JP5287190B2 - Recording medium length measuring apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a recording medium length measuring apparatus and an image forming apparatus.

  2. Description of the Related Art Conventionally, an image forming apparatus that calculates a sheet conveyance speed by an encoder roller or the like disposed on a sheet conveyance path is known (see, for example, Patent Document 1).

In this image forming apparatus, the encoder roller and the pressing roller are arranged so that the paper is sandwiched between both rollers, the encoder roller rotates as the paper passes, and the amount of rotation of the encoder roller is determined by the pulse It is detected as the number of pulses by the detector. Then, the control unit of the image forming apparatus calculates the sheet conveyance speed from the number of pulses detected by the pulse detector, the pulse interval, and the like.
JP 2005-225073 PR

  An object of the present invention is to provide a recording medium length capable of accurately measuring the length of the recording medium as compared with the case where the peripheral surface portion does not have the first and second rotating portions formed of different materials. Another object of the present invention is to provide a height measuring device and an image forming apparatus.

  In order to achieve the above object, an aspect of the present invention provides the following recording medium length measuring device and image forming apparatus.

[1] A first rotating portion that comes into contact with a recording medium after fixing conveyed along a conveying path and rotates as the recording medium is conveyed; and A second peripheral surface portion formed of a material having a smaller thermal expansion coefficient than the material of the first peripheral surface portion is in contact with the first peripheral surface portion of the first rotating portion, and Recording medium length comprising: a second rotating part that rotates with rotation; and a length detection part that detects the length of the recording medium in the transport direction based on the amount of rotation of the second rotating part. measuring device.

[ 2 ] The first peripheral surface portion includes a first layer and a second layer that covers the first layer, and the second layer has higher hardness than the first layer. The recording medium length measuring apparatus according to [1].

[ 3 ] Furthermore, a third circumferential surface portion is provided at a position facing the first rotating portion via the conveyance path, and a third peripheral surface portion comes into contact with the recording medium and rotates with conveyance of the recording medium. The recording medium length measuring apparatus according to [1], further including a rotating unit.

[ 4 ] The recording medium length measurement device according to [ 3 ], wherein the second rotating unit is arranged at a position off a line connecting the rotation centers of the first and third rotating units.

[ 5 ] The length detection unit includes a signal generation unit that generates a rotation amount detection signal corresponding to the rotation amount of the second rotation unit, and an end detection unit that detects the start and end of the recording medium in the conveyance direction. [1] comprising: a sensor; and a calculation unit that calculates a length in the conveyance direction of the recording medium based on a rotation amount detection signal from the signal generation unit and an end detection signal from the end detection sensor. ] The recording-medium length measuring apparatus of description.

[ 6 ] The length detection unit includes a signal generation unit that generates a rotation amount detection signal corresponding to the rotation amount of the second rotation unit, a temperature sensor that detects the temperature of the second rotation unit, and The rotation amount is acquired based on the rotation amount detection signal from the signal generation unit, and the acquired rotation amount is corrected based on the temperature detection signal from the temperature sensor to calculate the length of the recording medium in the transport direction. The recording medium length measurement apparatus according to [1], further including a calculation unit.

[ 7 ] The length detection unit includes a signal generation unit that generates a rotation amount detection signal corresponding to the rotation amount of the second rotation unit, and an eccentricity correction that corrects a rotation center shift of the second rotation unit. A storage unit for storing information and a rotation amount are acquired based on a rotation amount detection signal from the signal generation unit, and the acquired rotation amount is corrected based on the eccentricity correction information stored in the storage unit. The recording medium length measurement apparatus according to [1], further including a calculation unit that calculates a length of the recording medium in a conveyance direction.

[ 8 ] An image forming unit that forms an image on the recording medium after fixing conveyed along the conveyance path, and a first peripheral surface portion that contacts the recording medium, and the first rotating surface rotates along with the conveyance of the recording medium. The first peripheral portion of the first rotating portion is formed of a material having a smaller thermal expansion coefficient than the material of the first rotating portion and the first peripheral surface portion of the first rotating portion. The length of the recording medium in the conveyance direction is detected based on the second rotating unit that contacts the surface unit and rotates in accordance with the rotation of the first rotating unit, and the rotation amount of the second rotating unit. Based on the length in the conveyance direction of the recording medium measured by the recording medium length measuring unit, a reversing unit that reverses the front and back of the recording medium, and a recording medium length measuring unit. , Formed by the image forming unit on the recording medium whose front and back are reversed by the reversing unit Image forming apparatus and a control unit for controlling the formation conditions of the image to be.

According to the first aspect of the present invention, the measurement accuracy of the recording medium can be measured even when there is a temperature change as compared with the case where the thermal expansion coefficient of the material of the second peripheral surface portion is the same as or larger than that of the first peripheral surface portion. The influence on can be reduced.

According to the invention of claim 2, part a hardness of the second layer as compared with the case the same or lower as that of the first layer, the first peripheral surface is in contact with the recording medium and the second rotating part Therefore, it is possible to accurately convey the conveyance amount of the recording medium as the rotation amount of the second rotation unit.

According to the invention according to claim 3, in comparison with the case not having a third rotating part, the first rotary part with the conveyance of the recording medium is to simplify the structure to rotate.

According to the fourth aspect of the present invention, the second height of the recording medium length measuring device is lower than that when the second rotating portion is arranged on a line connecting the rotation centers of the first and third rotating portions. Can be made possible.

According to the invention of claim 5 , the length of the recording medium is not calculated based on the rotation amount detection signal from the signal generation unit and the end detection signal from the end detection sensor. The measurement accuracy when measuring the length can be improved.

According to the sixth aspect of the invention, it is possible to reduce the influence on the measurement accuracy of the recording medium even when there is a temperature change, as compared with the case where no correction is performed based on the temperature detection signal from the temperature sensor. it can.

According to the seventh aspect of the present invention, the length of the recording medium can be accurately measured while reducing the manufacturing cost as compared with the case where no correction is performed based on the eccentricity correction information.

According to the eighth aspect of the present invention, the measurement accuracy of the recording medium can be measured even when there is a temperature change as compared with the case where the thermal expansion coefficient of the material of the second peripheral surface portion is the same as or larger than that of the first peripheral surface portion. Can be reduced, and image misregistration between the front and back of the recording medium and between a plurality of recording media can be reduced.

  In the recording medium length measurement device according to the embodiment of the present invention, the first peripheral surface portion is in contact with the recording medium conveyed along the conveying path, and the first rotation rotates as the recording medium is conveyed. And a second peripheral surface portion formed of a material different from a material of the first peripheral surface portion of the first rotating portion is in contact with the first peripheral surface portion of the first rotating portion, A second rotation unit that rotates in accordance with the rotation of the first rotation unit, and a length detection unit that detects the length of the recording medium in the conveyance direction based on the rotation amount of the second rotation unit.

  The recording medium includes paper, film, an OHP sheet, a postcard, and the like, and is not limited to these as long as it can record an image.

  The first peripheral surface portion of the first rotating portion may be an outer ring portion having a predetermined thickness from the outer peripheral surface, and a bearing portion such as a bearing is provided at the center of the first rotating portion. If it is, the portion from the outer peripheral surface to the bearing portion may be used, or the portion including the bearing portion may be used.

  In the above configuration, the conveyance amount of the recording medium is transmitted to the second rotation unit by the first rotation unit, and the second rotation unit rotates, so that the length in the conveyance direction of the recording medium is calculated from the rotation amount. Measured. At that time, a material having a relatively large friction coefficient with the recording medium is used as the material of the first peripheral surface portion of the first rotating portion, and the thermal expansion coefficient is used as the material of the second peripheral surface portion of the second rotating portion. It is preferable to use a material having a relatively small value. As a result, even if the diameter of the first rotating part changes due to thermal expansion, the amount of movement of the peripheral surface of the first peripheral part, that is, the amount of rotation of the second rotating part is the heat of the first rotating part. Since it is not affected by the change in expansion, the length of the recording medium conveyance method can be accurately measured.

[First Embodiment]
FIG. 1 is a schematic diagram illustrating an example of a schematic configuration of an image forming apparatus according to a first embodiment of the present invention. The image forming apparatus 1 includes a sheet length measuring device (recording medium length measuring unit) 2 that measures a length of a sheet 10 as a recording medium in a conveying direction (hereinafter referred to as a sheet length), and a sheet length measuring device 2. The main control unit (control unit) 3 that receives the sheet length measured by the above and controls each unit of the image forming apparatus 1, and black (K), yellow (Y), magenta (M), and cyan (C). The first to fourth image forming units (image forming units) 4K, 4Y, 4M, and 4C that respectively form the toner images, and the colors (K, Y, and 4C) formed by the image forming units 4K, 4Y, 4M, and 4C, respectively. And an intermediate transfer belt 5 that holds toner images of M, C).

  The image forming apparatus 1 also includes a paper tray 11 that stores a plurality of paper sheets 10, a plurality of transport rollers 12 that transport the paper 10 carried out of the paper tray 11 along a predetermined transport path 10a, and a transport path 10a. A paper sensor 13 for detecting the presence or absence of the upper paper 10, a transfer roll 14 for transferring the toner image held on the intermediate transfer belt 5 to the paper 10, and a fixing device 15 for fixing the toner image transferred to the paper 10. A cooling unit 16 that cools the paper 10 and a paper reversing unit (reversing unit) 17 that reverses the front and back of the paper 10 are provided.

(Image forming unit)
Each of the image forming units 4K, 4Y, 4M, and 4C includes a photosensitive drum 40 having a photosensitive layer on the surface, a charger 41 that applies a predetermined charge to the photosensitive drum 40 before exposure, and image data of each color. The ROS (Raster Output Scanner) 42 as an exposure device that exposes the photosensitive drum 40 with a laser beam modulated on the basis thereof to form an electrostatic latent image, and the electrostatic latent image formed on the photosensitive drum 40 correspond to each other. A developing unit 43 that develops the toner of each color, and a static eliminator 44 that neutralizes the photosensitive drum 40 after the toner image is transferred to the intermediate transfer belt 5.

(Intermediate transfer belt)
The intermediate transfer belt 5 includes support rollers 50 </ b> A to 50 </ b> C that rotatably drive the intermediate transfer belt in the direction of arrow C and that rotatably support the intermediate transfer belt 5 with a predetermined tension. The support roller 50 </ b> A is disposed at a position facing the transfer roll 14 with the intermediate transfer belt 5 interposed therebetween.

(Main control unit)
The main control unit 3 is realized by a CPU or the like, for example, and controls each part of the image forming apparatus 1. The main control unit 3 is connected to an operation unit realized by a push button or a touch panel, a display unit that displays an operation screen or a result screen, and an external communication unit that communicates with an external device such as a computer. Has been.

  The main control unit 3 is configured to convey the sheet 10 by a sheet conveyance system including the conveyance roller 12 and the sheet sensor 13 in accordance with an operation signal from the operation unit and image data received from the external communication unit via the communication unit. To control. Further, the main control unit 3 synchronizes with the conveyance state of the paper 10, and based on the paper length measured by the paper reversing unit 17, the image forming unit for the paper 10 whose front and back are reversed by the paper reversing unit 17. Controls the formation conditions of toner images formed by 4K, 4Y, 4M, and 4C.

  Examples of the toner image forming conditions include a writing position indicating a transfer position from the starting end of the paper 10 when the toner image is transferred to the paper 10, an enlargement / reduction amount indicating the enlargement ratio and reduction ratio of the toner image, and the like.

(Paper length measuring device)
The sheet length measuring device 2 is disposed at the subsequent stage of the cooling unit 16. The sheet length measuring device 2 includes a sheet length detection unit (length detection unit) 20 that detects the sheet length of the sheet 10 conveyed along the conveyance path 10a. Details of the sheet length detection unit 20 will be described later.

  FIG. 2 is a schematic diagram illustrating an example of a schematic configuration of the sheet length measuring apparatus. FIG. 2A is a cross-sectional view taken along the line AA in FIG. 1, and the sheet 10 is conveyed in a direction perpendicular to the sheet (from the front to the back). FIG. 2B is a cross-sectional view taken along line BB in FIG. 2A, and the paper 10 is conveyed from the left to the right of the paper surface.

  The sheet length measuring device 2 includes a first support member 27A and a second support member 27B that are disposed at positions facing each other via the transport path 10a.

  The first support member 27A includes two shafts 200 and 201 disposed in parallel with the width direction of the paper 10, an intermediate roller (first rotation unit) 21 rotatably attached to the shaft 200, and a shaft. An encoder roller (second rotating unit) 22 fixed to 201, an encoder unit (signal generating unit) 23 connected to the encoder roller 22 via a shaft 201, and a start end 10b and a terminal end 10c of the paper 10 are detected. A paper edge sensor (edge detection sensor) 24 and a temperature sensor 25 arranged close to the encoder roller 22 are provided.

  The second support member 27 </ b> B is provided with a shaft 202 disposed in parallel with the width direction of the paper 10 and a pressing roller (third rotating portion) 26 that is rotatably attached to the shaft 202.

  The paper edge sensor 24 is, for example, a reflection-type optical sensor or the like, which irradiates a position where the paper 10 is conveyed with laser light and detects the intensity of the reflected light reflected by the surface 10 d of the paper 10. The paper edge sensor 24 sends an edge detection signal (edge detection signal) corresponding to the intensity of the reflected light to the control unit of the paper length detection unit 20, and the start edge 10b of the paper 10 according to the change of the edge detection signal. And the end 10c is detected.

  The temperature sensor 25 is, for example, a thermistor and detects the environmental temperature of the encoder roller 22. The temperature sensor 25 sends a temperature detection signal based on the detected environmental temperature to the control unit included in the paper length detection unit 20.

  The intermediate roller 21 has a first peripheral surface portion 21 a that contacts the surface 10 d of the paper 10 and rotates as the paper 10 is conveyed.

  The encoder roller 22 has a second peripheral surface portion 22 a that contacts the first peripheral surface portion 21 a of the intermediate roller 21, and rotates as the intermediate roller 21 rotates. The second peripheral surface portion 22a is formed of a material different from the material of the first peripheral surface portion 21a. In the present embodiment, the first peripheral surface portion 21a is formed of rubber, which is a material having a high coefficient of friction with the paper 10, and the second peripheral surface portion 22a has a smaller thermal expansion coefficient than rubber. It is made of a material metal (for example, aluminum).

  The pressing roller 26 is provided at a position facing the intermediate roller 21 through the transport path 10 a, has a third peripheral surface portion 26 a that contacts the back surface 10 e of the paper 10, and rotates as the paper 10 is transported.

  FIG. 3A is a cross-sectional view showing an example of the internal structure of the intermediate roller. FIG. 3B is a schematic diagram illustrating an example of a deformed state of the intermediate roller.

  The intermediate roller 21 has a two-layer structure including a first rubber layer 210 and a second rubber layer 211 that covers the first rubber layer 210. The hardness of the second rubber layer 211 is higher than the hardness of the first rubber layer 210.

  For example, when the diameter of the intermediate roller 21 is 20 mm, the first rubber layer 210 has a thickness of 19.95 mm and a hardness A30, and the second rubber layer 210 has a thickness of 0.05 mm and a hardness A80. The hardness is a value measured according to JIS K 6253 (ISO 7619) type A. The intermediate roller 21 is not limited to two layers, and three or more layers may be laminated. In the present embodiment, the material of the intermediate roller 21 is rubber, but plastic may be used, and the inner and outer layers may be formed of different materials.

  The intermediate roller 21 is applied with a constant pressure F <b> 1 from the encoder roller 22. As a structure for applying the pressure F1 to the intermediate roller 21, for example, the pressing roller 26 is fixed, the intermediate roller 21 and the encoder roller 22 are movable in the vertical direction, and the encoder roller 22 is moved downward using an elastic member such as a spring. The encoder roller 22 may be fixed at a position where the application state is maintained.

  When such a pressure is applied to the intermediate roller 21, the second rubber layer 211 is harder than the inner first rubber layer 210, so that the second rubber layer 211 is locally deformed on the surface. Instead, the entire intermediate roller 21 is deformed and deformed into an elliptical shape as illustrated in FIG.

  A float that cancels the self-weight of the intermediate roller 21 by providing an elastic member such as a spring in which an upward elastic force acts inside the first support member 27A and supporting the shaft 200 by the elastic member. A mechanism may be provided. As a result, the reaction force received by the intermediate roller 21 from the encoder roller 22 and the reaction force received by the intermediate roller 21 from the pressing roller 26 become substantially equal, so that the intermediate roller 21 is deformed into a vertically symmetrical elliptical shape.

(Encoder part)
The encoder unit 23 generates an encoder signal and a Z-phase signal as a rotation amount detection signal corresponding to the rotation amount of the encoder roller 22. The configuration of the encoder roller 22 will be described below with reference to FIG.

  FIG. 4 is a schematic diagram illustrating an example of a schematic configuration of the encoder unit. The encoder unit 23 is connected to the encoder roller 22 via a shaft 201. For example, two bearings 230A for fixing the shaft 201 to the housing 23a in a rotatable state inside a cylindrical housing 23a. , 230B and a circular slit disk 231 fixed to the shaft 201 through the center.

  The slit disk 231 is provided with a plurality of first slits 231a formed at equal intervals in the circumferential direction and one second slit 231b formed inside the slit 231a in the radial direction.

  In addition, the encoder unit 23 collects irradiation light from the first and second light emitting elements 232A and 232B and the first and second light emitting elements 232A and 232B, respectively, in the housing 23a. And the second lenses 233A and 233B, the fixed slit 234 formed on the optical axis condensed by the first lens 233A, and the first lens 233A and the first lens 233A. The first light receiving element 235A that receives the light that has passed through the slit 231a and the fixed slit 234, and the second lens 233B, and the first light that receives the light that has passed through the second slit 231b of the slit disk 231. Two light receiving elements 235B, and first and second amplifiers 236A and 236 for amplifying output signals from the first and second light receiving elements 235A and 235B, respectively. Provided with a door.

  The first and second light emitting elements 232A and 232B are configured by, for example, light emitting diodes (LEDs), and the first and second light receiving elements 235A and 235B are configured by, for example, photodiodes (PD). Yes.

  The first light receiving element 235 </ b> A intermittently divides the light that has passed through the first slit 231 a and the fixed slit 234 by the rotation of the encoder roller 22 so that the irradiation light from the first light emitting element 232 </ b> A is divided into pieces in time. And a pulse waveform corresponding to the timing of the received light is output as an output signal. The first amplifier 236A sends the encoder signal Sp obtained by amplifying the output signal to the control unit included in the paper length detection unit 20.

  The second light receiving element 235B receives the light that has passed through the second slit 231b once per rotation of the encoder roller 22, and outputs a pulse waveform corresponding to the timing of the received light as an output signal. The second amplifier 236B sends the Z-phase signal Sz obtained by amplifying the output signal to the control unit included in the paper length detection unit 20.

(Paper length detector)
FIG. 5 is a block diagram illustrating an example of a schematic configuration of the paper length detection unit. In addition to the encoder unit 23, the paper edge sensor 24, and the temperature sensor 25, the paper length detection unit 20 controls each unit, for example, a control unit 28 realized by a CPU or the like, and stores a program, data, and the like. For example, the storage unit (storage unit) 29 is realized by a ROM, a RAM, a hard disk, or the like.

  The control unit 28 is electrically connected to the main control unit 3, the encoder unit 23, the paper edge sensor 24, the temperature sensor 25, and the storage unit 29.

  The storage unit 29 stores pulse distance conversion information 290, thermal expansion coefficient information 291 and the like.

  The pulse distance conversion information 290 is information for converting the rotation amount of the encoder roller 22 into a distance. The pulse distance conversion information 290 stores, for example, an encoder pulse distance per pulse of the encoder signal Sp detected by the encoder unit 23 and a Z phase pulse distance per pulse of the Z phase signal Sz.

  The thermal expansion coefficient information 291 is information in which a thermal expansion coefficient indicating the ratio of the amount by which the size of the encoder roller 22 changes due to a change in temperature is stored. For example, the thermal expansion coefficient information 291 may be a linear expansion coefficient or a volume expansion coefficient. The thermal expansion coefficient information 291 may be a table in which dimensions such as the diameter of the encoder roller 22 at each temperature are measured in advance by a measuring device or the like that measures the component dimensions, and the measured dimensions of each temperature are stored.

  The control unit 28 communicates between the paper length calculation function (calculation unit) 280A for calculating the paper length and the main control unit 3, and supplies the paper length calculated by the paper length calculation function 280A to the main control unit 3. And a communication function 281 for transmission.

  The sheet length calculation function 280A receives the encoder signal Sp from the first amplifier 236A of the encoder unit 23 and the Z-phase signal Sz from the second amplifier 236B. Further, the sheet length calculation function 280A receives an edge detection signal from the sheet edge sensor 24 and a temperature detection signal from the temperature sensor 25.

  The paper length calculation function 280A calculates the paper length based on the input encoder signal Sp, Z-phase signal Sz, edge detection signal, and temperature detection signal. Specifically, the paper length calculation function 280A calculates the paper length based on the encoder signal Sp, the Z-phase signal Sz, and the edge detection signal, and the calculated paper length is based on the temperature detection signal from the temperature sensor 25. By correcting, the final sheet length is calculated. At that time, the paper length calculation function 280A converts the rotation amounts of the encoder signal Sp and the Z-phase signal Sz into the distance by the pulse distance conversion information 290, and calculates the thermal expansion coefficient corresponding to the temperature detection signal from the thermal expansion coefficient information 291. The thermal expansion coefficient is obtained and used for correcting the paper length. Details of the sheet length measurement operation will be described later with reference to FIG.

(Operation of image forming apparatus)
Next, an example of the overall operation when the image forming apparatus 1 forms images on both sides of the paper 10 will be described with reference to the flowchart of FIG.

  FIG. 6 is a flowchart illustrating an example of the overall operation when the image forming apparatus forms images on both sides of a sheet. First, when the main control unit 3 of the image forming apparatus 1 receives a print request, for example, by receiving image data from an external apparatus or the like (S1), the paper transport system such as the transport roller 12 and the image forming units 4K, 4K, 4Y, 4M, and 4C are activated to perform a warm-up operation (S2).

  After the warm-up operation, the main control unit 3 rotationally drives the transport roller 12 to carry out the paper 10 from the paper tray 11, and transports the paper 10 along the transport path 10a. The main control unit 3 outputs image signals based on image data to be printed on the front side of the paper 10 to the image forming units 4K, 4Y, 4M, and 4C in synchronization with the detection state of the paper 10 by the paper sensor 13 ( S11).

  Next, each of the image forming units 4K, 4Y, 4M, and 4C forms a toner image on the intermediate transfer belt 5 based on the image signal (S12). Specifically, the photosensitive drum 40 of each of the image forming units 4K, 4Y, 4M, and 4C is rotated, and after the rotated photosensitive drum 40 is charged by the charger 41, it corresponds to the image signal of each color from the ROS 42. An electrostatic latent image is formed on the surface of the photosensitive drum 40 by exposure with a laser beam. The electrostatic latent image on each photoconductor drum 40 is developed into a toner image by the corresponding developing device 43 for each color. The toner images are sequentially transferred onto the intermediate transfer belt 5 that is rotationally driven by the support rollers 50A to 50C.

  Next, the sheet 10 carried out from the sheet tray 11 is conveyed by the conveying roller 12 and reaches the position where the transfer roll 14 is disposed, and the toner image on the intermediate transfer belt 5 is transferred to the sheet by the transfer roll 14. 10 is transferred (S13).

  Next, the fixing device 15 fixes the toner image on the paper 10 by applying pressure to the paper 10 on which the toner image has been transferred, for example, while heating (S14). Then, the cooling unit 16 causes the paper 10 heated by the fixing device 15 to pass between, for example, two metal rollers disposed so as to sandwich the paper 10 with high thermal conductivity so as to pass through. Heat is absorbed from the paper 10, and the paper 10 is cooled (S15).

  Next, when the cooled paper 10 is conveyed to the paper length measuring device 2, the intermediate roller 21 and the encoder roller 22 are sequentially rotated as the paper 10 is conveyed. The rotation of the encoder roller 22 is detected by the encoder unit 23 as an encoder signal Sp and a Z-phase signal Sz. Further, the edge detection signal from the paper edge sensor 24 and the temperature detection signal from the temperature sensor 25 are input to the paper length calculation function 280A, and the paper length calculation function 280A receives the encoder signal Sp, Z-phase signal Sz, and edge detection signal. The sheet length is calculated based on the temperature detection signal (S21). Details of step S21 will be described later with reference to the flowchart of FIG.

  Then, the sheet length measuring device 2 transmits the calculated sheet length to the main control unit 3 via the communication function 281. When the main control unit 3 receives the paper length, the main control unit 3 calculates the writing position and the enlargement / reduction amount as the forming conditions for forming the toner image on the back side of the paper 10 based on the paper length (S22).

  Further, when the paper 10 that has passed through the paper length measuring device 2 is conveyed to the paper reversing unit 17 and carried into the paper reversing unit 17, the paper reversing unit 17 reverses the front surface 10 d and the back surface 10 e of the paper 10. And carry it out (S23). Note that, as a result of the paper 10 being reversed by the paper reversing unit 17, the front surface 10d and the back surface 10e are interchanged, and the start end 10b and the end end 10c are also interchanged.

  Next, when the sheet 10 is unloaded from the sheet reversing unit 17 and conveyed to the merging unit that merges with the sheet 10 unloaded from the sheet tray 11, the main control unit 3 synchronizes with the detection state of the sheet sensor 13. Then, an image signal based on the image data to be printed on the back side (the side opposite to the front side on which the toner image has already been formed) is output to the image forming units 4K, 4Y, 4M, 4C (S31).

  Then, each of the image forming units 4K, 4Y, 4M, and 4C forms a toner image on the intermediate transfer belt 5 according to the writing position and the enlargement / reduction amount calculated in step S22 (S32). When the paper 10 reaches the position of the transfer roll 14, the toner image on the intermediate transfer belt 5 is transferred to the paper 10 by the transfer roll 14 (S33). Next, the toner image is fixed on the paper 10 by the fixing device 15 (S34), and cooled by the cooling unit 16 (S35). Then, the paper 10 with the toner images fixed on the front surface 10d and the back surface 10e is discharged to the outside (S41), and a series of image forming operations is completed.

(Paper length measurement operation)
Next, an example of the operation when the sheet length measuring device 2 measures the sheet length of the sheet 10 will be described with reference to FIG. 7 and the flowchart of FIG.

  FIG. 7 is a waveform diagram showing an example of an edge detection signal, an encoder signal, and a Z-phase signal when the paper passes through the paper length measuring device. FIG. 8 is a flowchart showing details of step S21 in FIG.

  First, the paper length calculation function 280A monitors whether or not the edge detection signal is equal to or greater than a predetermined threshold due to the passage of the start edge 10b of the paper 10 in the input waveform of the edge detection signal from the paper edge sensor 24 (S101). ). Then, when the sheet 10 is transported and the start edge 10b passes the detection position of the sheet edge sensor 24 and the edge detection signal becomes equal to or greater than a predetermined threshold, the sheet length calculation function 280A detects the rising edge of the edge detection signal ( S101: Yes).

Then, the sheet length calculation function 280A from start detection time _{t e1} which detects the rising of the edge detection signal, starts counting the encoder pulses (S101),

  Next, the paper length calculation function 280A monitors whether or not the first encoder pulse is input from the first amplifier 236A of the encoder unit 23 (S111). Then, the sheet 10 is conveyed, the intermediate roller 21 rotates, and the encoder roller 22 rotates with the rotation. Further, in conjunction with the rotation of the encoder roller 22, the slit disk 231 of the encoder unit 23 connected to the shaft 201 rotates. When irradiation light from the first light emitting element 232A passes through the first slit 231a and the fixed slit 234, the irradiation light is received by the first light receiving element 235A and amplified by the first amplifier 236A. Thus, the first encoder pulse is input to the paper length calculation function 280A.

The sheet length calculation function 280A detects a first encoder pulses (S 111: Yes), stores the time Ta from the start end detection time _{t e1} to a first encoder detection time _{t p1} that detected the first encoder pulse The information is temporarily stored in the unit 29 (S112).

  Next, the paper length calculation function 280A monitors whether or not a Z-phase pulse is input from the second amplifier 236B (S121). Then, the sheet 10 is further conveyed, and the encoder roller 22 rotates via the intermediate roller 21, whereby the first Z-phase pulse is input to the sheet length calculation function 280A.

Next, when the paper length calculation function 280A detects the first Z-phase pulse (S121: Yes), the paper length calculation function 280A stops counting the encoder pulses and starts from the first encoder detection time _tp1 to the first Z-phase detection time t. The first count number Cp1 of encoder pulses up to _z1 is acquired and stored in the storage unit 29 (S122). The sheet length calculation function 280A, by dividing the time from the first encoder detection time _{t p1} to the first Z-phase detection time _{t z1} in the first count number Cp1, calculating a first reference time T1 And stored in the storage unit 29.

Then, the paper length calculation function 280A starts counting the Z-phase pulse from the first Z-phase detection time _tz1 (S123).

  Next, the paper length calculation function 280A monitors whether or not the edge detection signal is equal to or lower than a predetermined threshold due to the passage of the end 10c of the paper 10 in the input waveform of the edge detection signal from the paper edge sensor 24 ( S131). When the sheet 10 is conveyed and the end 10c passes the detection position of the sheet edge sensor 24, and the edge detection signal becomes equal to or less than a predetermined threshold, the sheet length calculation function 280A detects the falling edge of the edge detection signal. (S131: Yes).

Then, the sheet length calculation function 280A obtains the second encoder detection time t _p2 detecting the encoder pulse at the end a prior end detection time t _e2 which detects the falling of the edge detection signal. Then, the sheet length calculation function 280A acquires the time Tb from the second encoder detection time _tp2 to the end detection time _te2 and stores it in the storage unit 29 (S132).

Next, the paper length calculation function 280A stops the count of the Z-phase pulse, acquires the count number Cz of the Z-phase pulse, and stores it in the storage unit 29 (S133). The sheet length calculation function 280A is the encoder pulse from the second Z-phase detection time t _z2 detecting a Z-phase pulse A before the end detection time t _e2 at the end to a second encoder detection time t _p2 The second count number Cp2 is acquired and stored in the storage unit 29 (S134). The sheet length calculation function 280A, by dividing the time from the second Z-phase detection time _{t z2} to a second encoder detection time _{t p2} in the second count number Cp2, calculates a second reference time T2 And stored in the storage unit 29.

  Next, the sheet length calculation function 280A refers to the thermal expansion coefficient information 291 stored in the storage unit 29 on the basis of the temperature detection signal input from the temperature sensor 25, so that the current temperature environment of the encoder roller 22 is reached. The lower thermal expansion coefficient Kt is acquired (S141).

  Next, the paper length calculation function 280A refers to the pulse distance conversion information 290 and acquires the encoder pulse distance Kp per one pulse of the encoder pulse and the Z phase pulse distance Kz per one pulse of the Z phase pulse. (S142).

Then, the paper length calculation function 280A calculates the paper length Lp of the passed paper 10 by the following formula (1) based on the information stored or acquired as described above (S151).
Lp = Kt (L1 + L2 + L3 + L4 + L5) (1)
However, L1 = Kp (Ta / T1)
L2 = Kp × Cp1
L3 = Kz × Cz
L4 = Kp × Cp2
L5 = Kp (Tb / T2)

  When the above-described image formation is performed on a plurality of sheets 10, a plurality of sheets 10 are printed, and the plurality of sheets 10 are bundled to form one booklet. At this time, even if the paper length varies among the plurality of papers 10, the forming conditions such as the writing position are corrected based on the paper length measured by the paper length measuring device 2, so that the left and right spread or the top and bottom spread The amount of positional deviation between the sheets is reduced, and a high-quality booklet is created as compared with the case where correction based on the sheet length is not performed.

[Second Embodiment]
The paper length measuring device 2 according to the second embodiment measures the paper length by correcting the eccentricity when the encoder roller 22 rotates eccentrically. Note that the configuration and operation of the image forming apparatus 1 provided with the sheet length measuring device 2 are the same as those in the first embodiment, and thus the description thereof is omitted.

  FIG. 9 is a block diagram illustrating an example of a schematic configuration of the sheet length measuring apparatus. The paper length detection unit 20 of the paper length measurement device 2 includes an encoder unit 23, a paper edge sensor 24, a temperature sensor 25, a control unit 28, and a storage unit 29, as in the first embodiment. .

  The eccentricity correction information 292 stored in the storage unit 29 is information for correcting the eccentricity when the encoder roller 22 rotates with the rotation center shifted. The eccentricity correction information 292 is, for example, a table in which the distance from the reference position is stored in each encoder pulse number detected during one rotation from the reference position of the encoder roller 22. Hereinafter, the usefulness of the eccentricity correction information 292 will be described with reference to FIG.

  Fig.10 (a) is a figure which shows the example of arrangement | positioning of an encoder roller. The encoder roller 22 has an actual central shaft 22c formed at a position shifted from the designed central shaft 22b.

  FIG. 10B is a graph showing the relationship between the number of encoder pulse counts and the distance when the encoder roller rotates. Graph Ga shows the case where the encoder roller 22 rotates about the design center axis 22b. The graph Gb shows a case where the encoder roller 22 rotates on the actual center axis 22c.

  In the graph Ga, a proportional relationship is established between the count number and the distance. On the other hand, in the graph Gb, a proportional relationship is not established between the count number and the distance, and for example, an S-shaped curve is obtained. For this reason, when the count number Cp is converted into a distance, an error occurs between the distance La calculated by multiplying the count number Cp by the encoder pulse distance Kp per encoder pulse unit and the actual distance Lb. Therefore, the eccentricity correction information 292 stores, as information corresponding to the graph Gb, for example, a measurement value obtained by measuring the relationship between the count number and the distance in a state where the encoder roller 22 is assembled. The eccentricity correction information 292 may be based on measurement values obtained by measuring the diameter of the encoder roller 22, the position of the central shaft 22c, and the like with a measuring device or the like.

The paper length calculation function 280B calculates the paper length Lp by correcting the rotation amount based on the encoder signal Sp and the Z-phase signal Sz based on the eccentricity correction information 292. Specifically, the sheet length calculation function 280B acquires distances Lb1 and Lb2 corresponding to the first count number Cp1 and the second count number Cp2 by referring to the eccentricity correction information 292, and The paper length Lp is calculated by the following equation (2).
Lp = Kt (L1 + L2 + L3 + L4 + L5) (2)
However, L1 = Kp (Ta / T1)
L2 = Lb1
L3 = Kz × Cz
L4 = Lb2
L5 = Kp (Tb / T2)

  In the above configuration, since the paper length is measured in a state where the eccentricity of the encoder roller 22 is corrected by the paper length measuring device 2, the paper length is not affected by the processing accuracy or assembly accuracy of the encoder roller 22. Is measured accurately.

[Third Embodiment]
In the sheet length measuring device 2 according to the first embodiment, the encoder roller 22 is disposed above the intermediate roller 21. On the other hand, the sheet length measuring device 2 according to the present embodiment has a modified arrangement of the encoder roller 22. Note that the configuration and operation of the image forming apparatus 1 provided with the sheet length measuring device 2 are the same as those in the first embodiment, and thus the description thereof is omitted.

  FIG. 11 is a schematic diagram illustrating an example of a schematic configuration of the sheet length measuring apparatus. FIG. 11 is a diagram corresponding to FIG.

  The encoder roller 22 is arranged side by side in front of the intermediate roller 21 in the conveyance direction of the paper 10. That is, assuming that the line H1 connecting the rotation center of the pressing roller 26 and the rotation center of the intermediate roller 21 is a line H2 connecting the rotation center of the encoder roller 22 and the rotation center of the intermediate roller 21, the encoder roller 22 is from the line H1. In the example of FIG. 11, the crossing angle θ formed by the line H1 and the line H2 is 90 degrees. In the first embodiment, the intersection angle θ is 180 degrees, but the intersection angle θ may be changed between 90 degrees and 180 degrees. If the encoder roller 22 and the paper 10 are not in contact with each other, the angle may be 90 degrees or less.

  The intermediate roller 21 is applied with a pressure F in a diagonally lower right direction. The applied pressure F is divided into a pressure applied to the encoder roller 22 side and a pressure applied to the pressure roller 26 side, and the intermediate roller 21 receives a reaction force from the encoder roller 22 and the pressure roller 26.

  In the above configuration, the encoder roller 22 is disposed closer to the conveyance path 10a than in the first embodiment. Therefore, when the sheet length measuring device 2 is attached to the image forming apparatus 1, the encoder roller 22 is removed from the conveyance path 10a. Mounting dimensions are reduced.

[Other embodiments]
The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, in each of the above embodiments, the paper calculation function of the control unit of the paper length measuring device may be realized by a program for operating the control unit, or part or all of them may be realized by hardware. May be.

  The above program may be read from a recording medium such as a CD-ROM into a storage unit in the image forming apparatus, or downloaded from a server or the like connected to a network such as the Internet to the storage unit in the image forming apparatus. Also good.

  The paper calculation function of the control unit of the paper length measuring device may be provided in the main control unit. In this case, various signals input to the control unit are input to the main control unit, and the main control unit It is sufficient to store pulse distance conversion information, thermal expansion coefficient information, eccentricity correction information, and the like in the storage unit.

  Although the image forming apparatus in each of the above embodiments has been described as a so-called tandem type, the present invention sequentially rotates a plurality of photosensitive drums provided for each color with respect to a single image carrier. The present invention can also be applied to a rotary type image forming apparatus that develops a toner image.

  The image forming apparatus in each of the above embodiments is an electrophotographic system, but the present invention can be applied to any system regardless of the system such as an ink jet system or a thermal transfer system.

FIG. 1 is a schematic diagram illustrating an example of a schematic configuration of an image forming apparatus according to a first embodiment of the present invention. FIG. 2A is a cross-sectional view taken along line AA in FIG. FIG. 2B is a cross-sectional view taken along the line BB in FIG. FIG. 3A is a schematic diagram illustrating an example of the internal structure of the intermediate roller. FIG. 3B is a schematic diagram illustrating an example of a deformed state of the intermediate roller. FIG. 4 is a schematic diagram illustrating an example of a schematic configuration of the encoder unit. FIG. 5 is a block diagram showing an example of a schematic configuration of the sheet length measuring apparatus according to the first embodiment of the present invention. FIG. 6 is a flowchart illustrating an example of the overall operation when the image forming apparatus forms images on both sides of a sheet. FIG. 7 is a waveform diagram showing an example of an edge detection signal, an encoder signal, and a Z-phase signal when the paper passes through the paper length measuring device. 6 is a flowchart illustrating an example of an operation when the paper length measuring device measures a paper length. FIG. 9 is a block diagram showing an example of a schematic configuration of a sheet length measuring apparatus according to the second embodiment of the present invention. FIG. 10A is a diagram illustrating an example of an encoder roller. FIG. 10B is a graph showing the relationship between the number of encoder pulse counts and the distance when the encoder roller rotates. FIG. 11 is a schematic diagram showing an example of a schematic configuration of a paper length measuring apparatus according to the third embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 2 ... Paper length measuring device, 3 ... Main control unit, 4K, 4Y, 4M, 4C ... Image forming unit, 5 ... Intermediate transfer belt, 10 ... Paper, 10a ... Conveyance path, 10b ... Starting end, 10c ... Termination, 10d ... Front side, 10e ... Back side, 11 ... Paper tray, 12 ... Conveying roller, 13 ... Paper sensor, 14 ... Transfer roll, 15 ... Fixer, 16 ... Cooling unit, 17 ... Paper reversing unit, 20 ... Paper length detection unit, 21 ... intermediate roller, 21a ... peripheral surface part, 22 ... encoder roller, 22a ... peripheral surface part, 22b, 22c ... central axis, 23 ... encoder part, 23a ... housing, 24 ... paper edge sensor, 25 ... Temperature sensor 26 ... Pressing roller 27A, 27B ... Support member 28 ... Control unit 29 ... Storage unit 40 ... Photoconductor drum 41 ... Charger 42 ... ROS 43 ... Developer 44 ... Static elimination , 50A to 50C ... supporting roller, 200 to 202 ... shaft, 210, 211 ... rubber layer, 230A, 230B ... bearing, 231 ... slit disk, 231a, 231b ... slit, 232A, 232B ... light emitting element, 233A, 233B ... Lens, 234 ... Fixed slit, 235A, 235B ... Light receiving element, 236A, 236B ... Amplifier, 280A, 280B ... Paper length calculation function, 281 ... Communication function, 290 ... Pulse distance conversion information, 291 ... Thermal expansion coefficient information, 292 ... Eccentricity correction information

Claims (8)

A first rotating portion that is in contact with the recording medium after fixing conveyed along the conveyance path, and rotates with conveyance of the recording medium;
A second peripheral surface portion formed of a material having a smaller thermal expansion coefficient than a material of the first peripheral surface portion of the first rotating portion is in contact with the first peripheral surface portion of the first rotating portion; A second rotating part that rotates in accordance with the rotation of the first rotating part;
A recording medium length measurement apparatus comprising: a length detection unit configured to detect a length of the recording medium in a conveyance direction based on a rotation amount of the second rotation unit.   The first peripheral surface portion includes a first layer and a second layer covering the first layer, and the second layer has a higher hardness than the first layer. The recording medium length measuring apparatus as described.   Further, a third rotating part is provided at a position facing the first rotating part via the transport path, and a third peripheral surface part comes into contact with the recording medium and rotates as the recording medium is transported. The recording medium length measuring device according to claim 1, comprising: The recording medium length measurement apparatus according to claim 3 , wherein the second rotating unit is arranged at a position deviating from a line connecting rotation centers of the first and third rotating units.   The length detection unit includes a signal generation unit that generates a rotation amount detection signal corresponding to the rotation amount of the second rotation unit, an end detection sensor that detects a start end and a termination end of the recording medium in the conveyance direction, The calculation unit according to claim 1, further comprising: a calculation unit that calculates a length in the transport direction of the recording medium based on a rotation amount detection signal from the signal generation unit and an end detection signal from the end detection sensor. Recording medium length measuring device.   The length detection unit includes a signal generation unit that generates a rotation amount detection signal corresponding to the rotation amount of the second rotation unit, a temperature sensor that detects the temperature of the second rotation unit, and the signal generation unit A calculation unit that acquires a rotation amount based on a rotation amount detection signal from the image sensor, corrects the acquired rotation amount based on a temperature detection signal from the temperature sensor, and calculates a length in the conveyance direction of the recording medium; The recording medium length measuring device according to claim 1, comprising:   The length detection unit stores a signal generation unit that generates a rotation amount detection signal corresponding to the rotation amount of the second rotation unit, and eccentricity correction information that corrects a rotation center shift of the second rotation unit. And a storage unit that acquires the rotation amount based on a rotation amount detection signal from the signal generation unit, corrects the acquired rotation amount based on the eccentricity correction information stored in the storage unit, and records the recording The recording medium length measurement apparatus according to claim 1, further comprising a calculation unit that calculates a length in the conveyance direction of the medium. An image forming unit that forms an image on a recording medium after fixing conveyed along a conveyance path;
The first peripheral surface portion is in contact with the recording medium, and the thermal expansion coefficient is higher than that of the material of the first peripheral surface portion of the first rotating portion and the first rotating portion that rotates as the recording medium is conveyed. A second rotating portion that is made of a small material and is in contact with the first peripheral surface portion of the first rotating portion, and rotates with the rotation of the first rotating portion; and A recording medium length measurement unit having a length detection unit that detects a length of the recording medium in the transport direction based on the rotation amount of the second rotation unit;
A reversing unit for reversing the front and back of the recording medium;
Based on the length in the conveyance direction of the recording medium measured by the recording medium length measurement unit, the image formed by the image forming unit on the recording medium whose front and back are reversed by the reversing unit An image forming apparatus comprising: a control unit that controls forming conditions.

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