JP2008275842A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which is capable of accurately detecting an ambient environmental temperature, even when an environment detection means is arranged and used in such a place that is influenced by the temperature rise of an apparatus main body. <P>SOLUTION: The image forming apparatus A provided with a fixing means 14 for heat-fixing a toner image formed on a material to be recorded P has the environment detection means 26 inside and a control means for controlling image forming conditions, on the basis of environmental information detected by the environment detection means. The control means predicts the environmental information expected to be obtained from the environment detection means and obtains the information of the environment where the image forming apparatus is placed, from the predicted environmental information and the environmental information detected by the environment detection means, to control the image forming conditions, on the basis of the obtained environmental information, when image formation is started. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention forms and supports an unfixed toner image by a transfer method or a direct method on a recording material by an appropriate image forming process such as an electrophotographic method, an electrostatic recording method, or a magnetic recording method, and the unfixed toner. The present invention relates to an image forming apparatus for fixing an image on a recording material by a heat fixing unit.

  As a fixing unit in this type of image forming apparatus, a belt fixing type fixing device has been adopted in response to a recent demand for energy saving. A belt fixing type fixing device forms a fixing nip by sandwiching a thin belt having heat resistance between a ceramic heater as a heating means and a pressure roller as a pressure member. Then, the belt and the pressure roller are rotated together to fix the unfixed toner image by applying heat and pressure while conveying the recording material (see, for example, Patent Documents 1 to 4).

  In this belt fixing type fixing device, the heat capacity of the belt, which is a heating member, is very small compared to the conventional heat roller type fixing device, so that the heat energy from the heating means can be efficiently used in the fixing process. . Therefore, a so-called quick start that can shorten the waiting time from the power-on of the image forming apparatus to the printable state is possible. Furthermore, since the heat capacity of the heating member is small and it is not necessary to preheat the heating member during standby for printing, the power consumption of the image forming apparatus can be kept low, and energy saving can be achieved.

  Such a belt-fixing type fixing device using a heater can be raised to a fixable temperature in 30 seconds or less. In this way, if it is attempted to shorten the time from the start of printing to the end of discharge of the recording material, when the recording material on which the unfixed toner image is formed reaches the fixing device, the temperature rise of the fixing device is fixed. The temperature must be optimal.

  However, as described above, since the heating member of the belt fixing method has a small heat capacity, the heating member has an excessive amount of heat or an insufficient amount of heat depending on the temperature of the environment in which the image forming apparatus is used (hereinafter referred to as “environment temperature”). Cheap. For example, when the environmental temperature is high, the heating member may have an excessive amount of heat, which may cause a hot offset in which a part of the image remains on the belt side during fixing. On the other hand, when the environmental temperature is low, the temperature of paper, toner, and the like also becomes low. Therefore, the heating member may have insufficient heat at the time of fixing, and fixing failure may occur.

For this reason, there has been proposed an image forming apparatus that detects the environmental temperature in which the image forming apparatus is placed by using an environment detection unit and sets the optimum fixing temperature (for example, see Patent Document 5).
JP-A-63-313182 Japanese Patent Laid-Open No. 2-157878 JP-A-4-44075 JP-A-4-204980 JP 2001-222183 A

  In order to optimally set the fixing temperature as an image forming condition, the environment information detected by the environment detecting unit must always be a result of accurately detecting the environment temperature where the image forming apparatus is placed.

  However, recent image forming apparatuses are required to be faster and smaller. In order to cope with high speed, it is necessary to set the fixing temperature of the fixing device high, and the amount of heat generation increases. In order to further increase the speed, it is necessary to increase the size of motors that drive the image forming apparatus, which also increases the amount of heat generation. On the other hand, in order to reduce the size of the image forming apparatus, it is necessary to mount the components of the image forming apparatus at a high density. As a result, it becomes impossible to have a heat insulation configuration in which heat is sufficiently released to the outside or the environment detection means is kept away from the heat generating component. As a result, it is very difficult for the environment detection means to always accurately detect the environment information without being affected by the temperature rise of the main body, and the fixing temperature setting may become inappropriate.

  The present invention has been made paying attention to the above points, and can accurately detect the ambient temperature even if the environment detecting means is arranged and used in a place where the temperature of the apparatus main body is affected. An object of the present invention is to provide an image forming apparatus capable of performing the above.

  In order to achieve the above object, the present invention has the following configuration.

  An image forming apparatus including a fixing unit that thermally fixes a toner image formed on a recording material, the image forming apparatus including an environment detection unit, based on environmental information detected by the environment detection unit In the image forming apparatus having a control unit for controlling image forming conditions, the control unit predicts environmental information that will be obtained from the environment detection unit at the start of image formation, and the predicted environment information and the An image forming apparatus characterized in that it obtains environmental information where the image forming apparatus is placed from environmental information detected by the environment detecting means, and controls image forming conditions based on the obtained environmental information. .

  As described above, according to the present invention, there is provided an image forming apparatus capable of accurately detecting the ambient environmental temperature even when the environmental detection means is disposed and used in a place where the temperature of the apparatus main body is affected. Can be provided.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to examples.

  The image forming apparatus according to the first embodiment will be described in detail below with reference to FIGS. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention only to those unless otherwise specified. .

[overall structure]
First, the overall configuration of the image forming apparatus will be outlined with reference to FIG.

  FIG. 1 is a longitudinal sectional view showing an overall configuration of a printer engine A which is an aspect of an electrophotographic image forming apparatus. The photosensitive drum 1 is rotationally driven at a predetermined process speed in the direction of the arrow in the figure by a driving means (not shown). Around the photosensitive drum 1, a charging device 2 that uniformly charges the surface of the photosensitive drum 1 in order along the rotation direction, and a laser beam is irradiated based on image information to form an electrostatic latent image on the photosensitive drum 1. A scanner unit 3 is disposed. Then, the developing unit 4 for developing the toner image by attaching toner to the electrostatic latent image, the transfer roller 6 for transferring the toner image on the photosensitive drum 1 to the transfer material P, and the transfer remaining on the surface of the photosensitive drum 1 after the transfer. A cleaning device 25 and the like for removing residual toner are provided.

  Here, the photosensitive drum 1, the charging device 2, and the cleaning device 25 form a photosensitive drum unit 5, and the photosensitive drum unit 5 is further integrated into a cartridge with the developing unit 4 to form a process cartridge 7.

  The scanner unit 3 is arranged in a substantially horizontal direction of the photosensitive drum 1, and image light corresponding to an image signal is irradiated to a polygon mirror 9 rotated at high speed by a scanner unit motor (not shown) by a laser diode (not shown). The The image light reflected by the polygon mirror 9 is configured to selectively expose the charged photosensitive drum 1 surface through the imaging lens 10 to form an electrostatic latent image.

The transfer roller 6 facing the photosensitive drum 1 includes, for example, EPDM (ethylene-propylene-diene terpolymer), urethane rubber, in which a metal core is adjusted to a volume resistivity of about 10 ⁷ to 10 ¹¹ Ω · cm. Some are covered with an elastic body such as NBR (nitrile butadiene rubber). A positive bias is applied to the transfer roller 6 from a power source (not shown), and a negative toner image on the photosensitive drum 1 is transferred to the transfer material P in contact with the photosensitive drum 1 by an electric field generated by the bias. .

  The paper feed unit 8 feeds and conveys the transfer material P to the image forming unit, and a plurality of transfer materials P are stored in the paper feed cassette 11. At the time of image formation, the paper feed roller 12 (half-moon roller) and the registration roller pair 13 are driven and rotated according to the image forming operation to separate and feed the transfer material P in the paper feed cassette 11 one by one. The leading edge comes into contact with the registration roller pair 13 and temporarily stops to form a loop. Thereafter, the paper is fed to a nip formed by the transfer roller 6 and the photosensitive drum 1. Reference numeral 24 denotes a registration sensor, on which image formation is performed with reference to the time when the transfer material P crosses the registration sensor.

  The fixing device 14 is a fixing device of a fixing belt type and a pressure rotating body driving method (tensionless type), and fixes the toner image transferred to the transfer material P. It comprises a cylindrical fixing belt 141 as a rotator and a pressure roller 142 that presses against the belt and applies heat and pressure to the transfer material P (the configuration of the fixing device will be described in detail later). That is, the transfer material P onto which the toner image on the photosensitive drum 1 has been transferred is conveyed by the fixing belt 141 and the pressure roller 142 and is given heat and pressure when passing through the fixing device 14. As a result, the toner image is fixed on the surface of the transfer material P. The fixed transfer material P is discharged out of the main body by the paper discharge roller pair 15 with the image surface facing down from the paper discharge unit 16.

  The control device B controls the operation of the printer engine A and has a CPU 17, a RAM (read / write memory) 18, a ROM (read only memory) 19, an EPROM (read / write nonvolatile memory) 27, and a clock 28. is doing. The ROM 19 stores a program for controlling the image forming apparatus and various data, and the RAM 18 is used for storing data taken in for controlling the image forming apparatus. Furthermore, an environmental sensor 26 is connected to the CPU 17. The environment sensor 26 is a temperature sensor, and temperature information in the printer engine A is taken into the CPU 17. The clock 28 is backed up by a battery (not shown) and operates even when the power of the image forming apparatus is turned off.

[Process cartridge]
The process cartridge containing toner according to this embodiment will be described in detail with reference to FIGS. FIG. 2 is a longitudinal sectional view illustrating a schematic configuration of the process cartridge according to the first embodiment, and FIG. 3 is a perspective view illustrating a schematic configuration of the process cartridge according to the first embodiment.

  The process cartridge 7 is divided into a photosensitive drum 1, a photosensitive drum unit 5 having a charging unit and a cleaning unit, and a developing unit 4 having a developing unit for developing an electrostatic latent image on the photosensitive drum 1.

  The photosensitive drum 1 is configured by applying an organic photoconductor layer (OPC photosensitive member) to the outer peripheral surface of an aluminum cylinder.

  In the photosensitive drum unit 5, the photosensitive drum 1 is rotatably attached to the cleaning frame 51 via bearings 31a and 31b. A charging device 2 for uniformly charging the surface of the photosensitive drum 1 and a cleaning blade 60 for removing the toner remaining on the photosensitive drum are disposed on the periphery of the photosensitive drum 1. Further, the residual toner removed from the surface of the photosensitive drum 1 by the cleaning blade 60 is sequentially sent by a toner feeding mechanism 52 to a waste toner chamber 53 provided behind the cleaning frame. By transmitting the driving force of a driving motor (not shown) to one end, the photosensitive drum 1 is driven to rotate counterclockwise in the drawing according to the image forming operation.

  The developing unit 4 includes a developing roller 40 that contacts the photosensitive drum 1 and rotates in the direction of the arrow, a toner container 41 that contains toner, and a developing frame body 45. The developing roller 40 is rotatably supported by the developing frame 45 via a bearing member and rotates in the arrow Y direction. On the circumference of the developing roller 40, a toner supply roller 43 and a developing blade 44 that are in contact with the developing roller 40 and rotate in the direction of arrow Z are disposed. Further, a toner transport mechanism 42 for stirring the toner stored in the toner container 41 and transporting it to the toner supply roller 43 is provided.

  The developing unit 4 is supported by the pin 49a so that the entire developing unit 4 can swing with respect to the photosensitive drum unit 5 around the support shafts 49 provided on the bearing members 47 and 48 attached to both ends of the developing unit 4, respectively. Has a suspended structure. In the state of the process cartridge 7 alone (not attached to the printer main body), the developing roller 40 is always urged by the pressure spring 54 so as to abut on the photosensitive drum 1 by the rotational moment about the support shaft 49. . Further, the toner container 41 of the developing unit 4 is integrally provided with a rib 46 for contacting a separating means (described later) of the printer main body A when the developing roller 40 is separated from the photosensitive drum 1.

[Fixing device]
The fixing device according to this embodiment will be described in detail with reference to FIG. FIG. 4 is a longitudinal sectional view illustrating a schematic configuration of the belt heating type fixing device according to the first embodiment.

  141 is a fixing belt as a first rotating body (first fixing member), using SUS formed in a cylindrical shape as a belt base material, on which a silicone rubber layer is formed as an elastic layer, Further, a PFA resin tube is coated as the outermost layer.

  Reference numeral 142 denotes a pressure roller as a second rotating body (second fixing member). Reference numeral 143 denotes a heater holder having a substantially semi-circular arc-shaped cross-sectional heat resistance and rigidity as a heating body holding member, and 144 is a fixing heater as a heating body (heat source). It is arranged along. The fixing belt 141 is loosely fitted on the heater holder 143. The fixing heater 144 is formed by applying a conductive paste containing a silver / palladium alloy on an alumina substrate to form a film having a uniform thickness by a screen printing method. This is a ceramic heater.

  The heater holder 143 is formed of a liquid crystal polymer resin having high heat resistance, plays a role of holding the fixing heater 144 and guiding the fixing belt 141.

  The pressure roller 142 is formed by forming a silicone rubber layer on a stainless steel core by injection molding and coating a PFA resin tube thereon. The pressure roller 142 is disposed with both ends of the cored bar rotatably supported by a device frame (not shown). The fixing heater 144 and the heater holder 143 are brought into pressure contact with the elastic layer of the pressure roller 142 via the fixing belt 141 with a predetermined pressing force against the elasticity of the elastic layer via the fixing belt 141, and a predetermined necessary for heat fixing. A fixing nip portion 146 having a width is formed. The pressurization mechanism has a pressure release mechanism, and is configured to release the pressurization and remove the recording material P at the time of jam processing or the like.

  Reference numerals 147 and 148 denote two main and sub thermistors as first and second temperature detection means. A main thermistor 147 as a first temperature detecting means is in elastic contact with the inner surface of the fixing belt 141 above the heater holder 143 and detects the temperature of the inner surface of the fixing belt 141. A sub thermistor 148 as a second temperature detecting means is in contact with the back surface of the fixing heater 144 and detects the temperature of the back surface of the fixing heater.

[Drive configuration]
Next, the operation mechanism when the process cartridge 7 is mounted on the printer main body A will be described in detail.

  As described above, when the process cartridge 7 is a single unit, the developing roller 40 is always in contact with the photosensitive drum 1 as shown in FIG.

  On the other hand, a cam 20 a (FIG. 1) for separating the developing roller 40 from the photosensitive drum 1 against the urging force of the developing unit 4 is disposed on the back side in the insertion direction of the process cartridge 7 of the printer main body A. . The cam 20a is rotated by driving means (not shown), and the developing roller 40 is separated from the photosensitive drum 1 when the cam 20a raises the rib 46. When the cam 20a releases the pushing up of the rib 46, the developing roller 40 is moved to the photosensitive drum 1. Abut. Normally, when the process cartridge is mounted on the printer main body, the cam 20 a pushes up the rib 46 so that the developing roller 40 is separated from the photosensitive drum 1.

  Accordingly, when the process cartridge 7 is mounted and not used for a long time, the developing roller 40 is always separated from the photosensitive drum 1, so that the developing roller 40 is kept in contact with the photosensitive drum 1 for a long time. The permanent deformation of the generated roller layer can be reliably prevented. The photosensitive drum 1 and the developing roller 40 of the process cartridge 7 mounted on the image forming apparatus main body A can be separately driven by a motor (not shown).

[Operation of Image Forming Apparatus]
In the image forming apparatus according to the present embodiment, when the image forming operation is continuously performed under a certain environment, the environment sensor 26 itself is heated by the influence of heat generated from the low voltage power source, the high voltage power source, the motor, the fixing device, and the like. Therefore, the temperature detected by the environment sensor 26 taken into the CPU 17 rises according to the image forming operation time as shown in FIG. This temperature rise curve changes depending on the environmental temperature, for example, as shown in FIGS. Further, when the print mode corresponding to the paper type and basis weight is set, the fixing temperature control, the process speed, and the like may be changed, and at that time, the temperature rise curve is different from that in FIG. Therefore, in this embodiment, a temperature rising curve for each printing mode is prepared in advance for each environmental temperature at a predetermined temperature interval. When the environmental temperature is between the temperature intervals of the prepared temperature rising curve, a temperature rising curve corresponding to the environmental temperature can be obtained by interpolation from the temperature rising curves before and after the environmental temperature. As a result, it is possible to predict the temperature increase ΔT detected by the environmental sensor whose temperature has been increased, from the environmental temperature T _env that is the temperature at the start of the image forming operation and the image forming operation time.

Compare the detected temperature T _sens-end of the environmental sensor with the predicted temperature T _env + ΔT of the environmental sensor at the end of image formation. If the difference is less than the measurement error (about ± 2 ° C) of the environmental sensor, Since it is considered that there is not, T _env is set as the environmental temperature. On the other hand, if there is a difference greater than the measurement error of the environmental sensor, it can be predicted that the environmental temperature has changed by the end of image formation. At this time, the environmental temperature T _env is obtained by correcting as T _env = T _sens-end −ΔT. A series of operations for correcting the environmental temperature T _env will be referred to as an environmental detection sequence 1.

On the other hand, when the image forming operation is finished, heat is no longer generated, so that the temperature detected by the environment sensor 26 starts to decrease, and a temperature decreasing curve as shown in FIG. 6 is drawn. This curve is determined by the temperature T _sens-end of the environmental sensor 26 when the temperature is raised, the environmental temperature T _env where the image forming apparatus is placed, and the elapsed time from the end of the image forming operation. Therefore, similarly to the temperature increase curve, a temperature decrease curve for each environmental temperature T _env is prepared in advance for each T _sens-end at a predetermined temperature interval. For this, a theoretical formula using T _sens-end and T _env as parameters may be used.

When performing image forming operation again compares the actual sensed temperature T _sens-start the current detected temperature T _g of the environmental sensor 26 that is predicted from the temperature drop curve. If there is a difference greater than the sensor measurement error (approximately ± 2 ° C.), the environmental temperature T _env is obtained by correcting by T _env = T _env + (T _{sens -start} −T _g ).

A series of sequences for correcting the environmental temperature T _env will be referred to as an environmental detection sequence 2.

By using the above sequence, the environmental temperature T _env can be accurately predicted even if the environmental sensor is heated. Therefore, in this embodiment, the following parameters are stored in the EPROM 27 and read out as necessary to correct the environmental temperature T _env .

T _env : environmental temperature ΔT: degree of temperature increase from T _env T _sens-end : actual environmental sensor detection temperature at the _{end of the} image forming operation t _end : end time of the image forming operation Next, the image forming operation of this embodiment This will be described in detail with reference to FIGS. FIG. 7 is a flowchart illustrating the operation of the image forming apparatus according to the first embodiment.

When a print signal is input to the image forming apparatus main body, an image forming operation is started (Start, S700). The CPU 17 stores the time obtained from the clock 28 to measure the image forming operation time (S701), and then reads T _sens-end , t _end , and T _env from the EPROM 27 (S702) and executes the environment detection sequence 2. . Then, the environmental temperature T _env where the image forming apparatus is currently placed is obtained (S703).

Next, a target temperature _Tt for fixing temperature control for controlling the fixing device 14 to a predetermined temperature is set from the environmental temperature T _env (S704), and the temperature control of the fixing device 14 and the rotation of the photosensitive drum 1 and the scanner unit 3 are controlled. The rotation is started (S705).

Next, application of a charging bias is started after a predetermined time from the start of rotation of the photosensitive drum 1 (S706). When the temperature T of the fixing device reaches a predetermined temperature _Tt (S707), rotation of the developing roller 40 and application of a developing bias are started (S708).

  Then, after a predetermined time, the developing roller 40 is brought into contact with the photosensitive drum 1 (S709), and then a transfer material is picked up (S710), and an image is formed (S711).

When the image forming operation is completed, the time required for the image forming operation is obtained from the current time obtained from the clock 28 and the previously stored time at the start of the image forming operation (S712). Then, the environment detection sequence 1 is executed and T _env is corrected (S713). Finally, T _env , ΔT, T _sens-end , and t _end are written in the EPROM 27 (S714), and the image formation is completed (S715).

  By doing so, the correct environmental temperature can be obtained even if the environmental sensor itself is heated due to the temperature rise in the image forming apparatus main body, and the fixing temperature, which is an appropriate control condition of the fixing device, can be obtained. Can be set.

  Example 2 will be described below. In this embodiment, the first embodiment is applied to a color image forming apparatus that forms an image by performing an image forming process a plurality of times. In addition, the same structure and effect | action of Example 1 attach | subject the same number, and abbreviate | omit description.

[overall structure]
The image forming apparatus according to this embodiment will be described in detail with reference to FIG. FIG. 8 is a longitudinal sectional view showing the entire configuration of a full-color laser beam printer C which is an aspect of the color image forming apparatus according to the second embodiment.

  The color image forming apparatus C shown in the figure has a configuration in which process cartridges 7a, 7b, 7c, and 7d that respectively store toners of yellow, magenta, cyan, and black are vertically stacked on the process cartridge described in the first embodiment. It has become.

  The scanner units 3a, 3b, 3c, and 3d are vertically stacked in the same manner as the process cartridges 7a, 7b, 7c, and 7d, and are disposed substantially horizontally with the photosensitive drums 1a, 1b, 1c, and 1d.

Next, an electrostatic transfer belt 23 that circulates and moves in contact with all the photosensitive drums 1a, 1b, 1c, and 1d is disposed. The electrostatic transfer belt 23 is made of a resin material such as PVdF (polyvinylidene fluoride), polyamide, polyimide, PET (polyethylene terephthalate), or polycarbonate having a thickness of 50 to 300 μm and a volume resistivity of about 10 ⁹ to 10 ¹⁶ Ω · cm. . Further, rubber materials such as chloroprene rubber, EPDM, NBR, urethane rubber having a thickness of 0.5 to 2 mm and a volume resistivity of about 10 ⁹ to 10 ¹⁶ Ω · cm are also used. Furthermore, if necessary, conductive fillers such as carbon, ZnO, SnO ₂ , and TiO ₂ may be dispersed in these materials to adjust the volume resistivity to about 10 ⁷ to 10 ¹¹ Ω · cm. .

  The electrostatic transfer belt 23 is supported by four-axis rollers 22a, 22b, 22c and 22d in the vertical direction, and the transfer material P is electrostatically adsorbed on the outer peripheral surface on the left side in the drawing, thereby the photosensitive drums 1a, 1b and 1c. , 1d circulates to bring the transfer material P into contact therewith. As a result, the transfer material P is conveyed to the transfer position by the electrostatic transfer belt 23, and the toner images on the photosensitive drums 1a, 1b, 1c, and 1d are respectively transferred.

  Transfer rollers 6a, 6b, 6c, and 6d are arranged in parallel at positions facing the inner side of the electrostatic transfer belt 23 and facing the four photosensitive drums 1a, 1b, 1c, and 1d.

The transfer rollers 6 a, 6 b, 6 c, 6 d electrostatically transfer the toner images formed on the photosensitive drums 1 a, 1 b, 1 c, 1 d to the transfer material P on the electrostatic transfer belt 23. For example, a metal core is covered with an elastic body such as EPDM (ethylene-propylene-diene terpolymer), urethane rubber, or NBR (nitrile butadiene rubber) adjusted to a volume resistivity of about 10 ⁵ to 10 ⁸ Ω · cm. What was made into the structure which can be used can be used. A positive bias is applied to the transfer rollers 6a, 6b, 6c, and 6d from a power source (not shown), and the transfer material P in contact with the photosensitive drums 1a, 1b, 1c, and 1d is exposed to light by an electric field generated by the bias. Negative toner images on the drums 1a, 1b, 1c, and 1d are transferred.

  The control device B controls the operation of the printer engine B, and includes a CPU 17, a RAM (read / write memory) 18, a ROM (read only memory) 19, an EPROM (read / write nonvolatile memory) 27, and a clock 28. is doing. The ROM 19 stores a program for controlling the image forming apparatus and various data, and the RAM 18 is used for storing data taken in for controlling the image forming apparatus. Furthermore, an environmental sensor 26 is connected to the CPU 17. The environmental sensor 26 includes a temperature sensor and a humidity sensor, and temperature information and humidity information in the printer engine B are taken into the CPU 17. The clock 28 is backed up by a battery (not shown) and operates even when the power of the image forming apparatus is turned off.

[Drive configuration]
Next, the operation mechanism when the process cartridges 7a, 7b, 7c, 7d are mounted on the printer main body C will be described in detail.

  In the first embodiment, a cam 20 a for separating the developing roller 40 from the photosensitive drum 1 against the urging force of the developing unit 4 is provided on the back side in the process cartridge insertion direction. In this embodiment, the separation plate 20b is disposed so that the four color developing rollers 40a, 40b, 40c, and 40d can be separated and contacted at the same time. The separation plate 20b can be moved up and down by a drive motor (not shown). The developing rollers 40a, 40b, 40c, and 40d are separated from the corresponding photosensitive drums 1a, 1b, 1c, and 1d when the separating plate 20b is raised, and the developing rollers 40a, 40b, 40c, and 40d are lowered when the separating plate 20b is lowered. Contacts the photosensitive drums 1a, 1b, 1c, 1d.

  When the process cartridges 7a, 7b, 7c, and 7d are attached to the printer main body C, the separation plate 20b is pushed up. Accordingly, the ribs 46a, 46b, 46c, 46d provided in the developing unit ride on the separation plate 20b along the insertion operation of the process cartridges 7a, 7b, 7c, 7d. The developing rollers 40a, 40b, 40c, and 40d are separated from the photosensitive drums 1a, 1b, 1c, and 1d by a predetermined gap. This separated state is always maintained when the power is turned off and when development is not performed.

  Therefore, even when the process cartridges 7a, 7b, 7c, and 7d are mounted and not used for a long time, the developing rollers 40a, 40b, 40c, and 40d are always separated from the photosensitive drums 1a, 1b, 1c, and 1d. It will be in the state. Therefore, it is possible to reliably prevent permanent deformation of the roller layer that occurs when the developing roller is brought into contact with the photosensitive drum for a long period of time. The photosensitive drums 1a, 1b, 1c, 1d and the developing rollers 40a, 40b, 40c, 40d of the process cartridges 7a, 7b, 7c, 7d mounted on the printer main body C can be independently driven by a motor (not shown). is there.

[Image formation operation]
Next, the image forming operation of this embodiment will be described in detail with reference to FIGS. FIG. 9 is a flowchart illustrating the operation of the image forming apparatus according to the second embodiment.

When a print signal is input to the image forming apparatus main body, an image forming operation is started (Start, S900). The CPU 17 stores the time obtained from the clock 28 for measuring the image forming operation time (S901), and then reads T _sens-end , t _end , and T _env from the EPROM 27 (S902). Then, the environment detection sequence 2 is executed to determine the environment temperature T _env where the image forming apparatus is currently placed (S903).

Next, a target temperature _Tt for fixing temperature control for controlling the fixing device 14 to a predetermined temperature is set from the environmental temperature T _env (S904), and the temperature control of the fixing device 14 and the photosensitive drums 1a, 1b, 1c, 1d are set. The rotation and rotation of the scanner units 3a, 3b, 3c and 3d are started (S905).

Next, application of a charging bias is started after a predetermined time from the rotation of the photosensitive drums 1a, 1b, 1c, and 1d (S906). When the temperature T of the fixing device reaches a predetermined temperature _Tt (S907), rotation of the developing rollers 40a, 40b, 40c, and 40d and application of a developing bias are started (S908).

  Then, after a predetermined time, the developing rollers 40a, 40b, 40c, and 40d are brought into contact with the photosensitive drums 1a, 1b, 1c, and 1d, respectively (S909), and then a transfer material is picked up (S910). A resistance value of the transfer material is detected by the biased suction roller 21 (S911), and an optimum transfer bias is selected based on the detected resistance value and the temperature / humidity data acquired from the environmental sensor 26 (S913). Then, image formation is performed (S914).

When the image forming operation is completed, the time required for the image forming operation is obtained from the current time obtained from the clock 28 and the previously stored time at the start of the image forming operation (S915). Then, the environment detection sequence 1 is executed and T _env is corrected (S916). Finally, T _env , ΔT, T _sens-end , and t _end are written in the EPROM 27 (S917), and the image formation is completed (S918).

  A color image forming apparatus has a large number of high-voltage power supplies, and the number and output of motors increase, so that the amount of heat generation further increases as compared with a monochrome image forming apparatus. On the other hand, since the main body is being downsized, the correct environmental temperature is obtained even if the environmental sensor itself is heated by the influence of the temperature rise in the main body of the image forming apparatus by using this embodiment. It is possible to set a fixing temperature which is an appropriate control condition of the fixing device.

  Some recent image forming apparatuses have a duplex unit and are capable of duplex printing. In double-sided printing, since the transfer material once heat-fixed returns to the image forming apparatus again, the temperature tends to rise more easily than in single-sided printing, and the saturation temperature tends to be higher than in single-sided printing. Therefore, in an image forming apparatus capable of double-sided printing, a temperature rising curve for double-sided printing may be added as a temperature rising curve for each printing mode to predict the temperature rise of the environmental sensor.

  In each of the embodiments described above, the main body is provided with a clock backed up by a battery. However, in an image forming apparatus that does not include a clock, the temperature of the thermistor provided in the fixing device is measured to detect the temperature decrease state of the fixing device. Thus, it is possible to predict the time when the power is off.

  Note that the image forming apparatus according to the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the gist thereof.

  That is, the configuration of the process cartridge does not have to be as in the embodiment, and the configuration of the process cartridge does not have to be taken.

  In addition, the start timing of the fixing device, the photosensitive drum, and the scanner unit, the contact timing of the developing roller, and the timing of picking up the transfer material may be other than the above order.

  In each of the above embodiments, an image scanning scanner unit is used, but an exposure apparatus using an LED array may be used.

  Further, in addition to the color image forming apparatus that directly transfers the toner image on the photosensitive drum onto the transfer material, an intermediate transfer type color image forming apparatus may be used.

  In addition to a tandem type color image forming apparatus, the present invention can also be applied to a color image forming apparatus provided with a plurality of developing devices for one photosensitive drum that is well known in the past.

  The image forming apparatus is not limited to a transfer type apparatus, and may be a direct type image forming apparatus that directly forms and supports a toner image using photosensitive paper or electrostatic recording paper as a recording material.

1 is a longitudinal sectional view illustrating a schematic configuration of an image forming apparatus according to Embodiment 1. FIG. FIG. 3 is a cross-sectional view illustrating a schematic configuration of a process cartridge according to the first embodiment. 1 is an exploded perspective view illustrating a schematic configuration of a process cartridge according to Embodiment 1. FIG. 1 is a longitudinal sectional view illustrating a schematic configuration of a fixing device according to Embodiment 1. FIG. It is a figure which shows the temperature rising curve of the environmental sensor which concerns on Example 1. FIG. It is a figure which shows the temperature fall curve of the environmental sensor which concerns on Example 1. FIG. 3 is a flowchart illustrating an operation of the image forming apparatus according to the first exemplary embodiment. 6 is a longitudinal sectional view illustrating a schematic configuration of an image forming apparatus according to Embodiment 2. FIG. 10 is a flowchart illustrating an operation of the image forming apparatus according to the second embodiment.

Explanation of symbols

1, 1a, 1b, 1c, 1d Photosensitive drum 2, 2a, 2b, 2c, 2d Charging device (charging roller)
3, 3a, 3b, 3c, 3d Scanner unit 4 Developing device 6, 6a, 6b, 6c, 6d Transfer roller 7, 7a, 7b, 7c, 7d Process cartridge 14 Fixing device (corresponding to fixing means)
20a Cam 20b Separating plate 23 Electrostatic transfer belt 26 Environmental sensor (corresponding to detection means)
40, 40a, 40b, 40c, 40d Developing roller 141 Fixing belt 142 Pressure roller A, C Image forming apparatus engine

Claims (6)

An image forming apparatus including a fixing unit that thermally fixes a toner image formed on a recording material, the image forming apparatus including an environment detection unit, based on environmental information detected by the environment detection unit In an image forming apparatus having a control means for controlling image forming conditions,
The control means predicts environmental information that would be obtained from the environment detection means at the start of image formation, and the image forming apparatus is installed from the predicted environment information and the environment information detected by the environment detection means. An image forming apparatus characterized in that it is means for obtaining the obtained environmental information and controlling image forming conditions based on the obtained environmental information.   The control means performs control to correct the obtained environment information based on the environment information detected by the environment detection means, the obtained environment information, the image forming operation time, and the print mode at the end of image formation. Then, the corrected environment information is obtained from the corrected environment information at the start of image formation, the elapsed time from the end of the image formation, and the environment information detected by the environment detection means at the end of the image formation. The image forming apparatus according to claim 1, further performing control for correction.   3. The print mode according to claim 2, wherein the print mode is one of a print mode having a different process speed, a print mode having a different fixing condition, a single-sided print mode, or a double-sided print mode. Image forming apparatus.   The image forming apparatus according to claim 1, wherein the image forming condition is a fixing control condition of the fixing unit.   The image forming apparatus according to claim 1, wherein the environmental information is air temperature.   6. The image forming apparatus according to claim 1, wherein the image forming apparatus is a color image forming apparatus that forms an image by performing an image forming process a plurality of times.

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