JP4808396B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to a heating control unit that controls a fixing roller that heats and fixes a toner image formed on a sheet to a target temperature, a sheet selection unit that selects a type or size of a sheet to be fed, and a copying operation. Fixing temperature switching means for switching the target temperature to a temperature different from the standard temperature based on the type or size of the paper selected by the paper selection means during execution, and size detection means for detecting the size of the fed paper The present invention relates to an image forming apparatus configured to include:

Conventionally, when an image is output using an image forming apparatus, a toner image formed on an output sheet is heated and fixed by a fixing roller that is controlled to be heated to a target temperature. The target temperature is controlled according to the size and thickness of the output paper to be fed, and the heat absorption capacity increases as the output paper becomes thicker. Therefore, it is necessary to set the target temperature high. For example, Patent Document 1 describes that a thick paper sensor or the like is installed in the paper feeding unit of the image forming apparatus and the target temperature is controlled according to the thickness of the output paper.
JP-A-9-90795

  However, the above-mentioned cardboard sensors are not practical, and in reality, the output sheet is an output sheet (standard sheet) having a general thickness or thicker than that by an input operation by the user. After the initial setting of whether it is (thick paper), image formation is performed by installing and feeding any one of the output papers. In particular, in the case of manual paper feed, there is a case where the output paper is changed from a thick paper to a standard paper during the continuous image formation on a plurality of output papers, or vice versa. Although frequently occurring, the fixing roller continues to be executed at the target temperature corresponding to the initially set output paper unless the initial setting is changed. In particular, if the output paper is a thick paper in the initial setting, and the target temperature of the fixing roller is set to be high, the output paper is changed from the thick paper to the standard paper during the image formation. When the heat sink capacity is below the assumed heat absorption capacity, the fixing roller is abnormally heated, the heater for heating the fixing roller is damaged, or the temperature fuse for protecting the heater is broken. It was.

  SUMMARY OF THE INVENTION In view of the above-described conventional drawbacks, an object of the present invention is to provide an image forming apparatus capable of preventing a failure caused by a mismatch between the type of output paper and fixing temperature control.

In order to achieve the above object, a first characteristic configuration of an image forming apparatus according to the present invention is a fixing for heating and fixing a toner image formed on a sheet as described in claim 1 of the document of the claims. The heating control means for controlling the heating of the roller to the target temperature, the paper selection means for selecting the type and size of the paper to be fed, and the paper selected by the paper selection means during the copying operation are standard paper. For example, the target temperature is switched to the standard temperature, and if the paper is thicker than the standard paper, the fixing temperature switching means for switching the target temperature to a temperature higher than the standard temperature and the size of the paper to be fed are detected. An image forming apparatus configured to include a size detecting unit configured to detect the size of the fixing unit while the fixing temperature switching unit switches the target temperature to a temperature higher than the standard temperature. Ri when the detected size is different from the size selected by the sheet selecting means is the target temperature from a temperature higher than the standard temperature to a point that is configured to re-switch to the standard temperature.

  With the above-described configuration, the fixing roller is controlled at a temperature higher than the standard temperature corresponding to the standard paper in order to form an image on a thick paper sheet that is generally thicker than the standard paper used for image formation. When the size of the output paper to be fed is different from the original, the output paper on which the image is formed is changed to the standard paper and is switched to the standard temperature. That is, when the size of the output paper to be fed is different from the initial size, if the output paper corresponding to the temperature of the fixing roller is not supplied, the fixing roller responds to the temperature of the fixing roller from the state where the fixing roller is abnormally heated. Even if the output paper is not supplied, the fixing roller is switched to a state where it does not heat abnormally. Even when the output paper size change is not necessarily a change in the output paper thickness, the fixing roller does not overheat reliably when there is a possibility that the paper has changed from a thick paper to a standard paper. By switching to, it is possible to prevent the occurrence of problems such as breakage of the heater and blown fuse.

  In the output paper, the standard paper is a paper having a thickness of about 80 to 110 μm, and the thick paper is a paper having a thickness of about 200 to 250 μm that is used for a postcard or the like. That is, the standard paper and the cardboard paper are distinguished by a thickness of about 150 μm.

  As described above, according to the present invention, it is possible to provide an image forming apparatus that can prevent a failure caused by a mismatch between the type of output paper and the fixing temperature control.

  The case where the image forming apparatus according to the present invention is applied to a digital copying machine will be described below. As shown in FIG. 1, a copying machine as an image forming apparatus performs an image reading unit 1 as an image reading unit that reads image data of a document, and performs predetermined processing on the document image data read by the image reading unit 1. An image processing unit 2 for generating output image data, an image output unit 3 as image output means for forming and outputting an image on the output paper 10 based on the output image data from the image processing unit 2, and a copying machine A mode setting key for setting operation modes of various jobs, a print switch for starting the set job, and the like are arranged, and an operation unit 4 having a touch panel type liquid crystal display unit on which setting information by the mode setting key is displayed. And so on.

  The image reading unit 1 is fed by a document tray 12 on which a document is placed, a document feeding unit (not shown) that feeds a document placed on the document tray 12, and a document feeding unit. A CCD linear sensor (not shown) for reading the image of the original is provided.

  The image output unit 3 includes an image forming unit 6 that forms a toner image on the photoconductor 60 based on the output image data, a transport unit 7 that transports the output paper 10 onto which the formed toner image is transferred, and a transfer unit. A fixing unit 8 for fixing the toner image on the output sheet 10 by being heated and melted by a fixing roller 8a heated to a predetermined temperature by a heater (not shown) inserted and installed therein and a temperature sensor (not shown). It is configured with.

  The image forming unit 6 is arranged in order around the photoconductor 60, the periphery of the photoconductor 60, and exposes the charged photoconductor 60 to uniformly corona charge the surface and forms an electrostatic latent image. Print head 62, developing unit 63 for developing toner by electrostatically adhering toner to the formed electrostatic latent image, transfer unit for transferring the toner image to the output paper 10, and removing residual toner after transfer And a neutralizing lamp 65 that lowers the residual potential on the surface of the photosensitive member to make it uniform. The developing unit 63 has four colors of cyan, magenta, yellow, and black so that a color image can be generated. Development blocks are arranged.

  The transport unit 7 feeds the output paper 10 one by one from a general paper feed cassette 11a in which output papers 10 of different sizes are accommodated or a manual feed cassette 11b in which output papers 10 of arbitrarily different sizes are installed. A transfer unit 7a, a transfer conveyance unit 7b that conveys the fed output paper 10 to the transfer unit, and conveys the output paper 10 on which the toner image has been transferred toward the fixing unit 8, and an output that has passed through the fixing unit 8. A first paper discharge unit 7c that discharges the paper 10 face-up to the paper discharge tray 9, a second paper discharge unit 7d that discharges the paper 10 by a face-down method, and the image reading via the second paper discharge unit 7d. A third paper discharge unit 7e to be conveyed to the unit 1, a re-conveying unit 7f for double-sided printing, and the like are provided, and a conveyance roller is provided for each.

  The manual feed cassette 11b is provided with a size detecting means 53 for detecting the size of the output paper 10. The size detecting unit 53 includes a light shielding sensor and a size calculating unit, and is calculated by the size calculating unit based on the time and speed at which the output paper 10 passes over the light shielding sensor detected by the light shielding sensor. Thus, it is possible to detect the length of the output paper 10 in the vertical direction. It is also possible to detect the length of the output paper 10 in the lateral direction by using a plurality of light shielding sensors arranged in a direction perpendicular to the direction in which the output paper 10 is conveyed.

  As shown in FIG. 2, the control unit of the copying machine described above controls the image reading control unit 1 </ b> A that controls the document reading operation by the image reading unit 1, the image processing unit 2, and the image output unit 3. The image output control unit 3A for controlling, the operation control unit 4A for controlling the input / output signals of the operation unit 4, and the timing of each of the control blocks 1A, 2, 3A, 4A are controlled to manage the execution of the copying operation. The control blocks 1A, 2, 3A, 4A, and 5 are each provided with a CPU and a ROM that stores an operation program by the CPU.

  The image reading control unit 1A drives the document feeding unit 101 to feed the document placed on the document tray 12, and outputs an analog signal corresponding to the document image read by the CCD linear sensor 102 to the A / A. The image data obtained by converting into digital data by the D conversion means 103 is subjected to shading correction and γ correction by the input image processing means 104 provided with a predetermined conversion table.

  The image processing unit 2 includes an image processing unit 201 that generates output image data by performing spatial filter processing, halftone processing, enlargement / reduction processing, and the like on the image data output from the input image processing unit 104; Data conversion means 202 that converts output image data from 201 into a drive signal for the print head 62 and the like are provided, and the converted drive signal is output to the drive circuit of the print head 62.

  In the copying machine described above, a document is placed on the document tray 12, and the operation unit 4 is set by appropriately setting mode setting keys such as the number of copies, output paper size, and copy magnification, and then the copy switch is pressed to operate. Operation starts. That is, the system control unit 5 outputs a document image reading command to the image reading control unit 1A, outputs an output image generation command based on the read image data to the image processing unit 2, and outputs an image output control unit. An image output command is output to 3A. The image output control unit 3A drives the transport unit 7 to transport the output paper 10 from the general paper feed cassette 11a or the manual feed cassette 11b, and then outputs an image data output command to the image output control unit 3A at a predetermined timing. Then, the print head 62 is driven. When a toner image is formed on the photoreceptor 60 exposed by the print head 62, the toner image is transferred to the output paper 10, and after being fixed by the fixing unit 8, is discharged outside the apparatus.

  Hereinafter, the temperature control of the fixing unit 8 will be described in detail. As shown in FIG. 3, the functional block configuration for controlling the temperature of the fixing roller 8a, that is, the fixing unit 8, uses the heater lamp 60 and the temperature sensor 61 to control the heating of the fixing unit 8 to a target temperature. A heating control means 51; a paper selection means 54 for selecting the type or size of paper to be fed based on an operation from the operation unit 4; a paper feed cassette selection means 55 for selecting a paper feed cassette; A fixing temperature switching means 52 for switching a target temperature, the size detecting means 53, and a waiting time counting means 56 for measuring a time Tp during which the copying operation of the copying machine is not executed are configured.

  The heating control unit 51 has a plurality of target temperature setting modes for setting the target temperature in order to control the heating of the fixing unit 8. For example, as shown in FIG. 4, when the output paper 10 is a standard paper during the copying operation of the copying machine, the standard temperature mode is set to a target temperature Tst suitable for the standard paper, that is, a standard temperature. Similarly, during the copying operation of the copying machine, when the output paper 10 is the thick paper, the thick paper temperature mode is set to the target temperature The which is a temperature different from the standard temperature suitable for the thick paper. When the copying machine is not performing a copying operation, the standby temperature mode is set to the target temperature Twa, which is lower than the standard temperature. Similarly, when the copying machine is not performing the copying operation, A power-saving temperature mode that is set to a target temperature Tsa that is lower than the standby temperature mode, and a target temperature Twa after the copying machine is started up. A startup mode for setting the target temperature Tbo for causing the Ku increases.

  The standard temperature in the standard temperature mode is an optimum temperature for heating and fixing the toner image formed on the output paper 10 when the standard paper is used as the output paper 10, and forms the toner image. The temperature can be appropriately changed according to the toner material. The target temperature The in the thick paper temperature mode is set to a temperature higher than the standard temperature corresponding to the heat absorption capacity of the thick paper.

  The standby temperature mode and the power saving temperature mode are modes that are set when the copying operation of the copying machine is not performed. The standby temperature mode is set until a predetermined time Tth elapses after the copying machine enters a predetermined state after startup or after the previous copying operation is completed until the next copying operation is started. In this mode, the temperature is set slightly lower than the standard temperature (target temperature Twa) so that the next copying operation can be performed quickly. The power saving temperature mode is set after a lapse of a predetermined time Tth after the copying machine enters a predetermined state after startup or after the previous copying operation is completed until the next copying operation is started. In this mode, the power saving effect is emphasized, and the temperature is set to a temperature (target temperature Tsa) much lower than the standard temperature.

  The temperature switching means 52 includes paper type or paper size information from the paper selection means 54, paper cassette information from the paper cassette selection means 55, and paper size information from the size detection means 53. Based on the copying operation information from the system control unit 5 and the standby time information from the standby time counting means 56, the above-described target temperature setting mode of the heating control means 51 is switched. .

  The fixing temperature control of the fixing unit 8 will be described based on the flowchart of FIG. 5 and the relationship between the target temperature setting mode switching timing and the target temperature shown in FIG. When the power of the copying machine is turned on (SA1), the heating control unit 51 sets the eye temperature setting mode to the start mode by the temperature switching unit 52, and the temperature of the fixing unit 8 quickly reaches the standby temperature. A warm-up operation is performed so as to rise (SA2, T1).

  When the temperature of the fixing unit 8 reaches the standby temperature, the heating control unit 51 switches the target set temperature mode to the standby temperature mode, and maintains the fixing unit 8 at the standby temperature (SA3). At the same time, the standby time counting means 56 starts measuring the time Tp in the standby temperature mode. The temperature switching means 52 switches the target temperature setting mode to the power saving temperature mode when the time Tp in the standby temperature mode has exceeded the predetermined time Tth (SA4, SA6, T3). The waiting time counting means 56 resets the count value when the copying operation of the copying machine is started.

  When various settings are made by the operation unit 4 and the copy switch is pressed to start the copying operation of the copying machine (SA5, SA7), the heating control means 51 is set to the standby temperature mode or the Regardless of being in the power saving temperature mode, the fixing temperature switching means 52 switches the target temperature setting mode based on the various information.

  The fixing temperature switching means 52 switches the target temperature setting mode based on the paper type or paper size information from the paper selection means 54 (SA8). If the output paper 10 is a standard paper based on the paper type or paper size information, the heating control means 51 is switched to the standard temperature mode (SA9, T4), and during the copying operation of the copying machine, The temperature of the fixing unit 8 is controlled to be the standard temperature (SA10). Also, the fixing temperature switching means 52 waits for the end of the copying operation and switches to the standby temperature mode again (SA15, T5).

  If the output paper 10 is thick paper based on the paper type or paper size information, the mode is switched to the thick paper temperature mode (SA11, T6, T7). In this case, if the output paper 10 is selected to be fed from the general paper cassette 11a from the paper cassette information from the paper cassette selecting means 55 (SA12), the heating control means 51 is During the copying operation of the copying machine, the temperature of the fixing unit 8 is controlled to be the target temperature The without switching the target temperature setting mode (SA10). Further, the heating control means 51 waits for the end of the copying operation and is switched again to the standby temperature mode (SA15, T8).

  If the output paper 10 is selected to be fed from the manual feed cassette 11b from the paper feed cassette information (SA12), the operation obtained from the paper type or paper size information from the paper selection means 54 The size of the output paper 10 set by the section 4 is constantly compared with the size of the output paper 10 that is actually supplied during the copying operation of the copying machine detected by the size detecting means 53. The heating control unit 51 controls the temperature of the fixing unit 8 to be the target temperature The without switching the target temperature setting mode while the sizes match. Further, the copying operation ends and the standby temperature mode is switched (SA13, SA14, SA15, T8).

  When the detected change in the actually supplied output paper size is detected and is different from the set output paper size, the heating control unit 51 causes the temperature of the fixing unit 8 to become the target temperature The. The cardboard temperature mode controlled as described above is switched to the standard temperature mode (SA13, SA9, T9). That is, the fixing roller 8a is surely switched to a standard temperature that does not cause abnormal heating. Further, after the copying operation is completed, the standby temperature mode is switched (SA10, SA15, T10).

  In the embodiment described above, the size detection unit 53 is provided only in the manual feed cassette 11a. However, the general paper feed cassette 11a is also provided with the size detection unit 53 and is set in the thick paper temperature mode. The standard temperature mode may be switched to when the size change of the output paper fed from the general paper feed cassette 11a is detected.

  In the above-described embodiment, the case where the target temperature setting mode during the copying operation of the copying machine is the two modes of the standard temperature mode and the cardboard temperature mode has been described, but the target temperature setting mode corresponding to the cardboard temperature mode is output. A configuration may be adopted in which a target temperature setting mode corresponding to each thickness of output paper is provided by further dividing the paper thickness classification into a plurality of divisions. In each target temperature setting mode, when the size change is detected by the size detecting means 53, the standard temperature mode may be switched.

Illustration of copier Illustration of circuit configuration of copier Functional block diagram for fixing temperature control Explanatory drawing about the relationship between the switching timing of the target temperature setting mode with which the heating control means is provided and the target temperature Flow chart for explaining the operation of fixing temperature control

5: System control unit 8: Fixing unit 8a: Fixing roller 10: Output paper 11a: General paper feeding cassette 11b: Manual feed cassette 51: Heating control unit 52: Fixing temperature switching unit 53: Size detection unit 54: Paper selection unit 55
55: Paper cassette selection means 56: Standby time counting means 60: Heater 61: Temperature sensor

Claims (1)

A heating control means for controlling the fixing roller for heating and fixing the toner image formed on the paper to a target temperature; a paper selection means for selecting the type and size of the paper to be fed; If the paper selected by the paper selection means is standard paper, the target temperature is switched to the standard temperature, and if the paper is thicker than standard paper, the fixing temperature is used to switch the target temperature to a temperature higher than the standard temperature. An image forming apparatus including a switching unit and a size detection unit that detects a size of a sheet to be fed,
The fixing temperature switching unit is configured to switch the target temperature when the size detected by the size detection unit is different from the size selected by the paper selection unit in a state where the target temperature is switched to a temperature higher than the standard temperature. An image forming apparatus configured to re-switch the temperature from a temperature higher than the standard temperature to the standard temperature.

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