JP5876716B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

  2. Description of the Related Art Conventionally, in an image forming apparatus such as a printer, a copying machine, a facsimile machine, or a multifunction machine, for example, a printer, an electrostatic latent image is formed by exposing the surface of a photosensitive drum uniformly charged by a charging roller with an LED head. The electrostatic latent image is developed by a developing unit to form a toner image, and the toner image is transferred to a sheet of paper as a medium by a transfer roller. In the fixing unit, the toner is transferred to the sheet by a heating roller and a pressure roller. By fixing, an image is formed.

  By the way, in the printer, the conveyance speed of the paper at the portion between the photosensitive drum and the transfer roller (hereinafter referred to as “transfer portion”) where the toner image on the photosensitive drum is transferred to the paper, that is, the transfer. The sheet is conveyed at a portion between the heating roller and the pressure roller (hereinafter referred to as a “fixing unit”) where the toner image is fixed on the sheet on the downstream side of the transfer portion in the sheet conveyance direction and the sheet conveyance direction. The speed, that is, the fixing section conveyance speed cannot be made completely equal.

  Therefore, the fixing unit conveyance speed is slightly lower than the transfer unit conveyance speed, a slack is formed on the paper between the transfer unit and the fixing unit, the amount of slack, that is, the amount of slack is detected, and the detected slack is detected. The fixing unit conveyance speed is controlled based on the amount so that the amount of slackness falls within a certain range (see, for example, Patent Document 1).

JP 2004-233437 A

  However, in the conventional printer, the amount of slack of the paper between the transfer unit and the fixing unit varies depending on the thickness of the paper, so that the amount of slack cannot be controlled with high accuracy.

  For example, if thin paper is used as paper, slack is likely to form, so if the fixing unit transport speed is controlled with a small amount of slack, the amount of slack varies or noise is detected when the amount of slack is detected The amount of slack may be erroneously detected.

  Further, when using thick paper as the paper, the thick paper is not easily slackened and it is difficult to control the fixing unit conveyance speed, and the paper may be pulled and the image may be shifted.

  It is an object of the present invention to provide an image forming apparatus that can solve the problems of the conventional printer and can control the amount of slackness of a medium with high accuracy.

Therefore, in the image forming apparatus of the present invention, an image forming unit for forming a developer image and transferring it to a medium, a first driving unit for transporting the medium in the image forming unit, and the medium A fixing device that is disposed downstream of the image forming unit in the transport direction and fixes a developer image on the transported medium, a second drive unit for transporting the medium in the fixer, and A slack detecting device having a slack detecting element for detecting slack of the medium formed between the image forming unit and the fixing device, and the slack detecting element detects slack of the medium by moving the slack detecting device. An adjustment unit that adjusts the detection position of the slack detection element when rotating, and rotation of one of the first and second drive units based on the slack of the medium detected by the slack detection element Slack changing speed And a control unit.
The slack detecting element detects slack of the medium by contacting the medium.
The adjustment unit moves the slack detection device in a direction in which the slack is formed in the medium, whereby the position where the slack detection element contacts the medium is substantially parallel to the direction in which the slack is formed in the medium. The detection position of the slack detection element is adjusted by moving in the proper direction.

According to the present invention, in the image forming apparatus, an image forming unit for forming a developer image and transferring it to the medium, a first driving unit for transporting the medium in the image forming unit, and the medium A fixing device that is disposed downstream of the image forming unit in the transport direction and fixes a developer image on the transported medium, a second drive unit for transporting the medium in the fixer, and A slack detecting device having a slack detecting element for detecting slack of the medium formed between the image forming unit and the fixing device, and the slack detecting element detects slack of the medium by moving the slack detecting device. An adjustment unit that adjusts the detection position of the slack detection element when rotating, and rotation of one of the first and second drive units based on the slack of the medium detected by the slack detection element Sag system to change speed And a part.
The slack detecting element detects slack of the medium by contacting the medium.
The adjustment unit moves the slack detection device in a direction in which the slack is formed in the medium, whereby the position where the slack detection element contacts the medium is substantially parallel to the direction in which the slack is formed in the medium. The detection position of the slack detection element is adjusted by moving in the proper direction.

  In this case, since the detection position of the slack detection element for detecting slack of the medium formed between the image forming unit and the fixing device is adjusted, the slack detection element is placed at an appropriate position according to the thickness of the medium. be able to.

  Therefore, the slack amount control unit can control the slack amount with high accuracy.

FIG. 3 is an exploded perspective view of the fixing device according to the first embodiment of the present invention. 1 is a schematic diagram of a printer according to a first embodiment of the present invention. It is a 1st control block diagram of the printer in the 1st Embodiment of this invention. It is a 2nd control block diagram of the printer in the 1st Embodiment of this invention. FIG. 3 is a diagram illustrating an arrangement state of a transfer unit and a fixing device according to the first embodiment of the present invention. FIG. 3 is a diagram illustrating a relationship between a fixing device and an eject guide according to the first embodiment of the present invention. It is a perspective view which shows the front cover of the fixing device in the 1st Embodiment of this invention. It is a disassembled perspective view of the front cover in the 1st Embodiment of this invention. It is a 1st figure which shows the attachment state of the slack detection apparatus in the 1st Embodiment of this invention. It is a 2nd figure which shows the attachment state of the slack detection apparatus in the 1st Embodiment of this invention. It is a 3rd figure which shows the attachment state of the slack detection apparatus in the 1st Embodiment of this invention. It is a 1st perspective view of the slack detection apparatus in the 1st Embodiment of this invention. It is a 2nd perspective view of the slack detection apparatus in the 1st Embodiment of this invention. It is a principal part enlarged view of the front cover in the 1st Embodiment of this invention. It is a perspective view which shows the surface of the adjuster in the 1st Embodiment of this invention. It is a perspective view which shows the back surface of the adjuster in the 1st Embodiment of this invention. It is a front view of the fixing device in the first embodiment of the present invention. It is a 1st figure for demonstrating the adjustment method of the position of the slack detection lever by the adjuster in the 1st Embodiment of this invention. It is a 2nd figure for demonstrating the adjustment method of the position of the slack detection lever by the adjuster in the 1st Embodiment of this invention. It is a 3rd figure for demonstrating the adjustment method of the position of the slack detection lever by the adjuster in the 1st Embodiment of this invention. It is a conceptual diagram for demonstrating the operation | movement when detecting the slack of a paper with the slack detection lever in the 1st Embodiment of this invention. It is a figure which shows the 1st state of the paper in the 1st Embodiment of this invention. It is a figure which shows the 1st state of the slack detection lever in the 1st Embodiment of this invention. It is a figure which shows the 2nd state of the paper in the 1st Embodiment of this invention. It is a figure which shows the 2nd state of the slack detection lever in the 1st Embodiment of this invention. It is a figure which shows the 3rd state of the paper in the 1st Embodiment of this invention. It is a figure which shows the 3rd state of the slack detection lever in the 1st Embodiment of this invention. It is a figure which shows the relationship between the fixing device and eject guide in the 2nd Embodiment of this invention. It is a disassembled perspective view of the slack detection unit in the 2nd Embodiment of this invention. It is a 1st figure for demonstrating operation | movement of the slack detection unit in the 2nd Embodiment of this invention. It is a 1st figure for demonstrating operation | movement of the principal part of the slack detection unit in the 2nd Embodiment of this invention. It is a 2nd figure for demonstrating operation | movement of the slack detection unit in the 2nd Embodiment of this invention. It is a 2nd figure for demonstrating operation | movement of the principal part of the slack detection unit in the 2nd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In this case, a color printer as an image forming apparatus will be described.

  FIG. 2 is a schematic view of the printer according to the first embodiment of the present invention.

  As shown in the figure, a paper feed mechanism for supplying paper as a medium to the image forming unit along the conveyance path is disposed at the lower part of the printer 11, and the paper feed mechanism serves as a medium storage unit. A paper cassette 24 is provided. The sheets are fed one by one from the sheet cassette 24 by the sheet feeding roller 22 and conveyed to the registration rollers 23a and 23b. At this time, since the registration rollers 23a and 23b are stopped, the conveyance of the sheets is stopped. Be made. When the registration rollers 23a and 23b are rotated, the sheet is sent to the image forming unit along with the rotation.

  The image forming unit includes black, yellow, magenta, and cyan image forming units 12Bk, 12Y, 12M, and 12C arranged in series from the upstream side to the downstream side in the paper conveyance direction, the image forming unit 12Bk, LED heads 15Bk, 15Y, 15M, and 15C as exposure devices disposed adjacent to 12Y, 12M, and 12C, and a transfer unit u1 disposed below the image forming units 12Bk, 12Y, 12M, and 12C. .

  The image forming units 12Bk, 12Y, 12M, and 12C are photoconductor drums 13Bk, 13Y, 13M, and 13C as image carriers, and charging devices that uniformly charge the surfaces of the photoconductor drums 13Bk, 13Y, 13M, and 13C. As a latent image formed on the surfaces of the charging rollers 14Bk, 14Y, 14M, and 14C and the photosensitive drums 13Bk, 13Y, 13M, and 13C, a toner as a developer is attached to form a visible image. Developer rollers 16Bk, 16Y, 16M, and 16C as developer carriers for forming toner images as developer images of the respective colors, and developer supply members that supply toner to the development rollers 16Bk, 16Y, 16M, and 16C Toner supply rollers 18Bk, 18Y, 18M, and 18C, and a toner cart as a developer storage unit for storing toner Cleaning devices 36Bk, 36Y, 36M, and 36C for removing toner remaining on the surfaces of the photosensitive drums 13Bk, 13Y, 13M, and 13C, and the like. Each of 36M and 36C includes a cleaning blade (not shown) as a first cleaning member and as a first removal member.

  The LED heads 15Bk, 15Y, 15M, and 15C are disposed above the photosensitive drums 13Bk, 13Y, 13M, and 13C so as to face the photosensitive drums 13Bk, 13Y, 13M, and 13C, and are uniformly formed. The surface of the charged photosensitive drums 13Bk, 13Y, 13M, and 13C is irradiated to form the electrostatic latent image.

  The transfer unit u1 is stretched freely by a driving roller 33a as a first belt traveling roller, a driven roller 33b as a second belt traveling roller, and the driving roller 33a and the driven roller 33b. An endless conveyance belt (transfer belt) 21 as a conveyance member that is provided and conveys paper along the image forming units 12Bk, 12Y, 12M, and 12C, and as a first transfer member, the conveyance belt 21 As a second transfer member that is arranged to face the photosensitive drums 13Bk, 13Y, 13M, and 13C, charges the paper to the opposite polarity to the toner, and transfers the toner image of each color onto the paper. Transfer roller 17Bk, 17Y, 17M, 17C, as a second cleaning member that removes toner adhering to the surface of the conveyor belt 21 Further, a transport belt blade (not shown) as a second removal member, a waste toner box 35 as a waste developer storage unit disposed below the driven roller 33b and collecting toner removed by the transport belt blade, A suction device (not shown) for applying an electrostatic charge to the transport belt 21 is provided.

  The conveyance belt 21 is caused to travel by being transmitted from a transfer unit drive motor (not shown) to a drive gear (not shown) disposed at an end of the drive roller 33a, and the drive roller 33a is rotated.

  The sheet sent to the image forming unit is adsorbed by static electricity to the conveyance belt 21 to which an electrostatic charge is applied, and the photosensitive drums 13Bk, 13Y, 13M, 13C and the transfer rollers 17Bk, 17Y as the conveyance belt 21 travels. , 17M, and 17C, and the toner images of the respective colors are transferred one after another by static electricity of the transfer rollers 17Bk, 17Y, 17M, and 17C, thereby forming a color toner image.

  The transfer portions for black, yellow, magenta, and cyan are arranged between the photosensitive drums 13Bk, 13Y, 13M, and 13C and the transfer rollers 17Bk, 17Y, 17M, and 17C. A conveyance unit is formed between the conveyance belt 21 and the conveyance belt 21.

  In this way, the sheet on which the color toner image is formed is sent to a fixing device 28 as a fixing device. The fixing device 28 serves as a first fixing member having a heating element such as a halogen lamp 28c therein, a heating roller 28a as a first roller, a second fixing member, and a first fixing member. A pressure roller 28b serving as a second roller, and the color toner image is heated and pressed between the heating roller 28a and the pressure roller 28b to be fixed on a sheet, thereby forming a color image. The A fixing unit is formed between the heating roller 28a and the pressure roller 28b.

  In the present embodiment, the fixing device 28 includes a heating roller 28a and a pressure roller 28b. Instead of the pressure roller 28b, a fixing belt is used as the second fixing member. Can do. In that case, a fixed pressure member is disposed in the fixing belt. A fixing unit is configured between the heating roller 28a and the fixing belt.

  The sheet on which the color image is formed is discharged from the main body of the printer 11, that is, the apparatus main body, by the discharge rollers 38 a and 38 b and is stacked on the stacker 39.

  When the fixing device 28 is attached to the apparatus main body, the fixing device 28 is held by an eject guide 34 as a fixing device holding member attached to the apparatus main body and as a discharge guide portion, and is arranged on the eject guide 34. It is electrically connected to a provided connector (not shown). A photocoupler sensor 37 serving as a detection signal generating unit that generates a sensor output indicating the amount of looseness when a paper slack is detected is disposed at a predetermined location of the eject guide 34. Established. The fixing device 28 and the eject guide 34 are positioned by a predetermined positioning projection, a hole for inserting the projection, and the like.

  In this case, since the photocoupler sensor 37 is disposed in the eject guide 34, the distance between the fixing device 28 and the photocoupler sensor 37 can be increased, and the photocoupler sensor 37 is affected by the heat of the halogen lamp 28c. There is nothing. Therefore, since the inexpensive photocoupler sensor 37 can be used as the detection signal generation unit, the cost of the printer 11 can be reduced.

  Further, the printer 11 is disposed on the conveyance path at a distance equal to or smaller than the minimum medium interval, and conveys rollers ri (i = 1, 2,...) For conveying the paper, and rotates the conveyance rollers ri. A drive motor (not shown) as a drive unit, a flap f1 for switching the transfer path, and the like are provided.

  Next, the control device of the printer 11 having the above-described configuration will be described.

  FIG. 3 is a first control block diagram of the printer according to the first embodiment of the present invention, and FIG. 4 is a second control block diagram of the printer according to the first embodiment of the present invention.

  In the figure, reference numeral 61 denotes a print control unit as a control unit including a microprocessor, a ROM, a RAM, an input / output port, a timer, etc. (not shown). The print control unit 61 is a printer 11 for forming a color image. Perform overall control. Reference numeral 62 denotes an interface control unit that receives print data and a control command transmitted from a host computer (not shown) as a host device, and transmits information representing the state of the printer 11 to the host computer. 62 analyzes the control command and divides the print data for each color and temporarily records it in the reception memory 63. The print data temporarily recorded in the reception memory 63 is edited by the print control unit 61 and is recorded in the image data editing memory 64 as image data of each color to be sent to the LED heads 15Bk, 15Y, 15M, and 15C.

  Reference numeral 65 denotes an operation panel serving as an operation unit. The operation panel 65 includes a screen (not shown) for displaying the status of the printer 11 and a switch (not shown) for an operator to input an instruction to the printer 11.

  Reference numeral 66 denotes a plurality of sensors for detecting the transport position of the paper, an index representing the environment in which the printer 11 is placed, and in this embodiment, the temperature in the printer 11, that is, an environmental index detection for detecting the environmental temperature. The sensor unit includes a temperature sensor as a unit and a temperature sensor as a temperature detection unit, a density sensor that detects the density of the color image, and the like. The sensor output of each sensor of the sensor unit 66 is sent to the print control unit 61.

  The print control unit 61 includes a charging control unit 67, an exposure control unit 69, a development control unit 71, a transfer control unit 73, a drive control unit 75, a conveyance belt motor control unit 79 as a conveyance control unit, a fixing control unit 81, The photocoupler sensor 37 and the like are connected.

  The charging control unit 67 receives an instruction from the printing control unit 61, applies a charging voltage to the charging rollers 14Bk, 14Y, 14M, and 14C, and charges the surfaces of the photosensitive drums 13Bk, 13Y, 13M, and 13C. Let The charging controller 67 includes charging voltage controllers 68Bk, 68Y, 68M, and 68C for controlling the voltages applied to the charging rollers 14Bk, 14Y, 14M, and 14C.

  The exposure control unit 69 receives an instruction from the print control unit 61, receives image data of each color recorded in the image data editing memory 64, and transmits the image data of each color to the LED heads 15Bk, 15Y, 15M, 15C, the LED elements of the LED array (not shown) are selectively made to emit light, and the surfaces of the photosensitive drums 13Bk, 13Y, 13M, 13C are irradiated with light to be exposed, and on the photosensitive drums 13Bk, 13Y, 13M, 13C. An electrostatic latent image is formed on the surface. The exposure control unit 69 includes head control units 70Bk, 70Y, 70M, and 70C for sending image data to the LED heads 15Bk, 15Y, 15M, and 15C at a predetermined timing.

  The development control unit 71 receives an instruction from the print control unit 61, applies a development voltage to each of the development rollers 16Bk, 16Y, 16M, and 16C, and applies the development voltage to each of the photosensitive drums 13Bk, 13Y, 13M, and 13C. A toner image is formed by attaching toner to the electrostatic latent image formed in (1). The development control unit 71 includes development voltage control units 72Bk, 72Y, 72M, and 72C for controlling the voltages applied to the development rollers 16Bk, 16Y, 16M, and 16C.

  The transfer control unit 73 receives an instruction from the print control unit 61, applies a transfer voltage to each of the transfer rollers 17Bk, 17Y, 17M, and 17C, and applies the transfer voltage onto the photosensitive drums 13Bk, 13Y, 13M, and 13C. The formed toner image is transferred to a sheet. The transfer control unit 73 includes transfer voltage control units 74Bk, 74Y, 74M, and 74C for sequentially transferring the toner images onto the paper.

  The drive control unit 75 receives an instruction from the print control unit 61, and serves as an image forming drive unit and a drive motor as a first drive unit for conveying paper in the image forming unit. 77Bk, 77Y, 77M, and 77C are driven to rotate the photosensitive drums 13Bk, 13Y, 13M, and 13C, the charging rollers 14Bk, 14Y, 14M, and 14C, and the developing rollers 16Bk, 16Y, 16M, and 16C. The drive control unit 75 includes drive motor control units 76Bk, 76Y, 76M, and 76C for driving the drive motors 77Bk, 77Y, 77M, and 77C.

  Further, the conveyance belt motor control unit 79 receives an instruction from the print control unit 61 and drives a conveyance belt motor 80 as a driving unit for traveling the conveyance belt 21 for conveying the sheet in the image forming unit. Then, the drive roller 33a is rotated, and the transport belt 21 is caused to travel.

  The fixing control unit 81 receives an instruction from the printing control unit 61, applies a fixing voltage to the halogen lamp 28c provided in the fixing device 28, and fixes the toner image transferred onto the sheet. In the fixing controller 81, the heater lamp 81c is turned on / off by the heater controller 81a based on the temperature detected by the fixing thermistor 84, and the fixing device 28 has reached a predetermined set temperature. Sometimes, the motor controller 81b as the slack amount controller drives the fixing motor 82 as the second driving unit for transporting the paper in the fixing device 28, and the heating roller 28a and the pressure roller 28b are rotated. It is done.

  Next, the fixing device 28 will be described.

  FIG. 1 is an exploded perspective view of a fixing device according to the first embodiment of the present invention, FIG. 5 is a view showing an arrangement state of a transfer unit and a fixing device according to the first embodiment of the present invention, and FIG. FIG. 7 is a perspective view showing a front cover of the fixing device according to the first embodiment of the present invention, and FIG. 7 is a view showing a relationship between the fixing device and the ejection guide in the first embodiment of the invention.

  In the figure, u1 is a transfer unit for conveying paper, 28 is a fixing device, and 34 is an eject guide for holding the fixing device 28.

  The transfer unit u1 includes a driving roller 33a, a driven roller 33b, and a conveying belt 21.

  The fixing device 28 includes a housing Cs1 including a main body 101 and a front cover 41 that covers the front of the main body 101. In the main body 101, a heating roller 28a and a pressure roller 28b are rotatably disposed, and connectors 102 and 103 are disposed below the main body 101 so as to protrude.

  A color toner image is formed on the front panel portion 111 of the front cover 41, and an introduction port 104 for taking the paper conveyed by the conveyance belt 21 into the housing Cs1 is formed. On the lower edge, a guide 106 is formed so as to rise obliquely into the housing Cs1 and toward the fixing portion between the heating roller 28a and the pressure roller 28b. Further, a discharge port (not shown) for discharging the sheet on which the color image is fixed is formed at a position corresponding to the introduction port 104 in the main body 101.

  A through hole h1 is formed in the center of the lower edge eg1 of the guide 106 in the width direction from the front panel portion 111 to the introduction port 104. The through hole h1 is penetrated and the top is slightly protruded. A slack detecting lever 42 as a slack detecting element for detecting slack of the paper is provided. Further, in the vicinity of the through hole h1 in the front panel portion 111, an adjustment unit is used to adjust the position of the slack detection lever 42 when the slack detection lever 42 detects the slack of the paper, that is, the detection position. The adjuster 44 is swingably disposed. The slack detection lever 42 contacts the paper and is displaced according to the slack amount of the paper, and generates a sensor output of the photocoupler sensor 37 in accordance with the displacement. Therefore, the amount of slack in the paper can be detected by the photocoupler sensor 37.

  The eject guide 34 includes a holding portion 121 extending horizontally, a rising portion 122 formed vertically rising from one end of the holding portion 121, and a guide portion 123 extending horizontally from the upper end of the rising portion 122. The fixing unit 28 is held by the holding unit 121 and the rising unit 122. The holding unit 121 is provided with connectors 126 and 127 that are connected to the connectors 102 and 103 when the fixing device 28 is placed on the holding unit 121. The photocoupler sensor 37 is disposed at the bottom. The guide unit 123 is formed along a discharge port formed in the main body unit 101 and guides the paper discharged from the discharge port so as to be conveyed in the horizontal direction. For this purpose, a plurality of guide ribs 129 are formed on the guide portion 123 and formed with a predetermined interval. The photocoupler sensor 37 includes a light emitting part 37a made of a light emitting diode and a light receiving part 37b made of a light receiving transistor, and the light emitting part 37a and the light receiving part 37b are arranged at a predetermined distance from each other. When the light receiving unit 37b receives the light generated by the light emitting unit 37a, the photocoupler sensor 37 is turned on. When the light generating unit 37b stops receiving the light generated by the light emitting unit 37a, the photocoupler sensor 37 is turned on. Turns off.

  Next, a slack detection device as a slack detection unit for attaching the slack detection lever 42 to the front cover 41 will be described.

  FIG. 8 is an exploded perspective view of the front cover according to the first embodiment of the present invention, FIG. 9 is a first view showing the attachment state of the slack detecting device according to the first embodiment of the present invention, and FIG. FIG. 11 shows a mounting state of the slack detecting device according to the first embodiment of the present invention, and FIG. 11 shows a third view showing a mounting state of the slack detecting device according to the first embodiment of the present invention. FIG. 13 is a first perspective view of the slack detection device according to the first embodiment of the present invention, FIG. 13 is a second perspective view of the slack detection device according to the first embodiment of the present invention, and FIG. FIG. 15 is a perspective view showing the surface of the adjuster according to the first embodiment of the present invention, and FIG. 16 is an adjuster according to the first embodiment of the present invention. FIG. 17 is a perspective view showing the back surface of the first embodiment of the present invention. FIG. 18 is a first view for explaining a method of adjusting the position of the slack detecting lever by the adjuster according to the first embodiment of the present invention, and FIG. 19 is a first view of the present invention. FIG. 20 illustrates a method for adjusting the position of the slack detection lever by the adjuster according to the first embodiment of the present invention, and FIG. 20 illustrates a method for adjusting the position of the slack detection lever by the adjuster according to the first embodiment of the present invention. It is the 3rd figure for doing.

  In the figure, reference numeral 41 denotes a front cover, and 131 denotes a slack detection device attached to the front cover 41 so as to be movable in the vertical direction (arrows A and B directions).

  The front cover 41 includes a bottom panel 133 extending from the lower end of the front panel 111 toward the rear (the main body 101 (FIG. 1) side). A mounting hole h2 is formed for mounting. A pair of ribs 41a as unit guides are formed so as to rise vertically from the mounting hole h2 in the bottom panel portion 133 and project from the front panel portion 111. The rib 41 a includes a guide portion 137 that guides the slack detection device 131 and a locking portion 138 that is formed in a direction perpendicular to the guide portion 137 and that locks the slack detection device 131.

  And between each rib 41a in the said front panel part 111, the front panel part 111 is penetrated and it is extended in the horizontal direction, and the slot h3 is formed, The said slot h3 in the said slack detection apparatus 131 is formed. The locking piece 43b of the slack detection lever holder 43 as a detection element holding member, which will be described later, is projected to the front (front panel section 111 side) at a location corresponding to Is formed. The dimensions of the slot h3 and the locking piece 43b are set so that the locking piece 43b can move in the vertical direction by a predetermined distance within the slot h3.

  Then, when the locking piece 43b is moved in the vertical direction by a predetermined distance in the slot h3, the slack detecting device 131 is moved in the vertical direction by the predetermined distance along each rib 41a to detect slack. The lever 42 is moved in the vertical direction.

  The slack detection device 131 biases the slack detection lever 42, the slack detection lever holder 43 that holds the slack detection lever 42 in a swingable manner, and the slack detection lever holder 43 downward (in the direction of arrow C). A holder spring 45 as a first urging member, a lever spring 47 as a second urging member for urging the slack detection lever 42, and the slack detection lever 42 are supported with respect to the slack detection lever holder 43, A lever post 48 as a support that forms a swing fulcrum of the slack detection lever 42 is provided. The lever post 48 is press-fitted into a hole h4 formed in the slack detection lever holder 43.

  The slack detection lever 42 penetrates the lever post 48 and serves as a center of swinging of the slack detection lever 42 (not shown), a first arm m1 extending in the radial direction from the rotation support hole, and the first arm m1. A second arm m2 and the like extending in the radial direction at a predetermined angle with respect to the arm m1, in the present embodiment, at an angle of 90 [°] are provided, and the slack of the paper is formed at the tip of the first arm m1. A detection piece 141 for detection shields the light emitting portion 37a and the light receiving portion 37b of the photocoupler sensor 37 at the tip (in the present embodiment, the lower end) of the second arm m2. 42a is formed.

  Normally, the slack detection lever 42 is urged in the direction of arrow D by the lever spring 47, and is placed at a position where the shielding part 42a shields the light emitting part 37a and the light receiving part 37b, that is, a shielding position. When the detection piece 141 is pushed downward by the sheet on which the slack is formed, the slack detection lever 42 is rotated in the direction opposite to the direction of the arrow D, and the shielding part 42a is turned into the light emitting part 37a and the light receiving part 37b. Are placed in a position where they are not shielded, that is, in a non-shielded position.

  The lever spring 47 is composed of a torsion spring. The lever post 48 penetrates the coil portion, and one end is engaged with a predetermined portion of the slack detection lever 42 and the other end is engaged with a predetermined portion of the slack detection lever holder 43. It is arranged to be stopped.

  The detection piece 141 has a triangular shape and extends in a direction perpendicular to the main body of the first arm m1, that is, in the paper transport direction, and the slack detection device 131 is connected to the front cover 41. When attached to the tip, the tip end portion (triangular apex portion) pk is protruded upward from the through hole h1.

  In addition, the holder spring 45 is engaged with an engagement protrusion 41c formed by projecting one end from the front panel portion 111 between the bottom panel portion 133 and the slack detection lever holder 43, and the other end thereof. The slack detecting lever holder 43 is disposed and positioned so as to be engaged with a locking projection 43c formed to protrude from the shoulder 145 of the slack detecting lever holder 43.

  A support post 41d is formed directly below the slot h3 by projecting from the front panel portion 111 toward the transfer unit u1 (FIG. 5), and by screwing the screw 46 to the support post 41d, The adjuster 44 can be swingably mounted with the support post 41d as the swing center. The support post 41d is slightly longer than the thickness of the adjuster 44 so that the adjuster 44 can be smoothly rotated.

  The adjuster 44 includes a main body portion 151 having a fan shape, a cam 44b formed of an annular body formed by protruding on the back surface of the main body portion 151 by a predetermined thickness, and a predetermined thickness further than the cam 44b. A rotation fulcrum portion 44c formed to protrude is formed, and a through hole h5 is formed through the main body portion 151, the cam 44b and the rotation fulcrum portion 44c. The through hole h5 is formed to protrude from the front panel portion 111. The supported support post 41d is inserted. Each of the cam 44b and the rotation fulcrum portion 44c has a circular shape, and the center of the cam 44b is eccentric with respect to the center of the rotation fulcrum portion 44c.

  A scale 44a indicating the position of the slack detecting lever 42 is formed in the vicinity of the arc-shaped edge portion on the surface S1 of the main body 151, and a knob 44d extends from the surface S1 between the scale 44a and the through hole h5. It is formed by protruding. The front panel 111 is formed with a pointer 152 adjacent to the scale 44a and pointing to the first to third portions x1 to x3 of the scale 44a as the adjuster 44 rotates.

  By the way, the cam 44b and the locking piece 43b function as a movement direction converting portion that converts the rotational movement of the adjuster 44 into a linear movement of the slack detection lever 42 and also as a cam mechanism, and the locking piece 43b is a cam follower. Also works. The cam 44b constitutes the main driving portion of the cam mechanism, and the locking piece 43b constitutes the driven portion of the cam mechanism.

  For this purpose, the locking piece 43b is protruded by a predetermined amount from the front panel portion 111 through the slot h3, and on the lower surface of the portion protruding from the front panel portion 111 and the outer peripheral surface of the cam 44b. When the formed cam surface S2 is always in contact with the adjuster 44 and the cam 44b is rotated as the adjuster 44 is rotated, the lower surface of the portion protruding from the front panel 111 and the cam surface S2 slide. Be made.

  The cam surface S2 is decentered with respect to the swing center of the adjuster 44. The highest point of the cam surface S2 when the adjuster 44 is placed horizontally is defined as qm, and a predetermined distance from the point qm to the scale 44a side. In this embodiment, a point separated by 30 [°] is defined as qu, and a point separated from the point qm by a predetermined angle, in this embodiment, a point separated by 30 [°]. Assuming qd, the distance from the center of the through hole h5, that is, the swing center of the adjuster 44, to the cam surface S2 is the shortest at the point qd and the longest at the point cu.

  Therefore, when the cam 44b is rotated by rotating the adjuster 44, the locking piece 43b is moved vertically within the slot h3 by the predetermined distance, and the slack detection lever 42 is moved vertically. Let

  That is, when the operator operates the knob 44d and rotates the adjuster 44 in the direction of arrow F so that the pointer 152 points to the first part x1 of the scale 44a as shown in FIG. 18, the cam surface S2 Is brought into contact with the locking piece 43b. As a result, the locking piece 43b is placed at the highest position in the slot h3, and the slack detection lever 42 and the slack detection lever holder 43 are moved upward (in the direction of arrow A).

  Further, when the operator operates the knob 44d and rotates the adjuster 44 in the arrow G direction so that the pointer 152 points to the second portion x2 of the scale 44a as shown in FIG. 19, the cam surface S2 The point qm is brought into contact with the locking piece 43b. As a result, the locking piece 43b is placed at the center position in the slot h3, and the slack detection lever 42 and the slack detection lever holder 43 are moved downward (in the direction of arrow B).

  Then, when the operator operates the knob 44d and further rotates the adjuster 44 in the arrow G direction so that the pointer 152 points to the third portion x3 of the scale 44a as shown in FIG. 20, the cam surface The point qd of S2 is brought into contact with the locking piece 43b. As a result, the locking piece 43b is placed at the lowest position in the slot h3, and the slack detection lever 42 and the slack detection lever holder 43 are moved further downward (in the direction of arrow B).

  Therefore, by rotating the adjuster 44, the slack detection lever 42 and the slack detection lever holder 43 can be moved in the vertical direction, and slack of the paper can be detected at different positions.

  In the present embodiment, the adjuster 44 is rotated so that the pointer 152 points to the first to third portions x1 to x3 of the scale 44a, and the slack detection lever 42 and the slack detection lever holder 43 are moved to a predetermined position. Although the cam surface S2 is formed by a continuous outer circumferential surface of the circle, the pointer 152 can be placed anywhere between the first to third portions x1 to x3 of the scale 44a. Even if the adjuster 44 is rotated to point, the locking piece 43b can be placed at a predetermined position in the slot h3. Therefore, the slack detection lever 42 and the slack detection lever holder 43 can be placed at appropriate positions according to the thickness of the paper.

  Next, the operation when the slack detection lever 42 detects the slack of the paper will be described.

  FIG. 21 is a conceptual diagram for explaining the operation when the slack detection lever detects the slackness of the paper according to the first embodiment of the present invention, and FIG. 22 shows the first of the paper according to the first embodiment of the present invention. FIG. 23 is a diagram illustrating a first state of the slack detection lever according to the first embodiment of the present invention, and FIG. 24 is a diagram illustrating a second state of the sheet according to the first embodiment of the present invention. FIG. 25 is a diagram showing a second state of the slack detection lever in the first embodiment of the present invention, and FIG. 26 is a third state of the sheet in the first embodiment of the present invention. FIG. 27 is a diagram showing a third state of the slack detection lever in the first embodiment of the present invention.

  In the figure, 12C is an image forming unit, 13C is a photosensitive drum, 21 is a conveyor belt, 28 is a fixing device, 28a is a heating roller, 28b is a pressure roller, 37 is a photocoupler sensor, 41 is a front cover, and 42 is slack. A detection lever, 48 is a lever post, 104 is an introduction port, 106 is a guide, 111 is a front panel portion, 141 is a detection piece, pk is a tip portion of the detection piece 141, and P is paper. A cyan transfer portion E1 is formed between the photosensitive drum 13C and the conveying belt 21, and a fixing portion E2 is formed between the heating roller 28a and the pressure roller 28b.

  As shown in FIG. 22, when the paper P is not slack, that is, when the paper P is stretched linearly, the leading end pk of the detection piece 141 is placed at the highest position, as shown in FIG. Furthermore, the shielding part 42a of the slack detection lever 42 is placed at the shielding position and shields the light emitting part 37a and the light receiving part 37b of the photocoupler sensor 37. Therefore, the photocoupler sensor 37 is turned off.

  Then, as shown in FIG. 24, when the slack occurs in the paper P and the paper P is bent, the leading end pk of the detection piece 141 is pushed downward, and as shown in FIG. Rotated in the direction of arrow H, the photocoupler sensor 37 is switched from a state where the light emitting unit 37a and the light receiving unit 37b are shielded to a state where it is not shielded.

  Further, as shown in FIG. 26, when the slack amount of the paper P increases and the paper P is greatly curved, the leading end pk of the detection piece 141 is pushed further downward, and the slack detection is performed as shown in FIG. The lever 42 is further rotated in the direction of arrow H. At this time, the shielding part 42a is placed at the non-shielding position and does not shield the light emitting part 37a and the light receiving part 37b of the photocoupler sensor 37, so the photocoupler sensor 37 remains on.

  By the way, in the present embodiment, the transfer unit conveyance speed that is the first conveyance speed of the paper P in the transfer unit E1 is V1, and the fixing unit conveyance speed that is the second conveyance speed of the paper P in the fixing unit E2. Is set to V2, the fixing unit conveyance speed V2 is slightly lower than the transfer unit conveyance speed V1, and slack is formed on the paper P between the transfer unit E1 and the fixing unit E2.

In this case, since a speed difference ΔV is formed between the transfer portion conveyance speed V1 and the fixing portion conveyance speed V2, assuming that the time after the paper P reaches the fixing portion E2 is T, the paper in the transfer portion E1. The difference ΔQ between the transport amount Q1 of P and the transport amount Q2 of the paper P in the fixing unit E2
ΔQ = ΔV · T
Occurs and slack is formed on the paper P.

  Therefore, as shown in FIG. 26, the amount of slackness of the paper P increases, and as shown in FIG. 27, when the shielding portion 42a is placed at the non-shielding position and the photocoupler sensor 37 is turned on, the fixing control portion. The motor control unit 81b 81 (FIG. 4) performs a motor control process, changes the rotation speed of the fixing motor 82, and controls the slack amount of the paper P by increasing the fixing unit conveyance speed V2. Note that the slackness of the paper P increases even when the photocoupler sensor 37 is turned on and the fixing unit conveyance speed V2 is increased.

  In this case, the motor control unit 81b reads the sensor output from the photocoupler sensor 37 at every predetermined timing, and gradually increases the fixing unit conveyance speed V2 until the photocoupler sensor 37 is turned off. The transfer speed is set higher than V1.

  Accordingly, when the slack amount of the paper P is reduced, the slack detection lever 42 is rotated in the direction of the arrow D (FIG. 12) by the biasing force of the lever spring 47 (FIG. 11), and the shielding portion 42a is brought into the shielding position. When placed, the photocoupler sensor 37 is turned off.

  Subsequently, the motor control unit 81b reads the sensor output from the photocoupler sensor 37 at every predetermined timing, gradually decreases the fixing unit conveyance speed V2 until the photocoupler sensor 37 is turned on, and transfers the transfer unit. Lower than the conveyance speed V1.

  In this manner, the motor control unit 81b controls the fixing unit conveyance speed V2 until the printing of the paper P is completed, and controls the amount of slackness of the paper P.

  Therefore, in the present embodiment, the amount of slackness of the paper P can be kept within a certain range. Therefore, the amount of slackness is too large, and the toner image on the paper P rubs against a nearby member, or the amount of slackness is small. It is too small, and the paper P is not pulled and the image is not shifted. As a result, the image quality can be improved.

  In this embodiment, in order to control the amount of looseness, the fixing unit conveyance speed V2 is controlled. However, the transfer unit conveyance speed V1 can be controlled. In this case, the slack amount increases, and when the photocoupler sensor 37 detects the slack of the paper P and is turned on, the drive motor control units 76Bk, 76Y, 76M, 76C of the drive control unit 75 as the slack amount control unit or The conveyance belt motor control unit 79 changes the rotation speed of the drive motors 77Bk, 77Y, 77M, and 77C or the conveyance belt motor 80, and lowers the transfer unit conveyance speed V1.

  By the way, the fixing unit conveyance speed V2 is based on the same amount of slack when the paper P is a thin paper that is weak and easily forms slack, and a thick paper that is strong and hardly forms slack. If it is going to control, slack amount cannot be controlled accurately.

  That is, when thin paper is used, slack is likely to be formed on the paper P. Therefore, if the fixing unit conveyance speed V2 is controlled in a state where the slack amount is small, the slack amount fluctuates or noise is detected in the sensor output of the photocoupler sensor 37. May occur and the slack may be erroneously detected. Therefore, when using thin paper, it is desirable to control the fixing unit conveyance speed V2 so that the photocoupler sensor 37 is turned on when the amount of looseness becomes sufficiently large.

  In addition, when using thick paper, it is difficult for slack to be formed on the paper P, and it is difficult to control the fixing unit conveyance speed V2, so the paper P may be pulled and the image may be displaced. Therefore, when using thick paper, it is desirable to control the fixing unit conveyance speed V2 so that the photocoupler sensor 37 is turned on even if the slack amount is small.

  Therefore, in the present embodiment, when using thin paper, the operator operates the knob 44d, and as shown in FIG. 20, the adjuster 44 so that the pointer 152 points to the third portion x3 of the scale 44a. Is rotated in the direction of arrow G, the point qd of the cam surface S2 is brought into contact with the locking piece 43b. The locking piece 43b is placed at the lowest position in the slot h3, and the slack detection lever 42 and the slack detection lever holder 43 are moved downward (in the direction of arrow B). Therefore, the photocoupler sensor 37 can be turned on when the amount of looseness becomes sufficiently large.

  Further, when using cardboard, the operator operates the knob 44d and rotates the adjuster 44 in the direction of arrow F so that the pointer 152 points to the first part x1 of the scale 44a as shown in FIG. As a result, the point qu of the cam surface S2 is brought into contact with the locking piece 43b. The locking piece 43b is placed at the highest position in the slot h3, and the slack detection lever 42 and the slack detection lever holder 43 are moved upward (in the direction of arrow A). Therefore, even if the amount of slack is small, the photocoupler sensor 37 can be turned on.

  Thus, in the present embodiment, the detection position of the slack detection lever 42 is adjusted, so that the slack detection lever 42 can be moved in the vertical direction according to the thickness of the paper P and placed at an appropriate position. it can. Therefore, since the slack is not erroneously detected or the paper P is pulled and the image is not shifted, the image quality can be improved.

  In the present embodiment, since the pair of ribs 41a (FIG. 9) is formed perpendicular to the bottom panel portion 133, the slack detection lever 42 and the slack detection lever holder 43 can be moved in the vertical direction. it can. In addition, the position where the rib 41a is formed is set so that the photocoupler sensor 37 is disposed immediately below the lever post 48, and the photocoupler sensor 37 passes between the light emitting portion 37a and the light receiving portion 37b. A line extending in the direction of the slack detecting device 131 and a moving direction of the slack detecting device 131 are made parallel.

  Therefore, when the slack detection lever 42 and the slack detection lever holder 43 are moved in the vertical direction, the inclination of the slack detection lever 42 when the shielding portion 42a is placed at the shielding position does not change. As a result, the photocoupler sensor 37 can be reliably turned on / off according to the inclination of the slack detection lever 42.

  By the way, in the present embodiment, when the fixing device 28 is mounted on the apparatus main body, the fixing device 28 and the eject guide 34 (FIG. 2) are provided with predetermined positioning protrusions and holes for inserting the protrusions. However, at this time, if the slack detection lever 42 cannot be accurately arranged with respect to the photocoupler sensor 37, the slack of the paper cannot be detected with high accuracy.

  Therefore, a second embodiment of the present invention in which the slack detection lever 42 can be arranged with high accuracy with respect to the photocoupler sensor 37 will be described. In addition, about the thing which has the same structure as 1st Embodiment, the same code | symbol is provided and the effect of the same embodiment is used about the effect of the invention by having the same structure.

  FIG. 28 is a diagram showing the relationship between the fixing device and the ejection guide in the second embodiment of the present invention, FIG. 29 is an exploded perspective view of the slack detection unit in the second embodiment of the present invention, and FIG. FIG. 31 is a first diagram for explaining the operation of the slack detection unit according to the second embodiment of the invention, and FIG. 31 is a diagram for explaining the operation of the main part of the slack detection unit according to the second embodiment of the present invention. FIG. 32 is a second diagram for explaining the operation of the slack detection unit in the second embodiment of the present invention, and FIG. 33 is a diagram of the slack detection unit in the second embodiment of the present invention. It is a 2nd figure for demonstrating operation | movement of the principal part.

  In the figure, 34 is an eject guide as a fixing device holding member and as a discharge guide portion, 51 is a slack detecting device disposed in a fixing device 28 as a fixing device, and 161 is detachably attached to the eject guide 34. The slack detecting device 51 and the signal generating device 161 are detachably connected to each other. That is, by attaching the fixing device 28 to the ejection guide 34, the slackness detecting device 51 and the signal generating device 161 can be connected, and by removing the fixing device 28 from the ejection guide 34, the slackness detecting device 51 and the signal generation are generated. The device 161 can be separated. The slack detection unit 51 and the signal generator 161 constitute a slack detection unit 50.

  As in the first embodiment, the slack detection device 51 is attached to the front cover 41 so as to be movable in the vertical direction along the rib 41a as a unit guide, and slack as a slack detection element. A detection lever 42, a slack detection lever holder 43 as a detection element holding member that swingably holds the slack detection lever 42, and a first biasing member that biases the slack detection lever holder 43 downward. A holder spring 45, a lever spring 47 as a second urging member for urging the slack detection lever 42, and the slack detection lever 42 are supported with respect to the slack detection lever holder 43, and the swing fulcrum of the slack detection lever 42 A lever post 48 or the like is provided as a support member for forming the.

  The slack detection lever 42 penetrates the lever post 48 and serves as a center of swinging of the slack detection lever 42 (not shown). The first and second arms m1 and m2 extend radially from the rotation support hole. And a detection piece 141 for detecting looseness of the sheet P as a medium at the tip of the first arm m1 is provided at the tip of the second arm m2 (lower end in the present embodiment). A shielding part 42a for shielding the light emitting part 37a and the light receiving part 37b in the photocoupler sensor 37 as a detection signal generating part and as an optical sensor is formed.

  The detection piece 141 has a triangular shape and is extended in a direction perpendicular to the main body of the first arm m1, that is, in the paper transport direction, and the slack detection device 51 is connected to the front cover 41. When attached to the front end, the tip pk protrudes upward from the through hole h1.

  Reference numeral 44 denotes an adjuster as an adjustment unit for adjusting the detection position of the slack detection lever 42.

  On the other hand, the signal generator 161 has a sensor signal base holding part 163 attached to a sensor holder base 163 as a detection signal generator support body and a sensor holder spring 164 as an urging member to the sensor holder base 163. The sensor holder 162 as a member, and the photocoupler sensor 37 that is attached to the sensor holder 162 and detects the looseness of the paper P, etc. are provided. The photocoupler sensor 37 is held by the sensor holder 162 in a sensor holder base. 163 is supported.

  A locking portion 201 for detachably attaching the sensor holder base 163 to the eject guide 34 is formed at a predetermined position on the outer peripheral edge of the sensor holder base 163.

  By the way, as described above, when the fixing device 28 is mounted on the apparatus main body, if the slack detection lever 42 cannot be disposed with high accuracy with respect to the photocoupler sensor 37, the slack of the paper P is accurately detected. It cannot be detected.

  Therefore, in the present embodiment, as shown in FIGS. 32 and 33, the sensor holder 162 is urged by the urging force of the sensor holder spring 164 before the fixing device 28 is attached to the apparatus main body. It is arranged so as to float above the position where it is originally arranged with respect to the base 163 (on the side of the slack detecting device 51).

  For this purpose, the sensor holder 162 includes a groove 203 for mounting the photocoupler sensor 37, and flanges 204 and 205 formed on both sides of the groove 203 so as to extend in the horizontal direction. The guide holes 162c and 162d are formed in the sensor holder base 163. The guide pins 163a and 163b are attached to predetermined positions of the sensor holder base 163, and the guide pins 163a and 163b are inserted into the guide holes 162c and 162d. In this case, the inner diameter of the guide holes 162c and 162d is made smaller than the outer diameter of the main body of the guide pins 163a and 163b so that a predetermined gap is formed between the guide pins 163a and 163b and the guide holes 162c and 162d. The Therefore, the sensor holder 162 can be moved by a predetermined distance in the plane direction with respect to the sensor holder base 163. The guide pins 163a and 163b have a head portion hd at the upper end of the main body, and the outer diameter of the head portion hd is larger than the inner diameter of the guide holes 162c and 162d. Therefore, the sensor holder 162 does not come off the sensor holder base 163 when the signal generator 161 and the sensor holder 162 are engaged and disengaged.

  Then, in order to attach the slack detecting device 51 to the signal generating device 161, the slack detecting lever holder 43 is protruded downward to form positioning projections 53a and 53b as first positioning elements. Positioning holes 162a and 162b as second positioning elements are formed.

  In addition, in the present embodiment, at least one of the positioning protrusions 53a and 53b, the positioning rib 53c as a third positioning element is directed rearward (downstream in the transport direction of the paper P) from the positioning protrusion 53b. A pressing surface 162e as a fourth positioning element is formed at a predetermined location in the sensor holder 162, in this embodiment, on the upper surface of the block in which the positioning hole 162b is formed.

  Therefore, when the fixing device 28 is mounted on the apparatus main body, the positioning protrusions 53a and 53b are fitted into the positioning holes 162a and 162b, so that the plane direction (lateral direction and vertical direction) between the slack detecting device 51 and the signal generating device 161 is obtained. Can be positioned. At this time, since the pressing surface 62e is pressed by the positioning rib 53c, the slackness detecting device 51 and the signal generating device 161 can be positioned in the height direction.

  As a result, the slack detection lever 42 can be disposed with high precision with respect to the photocoupler sensor 37, so that slack of the paper P can be detected with high precision.

  Further, by connecting the slack detecting device 51 and the signal generating device 161, the slack detecting device 51 and the signal generating device 161 can be positioned in the plane direction and the height direction. Even if the positioning accuracy with respect to the position 34, the position where the rising portion 122 is formed, and the tilting accuracy are low, the slack detection lever 42 can be disposed with respect to the photocoupler sensor 37 with high accuracy. Furthermore, the shape of each part which comprises the slack detection unit 50 can be designed freely, and the slack detection unit 50 can be reduced in size.

  In each of the above embodiments, the tandem type color printer in which the image forming units 12Bk, 12Y, 12M, and 12C (FIG. 2) are arranged in the conveyance direction of the paper P has been described. The present invention can be applied to other color printers, single color printers, and the like. Further, the present invention can be applied to an image forming apparatus such as a copying machine, a facsimile machine, and a multifunction machine.

  Further, in each of the embodiments, the slack detection lever 42 is used as a slack detection element, but instead of the slack detection lever 42, a slack detection roller is used as a slack detection element, It is possible to use a non-contact slack detection sensor that detects slack of the paper by measuring the distance to the paper P.

  Further, in each of the embodiments, the slack detection lever 42 and the slack detection lever holder 43 are disposed in the fixing device 28. However, the slack detection lever 42 and the slack detection lever holder 43 are disposed between the transfer unit u1 and the fixing device 28. can do.

  Further, in each of the embodiments, the adjuster 44 is manually rotated, but can be automatically rotated.

  The paper P is used as the medium, but a film material, a cloth material, or the like can be used instead of the paper P.

  The present invention is not limited to the above embodiments, and various modifications can be made based on the gist of the present invention, and they are not excluded from the scope of the present invention.

DESCRIPTION OF SYMBOLS 11 Printer 28 Fixing device 42 Slack detection lever 50, 131 Slack detection device 77Bk, 77Y, 77M, 77C Drive motor 81b Motor control part 82 Fixing motor P Paper

Claims (10)

(A) an image forming unit for forming a developer image and transferring it to a medium;
(B) a first drive unit for conveying a medium in the image forming unit;
(C) a fixing device disposed on the downstream side of the image forming unit in the conveyance direction of the medium and fixing a developer image on the conveyed medium;
(D) a second drive unit for conveying the medium in the fixing device;
(E) a slack detection device including a slack detection element for detecting slack of a medium formed between the image forming unit and the fixing device;
(F) an adjustment unit that adjusts the detection position of the slack detection element when the slack detection element detects slack of the medium by moving the slack detection device;
(G) a slack amount control unit that changes the rotational speed of one of the first and second drive units based on the slack of the medium detected by the slack detection element;
(H) the slack detecting element detects slack of the medium by contacting the medium;
(I) The adjustment unit moves the slack detection device in a direction in which the slack is formed in the medium, so that the position where the slack detection element contacts the medium is approximately the same as the direction in which the slack is formed in the medium. An image forming apparatus , wherein the detection position of the slack detection element is adjusted by moving in a parallel direction . The slack detecting element is in contact with a medium, and detects slack of the medium by displacing the medium in a direction substantially perpendicular to the transport direction of the medium and the moving direction of the slack detecting device according to the slack of the medium. Item 2. The image forming apparatus according to Item 1 . Before Kiyurumi detection element is in contact with the medium, and displaced in accordance with the slack of the medium, the image forming apparatus according to claim 1 for generating a sensor output of the detection signal generating unit in accordance with the displacement. The slack detecting device, the slack detection element, and an image forming apparatus according to claim 1 or 3 comprising a detection element holding member for holding the該弛viewed detection element. (A) having a fixing device holding member for holding the fixing device;
The image forming apparatus according to claim 3 , wherein the detection signal generation unit is disposed on the fixing device holding member. (A) an image forming unit for forming a developer image and transferring it to a medium;
(B) a first drive unit for conveying a medium in the image forming unit;
(C) a fixing device disposed on the downstream side of the image forming unit in the conveyance direction of the medium and fixing a developer image on the conveyed medium;
(D) a second drive unit for conveying the medium in the fixing device;
(E) a slack detection device including a slack detection element for detecting slack of a medium formed between the image forming unit and the fixing device;
(F) an adjustment unit that adjusts a detection position of the slack detection element when the slack detection element detects slack of the medium;
(G) a slack amount control unit that changes the rotational speed of one of the first and second drive units based on the slack of the medium detected by the slack detection element;
(H) having a fixing device holding member for holding the fixing device;
(I) The fixing device holding member is provided with a signal generating device including a detection signal generating unit,
(J) The slack detection element is in contact with the medium and is displaced according to the slack of the medium, and generates a sensor output of the detection signal generation unit according to the displacement,
(K) The image forming apparatus, wherein the looseness detecting device and the signal generating device are connected by attaching the fixing device to a fixing device holding member. (A) The detection signal generating unit includes a light emitting unit and a light receiving unit,
(B) The slack detection element is swingably disposed with respect to the detection element holding member, and in accordance with the swing, the slack detection element shields the detection signal generator, and the detection signal generator does not shield. The image forming apparatus according to claim 5 , further comprising a shielding portion that takes a position. 8. The image forming apparatus according to claim 7 , wherein a line extending in a direction of the slack detection device through an intermediate between a light emitting portion and a light receiving portion in the detection signal generation portion is parallel to a moving direction of the slack detection device. . (A) a slack detection device provided with a slack detection element that is disposed in contact with the medium in a portion where slack is formed in the medium conveyed through the conveyance path and detects slack of the medium;
(B) a first drive unit disposed on the upstream side of a portion where the medium and the slack detection element contact in the medium transport direction, and transports the medium;
(C) a second drive unit that is disposed on the downstream side of a portion where the medium and the slack detection element contact in the medium conveyance direction, and conveys the medium;
(D) a slack amount control unit that changes the rotation speed of one of the first and second drive units based on the slack of the medium detected by the slack detection element;
(E) By moving the slack detection device in a direction in which slack is formed in the medium, the position where the slack detection element contacts the medium is moved in a direction substantially parallel to the direction in which slack is formed in the medium. And an adjustment unit that adjusts a detection position of the looseness detection element when the looseness detection device detects looseness of the medium. The slack detecting element is in contact with a medium, and detects slack of the medium by displacing the medium in a direction substantially perpendicular to the transport direction of the medium and the moving direction of the slack detecting device according to the slack of the medium. Item 10. The image forming apparatus according to Item 9 .

Images