Patent Application
20240075753
This application claims priority to German Patent Application No. 10 2022 122 204.7 filed Sep. 1, 2022, the disclosure of which is hereby incorporated by reference in its entirety.
The invention relates to a device and a corresponding method for controlling the heating elements of a drying unit for drying a recording medium, in particular for use in an inkjet printing device.
Inkjet printing devices can be used for printing to recording media, for example paper. For this purpose, one or more nozzles are used in order to fire ink droplets onto the recording medium, and thus to generate a desired print image on the recording medium.
An inkjet printing device can comprise one or more drying units in order to dry the recording medium after application of the print image and to thereby fix the applied ink on the recording medium. A drying unit can have a drying route with a plurality of drying modules. The individual drying modules can be configured to blow a warmed gaseous drying medium, in particular air, toward the surface of the recording medium in order to dry said recording medium. For this purpose, the individual drying modules can respectively have a heating element.
Within the scope of the drying of a printed recording medium, the temperature of the recording medium can be detected and the individual drying modules—in particular the heating elements of the individual drying modules—can be controlled and/or regulated depending on the detected temperature. The temperature of the recording medium can thereby be detected, for example in an unprinted region of the recording medium, in order to provide consistent conditions for the temperature detection, and thus in order to enable a reliable and robust control and/or regulation of the drying process.
The heating elements of the individual drying modules of a drying unit typically have a relatively high electric power consumption, which can lead to a relatively high loading of a power supply network, in particular of a three-phase alternating current supply network.
The present document deals with the technical object of enabling a power-efficient operation of a drying unit for a printing device via which an especially light loading of a power supply network is effected.
According to one aspect, a device is described for controlling a plurality of heating elements of a drying unit to dry a recording medium printed to by a printing device. The device is configured, for each of the plurality of heating elements, to determine a respective number of periods of an alternating current for which the respective heating element should be active in a heating cycle, wherein the heating cycle comprises a sequence of successive periods of the alternating current. The device is also configured to determine a heating block within the heating cycle for the respective heating element, which heating block has precisely the number of periods of the alternating current that was determined for the respective heating element, and to effect that the respective heating element is active in the zero, one, or more periods of the heating cycle that are indicated by the determined heating block, and is inactive in the zero, one, or more periods of the heating cycle outside of the determined heating block.
According to a further aspect, a method is described for controlling a plurality of heating elements of a drying unit for drying a recording medium printed to by a printing device. The method comprises, for each of the plurality of heating elements, the determination of a respective number of periods of an alternating current for which the respective heating element should be active in a heating cycle, wherein the heating cycle comprises a sequence of successive periods of the alternating current. The method further comprises the determination of a heating block within the heating cycle for the respective heating element, which heating block has precisely the number of periods of the alternating current as was determined for the respective heating element, and effecting that the respective heating element is active in the zero, one, or more periods of the heating cycle that are indicated by the determined heating block, and is inactive in the zero, one, or more periods of the heating cycle outside of the determined heating block.
The terms Fig., Figs., Figure, and Figures are used interchangeably in the specification to refer to the corresponding figures in the drawings.
In the following, examples are described in detail using the schematic drawing. Thereby shown are:
The printing device 100 depicted in
In the depicted example, the print group 140 of the printing device 100 comprises two print bars 102, wherein each print bar 102 can be used for printing with ink of a defined color, for example black, cyan, magenta, and/or yellow, and MICR ink if applicable. Different print bars 102 can be used for printing with respective different inks. Furthermore, the printing device 100 comprises at least one fixing or drying unit 150 that is configured to fix a print image printed onto the recording medium 120.
A print bar 102 can comprise one or more print heads 103 that, if applicable, are arranged in a plurality of rows side-by-side in order to print the dots of different columns 31, 32 of a print image onto the recording medium 120. In the example depicted in
In the embodiment illustrated in
The printing device 100 also comprises a control unit, for example an activation hardware and/or a controller, that is configured to drive actuators of the individual nozzles 21, 22 of the individual print heads 103 of the print group 140 in order to apply the print image onto the recording medium 120 depending on print data. The print data can respectively indicate, for each nozzle 21, 22, i.e. for each column 31, 32 of the print image and for each line of the print image, whether an ink ejection should take place or not, and if applicable what quantity of ink should be ejected.
As presented above, the printing device 100 can comprise a drying unit 150 that is configured to dry the recording medium 120 after application of the ink by the one or more print bars 102, and therewith to fix the applied print image onto the recording medium 120. For this purpose, the drying unit 150 can be controlled by the control unit 101 of the printing device 100. For example, the drying can take place depending on the quantity of the applied ink and/or depending on a type of the recording medium 120. For example, the temperature and/or the volumetric flow of the gaseous drying medium can be adapted depending on the quantity of the applied ink and/or depending on a type of the recording medium 120. In particular, the temperature and/or the volumetric flow of the gaseous drying medium can be set and/or adapted depending on a measured value of the temperature of the unprinted recording medium 120. Alternatively or in combination, the temperature of the recording medium 120 in the printed region can also be measured. The temperature of the recording medium 120 for an unprinted region can then be calculated by means of the ink quantity applied there, the grammage, the printing speed, and/or the nozzle box pressure or the drying module pressure.
The drying unit 150 depicted in
A contactless float drying by means of a forced convection can thus be used to dry a recording medium 120. As depicted in
The quantity of thermal energy that is supplied to the recording medium 120 to dry a print image within the drying unit 150 can be set, in particular can be controlled and/or regulated, such that on the one hand the print image is reliably and efficiently dried or fixed, and on the other hand an optimally small negative effect on the recording medium 120 is produced. In order to enable an optimally short drying route, it is advantageous to bring the temperature of the recording medium 120 optimally close to a defined limit temperature during the drying process. On the other hand, the limit temperature should not be exceeded, in order to avoid damage to the recording medium 120. Given paper, for example, the limit temperature can be at approximately 160° C.
The drying unit 150 can comprise a temperature sensor 151a that is configured to acquire sensor data with regard to the temperature of the recording medium 120. In this document, the sensor data of the temperature sensor 151 are also referred to as temperature data. The temperature sensor 151 can be arranged at a defined distance above the edge of the recording medium 120. An unprinted measurement stripe with a defined width, for example 12 cm, can be provided at the edge of the recording medium 120 in order to enable the temperature sensor 151 to at least intermittently acquire temperature data, i.e. measured values, with regard to the temperature of the unprinted recording medium 120.
A control unit 101, 161 of the drying unit 150 can be configured to operate the one or more drying modules 160 of the drying unit 150 depending on the temperature data. Temperature data with regard to the unprinted recording medium 120, in particular with regard to the unprinted measurement stripes, are thereby preferably used in order to effect an optimally precise and robust control and/or regulation of the one or more drying modules 160.
The phase-offset opening and closing of the individual switching elements 175 can lead to a non-uniform loading of the three-phase alternating current supply network, and thus to an additional adjustable short, during the period in which the heating element 162 is activated or deactivated. Consequently, it is typically advantageous to reduce the number of activations and deactivations of the individual heating elements 162 of a drying unit 150 in order to reduce the loading of the supply network that is produced by the drying unit 150.
To operate the heating elements 162 of the individual drying modules 160 of the drying unit 150, a respective measured value of the temperature of the recording medium 120 can be acquired at a defined measuring frequency, for example 1 Hz, using the temperature sensor 151 of the drying unit 150. The nominal temperature for the individual drying modules 160 can be determined on the basis of the measured value of the temperature, from which nominal temperature a control value for the heating element 162 of the respective drying module 160 can be determined under consideration of the respective real temperature which, for example, is detected by the temperature sensor 166 of the respective drying module 160. The control value can indicate for what portion of a heating cycle the heating element 162 of the respective drying module 160 should be active. A heating cycle can thereby extend beyond a defined number N of successive full or half-periods of the alternating current, in particular of the three-phase alternating current. For example, a heating cycle can comprise N=25 full periods or N=50 half-periods. The control value for a heating element 162 can thus indicate for how many full or half-periods of a heating cycle the heating element 162 should be active. In other words, the control value for a heating element 162 can indicate the number T of full or half-periods of a heating cycle in which the heating element 162 should be active.
A respective control value that indicates for how many full or half-periods of a heating cycle the respective heating element 162 should be active can thus be determined repeatedly, in particular periodically with a defined control frequency, for the individual heating elements 162 of the drying unit 150. For example, the activation matrix 200 depicted in
The use of the activation matrix 200 depicted in
The activation of the individual heating elements 162 can in particular be optimized in that
A respective block 206 of periods 201 that has a number T of periods 201 dependent on the control value L can thus be defined for the individual heating elements 162. The blocks 306 of the individual heating elements 162 can be arranged in chronological succession within the heating cycle, such that the block 306 of the second heating element 162 directly follows the block 306 of the first heating element 162, followed by the block 306 of the third heating element 162 etc. If a block 306 reaches the end of the heating cycle, the remaining portion of this block 306 can be continued again at the start of the heating cycle. The respective cumulative sum S of active periods 201, and the offset V of the respective block 306 within the heating cycle, are specified in the activation matrix 300 from
By sequentially stringing together the active and/or heating blocks 306 of the individual heating elements 162, as described above, it can be effected that the number R 305 of active heating elements 162 within the individual periods 201 of the heating cycle remains nearly constant. As a result of this, a nearly constant power consumption of the drying unit 150 can be effected over the time of a heating cycle.
For each drying module 160, a calculation can thus initially be made of how many full waves 201 need to be activated in the cycle in order to achieve the heating power requested by the respective drying module 160. Since the cycle in the shown example consists of N=25 full waves 201, the power levels may be activated in 4%-steps between 0% and 100% of the maximum available heating power.
In the depicted example, the heating element 162 of the first drying module 160 has a 4% duty cycle, which means that T=1 full wave 201 is to be driven. The heating element 162 of the second drying module 160 should be driven with an 8% duty cycle, thus with T=2 full waves, etc.
The heating element 162 of the first drying module 160 is activated at the 0th full wave of the heating cycle, and the heating element 162 of the second drying module 160 is activated when the heating element 162 of the first drying module 160 is deactivated, thus at the 1st full wave of the heating cycle. The heating element 162 of the third drying module 160 starts at the 3rd full wave and ends with the 12th full wave. The heating element 162 of the fourth drying module 160 starts at the 13th full wave and ends with the 22nd full wave. The heating element 162 of the fifth drying module 160 starts at the 23rd full wave and ends with the 24th full wave, the last full wave of the heating cycle. Since only 2 of the 9 necessary full waves for this heating element 162 are thereby considered, the 7 as of yet unconsidered full waves are started again with full wave 0 of the heating cycle and end with full wave 6. This means that duty cycles after the 24th full wave, i.e. at the end of the heating cycle, are transferred forward, i.e. to the start of the heating cycle.
The table 300 is filled up to the last drying module 160 of the drying unit 150. Under certain circumstances, full waves of the heating cycle in which no further heating elements 162 need to be activated any more remain at the end.
The different rows of the table 300 depicted in
When which drying module 160 is activated is entered in the following columns. How many nozzle boxes are activated simultaneously in the corresponding full wave is in the last row.
Via the described method, it is ensured that a switched-off heating element 162 is activated when a different heating element 162 is deactivated and that, in every full wave 201, optimally the same number of heating elements 162—for example 4 or 3 heating elements 162—are active at the end of the cycle.
A device 101, 161 is thus described for controlling a plurality of heating elements 162 of a drying unit 150 to dry a recording medium 120 printed to by a printing device 100. The plurality of heating elements 162 can, for example, comprise M=4 or more, or M=8 or more, or M=12 or more heating elements 162. The drying unit 150 can comprise a plurality of drying modules 160 that are arranged along a drying route, for example, as described in conjunction with
The device 101, 161 is configured to determine, for each of the plurality of heating elements 162, a respective number T of periods 201 of the alternating current for which the respective heating element 162 should be active in a heating cycle. A heating cycle can thereby comprise a sequence of successive full or half-periods 201 of the alternating current. For every single heating element 162, the fraction L of periods 201 of the heating cycle in which the respective heating element 162 should be active can thus be determined.
A heating cycle can, for example, comprise N periods 201 of the alternating current, for instance N=10 or more periods 201, or N=20 or more periods 201. For example, for how many of the N periods 201 the respective heating element 162 should be active can be determined for every single heating element 162.
The device 101, 161 can be configured to determine a respective nominal temperature for the respective heating element 162, in particular based on a measured value of the temperature of the recording medium 120, for each of the plurality of heating elements 162. Furthermore, a respective real temperature can be determined for the respective heating element 162, in particular using a temperature sensor 166 for the respective heating element 162. The number T of periods 201 of the alternating current for which the respective heating element 162 should be active in the heating cycle can then be determined precisely on the basis of the nominal temperature and on the basis of the real temperature, in particular using a regulator.
Furthermore, the device 101, 161 can be configured to determine, for each of the plurality of heating elements 162, a respective heating block 306 within the heating cycle for the respective heating element 162, wherein the heating block 306 has precisely the number T of periods 201 of the alternating current as was determined for the respective heating element. In other words, the periods 201 in which the respective heating element 162 should be active can respectively be merged into a contiguous heating block 306.
The device 101, 161 can thereby be configured to determine the heating block 306 for a heating element 162 such that the heating block 306 corresponds, in particular precisely corresponds, to a contiguous section of the sequence of successive periods 201 of the heating cycle that has precisely the number T of periods 201 of the alternating current as was determined for the heating element 162. Alternatively, the device 101, 161 can be configured to determine the heating block 306 for a heating element 162 such that the heating block 306 is composed of a first partial section from the sequence of successive periods 201 of the heating cycle at the start of the heating cycle and a second partial section from the sequence of successive periods 201 of the heating cycle at the end of the heating cycle, so that the first partial section and the second partial section together have precisely the number T of periods 201 of the alternating current as was determined for the heating element 162.
As was already explained further above, the heating cycle can have a sequence of N periods 201 of the alternating current or correspond to a sequence of N periods 201 of the alternating current. The individual periods 201 can be identifiable with an index number n=0, . . . , N−1 within the sequence of periods 201.
The device 101, 161 can then be configured to select, for the heating block 306 for a heating element 162 for which a number T of periods 201 has been determined, a contiguous section of T directly successive periods 201 from the sequence of N periods 201. Alternatively, the device 101, 161 can be configured to select, for the heating block 306 for a heating element 162, a first partial section from the periods 201 n=0, . . . , K at the start of the heating cycle, and a second partial section of the periods 201 n=Q, . . . , N−1 at the end of the heating cycle, such that K+N−Q+1=T.
A respective contiguous heating block 306 with T successive periods 201 can thus be established for every single heating element 162, wherein T is the determined number T of periods 201 for the respective heating element 162. A contiguous heating block 306 can thereby also be created via a “modulo” connection between the end of the heating cycle and the start of the heating cycle.
The device 101, 161 is also configured to effect that the respective heating element 162 is active in the zero, one, or more—i.e. in the T—periods 201 of the heating cycle that are indicated by the determined heating block 306, and is inactive in the zero, one, or more—i.e. in the N−T—periods 201 of the heating cycle outside of the determined heating block 306.
A device 101, 161 is thus described that is designed to activate the different heating elements 162 of a drying unit 150 respectively per block within a heating cycle in order to enable an operation of the drying unit 150 that is particularly power-efficient and gentle on the mains.
The heating elements 162 can be operated accordingly in successive heating cycles. An long-term, stable, and efficient operation of the drying unit 150 can thus be enabled.
The device 101, 161 can thus be configured to determine and/or arrange the plurality of heating blocks 306 for the corresponding plurality of heating elements 162 such that at least a portion of the plurality of heating elements 162 is activated precisely once within the heating cycle, in particular at the start of the determined heating block 306 for the respective heating element 162, and is deactivated precisely once, in particular at the end of the determined heating block 306 for the respective heating element 162. Alternatively or additionally, the device 101, 161 can be configured to determine and/or arrange the plurality of heating blocks 306 for the corresponding plurality of heating elements 162 such that each of the plurality of heating elements 162 is activated at most twice and deactivated at most twice within the heating cycle. A particularly low mains loading can be effected via the limited number of activations or deactivations of the individual heating elements 162.
The device 101, 161 can be configured to arrange the plurality of heating blocks 306 for the corresponding plurality of heating elements 162 in a distributed manner within the heating cycle such that the respective number of active heating elements 162 in the individual periods 201 of the sequence of periods 201 of the heating cycle assumes either a whole-number value R or a whole-number value R−1 for all periods 201 of the sequence of periods 201 of the heating cycle.
In other words, the heating blocks 306 of the individual heating elements 162 can be distributed within the heating cycle such that, if possible, the same number R of heating elements 162 is always active in the individual periods 201 of the heating cycle, and thus the heating power consumed by the drying unit 150 is constant over time. As an exception, the number R−1 of active heating elements 162 can be acceptable in one or more periods 201 since, due to the values of N, M, and T, where applicable no completely uniform distribution of the heating power to be consumed is possible.
Via such a uniform distribution of the heating blocks 306, the power efficiency of the drying unit 150 can be increased further, and the loading of the supply network can be further reduced.
The individual heating elements 162 of the plurality of heating elements 162 can be identifiable with an index number m=1, . . . , M within the drying unit 150. The index number m can, if applicable, indicate the position of the heating element 162 along the drying route of the drying unit 150. The device 101, 162 can be configured to arrange the heating blocks 306 of the M heating elements 162 using one or more of the following rules:
The individual heating blocks 306 can thus be arranged sequentially in the heating cycle. Upon achieving the end of the heating cycle, a “modulo” connection to the start of the heating cycle can thereby be effected so that a remaining heating block 306 can at least in part be placed at the start of the heating cycle again. The individual periods 201 of the heating cycle can thus, if applicable, be populated R times or (R−1) times with heating blocks 306 so that R or R−1 heating elements 162 are operated simultaneously in the individual periods 201. A uniform distribution of the heating blocks 306 can be particularly reliably effected via the aforementioned distribution method.
The device 101, 161 can be configured to determine and/or arrange the plurality of heating blocks 306 for the corresponding plurality of heating elements 162 such that each of the plurality of heating elements 162 is activated or deactivated at most once within any full period 201 of the heating cycle. The activation or the deactivation thereby preferably takes place at a zero crossing of the respective full period 201. The mains loading by the drying unit 150 can thus be further reduced.
Furthermore, a drying unit 150 and/or a printing device 100 that comprise the device 101, 161 are described in this document.
The method 400 comprises, for each of the plurality of heating elements 162, the determination 401 of a respective number T of periods 201 of the alternating current for which the respective heating element 162 should be active in a heating cycle, wherein the heating cycle comprises a sequence of N successive periods 201 of the alternating current. In what fraction L of the heating cycle the respective heating element 162 should be activated can thus be determined. This can be determined on the basis of a current measured value of the temperature of the recording medium 120 within the drying unit 150.
Furthermore, the method 400 comprises the determination 402 of a heating block 306 within the heating cycle for the respective heating element 162, wherein the heating block 306 respectively has precisely the number T of periods 201 of the alternating current that was determined for the respective heating element 162. Precisely one contiguous heating block 306 that comprises a section of the sequence of N successive periods 201 of the heating cycle is preferably determined for each heating element 162. The second can thereby, if applicable, be composed of two partial sections that are arranged at the end or at the start of the heating cycle, and that thus connect via a “modulo” operation that links the end of the heating cycle with the start of the heating cycle.
The method 400 also comprises effecting 403 that the respective heating element 162 is active in the zero, one, or more—i.e. in the T—periods 201 of the heating cycle that are indicated by the determined heating block 306, and is inactive in the zero, one, or more—i.e. in the N−T—periods 201 of the heating cycle outside of the determined heating block 306. The individual heating elements 162 can thus be respectively activated for all T periods 201 from the respective heating block 306, and be inactive for all N−T periods 201 outside of the respective heating block 306.
An operation of a drying unit 150 that is particularly power-efficient and gentle on the mains can be enabled via the measures described in this document.
Embodiments may be implemented in hardware (e.g., circuits), firmware, software, or any combination thereof. Embodiments may also be implemented as instructions stored on a machine-readable medium, which may be read and executed by one or more processors. A machine-readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computer). For the purposes of this discussion, the terms “controller”, “control unit” or “device for controlling” shall be understood to be circuit(s) or processor(s), or a combination thereof, including memory storing instructions. A circuit includes an analog circuit, a digital circuit, data processing circuit, other structural electronic hardware, or a combination thereof. A processor includes a microprocessor, a digital signal processor (DSP), central processor (CPU), application-specific instruction set processor (ASIP), graphics and/or image processor, multi-core processor, or other hardware processor.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2022 122 204.7 | Sep 2022 | DE | national |
