JP5455658B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, a printer, and a multifunction machine that integrates these functions. More specifically, the present invention relates to an image forming apparatus such as an electrophotographic system provided with a transfer conveyance belt for carrying and conveying a recording material.

  An image forming apparatus based on a transfer / conveyance belt is known in order to meet the expansion of specifications for thin paper and thick paper based on recent market needs (Patent Document 1). This apparatus electrostatically transfers an electrostatic toner image formed on the surface of a photosensitive drum, which is an image carrier, onto a recording material carried on a transfer conveyance belt by the action of a transfer charger. The recording material onto which the unfixed toner image has been transferred is separated from the transfer conveyance belt by the electrostatic adsorption force being attenuated by being neutralized by a separation corona charger at the downstream side of the transfer conveyance belt in the conveyance direction. The recording material separated from the transfer / conveying belt is heated and pressed by the fixing unit to fix the toner image on the recording material, and is discharged outside the apparatus.

  Patent Document 2 proposes an apparatus for transferring and fixing a toner image onto a recording material at the transfer and simultaneous fixing position. In this apparatus, before the leading edge of the image on the intermediate transfer body reaches the simultaneous transfer and fixing position, the recording material is fed from the paper feed cassette, and the recording material is heated, pressurized, or both. Pass the pretreatment means. Then, the recording material moves so that the leading edge of the image on the intermediate transfer member and the leading edge of the recording material are aligned, and is inserted into the simultaneous transfer fixing means, and the toner image is transferred and fixed onto the recording material simultaneously.

  In Patent Document 3, after an unfixed toner image formed on an image carrier is transferred to a recording material, an unfixed toner image on the recording material is placed on the upstream side of a roller pair which is a main heating / pressurizing unit. There has been proposed an image forming apparatus provided with preheating means for preheating.

  Patent Document 4 proposes an image forming apparatus including an intermediate transfer belt and a recording material conveyance belt. In this apparatus, a first toner image is transferred onto an intermediate transfer belt at a transfer portion formed by a photosensitive member and a transfer roller, and is rotated as it is. At this time, the fixing roller and the cleaning roller are not in contact with the intermediate transfer belt. Next, when the second toner image is formed on the photoreceptor, the front and back surfaces of the recording material are aligned with the transfer nip portion in synchronization with the first toner image already transferred onto the intermediate transfer belt. Each is transcribed. Thereafter, the recording material is conveyed to the fixing roller portion. At this time, the fixing roller and the cleaning roller are in contact with the intermediate transfer belt, and the second toner image and the first toner image between the fixing roller and the recording material are fixed on the recording material.

JP 2001-335178 A Japanese Patent Laid-Open No. 05-341660 JP 2000-321922 A JP 2002-268404 A

The image forming apparatus based on the transfer / conveying belt system disclosed in Patent Document 1 has abnormal discharge (peeling discharge) when the recording material is separated and conveyed from the transfer / conveying belt, particularly when the recording material is thin paper (basis weight is about 70 g / m ² or less). ) Tends to occur. The image defect is a phenomenon in which, for example, when a halftone image is output, a bird footprint-like discharge trace or a polka-dot discharge trace appears on the image. This will be described with reference to FIG. Reference numeral 106 denotes an endless transfer / conveying belt, which is stretched around a plurality of belt suspension rollers including the separation roller 111 and is circulated and moved in the direction of the arrow. The recording material P is carried and conveyed on the upper surface of the belt 106, and receives the transfer of the toner image on the image carrier in the process of passing through a transfer portion (not shown). The recording material P that has passed through the transfer portion is continuously conveyed by the belt 106 and reaches the separation portion A, which is a belt winding portion of the separation roller 111, and is separated from the belt 106 by curvature and introduced into an image fixing means (not shown). Go. In this case, if the recording material P is a thin paper with low rigidity (weak waist), when separating the curvature from the belt 106 in the separation portion A, the recording material P follows the curvature of the belt 106 wound around the separation roller 111. As shown by the solid line, it is separated after taking the form of winding once. That is, the separation angle θ1 formed between the belt 106 and the recording material P when the recording material P is separated is larger than the separation angle θ2 of paper having a large basis weight and relatively high rigidity ((b) in FIG. 8). growing. For this reason, particularly in the case of thin paper, an image defect due to peeling discharge is likely to occur when separating from the belt 106.

  Further, the charge held on the recording material when the recording material reaches the separation portion from the belt 106 due to the environmental conditions in which the image forming device is placed, the durability of the image forming device, the type of the recording material P, and the like. There are various quantities and polarities. Accordingly, the recording material is neutralized by a neutralizing means such as a separation corona charger so as to suppress the abnormal discharge that causes the above-mentioned image defect (bird footprint / polka dot shape) and so as not to disturb the electrostatic toner image. It is difficult to do.

  With respect to the above problem, the technique disclosed in Patent Document 3 relates to a preheating unit in a fixing device after a recording material onto which an unfixed toner image is transferred from a toner image carrier is separated and conveyed from the transfer device. It is a technology, and the effect on the above problems cannot be expected.

  Although the technique disclosed in Patent Document 2 and the technique disclosed in Patent Document 4 have an effect on the above problems, they have the following adverse effects. That is, in the technique disclosed in Patent Document 2, the recording material is preheated on the upstream side of the simultaneous fixing portion of the toner image onto the recording material. The resistance value of becomes higher. As a result, the secondary transfer bias for transferring the toner image to the recording material is set to a high value, and an image defect due to abnormal discharge on the upstream side of the secondary transfer portion or the recording material at the secondary transfer portion Separation defects that electrostatically adhere to the intermediate transfer member are likely to occur. Further, in the system in which the secondary transfer unit to fixing are integrally formed as disclosed in Patent Document 4, a shock to the fixing unit when a paper, particularly a thick paper, enters or exits, records a toner image. This affects the transfer portion that transfers to the material and the image carrier that forms the electrostatic toner image. For this reason, image defects are likely to occur. Further, it is easily affected by a difference in speed between the transfer portion and the fixing portion, and is liable to cause an adverse effect such as image shift or scattering.

  The present invention has been made in view of the above-described circumstances. The purpose of the image forming apparatus is provided with a transfer conveying means that can effectively suppress image defects that are likely to occur in the upstream and downstream of the toner image transfer portion to the recording material and can stably convey from thin paper to thick paper. Is to provide.

In order to achieve the above object, a typical configuration of an image forming apparatus according to the present invention includes a rotatable image carrier on which a toner image is formed and a plurality of belt suspension members including a recording material separation roller. It is stretched and circulated, carries the recording material, conveys it to the image transfer portion of the image carrier, and transfers the toner image to the recording material, on the downstream side of the image transfer portion in the recording material conveyance direction An endless transfer conveyance belt for separating the curvature of the recording material at a separation portion which is a belt winding portion of the separation roller; and a fixing device for fixing a toner image of the recording material separated from the transfer conveyance belt ; in a period from before Symbol image transfer portion of the separation unit, and the recording material carrying surface of the transfer conveyor belt is disposed in a non-contact, by irradiating an electromagnetic wave to a toner image carried on a recording material a toner image Is assumed to be attached to the recording material. An image forming apparatus comprising a wave emitting means, wherein the electromagnetic wave irradiating means and acquisition means for acquiring the rigidity of the recording material, when obtained result is rigid below a predetermined by the acquisition unit to be fed to the apparatus And a control means for operating the device .

According to the present invention, it is possible to effectively suppress image defects due to abnormal discharge that is likely to occur when the recording material is separated from the transfer conveyance belt.

Schematic diagram of an image forming apparatus in a reference example (A) is a block diagram of a main control system, (b) is a model diagram for explaining a belt deviation regulating member. Control flow chart of electromagnetic wave irradiation means Schematic diagram of an image forming apparatus in Embodiment 1 . (A) is a block diagram of a main control system, (b) is a schematic diagram of a stiffness detecting means for detecting the stiffness of a recording material using ultrasonic waves as a recording material information detecting means, and (c) is a stiffness characteristic value. Attenuation rate correlation diagram Control flow chart of electromagnetic wave irradiation means and second fixing device Schematic diagram of an image forming apparatus in Embodiment 2 . Illustration of separation angle for recording material curvature separation

  Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.

[Reference example]
(1) Overall Schematic Description of Example Image Forming Apparatus FIG. 1 is a schematic diagram of an image forming apparatus in this reference example . FIG. 2A is a block diagram of a main control system of the image forming apparatus of this reference example . This image forming apparatus is an electrophotographic system, a laser exposure system, a transfer conveyance belt type digital image forming apparatus (a copying machine, a printer, a facsimile machine, or a multi-function machine thereof). That is, an image can be formed on a recording material (transfer material) P based on an electrical image information signal input to a control circuit unit (control means) 100 from a host device 200 such as a document reading device, a personal computer, a facsimile, or a word processor. An electrophotographic image forming apparatus that can be used. The control circuit unit (control unit) 100 includes a CPU (arithmetic unit), ROM, RAM, and the like, and exchanges various electrical information with the operation unit 300 and the host device 200. Further, the control circuit unit 100 comprehensively controls the image forming operation of the image forming apparatus in accordance with a predetermined control program and a reference table.

  This image forming apparatus has a rotatable drum type electrophotographic photosensitive member (hereinafter referred to as a drum) 1 as an image carrier on which a toner image is formed. The drum 1 is rotationally driven at a predetermined speed by a drive source M in the clockwise direction of the arrow R1. Around the drum 1, a primary charger 2, an exposure device 3, a developing device 4, a transfer charger 31, and a drum cleaner 5 are disposed as process means acting on the drum 1 along the drum rotation direction.

The primary charger 2 is a charging unit that uniformly charges the surface of the drum 1 to a predetermined polarity / potential. In this reference example , a charging bias having a predetermined polarity / potential is applied from the power supply unit S2. A corona discharger that is a contact charger is used. As the primary charger 2, a contact charger using a conductive charging member such as a charging roller, a charging brush, or a charging blade can be used.

  The exposure device 3 is an exposure unit that forms an electrostatic latent image by exposing the uniformly charged surface of the drum 1 in accordance with image information. In this example, a laser scanner is used. The laser scanner includes a semiconductor laser (light source device), a polygon mirror, an fθ lens, and the like. The semiconductor laser outputs laser light modulated in accordance with an electrical image information signal input from the host device 200 to the control circuit unit 100. The laser light emitted from the semiconductor laser is scanned by rotating the polygon mirror, the light beam of the scanning light is changed by the reflecting mirror, and the light is condensed on the bus bar of the drum 1 by the fθ lens and exposed to the drum. An electrostatic latent image corresponding to image information is formed on 1. The electrostatic latent image forming method in this example is an image exposure method in which exposure is performed corresponding to the image information portion.

  The developing device 4 is a developing unit that develops the electrostatic latent image formed on the drum 1 as a toner image. In this example, a developing device of a two-component developing system or a reversal developing system is used. That is, the developing device 4 is filled with a predetermined amount of a two-component developer in which a non-magnetic toner having a negative charging polarity and a magnetic carrier having a positive charging polarity are mixed at a predetermined mixing ratio. Then, the visible toner image is formed by electrostatically transferring the toner to the non-exposed portion of the electrostatic latent image on the drum 1.

The transfer charger 31 is a transfer unit that transfers the toner image on the drum 1 to the recording material P. In this reference example , a transfer roller is used. The transfer roller 31 is a conductive roller (charging roller). In this reference example , the transfer roller 31 is composed of a conductive core metal having a diameter of 7.0 mm and an EPDM foamed elastic layer having a medium resistance value of 3.5 mm in thickness. The roller hardness (Asker C) is 30 °. The resistance value was measured by rotating the roller at a peripheral speed of 50 mm / sec with respect to the ground (earth surface) under a load of 4.9 N (500 g weight) and applying a voltage of 1000 V to the metal core. It was calculated | required from the relationship of an electric current, and the value was about 10 < ⁶ > ohm (23 degreeC / 50% RH). The transfer charger 31 may be a contact charger using a charging member such as a charging brush or a charging blade. A non-contact charger such as a corona discharger can also be used.

  A transfer / conveying belt (hereinafter referred to as a belt) 10 is disposed below the drum 1. The belt 10 is an endless belt having flexibility, and is suspended between a driving roller 32 and a recording material separating roller 33 arranged in parallel on the upstream side and the downstream side in the recording material conveyance direction with respect to the drum 1. It is stretched. The transfer roller 31 is arranged inside the belt 10 in parallel with the drum 1, and presses against the lower surface of the drum with the belt portion on the ascending side of the belt 10 sandwiched between the drum 1. A contact portion between the drum 1 and the belt 10 is a transfer portion (image transfer portion, transfer nip portion) 7. When the driving roller 32 is driven by the driving source M, the belt 10 is circulated and moved in the counterclockwise direction indicated by arrow R10 at a speed substantially corresponding to the rotational speed of the drum 1. The separation roller 33 and the transfer roller 31 rotate following the movement of the belt 10.

The material of the belt 10 may be either an elastic rubber material such as CR or urethane, or a resin material such as PVdF, PPS, or PI. In this reference example , the belt 10 was made of PI resin having a peripheral length of 440 mm and a thickness of 100 μm and high heat conductivity and low heat capacity. The resistance value of the belt 10 is a surface resistivity of 10 ¹² Ω · cm, a volume resistivity of 10 ¹⁰ Ω · cm (using a probe conforming to the JIS-K6911 method, an applied voltage of 100 V, an application time of 60 sec, and 23 ° C. and 50% RH). . An endless belt is formed by a (seamless) belt having no seam, and is suspended on a driving roller 32 and a driven separation roller 33. As the driving roller 32, a SUS cored bar having an outer diameter of 20 mm and a conductive rubber (volume resistance value: 10 ⁵ Ωcm or less) having a thickness of 1.5 mm was used. The separation roller 33 is supported by a spring pressure mechanism (not shown), and also functions as a tension roller that applies tension to the belt 10 by pressing the belt 10 from the inner peripheral surface side. A SUS roller having an outer diameter of φ19 mm was used as the separation roller 33.

Further, both ends of the belt 10 in the width direction of the belt 10 are restricted in order to restrict the lateral movement of the rollers 31, 32, and 33, which are a plurality of belt suspension members, along the longitudinal direction (roller axial direction) during the circulation movement of the belt 10. Each is provided with a shift regulating member. The width direction of the belt 10 is a belt dimension direction orthogonal to the belt moving direction. In this reference example , the deviation regulating member is a convex edge provided annularly along the circumference of the belt on the inner side of both end portions in the width direction of the belt 10 as shown in the model diagram of FIG. 12. The convex edges 12 on both sides thereof are positioned close to the outside of the roller end surfaces on both ends of the rollers 31, 32, and 33, respectively. When the belt 10 moves toward the one side in the width direction B1, the convex edge 12 on the upstream side of the shifting at that time is received by the roller end surface on that side. Further, when the belt 10 moves toward the other side in the width direction B2, the convex edge 12 on the upstream side of the shifting at that time is received by the roller end surface on that side. As a result, the lateral movement of the rollers 31, 32, and 33 along the longitudinal direction of the belt 10 during circulation is restricted. It is desirable that the convex edge 12 as the shift regulating member has an elastic property, and generally a rubber material such as Si or urethane is used. In this reference example , a urethane single-layer rubber bead member having a width a of 4.0 mm, a thickness b of 1.5 mm, and a JIS A hardness of 60 ° is attached to both end portions in the width direction of the belt 10 with a thermosetting adhesive. Affixed annularly along the circumference of the belt. Thereby, the convex edge 12 is provided as a shift regulating member.

  A feeding cassette 80 in which recording materials P are stacked and stored is disposed below the belt 10. The recording material P in the feeding cassette 80 is separated and fed by driving the feeding roller 81, and is conveyed to the registration roller pair 6 through the conveying path 82. The roller pair 6 is disposed on the upstream side of the driving roller 32 of the belt 10 in the recording material conveyance direction, and is a dies roller driving motor (registration driving motor) M6 (FIG. 2B) controlled by the control circuit unit 100. The rotation is stopped by the rotation. The roller pair 6 temporarily receives the leading end portion of the recording material P conveyed in the conveying path 82 to correct the skew of the recording material P, and sends the recording material P to the upper surface of the belt 10 at a predetermined control timing. To be carried on the belt 10. The recording material P sent out on the belt 10 is carried on the belt 10, conveyed by the circulating movement of the belt 6, and introduced into the transfer unit 7. As the recording material P passes through the transfer portion 7, the toner image on the drum 1 is transferred to the transfer roller 31 by applying a charging bias having a polarity opposite to the normal charging polarity of the toner from the power supply portion S 31. Receive sequentially.

The surface of the drum 1 after the transfer of the toner image to the recording material P reaches the drum cleaner 5 by the subsequent rotation of the drum 1, is cleaned by removing the residual toner, and is repeatedly used for image formation. The cleaner 5 is a cleaning unit that cleans the surface of the drum 1. In this reference example , the cleaner 5 is an apparatus that uses an elastic blade member that abuts against the counter surface of the drum 1 and rubs the drum surface as a cleaning member.

  Further, the recording material P that has passed through the transfer unit 7 is continuously conveyed by the belt 10, passes through the position of the electromagnetic wave irradiation means 20, and reaches the separation unit A that is a belt winding unit of the separation roller 33. The electromagnetic wave irradiation means 20 is a means for presuming an unfixed toner image carried on the recording material P before the recording material P reaches the separation portion A. The electromagnetic wave irradiation means 20 will be described later. The recording material P coming to the separation section A through the position of the electromagnetic wave irradiation means 20 is separated from the belt surface by the curvature in the separation section A, guided to the fixing inlet guide 93 and conveyed to the fixing device 9.

The belt 10 after separating the recording material P reaches the position of the belt cleaner 51 by the subsequent movement of the belt 10. Then, the toner and other foreign matters adhering to the belt surface are removed and cleaned, and the accumulated charge is removed (charge removal) and the recording material P is repeatedly carried and conveyed. In this reference example , the belt cleaner 51 uses a conductive fur brush 51a that is rotationally driven as a cleaning member, and is rotationally driven in contact with the surface of the belt 10 at the belt winding portion of the drive roller 32. As a result, the belt surface is rubbed. The shafts of the conductive fur brush 51a and the drive roller 32 are grounded. Instead of the conductive fur brush 51a, a conductive web (nonwoven fabric) can be used.

The fixing device 9 is a device that fixes an unfixed toner image on the recording material P as a fixed image on the surface of the recording material. In this reference example , the fixing device 9 is a heat roller type device, and includes a fixing roller 91 and an elastic pressure roller 92 as a heating and pressing mechanism. Both rollers 91 and 92 are arranged in parallel and pressed against each other to form a fixing nip portion N, and are driven to rotate in the direction of the arrow. The rollers 91 and 92 are provided with internal heaters H1 and H2, surface temperature detection elements (thermistors) TH1 and TH2, and release agent applicators 94 and 95, respectively. The release agent applicators 94 and 95 have application rollers for applying release agent oil such as dimethyl silicone oil to the surfaces of the rollers 91 and 92, and oil reservoirs, respectively. Each of the heaters H1 and H2 is supplied with electric power from a power source (not shown) and generates heat to heat the rollers 91 and 92 from the inside. Then, the surface temperatures of the rollers 91 and 92 are detected by the surface temperature detection elements TH1 and TH2, and the detected temperature information is input to the control circuit unit 100. The control circuit unit 100 controls the power supplied to the heaters H1 and H2 so that the surface temperature of each of the rollers 91 and 92 is raised to a predetermined fixing temperature based on the input detected temperature information, and is maintained at that temperature. To do. The recording material P introduced into the fixing device 9 enters the fixing nip portion N, is nipped and conveyed, and is heated and pressed to fix the unfixed toner image as a fixed image.

  In the single-sided image forming mode, the recording material P that has exited the fixing device 9 is guided to the discharge conveyance path 83 side by the first flapper 84 that is controlled to the first posture, and a discharge tray (not shown) outside the apparatus. ) Discharged and loaded. In the double-sided image forming mode, the recording material P on which the first side image has been formed that has left the fixing device 9 is guided to the reverse conveyance path 85 side by the first flapper 84 that is controlled to the second posture. The second flapper 87 controlled to the first posture is introduced into the switchback conveyance path 86. Then, the recording material P is introduced into the double-sided conveyance path 88 by the second flapper 87 that is switched back and is controlled to the second posture. Further, the recording material P is again introduced into the conveyance path 82 from the double-side conveyance path 88 and is fed onto the belt 10 through the registration roller pair 6 in a state where the recording material P is reversed. As a result, the toner image is transferred to the second surface of the recording material P by the transfer unit 7. Thereafter, similarly to the image forming operation on the first surface, the recording material P passes through the position of the electromagnetic wave irradiation means 20, the separation unit A, the fixing device 9, and the discharge conveyance path 83 to the discharge tray outside the apparatus as a double-sided image formed product. Discharged and loaded.

(2) Electromagnetic wave irradiation means The electromagnetic wave irradiation means 20 is disposed on the recording material carrying surface side of the belt 10 in a non-contact manner from the transfer portion 7 to the separation portion A of the belt 10, so that recording is performed. This is means for irradiating an electromagnetic wave to an unfixed toner image carried on the material P and attaching the toner image to the recording material. In this reference example , the electromagnetic wave irradiation means 20 includes an infrared lamp 21 and a reflection shade (infrared reflection mirror) 22 for irradiating the belt 10 with infrared rays. A halogen lamp was used as the infrared lamp 21 and was installed 10 mm away from the surface of the recording material P carried and conveyed by the belt 10. As the output of the halogen lamp 21, for example, if the softening point temperature T1 of the toner is 70 ° C., 400 W is sufficient, and in this reference example , the toner having the softening point temperature T1 of 70 ° C. and the 400 W halogen lamp 21 are used. used. An aluminum parabolic mirror was used as the reflecting shade 22 and was installed on top of the halogen lamp 21. At the position where the electromagnetic wave irradiation means 20 is disposed (belt facing position), a temperature detection element (thermistor) 23 for detecting the temperature of the belt 10 is in contact with or not on the belt surface opposite to the electromagnetic wave irradiation means 20 side of the belt 10. Arranged in contact. Then, detected temperature information of the temperature detecting element 23 is input to the control circuit unit 100.

FIG. 3 is a control flowchart of the electromagnetic wave irradiation means 20. When one or more continuous image forming jobs (mono print job or multi print job) are input, the control circuit unit 100 starts an image forming operation. In this reference example , feeding of the recording material P from the feeding cassette 80 is started (step S1). In addition, toner image formation on the drum 1 that has been driven to rotate is started (S2). The recording material P fed from the feeding cassette 80 reaches the registration roller pair 6 and is received by the leading end abutting against the nip portion of the roller pair 6 whose rotation is stopped at that time. Thereby, the skew correction of the recording material P is performed. Then, the motor M6 is turned on at a predetermined control timing (S3). As a result, the rotation of the roller pair 6 is started, and the recording material P is fed to the upper surface of the belt 10 that is circulated and carried on the belt 10. Then, the recording material P is conveyed by the movement of the belt 10 and introduced into the transfer unit 7. As the recording material P passes through the transfer unit 7, the toner image on the drum 1 is transferred by applying a charging bias having a polarity opposite to the normal charging polarity of the toner from the power supply unit S 31 to the transfer roller 31. Receive sequentially (S4).

In the transfer unit 7, the recording material P onto which the toner image is transferred from the drum 1 is conveyed by the subsequent movement of the belt 10 and reaches the position where the electromagnetic wave irradiation means 20 is disposed. In this reference example , the arrival of the leading end portion of the recording material P at the electromagnetic wave irradiation means arrangement position is detected by calculation of the control circuit unit 100 based on the driving ON timing of the motor M6 and the recording material conveyance speed by the belt 10. . Further, the control circuit unit 100 calculates the trailing edge of the recording material by calculation based on the detection timing of arrival of the leading end of the recording material to the position where the electromagnetic wave irradiation means is disposed, the recording material conveyance speed by the belt 10 and the size of the fed recording material. The passage of the electromagnetic wave irradiating means is detected. The size of the recording material is the size in the recording material conveyance direction. Then, the control circuit unit 100 only detects the infrared lamp 21 of the electromagnetic wave irradiation means 20 from the time when the leading end portion of the recording material P reaches the electromagnetic wave irradiation means arrangement position to the passage of the electromagnetic wave irradiation means arrangement position at the rear end. Is turned on (S5, S6).

When the infrared lamp 21 is turned on, in this reference example , the temperature T2 of the toner on the recording material P is slightly higher than the toner softening point T1 (70 ° C.) in the process of passing through the position where the electromagnetic wave irradiation means is disposed. It is heated so that the eye temperature (75 ° C. ≦ T2) is reached. Therefore, the toner image that has not been fixed is assumed to be attached to the recording material P before the recording material P reaches the separation portion A. Then, the recording material P reaches the separation portion A and is separated from the belt surface by the curvature. At this time, since the toner image on the recording material P is assumed by the electromagnetic wave irradiation means 20, the toner image scatters due to the peeling discharge generated at the time of separation as described above even when the recording material P is a thin paper with low rigidity. There is no deterioration such as. That is, the curvature is separated and conveyed from the belt 10 while maintaining high image quality.

  Then, the recording material P separated from the belt 10 is introduced into the fixing device 9 located on the downstream side in the transport direction, receives the main fixing of the toner image, and is discharged out of the image forming apparatus (S7). If there is only one image forming job, the image forming operation is completed. In the case of a plurality of continuous image forming jobs, the above-described image forming operation is repeatedly executed until the last one image is formed (S8 → S1).

Here, regarding the material of the belt 10, in this reference example , the polyimide resin was used as described above. As the material of the belt 10, other elastic rubber materials such as CR and urethane, or resin materials such as PVdF, PPS, and PEEK can be selected. However, if the PI has high heat conductivity and low heat capacity, no cooling means is required. This is relatively convenient.

  In addition, a thermometer 89 such as a radiation thermometer for measuring the temperature of the recording material P on which the first surface image has been formed heated through the fixing device 9 is provided in the middle of the duplex conveying path 88. In the case of the double-sided image formation mode, the control circuit unit 100 is configured to change and control the energization conditions for the electromagnetic wave irradiation means 20 during the second-side image forming operation according to the temperature detected by the thermometer 89. You can also The control for changing the energization condition to the electromagnetic wave irradiation means 20 is control for changing the heating temperature T2 of the toner by the electromagnetic wave irradiation means 20 according to the temperature detected by the thermometer 89.

In this reference example , by arranging the electromagnetic wave irradiation means 20 on the recording material carrying surface side of the belt 10, the toner image on the recording material can be directly heated. Therefore, there is an advantage that power consumption can be reduced compared to a configuration in which a heating member is arranged on the inner peripheral surface side of the belt 10 and an unfixed toner image on the recording material is heated via the belt 10 and the recording material.

The infrared lamp 21 in the electromagnetic wave irradiation unit 20 is turned on when, for example, a plurality of continuous image forming jobs are input, the first recording material P reaches the electromagnetic wave irradiation unit arrangement position when the first recording material P arrives. The lamp 21 starts to light and continues to light. Then, the last recording material P of the continuous image forming job may be operated so as to be turned off after passing through the electromagnetic wave irradiation means arrangement position. However, as in the present reference example, the control method in which the infrared lamp 21 is turned on only when the recording material P passes through the electromagnetic wave irradiation hand placement position is more advantageous. That is, there are advantages in terms of energy saving and in that excessive heat supply to the belt 10 and the electromagnetic wave irradiation means 20 can be suppressed and unnecessary temperature rise in the image forming apparatus can be suppressed.

  By adopting the above-described configuration, the recording material P is stably carried and conveyed by the belt 10, so that the posture of the recording material can be kept constant and the recording material can be stably charged. For this reason, it is possible to effectively suppress the separation failure in which the recording material P is electrostatically adhered to the drum 1 and the image failure on the upstream side and the immediately downstream side of the transfer unit 7 in the recording material conveyance direction. Further, even when a peeling discharge occurs when the recording material P is separated from the belt 10, a high-quality print image can be output without deteriorating the toner image.

[Example 1]
FIG. 4 is a schematic diagram of the image forming apparatus in this embodiment. FIG. 5 is a block diagram of a main control system of the image forming apparatus of this embodiment. The image forming apparatus of the present embodiment is basically a digital image forming apparatus of an electrophotographic system, a laser exposure system, and a transfer / conveyance belt type, similar to the reference example . Constituent members / portions common to the image forming apparatus of the reference example are denoted by common reference numerals, and description thereof is omitted.

Thin paper of the recording medium P based on the recent market needs, to meet the expansion of the thick paper specifications, basis weight corresponding specification width of the recording material in the image forming apparatus (paper) is also from 50 g / m ² about the paper in the thin paper, thick paper led and has been spread and up to about 300g / ^{m 2} paper. With respect to the above-mentioned specification width corresponding to the basis weight of the recording material, particularly for the image forming apparatus in the POD market, the image forming speed is constant without reducing the image forming speed regardless of the basis weight specification of the recording material to be fed. High-speed output is required. In order to respond to the needs, the image forming apparatus of this embodiment is provided with another fixing device 9A as a fixing unit on the downstream side in the recording material conveyance direction of the fixing device 9 of the image forming apparatus of the reference example . The fixing device 9 is a first fixing device, and the fixing device 9A is a second fixing device. That is, a roller pair, which is a heating and pressing mechanism for main-fixing an unfixed toner image on the recording material P, is further added to the configurations 91 and 92 of the reference example . Further, a recording material information detecting unit 70 for detecting recording material information of the recording material P supplied from the feeding cassette 80 to the image forming apparatus is disposed in the conveyance path 82.

  In this embodiment, the recording material information detection means 70 is a rigidity detection means for detecting the rigidity of the recording material P using ultrasonic waves. FIG. 5B is a schematic diagram of the rigidity detecting means 70. The rigidity detecting means 70 is disposed in the middle of the conveyance path 82 of the recording material P from the feeding cassette 80 to the registration roller pair 6. The recording material P is conveyed in the direction of arrow Y by the pair of paper feed rollers 74 and 75 and the pair of paper feed rollers 76 and 77. In the middle of the conveyance path 82, the ultrasonic transmission element 71 and the reception element 72 are arranged on the upstream side and the downstream side in the recording material conveyance direction Y so as to come into contact with the recording material P, respectively. When the recording material P is conveyed to a position in contact with both the ultrasonic transmission element 71 and the reception element 72 during an image forming operation or the like, an ultrasonic signal 73 is transmitted from the ultrasonic transmission element 71. The ultrasonic transmission element 71 transmits an ultrasonic signal 73 having a certain frequency / output, and the transmitted ultrasonic signal 73 changes in accordance with the rigidity characteristics of the recording material P. The changed signal is received by the receiving element 72 and input to the control circuit unit 100. The control circuit unit 100 calculates a change amount (attenuation rate) of the transmission signal from the transmission element 71 and the reception signal by the reception element 72. As shown in FIG. 5C, the attenuation rate has a correlation with the rigidity characteristic value of the recording material P, and the rigidity characteristic value is derived from the correlation characteristic.

In this embodiment, the control circuit unit 100 uses the recording material information detected by the recording material information detection unit 70 for the recording material P supplied to the image forming apparatus, and the second fixing device. This is a configuration for controlling the operation of 9A. This will be described with reference to the control flowchart of FIG. When one or a plurality of continuous image forming jobs are input, the control circuit unit 100 starts an image forming operation. In the present embodiment, feeding of the recording material P from the feeding cassette 80 is started (step S1). Then, when the first fed recording material passes through the stiffness detection means 70 of the conveyance path 82, the stiffness characteristic value of the recording material P is detected as described above (S2). The stiffness characteristic value of the recording material P detected by the stiffness detector 70 is input to the control circuit unit 100. The control circuit unit 100 determines whether or not the detected stiffness characteristic value is equal to or less than a predetermined value X1 (S3). In the conventional image forming apparatus, it was a recording material having a basis weight of about 70 g / m ² or less that caused an image failure due to abnormal discharge when the recording material P was separated from the belt 10. Therefore, when the rigidity characteristic value of the recording material having a basis weight of 70 g / m ² was obtained by the rigidity detecting means 70, it was X1. In this embodiment, the predetermined value relating to the detected stiffness characteristic value is set to X1, and the value is set in the control circuit unit 100 as reference data (comparison standard value).

(1) When the rigidity characteristic value of the recording material P that has been passed is equal to or less than the predetermined value X1 In step S3, when the rigidity characteristic value of the recording material P is equal to or less than the predetermined value X1, that is, the recording material P is thin paper ( In the case of paper with a small basis weight), the control circuit unit 100 puts the first fixing device 9 into an operating state, but puts the second fixing device 9A into a non-operating state (S4). Here, the operating state of the fixing device means that the fixing roller 91 and the pressure roller 92, which are heating and pressure mechanisms, are rotationally driven, and the heaters H1 and H2 are energized to cause the fixing roller 91 and the pressure roller 92 to be in a predetermined state. The temperature is raised to the fixing temperature and maintained at that temperature. In the non-operating state of the fixing device, the fixing roller 91 and the pressure roller 92 are rotationally driven (idle rotation), but the energization to the heaters H1 and H2 is turned off and the fixing roller 91 and the pressure roller 92 are turned off. Heating is not performed.

  Also, toner image formation on the drum 1 that has been driven to rotate is started (S5). The recording material P fed from the feeding cassette 80 reaches the registration roller pair 6 and is received by the leading end abutting against the nip portion of the roller pair 6 whose rotation is stopped at that time. The motor M6 is turned on at a predetermined control timing (S6). As a result, rotation of the roller pair 6 is started, and the recording material P is fed to the upper surface of the belt 10 that is circulatingly moved and is carried on the belt 10. Then, the recording material P is conveyed by the movement of the belt 10 and introduced into the transfer unit 7, and sequentially receives the transfer of the toner image on the drum 1 (S7).

The recording material P onto which the toner image has been transferred in the transfer unit 7 is conveyed by the subsequent movement of the belt 10 and reaches the position where the electromagnetic wave irradiation means 20 is disposed. Also in this embodiment, as in the reference example , the control circuit unit 100 is only in a period from the arrival of the leading end portion of the recording material P to the electromagnetic wave irradiation means arrangement position to the passage of the electromagnetic wave irradiation means arrangement position of the rear end portion. The infrared lamp 21 of the electromagnetic wave irradiation means 20 is turned on (S8, S9). As a result, the toner image that has not been fixed is assumed to be attached to the recording material P before the recording material P reaches the separation portion A. Then, the recording material P reaches the separation portion A and is separated from the belt surface by the curvature. At this time, since the toner image on the recording material P is assumed by the electromagnetic wave irradiation means 20, the toner image scatters due to the peeling discharge generated at the time of separation as described above even when the recording material P is a thin paper with low rigidity. There is no deterioration such as. That is, the curvature is separated and conveyed from the belt 10 while maintaining high image quality.

  Then, the recording material P separated from the belt 10 is introduced into the first fixing device 9 in an operating state and receives the main fixing of the toner image. The recording material exiting the first fixing device 9 is then discharged out of the image forming apparatus through the non-operating second fixing device 9A (S10). Since the recording material P is thin paper, it is sufficient to perform the main fixing of the toner image on the recording material P only by operating only the first fixing device 9. If there is only one image forming job, the image forming operation is completed. In the case of a plurality of continuous image forming jobs, the above-described image forming operation is repeatedly executed until the last one image is formed (S11 → S12 → S5).

(2) When the stiffness characteristic value of the passed recording material P exceeds the predetermined value X1 In step S3, when the stiffness characteristic value of the recording material P exceeds the predetermined value X1, that is, recording. When the material P is a class of thick paper (paper having a large basis weight), the control circuit unit 100 keeps the infrared lamp 21 of the electromagnetic wave irradiation means 20 in the off state. Then, the second fixing device 9 </ b> A is put into an operating state together with the first fixing device 9. Under this condition, an image forming operation is executed (S14 to S18, S11, S19).

  That is, since the recording material P to be passed is highly rigid (paper having a relatively large basis weight), the separation angle of the recording material P from the belt 10 becomes small. The toner image on the recording material P is unfixed, but the peeling discharge is suppressed to such an extent that harmful effects occur. Therefore, the recording material P is separated from the belt 10 without deteriorating the toner image. In other words, it is not necessary to take a procedure for assuming the toner image by turning on the infrared lamp 21 of the electromagnetic wave irradiation means 20. Further, since the first fixing device 9 and the second fixing device 9A are in an operating state, the unfixed toner image is properly fixed onto the recording material P even if the recording material P is a thick paper.

  Even when the stiffness characteristic value of the recording material P exceeds X1, there is no problem in image and recording material conveyance even if the infrared lamp 21 of the electromagnetic wave irradiation means 20 is turned on. However, if the heaters of the first and second fixing devices 9 and 9A are fully energized and then the infrared lamp 21 of the electromagnetic wave irradiation unit 20 is energized, the power consumption increases. End up. In this embodiment, if X1 <rigidity characteristic value, the electromagnetic wave irradiation means 20 is always controlled to be turned off, so that there is a merit in terms of power consumption suppression.

  As the recording material information detection method, the user inputs the basis weight information of the recording material P loaded on the feeding cassette 80 from the operation unit 300 of the image forming apparatus, and controls the image forming apparatus based on the information. It doesn't matter. However, the configuration shown in the present embodiment is advantageous in that the input work of the basis weight information for the user to the image forming apparatus can be omitted.

  Further, when the rigidity characteristic value is X1 or less, the energization condition (current) to the electromagnetic wave irradiation means 20 may be changed and controlled according to the characteristic value. When the rigidity characteristic value exceeds X1, the energization condition (current) to the fixing devices 9 and 9A may be changed and controlled according to the characteristic value. By taking the configuration described above, there is a merit in terms of suppressing power consumption.

  By adopting the configuration described above, the recording material P is stably carried and conveyed by the belt 10, so that the recording material posture can be kept constant and the recording material can be stably charged. For this reason, it is possible to effectively suppress the separation failure that the recording material P is electrostatically attached to the drum 1 and the image failure on the upstream side and the immediately downstream side of the transfer unit 7. Further, even when a peeling discharge occurs when the recording material P is separated from the belt 10, a high-quality print image can be output without deteriorating the toner image.

[Example 2]
FIG. 7 is a schematic configuration diagram of the image forming apparatus of this embodiment. The image forming apparatus according to the present exemplary embodiment is the same as the image forming apparatus according to the first exemplary embodiment , except that a four-color full-color image forming mechanism unit 60 is used as the image forming mechanism unit for the toner image transferred to the recording material P conveyed by the belt 10. is there. Since other image forming apparatus configurations are the same as those of the image forming apparatus according to the first exemplary embodiment , common constituent members and portions are denoted by common reference numerals, and description thereof is omitted.

  In the image forming mechanism 60, Pa, Pb, Pc, and Pd are the first to fourth image forming units, and the intermediate transfer belt 61 (second image carrier) that is circulated and moved at a predetermined speed in the direction of the arrow R61. The body is sequentially arranged along the moving direction of the body. Each image forming apparatus is an electrophotographic image forming mechanism that forms a toner image on an electrophotographic photosensitive drum 1 (first image carrier) that is rotationally driven in a direction indicated by an arrow by an electrophotographic process device. is there. In this embodiment, the first image forming unit Pa forms a yellow toner image corresponding to the yellow component image of the full-color image on the drum 1. The second image forming unit Pb forms a magenta toner image corresponding to the magenta component image of the full color image on the drum 1. The third image forming unit Pc forms a cyan toner image corresponding to the cyan component image of the full-color image on the drum 1. The fourth image forming unit Pd forms a black toner image corresponding to the black component image of the full color image on the drum 1. Then, the color toner images formed on the drum 1 of the first to fourth image forming units are sequentially primary-transferred so as to be superimposed on the surface of the intermediate transfer belt 61 in the primary transfer unit. The superimposed transfer toner image reaches the secondary transfer portion 7 which is the opposite portion between the transfer roller 31 and the transfer roller facing roller 62 by the subsequent movement of the belt 61, and collectively on the recording material P carried and conveyed by the belt 10. Secondary transferred. That is, an unfixed four-color full-color toner image is formed on the recording material P. Then, the recording material passes through the separation section A and the fixing devices 9 and 9A, and a four-color full-color image formed product is printed out. The surface of the intermediate transfer belt 61 after the transfer of the toner image to the recording material P is cleaned by removing residual toner remaining by the cleaner 63, and is repeatedly used for image formation.

As in the image forming apparatus according to the first exemplary embodiment , the control circuit unit 100 uses the electromagnetic wave irradiation unit based on the recording material information detected by the recording material information detection unit 70 for the recording material P supplied to the image forming apparatus. 20 and the operation of the second fixing device 9A (FIG. 6). Therefore, the image forming apparatus of this embodiment can obtain the same effects as those of the first embodiment .

  1 · 61 · · Image carrier 10 · · Transfer conveyor belt, 31 to 33 · · Multiple belt suspension members, 7 · · Image transfer portion, A · · Separation portion, 9 · 9A · · Fixing device, · · · .Recording materials, 20 ..Electromagnetic wave irradiation means

Claims (4)

A rotatable image carrier on which a toner image is formed, and a plurality of belt suspension members including a recording material separation roller. The toner image is transferred to a recording material and transferred to a recording material, and the recording material is separated by curvature at a separation portion which is a belt winding portion of the separation roller at a downstream side of the image transfer portion in the recording material conveyance direction. a transfer conveyor belt, a fixing device for fixing a toner image of the separated recording material from the transfer conveyor belt, in between the separation unit from the front Symbol image transfer unit, the recording material carrying surface of the transfer conveyor belt In an image forming apparatus comprising: an electromagnetic wave irradiating unit that is disposed in a non-contact manner on the side and irradiates an electromagnetic wave on a toner image carried on a recording material and presumably attaches the toner image to the recording material ;
An acquisition means for acquiring the rigidity of the recording material fed to the apparatus;
Control means for operating the electromagnetic wave irradiation means when the result obtained by the obtaining means is equal to or less than a predetermined rigidity;
An image forming apparatus comprising:   The image forming apparatus according to claim 1, wherein the electromagnetic wave irradiation unit is energized when the recording material passes through a position where the electromagnetic wave irradiation unit is disposed. The image forming apparatus according to claim 1 or 2, characterized in that the transfer conveyor belt is a belt of a resin material. The image forming apparatus according to any one of claims 1 to 3, wherein the electromagnetic wave irradiation means is an infrared lamp and reflector.