WO2010136269A1

WO2010136269A1 - Hydraulic cylinder assembly for a machine for producing a fiber web, especially a paper or cardboard making machine

Info

Publication number: WO2010136269A1
Application number: PCT/EP2010/055278
Authority: WO
Inventors: Ville Hopponen; Arto Ikonen
Original assignee: Metso Paper, Inc.
Priority date: 2009-05-29
Filing date: 2010-04-21
Publication date: 2010-12-02
Also published as: CN102449321A; AT510947B1; DE102009026604A1; AT510947A5

Abstract

The invention relates to a hydraulic cylinder assembly for a machine for producing a fiber web, especially a paper or cardboard making machine. The assembly comprises a hydraulic cylinder (2) having a cylinder housing (21) and a piston (27) which can be displaced inside the cylinder housing, said piston subdividing the cylinder housing into a chamber (22) on the cylinder head side and a chamber (23) on the cylinder back end side, and at least one digital hydraulic pressure controller (3) which is integrated into the assembly. Said pressure controller is associated with the chamber on the cylinder head side and the chamber on the cylinder back end side and controls a supply of working fluid to and a discharge thereof from the chambers to adjust the pressure of the working fluid in at least one of the chambers of the hydraulic cylinder (2).

Description

Hydraulic cylinder assembly for a machine for producing a fibrous web, in particular a paper or board machine

description

The invention relates to a hydraulic cylinder assembly for a machine for producing a fibrous web, in particular a paper or board machine.

In paper machines, actuating cylinders are widely used as actuation and control means. These actuating cylinders are preferably hydraulically driven, so that large forces can be set and applied with high accuracy.

Typically, a working fluid, e.g. Hydraulic oil, air, water, different gases or emulsions of the previous fluids, etc., used, which is pressurized by a pump. The introduction of the pressurized hydraulic oil into a hydraulic actuator, e.g. A hydraulic cylinder or a hydraulic motor is usually controlled by a proportional control valve (proportional valve) which may be electrically, hydraulically or pneumatically driven.

Such a control valve has a spool or spool reciprocable in a valve housing which, in response to its location in the valve housing, can adjust a desired pressure at the outlet by controlling the pressure of the hydraulic oil delivered by the pump. The mobility of the control piston in the valve housing necessarily requires a certain clearance or gap between the control piston and the valve housing, so that a Leakage of hydraulic oil within the control valve is unavoidable. The gap size must not be too narrow, otherwise the valve is too susceptible to contamination in the hydraulic oil.

Recently, alternative pressure regulators have been developed which are referred to throughout this application as digital hydraulic pressure regulators. The operation of digital hydraulic pressure regulators is summarized below:

In the simple case, a digital hydraulic pressure regulator consists of a series of valves connected in parallel, which only have an OPEN / CLOSE function; Thus, they are simple ON / OFF switching valves that allow or interrupt fluid flow and are referred to hereafter as valves or digital valves in this application. The valves are all connected to a common supply line on the one hand and to a common outlet line on the other. The valves themselves may be conventional solenoid valves, i. Be valves with electromagnetic drive. Such an electromagnetically operable valve is e.g. in EP 1 052 441 A2. Of course, other forms of drive can be chosen.

By connecting or installing throttle elements to the valves or by the design of the valves themselves, it is ensured that the valves have different flows when they are open. If, for example, four valves are provided, then the flow rates Q in the individual, in each case by the associated valve selectively releasable passages in the ratio of 1: 2: 4: 8 to each other; for a larger number of valves this series will continue accordingly. By opening and closing individual valves or valve combinations, which are determined and selected on the basis of models from a computer, a very rapid and precise pressure adjustment in the outlet line or in the adjoining actuator can now be achieved by the analogue control curve of the initially described proportional valve is replaced by a digitally created (ie approximate) control curve. This curve may be due to the omission of non-linearities and / or hysteresis loops of the analog

Proportional valve be a step-like approximate straight line, which allows to approach a control point quickly and almost free of overshoot.

Another advantage of using digital hydraulic pressure regulators is that the valves are either open or closed, i. To maintain a desired pressure in a closed (and thus stationary) system, the valves of the pressure regulator are simply closed and there are no leakage flows inside the valves. This is a clear difference to the conventional proportional valve, which is always flowed through by a hydraulic oil flow. This constantly costs energy for the hydraulic pumps, e.g. in the paper machine.

Thus, it can be seen that the use of digital hydraulic pressure regulators allows the hydraulic pumps to operate less often and / or shorter, thereby saving energy.

However, there is still a need to reduce the energy consumption of a machine for producing a fibrous web, especially a paper or board machine, to further reduce.

It is therefore the object of the invention to provide a hydraulic cylinder assembly for a machine for producing a fibrous web, in particular a paper or board machine, with which the energy consumption for the hydraulic control of a hydraulic cylinder assembly for a paper or board machine is further reduced.

The object of the invention is achieved with a hydraulic cylinder assembly for a machine for producing a fibrous web, in particular a paper or board machine, with the features of claim 1.

Advantageous developments of the assembly according to the invention are set forth in the subclaims.

According to one aspect of the invention, there is provided a hydraulic cylinder assembly for a machine for producing a fibrous web, in particular a paper or board machine. The assembly has a hydraulic cylinder including a cylinder housing and a piston movable in the cylinder housing, dividing the cylinder housing into a cylinder head chamber and a cylinder bottom chamber, and at least one digital hydraulic pressure regulator integrated into the assembly, the cylinder head side chamber and the cylinder head side chamber associated with the cylinder bottom side chamber, and which controls an inflow and outflow of working fluid to and from the chambers to adjust the pressure of the working fluid in at least one of the two chambers of the hydraulic cylinder. The following explanations always refer to a paper machine; However, this term is expressly to include all types of machines for the production of fibrous webs, so in particular also board machines, fibreboard machines and the like.

If a digital hydraulic pressure regulator is used instead of a conventional proportional valve, with the position of the hydraulic cylinder unchanged, the hydraulic fluid consumption, i. the internal leakage current in the controller zero. In a paper machine many adjustable elements are required and available; the adjustment is not often but only in relatively rare occurrences, such as start-up operations, web breaks and Neueinfädelungen the web, reel change or maintenance. The actuating movements, which are usually carried out by means of acting on the components to be adjusted in the paper machine hydraulic cylinders, thereby comprise a movement of a hydraulic cylinder and / or possibly a pressure build-up to any mechanical compressive forces, e.g. to generate a pressure in a gap between two rolls.

The inventors have now found that the expense of providing, installing and maintaining piping for the supply of a hydraulic cylinder to working fluid in a conventional paper machine is considerable. The materials used must be corrosion-resistant for the hot, humid environment, enormous distances have to be mastered, because a conventional paper machine is simply large (several tens of meters long), so that here

Material consumption of high-quality pipe material is a real cost factor. In addition, there are flow losses in the management of the fluid flows in the lines, either must be compensated by larger pipe cross-sections, ie more material consumption, or by higher pump power, ie by a higher energy consumption.

By assigning at least one digital hydraulic pressure regulator to the cylinder head side chamber and the cylinder bottom side chamber of the cylinder housing and the integration of the controller in the hydraulic cylinder assembly long cable guides can be omitted and a compact design can be ensured.

Preferably, the valves of the digital hydraulic pressure regulator are mounted directly on the hydraulic cylinder or in the piston of the hydraulic cylinder. In these advantageous embodiments of the invention, the valves of the digital hydraulic pressure regulator are attached directly to the hydraulic cylinder or in the piston itself. These designs are not only compact, but there are also few hydraulic connection points available. This improves reliability because there are few points in the hydraulic circuit that can leak.

Preferably, the piston is a reciprocating piston with piston rod. This piston may be a reciprocating hollow piston with a hollow piston rod, wherein in the piston optionally the valves of the digital hydraulic pressure regulator can be arranged and the hydraulic and electrical wiring of the digital hydraulic pressure regulator can be passed through the piston rod to the valves, whereby the Construction of the hydraulic cylinder housing can be simplified. Due to the hollow construction of the piston and the Piston rod is an additional space for the above-mentioned wiring only then usable, in contrast to a solid piston, which was produced in a solid construction. Thus, the available space within the piston and piston rod material can be optimally used for installation of the valves of the hydraulic pressure regulator and the corresponding lines. In this type of piston is further ensured that the valves of the hydraulic pressure regulator are installed in the piston, that their outlets are assigned directly to the cylinder head side chamber and the cylinder bottom chamber of the hydraulic cylinder, so that the piston rod ultimately occupies a position in the Essentially depends on the set by the pressure regulator difference in the pressures in the cylinder head side chamber and the cylinder bottom chamber of the hydraulic cylinder.

For the valves of the hydraulic pressure regulator, e.g. 2/2 solenoid valves from Matrix Mechatronics, preferably the 750 series.

When the valves of the digital hydraulic pressure regulator are mounted directly on the hydraulic cylinder, it is particularly preferred that the cylinder housing has an antechamber corresponding to the cylinder head side chamber and an antechamber corresponding to the cylinder bottom side chamber, which are hydraulically separated from each other and to which the valves of the digital hydraulic Pressure regulator are directly attached. Furthermore, the two prechambers can be formed by a cylinder envelope which surrounds the cylinder housing in a fluid-tight manner and has an annular space corresponding to the cylinder head side chamber and an annular space corresponding to the cylinder bottom side chamber define, wherein the annular spaces are hydraulically separated from each other by a partition wall disposed between the cylinder housing and the cylinder shell and the valves of the digital hydraulic pressure regulator are mounted on the peripheral surfaces thereof. Optionally, the cylinder envelope and the partition wall are integrally formed on the cylinder housing. In this design of the hydraulic cylinder, the outlets of the directly attached to the hydraulic cylinder (eg on the cylinder shell) valves of the digital hydraulic pressure regulator are assigned to the respective prechambers corresponding. The pre-chambers then have a common supply or exhaust port on the cylinder housing itself. The positions of the common ports on the cylinder housing are set so that a positional adjustment of the piston within the cylinder can be ensured by the differently adjustable pressures in the antechambers, regardless of the respective position of the piston. The piston and thus the piston rod ultimately assume a position which essentially depends on the difference between the pressures set by the pressure regulators in the antechamber assigned to the cylinder head side chamber and the prechamber assigned to the cylinder bottom side chamber.

In the above or other embodiments, the digital hydraulic pressure regulator may be a

Includes differential pressure control valve that switches a direct hydraulic connection between the cylinder head side chamber and the cylinder bottom side chamber and controls a flow of working fluid between the cylinder head side chamber and the cylinder bottom side chamber. Preferably, the volumes of the cylinder head side chamber and the cylinder bottom chamber be the same size.

According to the above embodiments of the invention, the hydraulic cylinder is a differential cylinder. In a differential cylinder, pressure-effective surfaces are formed on both the piston side and the piston rod side, so that the piston rod of the cylinder ultimately assumes a position which depends on the load acting on the piston rod and the difference of the pressures on the piston side and the rod side. In operation, when the position of the piston is to be adjusted, working fluid is fed under pressure into the cylinder chamber, the volume of which is to increase, while a corresponding amount of working fluid is discharged from the cylinder chamber, whose volume is to decrease. In this case, working fluid is discharged at a pressure level well above that of a reservoir, hereinafter referred to as a tank. This means that the previously invested pump energy, which is contained in this part of the working fluid to be discharged, is discharged into the tank unused. By the differential pressure control valve, which connects the two chambers of the cylinder together hydraulically, the working fluid can flow at high pressure level from one pressure chamber to the other and it may be necessary to apply only the pumping energy required to increase the pressure in this volume. This saves energy. Furthermore, by using the differential pressure control valve and a simplified structure of the digital hydraulic pressure regulator can be achieved in conjunction with a differential cylinder.

In the above embodiments, the assembly may further comprise an integrated pump to supply the working fluid at a sufficiently high pressure for the provide digital hydraulic pressure regulator. The pump can be mounted directly on the hydraulic cylinder. Further, the pump can feed the working fluid at high pressure into a hydraulically connectable with the digital hydraulic pressure regulator pressure accumulator and pressurize it.

In the embodiments shown above, the inventors have found that, with the elimination of the permanent leakage current in proportional control valves, there is actually so little demand for working fluid that it is energetically unfavorable to repeatedly turn on and off a pump of sufficient size for the leakage flow. The inventors have now found that the consumption of working fluid can also be covered by a pressure accumulator, wherein the pressure accumulator is charged with a pump from time to time. For this purpose, it is possible to associate each individual module with its own pressure accumulator and / or its own integrated pump or multiple modules with a common pressure accumulator and / or pump. In the second case, a single pump may be provided to charge the plurality of accumulators. In the case of multiple pressure accumulator these can also be charged one after the other individually, so that in the respective module temporarily integrable small pump, which is sized for the corresponding accumulator of the assembly is sufficient.

By assigning individual pressure accumulators to the individual modules, it is possible to provide a functional and spatial breakdown of the pressure supply areas, ie individual local pumps which can be integrated into the module are provided, which are independent of one another, so that long cable runs can be dispensed with. Furthermore, with a fast set of digital valves of a digital hydraulic pressure regulator on a pressure accumulator, the pressure in a nip or roller nip, for example, can be accurately controlled even though the level of the supply pressure varies slightly or decreases. The set of digital valves is also associated with the pressure accumulator in addition to the hydraulic cylinder to control the pressure and the volume flow delivered by the pressure accumulator. When the pressure accumulator is depleted, ie the energy stored therein has been released, the set of digital valves can switch to pump operation. The pressure control is carried out directly with the pumped working fluid and at the same time the accumulator is recharged. Then the pump switches off again and it is again taken working fluid from the pressure accumulator, whereby the energy costs can be significantly reduced.

The invention can be practiced with numerous modifications and options, some of which are described below. These modifications contribute to a simplified construction of the

Hydraulic cylinder assembly and / or to reduce energy consumption.

A conventional digital hydraulic pressure regulator has in the

Typically, a series or bank of valves connected in parallel for supplying working fluid to a pressure chamber of a hydraulic cylinder (e.g., a single-acting

Plunger cylinder, a double-acting

Differential cylinder, etc.) and a bank of parallel-connected valves for discharging working fluid from this pressure chamber. In general, one is

Differential cylinder with two pressure chambers a total of four

Assigned valve banks. With a switching valve (eg 4/2 Way valve), a simplification of the structure can be achieved by each a valve bank is connected to one cylinder pressure chamber, while the switching valve alternately connects the two valve banks with the tank or the pump (or the pressure source).

If digital hydraulic pressure regulators are used together with hydraulic cylinders, it is a particular advantage that these regulators have no leakage current. Therefore, working fluid volumes and piston position are very closely related, i. If one measures the volume of working fluid supplied to the cylinder, one can infer the actual position of the piston. In the operation of such a cylinder, the piston position may be an important quantity, in particular in the setting of accurate distances at high forces or with respect to a synchronization of movements.

The conventionally used sensors for this purpose are arranged on the outside of the cylinder and thus exposed to the adverse environmental conditions of, for example, paper machines, where it is often dusty and / or damp. As a result, this sensor is prone to failure.

Due to the close relationship between the output of the controller working fluid volume and the piston position can be closed according to a development of the invention from a volume flow measurement in the working fluid flow, for example, with gear flow meters on the piston position. In this case, the flow meter may be mounted at a location which is remote from the piston rod (whose position is to be detected). In addition, you can encapsulate such flow meters, since they only need to capture something that takes place inside them. In this way, a reliable piston position detection possible. Even if a measurement error occurs in the detection of the flow, this sensor assembly, especially if the return flow to and from the cylinder are separately detected and evaluated, is sufficiently accurate to detect malfunctions.

It is also possible to conclude from the operation of the digital hydraulic controller on the shifted working fluid volume by summing up the individual streams through the individual valves of a controller, taking into account the opening times. In this way, possibly even any flow meter can be saved. In this case, it is possible to use the knowledge that the opening times of the individual valves for the regulation are calculated anyway and from the calculation with the individual flow rates through the corresponding valves to the volume present in the respective pressure chamber and thus to the piston position.

For rapid control of streams of working fluids, the principle of digital hydraulics can also be used for flow regulators. As a rule, large valves with large cross-sections are used to control the considerable volume flows of the working fluid whose control accuracy is limited. For example, with the headbox of a paper machine, it is necessary to precisely control the composition of the pulp suspension to produce a paper of consistent quality. In this case dilution of the suspension (dilution) should be controlled by addition of water. This addition of water to establish a desired dilution can be controlled very precisely and responsively by means of digital hydraulic valve arrangements by providing the valves with the appropriate flow rates, as indicated at the beginning be described, opened or closed. By using several such digital hydraulic flow regulators with corresponding cross sections (the valves must still be able to be switched quickly enough), it is also possible to control large-volume material flows.

An important criterion for the quality (accuracy, overshoot, etc.) of the control by means of digital hydraulic regulators is the switching speed of the individual valves, i. how quickly the valves can be opened or closed. But for the rapid movement of the valve body in the valve are larger

(Acceleration) forces required than to hold the valve in the driven state. For this reason, so-called boosters or amplifiers can be used for the adjustment process, which supply a coil of the solenoid-operated valve briefly with an overvoltage, so that a stronger magnetic field is created and the valve body can be moved faster. An advantage of this technique is that these coils must be dimensioned only so large that they survive this short-term overload and endure a lower voltage in continuous operation.

The digital hydraulic controller arrangements described above are usually operated with hydraulic oil as working fluid. The use of oil is for the usual control valves for lubrication of the control piston basically required or at least beneficial. Since the digital hydraulic controllers only use simple shut-off valves, these are available

Lubrication requirement is no longer or not so much. Therefore, the working fluid may also be an aqueous emulsion (eg, an oil / water emulsion similar to the drilling mud) or even simple water. In addition to a significant reduction in the effort that must be made to protect the environment from pollution by leaking oil, there are also technical advantages. The viscosity of oil is temperature dependent. In digital hydraulic regulators fixed throttles for adjusting the flow rates through the individual valves are usually provided, the throttle effect shows a significant dependence on the viscosity of the working fluid. In the case of water or aqueous emulsions, the temperature has only a slight influence on the viscosity, so that the temperature sensitivity of the hydraulic system is low. Thus, it is not necessary to consider the temperature of the working fluid at the site of the digital hydraulic controller.

The invention will be further elucidated in the following with respect to various aspects by means of exemplary embodiments, with reference to the figures, in which:

Fig. 1 shows a schematic structure of a portion of a hydraulic cylinder assembly with digital hydraulic pressure regulators;

Fig. 2 shows a schematic structure of a portion of a hydraulic cylinder assembly with digital hydraulic pressure regulators, which are hydraulically connected to each other by differential pressure control valves;

Fig. 3 shows a portion of a

Hydraulic cylinder assembly with digital hydraulic pressure regulators, a differential pressure control valve, a hydraulic differential cylinder, an integrated Pump and a tank, and a pressure accumulator in a schematic diagram;

Fig. 4 shows a portion of a

Hydraulic cylinder assembly with digital hydraulic pressure regulators, a differential pressure control valve, a hydraulic differential cylinder, an integrated pump, a tank and a pressure accumulator in a schematic diagram;

Fig. 5 shows a schematic structure of a hydraulic cylinder assembly with digital hydraulic pressure regulators whose valves are arranged in a piston of the hydraulic cylinder;

Fig. 6 shows a portion of a

Hydraulic cylinder assembly with digital hydraulic pressure regulators, a differential pressure control valve and a hydraulic differential cylinder, and a pressure accumulator in a schematic diagram; and

Fig. 7 shows a portion of a

Hydraulic cylinder assembly with a digital hydraulic pressure regulator, a differential pressure control valve, a hydraulic differential cylinder and a

Directional control valve, and a pressure accumulator in a schematic diagram.

In the following description of the figures, the same or functionally identical elements are designated by the same reference numerals, so that the general functional description is made only with reference to a Fig. And then referenced. Further, if in the following text of pressure regulators or flow controllers, so these are, unless otherwise stated , digital hydraulic pressure regulators or flow controllers that operate using the digital hydraulic principle explained in the introduction at the outset.

FIG. 1 schematically shows a structure of a portion of a hydraulic cylinder assembly 1 according to a first embodiment of the present invention.

This hydraulic cylinder assembly 1 has a hydraulic cylinder 2 and four digital hydraulic pressure regulator 3. The hydraulic cylinder 2 is a hydraulic differential cylinder 2 and has a cylinder housing 21 and a piston 27 movable in the cylinder housing. The cylinder housing 21 is divided by a head of the piston 27 into a cylinder head side chamber 22 and a cylinder bottom side chamber 23. Furthermore, the cylinder housing 21 has an antechamber 24 corresponding to the cylinder head side chamber 22 and an antechamber 25 corresponding to the cylinder bottom side chamber 23. These two prechambers 24, 25 are hydraulically separated from each other by a partition wall 26 which extends radially outwardly and annularly around the housing 21 from the periphery of the cylinder housing 21. The two pre-chambers 24, 25 are formed by a cylindrical housing surrounding the cylinder housing 21 fluid-tight, whereby a corresponding to the cylinder head side chamber 22 annulus

(i.e., the cylinder head side prechamber 24) and an annular space corresponding to the cylinder bottom side chamber 23

(ie the cylinder bottom side pre-chamber 25) between the cylinder housing 21 and the cylinder cover 29 are fixed. These two annular spaces are separated hydraulically from one another by the partition wall 26 arranged between the cylinder housing 21 and the cylinder envelope 29. The Partition 26 is fixedly connected to the cylinder housing 21 and the cylinder cover 29 (eg welded).

A piston rod 28 of the piston 27 is disposed in the cylinder head side chamber 22. The piston 27 is slidably received in the usual manner in the cylinder housing 21 to be reciprocable in this. The piston rod 28 passes on the cylinder head side through a bore in the cylinder head cover 29, which encloses the cylinder housing 21 and thus both the cylinder head side chamber 22 and the cylinder bottom side chamber 23 fluid-tight and seals.

In each case two digital hydraulic pressure regulator 3 are connected to a common supply line 32 and a common outlet 33 and arranged integrated in this. Each pressure regulator 3 has in the supply line 32 and outlet line 33 in each case five digital hydraulic valves 31 (ON / OFF valves) arranged in parallel and throttle elements 34 which are fastened directly to the cylinder envelope 29 of the hydraulic cylinder 2.

For example, as the valve 31, a conventional control valve of the type GSR-RRV 95, which is e.g. in EP 1 052 441 A2. The operation and structure of such a digital valve are described in detail in this document.

The common supply pipe 32 and the common exhaust pipe 33 are filled with a working fluid (for example, hydraulic oil, air, etc.). By installing the throttle elements 34 to the digital hydraulic valves 31 in corresponding line 32, 33 is ensured that the valves 31 have different flow rates when they are open. For example, you can through the upstream throttle elements 34, the flow rates Q of the working fluid in the individual, each of the correspondingly associated valves 31 selectively releasable passages in the ratio of 1: 2: 4: 8: 16 to each other.

The common supply line 32 is thus hydraulically connected via the parallel valves 31 and throttle elements 34 of the two pressure regulator 3, which are shown schematically on the left side in Fig. 1, with the cylinder head side chamber 22 and with the cylinder bottom side chamber 23. The common outlet line 33 is also hydraulically connected via the parallel-connected valves 31 and throttle elements 34 of the two pressure regulator 3, which are shown schematically on the right side in Fig. 1, with the cylinder head side chamber 22 and the cylinder bottom side chamber 23.

Sensors (not shown) detect the pressure and the temperature in the two pressure chambers 22 and 34 of the differential cylinder 2. The pressure in the cylinder bottom side (piston rod side) pressure chamber 23 acts on a rod side piston ring surface 281 while the pressure in the cylinder head side

(piston-side) pressure chamber 22 presses on the piston surface 271. The piston surface 271 includes an annular surface of the piston 27 and a frusto-conical surface of a brake cone of the piston 27 on the cylinder head side. Other sensors

(not shown) detect the pressure Pzu in the supply line 32 and the pressure Pab in the outlet 33. With the four pressure regulators 3, the amount and pressure in the two pressure chambers 22 and 23 can be adjusted so that the piston rod 28 in the desired position and with the desired force with a machine element connected thereto (not shown) cooperates. The pressure Pzu in the supply line 32 from which the cylinder 2 is to be controlled is measured by means of the pressure sensor, and from this, the target pressure in the pressure chambers 22 and 23 is adjusted by controlling the flow rates in the valves 31 of the pressure regulator 3 to slidably move the piston rod 28 within the cylinder housing 21 and bring it into a desired desired position. That is, by appropriately switching on and off the valves 31 which are attached to the cylinder liner 29, thus, an inflow and outflow of the working fluid to and from the respective chambers of the hydraulic cylinder 2 can be controlled to thereby reduce the pressure of the working fluid in at least one from the cylinder head side chamber 22 and the cylinder bottom side chamber 23, whereby the position of the piston 27 within the cylinder housing 21 is adjusted accordingly.

2, a schematic structure of a portion of a hydraulic cylinder assembly 1 according to a second embodiment of the present invention is shown schematically.

The structure of this embodiment substantially corresponds to the structure of the hydraulic cylinder assembly 1 as shown in FIG. However, this hydraulic cylinder assembly 1 additionally comprises two

Differential pressure control valves 35, each of which provides a direct hydraulic connection between the cylinder head side prechamber 24 and the cylinder bottom side prechamber 25 on the supply line side and the outlet line side. Each differential pressure control valve 35 is arranged on the cylinder shell 29 in the region of the partition wall 26, ie in the region between the cylinder head side prechamber 24 and the cylinder bottom side prechamber 25 on the cylinder shell 29, and thus integrated within the assembly 1.

By the respective differential pressure control valve 35, which connects the two chambers 22, 23 of the cylinder 2 together hydraulically, the working fluid can flow at high pressure level from one pressure chamber to the other and it is thus only necessary to provide such a pumping energy, the further pressure increase in the respective chamber is required to change the position of the piston rod 27. That is, that

Differential pressure control valve 35 regulates a flow of working fluid between the cylinder head side chamber 22 and the cylinder bottom side chamber 23.

Preferably, the differential pressure control valve 35 is controlled during a rapid positional adjustment of the piston 27 and the piston rod 28 (to open) to allow a flow from one pressure chamber to the other, without an additional flow control of attached to the cylinder cover 29 valves 31 in elevated Dimensions must be used. The function of this differential pressure control valve 35, which allows a hydraulic connection between the two chambers 22 and 23 optionally, is explained below with reference to FIG. 3 again.

3 shows a section of a hydraulic cylinder assembly 1 according to a third exemplary embodiment with digital hydraulic pressure regulators 3, a differential pressure control valve 35, a hydraulic differential cylinder 2, an integrated hydraulic pump 4 and a tank 6, and a pressure accumulator 5 in a schematic diagram.

A supply section to the accumulator 5, the hydraulic pump 4 and the tank 6 supplies the four pressure regulator 3 for operation of the differential cylinder 2. Sensors detect the pressure in the two pressure chambers 22 and 23 of the differential cylinder 2, separated by the piston 27 with the piston rod 28 are. With the pressure regulators 3, the filling amount and pressure in the two pressure chambers 22 and 23 can be adjusted so that the piston rod 28 in the desired position and with the desired force with a machine element connected thereto (not shown) cooperates.

The pressure in the pressure supply section from which the cylinder 2 is to be controlled is measured by means of a pressure sensor 41, and from this, the target pressure in the pressure chambers 22 and 23 is adjusted.

In FIG. 3, unlike the structure of the hydraulic power pack 1 of FIG. 1, each of the four digital hydraulic pressure regulators 3 has six instead of five digital valves 31. The throttle elements 34 associated with the digital hydraulic valves 31 have different throttle openings, i. the throttle diameters are in the ratio 0.3: 0.4: 0.6: 0.8: 1.1: 1.5 mm to each other.

Furthermore, the hydraulic pump 4, which can be driven by an electric motor, as a pump integrated in the assembly 1 and the tank (oil tank or working fluid tank) 6 are mounted (integrated) within the assembly 1, indicated by the dotted line in FIG. 3 is shown. The pump 4 serves to the working fluid with sufficiently high pressure for the digital hydraulic pressure regulator 3 to provide or maintain the pressure in a pressure accumulator 5, which is not integrated into the assembly 1. Since the pump is hydraulically connected to the pressure accumulator 5, an operation of the pump 5 is only required to raise the pressure in the pressure accumulator 5 back to a certain pressure level. Thus, most of the time a pressure for the digital hydraulic pressure regulator 3 can be provided from the pressure accumulator 5 without the pump 4 being operated by the electric motor.

Thus, the pressure regulator 3, the pump 4 with its electric motor drive and the tank 6 are arranged as a separate block on the cylinder housing 21, and the pressure regulators are hydraulically connected via hydraulic lines 34 directly to the cylinder head side chamber 22 and the cylinder bottom side chamber 23. Prechambers are not provided in this embodiment.

By a correspondingly close arrangement of the pressure regulator 3, the pump 4 and the tank 6 to the cylinder 2 no long hydraulic lines are required.

Further, between the two chambers 22, 23 in the hydraulic circuit of the hydraulic cylinder assembly 1, a connecting line to the differential pressure control valve 35 is connected, the pressure chambers 22, 23 separated from each other in the closed state. When the differential pressure control valve 35 opens, the two pressure chambers are connected or shorted together. As a rule, a load or force is applied to the piston rod 28, which tends to push the piston rod 28 into the cylinder 2. If now the piston rod 28 of the load following in the cylinder 2 are retracted, as occurs for example when opening a nip, the differential pressure control valve 35 is opened and the digital valves 31 of the cylinder bottom side chamber 23 corresponding pressure regulator 3 remain closed. Thus, the working fluid flows partly into the cylinder head side chamber 22 and partly into the tank 6. The outflow into the tank is controlled by pressure regulators 3 corresponding to the cylinder head side chamber 22, and thus the lowering speed of the piston rod 27 is controlled.

Because the working fluid is short-circuited to fill the cylinder bottom side pressure chamber 23, this working fluid amount does not need to be taken out of the pressure supply section. The working fluid does not have to be first pumped by the pump 4 and brought to high pressure, in order then to be fed with regulated down pressure in the pressure chamber 23. Overall, the volume to be moved by the pump 4 is reduced, which saves energy.

Further, because the corresponding to the cylinder bottom side chamber 23 pressure regulator 3 remain off, eliminating the billing and control effort here. This halves the computational effort and the computing power for the controller 3 and also saves the drive energy for the operation of their valves 31 a.

Usually, as shown in this embodiment, the pump 4 is driven by an electric motor. Since in this embodiment, the pump 4 is not needed most of the time to provide a pressure in the digital hydraulic pressure regulator 3, this can often remain off, causing the Power consumption for operating the pump 4 (an operation of the electric motor) can be considerably reduced. By this arrangement, an energy saving of more than 99% compared to control valves is possible, which adjust a hydraulic actuator with a sliding spool or spool analog hydraulically.

According to this example, therefore, the

Hydraulic cylinder assembly 1 are used to control a gap of a paper machine calender. The gap is closed when the piston 27 of the cylinder 2 is urged in the direction of the cylinder head side chamber 22. When the piston 3 is located at its lowermost position in the cylinder bottom side chamber 23, the nip is fully opened, and at the highest position in the cylinder head side chamber 22, the nip is completely closed. To energize the nip, no energization is required since, by appropriate control of the digital and differential pressure control valves 35, a portion of the oil in the cylinder bottom chamber 23 is directed to the cylinder head chamber 22 of the hydraulic cylinder 2 via the differential pressure control valves 35 and a portion back to the tank 4 is guided.

In this pressure control in the chambers 22, 23 of the hydraulic cylinder assembly 1, a small amount of oil is required, whereby it is possible that an oil flow is required only during the closing movement of the nip, ie, it is necessary only during the closing of the nip of the pressure accumulator 5 or by an operation of the pump 4 oil in the oil circuit of the hydraulic cylinder assembly 1 is fed. FIG. 4 shows substantially the same structure as the embodiment in FIG. 2 of the hydraulic cylinder assembly 1 in which the digital hydraulic pressure regulators 3 and the differential pressure control valves 35 are directly attached to the cylinder liner 29. Furthermore, in this embodiment, the hydraulic cylinder assembly 1 also includes the pump 4, the tank 6 and the pressure accumulator 5. That is, the pump 4, the tank 6 and the pressure accumulator 5 are integrated into the assembly 1, which is represented schematically by the outer dash-dotted lines , Thus, in this embodiment, the hydraulic lines between the individual components of the assembly 1 can be further shortened.

FIG. 5 schematically shows a further exemplary embodiment of the hydraulic cylinder assembly 1 with digital-hydraulic pressure regulators 3, whose valves 31, 35 and throttle elements 34 are arranged in the piston 27 of the hydraulic cylinder 2. The operation of this hydraulic cylinder assembly 1 is the same as that described above in the embodiments of FIGS. 1 to 4.

In contrast to the structural design of the hydraulic cylinder assembly 1 of the above-described embodiments of Figs. 1 to 4 is provided in this hydraulic cylinder assembly of the piston 27 is a reciprocating double-acting, hollow piston with a hollow piston rod. In the head of this hollow piston 27, the valves 31 and throttle elements 34, which are described in detail above, are arranged. The hydraulic and electrical wiring of the digital hydraulic pressure regulator 3 are through the hollow piston rod 28 through to the respective parallel switched valves 31 of the digital hydraulic pressure regulator 3 out. In this embodiment, the volumes of the cylinder head side chamber 22 and the cylinder bottom side chamber 23 are substantially equal in size.

In this design of the piston 27 is further ensured that the valves 31 of the hydraulic pressure regulator 3 are installed in the piston such that their outlets A, B are assigned directly to the cylinder head side chamber 22 and the cylinder bottom side chamber 23 of the hydraulic cylinder 2, so that the piston rod 28 ultimately occupies a position which depends essentially on the difference set by the pressure regulator 3 of the pressures in the cylinder head side chamber 22 and the cylinder bottom side chamber 23 of the hydraulic cylinder 2.

Further, as already shown in the embodiment of Fig. 4, the pressure accumulator 5 and the pump 4, which is driven by an electric motor, and the oil tank 6 with the respective parallel-connected valves 31 and throttle elements 34 are hydraulically connected. For example, a hydraulic digital valve may be provided for the valves 31 (e.g., a 750 series matrix valve).

In this construction, the hydraulic cylinder assembly 1 can be dispensed with by the arrangement of the pressure regulator 3 in the piston 27 also on the cylinder envelope and thus on the antechambers in the design of the cylinder housing 21. This type of hydraulic cylinder assembly 1 according to the embodiment of FIG. 5 is used for example in adjusting cylinders in Mehrwalzenkalandern.

Further embodiments according to the present invention are shown in FIGS. 6 and 7. Fig. 6 shows a portion of a hydraulic cylinder assembly with digital hydraulic pressure regulators, a differential pressure control valve and a hydraulic differential cylinder, and a pressure accumulator in a schematic diagram. Fig. 7 shows a portion of a hydraulic cylinder assembly with digital hydraulic pressure regulators, a differential pressure control valve, a hydraulic differential cylinder and a

Directional control valve, and a pressure accumulator in a schematic diagram.

In these two embodiments shown in FIGS. 6 and 7, the differential pressure control valve 35 is also disposed between the cylinder head side chamber 22 and the cylinder bottom side chamber 23 to provide a hydraulic connection between these two chambers, in particular while the piston 27 is to perform a rapid movement.

As shown in FIG. 6, the hydraulic cylinder assembly 1 (see dotted line) consists of two digital hydraulic pressure regulators 3, the differential pressure control valve 35, two digital valves 36 associated with the digital hydraulic pressure regulators 3 and the hydraulic one

Differential cylinder 2. The pressure accumulator 5 is hydraulically connected to the assembly 1. With the two pressure regulators 3 in Fig. 6, the pressures and filling volumes of the pressure chambers 22, 23 of the differential cylinder 2 are regulated; this was previously explained in detail with another controller design, so that a repetition is omitted here.

The two pressure regulators 3 each have five digital valves 31, which are connected in parallel within the respective regulator; the regulators 3 may have the same construction as in the previously explained in detail pressure regulators of the preceding embodiments.

The pressure regulators 3 have a construction like the pressure regulator 3 described with reference to FIGS. 2, 3 and 4. The pressure regulator 3 disposed at the top of the figure is connected to a tank (not shown) while the lower pressure regulator 3 is connected to the pressure accumulator 5 is. The thus pressurized, lower regulator 3 can supply working fluid into the connected pressure chamber 22 of the cylinder 3, while working fluid from the other pressure chamber 21 via the upper regulator 3 can flow into the tank.

For example, when the differential pressure control valve 35 is closed, the pressure of the cylinder bottom side chamber 23 can be adjusted to generate larger forces. Thus, the pressure acting in the cylinder head side chamber 22 is then discharged to the tank via a discharge valve (not shown). By the hydraulic coupling of the two chambers by means of the differential pressure control valve 35, when the piston 27 is urged in the direction of the cylinder bottom side chamber 23, the working fluid via the differential pressure control valve 35 is supplied directly to the cylinder head side chamber 22, whereby a volume flow of the working fluid through the digital valves 31st and the throttle element 34 in the pressure regulators 3 to the tank (not shown) is extremely low.

As shown in FIG. 7, by additionally using a directional control valve 37 (ie, 4/2-way valve) upstream of the group of digital valves 31, the number of digital hydraulic pressure regulators 3 can be reduced to one, thereby also increasing the total number of digital valves 31 , 35, 36 reduced to nine. The directional control valve 37 can control the flow of oil such that the chambers 22, 23 can be alternately pressurized.

In both embodiments of the

Hydraulic cylinder assembly in Fig. 6 and 7 decreases during the movement of the piston 27, the volume of a pressure chamber, while the volume of the other pressure chamber increases; There are no operating conditions in which both pressure chambers are pressurized simultaneously or both are discharged simultaneously.

With this arrangement of pressure regulators, the required number of digital valves can be halved (Fig. 6) or further reduced (Fig. 7) compared to the arrangement of the pressure regulators in the embodiments of Figs. Thus, the investment costs for the machine for producing a fibrous web, in particular a paper or board machine, can be further reduced.

Claims

claims

Hydraulic cylinder assembly (1) for a machine for producing a fibrous web, in particular a paper or board machine, comprising a hydraulic cylinder (2) comprising a cylinder housing (21) and a in the cylinder housing (21) movable piston (27), the cylinder housing (21) into a cylinder head side chamber (22) and a cylinder bottom side chamber (23) divided, and at least one digital hydraulic pressure regulator (3), which is integrated in the assembly (1), the cylinder head side chamber (22) and the cylinder bottom side chamber ( 23), and which controls an inflow and outflow of working fluid to and from the chambers (22, 23) to adjust the pressure of the working fluid in at least one of the two chambers (22, 23) of the hydraulic cylinder (2).

Second hydraulic cylinder assembly (1) according to claim 1, characterized in that valves (31) of the digital hydraulic pressure regulator (3) directly to the hydraulic cylinder (2) are mounted.

3. hydraulic cylinder assembly (1) according to claim 1, characterized in that valves (31) of the digital hydraulic pressure regulator (3) in the piston (27) of the hydraulic cylinder (2) are mounted.

4. hydraulic cylinder assembly (1) according to one of claims 1 to 3, characterized in that the piston (27) is a reciprocating piston (27) with piston rod (28).

5. hydraulic cylinder assembly (1) according to claim 2, characterized in that the cylinder housing (21) to the cylinder head side chamber (22) corresponding pre-chamber (24) and one to the cylinder bottom side chamber

(23) corresponding pre-chamber (25) which are hydraulically separated from each other and to which the valves (31) of the digital hydraulic pressure regulator (3) are directly attached.

6. hydraulic cylinder assembly (1) according to claim 5, characterized in that the two prechambers (24, 25) by a cylinder housing (21) fluid-tight surrounding cylinder envelope (29) are formed and to the cylinder head side chamber (22) corresponding annular space (24 ) and one to the cylinder bottom side chamber

(23) corresponding annular space (25) define, wherein the annular spaces (24, 25) by a between the cylinder housing

(21) and the cylinder envelope (29) arranged separating wall (26) are hydraulically separated from each other and on the peripheral surfaces of the valves (31) of the digital hydraulic pressure regulator (3) are mounted.

7. hydraulic cylinder assembly (1) according to claim 6, characterized in that the cylinder envelope (29) and the partition wall (26) are integrally formed on the cylinder housing (21).

8. hydraulic cylinder assembly (1) according to one of claims 1 to 7, characterized in that the digital hydraulic pressure regulator (3) a

Differential pressure control valve (35) which switches a direct hydraulic connection between the cylinder head side chamber (22) and the cylinder bottom side chamber (23) and a flow of working fluid between the cylinder head side chamber (22) and the cylinder bottom side (23) chamber controls.

9. hydraulic cylinder assembly (1) according to claim 3, characterized in that the piston (27) is a reciprocating hollow piston with a hollow piston rod.

10. hydraulic cylinder assembly (1) according to claim 9, characterized in that in the hollow piston, the valves (31) of the digital hydraulic pressure regulator (3) are arranged and the hydraulic and electrical wiring of the digital hydraulic pressure regulator (3) through the piston rod through to the valves (31) is guided.

11. Hydraulic cylinder assembly (1) according to one of claims 1 to 10, characterized in that the volumes of the cylinder head side chamber (22) and the cylinder bottom side chamber (23) are equal.

The hydraulic cylinder assembly (1) according to any one of claims 1 to 11, characterized in that the assembly (1) further comprises an integrated pump (4) for providing the working fluid at a sufficiently high pressure to the digital hydraulic pressure regulator (3).

13. Hydraulic cylinder assembly (1) according to claim 12, characterized in that the pump (4) is mounted directly on the hydraulic cylinder (2).

14. Hydraulic cylinder assembly (1) according to claims 12 or 13, characterized in that the pump (4) further feeds the working fluid at high pressure into a digitally hydraulic pressure regulator (3) hydraulically connectable pressure accumulator (5) and pressurizes this.