AT14640U1 - DIGITAL HYDRAULIC PRESSURE REGULATOR AND METHOD OF CHECKING A DIGITAL HYDRAULIC PRESSURE REGULATOR - Google Patents

Abstract

Digital hydraulic pressure regulator (2, 4) with at least one digitally controllable valves having valve bank (A-T, P-A, P-B, B-T) and a malfunction determining device with a volumetric flow meter (12, 14). A check method for determining a malfunction of the pressure regulator (2, 4) comprises the following steps: closing all valves of the valve bank (AT, PA, PB, BT), pressurizing the digital hydraulic pressure regulator (2, 4) with a supply pressure, measuring a volumetric flow the digital hydraulic pressure regulator (2, 4) by means of the volumetric flow meter (12, 14), determining that there is a malfunction in the form of a partially or fully opened valve when a flow is present.

Description

DIGITAL HYDRAULIC PRESSURE REGULATOR AND VERIFICATION METHOD OF A DIGITAL HYDRAULIC PRESSURE REGULATOR

Description [0001] 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, various 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 adjusted and applied 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 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 described, for example, in the journal " Fluid ", No. 7-8, 2008, pages 12-13 and is again briefly summarized below: [0005] In the simple case, a digitally controlled pressure regulator consists of a series of parallel-connected, digitally controlled valves which only have an open / close function. and in the rest state (ZU state) are tight. 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 can be conventional solenoid valves, i. H. Be valves with electromagnetic drive. Of course, other forms of drive may be chosen.

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

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 can now be achieved in the output line or in the actuator connected thereto. This is achieved by replacing the analogue control curve of a conventional proportional control valve with a digitally generated (approximate) control curve. This curve, due to the elimination of non-linearities and / or hysteresis of the analog proportional valve, can be a step-like straight line that allows a control point to approach a control point quickly and (nearly) free of overshoot.

Another advantage of the digital hydraulic control is that the valves are either open or closed, i. E. 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 from 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 permits the hydraulic pumps to be operated less often or shorter, which saves energy. In addition, changes in the pressure level within extremely short Zeit¬räumen possible.

A digital hydraulic actuator, shown by way of example in FIG. 1, has four valve banks, 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 shown in FIG. The valve banks are also referred to as a digital flow control unit and are therefore provided with the abbreviation DFCU in FIG.

The hydraulic system of Fig. 1 consists of a means of two actuators 1, 5 ver¬ pushable cylinder 3, which is to be guided against a fixed cylinder 7. The actuators 1, 5 have a first chamber A and a second chamber B. If the pressure in the respective chamber A is increased in relation to the pressure in the respective chamber B, there is a feed movement of the movable cylinder 3 against the fixed cylinder 7. In contrast, there is a reset movement when the pressure in the respective Chamber Berhöht is. Each actuator 1, 5 is a digital hydraulic controller 2, 4 assigned, each having the same structure.

In order to achieve the feed movement, the valves of the valve banks PA in the two digital hydraulic regulators 2, 4 are switched 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 B-T are switched in digital hydraulic controllers to establish communication between the respective chambers B and a tank T for the hydraulic fluid. The switching of the valves creates a certain flow for the hydraulic fluid.

Accordingly, for a return movement, the valve banks P-B and A-T in the two digital hydraulic controllers 2, 4 are switched so that a connection between the pump P and the chamber B is made in the actuators.

Although not shown in Fig. 1, 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 set 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 publication DE 10 2010 042 780 A1 discloses 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 document WO 2010/136071 AI a method for controlling a digital hydraulic control device is known. In the course of a test sequence, individual valves are calibrated 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 discharge line, and calculating and setting calibration values for the individual ones Valves corresponding to sensed flow and pressure values in the controller, and / or condition monitoring in which each of the valves is sequentially switched and in which a valve opening condition of the individual valve is inferred from the sensed flow and pressure values in response to the valve switching.

Incidentally, it is possible to recognize that valves are faulty when stuck in the locked state. This recognition takes place on account of the differing pressure values, that is to say a difference between desired and actual pressures is detected and thus the faulty valve inserted in the closed state is precisely determined.

However, if a valve gets stuck in a partially or fully opened state, however, a recognition of this error according to the known Erkennungsverfah¬ren not possible. This can lead to the following problems: valves which are in the open or partially open position are not known; [0021] valves which are in the open or partially open position interfere with the recognition process described above, since these valves distort the present pressure in the system; - The intended function of the digital hydraulic hydraulic system can under

Circumstances can be achieved if the amount of fluid flowing through the valves stuck in the open or partially open position is comparatively high.

It is the object of the invention to provide a digital hydraulic pressure regulator and a Über¬prüfungsverfahren a digital hydraulic pressure regulator, with which can be detected that erroneous, located in partially open or fully open state are available Ventili¬.

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

A digital hydraulic pressure regulator according to the invention has at least one digitally controllable valve bank and a malfunction determining device with a flow meter. The malfunction determining means is adapted to designate that a malfunction in the form of a partially or fully opened valve (hereinafter also referred to as malfunctioning valve) is present when an instruction to close all the valves of the valve bank has been 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 area of the valve bank, a faulty closing valve can be detected immediately if a flow of the hydraulic fluid is nevertheless detected.

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

With appropriate previous calibration, based on the detected flow, the pressure increase resulting from the faulty closing valve can be determined. Thus, by appropriate control of the remaining valves under circumstances, even a compensation of the unintended pressure increase can be made.

Advantageously, the malfunction determination device can also identify a valve or several malfunctioning 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 malfunction determination, an instruction may be issued to close all the valves of one valve bank and to pressurize the fluid system with the supply pressure while all the valves of the remaining valve banks remain open. This means that one valve bank after the other is checked for malfunctioning valves.

An inventive method of checking a digital hydraulic pressure regulator with at least one digitally controllable valve bank comprises the following steps: - closing all valves of the valve bank, - applying the digital hydraulic pressure regulator with a supply pressure, - measuring a flow at the digital hydraulic pressure regulator, determining that there is a malfunction in the form of a partially or fully opened valve when there is a flow.

Advantageously, in addition, starting from the existing flow, a characteristic flow coefficient can be calculated.

In addition, advantageously one or more malfunctioning valves can 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 a plurality of valve banks is present, these can be individually checked one after the other by closing all valves of the valve bank to be checked, while all the valves of the remaining valve banks remain open, and the digital hydraulic pressure regulator with the Supply pressure is applied.

Advantageously, according to the verification method, each individual valve of the valve bank to be checked can be opened one after the other and closed again. 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 flow coefficient of the opened valve.

Based on the characteristic flow coefficient may be only a conditional statement 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 fault-free valve is opened in the course of the check, the pressure in the hydraulic system changes (increases) accordingly, that is, the characteristic flow coefficient of the flow in the hydraulic system increases by the characteristic Strömungskoeffi¬zienten the valve currently under review. However, if the change does not take place at the expected level, it can be determined that the valve currently being checked is a plug-in valve. If there is no change in the characteristic flow coefficient at all, the valve under test is a valve in the fully open state.

The verification method according to the invention can be combined with a method for checking for incorrectly closed valves. This advantageously makes it possible to identify not only faulty closing valves but also those valves which have become stuck in the closed state and can no longer be opened.

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

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

For checking for malfunctioning valves, the hydraulic system is supplied with a supply pressure by means of the pump P and an instruction is issued to close all the valves of one of the four valve banks A-T, P-A, P-B, B-T of one of the two digital hydraulic regulators 2, 4.

In the example described, all the valves of the valve bank A-T of the digital hydraulic regulator 2 are first closed due to a correspondingly issued instruction. If there is no fault of one of the valves of the valve bank A-T, i.e., all the valves of the valve bank A-T are actually completely closed, hydraulic fluid can no longer flow from the chamber A into the tank T. Consequently, any flow through the fully opened valve bank P-A into the chamber A is also prevented. The term "fully opened valve bank " It should be understood that all valves of the valve bank are fully opened.

In addition, no hydraulic fluid through the fully open valve bank P-Bin, the chamber B are supplied, since their volume can be increased for lack of outflow from the chamber Anicht. 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 area of the digital hydraulic controller 2, a flow only occurs when one or more of the valves of the checked valve bank (A-T) is not completely closed, but is in the fully or partially open position. If this is the case, a volume flow meter 12 provided on the digital hydraulic controller 2 detects a flow. The volume flow meter 12 shown in FIG. 1 by means of a symbol corresponds to a flow meter according to the invention. It should be noted, however, that any suitable flow meter may be used as a flow meter, such as a flowmeter. electromagnetic flowmeters, ultrasonic flowmeters or acoustic flowmeters.

When no flow is detected by the volumetric flow meter 12, it is determined that the valve bank A-T is free of errors. Thereafter, the next valve bank P-A is checked in the same way.

When a flow is detected by the volumetric flow meter 12, a characteristic flow coefficient is then calculated from the sensed flow. Comparison of this characteristic flow coefficient with pre-determined flow coefficients of the individual valves of the valve bank 2 enables accurate determination of the magnitude of pressure loss by the valve the faulty or not completely closed valve (s).

This makes it possible to determine whether one of the valves is in the fully open state or partially open state. In addition, appropriate countermeasures such as e.g. an increase in 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 take into account the result of the check in addition to a check for valves inserted in the closed state.

Since the volumetric flow meter 12 is provided on the digital hydraulic controller 2, it is only able to detect a flow existing in the area of the digital hydraulic controller 2 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 of the second digital hydraulic controller 4 shown in FIG. 1 are open or closed, since any digital hydraulic controller 4 can not detect any occurring flow from the volume flow meter 12 to the digital hydraulic controller 2.

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 having a plurality of digital hydraulic controllers 2, 4, as shown in FIG. 1, the checking of the individual valve banks in each digital hydraulic controller 2, 4 can even be carried out at the same time, since in each digital hydraulic controller 2, 4 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 of checking for closed state valves, all possible malfunctioning 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, e.g. 1, the control 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, 5th pre see are. For example, the linear sensors serve to accurately determine the position of the piston in the actuator 1, 5. However, they may also be provided at another suitable location as long as the position of the cylinder 3 is determined as a result.

Advantageously, however, it is 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 can 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 to calculate the piston position based on a measurement result of the pressure sensor in the chamber A, B of the cylinder 1.5 in case of failure of a linear sensor, which is used for accurate determination of the piston position.

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, starting from a position of the piston output by the linear sensor, the pressure in each of the chambers A, B to calculate. In addition, it is possible with the mathematical model to calculate the piston position starting from a pressure value measured in the chamber A, B by the pressure sensor.

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 while pulling the mathematical model, the piston position and thus a movement of the cylinder 3 can be determined with sufficient accuracy.

The invention has been described with reference to an embodiment based on FIG. 1, but is not interpreted in a 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 controllers is not limited. Also, the number of valve banks in a digital hydraulic controller is not limited to four. For example, the embodiment according to figure could 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.

Claims (9)

Claims 1. Digital hydraulic pressure regulator (2, 4) with at least one valve bank (AT, PA, PB, BT), which deflects digitally controllable valves, and a malfunction determining device with a volumetric flow meter (12, 14), characterized in that the malfunction determining device is designed is 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 the fluid system with a supply pressure, and one by the Volu¬menstrommessgerät (12, 14) measured flow of the fluid in the fluid system vor¬handen is. 2. Digital hydraulic pressure regulator (2, 4) according to claim 1, characterized in that the malfunction determination device has a calculation device which calculates starting from the measured volume flow a characteristic Strömungskoeffi¬ients, such as a pressure drop. 3. Digital hydraulic pressure regulator according to claim 2, characterized in that the malfunction determining means identified by comparison of the characteristic flow coefficient with known flow coefficients of the individual valves of the valve bank (A-T, P-A, P-B, B-T) one or more valves with malfunction. 4. Digital hydraulic pressure regulator (2, 4) according to one of claims 1 to 3, characterized ge indicates that the digital hydraulic pressure regulator (2, 4) has a plurality of valve banks (AT, PA, PB, BT), and wherein an instruction is issued for determining malfunction, to close all valves of a valve bank (AT) and to pressurize the fluid system with the supply pressure, while all valves of the remaining valve banks (PA, PB, BT) remain open. 5. Verification method of a digital hydraulic pressure regulator (2, 4) with at least one digitally controllable valves having valve bank (AT, PA, PB, BT), gekenn¬zeichnet that the method comprises the following steps: - Close all valves of the valve bank (AT, PA , PB, BT), - supplying the digital hydraulic pressure regulator (2, 4) with a supply pressure, - measuring a volume flow at the digital hydraulic pressure regulator (2,4), - determining that a malfunction in the form of a partially or fully opened valve exists a flow is present. 6. Verification method according to claim 5, characterized in that in addition starting from the measured volume flow, a characteristic Strömungskoeffi¬zient, such as a pressure loss is calculated. 7. A verification method according to claim 6, characterized in that 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). 8. Verification method according to one of claims 5 to 7, characterized in that a plurality of valve banks (AT, PA, PB, BT) is present, which are individually nach¬ checked by closing all the valves to be tested valve bank (AT) be while all valves of the remaining valve banks (PA, PB, BT) remain open, and the digital hydraulic pressure regulator (2, 4) is acted upon by the supply pressure. A check method according to any one of claims 5 to 8, characterized in that each individual valve of the valve bank (AT) to be checked is opened and closed one after the other and a faulty valve is detected when the magnitude of the difference between the characteristic flow coefficient before opening the valve and the open valve characteristic flow coefficient is less than the known open valve flow coefficient. For this 1 sheet drawings