DE102014202558A1 - DIGITAL HYDRAULIC PRESSURE REGULATOR AND METHOD OF CHECKING A DIGITAL HYDRAULIC PRESSURE REGULATOR - Google Patents

Abstract

A digital hydraulic pressure regulator (2, 4) according to the invention has at least one digitally controllable valve bank (A-T, P-A, P-B, B-T) and a malfunction determining device with a flow meter (12, 14). The malfunction determining means is arranged to determine that a malfunction is in the form of a partially or fully opened valve when an instruction to close all the valves of the valve bank (AT, PA, PB, BT) has been issued upon application of a supply pressure to the fluid system, and a flow of the fluid measured by the flow meter (12, 14) is present in the fluid system.

Description

The invention relates to a digital hydraulic pressure regulator and a verification method of a digital hydraulic pressure regulator.

In paper machines, working fluid (for example hydraulic oil, air, water, different gases or emulsions or mixtures of these fluids) 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.

In general, a working fluid is used, which is pressurized by a pump. The introduction of the pressurized working fluid into a hydraulic actuator, such as a fluid cylinder or a fluid motor (eg, hydraulic motor), is more recently controlled by digitally controlled valves that form a pressure regulator.

The operation of a digital pressure regulator is for example in the magazine "Fluid", No. 7-8, 2008, pages 12-13 is described in more detail and is summarized below again very briefly:
A digitally controlled pressure regulator consists in the simple case of a series of parallel-connected, digitally controlled valves, which have only an open / close function, and in the idle state (close-to-off state) are sealed. So there are simple on-off switching valves that allow or interrupt a flow and can be consistently referred to as valves in this application. The valves are all connected to a common supply line on the one hand and to a common output line on the other. The valves themselves may be conventional solenoid valves, ie valves with electromagnetic drive. Of course, other forms of drive can be chosen.

These valves can have different flow rates, for example by connecting or installing throttle elements. Preferably, the valves are in a series ratio of 1: 2: 4: 8 ... to each other, with the length of the row determined according to the number of valves.

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 a conventional 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. In addition, changes in pressure levels are possible within extremely short periods of time.

One in 1 exemplified, digital hydraulic actuator four valve banks are assigned, each having an equal number of valves and / or throttles. A schematic representation of such a hydraulic system, which can be used for example on a paper machine, is the 1 refer to. The valve banks are also referred to as digital flow control unit and are therefore in the 1 provided with the abbreviation DFCU.

The hydraulic system of 1 consists of one by means of two actuators 1 . 5 sliding cylinder 3 that is against a fixed cylinder 7 to lead is. The actuators 1 . 5 have a first chamber A and a second chamber B on. If the pressure in the respective chamber A is increased in relation to the pressure in the respective chamber B, a feed movement of the movable cylinder occurs 3 against the solid cylinder 7 , In contrast, there is a reset movement when the pressure in the respective chamber B is increased. Each actuator 1 . 5 is a digital hydraulic controller 2 . 4 assigned, each having the same structure.

To achieve the feed movement, the valves of the valve banks PA in the two digital hydraulic controllers 2 . 4 connected so that a connection between a pump P for generating a hydraulic pressure in a working fluid and the chamber A in the actuators 1 . 5 is made. At the same time, the valves of the valve banks BT in the digital hydraulic controllers are switched to connect to the hydraulic fluid between the respective chambers B and a tank T produce. The switching of the valves creates a certain flow for the hydraulic fluid.

For a reset movement accordingly the valve banks PB and AT in the two digital hydraulic controllers 2 . 4 switched so that a connection between the pump P and the chamber B is made in the actuators.

Although this in the 1 not shown, a valve bank may also be provided between the first chamber A and the second chamber B, to connect these two chambers A and B directly to each other.

However, in order to accurately adjust pressure in a fluid system with digitally controlled valves, the flow rates of the valves must be known, i.e., the system must be calibrated.

For this purpose, the document discloses DE 10 2010 042 780 A1 a fluid system of a machine for producing a fibrous web with digitally controlled valves, in which a calibration value of the valves can be determined. In addition, a corresponding calibration value determination method is disclosed.

From the publication WO 2010/136071 A1 For example, a method for controlling a digital hydraulic control device is known. As part of a test sequence, calibration of individual valves is accomplished by alternately opening two of the valves, one connecting a supply line to an output line and the other connecting the output line to a drain line, and calculating and setting calibration values for the individual valves accordingly detected flow and pressure values in the controller, and / or a condition monitoring, in which each of the valves is switched sequentially and in which a valve opening condition of the individual valve is inferred from the detected flow and pressure values in response to the valve switching.

Incidentally, it is possible to recognize that valves are defective when they are in the closed state. This detection is due to the different pressure values, that is, it is detected a difference between the target and actual pressure and thus accurately determines the stuck in the closed state, faulty valve.

• – In geöffneter oder teilweise geöffneter Stellung steckende Ventile werden nicht erkannt;
• – in geöffneter oder teilweise geöffneter Stellung steckende Ventile stören den voranstehend beschriebenen Erkennungsvorgang, da diese Ventile den vorliegenden Druck in dem System verfälschen;
• – die vorgesehene Funktion des digitalhydraulischen Hydrauliksystems kann unter Umständen erreicht werden, falls die Menge des durch die in geöffneter oder teilweise geöffneter Stellung stecken gebliebene Ventile strömenden Fluids vergleichsweise hoch ist.

However, if a valve gets stuck in a partially or fully opened state, recognition of this error according to the known recognition method is not possible. This can lead to the following problems:

• - Valves stuck in open or partially open position are not recognized;
• - Valves stuck in the open or partially open position interfere with the above-described detection process, as these valves distort the existing pressure in the system;
• - The proposed function of the digital hydraulic hydraulic system can be achieved under certain circumstances, if the amount of fluid flowing through the valves stuck in the open or partially open position is relatively high.

It is the object of the invention to provide a digital hydraulic pressure regulator and a verification method of a digital hydraulic pressure regulator, with which it can be recognized that faulty, partially open or fully open state valves are present.

The object of the invention is achieved by a digital hydraulic pressure regulator according to claim 1 and a verification method according to claim 5. Advantageous embodiments are set forth in the dependent claims.

A digital hydraulic pressure regulator according to the invention has at least one digitally controllable valves valve bank and a malfunction determining device with a flow meter. The malfunction determination device is designed to determine that a malfunction in the form of a partially or fully opened valve (hereinafter also referred to as faulty closing valve) is present when an instruction to close all valves of the valve bank was issued upon application of a supply pressure to the fluid system , and a flow of the fluid measured by the flow meter is present in the fluid system.

For this purpose, an instruction is given to close all valves of the valve bank. In addition, the hydraulic system is pressurized. Since the valves in the closed state prevent any flow in the region of the valve bank, a faulty closing valve can be detected immediately, even if a flow of hydraulic fluid is detected.

The malfunction determination device can advantageously have a calculation device which calculates a characteristic flow coefficient on the basis of the measured flow.

With appropriate prior calibration, based on the detected flow, the valve closing by the faulty valve can resulting pressure increase can be determined. Thus, by appropriate control of the remaining valves may even be made a balance of unintentional pressure increase.

Advantageously, the malfunction determining means may also identify a malfunctioning valve or valves by comparing the characteristic flow coefficient with known flow coefficients of the individual valves of the valve bank with the valves to be closed.

Since the respective flow coefficients of the individual valves of the valve bank are known, a faulty closing valve can be detected immediately if the characteristic flow coefficient deviates.

Advantageously, in the case of a plurality of valve banks for determining malfunction, an instruction may be issued to close all the valves of one valve bank and to supply the fluid system with the supply pressure while leaving all valves of the remaining valve banks open. This means that one valve bank after the other is checked for malfunctioning valves.

• – Schließen sämtlicher Ventile der Ventilbank,
• – Beaufschlagen des digitalhydraulischen Druckreglers mit einem Zufuhrdruck,
• – Messen einer Strömung an dem digitalhydraulischen Druckregler,

Bestimmen, dass eine Fehlfunktion in Form eines teilweise oder vollständig geöffneten Ventils vorliegt, wenn eine Strömung vorhanden ist. An inventive verification method of a digital hydraulic pressure regulator with at least one digitally controllable valve having valve bank has the following steps:

• Closing all valves of the valve bank,
• Pressurizing the digital hydraulic pressure regulator with a supply pressure,
• Measuring a flow at the digital hydraulic pressure regulator,

Determining that a malfunction is in the form of a partially or fully opened valve when there is a flow.

Advantageously, a characteristic flow coefficient can additionally be calculated on the basis of the existing flow.

In addition, advantageously, one or more malfunctioning valves may be identified by comparing the characteristic flow coefficient with known flow coefficients of the individual valves of the valve bank with the valves to be closed.

If there are a plurality of valve banks, these can be checked one at a time by closing all the valves of the valve bank to be checked, while leaving all valves of the remaining valve banks open, and applying the supply pressure to the digital hydraulic pressure regulator.

Advantageously, according to the checking method, each individual valve of the valve bank to be checked can be opened and closed again one after the other. In this case, a faulty valve can be detected when a difference between the characteristic flow coefficient before opening the valve and the characteristic open-current flow coefficient is smaller than the known open-current flow coefficient.

Based on the characteristic flow coefficient, only a conditional statement is possibly possible, which individual valve has exactly the malfunction of a partially or fully opened valve. In the course of the calibration mentioned above, a characteristic flow coefficient of the valve is determined for each individual valve in the open state.

If a faultless valve is opened in the course of the check, the pressure in the hydraulic system changes correspondingly, that is, the characteristic flow coefficient of the flow in the hydraulic system increases by the characteristic flow coefficient of the valve being checked. However, if the change does not occur at the expected level, it can be determined that the valve being tested is a plug-in valve. If there is no change in the characteristic flow coefficient at all, the valve under test is a fully open-state valve.

The verification method according to the invention can be combined with a method for checking for incorrectly closed valves. This makes it advantageous to identify not only faulty closing valves, but also those valves that have stuck in the closed state and can not be opened.

The 1 shows by way of example a hydraulic system to which an embodiment of the invention will be described.

Since that in 1 shown hydraulic system has already been described in the introduction, a repetition is avoided at this point.

To check for malfunctioning valves, the hydraulic system is supplied by the pump P with a supply pressure and issued an instruction, all valves from one of the four valve banks AT, PA, PB, BT one of the two digital hydraulic controller 2 . 4 close.

In the example described, first all the valves of the valve bank AT of the digital hydraulic controller 2 closed due to a corresponding issued instruction. If there is no fault of one of the valves of the valve bank AT, ie all valves of the valve bank AT are actually completely closed, hydraulic fluid can no longer flow out of the chamber A into the tank T. Consequently, any flow through the fully opened valve bank PA into the chamber A is also prevented. The term "fully open valve bank" is understood to mean that all valves of the valve bank are fully open.

In addition, no hydraulic fluid can be supplied through the fully open valve bank P-B in the chamber B, since their volume can not be increased for lack of outflow from the chamber A. Also, a leakage of the hydraulic fluid from the chamber B through the fully open valve bank B-T is not possible.

Thus, in the field of digital hydraulic controller 2 a flow only occur when one or more of the valves of the checked valve bank 2 is not completely closed, but is in fully or partially open position. If this is the case, one on the digital hydraulic controller detects 2 provided volumetric flow meter 12 a flow. That in the 1 Volumetric flow meter represented by a symbol 12 corresponds to a flow meter according to the invention. It should be noted, however, that any suitable flow meter can be used as flow meter, such as electromagnetic flow meter, ultrasonic flow meter or acoustic flow meter.

If through the volumetric flow meter 12 no flow is detected, a determination is made that the valve bank AT is faultless. Thereafter, the next valve bank PA is checked in the same way.

If through the volumetric flow meter 12 a flow is detected, then a characteristic flow coefficient is calculated based on the detected flow. A comparison of this characteristic flow coefficient with previously determined flow coefficients of the individual valves of the valve bank 2 allows accurate determination of the magnitude of the pressure loss through the faulty valve (s) that are not fully closing.

This makes it possible to determine whether one of the valves is in the fully opened state or partially open state. In addition, appropriate countermeasures such as e.g. an increase in the system pressure corresponding to the pressure loss through the faulty valve (s) or replacement of the affected valve or valve bank is initiated. In addition, it is advantageously possible to consider the result of the check in addition to a check for stuck in the closed state valves.

As the volumetric flow meter 12 on the digital hydraulic controller 2 is provided, it is only capable of one in the field of digital hydraulic controller 2 to detect existing flow, if this occurs in the case of a non-closing valve of the checked valve bank AT. Thus, it is irrelevant whether the valves of the valve banks in the 1 represented second digital hydraulic controller 4 open or closed, as one in this digital hydraulic controller 4 possibly occurring flow from the volumetric flow meter 12 on the digital hydraulic controller 2 can not be detected.

After checking the valve bank A-T, the remaining valve banks P-A, P-B and B-T are checked one after the other in the same way.

In a hydraulic system with several digital hydraulic controllers 2 . 4 like the one in the 1 can be shown checking the individual valve banks in each digital hydraulic controller 2 . 4 , even performed at the same time, because in each digital hydraulic controller 2 . 4 a volumetric flow meter 12 . 14 is provided.

The invention thus advantageously enables automatic detection of a fault in the form of a non-closing valve. By combining the invention with a method for checking valves in the closed state, all possible malfunctions of a digital hydraulic valve can be detected. These can be a plug in closed, partially open or completely open state.

In a digital hydraulic system such as the in 1 shown are the regulation of the movement of the cylinder 3 based on measurement results of linear sensors and the regulation of the pressure in a chamber A, B of the cylinder 1 . 5 based on measurement results of pressure sensors on the chamber walls in the cylinder 1 . 5 are provided. For example, the linear sensors are used to accurately determine the position of the piston in the actuator 1 . 5 , But they can also be provided at another suitable location, as long as the position of the cylinder 3 is determined.

However, it is advantageously possible if there is a failure of one of the pressure sensors to calculate the chamber pressure based on the measurement result of one of the linear sensors. Therefore, in a case where a pressure sensor fails, the control of the chamber pressure may alternatively be made via the linear sensor without the need to immediately shut down the system to replace the pressure sensor.

It is also possible, in case of failure of a linear sensor, which serves to accurately determine the piston position, the piston position based on a measurement result of the pressure sensor in the chamber A, B of the cylinder 1 . 5 to calculate.

In order to enable the above-described replacement of the linear sensor by a pressure sensor or vice versa, a mathematical model is provided with which it is possible to calculate the pressure in each of the chambers A, B based on a position of the piston output by the linear sensor. In addition, with the mathematical model, it is possible to calculate the piston position from a pressure value measured by the pressure sensor in the chamber A, B.

Thus, despite failure of a pressure sensor in the hydraulic system, by using a linear sensor by taking the mathematical model, the pressure of the hydraulic fluid in the chambers A, B can be determined with sufficient accuracy. It is also possible in case of failure of a linear sensor, by using a pressure sensor to pull the mathematical model, the piston position and thus a movement of the cylinder 3 be determined with sufficient accuracy.

The invention was based on an embodiment based on the 1 but is not to be construed in a manner limited by the embodiment, but only defined by the scope of the appended claims.

In particular, it should be noted that the number of digital hydraulic controller is by no means limited. Also, the number of valve banks in a digital hydraulic controller is not limited to four. For example, the embodiment according to FIG could still be extended by a valve bank A-B, which is associated with a direct connection of the two chambers A and B. Such a valve bank A-B can then be checked in the course of a check of the digital hydraulic controller, as described above. The number of valves per valve bank is arbitrary.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102010042780 A1 [0015]
• WO 2010/136071 A1 [0016]

Cited non-patent literature

• "Fluid", No. 7-8, 2008, pages 12-13 [0004]

Claims (10)

Digital hydraulic pressure regulator ( 2 . 4 ) with at least one digitally controllable valves having valve bank (AT, PA, PB, BT), and a malfunction determining device with a flow meter ( 12 . 14 ), wherein the malfunction determining means is arranged to determine that a malfunction is in the form of a partially or fully opened valve when an instruction to close all valves of the valve bank (AT, PA, PB, BT) is issued upon application of the fluid system with a supply pressure was, and one through the flow meter ( 12 . 14 ) measured flow of the fluid is present in the fluid system. Digital hydraulic pressure regulator ( 2 . 4 ) according to claim 1, wherein said malfunction determining means comprises calculating means which calculates a characteristic flow coefficient based on the measured flow. A digital hydraulic pressure regulator according to claim 2, wherein the malfunction determining means identifies one or more malfunctioning valves by comparing the characteristic flow coefficient with known flow coefficients of the individual valves of the valve bank (A-T, P-A, P-B, B-T) with the valves to be closed. Digital hydraulic pressure regulator ( 2 . 4 ) according to one of claims 1 to 3, wherein the digital hydraulic pressure regulator ( 2 . 4 ) has a plurality of valve banks (AT, PA, PB, BT), and wherein an instruction is issued for malfunction determination to close all the valves of one valve bank (AT) and to supply the fluid system with the supply pressure, while all valves of the remaining valve banks ( PA, PB, BT) remain open. Verification procedure of a digital hydraulic pressure regulator ( 2 . 4 ) having at least one digitally controllable valve bank (AT, PA, PB, BT), the method comprising the following steps: - closing all valves of the valve bank (AT, PA, PB, BT), - applying the digital hydraulic pressure regulator ( 2 . 4 ) with a supply pressure, - measuring a flow at the digital hydraulic pressure regulator ( 2 . 4 ), - determining that a malfunction is in the form of a partially or fully opened valve when there is a flow. The verification method according to claim 5, wherein in addition, based on the existing flow, a characteristic flow coefficient is calculated. A check method according to claim 6, wherein one or more malfunctioning valves are identified by comparing the characteristic flow coefficient with known flow coefficients of the individual valves of the valve bank (A-T, P-A, P-B, B-T) with the valves to be closed. A check method according to any one of claims 5 to 7, wherein there is a plurality of valve banks (AT, PA, PB, BT) which are checked one at a time by closing all the valves of the valve bank (AT) to be checked, while all the valves of the others Valve banks (PA, PB, BT) remain open and the digital hydraulic pressure regulator ( 2 . 4 ) is applied to the supply pressure. A check method according to any one of claims 5 to 8, wherein each individual valve of the valve bank (AT) to be checked is opened and closed one after another and a faulty valve is detected if a difference between the characteristic flow coefficient before opening the valve and the characteristic flow coefficient when the valve is open is smaller than the known flow coefficient of the open valve. A verification method according to any one of claims 5 to 9, combined with a method of checking for incorrectly closed valves.

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