Detection device, image forming apparatus

Abstract

To resolve such a problem that, when abnormality is determined to occur on the basis of a result of detection by a sensor, the cause of the abnormality cannot be determined.SOLUTION: Control means acquires a first voltage value of light reception by a photodetector when a light emitter emits light at a first current value, and a second voltage value of the light reception by the photodetector when the light emitter emits the light at a second current value different from the first current value, so as to determine whether abnormality occurs at detection means on the basis of a variation of the first and second voltage values.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to a detection device for detecting a sheet.

Background Art

[0002] Conventionally, in an image forming apparatus, as shown in Patent Document 1, a method of detecting the inclination of a conveyed sheet by a sensor and correcting the relative positional relationship between the sheet and the formed image is known.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when it is determined that an abnormality has occurred based on the result detected by the sensor, the cause of the abnormality cannot be determined.

Means for Solving the Problems

[0005] In order to achieve the above object, it has a light emitting element and a light receiving element, a detection means for detecting a sheet, and , based on the detection result of the detection means, control means for detecting an end portion of the sheet in a direction orthogonal to the conveyance direction of the sheet, and the control means causes the light emitting element to emit light at a first current value and the first voltage value received by the light receiving element, and the second voltage value received by the light receiving element when the light emitting element emits light at a second current value different from the first current value, and the change amount between the first voltage value and the second voltage value The first voltage value is greater than 0, and the second voltage value is greater than 0. It is characterized by determining that an abnormality has occurred in the detection means. If it is below the threshold, the detection means is abnormal If the amount of change is greater than the threshold, it is determined that there is no abnormality in the detection means. to determine.

Effects of the Invention

[0006] According to the present invention, the cause of the abnormality can be identified. [Brief explanation of the drawing]

[0007] [Figure 1] Schematic diagram of an image forming apparatus [Figure 2] Control block diagram of an image forming apparatus [Figure 3] Diagram showing light intensity adjustment [Figure 4] A flowchart showing how to adjust the light intensity. [Figure 5] A flowchart showing how to adjust the light intensity. [Figure 6] This diagram illustrates how to determine whether a line sensor is functioning correctly or not. [Figure 7] A flowchart illustrating the normal / abnormal determination of line sensors. [Figure 8] This diagram illustrates how to determine whether a line sensor is functioning correctly or not. [Figure 9] A flowchart illustrating the normal / abnormal determination of line sensors. [Figure 10] This diagram illustrates how to determine whether a line sensor is functioning correctly or not. [Figure 11] A flowchart illustrating the normal / abnormal determination of line sensors. [Figure 12] This diagram illustrates how to determine whether a line sensor is functioning correctly or not. [Figure 13] A flowchart illustrating the normal / abnormal determination of line sensors. [Figure 14] Schematic diagram showing the position of the seat and the line sensor. [Modes for carrying out the invention]

[0008] Embodiments of the present invention will be described below with reference to the drawings. Note that the following embodiments are not intended to limit the invention as defined in the claims, and not all combinations of features described in the embodiments are necessarily essential to the solution of the invention. [Examples]

[0009] (Image forming apparatus) FIG. 1 is a schematic configuration diagram of an image forming apparatus 201. FIG. 2 is a control block diagram of the image forming apparatus 201. The operation of the image forming apparatus 201 will be described using FIGS. 1 and 2.

[0010] The control unit 401 is a control means for controlling the operation of the image forming apparatus 201. It exchanges information such as image data and setting of image forming conditions with a host device 900 such as a personal computer, an image scanner, a facsimile, and an operation unit 730. Further, the control unit 401 performs signal processing and sequence control on various process devices.

[0011] The image forming apparatus 201 is a tandem type and intermediate transfer type laser beam printer that uses an electrophotographic process. The image forming apparatus 201 forms an image corresponding to the image data output from the host device 900 connected to the control unit 401 on a sheet S which is a recording medium.

[0012] The image forming apparatus main body 201A includes an image forming unit 201B that forms an image on a sheet. Above the image forming apparatus main body 201A, an image reading device 202 is disposed substantially horizontally as the image forming apparatus main body 201A. A discharge space V for sheet discharge is formed between the image reading device 202 and the image forming apparatus main body 201A.

[0013] The cassette feeding unit 230 includes a feeding cassette 1 for stacking the sheet S and a pickup roller 2 for feeding the sheet S loaded on the feeding cassette 1. Further, the cassette feeding unit 230 includes a separating unit including a feed roller 3 and a retard roller 4 for separating the sheet S sent out from the pickup roller 2.

[0014] The manual feed unit 235 includes a manual feed tray 5 for loading sheets S, and a pickup roller 502 for feeding the sheets S loaded in the manual feed tray 5. The manual feed unit 235 also includes a separation unit consisting of a feed roller 503 and a retard roller 504 for separating the sheets S fed out by the pickup roller 502.

[0015] The image forming unit 201B, which serves as an image forming means, comprises a laser scanner 210 and four process cartridges 211 that form an image using four toners: yellow (Y), magenta (M), cyan (C), and black (K). Each process cartridge 211 includes a photosensitive drum 212, a charger 213 which is a charging means, and a developer 214 which is a developing means. The image forming unit 201B also includes a toner cartridge 215 that supplies toner to the developer 214. Furthermore, it includes a secondary transfer unit 201D and a fixing unit 201E located above the process cartridges 211.

[0016] The secondary transfer unit 201D includes an intermediate transfer belt 216 wrapped around a drive roller 216a and a tension roller 216b. A primary transfer roller 219 is provided on the inside of the intermediate transfer belt 216, in contact with the intermediate transfer belt 216 at a position opposite the photosensitive drum 212. The intermediate transfer belt 216 rotates in the direction of the arrow by the drive roller 216a, which is driven by a drive unit (not shown). A secondary transfer roller 217 is provided in the secondary transfer unit 201D at a position opposite the drive roller 216a, for transferring the image formed on the intermediate transfer belt 216 to the sheet S.

[0017] A fixing unit 201E is positioned above the secondary transfer roller 217, and above the fixing unit 201E are a first discharge roller pair 225a, a second discharge roller pair 225b, and a double-sided reversal unit 201F. The double-sided reversal unit 201F is provided with a reversible reversible roller pair 222 and a re-transport passage R for transporting the sheet S, on which an image has been formed on the first surface, back to the image forming unit 201B.

[0018] An operating unit 730 is provided at the top of the image forming apparatus 201 as a means of receiving operations from the user. The operating panel is a touch panel type that not only displays information but also allows for input.

[0019] (Operation of the image forming apparatus) Next, the image forming operation of the image forming apparatus 201 will be described. First, when the image forming apparatus 201 receives image data to be printed, the image data is processed and then converted into an electrical signal which is transmitted to the laser scanner 210 of the image forming unit 201B. In the image forming unit 201B, the surface of the photosensitive drum 212, whose surface is uniformly charged to a predetermined polarity and potential by the charger 213, is sequentially exposed by the laser scanner 210. As a result, electrostatic latent images of yellow, magenta, cyan, and black are sequentially formed on the photosensitive drum of each process cartridge 211, respectively.

[0020] The electrostatic latent image formed on the photosensitive drum 212 is developed by the respective color developer units 214 to visualize it as an image. The images formed on each photosensitive drum are sequentially transferred onto the intermediate transfer belt 216 by applying a primary transfer bias to the primary transfer roller 219. As a result, a color image is formed on the intermediate transfer belt 216.

[0021] In parallel with the image forming operation, the sheets S are transported one by one to the register roller pair 240 by the cassette feeding unit 230 or the manual feed unit 235. The skew of the sheets S is corrected by the register roller pair 240. The position of the sheets S is detected by a line sensor 71a located upstream of the register roller pair 240, and the position of the electrostatic latent image formed on the photosensitive drum 212 is corrected according to the detected position of the sheets S. Note that the line sensor 71a or 71b and the control unit 401 together can also be referred to as a detection device located within the image forming apparatus 201.

[0022] After the sheet S is corrected for skew and the electrostatic latent image formed on the photosensitive drum 212 is corrected, the sheet S is transported to the secondary transfer section 201D by the register roller pair 240. In the secondary transfer section 201D, a secondary transfer bias is applied to the secondary transfer roller 217, and the image formed on the intermediate transfer belt 216 is transferred to the sheet S.

[0023] The sheet S on which the image has been secondarily transferred is transported to the fixing unit 201E. In the fixing unit 201E, the sheet S is subjected to heat and pressure in the nip section formed by the pressure roller 220a and the heating roller 220b, and the unfixed image secondarily transferred onto the sheet S is fixed. The sheet S with the fixed image is discharged into the discharge space V by the first discharge roller pair 225a or the second discharge roller pair 225b located downstream of the fixing unit 201E, and is loaded onto the paper output tray 223 in the discharge space V. If images are to be formed on both sides of the sheet S, after the image on the first side is fixed, the sheet S is transported to the re-transport passage R by the reversing roller pair 222 and transported again to the image forming unit 201B. During this transport, the position of the sheet S is detected by the line sensor 71b located in the re-transport passage R, and the formation position of the electrostatic latent image corresponding to the image on the second side formed on the photosensitive drum 212 is corrected according to the detected position of the sheet S.

[0024] (Block diagram for controlling the lysensor) Referring to Figure 2, the control of line sensors 71a and 71b, and the control of the image formation position based on the outputs from line sensors 71a and 71b will be explained. The control unit 401 receives outputs from the register roller pair 240 and line sensors 71a and 71b, which are located on the re-transport path R, respectively. The control unit 401 also receives sheet size information 406 from the operation unit 730 and the printer driver.

[0025] The light intensity adjustment unit 402 of the control unit 401 adjusts the light intensity by controlling the drive current value of the LED, which is the light-emitting element of the line sensor 71a, based on the set value determined in the light intensity adjustment flow described later in Figure 4. The line sensors 71a and 71b receive the light emitted from the LED and input a detection signal to the CPU 404 as a detection result. The CPU 404 of the control unit 401 determines the drive current value of the LED in the light intensity adjustment process described later, based on the voltage value obtained from the detection signals of the line sensors 71a and 71b.

[0026] After light intensity adjustment processing, the CPU 404 receives a detection signal from either the line sensor 71a or the line sensor 71b and detects the position of the sheet S being transported. The fault determination unit 403 determines if the line sensor is faulty based on the voltage value obtained from the detection signal received by the CPU 404. The image data correction unit 405 corrects the position of the image to be formed on the photosensitive drum 212 based on the result of detecting the position of the sheet S and the size information 406 of the sheet S.

[0027] (Schematic diagram showing the position of sheet S and line sensor) Figure 14 is a schematic diagram showing the position of the sheet S and the line sensor 71. The line sensor 71 is positioned in the width direction perpendicular to the conveying direction X of the sheet S and detects the edges of the sheet S in the width direction. The threshold range Y of the line sensor 71 is set according to the size of the sheet S. When both the sheet S and the line sensor 71 are normal, the sheet detection position Z is within the threshold range Y, and the sheet position is determined to be normal.

[0028] (light intensity adjustment) Referring to Figure 3, the method of adjusting the light intensity will be explained. The light intensity adjustment unit 402 of the control unit 401 causes the LED of the line sensor 71a or 71b to emit light at at least two arbitrary current values. Then, the detection voltage for each current value is obtained. The slope a and intercept b are determined from the two detection voltages, and a linear function is obtained as equation (1) when the voltage of the detection signal is VH and the driving current of the LED is I. VH = aI + b ... (1) A target voltage is predetermined for detecting sheet S using the line sensor 71. Based on equation (1) and the target voltage, a set current value for illuminating the LED is determined. This set current value obtained through light intensity adjustment is stored, and the LED is illuminated at the set current value to detect the position of sheet S.

[0029] (Flowchart showing methods for adjusting light intensity and correcting image formation position) Figure 4 is a flowchart showing the method for adjusting the light intensity and correcting the image formation position. In S101, the control unit 401 starts the printing process in response to a print start instruction input from the operation unit 730 or the printer driver. In S102, the control unit 401 adjusts the light intensity of the line sensor 71. Details of the light intensity adjustment are explained in Figure 5. In S103, the control unit 401 detects the position and tilt of the sheet S based on the detection signal, which is the detection result of the line sensor 71. In S104, the control unit 401 corrects the image formation position based on the detection result.

[0030] (Flowchart showing light intensity adjustment) Figure 5 is a flowchart showing the method of adjusting the light intensity. In S201, the control unit 401 transports the sheet S to the detection area of ​​the line sensor 71. In S202, the control unit 401 causes the LED to light up at an arbitrary first current value. In S203, the control unit 401 obtains a first voltage value from the detection signal of the line sensor 71.

[0031] In S204, the control unit 401 causes the LED to light up at an arbitrary second current value different from the first current value. In S205, the control unit 401 obtains a second voltage value from the detection signal of the line sensor 71. In S206, the control unit 401 uses the obtained first and second voltage values ​​and equation (1) to determine the set current value for illuminating the LED when sheet S is detected.

[0032] (Normal / abnormal determination of line sensor) Referring to Figure 6, the normal / abnormal determination of the line sensor during light intensity correction will be explained. There are cases where an abnormality occurs in the LED and the amount of light emitted does not change even when the current value is changed, or where an abnormality occurs in the line sensor and the amount of light received does not change even when the current value is changed. In such cases, the two voltage values ​​when the LED is driven with any two current values ​​will not change, or the amount of change will be small. Therefore, the amount of change (slope) of the two voltage values ​​when the LED is driven with any two current values ​​is calculated, and if the amount of change (slope) falls below a predetermined threshold, the control unit 401 determines that a fault has occurred. In Figure 6, the two voltage values ​​indicated by circles are the values ​​in the normal case. The two voltage values ​​indicated by triangles and squares are the values ​​in the abnormal case.

[0033] (Flowchart showing how to identify anomalies) Figure 7 is a flowchart illustrating the method for identifying abnormalities. Steps similar to those in Figure 5 are numbered as above, and their explanations are omitted here.

[0034] In S301, the control unit 401 calculates the difference (change) between the first voltage value and the second voltage value. It then determines whether the difference (change) is below a threshold. If it is greater than the threshold, it proceeds to S206; if it is below the threshold, it proceeds to S302. In S302, the control unit 401 determines that a malfunction has occurred in the line sensor 71 and displays a warning message on the operation unit 730 indicating that a malfunction has occurred in the line sensor 71. In S303, since the control unit 401 has determined that a malfunction has occurred in the line sensor 71, it terminates the process without performing light intensity adjustment. Furthermore, if light intensity adjustment is not performed, the subsequent sheet S position detection and image formation position correction are also not performed, and the printing process is terminated.

[0035] In this way, by illuminating the LED with two or more current values, it is possible to determine whether or not there is a malfunction in the line sensor. LEDs degrade over time, causing their light output to decrease and fluctuate with ambient temperature, so it is necessary to fine-tune the current flowing through the LED to adjust its light output. By determining whether or not a malfunction has occurred in the line sensor's light-emitting or light-receiving elements during this light output adjustment, it is possible to prevent the LED light output adjustment from failing properly, which would result in a correction error during subsequent sheet position detection and the output of an abnormal image. [Examples]

[0036] (Normal / abnormal determination of line sensor) Referring to Figure 8, the normal / abnormal determination of the line sensor during light intensity correction will be explained. If an abnormality occurs in the LED and the LED does not light up, or if an abnormality occurs in the line sensor, it may output a voltage value that is higher than the light intensity emitted by the LED. In such cases, the voltage value when the LED is driven with any two current values ​​may fall outside the predetermined normal range. If the voltage value falls outside the normal range, the control unit 401 determines that a malfunction has occurred. In Figure 8, the voltage values ​​indicated by circles are the values ​​in the normal case, and the voltage values ​​indicated by triangles are the values ​​in the abnormal case.

[0037] (Flowchart showing how to identify anomalies) Figure 9 is a flowchart illustrating the method for identifying abnormalities. Steps similar to those in Figure 7 are numbered as above, and their explanations are omitted here.

[0038] In S401, the control unit 401 determines whether the first voltage value is within the normal range. If it is within the range, the process proceeds to S402; otherwise, it proceeds to S302. In S402, the control unit 401 determines whether the second voltage value is within the normal range. If it is within the range, the process proceeds to S206; otherwise, it proceeds to S302.

[0039] In this way, by illuminating the LED with two or more current values, it is possible to determine whether or not a malfunction has occurred in the line sensor. [Examples]

[0040] (Normal / abnormal determination of line sensor) Referring to Figure 10, the normal / abnormal determination of the licensor during light intensity correction will be explained. In this embodiment, a malfunction is determined if either of the following two criteria is met: the malfunction determination based on the change in the first and second voltage values ​​as explained in Example 1, and the malfunction determination based on whether the voltage value is within the normal range as explained in Example 2. In Figure 10, the voltage values ​​indicated by circles are the values ​​when the condition is normal under all conditions. The voltage values ​​indicated by triangles are the values ​​when the condition is abnormal in the determination based on the change in voltage. The voltage values ​​indicated by squares are the values ​​when the condition is abnormal in the determination of whether the condition is within the normal range.

[0041] (Flowchart showing how to identify anomalies) Figure 11 is a flowchart illustrating the method for identifying an anomaly. Steps similar to those in Figure 9 are numbered as above, and detailed explanations are omitted here.

[0042] In S401, the control unit 401 determines whether the first voltage value is within the normal range. If it is within the range, proceed to S402; otherwise, proceed to S302. In S402, the control unit 401 determines whether the second voltage value is within the normal range. If it is within the range, proceed to S206; otherwise, proceed to S302. In S301, the control unit 401 calculates the difference (change) between the first voltage value and the second voltage value. Then, it determines whether the difference (change) is below a threshold. If it is greater than the threshold, proceed to S206; otherwise, proceed to S302.

[0043] In this way, by illuminating the LED with two or more current values, it is possible to determine whether or not a malfunction has occurred in the line sensor. [Examples]

[0044] (Normal / abnormal determination of line sensor) Referring to Figure 12, the normal / abnormal determination of the line sensor during light intensity correction will be explained.

[0045] In this embodiment, a method for determining whether a sheet S is present in the detection area of ​​the line sensor 71 will be described. In this embodiment, the line sensor 71 is configured so that no light-reflecting material, such as a white reference plate for adjustment, is placed in the area opposite the LED. When the LED is driven without the sheet S, in a normal case the detected voltage will be within a range close to the minimum value. In this embodiment, before adjusting the light intensity, abnormalities are determined by the voltage value when the LED is driven. In Figure 12, the voltage values ​​indicated by circles are the values ​​in a normal case. The voltage values ​​indicated by squares are the values ​​in an abnormal case.

[0046] (Flowchart showing how to identify anomalies) Figure 13 is a flowchart illustrating the method for identifying an anomaly. Steps similar to those in Figures 4 and 7 are numbered as above, and their explanations are omitted here.

[0047] In S501, the control unit 401 causes the LED to light up at an arbitrary first current value. In S502, the control unit 401 obtains a first voltage value from the detection signal of the line sensor 71. In S503, the control unit 401 determines whether the detected first voltage value is within a normal range. If it is within the range, proceed to S102; otherwise, proceed to S302.

[0048] In this way, by illuminating the LED when sheet S is not in the detection area, it is possible to determine whether or not an abnormality has occurred in the line sensor. [Explanation of Symbols]

[0049] S Seat 201 Image forming apparatus 401 Control Unit

Claims

1. A detection means having a light-emitting element and a light-receiving element for detecting a sheet, The system includes a control means for detecting the edge of the sheet in a direction perpendicular to the sheet transport direction based on the detection result of the aforementioned detection means, The detection device is characterized in that the control means obtains a first voltage value received by the photodetector when the light-emitting element is made to emit light at a first current value, and a second voltage value received by the photodetector when the light-emitting element is made to emit light at a second current value different from the first current value, and determines that an abnormality has occurred in the detection means if the first voltage value is greater than 0, the second voltage value is greater than 0, and the amount of change between the first voltage value and the second voltage value is less than or equal to a threshold, and determines that no abnormality has occurred in the detection means if the amount of change is greater than the threshold.

2. Equipped with display means, The detection device according to claim 1, characterized in that, if the control means determines that an abnormality has occurred in the detection means, it causes the display means to display a message indicating that an abnormality has occurred in the detection means.

3. The detection device according to claim 1, characterized in that, when the control means determines that no abnormality has occurred in the detection means, it adjusts the light intensity of the light-emitting element based on the first voltage value and the second voltage value.

4. A conveying means for transporting sheets, Image forming means for forming an image on a sheet, An image forming apparatus comprising a detection device according to any one of claims 1 to 3.

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