WO2004085027A1

WO2004085027A1 - System comprising a filter with a replaceable filter element, filter element for use in a system of this type, and method for determining a technical state of a replaceable filter element of this type

Info

Publication number: WO2004085027A1
Application number: PCT/NL2004/000211
Authority: WO
Inventors: Henk Van Savooijen; Marinus Johannes Berend Van Boven
Original assignee: Parker Filtration B.V.
Priority date: 2003-03-28
Filing date: 2004-03-29
Publication date: 2004-10-07
Also published as: NL1023037C2

Abstract

A system comprises a filter with a replaceable filter element for filtering a fluid in the system. The filter element is provided with a memory for storing a filter element data item. The system also comprises a control unit for controlling at least part of the system, which is designed to receive the filter element data item. The system also comprises at least one sensor for measuring a respective physical variable in the system. The sensor is connected to the control unit in order to provide a measurement data item relating to the physical variable to the control unit. The control unit is designed to determine a maintenance state data item from the filter element data item and the measurement data item. It is also possible for a data item which is stored in the memory of the filter element to be derived from the maintenance state data item.

Description

Short title: System comprising a filter with a replaceable filter element, filter element for use in a system of this type, and method for determining a technical state of a replaceable filter element of this type

The invention relates to a system, comprising a filter with a replaceable filter element for filtering a fluid in the system, the filter element being provided with a memory for storing a filter element data item, and a control unit for controlling at least a part of the system, which is designed to receive the filter element data item. The invention also relates to a filter element for use in a system of this type. Furthermore, the invention relates to a method for determining a maintenance condition of a replaceable filter element in a system comprising a filter having the filter element, comprising the step of transmitting a filter element data item stored in a memory of the filter element to a control unit of the system. The invention also relates to a computer program comprising program instructions for carrying out a method of this type.

US 5,674,381 has disclosed a filter device having a replaceable filter, comprising an electronic filter identification system. The identification system comprises an electronic label on the filter and a readout unit on the filter device. The readout unit is connected to a control unit of the filter device. The control unit can enable operation of the apparatus when a filter bearing a correct label is fitted. It is also possible for the label to comprise a read/write memory which is designed to store a total number of operating hours of the filter and to switch off the filter device when the maximum permitted number of operating hours has been reached.

One problem is that the number of operating hours is not a reliable measure of the technical state of the filter element, since the state can be influenced by a large number of use factors. To prevent a replaceable filter from becoming excessively worn in an apparatus of this nature, i.e. to prevent it from becoming contaminated, a considerable safety margin has to be maintained, and consequently in many cases the apparatus will indicate that the filter needs to be replaced whereas this is not actually necessary.

It is an object of the invention to provide a more reliable indication of a state of the filter element.

To achieve this object, the system is characterized in that the system furthermore comprises at least one sensor for measuring a respective physical variable in the system, the sensor being connected to the control unit in order to provide the control unit with a measurement data item relating to the physical variable, and in that the control unit is designed to determine a maintenance state data item from the filter element data item and the at least one measurement data item. The sensor provides information about a physical variable in the system, and may, for example, comprise a pressure sensor for measuring a pressure in a fluid flowing through the filter in operation, a sensor for measuring a pressure difference across the filter element in operation, a temperature sensor for measuring an operating temperature of a component of the system, such as the fluid, a flow sensor for measuring a flow velocity or flow rate of the fluid flowing through the filter in operation, a displacement sensor for detecting the opening or closing, during operation, of a component which is integrated in the filter, such as a bypass, a sensor for measuring a level of contamination which is present in the fluid, etc. The measurement data item which is thereby provided to the control unit by the sensor enables the control unit to provide a more reliable indication of a state of the filter on the basis of the measurement data item and the filter element data item which is read from the memory of the filter element. The filter element data item may preferably be one or more data items from a group consisting of a unique identification of the filter, a filter element type and a traceability code. Consequently, the control unit can also derive information about the filter from the filter element data item, for example a mean value for an operating parameter, such as an operating time or operating temperature, maximum quantitative flow, and the like, can be derived from the unique identification of the filter element or the filter element type, so that the control unit can determine a reliable estimate of a state of maintenance or a state of wear for the filter element on the basis of the filter element data item and the at least one measurement data item.

The fluid may, for example, be a liquid, such as a hydraulic fluid or a fuel, but may also be a gaseous medium. The filter element may therefore comprise any filter element which is suitable for filtering a fluid of this type. The memory of the filter element may, for example, comprise a semiconductor memory, in which case this may either be a read-only memory or a memory which is both readable and rewritable. The control unit may comprise a processing unit which is known per se, such as a microprocessor, microcomputer or other calculation unit, and is provided with program instructions for determining the maintenance state data item from the filter element data item and the measurement data item. Of course, this determination will be dependent on the nature of the measurement data item or the measurement data items, and the filter element data item, but if the filter element data item and the at least one measurement data item are known to the person skilled in the art, they will be implemented using program steps which are known per se. As an alternative, it is, of course, also possible for the control unit to comprise suitable hardware for determining the maintenance state data item from the filter element data item and the measurement data item. The maintenance state data item may include any information relating to a state of the filter element. Thus, the maintenance state data item may, for example, include contamination of the filter, an expected remaining number of operating hours, a quantity of particles which has been trapped by the filter, or any other data item relating to a condition of the filter element. Obviously, within the scope of the invention it is also possible for the maintenance state data item to include a data item concerning a state of the filter element and a data item relating to the identification of the filter element, so that this defines a relationship between the maintenance state data item and the specific filter element. The data item relating to the identification of the filter element may in this case be determined from the filter element data item and the data item relating to the state of maintenance, from the measurement data item or the filter element data item or from both of the latter. The replaceable filter element may comprise part of the filter, such as a component with a filter cartridge, but it is also possible for the filter element to comprise the entire filter.

It is preferable that the control unit is designed for comparing the maintenance data item with a replacement value of the filter element, and generating a replacement message for replacing the filter when the maintenance data item exceeds the replacement value. The control unit periodically or continuously compares the maintenance data item with a replacement value which is e.g. stored in a memory of the control unit and generates a replacement message when the replacement value is exceeded. Based on the replacement message, then control unit or an other control unit of a device which is coupled to the system can take an action, such as e.g. the generating of an alarm message, the switching of of the system or a part thereof or the lowering of one or more operational parameters such as an operational pressure, a flow of the filter etc. and/or the stepwise deactivating of the system. Also, it is possible that the control unit based on the replacement message sends, e.g. via a mobile communication link, a message. Instead of or in addition to a replacement value, the idea according to this embodiment is also applicable to any other suitable parameter which relates to a quality, state or time of life of the filter element. The replacement value can e.g. be a. fixed value or a value which is stored in the memory of the filter element and which is determined for the respective filter element, however it is also possible that the control unit is arranged for adapting the replacement value of any suitable parameter based on the measurement data item, the filter, element data item and/of the maintenance state data item. This solves the problem that the replacement values are often fixed with a considerable margin.

As the system could be used by a user under various conditions

(a dirty or clean environment, a continuous use or an intermittent use, etc.) the replacement value is in general based on a generic criterion. By adapting the replacement value based on the measurement data item, the replacement value can be adapted to conditions of use under which the respective filter element is used. By adapting the replacement value based on the filter element data, the replacement value can be adapted based on the specific properties of the filter element, such as for example a quality parameter while taking account of a more or less durable filter element, etc. By adapting the replacement value based on the maintenance state data item, account can by taken e.g. of a filter element which has already been used before when it is mounted into the system. Also, based on a maintenance state data item and/or a change over time of the measurement data it could be determined if possibly a filter element of an other type (e.g. a more simple filter element having a lower quality) has been placed because by such a filter element a faster change over time of the measurement data item and/or the maintenance state data item will be detected by the control unit. Based on such a, e.g. faster change of the respective data, the control unit can amend the replacement value such that e.g. a replacement message will be generated earlier.

The control unit is advantageously adapted for initiating an action to take the filter element out of service in response to the generating of the replacement message. The control unit is advantageously adapted for dependent on a value of the measurement data item and/or the maintenance state data item, selecting the action from a group of actions comprising the taking out of service of the system, the guiding of the fluid past the filter element, the not again taken into operation of the system and the determining of a maximum operating condition of the filter element. The control unit can thus be adapted for the directly taking out of service of the system, the bypassing of the filter element, the allowing continuation but after a taking out of service not again taking into operation of the system, and the reaching of a maximum operating condition (such as a maximum flow, operating pressure of temperature) of the filter element. For the predicting of a remaining lifetime of the filter element, the control unit is in an advantageous embodiment adapted for: the storing of a known end value of the maintenance state data item, the at least two times determining, with an intermediate time interval, of the maintenance state data item of the filter element, the determining of a speed of increase of the maintenance state data item from the at least two times determined maintenance state data item and the time interval, and the determining of a remaining lifetime of the filter element from the maintenance state data item, the end value and the speed of increase of the maintenance state data item. The applicant has realised that during a use of the filter element a continuous degradation of the filter element, and thus the maintenance state data item occurs, whereby this degradation takes place at first only very slowly, however when reaching an end of the live time of the filter element, a comparatively much faster degradation of the filter element, and thus the maintenance state data item occurs. A replacing of the filter element therefor needs to take place around, or advantageously just before the moment when a strong degradation of the maintenance state data item will take place. The inventor has further realised that by two times determining the maintenance state data item of the filter element with an intermediate time interval, a speed of the change of the maintenance state data item can be calculated from the difference between the maintenance state data item which has been determined two times and the time interval between these determinations. The inventor has realised that the remaining life time of the filter element can be determined from the speed of increase of the maintenance state data item and the lastly measured value of the maintenance state data item. When e.g. the determination of the maintenance state data item indicates that the filter is in relatively fresh state but that the speed of increase of the maintenance state data item is relatively high, a relatively short remaining life time will determined. On the contrary, when the maintenance state data item indicates that the filter already is in a progressive state of use but that the increase of the maintenance state data item is only very slowly, a relatively long remaining life time can be indicated nevertheless. The control unit is in this case advantageously adapted for the determining of the maintenance state data item from at least one quantity from a group comprising a level of cleanness of filtration, a pore size of the filter element, a temperature, a viscosity of the fluid, a flow of the fluid, and a load of the filter material, or any other suitable operating parameter. The Inventor has devised that for a reliable determination of the remaining life time, the maintenance state data item advantageously requires one or more of the qualities of the said group. The skilled person will, taking into account the operating conditions of the respective system in practice based on this explanation, be able to make a suitable choice for the maintenance state data item for a particular application of the system. Advantageously, the control unit is adapted for the storing of the end value, the remaining life time and the determined maintenance state data item in the memory of the filter element. When e.g. the filter element is interimly taken out of the system and inserted again at a later moment in time, a remaining life time and/or a maintenance state of the respective filter element can be determined in a reliable manner when the latter is placed again into the system.

The control unit is advantageously arranged for: the storing of the filter element data item which has been received from the filter element, the periodically determining based on the received filter element data item if the filter element has been removed or replaced, and the after a removal or replacement of the filter element storing of a time data item in connection with the stored filter element data item.

In this manner it is possible to, whether or not in combination with the storing of data items in the memory of the filter element as described above, to store data about replacement of the filter element in the control unit. This can be particularly advantageous when a user instead of making use of a filter element according to the invention, uses another e.g. plagiate or more simple filter element. By in the system, and in particular with the aid of the control unit, keeping track of when a filter element has been replaced, and which filter element this concerns, it can e.g. at a later moment in time been established that during a certain time a correct type of filter element has been used, and e.g. during another period of operation no filter element has been present, or use has been made of a wrong filter element or an other than prescribed type of filter element. The filter element data item can to this end be stored in the control unit of each suitable other part of the system. Also, it is possible that the control unit is arranged for the sending via a communication means of the filter element data item to e.g. another control unit which will take care of the storing of the respective data. Another important advantage is that it is in this manner possible to find out any possible misuse or to refute a suspicion of misuse by the possibility to store data of the filter element in the control unit and/or the storing of data in the memory of the filter element. The data can be stored e.g. in a form of a table whereby every time the data and a corresponding time information is stored. When the control unit thus detects a removal or replacement of the filter element, the control unit can arrange for a suitable alteration of e.g. a replacement value, a maximum operation condition, an end value etc. In this manner, the control unit could e.g. in absence of a filter only allow a limited operation, or upon placing a filter element of an unknown origin (which e.g. is not provided with a memory having a corresponding filter element memory) could limit a maximum duration of operation or other replacement values or end values .

Where in the document reference is made to a control unit, this can concern a separate unit of the system according to the invention, however it is also possible that at least a part of the functions of the control unit are executed by a control unit such as a computer, board-computer, machine control, PLC, micro controller or any other suitable control unit of a system or device wherein the system according to the invention is embedded .

Furthermore, it is preferable for the control unit to be designed to determine a use data item for the filter element, which can be stored in a memory of the filter element and/or the control system, from the maintenance state data item, and to store the use data item in the memory of the filter element and/or control system. Consequently, a use data item, which includes, for example, part of the maintenance state data item, can be derived from the maintenance state data item. In general, there is a limited space for storing data items in the memory of the filter element, and consequently the use data item will generally be a data item which requires relatively little memory space, but it is, of course, also possible for the use data item to correspond to the maintenance state data item. Storing the use data item, and therefore data items relating to the state, the use history, critical use conditions which have occurred, error messages which have been derived from the maintenance state data items, etc. in the memory of the filter element and/or the control system makes it possible to work out a history of the filter element and its use. This means that, depending on the contents of the use data items stored in the memory, it is possible to investigate the conditions under which the filter element was used and where the filter element was used, so that, for example in the event of a liability claim against the supplier of the filter element, in the event of damage to a component of the system, it is possible to investigate whether the filter element has been used appropriately and/or, for example, was exposed to extreme use conditions outside a normal operating range.

It is preferable for the filter element data item to comprise at least part of the use data item stored in the memory. This makes it possible for the filter element data item, which is read by the control unit and is used in the determination of the maintenance state data item, also to include data relating to earlier determinations of the maintenance state data item, or at least the use data item derived therefrom and used in the determination of the maintenance state data item. This therefore means that the maintenance state data item is in this way determined not only from the measurement of the physical variable and a substantially invariable filter element data item, but also from (part of) the filter element data item which contains previously stored data items relating to earlier determinations of the maintenance state data item. This makes it possible to implement a further improvement to the determination of the maintenance state data item, since it is possible to use not only data items relating to the current situation (as presented by a measurement data item from a sensor) , but also data items which have previously been stored in the memory of the filter element and may include an indication of previous use, error conditions which have previously occurred, alarm messages which have previously occurred, etc. If the filter element is, for example, exposed to an excessively high pressure or an excessively high temperature at a given moment, this could lead to a use data item being stored in the memory of the filter element and/or the control system, indicating that a use condition of this nature lying outside a standard use condition has occurred. Since the use data items stored in the filter element can also be taken into account in the determination of future maintenance state data items, this means that this error condition which has previously occurred can also be taken into account in the determination of the maintenance state data item. This will mean, for example, that the maintenance state data item will indicate that it is desirable to replace the filter element at an earlier stage than would be the case if a critical operating condition had not previously occurred.

The use data item preferably comprises one or more data items from a group consisting of an identification of the system for identifying the system in which the filter element is or was positioned, a status code for indicating a status of the filter element and a quality data item for indicating a use condition or use condition history of the filter element.

Furthermore, the control unit is preferably designed to compare at least part of the use data item and/or the filter element data item with data items in a table which are accessible to the control unit, and to store at least the part of the use data item and the filter element data item in the table if the said part does not correspond to the most recent data item in the table. In this way, information relating to the filter element can be kept up to date by the control unit and therefore by the system. Thus, the data stored in the table could be used to work out, for example, when replacement of the filter element has occurred. This is because at that moment the filter element data items will no longer correspond to those stored in the table, and consequently new data items will be written to the table. The data items are preferably held chronologically in the table, so that successive changes can be read out from the table. It is preferable for the table also to include data relating to the date and time of the occurrence of the change, so that it is possible to retrospectively trace events which led to new data items being input into the table with considerable accuracy. The comparison can be carried out on the basis of, for example, an identification of the filter element, so that it is possible to indicate that a new filter element has been installed on the basis of the occurrence of an error condition, alarm condition, critical operating condition and the like, so that the occurrence of a condition of this type can be recorded in the table. One advantage of storing the data items in the control unit or such that they are accessible to the control unit is that if an error should occur, caused by an incorrectly functioning filter element, or a filter element of a different type or a different origin, an operator of the system could replace the incorrect or defective filter element with a correct filter element, in order thereby to gloss over incorrect maintenance or incorrect use. This can subsequently be traced by virtue of the fact that at least some of the filter element data items and/or use data items are stored in the table in the control unit, and consequently replacement of the filter element of this nature can likewise be traced. It would also be possible, for example, for the critical use conditions which lie outside a normal range for the system to be stored in the memory of the filter element and in the table, so that these data items too can still be called up in the system after the filter element has been replaced. It is preferable for the filter element data item to include a type code for identifying a filter element type, and for the control unit to be designed to compare the type code with a list containing accepted filter element types and to generate an error message if the type code is not found in the list containing accepted filter element types. This makes it easy to generate an error message if a filter element of an incorrect type is installed in the system.

It is preferable for the maintenance state data item and/or use data item to include a status code and for the control unit to comprise means for generating an alarm report if the status code has a predetermined value. This makes it easy to generate an alarm report if certain conditions occur.

The system preferably comprises a readout unit which is connected to the control unit in order to display the maintenance state data item. In this way, the maintenance state data item can be displayed in a user-friendly way to, for example, a user of the system or a person carrying out maintenance on the system. The maintenance state data item may, depending on its nature, be displayed numerically, graphically or in the form of a combination thereof. Obviously, it would be clear that the maintenance state data item may comprise a single data item but may also comprise a plurality of data items, such as parameters, status information, etc.

The system preferably comprises a communication means for transmitting the maintenance state data item. This makes it possible to gain an insight into functioning, need for maintenance and/or condition of the system remotely via the communication means, so that, for example in the case of a system which is difficult to gain access to or is located remotely, it is easy to gain an insight into the condition of the system.

The method according to the invention is characterized in that the method also comprises the steps of using the control unit to receive a measurement data item which provides information about a physical variable in the system which has been measured by a sensor; and using the control unit to determine a maintenance state data item from the filter element data item and the at least one measurement data item.

Furthermore, the method preferably comprises the further steps of determining a use data item for the filter element, which is to be stored in a memory of the filter element and/or the control system, from the maintenance state data item; and storing the use data item in the memory of the filter element and/or the control system. ^'

The filter element data item preferably comprises at least part of the use data item stored in the memory.

Obviously, it will be clear that the method according to the invention may also comprise the further aspects and preferred embodiments as described with reference to the system according to the invention.

The invention will be explained in more detail on the basis of the appended drawing, which shows a non-limiting exemplary embodiment of the invention and in which:

Fig. 1 shows a block diagram of a system according to the invention;

Fig. 2A-C show a flow chart which shows the functioning of the system shown in Fig. 1 and an embodiment of the method according to the invention;

Fig. 3 shows a graphical view of a change over time of a maintenance state data item for illustration of a determination of a remaining live time of the filter element; and Fig. 4 a-b shows a further example of the functioning of the system and the method according to the invention.

Fig. 1 shows a filter 1 with a replaceable filter element 2 which is provided with a memory, in this example an identification chip 3. The identification chip 3 can be read out via an antenna 4 which is connected to a readout unit 5. The readout unit 5 is preferably also able to transmit one or more data items via the antenna 4 to the identification chip 3 in order for these data items to be stored in a memory of the identification chip. The identification chip 3 is accommodated in the filter element 2. The system also comprises a control unit 6 which is connected to the readout unit 5 for the exchange of data items. Furthermore, the control unit 6 is connected, in this exemplary embodiment via a communication bus 7, to one or more readout units 8, such as measurement amplifiers for reading out a measurement data item from a sensor 9. The sensor 9 may be a sensor for recording a pressure difference, a temperature, a contamination level, for example a water level, a flow velocity, the opening of a bypass, may be a counter for counting contaminating particles, etc. Furthermore, the system may be connected to a communication means, such as a communication unit 10, which may comprise a bus system, a display, a personal computer, a so-called human-machine interface, a mobile telephone connection (for example Bluetooth, wireless, etc.), an intranet or the Internet. Via the communication unit 10, it is also possible to exchange data items with a user or another system.

Obviously, it will be clear that numerous alternatives are possible within the scope of the invention, for example the memory in the filter element 2 can be read out in any suitable way by the control unit 6, and the sensor or sensors 9 may be connected to the control unit 6 in any suitable way. It is also possible for the exchange of data items between the sensors 9 and the control unit 6 and between the communication unit 10 and control unit 6 to take place via the same connection, such as a bus system.

The system functions as follows. Measurement data items are transmitted to the control unit 6 by the sensors 9 via the measurement amplifiers 8 and the bus 7, either continuously, periodically or on request from the control unit 6. The control unit 6 also receives a filter element data item, which has been read from the identification chip 3 by the readout unit 5, from the said readout unit 5. The control unit 6 then determines a maintenance state data item relating to the filter element 2 from at least one measurement data item and from the filter element data item. The maintenance state data item can be displayed via the communication unit 10, can be transmitted via a communication means, such as a mobile telephone link, a network or bus system, etc. It is also possible for the control unit 6 to cause an actuator (not shown) to adjust the system on the basis of the maintenance state data item, leading, for example, to a change in an operating pressure on the filter element 2, a change in a flow velocity through the filter element 2, etc. It is also possible for the control unit 6 to derive from the maintenance state data item a use data item which, via the readout unit 5 and the antenna 4, is stored in the memory of the identification chip 3.

The functioning of the system and the method will now be described in detail with reference to Fig. 2A-C. In step 100, a filter element data item, such as an identification (ID) of the filter element, is read out. Then, in step 110, if there is no identification in the filter element, an error message of a first type is generated, whereas if there is an identification in the filter element, the method continues with step 120. In step 120, the element type is read out, for example by a filter element data item again being read out of the filter element, but it is also possible for the filter element data item which was read out at step 100 to comprise a plurality of data items and for the filter element type already to be included in these data items. Then, in step 130, it is checked whether the filter element type corresponds to a type which is included in a first table. If so, step 140 moves on to step 150, and if not an error message of a second type is generated. Between step 140 and step 150, a determination of an integrity of the filter element can be established. When the determination results in a compliance of the system to the requirement of integrity, it can be proceeded with step 150 while in the case that the system does not meet the requirement of integrity an error code (e.g. error code 4) can be generated whereby it is proceeded with step 310. In this context, the wording integrity of the filter system is explained as e.g. the number of times that a filter element is taken out of the system and replaced again. Also these wordings can be interpreted as any other quality parameter of the filter element, such as the indexes qi and q₂ which will be discussed below based on fig. 3. In step 150, it is investigated whether the filter element comprises a memory which is both readable and writable. If not, the method continues with step 240, and if so the method continues with step 170. In step 170, a filter element data item is read out; this filter element data item comprises one or more unchangeable data items stored in the memory of the filter element and use data items for the filter which have previously been determined and have previously been stored in the filter element. Then, in step 180, these data items which have been read out are compared with a second table. If it is found in step 190 that the data items correspond, the method continues with step 220, whereas if it is found that the data items do not correspond, the method continues with step 200. A new filter element data item is generated at step 200. This situation may arise if a change has occurred, for example replacement of the filter element, although it is also possible for a situation of this nature to arise if a relevant changed use data item has been stored in the memory of the filter element. The changed filter element data item can then be stored in the respective table and/or in the memory of the filter element and/or the control unit in step 210, after which the method continues with step 220. In step 220, a status is determined from the filter element data item, and if the status is not appropriate an error message of a third type is generated. If the status is found to be appropriate, the method continues with step 240. Step 240 again investigates whether the filter element comprises a read/write memory, and if so the method continues with step 250. If not, the method continues with step 290. In step 250, the at least one measurement data item from the at least one sensor is read and interpreted, and a maintenance state data item and a use data item are determined therefrom. Then, in step 260, the use data item is written to the memory of the filter element. Then, a status of the element is determined at step 270, as will be explained below on the basis of a few examples. Then, in step 280, the method returns to step 240 if the status is appropriate, or continues to step 300 if the status is not appropriate. In step 300, the status of the filter element is written to the memory of the filter element, and then an error message of the third type is generated. If it is found in step 280 that the status of the element is appropriate, i.e. that no exceptional operating conditions have occurred, the method returns to step 240. Therefore, the steps 240, 250, 260, 270 and 280 form a loop which is repeated, with measurement data items being read, maintenance state data items determined, use data items determined and stored in the memory of the filter element and then the status of the filter element being determined each time. The loop can be interrupted by a stop command, as indicated by step 290, so that the procedure is terminated. In the event of the error message of the first, second and/or third type being generated, these error messages are then written to the second table, as indicated at step 310, and then an alarm message is generated in step 320, after which the procedure is ended at step 330.

The steps as described with reference to Fig. 2A, 2B, 2C can be carried out by suitable processing means, such as a microcontroller, microprocessor or other programmable modules, which is provided with suitable programming instructions for carrying out these steps. The determination of the maintenance state data item from the measurement data item and the filter element data item will be dependent on the nature of the use, the type of sensors used, and the like, but the person skilled in the art, on the basis of the above explanations, will readily be able to establish a suitable algorithm for determining a maintenance state data item for a specific application.

Fig. 3 shows a graphical view wherein along a horizontal axis a time is displayed while along vertical axis a maintenance state data item is displayed. An increase of a value of the maintenance state data item is in this context to be understood as a deterioration of a state of the filter, the skilled person would however understand that also a concept wherein a reversed change over time is applied, is equally well applicable in the context of the invention. The maintenance state data item is in fig. 3 indicated by the term q. From the curve q in fig. 3 it can be read that the quantity q (also indicated as quality index) increases gradually over time. This gradual increase can be linear over time as indicated in fig. 3, however also a different change over time is possible. From a certain moment which in the figure has been indicated as the time T_Q a comparatively significantly stronger change of a state of the filter appears to occur, which is also expressed in the curve of q_t as a strong increase of the maintenance data item, the quality factor q. As the working of the filter element will substantially change as from the time T_Qι e.g. by a silting up of the filter, replacement is therefor required to take place around or shortly before reaching the T_Q. The curve of q_t which is depicted in fig. 3, will be walked through by each filter element. However, the actual time intervals and the actual duration of use until the moment of reaching the time T_Q will very strongly depend on an amount of use, an intensity of use, a level of contamination, temperature and other conditions of behaviour. In case that according to the state of the art, a fixed duration of operation (e.g. a fixed amount of hours of operation) is applied for the moment for replacement of the filter, then depending on the conditions of use, the bend in the curve which is indicated with T can not yet be reached by far or contrarily have been surpassed by far, which can lead to undesired conditions by strong degradation of the filter element. Because of the strong degradation from the point T_Q, in practice according to state of the art, consequently a large safety margin is kept with regard to this point, such that in practice usually a replacement of the filter element is performed too early. The band in the curve of q_t will in the below be indicated with Q, in other words, the value of the index q at which the band in the curve q_t occurs .

According to the invention a maintenance state data item of the filter element is determined with an intermediate time interval, whereby in the exemplary embodiment of fig. 3 this takes place at the times t_x and t₂. From the measurement data item, the control unit determines a maintenance data item at the times t_x and t_2, which is indicated as q_x and q₂ respectively. Based on the values of q₁ and q₂ which have been calculated at the times t_x and t₂, a time can be determined at which the bend in the curve q_t, will be reached, in other words the remaining time from the moment t₂ (whereby an index q₂ has been reached) until the reaching of the moment T_Q (whereby the band Q will be reached) . This moment in time T_Q can in this exemplary embodiment be calculated based on the following formula: To = (Q-q₂) ( z-TQ - (T₂-T_x) , (q₂-qι) whereby the expressions tj., t₂, qi, q₂, Q and T_Q have been defined in the above text. In this manner, based on the maintenance state data item (in this example the index q) , the end value (in this example the band in the curve indicated as Q) and the speed of increase of the maintenance state data item (in this example determined from the difference between the values of qi and q₂ and the difference in time between t_x and t₂) have been determined. The quantities of the q, T_Q and the values q₁₍ q₂ at the times t_x and t₂, can be stored in the memory in the filter element, such that data about a maintenance state data item of the filter is present in the filter, which e.g. is advantageous when the filter is demounted, e.g. mounted again in the system such that on that basis a remaining life time of the filter can be determined also after an intermittent taking out of the filter element.

The maintenance state data item, in fig. 3 the quality index Q, can be determined on a basis of a large amount of data. Suitable data appears to be a cleanness of filtration, a pore size of the filter element, a temperature, a viscosity of the fluid, a flow of the fluid and a load of the filter material on each suitable combination of this data. The term cleanness of filtration is to be understood here as a relation between a level of contamination of the fluid flowing into the filter element and a level of contamination of the fluid flowing out of the filter element .

Whether or not in connection with the exemplary embodiment as discribed in connection with fig. 3, it is also possible that the maintenance state data item is compared with a replacement value of the filter element and that a replacement message is generated when the maintenance state data item exceeds the replacement value. The replacement value can in this context e.g. be determined based on the measurement data item or the filter element data item and/or can be determined based on the steps as shown with reference to fig. 3. When reaching the replacement value or when reaching or approaching the moment in time T_Q as shown in fig. 3, the control unit can take an action to take the filter element out of operation in response to .the generating of the replacement message, such as an action to directly switch off the device, the generating of an alarm message, the sending of a maintenance message, the reducing of a maximum parameter of operation, such as an operating pressure, a speed of flow, etc. and/or not allowing a renewed taking into operation of the system after a taking out of operation thereof.

Next to, or as an alternative of the storing of data in the memory of the filter element, it is also possible to store data in the control unit, or to have data stored by the control unit, e.g. at a moment of removal or replacement of the filter element, by e.g. periodically checking if the filter element has been removed or replaced, and to store the filter element data item in combination with a time data item after a removal or replacement of the filter element.

Fig. 4a and 4b show a flow diagram illustrating the method and the system according tot the invention. The flow diagram shows an application of a mobile crane, such as e.g. a crane equipped with an hydraulic system comprising a filter having a system according to the invention. The steps has shown in fig. 4a and 4b are executed by a local control unit such as a local control system, a P C, a microcontroller, microprocessor etc. The local control system is connected by means of a suitable communication connection, such as a bus, to a total maintenance system for the mobile crane, a diagnostics- and safety system and a communication system for communication via an external connection. Via the communication system, remote control and maintenance is possible, or updates can be obtained for the software for performing the steps. In step 400 the filter system is checked, whereby amongst others by means of reading out of the filter element data item it is checked if a correct type of filter has been placed and/or a maintenance state of the filter. When this is considered acceptable (step 401) it is preceded with step 402, while when this is not accepted an error message is generated. In step 402 data of the total control system (overall management system) can be obtained and after that in step 403 it can be decided if an updating of the software for executing the steps is to be carried out. If this is the case, in step 404 the respective information is collected, interpreted, and stored as program instructions. After that or in case that no updating is required, directly from step 403, it is proceeded with step 405 whereby the filter system is ready to register and interprete measurement data items and system data items. If this is not the case, than in step 406 it is returned to step 400 and otherwise to step 407. In step 407, the data of the sensor (the measurement data items) and system data items are traced and interpreted and system data items are also followed and interpreted and quality data items (such as a maintenance data item) are generated. Thereafter, in step 408 a state of the filter element is determined (e.g. expressed in terms of a filter element data item) and this is written if required into the memory of the filter element. If induced by measured values and/or maintenance state date items or quality data items, in step 409 a warning can be generated based on diagnostic functions and a quality state. If this is the case step (410) an error message will be generated, the warning will be stored in step 411, and in step 412 it will be determined if the warning is also to be stored in the filter element (step 413) . Thereafter it is proceeded with step 414 whereby it is checked if the system is still in operation. If this is the case and the system is required to stay in operation, it is returned to step 407. If the system is not required to stay in operation or can not stay in operation, it is proceeded with step 416 whereby the crane is taken out of operation and the measurement data items are interpreted. Also, maintenance state data items and quality data items are generated. This is repeated in step 417 until the crane is taken out of operation (step 418) . With the steps as described it is thus accomplished that a state of the filter element is monitored, a warning or error message is generated when certain limits are exceeded and in case that is desired that the system is switched off. The warnings can be stored in the system and/or in the filter element such that error conditions are traceable later. Besides, when in step 401 and/or 410 an error code is generated, this can lead to a switching off of the system. With the error code, depending on the application, the control unit can get an action going, varying from the activation of an alarm or alarm message, to the controlled or immediate taking out of operation of the system.

Wherever the present document refers to a data item, such as a filter element data item, a measurement data item, a use data item and the like, it will be clear that this term is to be understood as meaning not just a single data item, such as a single measured value, a single status code or status bit, a single analogue measured value or the like, but rather that the term data item is also to be understood as encompassing a combination of two or more different data items.

Therefore, with the system and method according to the invention it is possible to gain information about correct functioning of the filter element and information about the filter element, and also, on the basis of the maintenance state data items obtained from these data items, to store information in the memory of the filter element, so that this information can also be taken into consideration during subsequent determinations of a maintenance state data item. It is also possible for the maintenance state data items or error codes and alarm messages originating therefrom to be stored in the control unit or such that they are accessible to the control unit, so that it is also possible to investigate, in the system of which the control unit forms part, what events have occurred. This means, for example, that even after the filter element in the system has been exchanged, information concerning events which have previously taken place remain present in the system. In particular if the system is combined with a communication means for transmitting maintenance state data items or part thereof, status data items, alarm messages and the like to another location, it is possible to obtain a very reliable and traceable system, since data items relating to an operating condition of the system and the filter element in particular are stored in both the system and the filter element, and are also transmitted via the communication means to a remote unit, from where action can be initiated if necessary, depending on the data items obtained. Obviously, it is also possible for data items to be transmitted from a regulating unit, control unit or the like via the communication means to the control unit in order thereby, for example, to influence the sequence of steps and processes running in the control unit. A system of this type could, for example, be used very successfully for a hydraulic system in a windmill which is positioned in a wind farm, for example out at sea, so that data items relating to a condition of the filter, such as contamination, a quantity of moisture absorbed, or any other relevant parameter which may influence a decision to replace the filter element are stored both in the system and the filter element and also are transmitted via, in this case, by way of example, a mobile telephone link, such as a GSM, GPRS or UMTS link, or via the Internet/intranet, to a monitoring unit, such as control room.

The text which follows will provide a number of possible applications of the invention:

In a first example, the filter element comprises an identification chip with a memory which is rewritable, and the system comprises a temperature and pressure sensor. A degree of contamination of the filter element can be derived from a pressure drop across the filter element in combination with a temperature of the fluid. Data items relating to a minimum and maximum temperature, a maximum measured pressure difference across the filter element and a degree of saturation of the element or whether or not the element is completely saturated can be stored in the memory in the filter element. The data items stored in the filter element can also be used to determine the maintenance data item, so that it is possible to assess the quality and state of the element on the basis of the history of the filter element in question, even if, for example, the filter element has been transferred from system to system. In this way, it is possible to make maximum use of the service life of the filter element, which on the one hand does not require the element to be replaced prematurely, but on the other hand allows reliable detection of complete contamination of the filter element, even if the latter has, for example, been transferred from system to system. The pressure sensor may, incidentally, be accommodated in the filter itself or in one or more parts of the system which are in communication with the filter.

In a second exemplary embodiment, the filter element comprises a rewritable memory, and the system comprises a plurality of sensors for recording specific variables. The sensors may, for example, comprise contamination sensors for measuring a quantity of contaminating particles in the fluid, or a moisture sensor for measuring a quantity of moisture in the fluid. In this exemplary embodiment too, it is possible for the abovementioned temperature and pressure sensor to be present . A forecast about the technical use condition of the filter element at that time can be made on the basis of the measurement data items obtained from the various sensors, by means of a suitable algorithm which is programmed, for example, into a computer, so that a maintenance data item can be derived therefrom. In this case too, all the information is written to the memory of the filter element, so that it becomes possible to determine the technical quality, and therefore the maintenance data item, of the element on the basis of the measured measurement variables and on the basis of the historic data items stored in the memory of the filter element.

Claims

1. System, comprising - a filter with a replaceable filter element for filtering a fluid in the system, the filter element being provided with a memory for storing a filter element data item, and a control unit for controlling at least a part of the system, which is designed to receive the filter element data item, characterized in that the system furthermore comprises at least one sensor for measuring a respective physical variable in the system, the sensor being connected to the control unit in order to provide the control unit with a measurement data item relating to the physical variable, and in that the control unit is designed to determine a maintenance state data item from the filter element data item and the at least one measurement data item.

2. System according to any of the preceding claims, characterized in that the control unit is adapted for the comparing of the maintenance state data item with a replacement value of the filter element, and the generating of a replacement message to replace the filter when the maintenance state date item exceeds the replacement value.

3. System according to claim 2, characterized in that the control unit is adapted for adapting the replacement value based on the measurement data item, the filter element data item and/or the maintenance state data item.

4. System according to claim 2 or 3, characterized in that the control unit is adapted for initiating an action to take the filter element out of operation in response to the generation of the replacement message.

5. System according to claim 4, characterized in that the control unit is arranged for, in dependency on a value of the measurement data item and/or the maintenance state data item, choosing the action from a group of actions comprising the taking out of operation of the system, the guiding of the fluid along the filter element, the not again taking into operation of the system and the establishing of a maximum operating condition of the filter element.

6. System according to any of the preceding claims, characterized in that the control unit is arranged for: the storing of a known end value of the maintenance state data item, - the at least two times determining, with an intermediate time interval, of the maintenance state data item of the filter element, the determining of a speed of increase of the maintenance state data item from the at least two times determined maintenance state data item and the time interval, and the determining of a remaining life time of the filter element from the maintenance state data item, the end value and the speed of increase of the maintenance state data item.

7. System according to claim 6, characterized in that the control unit is adapted for the determining of the maintenance state data item from at least a quantity of a group comprising a level of cleanness of filtration, a pore size of the filter element, a temperature, a viscosity of the fluid, a flow of the fluid, and a load of the filter material.

8. System according claim 6 or 7, characterized in that the control unit is adapted for the storing of the end value, the remaining life time and the determined maintenance state data item in the memory of the filter element.

9. System according to any of the preceding claims, characterised in that the control unit is adapted for: the storing of the filter element data item which has been received from the filter element, the periodically checking based on the received filter element data item if the filter element has been removed or replaced, and the after a removal or replacement of the filter element storing of a time data item in connection with the stored filter element data item.

10. System according to any of the preceding claims, characterized in that the control unit is also designed to determine, from the maintenance state data item, a use data item for the filter element, which can be stored in a memory of the filter element and/or the control system, and to store the use data item in the memory of the filter element and/or the control system.

11. System according to any of the preceding claims, characterized in that the filter element data item comprises at least part of the use data item stored in the memory.

12. System according to one of the preceding claims, characterized in that the filter element data item comprises one or more items from a group consisting of a unique identification of the filter element, a filter element type and a traceability code.

13. System according to any of the preceding claims, characterized in that the use data item comprises one or more items from a group consisting of an identification of the system for identifying the system in which the filter element is or was positioned, a status code for indicating a status of the filter element and a quality data item for indicating a use condition or use condition history of the filter element.

14. System according to one of the preceding claims, characterized in that the sensor comprises one or more components from a group consisting of a pressure sensor for measuring a pressure in a fluid flowing through the filter in operation, a sensor for measuring a pressure difference across the filter in operation, a temperature sensor for measuring an operating temperature of a component of the system, a flow sensor for measuring a flow velocity or flow rate of the fluid flowing through the filter in operation, a displacement sensor for detecting the opening or closing, during operation, of a component which is integrated in the filter, such as a bypass, and a sensor for measuring a level of contamination which is present in the fluid.

15. System according to one of the preceding claims, characterized in that the control unit is also designed to: compare at least part of the use data item and/or the filter element data item with data items in a table which are accessible to the control unit, and store at least part of the use data item and the filter element data item in the table if the said part does not correspond to a most recent data item in the table.

16. System according to one of the preceding claims, characterized in that the filter element data item comprises a type code for identifying a filter element type, and in that the control unit is designed to compare the type code with a list containing accepted filter element types and to generate an error message if the type code is not found in the list containing accepted filter element types.

17. System according to any of the preceding claims, characterized in that the maintenance state data item and/or the use data item comprises a status code, and in that the control unit comprises means for generating an alarm report if the status code has a predetermined value .

18. System according to one of the preceding claims, characterized in that the system furthermore comprises a readout unit which is connected to the control unit in order to display the maintenance state data item.

19. System according to one of the preceding claims, characterized in that the system comprises a communication means for transmitting the maintenance state data item.

20. Filter element for use in a system according to one of the preceding claims.

21. Method for determining a maintenance condition of a replaceable filter element in a system comprising a filter having the filter element, comprising the step of: transmitting a filter element data item stored in a memory of the filter element to a control unit of the system, characterized in that the method also comprises the steps of: using the control unit to receive a measurement data item which provides information about a physical variable in the system which has been measured by a sensor; and - using the control unit to determine a maintenance state data item from the filter element data item and the at least one measurement data item.

22. Method according to claim 21, characterized by the further steps of: determining a use data item for the filter element, which is to be stored in a memory of the filter element and/or the control system, from the maintenance state data item; and storing the use data item in the memory of the filter element and/or the control system.

23. Method according to claim 21 or 22, characterized in that the filter element data item comprises at least part of the use data item stored in the memory.

24. Computer program comprising program instructions for carrying out the method according to one of claims 21-23.