EP2435713B1 - Method for removing foreign matter from a digital hydraulic pressure controller - Google Patents

Description

The invention relates to a method for removing foreign matter from a digital hydraulic pressure regulator of a hydraulic system and more particularly to a method for removing foreign matter from a digital hydraulic pressure regulator of a hydraulic system of a machine for producing a fibrous web, in particular a paper or board machine.

In paper machines, hydraulics is widely used as actuation and control means; In particular, actuators are hydraulically driven, with which large forces can be set and exercised with high accuracy.

Typically, a working fluid, e.g. Hydraulic oil used, which is pressurized by a pump. The introduction of the pressurized hydraulic oil into a hydraulic actuator, e.g. a hydraulic cylinder or hydraulic motor is typically controlled by a proportional control valve or proportional valve, which may be electrically, hydraulically, or pneumatically driven.

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

Recently, alternative pressure regulators have been developed, such as those from US 2009/0114284 A1 are known and to be referred to throughout this application as a digital hydraulic pressure regulator.

The operation of the digital hydraulic pressure regulator is already widely known. For improved readability of this application, however, the operation of digital hydraulic pressure regulators is briefly summarized below:

In the simple case, a digital hydraulic pressure regulator consists of a series of valves connected in parallel, which have only ON / OFF functions; So are simple ON / OFF switching valves that allow or interrupt a flow and can be consistently referred to in this application as valves. The valves are all connected to a common supply line on the one hand and to a common output line on the other hand. The valves themselves may be conventional solenoid valves, i. Be valves with electromagnetic drive. Of course, other forms of drive can be chosen.

By connecting or installing throttle elements or by the valves themselves, it is ensured that the valves have different flow cross-sections and thus different flows when they are open; a throttle element together with a valve forms a valve device. For example, if four Valves are provided, the flow rates Q in the individual, each of the associated valve selectively releasable flow cross-sections 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 mathematical models by a computer, a very rapid and precise pressure adjustment in the output line or in the actuator connected thereto can now be achieved. This is achieved by replacing the analogue control curve of the initially described proportional control valve with a digitally generated (approximate) control curve. Due to the omission of non-linearities and / or hysteresis of the analogue proportional valve, this curve can be a step-like approximated straight line which allows a control point to approach a control point quickly and (virtually) free of overshoot.

Another advantage of the digital hydraulic control is that the valves are either open or closed, i. To maintain a desired pressure in a closed (and unchanged) system, the valves are simply closed and there are no internal leakage flows. This is a clear difference to the conventional proportional valve, which is always traversed 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 or shorter, which saves energy.

It may happen during operation of a digital hydraulic control, as described above, occur that foreign matter in the valves and / or in the common lines, which may interfere with a trouble operation of the scheme disturbing. Among other things, such foreign bodies can enter the system during maintenance-related replacement of one or more of the valves. As a foreign body and air or air bubbles is referred to, which may occur at the first commissioning of such a digital hydraulic system in the system. Foreign objects of this type must be removed or rinsed out of the system for error-free operation of the system.

This object is achieved with a method for removing foreign matter from a digital hydraulic pressure regulator of a hydraulic system, having the features and method steps of claim 1.

According to the invention, a method for removing foreign substances from a digital hydraulic pressure regulator of a hydraulic system, in particular for a machine for producing a fibrous web, is proposed. The pressure regulator has two pressure regulator sections, which can be connected to one another, for example, by an overflow valve and each of which has two valve banks. In each of the valve banks, a plurality of individually switchable valve means is provided, each having a different flow cross-section. Preferably, the valve means of each valve bank have stepwise mutually different flow cross-sections, ie, a flow cross-section of a valve means of a valve bank with respect to a flow cross section of another valve means the same valve bank to a predetermined amount larger or smaller. The valve means are connected in parallel within a valve bank so as to form a parallel arrangement within a valve bank. A valve bank of each pressure regulator section may connect a supply line for supplying the digital hydraulic pressure regulator with a pressurized working fluid, such as hydraulic oil and the like, with a regulator output line. The other valve bank of the same pressure regulator section can connect the regulator outlet line with a drain line for discharging the working fluid from the pressure regulator.

The method according to the invention has a step of connecting the two pressure regulator sections, a step of opening the valve device with the largest flow cross section of the supply line side valve bank of a pressure regulator section, a step of opening the valve device with the largest flow cross section of the drain line side valve bank of the other pressure regulator section and a step of Rinse the open flow path through the pressure regulator with the working fluid, while the remaining valve means are closed.

In the method described above, therefore, the longest possible flow path is opened and rinsed by the pressure regulator with the largest possible flow cross-section, in order thereby to provide, among other things. To be able to flush out as much foreign bodies as possible from the pressure regulator.

In order to be able to free further parts of the pressure regulator from foreign bodies, the method according to the invention furthermore has a step of opening the valve device with the next-smaller flow cross section of the valve Supply line side valve bank of a pressure regulator section, a step of opening the valve means with the next smaller flow cross section of the drain line side valve bank of the other pressure regulator section and a step of purging the open flow path through the pressure regulator with the working fluid, while the remaining valve means are closed.

The above-mentioned steps are preferably repeated until all valve means of the supply-line-side valve bank of the one pressure regulator section and all valve means of the drain-line-side valve bank of the other pressure regulator section are flushed once with the working fluid and thereby freed from foreign bodies.

In order to free further parts of the pressure regulator from foreign bodies, the method described so far may also include a step of opening the valve device with the largest flow cross section of the supply line side valve bank of the other pressure regulator section, a step of opening the valve device with the largest flow cross section of the drain line side valve bank of a pressure regulator section and a step of purging the opened flow path through the pressure regulator with the working fluid while the remaining valve means are closed.

In order to also flush the not yet flushed valves of the pressure regulator, the method may further include a step of opening the valve means with the next smaller flow cross section of the supply line side valve bank of the other pressure regulator section, a step of opening the Valve means having the next smaller flow cross section of the drain line side valve bank of a pressure regulator section and a step of purging the open flow path through the pressure regulator with the working fluid, while the remaining valve means are closed.

The above-mentioned steps are preferably repeated until all the valve means of the supply-line-side valve bank of the other pressure regulator portion and all the valve means of the drain-line-side valve bank of the one pressure regulator portion are purged. With the method according to the invention, which has all the previously described steps, it is possible to flush all valve devices and all lines connecting them with the working fluid in order to remove all foreign substances from the digital hydraulic pressure regulator.

The pressurized working fluid according to the inventive method is preferably stored in a pressure accumulator prior to rinsing. It is further preferable that the working fluid is pressurized by a pump.

The method according to the invention preferably further comprises a step of collecting the working fluid after the step of purging in a tank for storing pressureless working fluid.

• Fig. 1 einen Abschnitt eines Hydrauliksystems mit einem Druckspeicher, einem digitalhydraulischen Druckregler und einem hydraulischen Differentialzylinder in einem schematischen Schaltbild;
• Fig. 2 das in Fig. 1 gezeigte Schaltbild, bei dem ein geöffneter Strömungsweg zum Spülen des in Fig. 1 gezeigten Druckreglers bei einer bestimmten Schaltung von Ventilen des Druckreglers gezeigt ist;
• Fig. 3 das in Fig. 1 gezeigte Schaltbild, bei dem ein Strömungsweg zum Entlüften eines Teils des in Fig. 1 gezeigten Druckreglers bei einer bestimmten Schaltung von Ventilen des Druckreglers gezeigt ist; und
• Fig. 4 das in Fig. 1 gezeigte Schaltbild, bei dem ein Strömungsweg zum Entlüften eines anderen Teils des in Fig. 1 gezeigten Druckreglers bei einer bestimmten Schaltung von Ventilen des Druckreglers gezeigt ist.

The invention will be explained below with reference to various aspects with reference to exemplary embodiments with reference to the drawings. It shows:

• Fig. 1 a section of a hydraulic system with a pressure accumulator, a digital hydraulic pressure regulator and a hydraulic differential cylinder in a schematic diagram;
• Fig. 2 this in Fig. 1 shown circuit diagram in which an opened flow path for rinsing the in Fig. 1 shown pressure regulator is shown in a particular circuit of valves of the pressure regulator;
• Fig. 3 this in Fig. 1 shown circuit diagram in which a flow path for venting a portion of in Fig. 1 shown pressure regulator is shown in a particular circuit of valves of the pressure regulator; and
• Fig. 4 this in Fig. 1 shown circuit diagram in which a flow path for venting another part of in Fig. 1 shown pressure regulator is shown in a particular circuit of valves of the pressure regulator.

In the following description of the figures, identical or functionally identical elements are designated by the same reference numerals, so that the general functional description is made only with reference to a figure and then referred to it. Further, if in the following text of a pressure regulator is mentioned, this is, unless otherwise stated, a digital hydraulic pressure regulator, which operates using the explained at the beginning of the description of the digital hydraulic principle.

Fig. 1 shows a portion of a hydraulic system with a pressure accumulator 11, a digital hydraulic pressure regulator 4 and a hydraulic differential cylinder 3 in a schematic diagram. One Supply section 1 with a pump pressure accumulator 11, a pump 16 and a tank 20 supplies the pressure regulator 4 with a pressurized working fluid. The pressure regulator 4 has two pressure regulator sections 41, 42 for operating a differential cylinder 3. Sensors 19 detect by means of output lines 413, 423 the pressure in the two pressure chambers 31 and 34 of the differential cylinder 3, which are separated by a piston 33 with a piston rod 36. The pressure in the rod-side pressure chamber 31 acts on the rod-side piston surface 32, while the pressure in the piston-side pressure chamber 34 presses on the piston surface 35. With the pressure regulator sections 41 and 42, the filling amount and pressure in the two pressure chambers 31 and 34 can be adjusted so that the piston rod 36 in the desired position and with the desired force with a machine element connected thereto (not shown) cooperates. Each pressure regulator section 41, 42 is connected to a supply line 43, to a respective output line 413, 423, and to a respective drain line 414, 424. Furthermore, each pressure regulator section 41, 42 has a supply line side valve bank 411, 421 and a drain line side valve bank 412, 422. In this case, depending on whether valves of the banks are open or closed, the supply-side valve bank 411, 421 connect the supply line 43 with the respective output line 413, 423. Similarly, the drain line side valve bank 412, 422 may connect the respective output line 413, 423 to the respective drain line 414, 424.

The pressure in the pressure supply 1, from which the cylinder 3 is to be controlled, is measured by means of pressure sensor 14 and, based thereon, the target pressure in the pressure chambers 31 and 34 is set. At 45 is one Overflow valve referred to, which allows a connection of the two pressure chambers 31 and 34 optionally. The function of this spill valve 45, which can be switched to passage, separates the regulator sections 41, 42 and the pressure chambers 31, 34 from each other in the closed state. When the spill valve 45 opens, the two pressure chambers are connected or shorted together. As a rule, there is a load or force on the piston rod which tends to push the piston rod into the cylinder. If now the piston rod of the load to be drawn into the cylinder following, as occurs for example when opening a roll gap, the overflow valve 45 is opened and the control valves of the piston rod side controller section remain closed. The working fluid thus flows partly into the piston-side pressure chamber 31 and partly into the tank (not shown). The outflow into the tank is controlled by the cylinder-side regulator section 42 and thus controls the lowering speed of the piston rod.

Fig. 2 shows a flow path opened by the method according to the invention, in which the pressurized working fluid from the pump 16 via the supply line 43 through the valve with the largest flow cross-section, in this example with a flow cross-sectional diameter of 1.5 mm, the supply line side valve bank 421 of the pressure regulator section 42nd is conveyed to the output line 423. Since the output line 423 of the pressure regulator section 42 communicates via the opened spill valve 45 with the outlet line 413 of the pressure regulator section 41, the working fluid becomes the output line 413 and further through the valve having the largest flow area, in this example a Flow cross-sectional diameter of 1.5 mm, the drain line side valve bank 412 of the pressure regulator section 41 conveyed into the tank 20 and collected there. In this procedure, a flushing of the longest flow path is achieved with the largest possible flow cross-section of the pressure regulator 4, wherein in the flushed parts of the pressure regulator 4 existing foreign matter flushed out and thus removed from the pressure regulator 4.

A circuit of the pressure regulator 4 for venting a first part of the pressure regulator 4 is in Fig. 3 shown. As it is in Fig. 2 shown and described above, first the longest flow path is flushed through with the largest possible flow cross-section of the pressure regulator 4. Subsequently, at the in Fig. 3 As shown, the valve with the next smaller flow area in the supply line side valve bank 421 of the pressure regulator section 42 and the valve with the next smaller flow area of the drain line side valve bank 412 of the pressure regulator section 41 are opened. Then, the working fluid is purged through the flow path formed thereby. The valve with the next smaller flow cross section is located in the valve arrangement shown in each of the valve banks next to the previously opened valve with the largest possible flow cross-section. In a next process step, the valve with the next smallest flow cross-section in each of the active valve banks is opened and the flow path opened thereby purged, etc. These steps are repeated until all the valves of the two in Fig. 3 shown active valve banks are flushed and vented.

A circuit of the pressure regulator 4 for venting the remaining part of the pressure regulator 4 is in Fig. 4 shown. Analogous to Fig. 3 First, the longest flow path with the largest possible flow cross-section of the pressure regulator 4 is purged by the pressurized working fluid from the pump 16 via the supply line 43 through the valve with the largest flow cross section of the supply line side valve bank 422 of the pressure regulator section 41 is conveyed into the output line 413. Since the exit passage 413 of the pressure regulator section 41 communicates with the exit passage 423 of the pressure regulator section 42 via the opened relief valve 45, the working fluid becomes the exit passage 423 and further through the valve having the largest flow area of the drain passage side valve bank 422 of the pressure regulator section 42 into the tank 20 promoted and collected there. Subsequently, at the in Fig. 4 1, the valve with the next smaller flow area in the supply line side valve bank 411 of the pressure regulator section 41 and the valve with the next smaller flow area of the drain line side valve bank 422 of the pressure regulator section 42 are opened. Then, the working fluid is purged through the flow path formed thereby. The valve with the next smaller flow cross section is located in the valve arrangement shown in each of the valve banks next to the previously opened valve with the largest possible flow cross-section. In a next method step, the valve with the next smallest flow cross-section in each of the active valve banks is opened and the flow path opened thereby purged, etc. These steps are repeated until all valves of the pressure regulator 4 are flushed and vented. As an alternative to the structure of the pressure regulator 4 described above, it is not absolutely necessary for the valves of a valve bank with a descending flow cross section to be arranged next to one another. It would also be conceivable to provide an arbitrary arrangement of the valves in each valve bank.

Claims (10)

1. A method for removing foreign matter from a pipeline of a hydraulic system, in particular for a machine for producing a fibrous web,
   wherein a digital hydraulic pressure regulator (4) has two pressure regulators portions (41, 42) which are connectable to each other and each of which has two valve banks (411, 412, 421, 422) in each of which a plurality of individually switchable valve means (5) is provided, each having a different flow cross-section and which are connected in parallel within a valve bank, and the one valve bank (411, 421) of which is adapted to connect a supply line (43) to a controller output line (413, 423) and the other valve bank (412, 422) is adapted to connect the controller output line (413, 423) to a drain line (414, 424), and
   wherein the method comprises the steps of:

   connecting the two pressure regulator portions (41, 42),

   opening the valve means having the largest flow cross-section of the supply-line-side valve bank (421) of the one pressure regulator portion (42),

   opening the valve means having the largest flow cross-section of the drain-line-side valve bank (412) of the other pressure regulator portion (41), and

   purging the opened flow path through the pressure regulator (4) with a pressurized working fluid, while the remaining valve means are closed.
2. The method according to claim 1, wherein the method further comprises the steps of:

   opening the valve means having the next smaller flow cross-section of the supply-line-side valve bank (421) of the one pressure regulator portion (42),

   opening the valve means having the next smaller flow cross-section of the drain-line-side valve bank (412) of the other pressure regulator portion (41), and

   purging the opened flow path through the pressure regulator (4) with the working fluid, while the remaining valve means are closed.
3. The method according to claim 2, wherein the steps set forth in claim 2 are repeated until all the valve means (5) of the supply-line-side valve bank (421) of the one pressure regulator portion (42) and all the valve means of the drain-line-side valve bank (412) of the other pressure regulator portion (41) are purged.
4. The method according to claim 2 or 3, wherein the method further comprises the steps of:

   opening the valve means having the largest flow cross-section of the supply-line-side valve bank (411) of the other pressure regulator portion (41),

   opening the valve means having the largest flow cross-section of the discharge-line-side valve bank (422) of the one pressure regulator portion (42), and

   purging the opened flow path through the pressure regulator (4) with the working fluid, while the remaining valve means are closed.
5. The method according to claim 4, wherein the method further comprises the steps of:

   opening the valve means having the next smaller flow cross-section of the supply-line-side valve bank (411) of the other pressure regulator portion (41),

   opening the valve means having the next smaller flow cross-section of the drain-line-side valve bank (422) of the one pressure regulator portion (42), and

   purging the opened flow path through the pressure regulator (4) with the working fluid, while the other valve means are closed.
6. The method according to claim 5, wherein the steps mentioned in claim 5 are repeated until all the valve means of the supply-line-side valve bank (411) of the other pressure regulator portion (41) and all the valve means of the drain-line-side valve bank (422) of the one pressure regulator portion (42) are purged.
7. The method according to any one of the preceding claims, wherein the valve means (5) of each said valve bank have flow cross-sections which are stepwise different from each other.
8. The method according to any one of the preceding claims, wherein the working fluid is stored in a pressure accumulator (11) prior to purging.
9. The method according to any one of the preceding claims, wherein the working fluid is pressurized by a pump (16).
10. The method according to any one of the preceding claims, wherein the method further comprises the step of:

    collecting the working fluid, after the step of purging, in a tank (20) for storing unpressurized working fluid.

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