JP2008111888A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve such a problem that defective images and poor cleaning occur due to rise of temperature in an image forming part resulting in sticking of toner to a developing part and a cleaner part composing the image forming part since a sheet heated by a fixing part passes through a conveying path again since a recording material on which an image has been recorded in a both-side recording mode is turned upside down and pulled into a both-side conveying part just after being ejected. <P>SOLUTION: During the both-side recording mode, forward/backward rotational drive is repeated a plurality of times in accordance with the number of continuously image formation sheets and an environmental condition such as an apparatus temperature to thereby cool the sheet outside the apparatus, then, the defective images and the poor cleaning resulting from the rise of temperature in the apparatus due to refeeding of the paper from the both-side conveying part are prevented. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  In the present invention, images can be formed on the front and back of a recording material. In particular, after a recording material having an image formed on the front surface is reversed, the recording material is conveyed again to the image forming unit by a double-sided conveyance unit to form an image on the back side. The present invention relates to an image forming apparatus.

  Conventionally, in an image forming apparatus, a recording material on which an image is formed on the front surface is reversed by the image forming unit and conveyed again to the image forming unit, and an image is formed on the back surface of the recording material to perform double-sided recording. There is something.

  In recent years, there is an increasing demand for recording on both sides of a recording material for the purpose of environmental protection and cost reduction, and there is an increasing demand for a compact, low-cost image forming apparatus with a double-sided recording mechanism.

JP2003-241458

  In a small-sized and low-cost image forming apparatus such as a laser beam printer, naturally, a low-cost double-sided recording mechanism is indispensable, and as such a double-sided recording mechanism, the recording material discharged after the recording is finished is stacked. There is a configuration in which the reversing operation of double-sided recording is performed using a section (discharge tray). That is, when performing double-sided recording, a part of the recording material recorded on one side is discharged to the discharge tray, and then this recording material is conveyed to the double-sided conveyance unit.

  In such a configuration, it is necessary to drive at least one roller upstream of the discharge tray in the forward / reverse direction. When the recording material is conveyed toward the discharge tray, the discharge roller is driven in the forward direction to reverse the recording material. Therefore, in order to convey the recording material partially discharged to the discharge tray to the double-sided conveyance unit, the roller must be driven in reverse.

  In addition to the main drive, there is a configuration that uses a stepping motor to perform forward / reverse drive of the roller, but in order to perform the above operation at a low cost, a configuration using a combination of a solenoid, a spring clutch, and a gear train is possible. Used.

  In such a configuration, after the recording material on which recording has been completed is discharged, the recording material is immediately reversed and pulled into the double-sided conveyance unit, so that the recording material heated by the fixing unit passes through the conveyance path again, and the image forming unit rises. As a result, the toner is fixed at the developing unit and the cleaner unit constituting the image forming unit, and problems such as image defects and cleaning defects occur.

  The present invention has been made to solve the above-described problems, and its purpose is to suppress the temperature rise in the apparatus during double-sided image formation, and to prevent the occurrence of image defects and cleaning defects due to the temperature increase in the apparatus. It is an object of the present invention to provide an image device that can be prevented.

  According to the first aspect of the present invention, there is provided a fixing device for fixing an image on a recording material on which an image is formed by an image forming means with heat, and a single-sided recording mode for conveying a recording material on which a surface image is fixed by the fixing device to a discharge portion. And a double-sided recording mode in which the recording material image-formed on the front side is conveyed from the discharge unit to the double-sided conveyance unit, and after the image is formed on the back surface, the recording material is conveyed to the discharge unit. A pair of discharge reversing rollers that can be driven forward to convey the image-formed recording material to the discharge unit and can be reversely driven to reversely convey the recording material to the double-sided conveyance unit in the double-sided recording mode. Before the recording material image-formed on the surface in the double-sided recording mode is conveyed to the double-sided conveyance unit, the discharge reversing roller pair is clamped and the forward / reverse driving of the discharge reversing roller pair is performed. Repeat multiple times Image forming apparatus characterized by.

  According to a second aspect of the present invention, in the image forming apparatus of the first aspect, the operation of repeating the forward / reverse driving of the pair of discharge reverse rollers a plurality of times is performed when the number of continuous image formations of the recording material exceeds a predetermined number. It is characterized by being.

  According to a third aspect of the present invention, in the image forming apparatus according to the first aspect, in the operation of repeating the forward / reverse driving of the pair of discharge reversing rollers a plurality of times, the temperature detected by the temperature detecting means provided in the apparatus has a predetermined temperature. It is performed when it exceeds.

  According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first, second, and third aspects, when the forward / reverse driving of the discharge reverse roller pair is repeated a plurality of times, the heating temperature of the fixing device is set at the time of fixing. It is characterized by lowering.

  According to the present invention, even in an image forming apparatus in which a recording material that has been recorded on the front surface is immediately drawn into a double-sided conveyance path by double-sided conveyance of a low-cost configuration that does not use a separate drive such as a stepping motor, The recording material is cooled outside by repeating the forward / reverse rotation of the discharge reversing roller for a predetermined time or until the internal temperature drops to the predetermined temperature according to the predetermined environmental conditions such as the internal temperature, and the paper is fed again from the double-sided conveyance path. Therefore, it is possible to provide an image forming apparatus excellent in image quality, in which the temperature inside the apparatus is not raised to cause image defects or cleaning defects.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  Next, a printer will be exemplified and described as the image forming apparatus according to the first embodiment of the present invention.

  {Overall Configuration} FIG. 1 is a schematic explanatory diagram of a printer according to the first embodiment. In FIG. 1, 101 is a photosensitive drum as an image carrier, 102 is a light source that emits laser light, 103 is a rotating polygon mirror that is rotated by a scanner motor 104, and 105 is selectively irradiated from the light source 102, This is a laser beam for scanning the drum 101.

  Reference numeral 106 denotes a charging roller for uniformly charging the surface of the photosensitive drum 101, and 107 denotes a developing unit for developing the electrostatic latent image formed on the photosensitive drum 101 with toner. Reference numeral 108 denotes a transfer roller for transferring the toner image developed by the developing device 107 to a recording material, and 109 denotes a fixing device for fixing the toner image transferred to the recording material by heat.

  110 rotates once to feed the recording material from the cassette having a function of identifying the size of the recording material, and feeds the recording material to the conveyance path. 111 and 112 convey the recording material fed from the cassette. It is a conveyance roller.

  113 is a pre-feed sensor for detecting the leading edge and the trailing edge of the fed recording material, 114 is a pre-transfer roller for feeding the conveyed recording material to the photosensitive drum 101, and 115 is for the fed recording material. This is a top sensor for synchronizing the image formation on the photosensitive drum 101 and the conveyance of the recording material and measuring the length of the fed recording material in the conveyance direction.

  116 is a discharge sensor for detecting the presence or absence of the recording material after fixing, 117 is a discharge roller for conveying the recording material after fixing to the discharge tray 118, and 119 is a discharge tray for recording material conveyed from the discharge roller 117 A discharge reversing roller that rotates forward to discharge to 118 and reverses when the recording material is fed to the double-sided conveyance unit, 120 is a double-sided introduction roller for feeding the recording material sent from the discharge reversing roller 119 to the double-sided conveyance unit, 121, 122, and 123 are double-sided conveyance rollers in the double-sided conveyance unit, and 124 is a refeed sensor for detecting the recording material conveyance state of the double-sided conveyance unit.

  Reference numeral 125 denotes a toner cartridge 125 in which the photosensitive drum 101, the charging roller 106, and the developing device 107 are integrated and detachable from the main body of the image forming apparatus. Although not shown, a cartridge door (not shown) is provided when the toner cartridge 125 is attached to and detached from the image forming apparatus main body.

  {Drive Control Configuration} Next, the configuration of the control system for controlling the drive of the printer having the above configuration will be described. FIG. 2 is a block diagram of the drive control configuration. In FIG. 2, reference numeral 201 denotes image code data sent from an external device such as a host computer (not shown), which is developed into bit data necessary for printer recording, and printer internal information. It is a printer controller for reading and displaying it.

  A printer engine control unit 202 controls operation of each unit of the printer engine in accordance with an instruction from the printer controller 201 and notifies the printer controller 201 of printer internal information. A high-voltage control unit 203 performs high-voltage output control in each process such as charging, development, and transfer in accordance with instructions from the printer engine control unit 202.

  An optical system control unit 204 controls driving / stopping of the scanner motor 104 and lighting of the laser beam in accordance with instructions from the engine control unit 202. A fixing control unit 205 drives / stops energization of the fixing heater in accordance with an instruction from the printer engine control unit 202.

  206 is a sensor input unit that detects the presence or absence of the recording material of the pre-feed sensor 113, the top sensor 115, the discharge sensor 116, and the re-feed sensor 124 and notifies the engine control unit 202, and 207 is an instruction from the printer engine control unit 202. Accordingly, in the recording material conveyance driving unit for driving / stopping the motor / roller or the like for conveying the recording material, the feeding roller 110, the conveyance rollers 111 and 112, the pre-transfer roller 114, the fixing roller 109, and the discharge roller in FIG. 117, driving / stopping the double-side introduction roller 120, and normal / reverse driving of the discharge reversing roller 119, and driving of the double-sided conveying rollers 121 to 123.

  {Double-Sided Recording Operation} Next, the engine control unit 202 will be described with reference to FIG. FIG. 3 is a flowchart of a control method when the engine control unit 202 performs double-sided recording in the present embodiment.

  In step 301, the engine control unit 202 rotates the feeding roller 110 once to feed the recording material to the conveyance rollers 111 and 112, and conveys the recording material until the pre-feed sensor 113 detects the leading edge of the recording material.

  At the same time, the electrophotographic process is initialized (started up) so that the surface of the photosensitive drum 101 has a desired potential, and the rotary polygon mirror 103 is driven to a predetermined rotational speed. Further, pre-recording control is performed to start up the fixing device 109 so as to reach a predetermined temperature.

  In step 302, if all the conditions are confirmed that the rotational speed of the rotary polygon mirror 113 has reached the desired rotational speed, the fixing device 109 has reached the desired temperature, and the initialization of the photosensitive drum 101 has been completed, The feeding roller 110 is rotated once to feed the recording material to the conveying rollers 111 and 112, and the recording material is conveyed until the pre-feed sensor 113 detects the leading edge of the recording material.

  When the leading edge of the recording material is detected by the pre-feed sensor 113, the engine control unit 202 turns on an electromagnetic clutch (not shown) for a predetermined time until the leading edge of the recording material hits the pre-transfer roller 114 and the skew feeding of the recording material is corrected. The rotation of the pre-transfer roller 114 is stopped.

  In step 303, the engine control unit 202 turns off the electromagnetic clutch, starts rotation of the pre-transfer roller 114, and resumes conveyance of the recording material toward the photosensitive drum 101. Then, when the top sensor 115 detects the leading edge of the recording material that has been transported again, the engine control unit 202 outputs a vertical synchronization signal to the printer controller 201 and performs recording on the recording material in synchronization with the leading edge.

  Thereafter, the toner image latently formed on the recording material by the fixing device 109 is thermally welded onto the recording material and conveyed to the discharge roller 117.

  In step 304, the process waits until the leading edge of the conveyed recording material is detected by the discharge sensor 116. When the discharge sensor 116 detects the leading edge of the recording material, in step 305, the engine control unit 202 turns off a discharge reversing solenoid (not shown). The forward rotation drive of the discharge reverse roller 119 is performed. The discharge reversing roller 119 driven in the forward direction conveys the conveyed recording material in the direction of the discharge tray 118.

  In step 306, the process waits until the discharge sensor 116 detects the rear end of the recording material. When the discharge sensor 116 detects the rear end of the recording material, in step 307, the rear end of the recording material passes through the discharge roller 117 and passes through the discharge reverse roller 119. Wait for a predetermined time until it reaches 10mm (for example).

  In step 308, the number of recording materials conveyed to the engine control unit 20 is counted up, and it is determined whether or not a predetermined number of sheets have been conveyed. For example, the internal temperature does not increase so much even if the recording materials are conveyed on both sides up to 20 sheets continuously. In this embodiment, it is determined whether or not the number of conveyed recording materials is 20 or more. If the number of conveyed recording materials is 20 or more, the process proceeds to step 309. If the number of conveyed recording materials is less than 20, the process proceeds to step 316.

  In step 309, the engine control unit 202 stops driving the fixing heater. In step 310, the engine control unit 202 turns on a discharge reversing solenoid (not shown) and switches the driving of the discharge reversing roller 119 from the normal rotation driving to the reverse rotation driving. The discharge reversing roller 119 driven in the reverse direction starts the reversal conveyance with the recording material directed to the double-side introduction roller 120.

In step 311, the waiting time is 0.3 sec in this embodiment, which is a predetermined time during which the leading edge of the recording material that has started reverse conveyance in step 310 does not reach the double-sided introduction roller 120.
In step 312, the engine control unit 202 turns off the discharge reversing solenoid, switches the driving of the discharge reversing roller 119 from the reverse rotation driving to the normal rotation driving, and conveys the recording material toward the discharge tray 118 again.

  In step 313, the process waits for the same predetermined time as in step 311. In step 314, the number of repetitions of a series of operations from step 310 to step 313 is counted up, and it is determined whether or not the number is a predetermined number or more. In this embodiment, it is 10 times, and if less than 10 times, the process returns to step 310, and if 10 times is reached, the process proceeds to step 315.

  In this embodiment, the steps 310 and 312 are the same predetermined time of 0.3 sec, so that the total is 0.6 sec. The recording material is largely discharged for 6.0 sec in 10 repetitions, and the discharge reverse roller on the discharge tray 118 is discharged. 119 holds the trailing edge of the recording material.

  As a result, the recording material discharged and held on the discharge tray 118 is cooled. In this embodiment, the recording material cooling time is 0.6 sec × 10 times = 6.0 sec for 20 or more continuous recording material conveyances, but 0.6 sec × 20 times = 12.0 sec for 40 or more sheets, and 0.6 sec × 40 for 80 or more sheets. The recording material wait time may be changed according to the number of sheets, such as times = 24.0 sec.

  In step 315, the engine control unit 202 resumes the fixing heater driving stopped in step 309.

In step 316, the engine control unit 202 turns on the discharge reversing solenoid to start the reverse rotation driving of the discharge reversing roller 119, and feeds the recording material toward the duplex conveying unit.
Step 317 waits until the refeed sensor 124 detects the leading edge of the recording material sent to the double-sided conveyance unit. In step 318, the double-sided conveyance unit 208 is informed that the refeed sensor 124 has detected the leading edge of the recording material. Then, the engine control unit 202 issues a feeding instruction to the double-sided conveyance control unit 202.

  Receiving this feeding instruction, the double-sided conveyance control unit 208 continues to drive the double-sided conveyance rollers 121 to 123 in the double-sided conveyance unit as it is, and conveys the recording material in the double-sided conveyance unit to the pre-feed sensor 113.

  When the leading edge of the recording material is detected by the pre-feed sensor 113, the engine control unit 202 turns on an electromagnetic clutch (not shown) for a predetermined time until the leading edge of the recording material hits the pre-transfer roller 114 and the skew feeding of the recording material is corrected. The rotation of the pre-transfer roller 114 is stopped.

  In step 319, the engine control unit 202 turns off the electromagnetic clutch, starts rotation of the pre-transfer roller 114, and resumes conveyance of the recording material toward the photosensitive drum 101. When the top sensor 115 detects the leading edge of the recording material, it outputs a vertical synchronizing signal to the printer controller 201 and performs recording on the recording material by synchronizing the leading edge.

  In step 320, the weight of the conveyed recording material is waited until it is detected by the discharge sensor 116. When the discharge sensor 116 detects the leading edge of the recording material, the engine control unit 202 turns off a discharge reversing solenoid (not shown) in step 321. The forward rotation drive of the discharge reverse roller 119 is performed. The discharge reversing roller 119 driven in the forward direction conveys the conveyed recording material in the direction of the discharge tray 118.

  In step 322, the process waits until the discharge sensor 116 detects the trailing edge of the recording material. When the discharge sensor 116 detects the trailing edge of the recording material, the recording material trailing edge passes through the discharge reverse roller 119 and records on the discharge tray 118 in step 323. Wait for a predetermined time when the material is completely discharged.

  In step 324, the engine control unit 202 determines whether or not a next print request instruction is received from the printer controller 201. If there is no next print request, the process proceeds to step 325, and if the next print request is received, the process proceeds to step 202. Start printing.

  In step 325, contrary to step 301, the post-recording control of the lowering of the surface potential of the photosensitive drum 101, the stop of the rotary polygon mirror 103, and the lowering of the fixing device 109 is performed, and the printing operation is finished.

  The prefeed sensor 113, the top sensor 115, the discharge sensor 116, and the refeed sensor 124 are on the recording material conveyance path of the printer that is the image forming apparatus described in the present embodiment. Always make sure.

  For example, if the pre-feed sensor 113 does not detect the leading edge of the recording material within a predetermined time from the start of the feeding operation, the pre-feed sensor 113 determines that the recording material has a delay jam, and after detecting the leading edge of the recording material, When the end is not detected, it is determined as a stay jam.

  Such a jam determination is performed not only by the pre-feed sensor 113 but also by all of the top sensor 115, the discharge sensor 116, and the refeed sensor 124.

  The engine control unit 202 that has detected a jam immediately interrupts all operations and makes a transition to a jam state even during a recording operation. In order to release this jammed state, it is necessary to open and close the cartridge door that opens and closes when a toner cartridge (not shown) is attached or detached.

  The engine control unit 202 that detects opening / closing of the cartridge door cancels the jammed state, cleans the photosensitive drum 101, and performs initial driving to initialize the electrophotographic process. At the same time, each roller is driven to discharge the staying recording material in the apparatus to the outside of the apparatus.

  As described above, according to the number of double-sided prints, the recording material that has been recorded on the front surface is repeatedly forward / reversely rotated by the discharge reverse roller and held on the discharge tray for a predetermined time, and the energization to the fixing heater is stopped during that time. As a result, it is possible to cool the recording material and prevent temperature rise in the apparatus due to double-sided paper re-feeding.

  Next, another embodiment of the present invention will be described.

  {Overall Configuration} FIG. 4 is a schematic explanatory diagram of a printer according to the second embodiment. 4 is different from the first embodiment shown in FIG. 1 in that an in-machine temperature sensor 126 is provided on the recording material conveyance path. The rest of the configuration is the same as in FIG.

  {Drive Control Configuration} The drive control configuration of the printer according to the second embodiment is the same as that of the first embodiment shown in FIG.

  {Double-Sided Recording Operation} Next, the engine control unit 202 will be described with reference to FIG. FIG. 5 is a flowchart of a control method when the engine control unit 202 performs double-sided recording in the second embodiment.

  From step 501 to step 507, the same control as in the first embodiment shown in steps 301 to 307 in FIG. 3 is performed.

  In step 508, the engine control unit 202 determines whether or not the temperature of the recording material conveyance path is equal to or higher than a predetermined temperature by the in-machine temperature sensor 126. In this embodiment, it is determined whether the in-machine temperature is 45 ° C. or higher. If the in-machine temperature is 45 ° C. or higher, the process proceeds to step 509, and if the in-machine temperature is less than 45 ° C., the process proceeds to step 516.

  From step 509 to step 513, the recording material whose recording has been completed on the surface is controlled to be cooled and held on the discharge tray 118 as in the first embodiment shown in steps 309 to 313 of FIG.

  In step 514, it is determined by the in-machine temperature sensor 126 whether or not the temperature of the recording material conveyance path has become lower than a predetermined temperature. In this embodiment, it is determined whether the in-machine temperature is less than 35 ° C. If the in-machine temperature is less than 35 ° C., the process proceeds to step 515, and if the in-machine temperature is 35 ° C. or more, the process returns to step 510.

  The determination in step 514 may be performed a predetermined number of times by repeating a series of operations in steps 510 to 513 as in the first embodiment shown in step 314 in FIG.

  Steps 515 to 525 of the shift are the same control as in the first embodiment shown in steps 315 to 325 of FIG.

  As described above, the energization of the fixing heater is stopped according to the temperature inside the apparatus, and the recording material on the surface is recorded until the inside temperature of the apparatus drops to a predetermined temperature on the discharge tray by repeating the forward / reverse rotation of the discharge reverse roller. By holding, it is possible to cool the recording material and prevent the temperature rise in the apparatus due to refeeding in the double-sided image forming mode.

FIG. 2 is a schematic explanatory diagram of a printer according to the first embodiment. It is a block diagram of a drive control configuration. It is a flowchart of the control method in case the engine control part in 1st Embodiment performs double-sided recording. FIG. 10 is a schematic explanatory diagram of a printer according to a second embodiment. It is a flowchart of the control method in case the engine control part in 2nd Embodiment performs double-sided recording.

Explanation of symbols

101 Photosensitive drum
102 Semiconductor laser
103 rotating polygon mirror
104 Scanner motor
105 Laser beam
106 Charging roller
107 Developer
108 Transfer roller
109 Fuser
110 Cassette feed roller
111, 112 Transport roller
113 Pre-feed sensor
114 Pre-transfer roller
115 Top sensor
116 Discharge sensor
117 Discharge roller
118 Output tray
119 Discharge reversing roller
120 Double-sided introduction roller
121, 122, 123 Double-sided transport roller
124 Refeed sensor
125 Toner cartridge
126 In-machine temperature sensor
201 Printer controller
202 Engine control unit
203 High pressure controller
204 Optical system controller
205 Fixing controller
206 Sensor input section
207 Recording material conveyance control unit

Claims (4)

A fixing device for fixing an image on a recording material image-formed by image forming means by heat; a one-sided recording mode for conveying a recording material on which a surface image is fixed by the fixing device to a discharge portion; and image formation on the surface In an image forming apparatus comprising a double-sided recording mode in which the recording material is conveyed from the discharge unit to the double-sided conveyance unit, and after the image is formed on the back surface, the recording material is conveyed to the discharge unit.
A discharge reversing roller that can be driven forward to convey the image-formed recording material to the discharge unit and can be reversely driven to reversely convey the recording material to the double-sided conveyance unit in the double-sided recording mode. Have a pair,
Before the recording material with the image formed on the surface in the double-sided recording mode is conveyed to the double-sided conveyance unit, the recording material is sandwiched between the discharge reversing roller pair, and the forward / reverse driving of the discharge reversing roller pair is repeated a plurality of times. An image forming apparatus. 2. The image forming apparatus according to claim 1, wherein the operation of repeating the forward / reverse driving of the discharge reversing roller pair a plurality of times is performed when the number of continuous image formations of the recording material exceeds a predetermined number. . The operation of repeating the forward / reverse driving of the discharge reversing roller pair a plurality of times is performed when the temperature detected by the temperature detecting means provided in the machine exceeds a predetermined temperature. Image forming apparatus. 4. The image formation according to claim 1, wherein when the forward / reverse driving of the pair of discharge reverse rollers is repeated a plurality of times, the heating temperature of the fixing device is lower than that during fixing. apparatus.

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