Image forming device

Abstract

To estimate the cause of deviation to one side of a sheet during detection by using the history of opening and closing of paper feed cassettes and the history of the occurrence of deviation to one side, and notify a user of an appropriate method for dealing with the deviation.SOLUTION: When the difference between temperatures detected by thermistors 309, 310 provided on both ends of a heating roller 323 of a fuser 170 is equal to or more than a predetermined value, an image forming apparatus determines that deviation to one side of a sheet occurs, and based on the history of opening and closing of a paper feed cassette 150 and the history of the occurrence of previous deviation to one side, notifies a user of a method for dealing with the determination as deviation to one side.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus having an openable and closable paper storage section for feeding paper. [Background technology]

[0002] In image forming devices such as laser printers and copiers, the toner image is heated and fixed onto the paper by passing the paper on which an unfixed toner image has been formed through the fixing nip of a heat fixing device (hereinafter referred to as a fixing device) and applying heat and pressure to the toner image.

[0003] When paper passes through the fixing nip, it absorbs heat from the fixing nip, which is heated by the heater. Therefore, if the paper width is narrow compared to the heater width, a temperature difference occurs between the paper passing area and the non-passing area (edge) of the fixing nip. If the temperature at the edge of the fixing nip continues to rise, image defects will occur, so a temperature rise suppression process is widely used to cool the edge of the fixing unit when the edge temperature exceeds a certain temperature, reducing productivity.

[0004] Even when paper of a width equal to the heater width is passed through, edge temperature rise can occur. When paper is fed from a cassette or tray, a toner image is formed in the image forming unit, and the paper is then transported to the fixing device. If the paper is not properly set in the cassette or tray, the paper will be transported out of alignment. Therefore, even if the paper width is the same as the heater width, misalignment of the paper in the fixing nip can result in a non-paper passing area at one edge of the fixing nip, causing excessive temperature rise. The temperature rise suppression process is activated to suppress this excessive temperature rise, which can reduce productivity.

[0005] As a method for determining conveyance problems caused by such paper misalignment, an image forming apparatus has been proposed as described in Patent Document 1. Patent Document 1 describes a method for detecting paper misalignment and controlling device operation by utilizing changes in the difference in edge temperatures detected by temperature detection means installed at the left and right ends of the fixing unit before and after the paper passes through the fixing nip. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Application No. 2016-139075 Summary of the Invention [Problem to be solved by the invention]

[0007] When uneven printing occurs, the productivity of the device is reduced in order to prevent the temperature from rising, but in this case, the functionality of the device is limited. Therefore, it is desirable to be able to present a solution to the user after uneven printing occurs.

[0008] However, in the method of detecting imbalance by detecting changes in the temperature detection section as paper passes, as in Patent Document 1, it is possible to detect the fact that imbalance has occurred, but it is difficult to identify the cause, and it is difficult to suggest appropriate measures to the user.

[0009] An object of the present invention is to present to the user a method for eliminating uneven paper alignment when it occurs. [Means for solving the problem]

[0010] In order to solve the above problems, the image forming apparatus of the present invention comprises: Paper cassette An image forming apparatus into which , a feeding means for feeding the paper stored in the cassette; forming means for forming a toner image on the paper fed by the feeding means; a fixing unit having a nip portion and fixing the toner image onto a sheet conveyed through the nip portion by heat; a first temperature detecting means and a second temperature detecting means provided in the fixing means for detecting temperatures at both end portions of the fixing means in a direction perpendicular to a conveying direction of the paper conveyed through the nip portion; a notification means for notifying information; a control means for causing the notifying means to issue a first message prompting the user to check the position of a guide that regulates the position of paper inside the cassette when a difference between the temperature detected by the first temperature detecting means and the temperature detected by the second temperature detecting means is equal to or greater than a predetermined value, if there is no history of the notifying means issuing the first message, and causing the notifying means to issue a second message prompting the user to adjust the installation position of a regulating member that regulates the abutment position when the cassette is inserted into the image forming apparatus, if there is a history of the notifying means issuing the first message; The present invention is characterized by having the following. [Effects of the Invention]

[0011] According to the present invention, when uneven distribution occurs, a method for eliminating the uneven distribution can be presented to the user. [Brief explanation of the drawings]

[0012] [Figure 1] Cross-sectional view of an image forming apparatus [Figure 2] Control block diagram of an image forming apparatus [Figure 3] Schematic diagram of the paper cassette adjustment mechanism [Figure 4] Illustration of paper misalignment [Figure 5] Control flow chart during image formation [Figure 6] Flowchart of the bias notification determination process [Figure 7] Flowchart of cassette open / close monitoring process [Figure 8] FIG. 10 is a diagram showing a notification message to a user. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0014] Fig. 1 is a cross-sectional view of an image forming apparatus according to this embodiment, and Fig. 2 is a control block diagram according to this embodiment. The basic configuration will be described with reference to Figs.

[0015] The control unit 300 in FIG. 2 is composed of a CPU 301, a RAM 302, a ROM 303, and a non-volatile memory 304.

[0016] An instruction / display device 305 (hereinafter referred to as operation unit 305) including a touch panel is connected to CPU 301 as a notification means, and a user can request desired operations, such as executing a print job or operating the power supply, from CPU 301 via operation unit 305. Operation unit 305 also notifies the user of various information. CPU 301 can also be connected to PC 307 via external I / F 306, which is an interface with external devices. CPU 301 starts operation upon receiving an instruction to start a print operation or an instruction to return from a power saving mode from operation unit 305 or PC 307. For example, when a user issues an instruction to start a print operation from PC 307, CPU 301 controls the drive of image forming unit 308 and various loads 311 composed of connected motors, heaters, etc.

[0017] During image formation, the CPU 301 can obtain the temperatures at both ends of the fixing unit in the width direction via the connected end thermistor 1 (309) and end thermistor 2 (310). The CPU 301 can also obtain the open / closed status of each of the multiple paper feed cassettes via the cassette open / close detection sensor 312.

[0018] As described above, the CPU 301 is configured to be able to control the image forming unit 308. The image forming unit 308 is able to control high voltages and drive of the cartridges 120a, 120b, 120c, and 120d, each including a photosensitive member, shown in FIG. 1, the intermediate transfer belt 130, the primary transfer units 123a to 123d, and the secondary transfer unit 140, as well as control the laser scanners 122a to 122d.

[0019] The image formation procedure and the procedures of the flowcharts used in the following description are stored in the ROM 303. The non-volatile memory 304 can retain data even after the power supply to the CPU 301 is stopped, and continues to save the data stored in the RAM 302 even after the power is turned off and on.

[0020] <Explanation of basic image formation operations> 1 and 2, a basic image forming operation will be described. When a user executes a print job from PC 307 connected to external I / F 306 and a print operation start instruction is sent to CPU 301, CPU 301 starts the paper feeding operation of sheets housed in paper feed cassettes 150a and 150b. By driving a transport motor that serves as the drive source for paper feed pickup rollers 151a and 151b, paper feed pickup rollers 151a and 151b rotate, feeding and conveying sheets one by one from paper feed cassettes 150a and 150b. In other words, pickup rollers 151a and 151b function as a feeding unit. At this time, CPU 301 monitors whether the paper feeding operation was performed normally using paper feed pickup sensors 152a and 152b.

[0021] Meanwhile, CPU 301 starts the image forming operation using cartridges 120a to 120d to coincide with the arrival of paper at secondary transfer unit 140, and primary transfer units 123a to 123d form toner images on intermediate transfer belt 130. Cartridge 120a forms a yellow image, cartridge 120b forms a magenta image, cartridge 120c forms a cyan image, and cartridge 120d forms a black image. Note that yellow, magenta, cyan, and black may also be referred to as Y, N, C, and K, respectively. Each cartridge is configured to be user-installable and removable.

[0022] During the paper feeding operation, paper fed from paper feed cassette 150a or paper feed cassette 150b is transported by transport path rollers 153, 154, and 155. CPU 301 detects the position of the transported paper by monitoring pre-registration transport sensor 160. Then, taking into account the timing when the leading edge of the paper reaches pre-registration transport sensor 160, the transport of the paper is controlled so that the leading edge of the paper and the leading edge of the toner image on intermediate transfer belt 130 coincide with each other at secondary transfer unit 140. For example, if it is determined that the paper has arrived earlier than the toner image, registration rollers 161 stop the paper for a predetermined time and then resume transport so that the leading edges coincide with each other. In this way, a secondary transfer voltage is applied to the paper and toner image that have arrived at secondary transfer unit 140, and the toner image is transferred to the paper.

[0023] After the secondary transfer, the paper is transported to the fixing device 170, where the toner image on the paper is heated and fixed to the paper, and then the paper is transported further downstream of the image forming apparatus.

[0024] When the leading edge of the paper after fixing reaches paper transport sensor 171, CPU 301 determines whether to transport the paper to paper transport path 230 or paper transport path 231, in accordance with an instruction previously specified from operation unit 305 or PC 307 connected via external I / F 306. Based on the result of this determination, CPU 301 switches the operation of transport flapper 172 to switch the destination of the paper. Specifically, in the case of the front side of a double-sided print instruction, the paper is transported to paper transport path 230, and in the case of a single-sided print or the back side of a double-sided print, the paper is transported to paper transport path 231.

[0025] The following describes the case where paper is transported to paper transport path 231. The paper transported to paper transport path 231 is further transported by transport rollers 232 to a downstream portion of the image forming apparatus. Similar to the switching described above, CPU 301 switches the operation of paper transport flapper 190 in accordance with instructions previously specified from operation unit 305 or PC 307 connected via external I / F 306. This allows for switching between transporting paper to paper transport path 180 or paper transport path 181. If the user's designated paper output destination is paper output tray 200, the paper is transported to paper transport path 180, and if the designated paper output destination is paper output tray 196, the paper is transported to paper transport path 181.

[0026] The above basic image forming operation is an example, and the present invention is not limited to the above configuration.

[0027] <Explanation of the cassette adjustment mechanism> FIG. 3 is a schematic diagram illustrating the cassette adjustment mechanism, consisting of abutment member 320a and adjustment screw 321a, installed on the side of the paper feed cassette 150a. The paper feed cassette 150a is in the closed state when it is pushed in until the abutment member 320a on the paper feed cassette 150a contacts the abutment portion inside the image forming apparatus (not shown). The open state is when the abutment portion inside the image forming apparatus and the abutment member 320a on the paper feed cassette 150a are not in contact. In other words, the abutment member 320a functions as a restricting member that restricts the position of the paper feed cassette in the closed state in the insertion direction. The abutment member 320a has a cutout width for the adjustment screw 321a to allow it to move back and forth relative to the cassette insertion direction. Therefore, moving the abutment member 320a in the cassette insertion direction moves the center of the paper feed cassette 150a in the opposite direction to the cassette insertion direction. Furthermore, by moving the abutting member 320a in the direction opposite to the cassette insertion direction, the center of the sheet feed cassette 150a moves in the cassette insertion direction. Possible By moving the adjustment screw 321a, it becomes possible to adjust the center position of the paper feed cassette 150a, i.e., the center position of the paper in the direction perpendicular to the conveyance direction. In other words, the adjustment screw 321a functions as an adjustment means for adjusting the position of the paper feed cassette in the closed state in the insertion direction. While the above description has been given for the mechanism of the paper feed cassette 150a, the same applies to the paper feed cassette 150b.

[0028] The cassette adjustment mechanism in this embodiment is merely an example, and the adjustment mechanism may be, for example, a dial-type member or a mechanism installed on the image forming apparatus side. This concludes the description of the cassette adjustment mechanism.

[0029] <Explanation of bias detection> 4 is a diagram showing a schematic diagram of the inside of the fixing unit 170. The fixing unit 170 has a heating roller 322 as a first rotating body and a pressure roller 323 that presses against the heating roller 322. The heating roller 322 also has a fixing heater 324 that uniformly heats the heating roller 322. The heating roller 322 is further provided with a main thermistor 325 that measures the temperature at the center of the heating roller 322, and the aforementioned end thermistor 1 (309) and end thermistor 2 (310) that measure the temperatures at both ends. These thermistors function as temperature detection means.

[0030] 4 is the position of the paper when the center of the paper in the width direction is aligned with the center of the paper in the width direction perpendicular to the paper conveyance direction at the nip of the fixing device 170. Paper position P2 is the position of the paper when the center of the paper is shifted toward the end thermistor 1 (309) with respect to the center of the fixing device 170 (misalignment in the width direction), that is, when the paper is shifted to one side.

[0031] When the paper is at paper position P, the temperature at the center of the fuser 170 is relatively low because the paper absorbs heat from the heating roller, while the temperature at both ends rises compared to the center because they are not affected by the paper. At this time, the temperatures of end thermistors 1 (309) and 2 (310) are approximately the same because neither end is affected by the paper. On the other hand, when the paper is at position P2, the temperature drops from the center of the fuser 170 to end thermistor 1 (309) because it is affected by the paper, while the temperature rises on the end thermistor 2 (310) side because it is not affected by the paper. For this reason, if the paper is misaligned, a difference in temperature will occur between end thermistor 1 (309) and end thermistor 2 (310).

[0032] In this embodiment, if the temperature difference between edge thermistor 1 (309) and edge thermistor 2 (310) is equal to or greater than a predetermined value, it is determined that misalignment has occurred. Note that even if the center of the paper is misaligned toward edge thermistor 2 (310), it is possible to determine misalignment from the temperature difference between edge thermistor 1 (309) and edge thermistor 2 (310).

[0033] <Explanation of the overall picture of control> 5 is a flowchart showing the process of detecting unevenness by the CPU 301. This procedure is stored as a program in the ROM 303, and is read and executed by the CPU 301.

[0034] When the CPU 301 is powered on and starts processing, the CPU 301 first checks whether there is a print request from the PC 307 connected via the external I / F 306 or from the operation unit 305 (S401).

[0035] If CPU 301 determines in S401 that a print request has been made, it performs an image forming operation based on the print request (S402). On the other hand, if CPU 301 determines in S401 that a print request has not been made, it proceeds to processing in S406. After image forming operation in S402, CPU 301 acquires the temperatures of end thermistors (309, 310) installed at both ends of fuser 170 (S403). Here, CPU 301 determines whether the temperature difference between the temperatures of end thermistors (309, 310) acquired in S403 is equal to or greater than a predetermined value (S404). If CPU 301 determines in S404 that the temperature difference is equal to or greater than the predetermined value, it proceeds to S405, where it performs a bias notification determination process (described later) (S405). On the other hand, if CPU 301 determines in S404 that the temperature difference is less than the predetermined value, it proceeds to processing in S406.

[0036] When the process proceeds to S406, the CPU 301 performs the cassette open / close monitoring process described below. After that, the CPU 301 checks whether there is a request to turn off the power (S407). If there is no request, the flow from S401 is performed again, and if there is a request, the CPU 301 turns off the power.

[0037] <Description of the bias notification determination process> Next, the bias notification determination process shown in S405 of FIG. 4 will be described with reference to FIG.

[0038] First, the CPU 301 determines whether a rough installation confirmation flag is set for the designated paper cassette currently being fed, indicating that the user has reinstalled paper (S501). The rough installation confirmation flag indicates that the user has opened and closed the cassette because the paper may not have been properly loaded in the paper cassette. Setting this flag indicates that the user has checked the designated paper cassette. If the CPU 301 determines that the rough installation confirmation flag is not set, it sets a cassette open / close instruction flag (S502). The cassette open / close instruction flag indicates that an instruction to open or close the designated paper cassette is required. The CPU 301 then determines that the paper misalignment is due to improper paper installation and instructs the operation unit 305 to display the message (first message) shown in FIG. 8A to prompt the user to review the paper installation status (guide position) in the paper cassette (S503). 8A is displayed to prompt the user to open or close the paper feed cassette. Then, the CPU 301 proceeds to step S508, which will be described later.

[0039] On the other hand, if the CPU 301 determines in S501 that the rough installation confirmation flag has been set, the process proceeds to S504. In this case, the user has already opened the cassette and confirmed the paper installation status, so the paper is installed correctly. Therefore, the CPU 301 sets the offset confirmation flag for the designated paper cassette that is currently supplying paper (S504). The CPU 301 then checks whether the offset confirmation flag has been set previously for a paper cassette other than the designated paper cassette (S505). If the CPU 301 determines that the offset confirmation flag has not been set for a cassette other than the designated paper cassette, the process proceeds to S506. In S506, the CPU 301 determines that the offset is caused by improper adjustment of the designated paper cassette, and instructs the operation unit 305 to display the message (second message) shown in FIG. 8B (S506). Furthermore, if in S505 CPU 301 determines that the offset determination flag is set for a cassette other than the designated paper feed cassette, the process proceeds to S507. In S507, CPU 301 determines that the offset is caused by a faulty thermistor in fixing unit 170, and instructs the display of the message (third message) shown in Fig. 8(c) (S507). After completing the process of S506 or S507, CPU 301 proceeds to the process of S508.

[0040] Next, the CPU 301 proceeds to S508, where it acquires whether the user has pressed the "Resume Printing" button displayed on the operation unit 305, and waits until it determines that the button has been pressed (S508). Thereafter, if the CPU 301 determines that the "Resume Printing" button has been pressed, it ends the misalignment notification determination process.

[0041] <Description of cassette open / close monitoring process> Next, the cassette open / close detection process shown in S406 of FIG. 4 will be described with reference to FIG.

[0042] When the cassette open / close monitoring process starts, the CPU 301 first reads the value of the connected cassette open / close detection sensor 312 and stores it in RAM 302 (S601). Next, the CPU 301 references the value stored in RAM 302 when the cassette open / close detection sensor 312 was last read, and determines whether the current value has changed from the previous value (S602). If the CPU 301 determines that there is no change between the previous value and the current value, this means that no cassette opening or closing operation has occurred, and the cassette open / close monitoring process ends.

[0043] Next, in S602, if the CPU 301 determines that a change has occurred between the previous value and the current value, it means that a cassette has been opened or closed, and so the process proceeds to S603, where the value (current value) of the cassette open / close detection sensor is saved in RAM 302 (S603). Next, the CPU 301 checks whether the change from the previous value to the current value represents a change from an open state to a closed state of the paper feed cassette (S604). If the CPU 301 determines that the state of the paper feed cassette has changed from a closed state to an open state, it ends the cassette open / close monitoring process. On the other hand, if the CPU 301 determines that the state of the paper feed cassette has changed from an open state to a closed state, it proceeds to the process of S605.

[0044] When the CPU 301 proceeds to the process of S605, it determines whether the cassette open / close instruction flag for the sheet cassette in question is set (S605). If the CPU 301 determines in S605 that the cassette open / close instruction flag is not set, this means that the user did not open or close the cassette in response to the notified message, but rather for another reason. Therefore, the CPU 301 resets the rough installation confirmation flag for the sheet cassette in question, which is stored in RAM 302 (S606), and ends the cassette open / close monitoring process. On the other hand, if the CPU 301 determines in S605 that the cassette open / close instruction flag is set, this means that the user opened or closed the cassette in response to the notified message. Therefore, the CPU 301 resets the cassette open / close instruction flag for the sheet cassette in question, which is stored in RAM 302, and sets the rough installation confirmation flag (S607). After executing the process of S607, the CPU 301 ends the cassette open / close monitoring process.

[0045] Although the present embodiment shows control of a paper feed cassette, the same effect can be obtained by detecting the presence or absence of paper using a manual paper feed mechanism or the like.

[0046] As described above, according to this embodiment, the cause of sheet misalignment is estimated using the opening and closing history of the sheet feed cassette that fed the sheet and the misalignment occurrence history for each sheet feed cassette.

[0047] If there is no history of misalignment in the paper feed cassette and no opening or closing of the paper feed cassette has been detected between the time the paper was installed and the time the misalignment occurred, the system determines that the paper was installed improperly in the paper feed cassette and displays the message shown in Figure 8(a) to prompt the user to check the paper installation.

[0048] If none of the paper cassettes have a history of misalignment and a message has already been issued to prompt the user to check the paper placement in the paper cassette when misalignment occurred, the system determines that the paper cassette is out of adjustment and displays the message shown in Figure 8(b) to prompt the user to adjust the paper cassette.

[0049] Furthermore, if a message urging the user to check the placement of paper in the paper feed cassette has already been issued after detecting the occurrence of paper misalignment, and if there is a history of paper misalignment occurring in other paper feed cassettes, it is determined that the thermistor in the fixing unit 170 is faulty. Therefore, in this case, the message shown in Fig. 8(c) is issued to the user to urge the user to have the fixing unit 170 serviced.

[0050] In the above embodiment, an example in which multiple cassettes are provided has been described, but even in a configuration in which only one cassette is provided, it is possible to notify the messages shown in Figures 8(a) and 8(b). In this case, the processes of S505 and S507 are omitted.

[0051] By controlling as described above, the notification message can be switched depending on the estimated cause, and when uneven load distribution occurs, it becomes possible to instruct the user on an appropriate method of dealing with the situation. [Explanation of symbols]

[0052] 150a, 150b paper cassette 170 Fixing unit 309 End thermistor 1 310 End thermistor 2 312a, 312b Cassette open / close detection sensor 320a Stopper member 321b Adjustment screw

Claims

1. An image forming apparatus into which a cassette containing paper is inserted, a feeding means for feeding the paper stored in the cassette; forming means for forming a toner image on the paper fed by the feeding means; a fixing unit having a nip portion and fixing the toner image onto a sheet conveyed through the nip portion by heat; a first temperature detecting means and a second temperature detecting means provided in the fixing means for detecting temperatures at both end portions of the fixing means in a direction perpendicular to a conveying direction of the paper conveyed through the nip portion; a notification means for notifying information; a control means for causing the notifying means to issue a first message prompting the user to check the position of a guide that regulates the position of sheets inside the cassette when a difference between the temperature detected by the first temperature detecting means and the temperature detected by the second temperature detecting means is equal to or greater than a predetermined value, if there is no history of the notifying means issuing the first message, and causing the notifying means to issue a second message prompting the user to adjust the installation position of a regulating member that regulates the abutment position when the cassette is inserted into the image forming apparatus, if there is a history of the notifying means issuing the first message; An image forming apparatus comprising:

2. 2. The image forming apparatus according to claim 1, wherein the cassette has an adjustment means for adjusting the position of the regulating member in a direction perpendicular to the paper feeding direction.

3. A plurality of the cassettes are provided, The image forming apparatus of claim 1 or 2, characterized in that when the control means detects that the difference is greater than or equal to the predetermined value when the fixing means is fixing multiple sheets of paper fed from a first cassette among the multiple cassettes, and if the control means also detects that the difference is greater than or equal to the predetermined value when the fixing means is fixing multiple sheets of paper fed from a cassette other than the first cassette prior to the detection, it causes the notification means to notify a third message urging inspection of the fixing means.

4. 4. The image forming apparatus according to claim 3, wherein the control unit determines that the first temperature detection unit or the second temperature detection unit is defective.

Images