Detector and image formation device

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 technology]

[0002] Conventionally, in an image forming apparatus, as shown in Patent Document 1, a method is known in which a sensor detects the inclination of a sheet being conveyed and corrects the relative positional relationship between the sheet and an image to be formed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2012-3174 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when it is determined that an abnormality has occurred based on the results detected by the sensor, it is not possible to determine the cause of the abnormality. [Means for solving the problem]

[0005] In order to achieve the above object, the device comprises a detection means having a light-emitting element and a light-receiving element and detecting a sheet, and a control means which detects the edge of the sheet in a direction perpendicular to the sheet conveying direction based on the detection result of the detection means, wherein the control means acquires a first voltage value received by the light-receiving element when the light-emitting element is made to emit light at a first current value, and a second voltage value received by the light-receiving element when the light-emitting element is made to emit light at a second current value different from the first current value, and determines whether an abnormality has occurred in the detection means based on the amount of change between the first voltage value and the second voltage value. [Effects of the Invention]

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

[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] Flowchart showing how to adjust the light intensity [Figure 5] Flowchart showing how to adjust the light intensity [Figure 6] Diagram showing normal / abnormal judgment of line sensor [Figure 7] Flowchart showing normal / abnormal judgment of line sensor [Figure 8] Diagram showing normal / abnormal judgment of line sensor [Figure 9] Flowchart showing normal / abnormal judgment of line sensor [Figure 10] Diagram showing normal / abnormal judgment of line sensor [Figure 11] Flowchart showing normal / abnormal judgment of line sensor [Figure 12] Diagram showing normal / abnormal judgment of line sensor [Figure 13] Flowchart showing normal / abnormal judgment of line sensor [Figure 14] Schematic diagram showing the seat position and line sensor DETAILED DESCRIPTION OF THE INVENTION

[0008] The following describes embodiments of the present invention with reference to the drawings. Note that the following embodiments do not limit the scope of the invention as claimed, and not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention. [Example]

[0009] (Image forming device) Fig. 1 is a schematic 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 with reference to Figs.

[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 image formation condition settings with the host device 900, which may be a personal computer, image scanner, facsimile, etc., and the operation unit 730. The control unit 401 also performs signal processing and sequence control for various process devices.

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

[0012] The image forming apparatus main body 201A is equipped with an image forming unit 201B that forms an image on a sheet. An image reading device 202 is disposed above the image forming apparatus main body 201A and approximately horizontally relative to the image forming apparatus main body 201A. A discharge space V for discharging sheets is formed between the image reading device 202 and the image forming apparatus main body 201A.

[0013] The cassette feeding section 230 includes a feeding cassette 1 that accumulates sheets S, and a pickup roller 2 that feeds the sheets S stacked in the feeding cassette 1. The cassette feeding section 230 also includes a separation section that includes a feed roller 3 and a retard roller 4 that separate the sheets S sent out from the pickup roller 2.

[0014] The manual feed section 235 includes a manual feed tray 5 on which sheets S are stacked, and a pickup roller 502 that feeds the sheets S stacked on the manual feed tray 5. The manual feed section 235 also includes a separation section that includes a feed roller 503 and a retard roller 504 that separate the sheets S sent out from the pickup roller 502.

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

[0016] The secondary transfer unit 201D includes an intermediate transfer belt 216 wound around a drive roller 216a and a tension roller 216b. A primary transfer roller 219 is provided inside the intermediate transfer belt 216, contacting the intermediate transfer belt 216 at a position facing the photosensitive drum 212. The intermediate transfer belt 216 is rotated in the direction of the arrow by a drive roller 216a driven by a drive unit (not shown). A secondary transfer roller 217 that transfers an image formed on the intermediate transfer belt 216 to a sheet S is provided at a position facing the drive roller 216a of the secondary transfer unit 201D.

[0017] A fixing unit 201E is disposed above the secondary transfer roller 217, and a first pair of discharge rollers 225a, a second pair of discharge rollers 225b, and a double-sided reversing unit 201F are disposed above the fixing unit 201E. The double-sided reversing unit 201F is provided with a pair of reversing rollers 222 that can rotate forward and backward, and a re-conveying path R that conveys the sheet S, on whose first side an image has been formed, again to the image forming unit 201B.

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

[0019] (Operation of image forming device) 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 subjected to image processing, converted into an electrical signal, and 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, the surface of which has been 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 images formed on the photosensitive drums 212 are developed by the developers 214 of each color to be visualized as images. The images formed on each photosensitive drum are transferred onto the intermediate transfer belt 216 in a superimposed manner by applying a primary transfer bias to the primary transfer rollers 219. As a result, a color image is formed on the intermediate transfer belt 216.

[0021] In parallel with the image forming operation, sheets S are conveyed one by one to a pair of registration rollers 240 by a cassette feeding unit 230 or a manual paper feeding unit 235. Skew of the sheets S is corrected by the pair of registration rollers 240. The position of the sheet S is detected by a line sensor 71a disposed upstream of the pair of registration rollers 240, and the position of the electrostatic latent image formed on the photosensitive drum 212 is corrected in accordance with the detected position of the sheet S. The line sensor 71a or 71b and the control unit 401 can also be collectively referred to as a detection device disposed within the image forming apparatus 201.

[0022] After the skew of the sheet S and the electrostatic latent image formed on the photosensitive drum 212 are corrected, the sheet S is conveyed to the secondary transfer section 201D by the pair of registration rollers 240. In the secondary transfer section 201D, a secondary transfer bias is applied to the secondary transfer roller 217, so that the image formed on the intermediate transfer belt 216 is secondarily transferred onto the sheet S.

[0023] The sheet S onto which the image has been secondarily transferred is transported to the fixing unit 201E. The sheet S is subjected to heat and pressure in a nip formed by a pressure roller 220a and a heating roller 220b in the fixing unit 201E, whereby the unfixed image that has been secondarily transferred onto the sheet S is fixed. The sheet S onto which the image has been fixed is discharged to a discharge space V by a first discharge roller pair 225a or a second discharge roller pair 225b provided downstream of the fixing unit 201E, and is stacked on a paper discharge tray 223 in the discharge space V. When 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 a re-conveyance path R by a 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 a line sensor 71b arranged on the re-conveyance path R, and the formation position of an electrostatic latent image corresponding to the image on the second side that is formed on the photosensitive drum 212 is corrected in accordance with the detected position of the sheet S.

[0024] (Block diagram of licensor control) 2, the control of the line sensors 71a and 71b and the control of the image forming position based on the outputs from the line sensors 71a and 71b will be described. The control unit 401 receives outputs from the line sensors 71a and 71b, which are respectively arranged on the registration roller pair 240 and the re-conveyance path R. The control unit 401 also receives size information 406 of the sheet S from the operation unit 730 or 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 LEDs, which are the light-emitting elements of the line sensor 71a, based on the setting value determined in the light intensity adjustment flow described later in Fig. 4. The line sensors 71a and 71b receive light emitted from the LEDs and input detection signals as the detection results to the CPU 404. The CPU 404 of the control unit 401 determines the drive current value of the LEDs in the light intensity adjustment process described later, based on the voltage value determined from the detection signals of the line sensors 71a and 71b.

[0026] After the light amount adjustment process, the CPU 404 receives a detection signal from the line sensor 71a or 71b and detects the position of the sheet S being conveyed. A failure determination unit 403 determines whether the line sensor has failed based on a voltage value calculated from the detection signal received by the CPU 404. An image data correction unit 405 corrects the formation position of the image formed on the photosensitive drum 212 based on the result of detecting the position of the sheet S and size information 406 of the sheet S.

[0027] (Schematic diagram showing the position of the sheet S and the line sensor) 14 is a schematic diagram showing the position of the sheet S and the line sensor 71. The line sensor 71 is arranged in the width direction perpendicular to the conveying direction X of the sheet S, and detects the edge of the sheet S in the width direction. A threshold range Y is set for the line sensor 71 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) The method of adjusting the light intensity will be described with reference to Figure 3. 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 when the LED is emitted at each current value is obtained. The slope a and intercept b are found from the two detection voltages, and a linear function is found as equation (1) when the detection signal voltage is VH and the LED drive current is I. VH=aI+b (1) The target voltage for detecting the sheet S by the line sensor 71 is determined in advance, and the set current value for illuminating the LED is calculated based on the formula (1) and the target voltage. The set current value calculated by this light intensity adjustment is stored, and the LED is illuminated at the set current value to detect the position of the sheet S.

[0029] (Flowchart showing the method for adjusting the amount of light and correcting the image formation position) 4 is a flowchart showing a method for adjusting the light intensity and correcting the image forming position. In S101, the control unit 401 starts the print 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 will be described with reference to FIG. 5. In S103, the control unit 401 detects the position and tilt of the sheet S based on a detection signal that is the detection result of the line sensor 71. In S104, the control unit 401 corrects the image forming position based on the detection result.

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

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

[0032] (Line sensor normal / abnormal judgement) Referring to FIG. 6, the normal / abnormal determination of the line sensor during light intensity correction will be described. An abnormality may occur in the LED, causing the emitted light intensity to remain unchanged even when the current value is changed. Alternatively, an abnormality may occur in the line sensor, causing the received light intensity to remain unchanged even when the current value is changed. In such cases, the two voltage values ​​obtained when the LED is driven at two arbitrary current values ​​do not change, or the amount of change is small. Therefore, the amount of change (slope) between the two voltage values ​​obtained when the LED is driven at two arbitrary current values ​​is calculated. If the amount of change (slope) falls below a predetermined threshold, the control unit 401 determines that a malfunction has occurred. In FIG. 6, the two voltage values ​​indicated by circles are normal values. The two voltage values ​​indicated by triangles and squares are abnormal values.

[0033] (Flowchart showing how to determine abnormalities) Fig. 7 is a flowchart showing a method for determining an abnormality. Note that the same steps as those in Fig. 5 above are given the same numbers, and their explanation will be omitted here.

[0034] In S301, the control unit 401 obtains the difference (amount of change) between the first voltage value and the second voltage value. Then, it determines whether the difference (amount of change) is equal to or less than a threshold value. If it is greater than the threshold value, the process proceeds to S206, and if it is equal to or less than the threshold value, the process proceeds to S302. In S302, the control unit 401 determines that a malfunction has occurred in the line sensor 71, and causes the operation unit 730 to display a warning message 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, the process ends without adjusting the amount of light. Furthermore, if the light amount adjustment was not performed, the subsequent position detection of the sheet S and correction of the image formation position are not performed, and the printing process ends.

[0035] In this way, by lighting the LED with two or more current values, it is possible to determine whether an abnormality has occurred in the line sensor. Because the light intensity of LEDs decreases with age and varies with the ambient temperature, it is necessary to fine-tune the current flowing through the LED to adjust the light intensity. By determining whether a malfunction has occurred in the light-emitting or light-receiving elements of the line sensor during this light intensity adjustment and whether normal detection is being performed, it is possible to prevent the LED light intensity from being adjusted normally, resulting in a correction abnormality when detecting the subsequent sheet position, and the output of an abnormal image. [Example]

[0036] (Line sensor normal / abnormal judgement) With reference to FIG. 8, the determination of normality or abnormality of the line sensor during light intensity correction will be described. An abnormality may occur in the LED causing it to not light up, or an abnormality may occur in the line sensor causing it to output a voltage value that is greater than the amount of light 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 FIG. 8, the voltage values ​​indicated by circles are normal values, and the voltage values ​​indicated by triangles are abnormal values.

[0037] (Flowchart showing how to determine abnormalities) Fig. 9 is a flowchart showing a method for determining an abnormality. Note that the same steps as those in Fig. 7 above are given the same numbers, and their explanation will be 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, and if it is outside the range, the process 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, and if it is outside the range, the process proceeds to S302.

[0039] In this way, by lighting the LED with two or more current values, it is possible to determine whether or not an abnormality has occurred in the line sensor. [Example]

[0040] (Line sensor normal / abnormal judgement) With reference to FIG. 10, the normality / abnormality determination of the license sensor during light intensity correction will be described. In this embodiment, a failure is determined when either of two criteria is met: determining a failure based on the amount of change between the first voltage value and the second voltage value as described in embodiment 1, and determining a failure based on whether the voltage value is within the normal range as described in embodiment 2. In FIG. 10, the voltage values ​​indicated by circles are normal values ​​under either condition. The voltage values ​​indicated by triangles are abnormal values ​​when determining the amount of change. The voltage values ​​indicated by squares are abnormal values ​​when determining the normal range.

[0041] (Flowchart showing how to determine abnormalities) Fig. 11 is a flowchart showing a method for determining an abnormality. Note that the same steps as those in Fig. 9 above are given the same numbers, and detailed explanations will be 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, the process proceeds to S402, and if it is outside the range, the process 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, and if it is outside the range, the process proceeds to S302. In S301, the control unit 401 obtains the difference (amount of change) between the first voltage value and the second voltage value. Then, the control unit 401 determines whether the difference (amount of change) is equal to or less than a threshold value. If it is greater than the threshold value, the process proceeds to S206, and if it is equal to or less than the threshold value, the process proceeds to S302.

[0043] In this way, by lighting the LED with two or more current values, it is possible to determine whether or not an abnormality has occurred in the line sensor. [Example]

[0044] (Line sensor normal / abnormal judgement) With reference to FIG. 12, the determination of whether the line sensor is normal or abnormal during light amount correction will be described.

[0045] In this embodiment, a method of determining whether or not a sheet S is present in the detection area of ​​the line sensor 71 will be described. In this embodiment, the area of ​​the line sensor 71 facing the LED is configured so that no light-reflecting member, such as a white reference plate for adjustment, is disposed. When the LED is driven without the sheet S present, the detected voltage is normally within a range close to the minimum value. In this embodiment, an abnormality is determined based on the voltage value when the LED is driven before light intensity adjustment. In FIG. 12, the voltage values ​​indicated by circles are normal values. The voltage values ​​indicated by squares are abnormal values.

[0046] (Flowchart showing how to determine abnormalities) Fig. 13 is a flowchart showing a method for determining an abnormality. Note that the same steps as those in Fig. 4 and Fig. 7 are given the same numbers, and their explanations will be omitted here.

[0047] In S501, the control unit 401 causes the LED to emit light at an arbitrary first current value. In S502, the control unit 401 acquires 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, the process proceeds to S102; if it is outside the range, the process proceeds to S302.

[0048] In this way, by emitting light from the LED when the 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 device 401 Control Unit

Claims

1. a detection means having a light emitting element and a light receiving element for detecting a sheet; a control unit that detects an edge of the sheet in a direction perpendicular to the sheet conveying direction based on the detection result of the detection unit, The control means acquires a first voltage value received by the light receiving element when the light emitting element is caused to emit light at a first current value, and a second voltage value received by the light receiving element when the light emitting element is caused to emit light at a second current value different from the first current value, and determines whether or not an abnormality has occurred in the detection means based on the amount of change between the first voltage value and the second voltage value.

2. A display means is provided, The detection device according to claim 1, characterized in that, when the amount of change is equal to or less than a threshold value, the control means determines that an abnormality has occurred in the detection means and causes the display means to display a message indicating that an abnormality has occurred in the detection means.

3. The detection device described in claim 1, characterized in that if the change amount is greater than a threshold value, the control means determines that no abnormality has occurred in the detection means, and adjusts the light intensity of the light-emitting element based on the first voltage value and the second voltage value.

4. a detection means having a light emitting element and a light receiving element for detecting a sheet; a control unit that detects an edge of the sheet in a direction perpendicular to the sheet conveying direction based on the detection result of the detection unit, The control means acquires a first voltage value received by the light receiving element when the light emitting element is caused to emit light at a first current value, and determines that an abnormality has occurred in the detection means if the first voltage value is outside a predetermined range, and determines that no abnormality has occurred in the detection means if the first voltage value is within the predetermined range.

5. A display means is provided, 5. The detection device according to claim 4, wherein, when the control means determines that an abnormality has occurred in the detection means, the control means causes the display means to display a message indicating that an abnormality has occurred in the detection means.

6. The detection device described in claim 4, characterized in that when the control means determines that no abnormality has occurred in the detection means, it acquires a second voltage value received by the light receiving element when the light emitting element is made to emit light at a second current value different from the first current value, and adjusts the light intensity of the light emitting element based on the first voltage value and the second voltage value.

7. a conveying means for conveying a sheet; an image forming means for forming an image on a sheet; An image forming apparatus comprising: the detection device according to claim 1 .

Images