JP7484271B2 - Image forming apparatus and method for controlling image forming apparatus - Google Patents

Description

The present invention relates to an image forming apparatus and a method for controlling an image forming apparatus.

As disclosed in Patent Document 1, there is a technology for detecting the temperature of the drying heater in large commercial inkjet printers. Until now, in large commercial cut-sheet inkjet printers, it has been common to detect the temperature of the drying heater by combining software detection (infrared sensor or thermistor) and hardware detection (thermostat). There is also technology that uses feedback of the software-detected temperature value to adjust the heater temperature and control the ON/OFF of the output.

However, in large commercial cut-sheet inkjet printers that use software detection by an infrared sensor to feed back values to adjust the heater temperature and control the output on and off, there is a problem in that if the paper is transported out of alignment, the infrared sensor's laser can be blocked by the paper, preventing correct temperature detection (the sensor detects the paper temperature and erroneously detects that the temperature has dropped) and causing the heater temperature to reach an abnormal level (when the infrared sensor makes the aforementioned erroneous detection, it tries to raise the heater's temperature, which has already dropped, leading to abnormal heat generation), resulting in a malfunction that stops the printer due to hardware detection.

The present invention has been made in consideration of the above, and aims to prevent malfunctions in heater temperature detection caused by misalignment of paper transport.

In order to solve the above-mentioned problems and achieve the object, the present invention provides a printing apparatus comprising a medium transport unit that transports a medium, an imaging unit that forms an image on the medium, and a drying unit that dries the medium on which the image has been formed , wherein the drying unit has a heating unit that extends in a direction perpendicular to the medium transport direction and has black bands on both ends and is heated by a heater, and a temperature detection unit that detects the temperature of the black bands with an infrared sensor , and further comprises a memory unit that stores a normal lower limit, a normal upper limit, a dirt lower limit, a dirt upper limit, a media transport deviation lower limit, a media transport deviation upper limit, and a heater abnormality value as threshold values for the temperature difference between both ends of the heating unit, and a control unit that adjusts the temperature of the heating unit based on the temperature detected by the temperature detection unit .

The present invention has the advantage of being able to prevent malfunctions in heater temperature detection caused by misalignment of paper transport.

FIG. 1 is a diagram showing an example of a schematic configuration of an image forming apparatus. FIG. 2 is a diagram showing an example of the configuration of a drying device of an image forming apparatus. FIG. 3 is a diagram showing an example of the transport of paper in the drying device. FIG. 4 is a diagram showing an example of a case where a conveyance deviation of a sheet occurs in a drying device of an image forming apparatus. FIG. 5 is a diagram showing an example of the transport of paper in the drying device. FIG. 6 is a diagram showing an example of a case where a sheet skew occurs in a drying device of an image forming apparatus. FIG. 7 is a diagram showing an example of the transport of paper in the drying device. FIG. 8 is a diagram showing the temperature difference of the infrared sensor when the paper is skewed and when the paper is conveyed with a deviation. FIG. 9 is a diagram showing an example of the configuration of a drying device for a conveying belt. FIG. 10 is a diagram showing an example of the conveyance of a sheet in a belt-conveying drying device. FIG. 11 is a diagram illustrating an example of a hardware configuration of a control unit included in the image forming apparatus. FIG. 12 is a diagram showing the relationship between the temperature information stored in the storage unit of the image forming apparatus and the detected temperature. FIG. 13 is a flowchart showing an example of a process performed by the control unit of the image forming apparatus.

The image forming apparatus of this embodiment will be described. This embodiment is an inkjet printer having an ink ejection device and an ink drying device, and has the following features. In a heat roller temperature detection circuit using an infrared sensor, the sensor irradiating the heat roller with infrared rays cannot detect the temperature correctly because the paper blocks the infrared laser due to paper transport misalignment. This phenomenon causes erroneous detection by the hardware detection unit due to an abnormality in the heater temperature. The image forming apparatus of this embodiment can detect temperature correctly, and can prevent erroneous detection by the hardware detection unit due to an abnormality in the heater temperature. Furthermore, as a result of preventing transport misalignment, it becomes possible to correctly detect the heater temperature using the infrared sensor, and therefore the paper can be appropriately heated by temperature feedback.

First, the general configuration of the image forming apparatus according to this embodiment will be described. FIG. 1 is a diagram showing an example of the general configuration of the image forming apparatus. The image forming apparatus 1 according to this embodiment includes a paper transport unit 19 which is a medium transport unit, a pre-coating device 12, an image forming unit 13 which is an image creating unit, a drying device 14 which is a drying unit, a control unit 15, and a memory unit 16.

The paper transport unit 19 is a roller that transports the medium. In this embodiment, the medium is exemplified as paper 101. The pre-coating device 12 applies pre-coating liquid 18 to both sides or one side of the paper 101. The pre-coating liquid 18 has the function of agglomerating the coloring material components in the ink and making the ink more easily fixed. By applying pre-coating liquid to the paper 101 before image formation, a high-quality image can be formed even when using paper 101 on which ink is less likely to fix.

The image forming unit 13 forms an image on the paper 101. In this embodiment, the image forming unit 13 forms an image by ejecting black (K), cyan (C), magenta (M), and yellow (Y) inks onto the surface of the paper 101.

The drying device 14 dries the paper 101 on which an image has been formed by the image forming unit 13 by heating it. Note that drying has the effect of blending the ink adhering to the paper 101 and fixing the ink adhering to the medium P.

Figure 2 is a diagram showing an example of the configuration of a drying device of an image forming apparatus. Figure 3 is a diagram showing an example of the transport of paper in the drying device. The drying device 14 has heat rollers 102, which are multiple heating units arranged along the transport direction of paper 101. The heat roller 102 is shaped to extend in a direction perpendicular to the transport direction. Two heaters 103 and 106 are inserted into the heat roller. The heaters 103 and 106 heat the heat roller 102. When the heater length becomes long, it is common to connect two filaments to extend the filament. It is known that the heater temperature at the joint where the filaments are joined is lower than the heater temperature outside the joint. Therefore, instead of extending the heater, the temperature of the heat roller 102 is made uniform by dividing it into two heaters, heater 103 and heater 106, to prevent color unevenness and drying unevenness caused by temperature unevenness.

The heat roller 102 is generally made of a material with high thermal conductivity, such as aluminum. In addition, since the heat roller 102 made of aluminum or the like comes into contact with the paper 101, the surface (including the surface treatment) is prone to reflection. When the roller is irradiated with an infrared laser or the like from an infrared sensor described below, false detection occurs due to reflection. As a workaround for this, it is known to apply black paint with an emissivity of 1.0 to the laser irradiation area. Because the heat roller 102, which is the irradiating area, is a rotating roller, black bands 104 are provided on both ends of the heat roller 102. This prevents false detection due to reflection of the infrared laser.

As shown in FIG. 3, the paper 101 is mainly transported in a cut-sheet paper transport manner. It is generally transported by heat rollers 102 (or a belt transport with a belt wrapped around the heat rollers 102). (This is to make it easier to transfer heat to the paper.) In this format, a transport motor 131 rotates a transport belt 132.

The drying device 14 has multiple infrared sensors 105a1, 105a2, 105b1, 105b2, 105c1, 105c2, 105d1, and 105d2 that are temperature detection units. In the following description, the infrared sensors 105a1, 105a2, 105b1, 105b2, 105c1, 105c2, 105d1, and 105d2 are also referred to as infrared sensors 105 without distinction. The infrared sensors 105 measure the temperature of the heat roller 102 by irradiating the black bands 104 on both ends of the heat roller 102 with an infrared laser.

As shown in FIG. 2, the temperature of the heat roller 102 located most upstream in the conveying direction is measured by infrared sensors 105a1 and 105a2. The temperature of the heat roller 102 adjacent to it on the downstream side is measured by infrared sensors 105b1 and 105b2. The temperature of the heat roller 102 adjacent to it further downstream is measured by infrared sensors 105c1 and 105c2. The temperature of the heat roller 102 adjacent to it further downstream is measured by infrared sensors 105d1 and 105d2. The control unit 15 controls the heaters 103 and 106 based on the paper information or ink information stored in the memory unit 16 to set the temperature of the heat roller 102.

Figure 4 is a diagram showing an example of a case where a paper is conveyed in a drying device of an image forming apparatus. Figure 5 is a diagram showing an example of paper conveyance in a drying device. When a conveyance deviation (cut sheet paper) occurs, one of the black belts 104 provided at both ends of the heat roller 102 is entirely covered by the paper 101. Therefore, in the example shown in Figure 4, the paper 101 is caught between the infrared sensors 105a2, 105b2, 105c2, 105d2 and the black belt 104. At this time, since the infrared sensors 105a2, 105b2, 105c2, 105d2 detect the temperature of the paper edge, even if the temperature of the heat roller 102 is normal, the temperature detected by the infrared sensors 105a2, 105b2, 105c2, 105d2 is detected as a temperature value lower than the normal temperature. On the other hand, as shown in FIG. 5, infrared sensors 105a1, 105b1, 105c1, and 105d1 are not blocked by the paper 101, so they detect the normal temperature. Therefore, there is a difference in the temperature detection results measured at both ends of all heat rollers 102.

As a result of feeding back a low temperature value, an instruction is sent to the temperature control unit of the heat roller 102 to increase the temperature, which causes a temperature abnormality and leads to a false detection that the temperature protection thermostat 100 is turned off.

Next, we will explain temperature detection by the infrared sensor 105 when paper skew occurs, in which the paper 101 is inclined with respect to the normal transport path of the paper 101. Figure 6 is a diagram showing an example of when paper skew occurs in a drying device of an image forming apparatus. Figure 7 is a diagram showing an example of paper transport in the drying device.

When paper skew occurs, as shown in Figures 6 and 7, there are heat rollers 102 in which one of the black bands 104 at both ends is covered by the paper 101, and heat rollers 102 in which neither of the black bands 104 at both ends is covered by the paper. Therefore, in the example shown in Figure 6, the paper 101 is between the infrared sensors 105a1, 105b1, and 105c2 and the black bands 104. On the other hand, the black bands 104 at both ends of the most downstream heat roller 102 are not covered by the paper 101. At this time, a difference occurs in the results of temperature detection by the infrared sensors 105 that measure the temperatures at both ends, except for the heat roller 102 at the most downstream. In addition, among the infrared sensors 105a1, 105b1, 105c1, and 105d1 that detect the temperature on one side of the heat roller 102, there is an infrared sensor 105 that detects a different temperature from the others, and among the infrared sensors 105a2, 105b2, 105c2, and 105d2 that detect the temperature on the other side, there is an infrared sensor 105 that detects a different temperature from the others.

Figure 8 shows the temperature difference of the infrared sensor when the paper is skewed and when the paper is conveyed with a misalignment. As shown in Figure 8, when there is a temperature difference between both ends of all heat rollers 102, it can be determined that there is a conveyance misalignment. Also, when there is a temperature difference between both ends of some heat rollers 102, it can be determined that there is a paper skew.

One method for detecting paper skew is known to be the provision of a component for detecting the paper position. However, there are thermal issues within the drying device 14, making it impractical to add additional components. On the other hand, the image forming device 1 of this embodiment makes it possible to detect temperature and paper skew without adding additional components.

In this embodiment, the paper transport misalignment is explained in terms of roll transport using a heat roll, but the present invention is not limited to roll transport. For cut paper in a sheet-fed machine, belt transport may be used. This can also be applied to cases where the paper is skewed even in the case of belt transport. In the case of belt transport, it is possible to imagine a case where the black band is not attached to the heat roller. It is possible that the belt may block the temperature detection sensor. Figure 9 is a diagram showing an example of the configuration of a drying device for belt transport. Figure 10 is a diagram showing an example of paper transport within a drying device for belt transport. As shown in Figures 9 and 10, a black band may be attached to the transport belt for detection.

Figure 11 is a diagram showing an example of the hardware configuration of a control unit provided in an image forming apparatus. The control blocks are a temperature protection unit 17 which is a hardware detection circuit and a control unit 15 which is a software detection circuit. The temperature protection unit 17 cuts off the power supply to the heaters 103, 106 by hardware detection of the thermostat 100. The temperature protection unit 17 is a hardware circuit that also stops the heaters 103, 106 when the power supply to the heaters 103, 106 is cut off. The temperature protection unit 17 is a protection circuit that does not operate unless an abnormal temperature occurs.

After the heaters 103 and 106 are turned on, the control unit 15 detects the temperature using the infrared sensor 105 and sends the temperature information to the control circuit 111 and the CPU 112. Various setting information and various state information are stored in the memory unit 16 shown in FIG. 1. The control circuit 111 and the CPU 112 compare the temperature information from the infrared sensor 105 with the stored information and issue a command to the heater drive circuit 113 to achieve an appropriate temperature. The memory unit 16 is, for example, a storage device such as an HDD (Hard Disk Drive) or an SSD (Solid State Drive). The memory unit 16 also stores various data such as programs for the image forming device 1.

Figure 12 is a diagram showing the relationship between temperature information stored in the memory unit of the image forming device and the detected temperature. When a paper transport deviation occurs, it is not possible to determine whether it is due to a heater abnormality or a transport deviation based on the temperature difference detected by the infrared sensor 105 alone. Therefore, multiple threshold values are stored in the memory unit 16 for the temperature difference (absolute value) between both ends of the heat roller 102 shown in Figure 12. For example, the infrared sensor 105 may detect the temperature of a black band 104 covered by the paper 101 to determine the threshold value.

As shown in FIG. 12, the normal lower limit temperature (th1) is stored as a threshold value. The normal upper limit temperature/soil lower limit temperature (th2) is stored as a threshold value. The paper transport deviation lower limit temperature/soil upper limit temperature (th3) is stored as a threshold value. The paper transport deviation upper limit temperature/heater abnormality lower limit temperature (th4) is stored as a threshold value.

If the temperature difference between both ends of the heat roller 102 is between the normal lower limit temperature (th1) and the normal upper limit temperature/dirt lower limit temperature (th2), the control unit 15 determines that the difference is within the range of heater variation and that the heat roller 102 is in a normal state. If the temperature difference between both ends of the heat roller 102 is between the normal upper limit temperature/dirt lower limit temperature (th2) and the paper transport deviation lower limit temperature/dirt upper limit temperature (th3), the control unit 15 determines that the temperature difference is caused by the heat roller 102 being dirty by ink or ink mist. If the temperature difference between both ends of the heat roller 102 is between the paper transport deviation lower limit temperature/dirt upper limit temperature (th3) and the paper transport deviation upper limit temperature/heater abnormality lower limit temperature (th4), the control unit 15 determines that a transport deviation or paper skew has occurred. If the temperature difference between both ends of the heat roller 102 exceeds the paper transport deviation upper limit temperature/heater abnormality lower limit temperature (th4), the control unit 15 determines that a heater abnormality has occurred. At this time, thermostat 100 is left as is, assuming that CPU 112 may go out of control.

Figure 13 is a flow chart showing an example of processing by the control unit of the image forming apparatus. First, machine initialization starts turning on the heaters 103 and 106, initial temperature setting, and mainland detection (step S1). Next, if the black belt 104 has not reached the predetermined temperature th1 (step S2, No), the judgment of step S2 is repeated. If the black belt 104 has reached th1 (step S2, Yes), transport and printing of the paper 101 are started (step S3). Note that if the judgment of step S2 has been repeated a predetermined number of times, or if it is not possible to proceed to step S3 even after a predetermined time has passed, a process may be added in which the operation of the image forming apparatus 1 is stopped as a heater abnormality.

If the temperature difference between the black bands 104 at both ends of the heat roller 102 is between th1 and th2 (step S4, Yes) (see FIG. 12(a)), the image forming device 1 continues transporting and printing on the paper, and when transporting and printing are completed (step S5), the operation of the image forming device 1 is stopped.

If the temperature difference between the black bands 104 at both ends of the heat roller 102 is not between th1 and th2 (step S4, No) but is between th2 and th3 (step S6, Yes) (see Figure 12 (b)), the heat roller 102 is deemed dirty and a maintenance request is sent (step S7), and the process proceeds to step S5.

If the temperature difference between the black bands 104 at both ends of the heat roller 102 is not between th2 and th3 (step S6, No), but the temperature difference between the black bands 104 at both ends of all heat rollers 102 is between th3 and th4 (step S8, Yes) (see Figure 12 (c)), it is determined that there is a paper transport misalignment, and the operation of the image forming device 1 is stopped (step S9).

If the temperature difference between the black bands 104 at both ends of all heat rollers 102 is not between th3 and th4 (step S8, No), but the temperature difference between the black bands 104 at both ends of some heat rollers 102 is between th3 and th4 (step S10, Yes), it is determined that paper skew has occurred and the operation of the image forming device 1 is stopped (step S11).

If the temperature difference between the black bands 104 at both ends of some of the heat rollers 102 is not between th3 and th4 (step S10, No) but exceeds th4 (step S12, Yes), it is determined that there is a heater abnormality and the operation of the image forming device 1 is stopped (step S13).

In addition, step S10 for determining paper skew may also include a determination as to whether a different temperature is detected on one side of the heat roller 102 and whether a different temperature is detected on the other side. In addition, if there is no distinction between conveyance misalignment and paper skew, the determination may not be made separately between step S8 and step S10, and the operation of the image forming device 1 may be stopped if the temperature difference between the black bands 104 at both ends of the heat roller 102 is between th3 and th4.

REFERENCE SIGNS LIST 1 Image forming apparatus 12 Pre-coating device 13 Image forming section 14 Drying device 15 Control section 16 Memory section 17 Temperature protection section 19 Paper conveying section 100 Thermostat 101 Paper 102 Heat roller 103, 106 Heater 104 Black belt 111 Control circuit 112 CPU
113 Heater driving circuit 131 Conveyor motor 132 Conveyor belt

JP 2018-12323 A

Claims (8)

a medium transport unit that transports the medium;
an image forming unit for forming an image on the medium;
a drying section that dries the medium on which the image is formed;
Equipped with
the drying unit includes a heating unit that extends in a direction perpendicular to a transport direction of the medium, has black bands on both ends, and is heated by a heater, and a temperature detection unit that detects a temperature of the black bands by an infrared sensor;
a storage unit that stores a normal lower limit, a normal upper limit, a dirt lower limit, a dirt upper limit, a medium conveyance deviation lower limit, a medium conveyance deviation upper limit, and a heater abnormality value as threshold values of a temperature difference between both ends of the heating unit;
A control unit that adjusts the temperature of the heating unit based on the temperature detected by the temperature detection unit;
The image forming apparatus further comprises: 2 . The image forming apparatus according to claim 1 , wherein the control unit determines that the heater is abnormal when a temperature difference between both ends of the heating unit exceeds a lower limit temperature for a heater abnormality . The image forming device according to claim 1 or 2, characterized in that the control unit operates the medium conveying unit normally when the temperature difference between both ends of the heating unit is equal to or greater than the normal lower limit and less than the normal upper limit. The image forming apparatus according to any one of claims 1 to 3, characterized in that the control unit notifies the contamination of the heating unit when the temperature difference between both ends of the heating unit is equal to or greater than the lower contamination limit and less than the upper contamination limit. The heating section is provided in a plurality of rows along the conveying direction,
The image forming device described in any one of claims 1 to 4, characterized in that when there is a temperature difference between both ends of all of the heating sections and the temperature difference is greater than or equal to the lower limit of the media transport deviation and less than the upper limit of the media transport deviation, the control unit determines that the media has deviated from the normal transport path, notifies of the media transport deviation, and stops operation of the image forming device. The heating section is provided in a plurality of rows along the conveying direction,
The image forming device described in any one of claims 1 to 5, characterized in that when there is a temperature difference between both ends of some of the heating sections and the temperature difference is greater than or equal to the lower limit of the media transport deviation and less than the upper limit of the media transport deviation, the control unit determines that the media is skewed relative to the normal transport path, notifies of the media skew, and stops operation of the image forming device. The image forming device according to any one of claims 1 to 5, characterized in that the control unit determines that a heater abnormality has occurred when the temperature difference between both ends of the heating unit is equal to or greater than the heater abnormality value, notifies the user of the heater abnormality, and stops operation of the image forming device. A method for controlling an image forming apparatus including a medium transport unit that transports a medium, an imaging unit that forms an image on the medium, and a drying unit that dries the medium on which the image has been formed, the drying unit having a heating unit that extends in a direction perpendicular to a transport direction of the medium, has black bands on both ends, and is heated by a heater, and a temperature detection unit that detects the temperature of the black bands by an infrared sensor, the method comprising:
11. A control method for an image forming apparatus, comprising: determining that there is a transport deviation or a media skew in the medium when a predetermined temperature difference exists between both ends of the heating unit.

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