Image formation device

Abstract

To provide an image formation device which appropriately detects a failure of a temperature sensor of a dryer at comparatively low cost.SOLUTION: A dryer 7 dries ink in a print sheet where an image is formed by recording heads 1a to 1d, by a heater 7a. A temperature sensor 11 measures the temperature of the heater. A controller lowers output of the heater 7a when the temperature measurement value of the temperature sensor 11 becomes a target upper limit value, and increases output of the heater 7a when the temperature measurement value of the temperature sensor 11 becomes a target lower limit value. Furthermore, the controller determines that the temperature sensor 11 is failed, when the temperature measurement value does not become a target lower limit value, until lapsed time from a time point when the temperature measurement value reaches a target upper limit value, and the output of the heater 7a is lowered exceeds a predetermined threshold.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus. [Background technology]

[0002] One inkjet printer is equipped with a drying device that uses a heater to dry the ink on a print sheet after printing.The drying device is equipped with a temperature sensor that measures the temperature of the heater (such as the temperature of the air heated by the heater), controls the temperature of the heater according to the temperature measured by the temperature sensor, and furthermore, is equipped with a thermostat that cuts off the power supply to the heater when the temperature exceeds an allowable value due to a malfunction of the temperature sensor or the like (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-13297 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the inkjet printer requires a separate thermostat to detect temperature sensor failure, which increases the cost of the device. Also, if the thermostat fails, the temperature sensor failure will not be detected, causing the heater temperature to rise excessively, which could cause the drying device or other equipment to malfunction.

[0005] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an image forming apparatus that can appropriately detect a failure of a temperature sensor in a drying device at a relatively low cost. [Means for solving the problem]

[0006] The image forming apparatus according to the present invention includes a recording head that ejects ink to form an image to be printed on a print sheet, a sheet transport unit that transports the print sheet, a drying device that includes a heater and that dries the ink on the print sheet on which the image has been formed by the recording head using the heater, a temperature sensor that measures the temperature of the heater, and a controller that controls the sheet transport unit and the recording head to print the image at a predetermined print speed and controls the heater of the drying device in accordance with the temperature measurement value of the temperature sensor.The controller (a) reduces the output of the heater when the measured temperature value reaches a target upper limit, and increases the output of the heater when the measured temperature value reaches a target lower limit, and (b) determines that the temperature sensor is faulty if the measured temperature does not reach the target lower limit before the elapsed time from when the measured temperature value reached the target upper limit and the heater output was reduced exceeds a predetermined threshold. [Effects of the Invention]

[0007] According to the present invention, an image forming apparatus that can appropriately detect a failure of a temperature sensor in a drying device can be obtained at a relatively low cost.

[0008] The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing an image forming apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram showing the electrical configuration of the image forming apparatus 10 according to the embodiment of the present invention. [Figure 3] FIG. 3 is a diagram illustrating changes in the measured temperature values ​​corresponding to the output control of the heater 7a in the image forming apparatus 10 shown in FIGS. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0011] Fig. 1 is a diagram showing an image forming apparatus according to an embodiment of the present invention. The image forming apparatus 10 shown in Fig. 1 is a device such as a printer, copier, facsimile machine, or multifunction device, and in this embodiment is equipped with a line-head inkjet color printing mechanism.

[0012] The image forming apparatus 10 shown in FIG. 1 includes a print engine 10a and a sheet conveying unit 10b. The print engine 10a deposits ink on a print sheet 101 to physically print an image to be printed on the print sheet 101. For example, an ink cartridge is detachably attached to the print engine 10a, and the print engine 10a performs printing using ink supplied from the ink cartridge. The sheet conveying unit 10b is a conveying device that conveys the print sheet 101 before printing to the print engine 10a and conveys the print sheet 101 after printing to an output tray 10c via a drying device 7.

[0013] In this embodiment, print engine 10a is equipped with line-head type recording heads 1a to 1d corresponding to four ink colors: cyan, magenta, yellow, and black. Recording heads 1a to 1d eject ink of the corresponding ink color from nozzles to form an image to be printed on print sheet 101. Note that a monochrome image forming device has only one recording head.

[0014] In this embodiment, the sheet conveying section 10b includes a circular conveying belt 2 arranged opposite the print engine 10a and conveying the print sheet 101, a drive roller 3, a driven roller 4, and a tension roller 4a around which the conveying belt 2 is suspended, an adsorption roller 5 that nips the print sheet 101 together with the conveying belt 2, a subsequent conveying belt 6, and a drying device 7.

[0015] A drive roller 3, a driven roller 4, and a tension roller 4a rotate the conveyor belt 2. The suction roller 5 nips the print sheet 101 conveyed from a paper feed cassette 20 (described later). The nipped print sheet 101 is then conveyed by the conveyor belt 2 to the printing positions of the recording heads 1a to 1d in order, where an image of each color is printed by the recording heads 1a to 1d. The sheet sensor 2a detects the passage of the print sheet 101, and the current position of the print sheet 101 on the conveyance path is determined based on the detection timing. The image is then printed at the appropriate position on the print sheet 101. After printing, the print sheet 101 is discharged to a discharge tray 10c or the like by the subsequent conveyor belt 6. At this time, the print sheet 101 onto which the ink has been discharged is dried by a drying device 7.

[0016] Specifically, the drying device 7 includes a heater 7a, which dries the ink on the print sheet on which the image is formed by the recording heads 1a to 1d.

[0017] The drying device 7 is provided with a temperature sensor 11. The temperature sensor 11 measures the temperature of the heater 7a (such as the temperature of the heating element in the heater 7a and the temperature of the air heated by the heating element in the heater 7a) and outputs the measured temperature value.

[0018] A sheet suction section 8 is disposed along the sheet transport path. Negative pressure is applied to the sheet suction section 8, causing the print sheet 101 to be attracted to the transport belt 2 via the sheet suction holes.

[0019] Furthermore, the sheet transport unit 10b is equipped with a paper feed cassette 20 as a paper feed source. The paper feed cassette 20 stores print sheets 101, and a lift plate 21 pushes the print sheets 101 upward to abut against a pickup roller 22. The print sheets 101 placed in the paper feed cassette 20 are picked up one by one from above by the pickup roller 22 onto a paper feed roller 23. The paper feed roller 23 transports the print sheets 101 fed from the paper feed cassette 20 by the pickup roller 22 onto a transport path one by one.

[0020] Conveyance rollers 27 convey the print sheet 101 on a predetermined conveyance path. When the conveyed print sheet 101 is detected by a registration sensor 28a, registration rollers 28 temporarily stop the print sheet 101 and convey the print sheet 101 to the print engine 10a (specifically, to the nip position between the attraction roller 5 and the conveyance belt 2) at the secondary paper feed timing. The secondary paper feed timing is specified by a controller 75 (described later) so that an image is formed at a specified position on the print sheet 101.

[0021] Fig. 2 is a block diagram showing the electrical configuration of image forming apparatus 10 according to the embodiment of the present invention. As shown in Fig. 2, image forming apparatus 10 includes a printing device 71 having the mechanical configuration shown in Fig. 1, as well as an operation panel 72, a storage device 73, an outside air temperature sensor 74, and a controller 75.

[0022] The operation panel 72 is arranged on the surface of the housing of the image forming device 10 and is equipped with a display device 72a such as an LCD display and an input device 72b such as hard keys or a touch panel, and displays various messages to the user on the display device 72a and accepts user operations on the input device 72b.

[0023] The storage device 73 is a non-volatile storage device (such as a flash memory or a hard disk drive) that stores data, programs, and the like required for controlling the image forming apparatus 10.

[0024] The outside air temperature sensor 74 is a temperature sensor that measures the outside air temperature of the image forming apparatus 10. For example, the outside air temperature sensor 74 is set in a part of the housing of the image forming apparatus 10 where there is no heat generating element.

[0025] The controller 75 includes a computer that operates according to a program, an ASIC (Application Specific Integrated Circuit) that executes predetermined operations, and the like, and operates as various processing units. The computer includes a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), and the like, and performs various processes by loading programs stored in the ROM, storage device 73, etc. into the RAM and executing them on the CPU.

[0026] Specifically, the controller 75 controls the sheet transport unit 10b and the recording heads 1a to 1d to print an image at a predetermined print speed, and also controls the heater 7a of the drying device 7 according to the temperature measurement value of the temperature sensor 11.

[0027] Fig. 3 is a diagram illustrating changes in the temperature measurement value corresponding to the output control of the heater 7a in the image forming apparatus 10 shown in Fig. 1 and Fig. 2. Specifically, as shown in Fig. 3, when the temperature measurement value of the temperature sensor 11 reaches the target upper limit, the controller 75 reduces the power supplied to the heater 7a to reduce the output of the heater 7a, and when the temperature measurement value of the temperature sensor 11 reaches the target lower limit, the controller 75 increases the power supplied to the heater 7a to increase the output of the heater 7a. This maintains the temperature of the heater 7a approximately within the allowable range.

[0028] 3, the controller 75 monitors the elapsed time dt from the point at which the temperature measurement value of the temperature sensor 11 reaches the target upper limit and the output of the heater 7a is reduced, and if the temperature measurement value does not reach the target lower limit before the elapsed time dt exceeds a predetermined threshold Tm, it determines that the temperature sensor 11 has failed. If it is determined that the temperature sensor 11 has failed, the controller 75 may, for example, stop the supply of power to the heater 7a, stop the print process, or notify the user.

[0029] For example, the predetermined threshold Tm is set based on the number of print sheets 101 passing through the heater 7a during the elapsed time and the printing rate of the print sheets 101 passing through the heater 7a during the elapsed time (specifically, the average or total printing rate). Here, the greater the number of print sheets 101, the lower the predetermined threshold Tm is set, and the higher the printing rate of the print sheets, the lower the predetermined threshold Tm is set. For example, the predetermined threshold Tm is derived by estimating the number of print sheets 101 and the printing rate based on the print request up until the start of the elapsed time dt.

[0030] Furthermore, in this embodiment, since the outside air temperature sensor 74 is provided, the predetermined threshold value Tm is set based on the number of print sheets, the print rate of the print sheets, and the outside air temperature measured by the outside air temperature sensor 74. Here, the greater the number of print sheets 101, the lower the predetermined threshold value Tm is set; the higher the print rate of the print sheets, the lower the predetermined threshold value Tm is set; and the lower the measured outside air temperature, the lower the predetermined threshold value Tm is set.

[0031] Next, the operation of the image forming apparatus 10 will be described.

[0032] When the controller 75 receives a print request, it generates image data for the image to be printed specified by the print request and causes the sheet transport unit 10b to start transporting the print sheet 101. As the print sheet 101 passes through the print engine 10a, the controller 75 controls the print recording heads 1a to 1d to eject ink onto the print sheet 101 in accordance with the image to be printed. The print sheet 101 then passes through the drying device 7 and is discharged.

[0033] During the above-mentioned printing process, the controller 75 monitors the temperature measurement value of the temperature sensor 11 as described above, and when the measured temperature value reaches the target upper limit, it reduces the output of the heater 7a, and when the measured temperature value reaches the target lower limit, it increases the output of the heater 7a. Here, the output of the heater 7a is controlled at two predetermined values: high output and low output.

[0034] Furthermore, when the temperature measurement value of the temperature sensor 11 reaches the target upper limit and the controller 75 reduces the output of the heater 7a, the controller 75 monitors the time elapsed from that point, and if the temperature measurement value does not reach the target lower limit before the elapsed time dt exceeds a predetermined threshold Tm, the controller 75 determines that the temperature sensor 11 is malfunctioning. If the controller 75 determines that the temperature sensor 11 is malfunctioning, the controller 75 may, for example, stop the supply of power to the heater 7a, stop the print process, or notify the user. On the other hand, if the temperature measurement value reaches the target lower limit before the elapsed time dt exceeds the predetermined threshold Tm, the controller 75 does not determine that the temperature sensor 11 is malfunctioning, and the print process continues.

[0035] As described above, according to the above embodiment, the drying device 7 uses the heater 7a to dry the ink on the print sheet on which an image has been formed by the recording heads 1a to 1d. The temperature sensor 11 measures the temperature of the heater. The controller 75 reduces the output of the heater 7a when the temperature measurement value of the temperature sensor 11 reaches the target upper limit, and increases the output of the heater 7a when the temperature measurement value of the temperature sensor 11 reaches the target lower limit. Furthermore, the controller 75 determines that the temperature sensor 11 is faulty if the measured temperature does not reach the target lower limit by the time the elapsed time dt from the time the measured temperature reached the target upper limit and the output of the heater 7a was reduced exceeds the predetermined threshold Tm.

[0036] This allows a failure of the temperature sensor 11 to be detected without providing a separate component (such as a thermostat) for detecting a failure of the temperature sensor 11, so that a failure of the temperature sensor 11 of the drying device 7 can be appropriately detected at a relatively low cost.

[0037] It should be noted that various changes and modifications to the above-described embodiments will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the spirit and scope of the subject matter and without diminishing its intended advantages. In other words, it is intended that such changes and modifications be included within the scope of the claims. [Industrial Applicability]

[0038] The present invention is applicable to, for example, an inkjet type image forming apparatus. [Explanation of symbols]

[0039] 1a to 1d recording head 7 Drying equipment 7a Heater 10 Image forming device 10b Sheet transport section 11 Temperature sensor 74 Outside air temperature sensor 75 Controller

Claims

1. a recording head that ejects ink to form an image to be printed on a print sheet; a sheet conveying section for conveying the print sheet; a drying device including a heater, the drying device using the heater to dry the ink on the print sheet on which the image is formed by the recording head; a temperature sensor for measuring the temperature of the heater; a controller that controls the sheet transport unit and the recording head to print the image at a predetermined print speed, and controls a heater of the drying device in accordance with the temperature measurement value of the temperature sensor; the controller (a) reduces the output of the heater when the measured temperature value exceeds a target upper limit value, and increases the output of the heater when the measured temperature value falls below a target lower limit value; and (b) determines that the temperature sensor is faulty if the measured temperature value does not fall below the target lower limit value until the elapsed time from when the measured temperature value exceeded the target upper limit value and the output of the heater was reduced exceeds a predetermined threshold value. An image forming apparatus comprising:

2. 2. The image forming apparatus according to claim 1, wherein the predetermined threshold is set based on the number of print sheets passing through the heater during the elapsed time and the printing rate of the print sheets passing through the heater during the elapsed time.

3. The predetermined threshold value is set lower as the number of print sheets increases, the predetermined threshold value is set lower as the printing rate of the print sheet increases; 2. The image forming apparatus according to claim 1, wherein:

4. an outside air temperature sensor for measuring the outside air temperature of the image forming apparatus; the predetermined threshold is set based on the number of print sheets passing through the heater during the elapsed time, the printing rate of the print sheets passing through the heater during the elapsed time, and the measured outside air temperature; 2. The image forming apparatus according to claim 1, wherein:

5. The predetermined threshold value is set lower as the number of print sheets increases, the predetermined threshold is set lower as the printing rate of the print sheet increases, The predetermined threshold value is set lower as the measured outside air temperature is lower; 5. The image forming apparatus according to claim 4, wherein:

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