JP2013249149A - Device for detecting recording material, and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the following problem: in a period until the amount of LED light is stabilized, the amount of LED light is changed depending on the time from the start of LED light emission to an end position detection of a recording medium, so that accuracy of detecting the end position is decreased when a detection result of the end position is changed due to a difference in the amount of light.SOLUTION: A device for detecting an end position of a recording material includes: a reciprocating sensor unit; and a recording material sensor mounted on the sensor unit to detect a recording material by receiving light emitted from a light emitting part by a light receiving part. The recording material sensor detects an end position of a recording material on a side orthogonal to the conveyance direction of the recording material, while the sensor unit reciprocates, and corrects the result of detecting the end position of the recording material using a correction value corresponding to the time elapsed from the start of light emission from the light emitting part of the recording material sensor until when the end position of the recording material is detected.

Description

  The present invention relates to a recording material detection device for detecting an end position of a recording material, and an image forming apparatus such as a copying machine, a printer, a facsimile, or a composite machine including the recording material detection device.

  In a conventional image forming apparatus, a recording material is fed from a paper feed cassette by a paper feed roller and conveyed to an image forming unit. The recording material to be transported is transported due to various effects such as the difference in outer diameter of the transport roller, fluctuations in transport speed due to wear with the transport roller, and the friction resistance between the transport guide that guides the recording material and the recording material. In some cases, the sheet is conveyed in an oblique state (hereinafter also referred to as skew). When the recording material is conveyed while being skewed and the toner image on the photosensitive drum is transferred to the recording material, the image is printed in an oblique state with respect to the recording material. Therefore, in order to suppress the skew of the recording material in the image forming apparatus, the recording material tip is brought into contact with the pair of registration rollers and the conveying roller pair, and the recording material is aligned and then conveyed to the image forming unit. There are things that suppress skew. However, the configuration in which the leading edge of the recording material is abutted to suppress the skew is effective in the direction parallel to the recording material conveyance direction, but the positional deviation cannot be suppressed in the direction orthogonal to the recording material conveyance direction. In addition, in the configuration in which double-sided printing is performed separately from such skew feeding, the recording material that has passed through the fixing portion on the first side contracts due to the heat and pressure of the fixing portion, so the recording material size on the second side is the first side. In some cases, the end position parallel to the recording material conveyance direction is different from the recording material size.

  Therefore, in order to cope with the positional deviation in the direction orthogonal to the recording material conveyance direction, there is a configuration in which a recording material end position parallel to the recording material conveyance direction is detected. As a configuration for detecting the end position of the recording material, Patent Document 1 discloses a position where the photo interrupter is moved across the recording material in a direction orthogonal to the conveyance direction of the recording material, and the recording material blocks light from the reference position. The end position of the recording material is detected by the distance up to. A method of correcting a shift between the recording material and the image by relatively matching the position of the recording material and the image forming position is disclosed.

JP-A-9-124187

  As described in the prior art, when detecting the end position of the recording material by reciprocating the sensor, when detecting the end position of the recording material before the amount of light emitted from the light emitting unit is stabilized As a result, variations in the amount of light from the light-emitting portion will reduce the detection accuracy of the end position. On the other hand, when the end position of the recording material is detected after the amount of light emitted from the light emitting unit is stabilized, variation in the amount of light from the light emitting unit is suppressed, but the end position is detected until the amount of light stabilizes. This makes it difficult to detect the end position. Hereinafter, the detection accuracy of the light amount and the end position will be described with reference to FIGS.

  FIG. 14 is a schematic configuration diagram illustrating a recording material detection unit in the recording material edge position detection apparatus. A light emitting unit 111 and a light receiving unit 112 are mounted on the sensor unit 110. The light emitting unit 111 includes an LED, and irradiates the light receiving unit 112 with light. There is a slit 401 between the light emitting unit 111 and the light receiving unit 112, and light emitted from the light emitting unit 111 passes through the slit 401 and is received by the light receiving unit 112. As the sensor unit 110 moves in the direction of the arrow 402, the recording material P enters between the light emitting unit 111 and the light receiving unit 112. That is, the light from the light emitting unit 111 changes from the transmissive state to the light shielding state where the light is blocked by the recording material P, and accordingly, the output of the light receiving unit 112 changes.

  FIG. 15 is a timing chart showing an output signal of the light receiving unit 112. The horizontal axis represents time, and shows a change in the position of the sensor unit 110 that moves. The vertical axis indicates the output signal of the light receiving unit 112, that is, the amount of light received by the light receiving unit 112. Reference numeral 503 denotes the width of the slit 401. When the sensor unit 110 moves in a direction in which the recording material P is present and the recording material P starts to enter between the slits 401, the amount of light received by the light receiving unit 112 starts to decrease. Furthermore, as the movement of the sensor unit 110 proceeds, the range of light that is shielded by the recording material P in the slit width increases, so the amount of light further decreases. At the timing 507 when the recording material P is shielded from light over the entire slit width, the amount of light becomes the lowest.

  Reference numeral 501 denotes a transition of the light amount when the light amount from the light emitting unit 111 is high, and 502 denotes a transition of the light amount when the light amount from the light emitting unit 111 is low. Reference numeral 505 denotes a threshold for determining that the end position of the recording material has been detected, and it is determined that the end of the recording material P has been detected at a timing when the amount of light falls below the threshold. 505 is actually a reference voltage for the comparator circuit. When the light quantity is higher than the reference voltage for 505, the comparator circuit outputs a high level, and when it is low, it outputs a low level. The timing when the light quantity falls below the threshold 505 differs between the case where the light quantity is high 501 and the case where the light quantity is low 502. Reference numeral 504 denotes a difference in timing that falls below the threshold 505 due to a difference in light quantity. Since the threshold value 505 is constant, an error occurs at a timing lower than the threshold value due to a difference in the amount of light. The error causes the end position of the recording material P to be different even though the end position is the same. It becomes the cause which will be detected.

  FIG. 16 is a diagram showing the transition of the amount of light after the LED starts to emit light. It is known from the characteristics of the device that the amount of light stabilizes after a certain amount of time has elapsed since the start of light emission. Specifically, the amount of light emission gradually decreases as the internal resistance increases due to the internal temperature increase of the LED, and the amount of light stabilizes when the internal temperature increase reaches saturation. It takes several seconds to several tens of seconds to stabilize. For this reason, the amount of LED light changes depending on the time from the start of light emission of the LED to the detection of the end position of the recording material. Therefore, as shown in FIG. 15 above, a change in the detection result of the end position due to the difference in the amount of light occurs.

  The invention according to the present application has been made in view of the above situation, and an object thereof is to suppress a decrease in detection accuracy of the end position of the recording material due to a change in the light amount of the light emitting unit.

  To achieve the above object, the present invention provides a sensor unit that reciprocates, and a recording material detection that is mounted on the sensor unit and detects the presence or absence of a recording material by receiving light emitted from a light emitting unit by a light receiving unit. A recording material end position detecting device having a sensor, wherein the recording material detection sensor detects an end position of the recording material on a side orthogonal to the recording material conveyance direction while the sensor unit is reciprocating. The end position of the recording material is determined using a correction value corresponding to the elapsed time from the start of light emission from the light emitting unit of the recording material detection sensor until the end position of the recording material is detected. The detected detection result is corrected.

  According to the configuration of the present invention, a decrease in the detection accuracy of the recording material end position due to a change in the light amount of the light emitting unit is suppressed.

The figure which shows the structure of the recording material edge position detection device Block diagram showing operation control of recording material edge position detection device The figure which showed the state which has detected the edge part position of the recording material P Graph showing the output value of the recording material detection sensor and the rotation angle of the crank arm Schematic configuration diagram of an image forming apparatus Flowchart showing a method for adjusting the main scanning writing position during image formation for single-sided printing A correction table showing correction values for correcting the detection result of the end position of the recording material P in accordance with the elapsed time since the LED which is the light emitting unit 111 emits light. Schematic configuration diagram of an image forming apparatus Flow chart showing a method of adjusting the main scanning writing position when forming an image for duplex printing A correction table indicating correction values for correcting the detection result of the end position of the recording material P according to the size of the recording material P when performing duplex printing. A flowchart showing a method for correcting a correction value according to a temperature detected by a temperature sensor. A flowchart showing a method of correcting the correction value according to the elapsed time from the end of the previous image formation to the start of the time image formation. Flow chart showing the calibration operation for measuring the light quantity reduction characteristic of the LED Schematic configuration diagram of light emitting part and light receiving part of recording material edge position detection device Timing chart showing output signal of light receiving unit 112 The figure which showed transition of the light quantity after starting the light emission of LED

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following embodiments do not limit the invention according to the claims, and all combinations of features described in the embodiments are not necessarily essential to the solution means of the invention.

(First embodiment)
FIG. 1 is a diagram showing a configuration of a recording material edge position detection device. The recording material end position detection device has a crank arm 102 as a rotating member that is rotatably supported around a crankshaft 101. Here, the crank arm 102 is configured in a disc shape, but may be configured in a rod-shaped link member. One end of the connecting link 104 is rotatably connected to the crank arm 102 at a connecting portion 103 on the crank arm 102. A sensor unit 110 is connected to the connecting portion 105 that is the other end of the connecting link 104. The crank arm 102 is rotated by a crank arm driving unit (not shown). The sensor unit 110 is configured to reciprocate on a straight line connecting the crankshaft 101 that is the rotation center of the crank arm 102 and the connecting portion 105 with the rotation of the crank arm 102. The sensor unit 110 is equipped with a light emitting unit 111 and a light receiving unit 112 as recording material detection sensors. The light emitting unit 111 uses an LED as a light source. A slit 401 is disposed on the light receiving surface of the light receiving unit 112, and receives light emitted from the light emitting unit 111 through the gap of the slit 401. The light emitting unit 111 and the light receiving unit 112 of the recording material detection sensor are combined to form a recording material detection sensor. As the crank arm 102 rotates once, the sensor unit 110 reciprocates once.

  Here, the light emitting unit 111 and the light receiving unit 112 are opposed to detect the presence or absence of a recording material as a transmission type recording material detection sensor. However, the light emitting unit 111 and the light receiving unit 112 are arranged on the same surface. It is also possible to detect the presence or absence of a recording material as a reflective recording material detection sensor.

  When there is no blocking between the light emitting unit 111 and the light receiving unit 112, the light receiving unit 112 can receive light from the light emitting unit 111. When the recording material P exists between the light emitting unit 111 and the light receiving unit 112, the light from the light emitting unit 111 is blocked by the recording material P, so that the amount of light received by the light receiving unit 112 decreases. Accordingly, the recording material detection sensor can detect whether or not the recording material P exists on the optical path between the light emitting unit 111 and the light receiving unit 112. Further, the end of the recording material P can be detected by detecting the output of the light receiving unit 112 and detecting the change point of the output, which means switching of the presence or absence of the recording material P.

  FIG. 2 is an example of a block diagram illustrating operation control of the recording material edge position detection device. 2A, the CPU 201 is connected to the light emitting unit 111 and the light receiving unit 112 of the recording material detection sensor, and detects the output of the light receiving unit 112 when the light emitting unit 111 is turned on. When there is no recording material P between the light emitting unit 111 and the light receiving unit 112, the output value of the light receiving unit 112 becomes large and the output value is detected as High. When the recording material P exists between the light emitting unit 111 and the light receiving unit 112, the output value of the light receiving unit 112 is reduced by being shielded by the recording material P, and the output value is detected as Low.

  Further, the CPU 201 controls the operation of the crank arm driving unit 230, and the crank arm 102 rotates by the driving force from the crank arm driving unit 230. The crank arm driving unit 230 is a rotary motor such as a stepping motor, and can perform angle control and angular velocity control based on a signal from the CPU 201. The CPU 201 can calculate the rotation angle of the crank arm 102 by a control signal sent to the crank arm driving unit 230. For example, since the number of drive pulses when the stepping motor rotates once is determined, the rotation angle of the stepping motor can be calculated by counting the number of drive pulses of the stepping motor by the CPU 201. If the driving force is transmitted from the stepping motor to the crank arm 102 directly or via a gear or the like, the rotation angle of the crank arm 102 can be calculated based on the rotation angle and gear ratio of the stepping motor. it can.

  As shown in FIG. 2B, the crank arm driving unit 230 may be a rotary motor such as a DC brush motor or a DC brushless motor. At this time, the rotation angle of the crank arm 102 is detected by a crank arm angle detection unit 250 such as an encoder and sent to the CPU 201. The CPU 201 can perform angle control and angular velocity control based on a signal from the crank arm angle detection unit 250. Further, the rotation angle of the crank arm 102 can be calculated from a signal from the crank arm angle detection unit 250.

  FIG. 3 is a diagram illustrating a state in which the end position of the recording material P is detected. The recording material P is conveyed in the direction of the arrow 320. The recording material end position detection device is arranged so that the sensor unit 110 reciprocates in the direction of an arrow 322 perpendicular to the conveyance direction of the recording material P. The crank arm 102 is supported by the crankshaft 101 and rotates in the direction of the arrow 130. The crank arm 102 can also rotate in the direction opposite to the arrow 130. The crank arm 102 rotates in one direction while the end position of the recording material P is detected.

  As the crank arm 102 is rotated by the crank arm driving unit, the sensor unit unit 110 reciprocates in the direction of the arrow 322. If the recording material P does not exist on the optical path of the light emitting unit 111 and the light receiving unit 112 of the recording material detection sensor, the output of the recording material detection sensor becomes High (hereinafter also referred to as “no recording material”). If the recording material P exists on the optical path of the light emitting unit 111 and the light receiving unit 112 of the recording material detection sensor, the output of the recording material detection sensor becomes Low (hereinafter also referred to as “with recording material”). When the sensor output changes from High to Low or from Low to High, it can be said that the end of the recording material P exists on the optical path of the light emitting unit 111 and the light receiving unit 112 of the recording material detection sensor. Therefore, the sensor unit 110 is disposed and reciprocated so that the optical paths of the light emitting unit 111 and the light receiving unit 112 of the recording material detection sensor pass through the end of the recording material, thereby being parallel to the conveyance direction of the recording material P. The end position of the recording material can be detected. When the end position of the recording material P is detected, the recording material P may be transported or stopped.

  Next, a method for obtaining the distance from the crankshaft 101 to the connection part 105 of the sensor unit part 110 will be described. As shown in FIG. 1, the distance between the crankshaft 101 and the connecting portion 103 is R, and the length from the connecting portion 103 to the connecting portion 105 of the connecting link 104 is L. Furthermore, an angle formed by a straight line 122 connecting the crankshaft 101 and the connecting portion 105 and a straight line 123 connecting the crankshaft 101 and the connecting portion 103 is θ [rad] (hereinafter also referred to as “crank arm angle”). And At this time, the distance X from the crankshaft 101 to the connecting portion 105 can be expressed by the following equation.

Therefore, if the crank arm angle θ is obtained, the position of the sensor unit 110 can be obtained. While rotating the crank arm 102 to reciprocate the sensor unit 110, the output value of the recording material detection sensor is detected. Then, the distance from the crankshaft 101 to the end position of the recording material P can be calculated by obtaining the crank arm angle θ when the end of the recording material P is detected, that is, the rotation amount of the crank arm 102. That is, the crank arm angle θ can be said to be information regarding the amount of rotation of the crank arm 102.

  FIG. 4 is a graph showing the output value of the recording material detection sensor and the rotation angle of the crank arm. As described above, when the output value of the recording material detection sensor is High, there is no recording material, and when the output value is Low, the recording material is present. The horizontal axis indicates the rotation angle of the crank arm. The rotation angle of the crank arm during the period when the output value of the recording material detection sensor is High is φ. Here, as an example, since the crank arm driving unit uses a stepping motor, the rotation angle Φ of the crank arm in a predetermined period can be calculated by the CPU 201. In this way, the rotation angle φ of the crank arm is calculated during the period when the output value of the recording material detection sensor is High. When the rotation angle φ of the crank arm is obtained, the crank arm angle θ is half of the rotation angle φ of the crank arm due to the geometric relationship of the crank mechanism.

Thus, the distance from the crankshaft 101 to the connection portion 105 of the sensor unit 110 can be obtained by substituting the value of the rotation angle of the crank arm obtained by the equation (2) into the equation (1). Furthermore, by adding a distance Y from the predetermined connecting portion 105 to the light path of the light emitting portion 111 and the light receiving portion 112 of the recording material detection sensor to this value, the distance from the crankshaft 101 to the end position of the recording material P is added. The distance can be determined.

  In this way, the period during which the recording material P is not detected by the recording material detection sensor is detected. By calculating the rotation angle of the crank arm from there, detection of the end position of the recording material can be started regardless of the stop position of the sensor, and a dedicated drive source or member is used to reciprocate the sensor. Therefore, it is possible to accurately detect the end position of the recording material.

  Here, the method for obtaining the crank arm rotation angle by detecting the period when the output of the recording material detection sensor is High (no recording material) has been described, but the present invention is not limited to this. For example, the rotation angle of the crank arm can be obtained by detecting the period when the output of the recording material detection sensor is Low (with recording material). Here, as an example, the configuration using the crank arm has been described as the configuration for reciprocating the sensor. However, if the configuration is such that the end position of the recording material P can be detected by reciprocating the sensor, It is not limited.

  Next, an image forming apparatus provided with a recording material edge position detection device will be described. FIG. 5 is a schematic configuration diagram of the image forming apparatus. Here, a laser printer (hereinafter also referred to as an “image forming apparatus”) as an example of an image forming apparatus will be described. As an image forming apparatus, an image forming apparatus such as a copying machine, a facsimile, or a complex machine of these is used. It may be.

  The image forming apparatus includes a drum-type electrophotographic photosensitive member (hereinafter also referred to as “photosensitive drum”) 1 as an image carrier. The photosensitive drum 1 is rotatably supported and is driven to rotate at a predetermined process speed in the direction of an arrow by a driving unit (not shown). Around the photosensitive drum 1, a charging roller 2, an exposure device 3, a developing device 4, a transfer roller 5, and a cleaning device 7 are sequentially arranged along the rotation direction. In addition, a paper feed cassette 10 that stores a recording material P as paper is disposed below the image forming apparatus. Further, the paper feeding roller 11, the registration roller 8, the recording material edge position detecting device 100, the top sensor 9, the fixing device 6, the fixing paper discharging roller 12, the paper discharging roller 13, the discharge roller in order along the conveyance path of the recording material P. A paper tray 14 is arranged. In addition, a motor 17 is provided as a drive source for each unit.

  Next, the operation of the image forming apparatus will be described. The photosensitive drum 1 that is rotationally driven in the direction of the arrow by a photosensitive drum driving unit (not shown) is uniformly charged to a predetermined polarity and a predetermined potential by the charging roller 2. The surface of the charged photosensitive drum 1 is exposed based on the image information by the exposure means 3 including a laser optical system on the surface, and the charge of the exposed portion is removed to form an electrostatic latent image. The operation of the exposure unit 3 is controlled by the CPU 201 which is a control unit. The electrostatic latent image is developed by the developing device 4. The developing device 4 has a developing roller 41, and a developing bias is applied to the developing roller 41 to attach toner to the electrostatic latent image on the photosensitive drum 1 and develop it as a toner image.

  The toner image is transferred to the recording material P by the transfer roller 5. The recording material P is housed in a paper feeding cassette 10, fed by a paper feeding roller 11, conveyed by a registration roller 8, and passes through a recording material edge position detection device 100 and a top sensor 9, and the photosensitive drum 1. And a transfer nip between the transfer roller 5 and the transfer roller 5. At this time, the leading edge of the recording material P is detected by the top sensor 9 and is synchronized with the toner image on the photosensitive drum 1. That is, the top sensor 9 is a leading edge detection sensor that detects the leading edge of the recording material P. A transfer bias is applied to the transfer roller 5, whereby the toner image on the photosensitive drum 1 is transferred to a predetermined position on the recording material P. The recording material P carrying the unfixed toner image on the surface by transfer is conveyed to the fixing device 6, and the unfixed toner image is heated and pressurized and fixed on the surface of the recording material P.

  The recording material P on which the toner image is fixed by the fixing device 6 is conveyed by the fixing paper discharge roller 12 and discharged onto the paper discharge tray 14 by the paper discharge roller 13. When an image is formed on the second surface of the recording material P, a part of the recording material P (tip portion) is once discharged to the outside of the image forming apparatus, and then the rotation direction of the discharge roller 13 is switched. By switching the rotation direction and switching back, the recording material P is conveyed to the double-sided roller and the refeed roller 51 in the double-sided conveyance path. The recording material P, which has been reversed upside down in this way, is conveyed again to the photosensitive drum 1 by the registration rollers 8 and printing on the second surface of the recording material P is performed. Although an image forming apparatus that forms a monochrome image has been described here as an example, the present invention is not limited to this, and the present invention can be applied to an image forming apparatus that forms a color image.

  Next, referring to FIGS. 6 and 7, when an image is formed on the recording material P in the image forming apparatus, the recording material end position detecting device 100 detects the end of the recording material P and adjusts the image writing position. The method of performing will be described. FIG. 6 is a flowchart showing a method of adjusting the main scanning writing position when forming an image for single-sided printing. In step S201, the CPU 201 starts printing upon receiving an image formation command. In step S <b> 202, the CPU 201 starts light emission of the LED that is the light emitting unit 111 of the recording material edge position detection device 100 when printing is started. In step S <b> 203, the CPU 201 starts a timer for measuring the elapsed time from the start of LED light emission. In step S <b> 204, the CPU 201 feeds the recording material P from the paper feed cassette 10 by the paper feed roller 11. The recording material P fed to the paper feed roller 11 is subsequently conveyed by the registration roller 8.

  In step S <b> 205, the CPU 201 determines whether the top sensor 9 has detected the leading edge of the recording material P. When the top sensor 9 detects the leading edge of the recording material P, the motor 17 starts to be driven. In step S <b> 206, the CPU 201 drives the recording material end position detection device 100 with the driving force of the motor 17 to detect the end position of the recording material P parallel to the conveyance direction of the recording material P. In step S207, the CPU 201 stops the timer at the timing when the end position of the recording material P is detected, and reads the timer value. In step S208, the CPU 201 corrects the end position detection result in accordance with the read timer value.

  Here, correction of the detection result of the end position according to the timer value will be described. FIG. 7 is a correction table showing correction values for correcting the detection result of the end position of the recording material P according to the elapsed time since the LED which is the light emitting unit 111 emits light. When the elapsed time from the start of light emission is short, as described above with reference to FIG. 16, the light amount fluctuation is large while the LED temperature is rising, and the light amount is higher than that at the time of stabilization. Therefore, the correction value is set to a larger value as the elapsed time until the light quantity is stabilized is shorter. As the elapsed time from the start of light emission becomes longer, the rising temperature of the LED is saturated and the light quantity is stabilized. Therefore, the correction value decreases as the elapsed time becomes longer. Here, the correction value is set to 0 when the elapsed time becomes 30 seconds or more. Although specific correction values are shown in the table of FIG. 7, the present invention is not limited to this. For example, the correction value can be set as appropriate depending on the individual difference of the LEDs, and the division of elapsed time can also be set as appropriate.

  Note that a negative correction value for correcting the detection result of the end position of the recording material P indicates that the correction value is subtracted from the actual measurement result. This will be described. As shown in FIG. 15, when the light amount of the light emitting unit 111 is high, the time required to detect the end position of the recording material P becomes long. That is, this is detected when the distance from the recording material edge position detection device 100 to the detection of the edge position of the recording material P is long. That is, in the recording material end position detection apparatus 100, the light amount is stable because the end position of the recording material P is set to be detected accurately in a state where the light amount of the LED that is the light emitting unit 111 is stable. If the end position of the recording material P is detected with a high light amount before the recording, the distance is longer than the actual end position due to the influence of the high light amount. Therefore, by using the table of FIG. 7, in the case of a high light amount before the light amount is stabilized, the detection result of the detected end position of the recording material P is corrected with a correction value, thereby suppressing a decrease in detection accuracy. it can.

  There are various reasons why the detection time of the end position of the recording material P by the recording material end position detection device 100 changes. As a specific example, the end position of the recording material P is detected. After the light emission of the light emitting unit 111 is started, the time until the recording material P is conveyed to the recording material end position detecting device 100 changes. For example, when the recording material P is not normally performed from the paper feed cassette 10 and the paper feed retry is performed again, the paper feed retry may be successful once, or may be required twice or three times. In some cases. As a result, the time until the recording material edge position detecting device is conveyed changes, and the detection result of the edge position of the recording material P varies depending on the light amount of the light emitting unit 111 at that time. However, as described above, the light amount of the light emitting unit 111 is corrected by correcting the detection result according to the elapsed time from when the light emitting unit 111 starts light emission until the end position of the recording material P is detected. This makes it possible to suppress a decrease in the detection accuracy of the recording material end position due to the change of the recording material.

  The correction table may be stored in a read-only memory (ROM) built in the CPU 201 or a writable nonvolatile memory (NVRAM). When storing the correction table in the NVRAM, for example, before shipment of the image forming apparatus, the actual LED light quantity is measured for each unit, and the data is used as the correction table, so that image formation corresponding to individual differences of the LEDs is performed. A correction table suitable for each apparatus can be created.

  Returning to the flowchart of FIG. In step S209, the CPU 201 corrects the detection result of the end position of the recording material P with the correction value in the correction table in FIG. 7 according to the timer value read in step S208. For example, a case where the detection result of the end position of the recording material P is 0.500 mm will be described. In this case, if the timer value is 2.5 seconds, the correction value is -0.050 mm from the correction table of FIG. Therefore, 0.500 mm−0.050 mm = 0.450 mm is the end position of the recording material P. If the timer value is 5.5 seconds, the correction value is -0.030 mm from the correction table of FIG. Therefore, 0.500 mm−0.030 mm = 0.470 mm is the end position of the recording material P. As described above, if the timer value is 30 seconds or more, the detection result is directly used as the end position of the recording material P without correction.

  In S210, the CPU 201 determines an adjustment amount of the image writing position in the direction (main scanning direction) orthogonal to the conveyance direction of the recording material P according to the end position of the recording material P that has been corrected according to the timer value. To do. In step S211, the CPU 201 adjusts the image writing position in the main scanning direction of the exposure unit 3 based on the adjustment amount determined in step S210 after a predetermined time from the timing when the top sensor 9 detects the leading edge of the recording material P, and forms an image. . In step S212, the CPU 201 discharges the recording material P on which image formation has been performed to the outside of the image forming apparatus.

  As described above, in order to detect the end position of the recording material P, according to the elapsed time from the start of the light emission of the light emitting unit 111 without waiting until the light amount emitted from the light emitting unit 111 is stabilized, By correcting the detection result of the end position, it is possible to suppress a decrease in detection accuracy of the end position of the recording material due to a change in the light amount of the light emitting unit 111. Therefore, it is possible to shorten the time until the end position of the recording material P is detected, and it is also possible to shorten the time for emitting the LED as the light emitting unit 111, and thus it is possible to suppress the shortening of the LED life.

(Second Embodiment)
In the first embodiment, the method for correcting the detection result of the end position of the recording material P when performing single-sided printing has been described. In the present embodiment, a method for correcting the detection result of the end position of the recording material P when performing duplex printing will be described. In addition, description here is abbreviate | omitted about the structure similar to previous 1st Embodiment.

  FIG. 8 is a schematic configuration diagram of the image forming apparatus. The difference from FIG. 5 of the first embodiment is that the recording material edge position detection device 100 is disposed on the double-sided conveyance path and the double-sided sensor 15 is provided on the double-sided conveyance path. Further, the motor 17 which is a driving source of the recording material edge position detecting device 100 drives the double-sided roller 16 and the refeed roller 51 in the double-sided conveyance path. Other members similar to those of the image forming apparatus in FIG. 5 are denoted by the same reference numerals, and description thereof is omitted here.

  9 and 10, when an image is formed on the recording material P in the image forming apparatus, the recording material end position detecting device 100 detects the end of the recording material P and adjusts the image writing position. A method will be described. FIG. 9 is a flowchart showing a method of adjusting the main scanning writing position when forming a double-sided printed image. Note that the same processes as those in the flowchart of FIG.

  In step S201, the CPU 201 starts printing upon receiving an image formation command. In step S <b> 204, the CPU 201 feeds the recording material P from the paper feed cassette 10 by the paper feed roller 11 when printing is started. The recording material P fed to the paper feed roller 11 is subsequently conveyed by the registration roller 8. In step S <b> 205, the CPU 201 determines whether the top sensor 9 has detected the leading edge of the recording material P. The top sensor 9 is arranged on the upstream side in the conveyance direction of the recording material P from the recording material edge position detection device 100. When the top sensor 9 detects the leading edge of the recording material P, the CPU 201 starts to emit light from the LED that is the light emitting unit 111 of the recording material edge position detection device 100 in S202. In step S <b> 211, the CPU 201 forms an image on the surface of the recording material P after a predetermined time from the timing when the top sensor 9 detects the leading edge of the recording material P.

  In step S <b> 301, the CPU 201 determines whether or not the double-sided printing is to perform image formation on the back surface after the image formation on the front surface of the recording material P. If it is not duplex printing, the recording material P is discharged out of the image forming apparatus. In the case of duplex printing, in S302, the CPU 201 determines whether it is a reversal timing for reversing the recording material P. When the reversal timing is reached, in step S303, the CPU 201 reversely drives the paper discharge roller 13 to convey the recording material P toward the double-sided conveyance path. After conveying the recording material P toward the double-sided conveyance path, the CPU 201 determines whether or not the leading edge of the recording material P is detected by the double-sided sensor 15 in S304. When the leading edge of the recording material P is detected by the double-sided sensor 15, in S <b> 206, the CPU 201 drives the recording material edge position detection device 100 by the driving force of the motor 17, and the recording material P parallel to the conveyance direction of the recording material P is recorded. The end position of is detected. In step S <b> 305, the CPU 201 detects the end position of the recording material P by the recording material end position detection apparatus 100, and then corrects the detection result of the end position according to the size of the recording material P.

  Here, correction of the detection result of the end position according to the size of the recording material P will be described. FIG. 10 is a correction table showing correction values for correcting the detection result of the end position of the recording material P in accordance with the size of the recording material P when performing double-sided printing. In the present embodiment, the light emission of the LED is started at the timing when the top sensor 9 detects the leading edge of the recording material P. Therefore, there is no change in the elapsed time from the start of light emission due to the paper feed retry process as described in the first embodiment. In double-sided printing, the elapsed time from when the recording material P is detected by the top sensor 9 until the end position is detected changes according to the size of the recording material P (length in the transport direction). This is because the time taken for the recording material P to switch back to the double-sided conveyance path is determined according to the size of the recording material P (length in the conveyance direction). Therefore, in the correction table of FIG. 10, the correction value is determined based on the conveyance time corresponding to the size of the recording material P. The correction table in FIG. 10 is based on the conveyance time when the recording material P is conveyed at 1/1 speed, but is not limited to this. For example, a plurality of similar correction tables corresponding to when the recording material P is conveyed at 1/2 speed or when it is conveyed at 1/3 speed are corrected from the correction table according to the size and conveying speed of the recording material P. It is also possible to determine the value.

  When the elapsed time from the start of light emission is short, as described above with reference to FIG. 16, the light amount fluctuation is large while the LED temperature is rising, and the light amount is higher than that at the time of stabilization. Therefore, the correction value is set to a larger value as the elapsed time until the light quantity is stabilized is shorter. The correction table may be stored in a read-only memory (ROM) built in the CPU 201 or a writable nonvolatile memory (NVRAM). When storing the correction table in the NVRAM, for example, before shipment of the image forming apparatus, the actual LED light quantity is measured for each unit, and the data is used as the correction table, so that image formation corresponding to individual differences of the LEDs is performed. A correction table suitable for each apparatus can be created.

  Returning to the flowchart of FIG. In step S209, the CPU 201 corrects the detection result of the end position of the recording material P with the correction value of the correction table in FIG. For example, a case where the detection result of the end position of the recording material P is 0.250 mm will be described. In this case, if the size of the recording material P is A4L, the correction value is −0.060 mm from the correction table of FIG. Therefore, 0.250 mm−0.060 mm = 0.190 mm is the end position of the recording material P. When the size of the recording material P is A3P, the correction value is −0.040 mm from the correction table of FIG. Therefore, 0.250 mm−0.040 mm = 0.210 mm is the end position of the recording material P.

  In S210, the CPU 201 adjusts the image writing position in the direction (main scanning direction) perpendicular to the conveyance direction of the recording material P according to the end position of the recording material P that has been corrected according to the size of the recording material P. To decide. In step S <b> 306, the CPU 201 determines whether the top sensor 9 has detected the leading edge of the recording material P conveyed toward the registration roller again by the refeed roller 51. In step S307, the CPU 201 adjusts the image writing position in the main scanning direction of the exposure unit 3 based on the adjustment amount determined in step S305 after a predetermined time from the timing when the top sensor 9 detects the leading edge of the recording material P, and forms an image. . In step S212, the CPU 201 discharges the recording material P on which image formation has been performed to the outside of the image forming apparatus.

  In this way, when performing double-sided printing, in order to detect the end position of the recording material P, the light emission unit 111 emits light by correcting the detection result of the end position according to the size of the recording material P. It is possible to suppress a decrease in the detection accuracy of the end position of the recording material due to a change in the light amount of the light emitting unit 111 without waiting for the light amount to be stabilized. In the configuration in which the recording material edge position detection device 100 is disposed in the double-sided conveyance path when performing double-sided printing, if the distance from the paper feed cassette 10 to the detection position of the recording material P is long, the paper feed timing is When the light emission of the LED is started, the light emission time may become too long. As a result, the lifetime of the LED may be shortened. However, the detection accuracy can be improved by starting LED emission after the recording material P is detected by the top sensor 9 as in the present embodiment, and correcting the detection result of the end position according to the size of the recording material P. It is possible to suppress the decrease of the LED and shorten the life of the LED. Further, since there is no need to wait until the light emitting unit 111 is stabilized, the time until the end position of the recording material P is detected can be shortened. Further, the time from when the recording material P is detected by the top sensor to when it is detected by the recording material edge position detection device 100 can be obtained from the size of the recording material P and the conveyance speed. Correction can also be performed without using a timer for counting time.

  In the present embodiment, as an example of the image forming apparatus, the configuration in which the recording material end position detecting device 100 is disposed in the double-sided conveyance path as illustrated in FIG. 8 is described, but the present invention is not limited to this. For example, as shown in FIG. 5 of the first embodiment, as shown in FIG. 8 on the conveyance path from the paper feed cassette 10 until image formation is started and on the downstream side in the recording material conveyance direction. It is also possible to arrange the recording material edge position detection device 100 on the both-side conveyance path and on both of them. In that case, the writing position of the first surface of the recording material P is corrected based on the detection result of the recording material end position detecting device 100 arranged at the position shown in FIG. 5, and the recording material P is arranged at the position shown in FIG. The writing start position of the second surface of the recording material P, which is the back surface of the first surface, is corrected based on the detection result of the recording material edge position detection device 100.

(Third embodiment)
In the present embodiment, according to the temperature for the correction value for correcting the detection result of the end position of the recording material P according to the temperature detected by the temperature sensor that can detect the temperature around the LED that is the light emitting unit 111. A method of correcting the detection result after making the correction will be described. In addition, description here is abbreviate | omitted about the structure similar to previous 1st Embodiment or 2nd Embodiment.

  FIG. 11 is a flowchart showing a method of correcting the correction value according to the temperature detected by the temperature sensor. In step S401, the CPU 201 measures the ambient temperature of the LED using a temperature sensor. Note that the light quantity of the LED is known to decrease as the temperature of the LED increases due to device characteristics. When the temperature around the LED is already high before the light emission starts, the LED temperature rise after the LED starts light emission is small, so the light amount decrease is small. On the other hand, when the temperature around the LED is a low temperature before the start of light emission, the LED temperature rises after the LED starts to emit light increases, and the light amount decreases. In view of this phenomenon, the correction value is corrected in the present embodiment.

  In S402, the CPU 201 determines whether or not the temperature around the LED is 50 ° C. or higher. If it is 50 ° C. or higher, the CPU 201 sets all correction values to 0 in S403. That is, the output result of the end position of the recording material P is not corrected. This is because the temperature around the LED is high before the start of light emission, so that the temperature rise after the LED starts to emit light is small, and the decrease in light quantity is small.

  If it is not 50 ° C. or higher, in S404, the CPU 201 determines whether or not the temperature around the LED is 40 ° C. or higher. If it is 40 ° C. or higher, in S405, the CPU 201 sets the correction value to 50% and if it is 40 ° C. or higher, the temperature around the LED is warmed to some extent, and the temperature rise after the start of LED emission is slight. This is because the decrease in the amount of light is less than that at room temperature. If it is not 40 ° C. or higher, the CPU 201 does not correct the correction value in S406. This is because the temperature around the LED is low and the temperature rise after the LED starts to emit light increases. Therefore, the correction value is left as it is.

  Here, the correction value is corrected by dividing it in three temperature regions according to the ambient temperature of the LED. However, the correction value is not limited to this. For example, the correction value is finely divided into more temperature regions. May be corrected. Moreover, it is an example that 50 degreeC and 40 degreeC were made into a partition, for example, you may change temperature setting according to the individual difference of LED. As an example of correcting the correction value, the correction value is set to 0, the correction value is set to 50%, and the correction value is left as it is. However, the present invention is not limited to this. Accordingly, the correction ratio can be changed.

  In this way, by correcting the correction value for correcting the detection result of the end position of the recording material P according to the temperature around the LED, the detection is performed in consideration of the change in the light amount of the LED according to the temperature. Since the result can be corrected, it is possible to suppress a decrease in detection accuracy of the end position of the recording material due to a change in the light amount of the light emitting unit 111 without waiting until the light amount emitted from the light emitting unit 111 is stabilized. Therefore, it is possible to shorten the time until the end position of the recording material P is detected, and it is also possible to shorten the time for emitting the LED as the light emitting unit 111, and thus it is possible to suppress the shortening of the LED life.

(Fourth embodiment)
In this embodiment, after the image formation is completed and the light emission of the light emitting unit 111 is stopped, the elapsed time from the start of the image formation of the time until the light emission of the light emitting unit 111 is started again is counted and recorded. A method of correcting the detection result after correcting the correction value for correcting the detection result of the end position of the material P according to the elapsed time will be described. In addition, description here is abbreviate | omitted about the structure similar to previous 1st Embodiment thru | or 3rd Embodiment.

  It is known that the amount of light of the LED that is the light emitting unit 111 decreases due to the temperature rise of the LED due to the characteristics of the device. If the elapsed time from the end of the previous image formation to the start of the next image formation is long, the period during which the LED is not emitting light also becomes longer, and the LED temperature and the ambient temperature of the LED have decreased. Thus, the next image formation is performed. On the other hand, if the elapsed time from the end of the previous image formation to the start of the next image formation is short, the period during which the LED is not emitting light will be short, and the LED temperature and the ambient temperature of the LED will be too low. The next image formation is performed in a state where it is not lowered. Therefore, if the elapsed time from the end of the previous image formation to the start of the next image formation is long, the temperature change of the LED at the next image formation becomes large, and the amount of decrease in the amount of light becomes large. On the other hand, if the elapsed time from the end of the previous image formation to the start of the next image formation is short, the temperature change of the LED at the next image formation becomes small, and the amount of decrease in light quantity becomes small. In the present embodiment, a method of correcting the correction value according to the elapsed time from the end of the previous image formation to the start of time image formation will be described.

  FIG. 12 is a flowchart showing a method of correcting the correction value according to the elapsed time from the end of the previous image formation to the start of time image formation. In step S <b> 501, the CPU 201 acquires an elapsed time from the end of the previous image formation to the start of the next image formation. In step S502, the CPU 201 determines whether or not the acquired elapsed time is within one second. If it is within 1 second, the CPU 201 sets the correction value to 60% in S503. This is because, since the elapsed time from the previous image formation to the next image formation is short, the temperature rise after the LED starts emitting light is small at the next image formation, and the decrease in light quantity is small.

  If it is not within 1 second, in S504, the CPU 201 determines whether or not the acquired elapsed time is within 5 seconds. If it is within 5 seconds, the CPU 201 sets the correction value to 30% in S505. If it is within 5 seconds, the temperature of the LED is warmed to some extent compared to the normal time, and the temperature rise after the start of light emission of the LED is slight. If not within 5 seconds, the CPU 201 does not correct the correction value in S506. This is because, since the elapsed time is long, the temperature of the LED is greatly decreased, and the temperature rise after the LED starts to emit light is increased. Therefore, the correction value is left as it is.

  In this example, correction values are corrected by dividing into three pattern areas according to the elapsed time. However, the correction values are not limited to this. For example, correction values are corrected finely by dividing into more areas. Also good. Moreover, it is an example that 1 second and 5 seconds are divided, and for example, the set time may be changed according to individual differences of LEDs. Further, as an example of correcting the correction value, the correction value is set to 60%, the correction value is set to 30%, and the correction value is left as it is. It is possible to change the correction ratio according to the above. The elapsed time may be measured by a timer, or the elapsed time may be predicted based on the value of the temperature decrease of the fixing device.

  In this way, by correcting the correction value for correcting the detection result of the end position of the recording material P according to the elapsed time from the end of the previous image formation to the start of the next image formation, the temperature The detection result can be corrected by taking into account the change in the light quantity of the LED in accordance with the detection, so that the end position of the recording material can be detected by the change in the light quantity of the light emitting section 111 without waiting until the light quantity emitted from the light emitting section 111 is stabilized. It became possible to suppress the decrease in accuracy. Therefore, it is possible to shorten the time until the end position of the recording material P is detected, and it is also possible to shorten the time for emitting the LED as the light emitting unit 111, and thus it is possible to suppress the shortening of the LED life. Further, since the temperature of the LED can be estimated from the elapsed time, the correction value can be corrected without increasing the cost such as using a dedicated temperature sensor.

(Fifth embodiment)
In the present exemplary embodiment, a method for measuring and calibrating data of light quantity reduction characteristics of an LED serving as the light emitting unit 111 of the recording material edge position detection device 100 using an image forming apparatus will be described. In addition, description here is abbreviate | omitted about the structure similar to previous 1st Embodiment thru | or 4th Embodiment.

  If the image forming apparatus continues to be used for a long period of time, the LED light quantity reduction characteristics change due to factors such as deterioration over time and adhesion of toner and paper powder. Thereby, even if it correct | amends using the correction table created by the initial light quantity fall characteristic of LED, there exists a possibility that the detection accuracy of an edge part position may fall. In the present embodiment, the correction table can be updated by measuring the light quantity reduction characteristic of the LED, and a correction value suitable for the LED state can be set.

  FIG. 13 is a flowchart showing a calibration operation for measuring the light quantity reduction characteristic of the LED. In step S601, the CPU 201 starts calibration and starts light emission of the LED. In step S602, the CPU 201 measures the light amount of the LED. Thereafter, in step S603, the CPU 201 determines whether 500 msec has elapsed since the previous light amount was measured. When 500 msec has elapsed, in step S604, the CPU 201 measures the light amount of the LED again. In step S <b> 605, the CPU 201 determines whether 30 seconds or more have elapsed since the start of LED light emission. If 30 seconds have not elapsed, the process returns to S603 again, and the light quantity measurement is continued. When 30 seconds or more have elapsed, the measurement of the light amount of the LED is terminated. Then, based on the measured light quantity, the change of the light quantity of the LED is detected, and the correction table is updated by setting the light quantity reduction characteristic of the LED.

  As a specific example, for example, as an initial value of the LED, according to a light amount reduction characteristic such as 1% decrease after 5 seconds, 2% decrease after 10 seconds, and 3% decrease after 20 seconds from the start of LED light emission. Assume that an initial correction table has been created. For example, when this LED changes to a light quantity reduction characteristic such as 2% reduction after 5 seconds from the start of light emission, 4% reduction after 10 seconds, and 6% reduction after 20 seconds, the light quantity reduction rate is 2 compared to the initial value. Doubled. When the rate of decrease in the amount of light increases, it is necessary to reduce the correction amount at the end, so the correction value is set to 80%. Thereby, it can correct | amend to the correction value according to each light quantity fall characteristic of LED of each image forming apparatus. In addition, the numerical value shown here is an example and is not restricted to this, For example, according to the individual difference of LED, it is also possible to change the correction ratio.

  An image forming apparatus that does not have NVRAM, which is a nonvolatile memory, has a correction table in a readable / writable memory (RAM), and an image forming apparatus that has NVRAM rewrites the correction table in NVRAM. . Further, the timing of performing calibration may be determined every time the image forming apparatus is turned on, or may be determined by the number of prints such that the number of prints is every 1000 sheets. For example, in the case of an image forming apparatus that detects the lifetime of consumable parts such as a process cartridge and a fixing device, the calibration timing may be determined based on the lifetime detection result.

  In this way, by detecting the LED light quantity reduction characteristics for each image forming apparatus and appropriately updating the correction table, the detection result can be corrected in consideration of changes in the LED light quantity due to the deterioration of the LED over time, etc. It is possible to suppress a decrease in detection accuracy of the recording material end position due to a change in the light amount of the light emitting unit 111 without waiting until the light amount emitted from the unit 111 is stabilized. Therefore, it is possible to shorten the time until the end position of the recording material P is detected, and it is also possible to shorten the time for emitting the LED as the light emitting unit 111, and thus it is possible to suppress the shortening of the LED life. Even when the image forming apparatus is used for a long time and the light quantity reduction characteristic of the LED changes from the time of shipment, an appropriate correction value can be determined according to the changed condition. It becomes possible to suppress a decrease in detection accuracy.

DESCRIPTION OF SYMBOLS 100 Recording material edge part position detection apparatus 101 Crankshaft 102 Crank arm 103 Connection part 104 Link member 105 Connection part 110 Sensor unit 111 Light emission part 112 Light reception part 201 CPU
P Recording material

Claims (19)

A reciprocating sensor unit;
In a recording material detection apparatus having a recording material detection sensor mounted on the sensor unit and detecting the presence or absence of a recording material by receiving light emitted from a light emitting unit by a light receiving unit,
While the sensor unit is reciprocating, the recording is detected based on a period in which the recording material detection sensor detects that there is a recording material and a period in which it is detected that there is no recording material. The material detection sensor detects the end position of the recording material on the side orthogonal to the recording material conveyance direction,
The end position of the recording material is detected using a correction value corresponding to the elapsed time from the start of light emission from the light emitting portion of the recording material detection sensor until the end position of the recording material is detected. A recording material detecting apparatus for correcting the detected result. A reciprocating sensor unit;
A recording material detection sensor that is mounted on the sensor unit and detects the presence or absence of a recording material by receiving light emitted from a light emitting unit at a light receiving unit;
In the recording material detection apparatus, which is disposed upstream of the sensor unit in the recording material conveyance direction and has a leading edge detection sensor for detecting a leading edge in the recording material conveyance direction,
While the sensor unit is reciprocating, the recording is detected based on a period in which the recording material detection sensor detects that there is a recording material and a period in which it is detected that there is no recording material. Timing at which light emission from the light emitting unit is started when the material detection sensor detects the end position of the recording material on the side orthogonal to the conveyance direction of the recording material, and the leading edge detection sensor detects the leading edge of the recording material And a correction value corresponding to the length in the conveyance direction of the recording material, and the detection result of detecting the end position of the recording material is corrected. A rotating member that is rotatably supported and rotated by driving from the driving unit to reciprocate the sensor unit;
While the sensor unit is reciprocating due to the rotation of the rotating member, information on the amount of rotation of the rotating member during the period when the recording material detection sensor detects that the recording material is present, or While the sensor unit is reciprocating as the rotating member rotates, the recording material detection sensor detects that there is no recording material, based on information about the amount of rotation of the rotating member. The recording material detection apparatus according to claim 1, wherein the recording material detection sensor detects an end position of the recording material on a side orthogonal to the conveyance direction of the recording material. A connecting link connecting the rotating member and the sensor unit;
The recording material detection apparatus according to claim 3, wherein the rotating member is connected to one end of the connecting link, and a sensor unit is connected to the other end of the connecting link.   5. The recording material detection apparatus according to claim 4, wherein the recording material detection sensor reciprocates on a straight line connecting a connection portion between the sensor unit and the connecting link and a rotation center of the rotating member. .   4. The recording according to claim 3, wherein the driving unit drives the rotating member to rotate in one direction when the end position of the recording material is detected by the recording material detection sensor. Material detection device.   Each time the rotating member makes one revolution, the sensor unit makes one reciprocation, and the sensor unit makes one reciprocation, so that the recording material detection sensor detects that there is a recording material, or the recording material detection. The recording material detection apparatus according to claim 3, wherein a period during which the recording material is detected to be absent is detected by a sensor.   The recording material detection apparatus according to claim 1, further comprising a correction table storing a correction value for correcting a detection result obtained by detecting an end position of the recording material.   9. The correction amount of the detection result obtained by detecting the end position of the recording material is increased as the amount of light of the light emitting unit when the end position of the recording material is detected is increased. The recording material detection device according to claim 1. A temperature sensor for detecting a temperature around the recording material detection sensor;
The correction value for correcting a detection result obtained by detecting an end position of the recording material is corrected according to a temperature detected by the temperature sensor. Recording material detection device.   Measures the elapsed time from stopping light emission from the light emitting unit to starting light emission from the light emitting unit again, and corrects the detection result of detecting the end position of the recording material according to the elapsed time The recording material detection apparatus according to claim 1, wherein a correction value to be corrected is corrected.   After starting light emission from the light emitting unit, a light amount reduction characteristic until the light amount becomes stable is detected, and a correction value for correcting the detection result of detecting the end position of the recording material according to the light amount reduction characteristic is corrected. The recording material detection device according to claim 1, wherein the recording material detection device is a recording material detection device. A first sensor unit that reciprocates;
A second sensor unit which is disposed downstream of the first sensor unit in the recording material conveyance direction and reciprocates;
A recording material detection sensor that is mounted on the first sensor unit and the second sensor unit and detects the presence or absence of a recording material by receiving light emitted from a light emitting unit by a light receiving unit;
In the recording material detection apparatus, comprising a leading edge detection sensor disposed upstream of the second sensor unit in the recording material conveyance direction and detecting a leading edge of the recording material in the conveyance direction,
While the first sensor unit and the second sensor unit are reciprocating, a period during which the recording material detection sensor detects that there is a recording material based on the output value of the light receiving unit, and there is no recording material Based on the detected period, the recording material detection sensor detects the end position of the recording material on the side perpendicular to the recording material conveyance direction,
The detection result detected by the first sensor unit is from the start of light emission from the light emitting part of the recording material detection sensor of the first sensor unit until the end position of the recording material is detected. Correction using a correction value according to the elapsed time of
The detection result detected by the second sensor unit includes the timing at which light emission from the light emitting unit is started and the length in the conveyance direction of the recording material when the leading edge detection sensor detects the leading edge of the recording material. A recording material detection apparatus which performs correction using a corresponding correction value. A first rotating member that is pivotally supported and rotated by driving from a driving unit to reciprocate the first sensor unit;
A second rotating member that is rotatably supported and rotates by driving from the driving unit to reciprocate the second sensor unit;
While the first sensor unit and the second sensor unit reciprocate as the first rotating member and the second rotating member rotate, there is a recording material by the recording material detection sensor. Information regarding the amount of rotation of the rotating member during the period of detection, or while the sensor unit is reciprocating as the rotating member rotates, if there is no recording material by the recording material detection sensor The recording material detection sensor detects an end position of a recording material on a side orthogonal to a recording material conveyance direction based on information on a rotation amount of the rotation member rotated during a detection period. Item 14. The recording material detection device according to Item 13. Image forming means for forming an image on a recording material;
A reciprocating sensor unit;
In an image forming apparatus having a recording material detection sensor mounted on the sensor unit and detecting the presence or absence of a recording material by receiving light emitted from a light emitting unit by a light receiving unit,
While the sensor unit is reciprocating, the recording is detected based on a period in which the recording material detection sensor detects that there is a recording material and a period in which it is detected that there is no recording material. The material detection sensor detects the end position of the recording material on the side orthogonal to the recording material conveyance direction, and the light emission from the light emitting portion of the recording material detection sensor is started, and then the end position of the recording material is detected. The detection value obtained by detecting the end position of the recording material is corrected using a correction value corresponding to the elapsed time until the image is processed, and the image writing timing by the image forming unit is adjusted according to the corrected detection result. An image forming apparatus. Image forming means for forming an image on a recording material;
A sensor unit disposed on the double-sided conveyance path and reciprocating;
A recording material detection sensor that is mounted on the sensor unit and detects the presence or absence of a recording material by receiving light emitted from a light emitting unit at a light receiving unit;
An image forming apparatus having a leading edge detection sensor that is disposed upstream of the sensor unit in the recording material conveyance direction and detects a leading edge of the recording material in the conveyance direction.
While the sensor unit is reciprocating, the recording is detected based on a period in which the recording material detection sensor detects that there is a recording material and a period in which it is detected that there is no recording material. Timing at which light emission from the light emitting unit is started when the material detection sensor detects the end position of the recording material on the side orthogonal to the conveyance direction of the recording material, and the leading edge detection sensor detects the leading edge of the recording material And a correction value corresponding to the length of the recording material in the conveyance direction is used to correct the detection result of detecting the end position of the recording material, and according to the corrected detection result, image writing by the image forming unit is performed. An image forming apparatus characterized by adjusting timing. A rotating member that is rotatably supported and rotated by driving from the driving unit to reciprocate the sensor unit;
While the sensor unit is reciprocating due to the rotation of the rotating member, information on the amount of rotation of the rotating member during the period when the recording material detection sensor detects that the recording material is present, or While the sensor unit is reciprocating as the rotating member rotates, the recording material detection sensor detects that there is no recording material, based on information about the amount of rotation of the rotating member. 17. The image forming apparatus according to claim 15, wherein the recording material detection sensor detects an end position of the recording material on a side orthogonal to the recording material conveyance direction. Image forming means for forming an image on a recording material;
A first sensor unit that reciprocates;
A second sensor unit which is disposed on a double-sided conveyance path downstream of the first sensor unit in the conveyance direction of the recording material and reciprocates;
A recording material detection sensor that is mounted on the first sensor unit and the second sensor unit and detects the presence or absence of a recording material by receiving light emitted from a light emitting unit by a light receiving unit;
An image forming apparatus having a leading edge detection sensor disposed upstream of the second sensor unit in the recording material conveyance direction and detecting a leading edge of the recording material in the conveyance direction;
While the first sensor unit and the second sensor unit are reciprocating, a period during which the recording material detection sensor detects that there is a recording material based on the output value of the light receiving unit, and there is no recording material Based on the detected period, the recording material detection sensor detects the end position of the recording material on the side perpendicular to the recording material conveyance direction,
The detection result detected by the first sensor unit is from the start of light emission from the light emitting part of the recording material detection sensor of the first sensor unit until the end position of the recording material is detected. Correction as the first detection result using a correction value according to the elapsed time of
The detection result detected by the second sensor unit includes the timing at which light emission from the light emitting unit is started and the length in the conveyance direction of the recording material when the leading edge detection sensor detects the leading edge of the recording material. Using the corresponding correction value as a second detection result,
When image formation is performed on the first surface of the recording material, the image writing timing by the image forming means is adjusted according to the first detection result, and the second surface of the recording material, which is the back surface of the first surface. When the image is formed, the image forming apparatus adjusts the image writing timing by the image forming unit according to the second detection result. A first rotating member that is pivotally supported and rotated by driving from a driving unit to reciprocate the first sensor unit;
A second rotating member that is rotatably supported and rotates by driving from the driving unit to reciprocate the second sensor unit;
While the first sensor unit and the second sensor unit reciprocate as the first rotating member and the second rotating member rotate, there is a recording material by the recording material detection sensor. Information regarding the amount of rotation of the rotating member during the period of detection, or while the sensor unit is reciprocating as the rotating member rotates, if there is no recording material by the recording material detection sensor The recording material detection sensor detects an end position of a recording material on a side orthogonal to a recording material conveyance direction based on information on a rotation amount of the rotation member rotated during a detection period. Item 19. The image forming apparatus according to Item 18.

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