen zweite Steuerstellung überführt. In dieser Steuerstellung ist der Steuerraum 13 mit einem Tank 6 verbunden. Das in dem Steuerraum 13 unter Druck stehende Druckmittel wird somit mit atmosphärischem Druck verbunden, wodurch eine rapide Entleerung des Steuerraums 13 erfolgt. Gleichzeitig wird der Vorratsraum 12 in das Hydrauliksystem 1 entleert. Erfolgt die Druckmittelentleerung des Steuerraums 13 derart schnell, dass sich der Druckkolben 8 ausschließlich über die erste Druckfläche 10 gegenüber dem Vorratsraum 12 abstützt, so wirkt die gesamte Kraft des Federelements 23 lediglich auf den Vorratsraum 12. Somit gilt für den Druck p in dem Vorratsraum 12 zu Beginn des Entleervorgangs:

solange der Druckkolben 8 noch nicht vollständig ausgelenkt wurde, also nicht an den Anschlägen 14 anliegt. Da das Rückschlagventil 5a in der Druckmittelleitung 4 stromaufwärts der Vorratsleitung 15 angeordnet ist, ist sichergestellt, dass der gesamte Druck p und das gesamte Volumen des Vorratsraum 12 dem Verbraucher 3 zur Verfügung steht. Somit steht nicht nur, wie in Anwendungen mit konventionellen Druckspeichern, der aktuelle Systemdruck oder der maximale Befülldruck zur Verfügung, sondern ein um bis zu dem Faktor 1 + A₂/A₁ erhöhter Druck. Das Hydrauliksystem 1 kann somit durch Einstellen der zweiten Steuerstellung an dem Wegeventil 18 eine Druckunterstützung erfahren, die die Unterstützung durch konventionelle Druckspeicher um ein Vielfaches übersteigt. Somit kann die Druckmittelpumpe 7 auf den Normalbetrieb des Verbrauchers 3 ausgelegt werden, während von dem Verbraucher 3 kurzfristig benötigte höhere Druckmittelvolumina bzw. Betriebsdrücke durch den Druckspeicher 2 abgefangen werden können.During normal operation of the consumer 3 in which the of the pressure medium pump 7 provided pressure fluid volume or the pressure provided to the consumer 3 to operate, there is the directional control valve 18 in the first position. Thus, pressure medium reaches both via the supply line 15 in the pantry 12 , as well as over the control line 16 in the control room 13 , That in the pantry 12 or the control room 13 introduced pressure medium acts on the pressure surfaces 10 . 11 whereby the pressure piston 8th in the direction of the attacks 14 against the force of the spring element 23 is moved so that the volume of both the pressure chambers 12 . 13 increases. The pressure in the hydraulic system drops 1 , For example, due to an increased pressure medium requirement of the consumer 3 , so the pressure in the pantry sinks to the same extent 12 , Due to the pressure gradient between the control room 13 and the hydraulic system 1 closes the check valve 5b in the control line 16 , causing a pressure drop in the control room 13 and a pressure medium flow can be avoided from this. This has the consequence that the volume of the control room 13 and the pantry 12 despite the pressure drop in the hydraulic system 1 remains constant. It applies to the path x, the pressure piston 8th was deflected from its rest position:

where A _{1 is} the area of the first printing surface 10 , A ₂ the area of the second printing surface 11 , p _max the maximum system pressure occurring during the filling phase and D the spring constant of the spring element 23 equivalent. Here is the maximum displacement by the attacks 14 limited. Under the initial position is the state of the pressure piston 8th to understand in which the spring element 23 is maximally relaxed. Exceeds that of the consumer 3 Requested pressure medium volume or the required pressure, the capacity of the pressure medium pump 7 so becomes the directional control valve 18 transferred to its second control position. In this control position is the control room 13 with a tank 6 connected. That in the control room 13 pressurized fluid is thus connected to atmospheric pressure, thereby rapidly evacuating the control chamber 13 he follows. At the same time the storeroom becomes 12 in the hydraulic system 1 emptied. Does the pressure medium discharge of the control room 13 so fast that the pressure piston 8th exclusively via the first printing surface 10 opposite the pantry 12 supported, so affects the entire force of the spring element 23 only on the pantry 12 , Thus applies to the pressure p in the pantry 12 at the beginning of the emptying process:

as long as the pressure piston 8th was not completely deflected, so not at the attacks 14 is applied. Because the check valve 5a in the pressure medium line 4 upstream of the supply line 15 is arranged, it is ensured that the total pressure p and the entire volume of the pantry 12 the consumer 3 is available. Thus, not only is the current system pressure or the maximum filling pressure available, as in applications with conventional pressure accumulators, but a pressure increased by up to a factor of 1 + A ₂ / A ₁ . The hydraulic system 1 can thus by adjusting the second control position on the directional control valve 18 experienced a pressure support that exceeds the support of conventional accumulators many times over. Thus, the pressure medium pump 7 on the normal operation of the consumer 3 be designed while by the consumer 3 short-term required higher pressure fluid volumes or operating pressures through the pressure accumulator 2 can be intercepted.

wobei p_sys dem bei Beginn der Druckunterstützung herrschenden Systemdruck entspricht. Denkbar ist der Einsatz dieser Ausführungsform Anwendungen in denen der benötigte Spitzensystemdruck nur geringfügig oberhalb der Kapazität der Druckmittelpumpe 7 liegt. In diesem Fall kann auf das Rückschlagventil 5b in der Steuerleitung 16 verzichtet werden, wodurch die Kosten sinken.Likewise conceivable are embodiments in which the arrangement of a check valve 5b in the control line 16 is waived. In the normal operating phases of the consumer 3 , the accumulator fills up 2 analogous to the embodiment described above. If the system pressure drops, then pressure medium flows both from the storage room 12 as well as from the control room 13 from. This leads to a pressure drop in both rooms 12 . 13 , causing a displacement of the plunger 8th leads in the direction of its rest position. Thus, in this embodiment, both the pressure medium volume which can be provided for the phase adjustment and the pressure which can be provided in the storage space 12 lowered. Nevertheless, the pressure increase takes place in the storage room 12 instead, if the directional control valve 18 is transferred to the second switching position. In this case applies to the provided pressure p at not yet completely deflected pressure piston 8th :

wherein p _sys corresponds to the pressure prevailing at the beginning of the pressure support system pressure. The use of this embodiment is conceivable applications in which the required peak system pressure only slightly above the capacity of the pressure medium pump 7 lies. In this case, the check valve 5b in the control line 16 be omitted, which reduces costs.

gelten. Um dies zu erreichen ist vorgesehen, dass für den minimalen Durchflussquerschnitt zwischen dem Steuerraum 13 und dem Tank 6 A_S:

gilt, wobei A_V dem minimalen Durchflussquerschnitt zwischen dem Vorratsraum 12 und dem Verbraucher 3 entspricht.During the filling process of the pressure accumulator 2 the system pressure of the hydraulic system acts 1 on both the first and second printing surfaces 10 . 11 , According to the formula F = pA = p (A ₁ + A ₂ ), the energy storage takes on a greater force than would be the case with a pressure accumulator having only the pressure surface A ₁ . Will the accumulator 2 the hydraulic system 1 switched on (the directional control valve 18 transferred to the second switching position), so this increased force acts exclusively on the first pressure surface 10 on the pantry 12 , causing the in the pantry 12 prevailing pressure is increased. Prerequisite is that the control room 13 depressurized, ie a support of the energy storage on the pressure piston 8th force exerted not over the control room 13 he follows. To realize this, the ratio of the pressure medium flow from the control room must be realized 13 to the pressure medium flow from the storage room 12 Q _S / Q _V

be valid. To achieve this it is envisaged that for the minimum flow area between the control room 13 and the tank 6 A _S :

where A _{V is} the minimum flow area between the pantry 12 and the consumer 3 equivalent.

To the functioning of the pressure accumulator 2 to ensure is a vent 19 the spring chamber provided for pressure medium, which due to leakage between the pressure piston 8th and the housing 9 got into the spring chamber, into the tank 6 dissipate.

A further embodiment of the pressure accumulator according to the invention 2 is in 2 shown. Unlike the in 1 illustrated embodiment is a connecting line in this embodiment 20 inside the pressure piston 8th provided, which the storeroom 12 with the control room 13 combines. In the connection line 20 is an additional check valve 5c provided, which a pressure medium flow from the control room 13 to the pantry 12 allows an opposite pressure fluid flow but locks. The operation of the pressure accumulator 2 is essentially the same as in 1 illustrated first embodiment. In contrast to this, the pantry can 12 this embodiment on the control room 13 and the connection line 20 be filled. Thus, in the supply line 15 an additional hydraulic valve are arranged, by means of which the storage space 12 optionally from the hydraulic system 1 can be disconnected or connected to this. Will the accumulator 2 emptied, so prevails in the control room 13 a lower pressure than in the pantry 12 , Thus, the check valve closes 5c , thereby emptying the pantry 12 in the tank 6 As an alternative to the illustrated embodiment, the connecting line including check valve 5c also in the case 9 be arranged.

3 shows a further embodiment of a pressure accumulator according to the invention 2 , This essentially corresponds to the first embodiment 1 , Unlike the first embodiment is no vent 19 provided the spring chamber. The spring chamber is rather than counter-pressure space 21 formed, which can be filled with pressure medium. The directional valve 18 is provided in this embodiment with an additional back pressure port G, which with the back pressure chamber 21 communicated. In a first control position of the directional control valve 18 the control chamber connection A is connected to the pressure connection P, while the counterpressure connection G communicates with the outflow connection T. In a second control position of the directional control valve 18 the control room terminal A is connected to the drain port T, while the pressure port P communicates with the back pressure port G.

Is the directional valve 18 in the first control position, there are no changes compared to the embodiment 1 on. In the second control position, however, additional pressure medium in the back pressure chamber 21 directed. This acts on a third pressure surface 22 of the pressure piston 8th with a force in the same direction as the spring element 23 acts. This will increase the pressure in the pantry 12 additionally increased. Furthermore, on the pressure piston 8th or the housing 9 sealing elements 26 be provided, which abut both components and leakage between the pressure chambers 12 . 13 and between the control room 13 and the backpressure room 21 minimize.

LIST OF REFERENCE NUMBERS

1

hydraulic system

2

accumulator

3

consumer

4

Pressure medium line

5a, b, c

check valve

6

tank

7

Hydraulic pump

8th

pressure piston

9

casing

10

first printing surface

11

second printing surface

12

pantry

13

control room

14

attack

15

supply line

16

control line

17

control means

18

way valve

19

vent

20

connecting line

21

Counterpressure chamber

22

third printing surface

23

spring element

24, 25

Pressure medium connection

26

sealing element

P

pressure connection

T

drain connection

A

Control space connection

G

Back pressure port

Claims (12)

Accumulator ( 2 ) with a housing ( 9 ), one inside the housing ( 9 ) arranged displaceable element ( 8th ) and an energy store ( 23 ), Wherein the displaceable element ( 8th ) a first printing surface ( 10 ), wherein the first pressure surface ( 10 ) and the housing ( 9 ) a storeroom ( 12 ) at least partially and • wherein the displaceable element ( 8th ) by pressurizing the storage space ( 12 ) against the force of the energy store ( 23 ), characterized in that • the displaceable element ( 8th ) a second printing surface ( 11 ), wherein the second printing surface ( 11 ) and the housing ( 9 ) a control room ( 13 ) at least partially, • whereby the displaceable element ( 8th ) by pressurizing the control room ( 13 ) also against the force of the energy storage ( 23 ) and • where the accumulator ( 2 ) is designed such that a pressure medium flow within the pressure accumulator ( 2 ) between the control room ( 13 ) and the storage room ( 12 ) at least in the direction of the control room ( 13 ) is locked or can be locked. Accumulator ( 2 ) according to claim 1, characterized in that the storage space ( 12 ) with a consumer ( 3 ) is connectable. Accumulator ( 2 ) according to claim 1, characterized in that the storage space ( 12 ) with a consumer ( 3 ) communicates. Accumulator ( 2 ) according to claim 1, characterized in that the control room ( 13 ) without pressure with a tank ( 6 ) can be connected. Accumulator ( 2 ) according to claim 1, characterized in that the control room ( 13 ) without pressure with a tank ( 6 ) can be connected, without at the same time the pantry ( 12 ) with the tank ( 6 ) communicates. Accumulator ( 2 ) according to claim 1, characterized in that the control room ( 13 ) independent of the storage room ( 12 ) can be emptied. Accumulator ( 2 ) according to claim 1, characterized in that the control room ( 13 ) optionally with a pressure source ( 7 ) or a tank ( 6 ) can be connected. Accumulator ( 2 ) according to claim 7, characterized in that control means ( 17 ) are provided, wherein the control room ( 13 ) by means of the control means ( 17 ) optionally with a tank ( 6 ) or a pressure source ( 7 ) can be connected. Accumulator ( 2 ) according to claim 1, characterized in that a pressure medium loading of the storage space ( 12 ) the displaceable element ( 8th ) is displaced in the same direction as a pressurization of the control room ( 13 ). Accumulator ( 2 ) according to claim 1, characterized in that the displaceable element ( 8th ) a third printing surface ( 22 ) having a counterpressure space ( 21 ) is at least partially limited, wherein a pressure medium loading of the back pressure chamber ( 21 ) the displaceable element ( 8th ) is displaced in the opposite direction as a pressurizing of the control chamber ( 13 ) or the storage room ( 12 ). Accumulator ( 2 ) according to claim 1, characterized in that the storage space ( 12 ) with a consumer ( 3 ) is at least connectable, the control room ( 13 ) with a tank ( 6 ) and the ratio between the minimum flow area between the control space ( 13 ) and the tank ( 6 ) and the minimum Flow area between the storage room ( 12 ) and the consumer ( 3 ) is greater than the ratio between the area of the second printing surface ( 11 ) and the area of the first printing surface ( 10 ). Accumulator ( 2 ) according to claim 1, characterized in that the storage space ( 12 ) and the control room ( 13 ) within the accumulator ( 2 ) do not communicate with each other.

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