Image forming apparatus

Abstract

To make it possible to execute a mode for improving productivity while maintaining stability of image output in accordance with a user's selection.SOLUTION: An image forming apparatus can switch between a first mode that is in default settings and causes image forming means to output an image with first throughput when executing an image forming job for forming an image on a recording material, and a second mode that is set in accordance with a user's selection. When the second mode is selected, and when the image forming apparatus executes the image forming job in a state where a predetermined condition is satisfied, the apparatus causes the image forming means to output an image with second throughput higher than the first throughput.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus for forming an image on a recording material. [Background technology]

[0002] Image forming apparatuses such as printers, copiers, and multifunction machines are required to increase productivity. A typical indicator of productivity is throughput (the number of images output per unit time). However, due to various factors such as environmental conditions such as temperature and humidity, printing rate, and the material of the recording material, attempts to increase throughput may lead to image distortion and conveyance failure. For example, when continuous printing is performed with a short paper interval set for paper that has been left in a high-humidity environment for a long time, a temperature difference gradually occurs between the fixing member in contact with the front side of the paper and the fixing member in contact with the back side of the paper, which may cause the paper to curl. Patent Document 1 describes a technology that optimizes fixability, image gloss value, and curl suppression by changing the conveyance interval of the recording material and the temperature setting of the fixing device based on temperature and humidity conditions.

[0003] In addition to the normal mode set as a default operation mode of the image forming apparatus, a multi-purpose mode that can be selected by the user may be provided. Examples of the multi-purpose mode include a mode that improves fixability more than the normal mode, a mode that reduces curling of the recording material more than the normal mode, and a mode that reduces the operating noise of the image forming apparatus more than the normal mode. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2006-235551 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the normal mode set by default, productivity is generally kept relatively low so that image output can be stably performed even if various factors including environmental conditions change. However, events that require productivity to be suppressed to avoid image distortion or conveyance failure are often temporary or occur relatively infrequently. Therefore, if the image forming apparatus is used in the normal mode even if no events that require productivity to be suppressed have occurred, the original productivity of the image forming apparatus may not be achieved.

[0006] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide an image forming apparatus capable of executing a mode that improves productivity while maintaining the stability of image output, according to a user's selection. [Means for solving the problem]

[0007] One aspect of the present invention is an image forming apparatus including an image forming means for forming an image on a recording material, the image forming means having an image carrier, an exposure means for exposing the image carrier to light to form an electrostatic latent image, a development means for developing the electrostatic latent image formed on the image carrier into a toner image using toner, a transfer means for transferring the toner image to the recording material, and a fixing means for heating the toner image transferred to the recording material and fixing the toner image to the recording material, and a control means for controlling the image forming means, the fixing means having a cylindrical film, a heater disposed in an internal space of the film, and a roller that contacts an outer peripheral surface of the film and forms a fixing nip portion for heating the toner image while nipping and transporting the recording material together with the heater via the film, the image forming apparatus has a humidity detection means for detecting an environmental humidity of the image forming apparatus, and the control means is set to a default value. an image forming apparatus capable of switching between a first mode in which, when executing an image forming job for forming an image on a recording material, the image forming means outputs an image at a first throughput, and a second mode set by user selection, in which the process speed of the image forming means is the same as in the first mode, and the image can be output at a second throughput higher than the first throughput by making the interval between the recording materials being transported narrower than in the first mode, wherein the interval between the recording materials at the first throughput is longer than the circumference of the roller, and the interval between the recording materials at the second throughput is shorter than the circumference of the roller, and the control means outputs the image at the second throughput only when the second mode is selected and when certain conditions are satisfied, including a condition that the environmental humidity is equal to or lower than a threshold value. Effect of the Invention

[0008] According to the present invention, it is possible to provide an image forming apparatus capable of executing a mode that improves productivity while maintaining the stability of image output, according to a user's selection. [Brief description of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view of an image forming apparatus according to an embodiment of the present disclosure. [Diagram 2] FIG. 2 is a block diagram of a control system of the image forming apparatus. [Diagram 3] FIG. 2 is a cross-sectional view of a fixing device of the image forming apparatus. [Figure 4] FIG. 4 is a diagram showing a mode selection screen displayed on an operation panel in the first embodiment. [Diagram 5] 11 is a flowchart showing a process of determining a throughput in the first embodiment. [Figure 6] 11 is a flowchart showing a process of determining a throughput in the second embodiment. [Figure 7] 13 is a flowchart showing a process of determining a throughput according to the third embodiment. [Figure 8] 13 is a flowchart showing a process of determining a throughput according to the fourth embodiment. [Figure 9] FIG. 13 is a schematic diagram of a media sensor in the fifth embodiment. [Figure 10] 13 is a flowchart showing a process of determining a throughput according to the fifth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings. EXAMPLES

[0011] (1) Image forming device 1 is a cross-sectional view of an image forming apparatus according to a first embodiment of the present disclosure. This image forming apparatus is an electrophotographic laser beam printer (hereinafter, simply referred to as printer 203). Unless otherwise specified, the mechanical configuration of printer 203 and the basic flow of image forming operations described below are common to the other second to fifth embodiments.

[0012] The printer 203 includes a print engine 212 as an image forming means for forming an image on a recording material P. The recording material P can be a variety of sheets of different sizes and materials, including paper such as plain paper and thick paper, sheet materials with surface treatments such as plastic film, cloth, and coated paper, and sheet materials with special shapes such as envelopes and index paper.

[0013] The print engine 212 includes an electrophotographic mechanism consisting of a process cartridge 15, a laser exposure device 10, a transfer roller 16, and a fixing device 22, and a recording material transport mechanism that feeds recording material P one sheet at a time and discharges the recording material P after image formation outside the device. The process cartridge 15 includes a photosensitive drum 11, a charging roller 12, and a developing device 13. The recording material transport mechanism includes transport members for transporting the recording material P, such as a feed cassette 17, a feed roller 18, and a transport roller 19, as well as guide members such as a transport metal plate that forms a transport path for the recording material P. An image forming operation by the print engine 212 will be described below while touching on the components of the print engine 212.

[0014] The photosensitive drum 11 as an image carrier is a drum-shaped electrophotographic photosensitive body, and an organic photosensitive drum having a photosensitive layer of an organic photoconductor formed on the outer peripheral surface of a conductive drum base such as aluminum is used. A charging roller 12 as a charging means uniformly charges the surface of the photosensitive drum 11 to a predetermined polarity and potential. A laser exposure device 10 as an exposure means performs scanning exposure by irradiating the surface of the photosensitive drum 11 charged by charging with a laser beam L modulated in response to image information input from an external device such as an image scanner or computer (not shown). As a result, the surface charge of the photosensitive drum 11 is attenuated or removed, and an electrostatic latent image corresponding to the image information is formed. A developing device 13 as a developing means has a developing roller 13a that carries a developer containing toner, and this developing roller 13a visualizes (develops) the electrostatic latent image on the surface of the photosensitive drum 11 as a toner image.

[0015] The recording materials P are stored in a stacked state in the feeding cassette 17. When the feeding roller 18 rotates based on a feeding start signal, the recording materials P in the feeding cassette 17 are fed. The fed recording materials P are conveyed by the conveying roller 19 through a conveying path 20 to the registration roller 21. At this time, a separating member abutting the conveying roller 19 applies frictional force to other recording materials P overlapping the recording material P to be fed, so that the recording materials P are conveyed from the conveying roller 19 in a separated state one by one.

[0016] The registration roller 21 conveys the recording material P at a predetermined controlled timing to a transfer portion T, which is a nip portion between the photosensitive drum 11 and a transfer roller 16. The recording material P introduced into the transfer portion T is sandwiched and conveyed in this transfer portion T, during which the toner image carried on the photosensitive drum 11 is electrostatically transferred in sequence onto the surface of the recording material P by the transfer roller 16 as a transfer means. Note that a media sensor 5 for detecting the properties of the recording material can be arranged near the registration roller 21.

[0017] The recording material P to which the toner image has been transferred at the transfer portion T is separated from the surface of the photosensitive drum 11 and then introduced into the fixing device 22 through a conveying sheet metal 26, where the toner image is subjected to a heat fixing process. The detailed configuration of the fixing device 22, which is an example of a fixing means, will be described later. Meanwhile, the surface of the photosensitive drum 11 after separation of the recording material (after the toner image has been transferred to the recording material) is cleaned by removing residual toner and paper powder by a cleaning blade 14a of a cleaning device 14, and is used repeatedly for image formation. In this embodiment, the four process devices, the photosensitive drum 11, the charging roller 12, the developing device 13, and the cleaning device 14, are collectively configured as a process cartridge 15 that is detachable and replaceable with respect to the printer body.

[0018] The recording material P that has passed through the fixing device 22 is sent to the discharge rollers 24 by the conveying rollers 23. In the case of single-sided printing, the recording material P is discharged by the discharge rollers 24 onto a discharge tray 25 on the top of the printer. In the case of double-sided printing, the recording material P, which has had a toner image transferred to its first side and has been subjected to a fixing process, is partially discharged outside the printer body, and after the trailing end of the recording material leaves the nip of the conveying rollers 23, the discharge rollers 24 perform reverse rotation drive. As a result, the recording material P is conveyed downward along the conveying metal plate 27. The recording material P that has been drawn back into the printer body in this way is then sandwiched in the nip of the double-sided reversing rollers 28 and conveyed along the conveying metal plate 29 to the double-sided conveying rollers 30. The double-sided conveying rollers 30 further convey the recording material P along the conveying metal plate 31 and send it to the re-feed rollers 32. The recording material P is again sent to the registration roller 21 along the conveying metal plate 33 by the re-feed roller 32, and an image is formed on the second side through a process similar to that on the first side, and this time the discharge roller 24 is discharged onto the discharge tray 25 without performing reverse rotation drive.

[0019] 2 is a block diagram of a control system for the printer 203 of this embodiment. The hardware configuration of the image forming system according to this embodiment is configured by a host computer 200 and a printer 203 as external devices, as shown in FIG. 2. The host computer 200 has a main body section 201 that instructs the printer 203 to print via a network, and an operation display section 202. Here, the operation display section 202 of the host computer 200 includes a display, a keyboard, a mouse, etc., which are not shown. An example of the host computer 200 is a personal computer in which driver software is installed that receives data from an application such as a word processing software provided in the host computer 200 and generates a print instruction for the printer 203.

[0020] The printer 203 is composed of an operation display unit 205, a video controller 204, and an engine control unit 206. Here, the operation display unit 205 of the printer 203 includes the operation display unit 205 and operation buttons of FIG. 1. The video controller 204 transmits print data (image information to be printed) and print instructions received from the host computer 200 to the engine control unit 206. The engine control unit 206 is composed of a CPU 207, a ROM 208, and a RAM 209. The CPU 207 loads programs and various data into the ROM 208 and executes the programs by using the RAM 209 as a working area. The actuators (motors, solenoids, etc.) and power circuits that drive the components of the print engine 212 described above are accessible to an IO port 211 via a bidirectionally accessible system bus 210.

[0021] The CPU 207 realizes recording material conveyance and image formation by controlling these actuators and power circuits via the IO port 211. In this way, the CPU 207 executes a print job (image forming job), which is a series of operational tasks for outputting images onto a predetermined number of recording materials based on image information and print instructions received from the host computer 200. The video controller 204 and the engine control unit 206 function as control means of this embodiment that cooperate to control the operation of the printer 203.

[0022] (2) Fixing device 3 is a cross-sectional view of the fixing device 22 in this embodiment. The fixing device 22 is an image heating device of a film heating type, which includes a film , a stay , a heater 37, and a pressure roller .

[0023] The film 36, which serves as a heating body for heating an image on a recording material, is configured so that a part of its circumference is always tension-free and is rotated by the rotational driving force of the pressure roller 40, which serves as a pressure member. Specifically, the film 36 is supported by a stay 35, which serves as a heating body support member and a film guide member, and has a circumference that is longer than the area occupied by the stay 35 when viewed from the longitudinal direction (the axial direction of the pressure roller 40, the recording material width direction perpendicular to the recording material conveying direction P). The stay 35 is a rigid member made of heat-resistant resin and has a cross section in the shape of a trough, which is approximately semicircular, and whose longitudinal direction is a direction intersecting with the recording material conveying direction X. In this embodiment, a highly heat-resistant liquid crystal polymer is used as the material for the stay 35.

[0024] The heater 37 as a heating element is fixed and supported in a state of being fitted into a groove portion 35a provided on the lower surface of the stay 35 along the longitudinal direction of the stay 35. The heater 37 can be a ceramic heater in which a resistance heating element is formed on a ceramic substrate. For the ceramic substrate, for example, a material having electrical insulation, high thermal conductivity, and low heat capacity, such as alumina or aluminum nitride, is used. Then, a resistance heating element such as Ag / Pd (silver palladium) is formed on one surface of the ceramic substrate (the surface facing the fixing film) along the longitudinal direction of the substrate (the direction perpendicular to the paper surface of FIG. 3, the recording material width direction) by screen printing or the like. Furthermore, the surface on which the resistance heating element is formed is covered with a thin glass coating layer to form a ceramic heater. In this ceramic heater, when electricity is applied to the resistance heating element from a power supply device (not shown) via a power supply unit, the resistance heating element generates heat and the entire heater including the ceramic substrate and the glass coating layer is rapidly heated.

[0025] The temperature rise of the heater 37 is detected by a thermistor 50 as a temperature detection means installed on the back surface of the heater, and is fed back to a current control unit (not shown). The current control unit controls the power supply to the resistance heating element so that the heater temperature detected by the thermistor 50 is maintained at a predetermined temperature.

[0026] The film 36 as a flexible member is a cylindrical member with excellent heat resistance, and is loosely fitted around the stay 35. The film 36 has a total thickness of 100 μm or less in order to reduce heat capacity and improve quick start performance. Specific examples of the film 36 include a single layer of PTFE, PFA, or FEP, which has heat resistance, releasability, strength, and durability. Alternatively, a composite layer film in which the outer surface of polyimide, polyamide-imide, PEEK, PES, PPS, or the like is coated with PTFE, PFA, FEP, or the like can be used. However, PTFE is polytetrafluoroethylene, PFA is perfluoro(alkyl vinyl ether)-tetrafluoroethylene plastic, and FEP is perfluoro(ethylene-propylene) plastic. PEEK is polyether ether ketone, PES is polyether succinate, and PPS is polyphenylene sulfide.

[0027] In this embodiment, a polyimide film having a diameter of 24 mm and a thickness of 50 μm coated with PTFE having a thickness of 10 μm, resulting in a total thickness of 60 μm, was used as the heat-resistant film 36. Grease was applied to the inner peripheral surface side of the film 36 to improve sliding properties.

[0028] The pressure roller 40 as a backup member is formed by forming an elastic layer 42, which is made of insulating silicone solid rubber, silicone sponge rubber, etc., or conductive by dispersing a conductive agent, on a core metal 41 made of a metal such as iron or aluminum. A fluororesin layer is formed on the elastic layer 42 as a release layer 43. In this embodiment, a pressure roller having a diameter of 20 mm is used, which is made by forming an insulating silicone sponge rubber layer having a thickness of 3.5 mm on an iron core metal having a diameter of 13 mm and covering it with a conductive PFA tube having a thickness of 20 μm. The pressure roller 40 is a member whose longitudinal direction is a direction intersecting with the recording material conveying direction X, and both longitudinal ends of the core metal 41 are rotatably held by side plates constituting the frame of the fixing device 22 via bearing members.

[0029] The pressure roller 40 is pressed against the film 36 with a pressure of about 127 N (13 kgf) by a pressure spring (not shown). That is, a predetermined pressure is applied between the stay 35 that holds the heater 37 and the pressure roller 40, and a nip portion (fixing nip portion) N of a predetermined width is formed between the heater 37 and the pressure roller 40 with the film 36 sandwiched between them. The driving force of the rotation drive mechanism M is transmitted to a drive gear provided at the end of the core metal 41 of the pressure roller 40, so that the pressure roller 40 rotates at a predetermined peripheral speed in the direction of the arrow. The rotation of the pressure roller 40 causes a rotational force to act on the film 36 due to the frictional force between the pressure roller 40 and the surface of the film 36 at the nip portion N. The film 36 rotates around the stay 35 in the direction of the arrow at a peripheral speed substantially equal to the rotational peripheral speed of the pressure roller 40 while its inner side slides against the surface of the heater 37 at the nip portion N. The stay 35 also serves as a guide member for the film 36 that rotates.

[0030] When performing the fixing process, the temperature of the heater 37 rises to a predetermined target temperature (fixing temperature), and in a state in which the rotational circumferential speed of the film 36 is stabilized, the recording material P carrying a toner image is introduced along the fixing inlet guide 45 between the film 36 and the pressure roller 40. Then, the recording material P is sandwiched and conveyed together with the film 36 at the nip portion N, so that the heat of the heater 37 is imparted to the recording material P via the film 36. As a result, the unfixed toner image t on the recording material P melts, and then cools and solidifies, thereby being fixed to the surface of the recording material P. The recording material P that has passed through the nip portion N is separated from the surface of the film 36 and conveyed to the conveying roller 23.

[0031] 1, the printer 203 of this embodiment is equipped with the temperature and humidity sensor 2 and can detect the environmental temperature and humidity as the environmental conditions of the environment in which the printer 203 is used. In other words, the temperature and humidity sensor 2 is a humidity detection unit that detects the environmental humidity of the image forming apparatus, and is also a temperature detection unit that detects the environmental temperature of the image forming apparatus.

[0032] (3) Operation mode of the image forming device Next, the operation modes of the image forming apparatus will be described. The printer 203 according to this embodiment has a plurality of operation modes so that the functions and characteristics of the printer 203 can be customized according to the purpose of use of the user.

[0033] In the "normal mode", which is the default operating mode of the printer 203, the process speed, which is the operating speed of the image formation process, is set to 232 mm / sec, and the paper spacing (the distance between recording materials during continuous printing) is set to 70 mm. The normal mode is the first mode in this embodiment. When performing continuous printing in the normal mode, it is possible to print 38 sheets per minute for A4 size recording materials, and 40 sheets per minute for LTR size recording materials. This number of prints that can be output per minute is called the throughput, and will be expressed hereinafter in units of ppm (pages per minute).

[0034] The default operation mode refers to the operation mode that is set when the image forming apparatus has multiple operation modes that can be set by the user and the user has not performed any setting operation (initial state). In addition, in the case where the configuration allows the user to perform an operation to reset the multi-purpose mode setting described below, the default operation mode is automatically re-set by the reset operation.

[0035] In this embodiment, the user can select the multi-purpose mode from the operation display unit 205 of the printer 203 in Fig. 1. Fig. 4 shows a display screen (mode selection screen) displayed on the display of the operation display unit 205. The user selects "productivity improvement mode" from among a plurality of modes according to the instructions on the mode selection screen, and presses the OK button 205a, whereby the productivity improvement mode is set as the operation mode of the printer 203. The productivity improvement mode is a second mode in this embodiment that can improve throughput compared to the first mode.

[0036] In the productivity improvement mode of this embodiment, the A4 size throughput can be improved from 38 ppm to 40 ppm by changing the paper pitch from 70 mm to 48 mm. In other words, when A4 size is used as the standard, the first throughput in this embodiment is 38 ppm and the second throughput is 40 ppm. Also, the LTR size throughput can be improved from 40 ppm in the normal mode to 42.5 ppm. In this embodiment, the process speed in the productivity improvement mode is 232 mm / sec, the same as in the normal mode.

[0037] In addition to the productivity improvement mode, the printer 203 of this embodiment also has a fixability improvement mode, a curl reduction mode, and a quiet mode as multi-purpose modes. The fixability improvement mode is a mode in which the fixing temperature is increased without changing the throughput from the normal mode, and it is possible to improve the fixability of the image on the recording material. The curl reduction mode is a mode in which the paper gap is significantly wider than in the normal mode, and in exchange for allowing a decrease in throughput, it is possible to reduce the curl of the recording material. The quiet mode is a mode in which the process speed is changed to half the speed of the normal mode, and in exchange for allowing a decrease in throughput, it is possible to suppress the operating noise of the printer 203 during image formation. The curl reduction mode and the quiet mode are examples of the third mode in which the throughput is decreased to a third throughput lower than the first throughput compared to the first mode, but in exchange for this, functions other than the throughput can be added or improved.

[0038] In the curl reduction mode, curling is reduced by significantly widening the paper gap because the temperature difference between the heater 37 (FIG. 2) and the pressure roller 40 becomes sufficiently small between the time when the previous recording material passes through the fixing nip and the time when the next recording material enters. In other words, in the normal mode where the paper gap is relatively short, the temperature of the pressure roller 40 gradually decreases during continuous printing, and a difference in the amount of heat applied to the front and back of the recording material occurs. In this case, for example, if an image is formed on a recording material that has been left in a high-humidity environment for a long time, a difference in the amount of moisture that causes curling occurs between the front and back sides of the recording material that has passed through the fixing nip. In contrast, in the curl reduction mode, heat is applied almost evenly to the front and back of the recording material, so curling is suppressed.

[0039] In the productivity improvement mode, curl reduction mode, etc., "widening the paper gap" compared to the normal mode specifically includes changing the following settings. The interval at which an exposure start signal is generated, which instructs the laser exposure device 10 to start writing a latent image, is made longer than in the normal mode. The interval at which a feed start signal is generated, which instructs the feed roller 18 to start feeding the recording material, is made longer than in the normal mode. The interval at which a registration ON signal is generated, which instructs the registration rollers 21 to start conveying the recording material to the transfer portion T, is made longer than in the normal mode.

[0040] Furthermore, "changing the process speed" in a print job in quiet mode or the like includes changing the following settings, for example. The rotation speeds of the photosensitive drum 11 and the pressure roller 40 are set to the changed process speed. The conveying speed of the recording material by the registration rollers 21 is set to a speed corresponding to the changed process speed.

[0041] The multi-purpose mode can also be selected by the user from the operation display unit 202 (e.g., a display or keyboard of a personal computer) of the host computer in Fig. 2. Although the case where the user selects the multi-purpose mode has been described here, the operation for selecting the mode can also be performed by someone other than the user (e.g., a sales representative or a service representative).

[0042] (4) Productivity Improvement Mode Details Incidentally, although the productivity improvement mode aims to improve throughput, there are cases where it is not appropriate to shorten the paper interval compared to the normal mode. For example, if the paper interval is set to be short in a high humidity environment, the temperature of the fixing members such as the film 36 and pressure roller 40 that perform the fixing process drops, and eventually water droplets begin to adhere to the fixing members. This causes a significant decrease in the frictional force on the surface of the fixing members, making it impossible to transport the recording material at a specified speed. This phenomenon is called condensation slip, and when condensation slip occurs, it can cause a disturbance in the toner image or a jam (paper jam) due to a delay in the transport of the recording material.

[0043] In normal mode, the paper interval is 70 mm, which is greater than the outer circumference of the pressure roller with a diameter of 20 mm (approximately 63 mm), and the pressure roller temperature does not drop easily during continuous printing. In other words, the paper interval in normal mode is set to suppress degradation of image quality and jams caused by condensation slippage, regardless of humidity conditions.

[0044] On the other hand, when the paper gap is changed to 48 mm in the productivity improvement mode, the amount of rotation of the pressure roller 40 during the period from when the previous recording material passes through the fixing nip until the next recording material enters is less than one rotation. In other words, after the previous recording material passes, the next recording material reaches the fixing nip before the film 36 applies heat to the entire circumference of the pressure roller 40, and the temperature of the pressure roller 40 is likely to drop. Therefore, if the paper gap is set to 48 mm under high humidity conditions, condensation may occur on the surface of the pressure roller during continuous printing.

[0045] Therefore, in this embodiment, even if the "productivity improvement mode" is selected, the paper gap is actually changed to 48 mm only when the temperature and humidity sensor 2 detects that the humidity is 60% Rh or less. In other words, in this embodiment, the throughput is improved compared to the normal mode only when the environmental humidity is equal to or less than a predetermined threshold value as a predetermined condition.

[0046] (5) Productivity improvement mode decision process Fig. 5 is a flowchart showing the productivity improvement mode determination process in this embodiment. Note that the productivity improvement mode determination process, including the flowcharts (Figs. 6 to 8 and 10) described in the second and subsequent embodiments, is executed by the CPU 207 (Fig. 2) at the start of a print job.

[0047] First, in step S11, it is checked whether the productivity improvement mode is selected. If the productivity improvement mode is not selected, the process proceeds to step S12, and the print job is executed in the normal mode, that is, with the paper interval set to 70 mm. If the productivity improvement mode is selected in step S11, the process proceeds to step S13, and it is checked whether the humidity is 60% Rh or less based on the detection result of the temperature and humidity sensor 2. If the humidity exceeds 60% Rh, which is the threshold value in this embodiment, there is a possibility of condensation slippage occurring, so the process proceeds to step S14, and the print job is executed with the paper interval of 70 mm, which is the same as in the normal mode. In this case, the throughput is the same as in the normal mode. If the detection result of the temperature and humidity sensor 2 is the humidity threshold value of 60% Rh or less, the process proceeds to step S15, and the paper interval is changed to 48 mm and the print job is executed. At this time, the throughput is greater than in the normal mode, and the productivity is improved.

[0048] In this embodiment, although a condition is set for activating the productivity improvement mode (i.e., applying a higher throughput than the normal mode), the humidity in a typical office environment where the printer 203 is used is often 60% Rh or less. Therefore, the majority of users can enjoy improved throughput by selecting the productivity improvement mode. Even if the environment in which the printer 203 is installed is highly humid, the paper gap is set to 70 mm, the same as in the normal mode, in that case, and it is possible to avoid the occurrence of condensation slippage. This makes it possible to maximize the productivity of the printer 203 while avoiding problems caused by the special usage environment of the printer 203.

[0049] Furthermore, if the user does not select the productivity improvement mode, the printer 203 outputs images at a constant throughput regardless of the humidity conditions in the normal mode set by default. In this case, it is possible to avoid the occurrence of condensation slip even if there is an abnormality in the temperature and humidity sensor 2. Also, for users who do not require improved productivity, the fact that images are always output at a constant throughput can contribute to improving the usability of the image forming apparatus in that there is no discrepancy between the throughput expected by the user and the actual throughput. EXAMPLES

[0050] In the second embodiment, a configuration will be described in which the process speed is changed in the productivity improvement mode to improve throughput compared to the normal mode, and the productivity improvement mode is activated under conditions different from those in the first embodiment. Note that the mechanical configurations of the printer 203 and the fixing device 22 and the basic flow of the image forming operation are common to the first embodiment. Hereinafter, elements with the same reference numerals as those in the first embodiment have substantially the same configurations and functions as those described in the first embodiment.

[0051] In the printer 203 of this embodiment, in the "normal mode" which is the default operating mode, the process speed is set to 232 mm / sec and the paper interval is set to 35 mm. When performing continuous printing in this normal mode, a throughput of 42 ppm for A4 size and 44 ppm for LTR size is achieved.

[0052] In this embodiment, when the user selects the "productivity improvement mode" from the operation display unit 202 of the host computer or the operation display unit 205 of the printer in FIG. 2, the process speed is changed from 232 mm / sec to 280 mm / sec. When continuous printing is performed in this productivity improvement mode, the throughput of A4 size is improved from 42 ppm to 50.5 ppm. In other words, when A4 size is used as a standard, the first throughput in this embodiment is 42 ppm and the second throughput is 50.5 ppm. Furthermore, when continuous printing is performed in the productivity improvement mode, the throughput of LTR size is improved from 44 ppm to 53.5 ppm. In addition to increasing the process speed, in this embodiment, the fixing temperature is increased by 20° C. to maintain fixability, and the transfer voltage is adjusted so as not to impair image quality.

[0053] However, when double-sided printing is performed with the fixing temperature increased by 20°C, the temperature rise inside the printer during continuous printing becomes large, and toner blocking, in which toner particles stick together in the developing container of the developing device 13, may occur. This occurs because the recording material, which has become hotter after passing through the fixing nip when printing the first side, is transported again through the printer for printing the second side, causing the temperature inside the sealed developing container to rise, causing the toner before development to enter a semi-molten state. Once toner blocking occurs, development becomes difficult, and there is a risk that it will no longer be possible to output a normal image.

[0054] Therefore, even if the "productivity improvement mode" is selected, the process speed is changed to 280 mm / sec only in the case of single-sided printing. In other words, in this embodiment, the throughput is improved compared to the normal mode only when the print job is set to single-sided printing as a predetermined condition. The process speed in the normal mode is set to 232 mm / sec, which is a speed that can sufficiently suppress toner blocking even in the case of double-sided printing.

[0055] 6 is a flow chart showing the productivity improvement mode determination process in this embodiment. First, in step S21, it is checked whether the productivity improvement mode has been selected. If the productivity improvement mode has not been selected, the process proceeds to step S22, where the print job is executed in the normal mode, i.e., with the process speed set to 232 mm / sec. If the productivity improvement mode has been selected, the process proceeds to step S23, where it is checked whether the setting for the print job sent to the video controller 204 of the printer 203 is single-sided printing.

[0056] If the print job is set to double-sided printing rather than single-sided printing, there is a possibility of toner blocking occurring, so the process proceeds to step S24 and the print job is executed at the same process speed (232 mm / sec) as in normal mode. In this case, the throughput is the same as in normal mode. If the print job is set to single-sided printing, the process proceeds to step S25 and the process speed setting is changed to 280 mm / sec and the print job is executed. At this time, the throughput is greater than in normal mode, improving productivity.

[0057] In this embodiment, a user who mainly performs single-sided printing can improve productivity by selecting the productivity improvement mode. Even if a double-sided print job is submitted with the productivity improvement mode selected, the job is executed with the throughput suppressed to the same level as in the normal mode, so that the occurrence of toner blocking can be avoided. This makes it possible to maximize the productivity of single-sided printing, which is frequently used, while avoiding problems with double-sided printing. Furthermore, if the user does not select the productivity improvement mode, the advantages of the normal mode, which is set by default, can be obtained. EXAMPLES

[0058] In the third embodiment, a configuration for activating the productivity improvement mode under conditions different from those in the first and second embodiments will be described. The mechanical configurations of the printer 203 and the fixing device 22 and the basic flow of the image forming operation are common to those in the first embodiment. Also, in this embodiment, as in the second embodiment, the process speed is changed to improve the throughput more than in the normal mode. Hereinafter, elements with the same reference numerals as those in the first embodiment have substantially the same configurations and functions as those described in the first embodiment.

[0059] First, the relationship between the environmental temperature and the quality of the image formation product will be described. When continuous printing is performed in a high-temperature environment with a high throughput, the recording materials after the fixing process are stacked one after another on the discharge tray while still at a high temperature, and heat is trapped in the sheet stack. This causes the toner to remelt, resulting in the toner sticking between the recording materials. This phenomenon is called discharge sticking, and when the stuck recording materials are peeled off, it causes the toner image to be lost and the back of the recording materials to be stained. Conversely, when continuous printing is performed in a low-temperature environment with a high throughput, the power supplied to the heater 37 is insufficient, making it impossible to reach the specified fixing temperature, which can cause fixing failure. In order to avoid these situations, it is known that it is effective to slow down the drive speed of the fixing member, lower the fixing temperature, and take a considerable amount of time for the fixing process.

[0060] In the normal mode of this embodiment, the process speed is set to 232 mm / sec. This value is selected so that ejected paper sticking and fixing failure do not occur even in high or low temperature environments within the expected range in the printer 203 of this embodiment.

[0061] Here, in the case of the printer 203 of this embodiment, there was a risk of the aforementioned ejected paper sticking occurring when continuous printing was performed in a high temperature environment with a process speed of 280 mm / sec and a fixing temperature 20° C. higher than that in the normal mode of embodiment 1. Also, in a low temperature environment, when printing was performed with a process speed of 280 mm / sec and a fixing temperature 20° C. higher, there was a risk of poor fixing occurring because the power required for fixing was insufficient and the target fixing temperature could not be reached.

[0062] Therefore, in this embodiment, even if the "productivity improvement mode" is selected, the process speed is changed to 280 mm / sec only when the temperature is between 17° C. and 30° C. In other words, in this embodiment, the throughput is improved compared to the normal mode only when the environmental temperature is within a predetermined range as a predetermined condition.

[0063] 7 is a flow chart showing the productivity improvement mode determination process in this embodiment. First, in step S31, it is checked whether the productivity improvement mode has been selected. If the productivity improvement mode has not been selected, the process proceeds to step S32 and the print job is executed in normal mode, i.e., with the process speed set to 232 mm / sec. If the productivity improvement mode has been selected, the process proceeds to step S33 and it is checked whether the environmental temperature is between 17° C. and 30° C. based on the detection result of the temperature and humidity sensor 2.

[0064] If the environmental temperature is below 17°C or above 30°C, there is a possibility of poor fixing or paper sticking, so the process moves to step S34 and the print job is executed at the same process speed of 232 mm / sec as in normal mode. In this case, the throughput is the same as in normal mode. If the temperature and humidity sensor detects that the environmental temperature is between 17°C and 30°C, the process moves to step S35 and the process speed is changed to 280 mm / sec and the print job is executed. In this case, the throughput is greater than in normal mode, improving productivity.

[0065] In this embodiment, although a condition for activating the productivity improvement mode is set, since the temperature in a typical office environment where a printer is used is often between 17°C and 30°C, the majority of users can improve their productivity by using this productivity improvement mode. Even if a print job is input in a low-temperature or high-temperature environment with the productivity improvement mode selected, the same process speed as in the normal mode is applied, so that the occurrence of poor fixing or paper sticking on the output paper can be avoided. This makes it possible to maximize the productivity of the printer 203 while avoiding problems caused by the special usage environment of the printer 203. Furthermore, if the user does not select the productivity improvement mode, the advantages of the normal mode set by default can be obtained. EXAMPLES

[0066] In the fourth embodiment, a configuration is described in which the productivity improvement mode is activated under conditions different from those in the first to third embodiments. The mechanical configurations of the printer 203 and the fixing device 22 and the basic flow of the image forming operation are common to those in the first embodiment. In addition, in this embodiment, as in the second and third embodiments, the process speed is changed to improve the throughput more than in the normal mode. Hereinafter, elements with the same reference numerals as those in the first embodiment have substantially the same configurations and functions as those described in the first embodiment.

[0067] The printer 203 of this embodiment is connected to a host computer 200 (FIG. 2), such as a personal computer. When image information and a print instruction are sent from the host computer 200 to a video controller 204, an engine control unit 206 executes a print job based on the instruction from the video controller 204.

[0068] Here, the video controller 204 includes an image data detection unit. The image data detection unit obtains the coverage rate of the toner image for each image formed on one sheet of recording material from the print data received from the host computer 200. The CPU 207 of the engine control unit 206 then obtains the printing rate of the toner image based on these values, determining that a rate of less than 60% is low printing and a rate of 60% or more is high printing. The printing rate refers to the ratio of the area on the recording material where the toner constituting the toner image is attached to the area (effective printing area) where the print engine 212 (FIG. 1) can form an image. In the case of high printing, the fixing temperature is increased by 10°C.

[0069] In this embodiment, when high-power printing is performed at a process speed of 280 mm / sec, a large amount of toner needs to be melted, and therefore the amount of heat applied from the fixing member to the recording material may be insufficient, causing poor fixing, which may significantly reduce image quality. Note that the process speed in the normal mode is set to 232 mm / sec, which is a speed that can sufficiently suppress poor fixing regardless of the print rate.

[0070] Therefore, even if the "productivity improvement mode" is selected, the process speed is changed to 280 mm / sec only in the case of low printing with a print rate of less than 60%. The process speed in normal mode is 232 mm / sec, the same as in embodiments 2 and 3. In other words, in this embodiment, the predetermined conditions include conditions based on the image information to be printed (image conditions), and the throughput is improved compared to the normal mode only when the print rate is less than the threshold value.

[0071] When performing continuous printing, the process speed is not changed for each recording material, but rather, for example, the maximum value of the printing rate of each image output by the current print job is used to determine whether the printing rate is high or low. This makes it possible to avoid poor fixing for all output images even when some images in a job are high printing and other images are low printing.

[0072] 8 is a flow chart showing the productivity improvement mode determination process in this embodiment. First, in step S41, it is checked whether the productivity improvement mode has been selected. If the productivity improvement mode has not been selected, the process proceeds to step S42, where the print job is executed in normal mode, i.e., with the process speed set to 232 mm / sec. If the productivity improvement mode has been selected, the process proceeds to step S43, where it is checked whether the print ratio is less than 60% based on the image data sent to the printer's video controller 204.

[0073] If the printing rate is 60% or more, there is a possibility of poor fixing, so the process moves to step S44 and the print job is executed at the same process speed of 232 mm / sec as in normal mode. In this case, the throughput is the same as in normal mode. If the printing rate is less than 60%, the process moves to step S45 and the process speed is changed to 280 mm / sec and the print job is executed. At this time, the throughput is greater than in normal mode, improving productivity.

[0074] In this embodiment, although the conditions for activating the productivity improvement mode are set, since the images printed on the recording material are often mostly text images, the productivity improvement mode can be used by most users to improve their productivity. Even if a high-printing print job is submitted with the productivity improvement mode selected, the same process speed as in the normal mode is applied, so that the occurrence of poor fixing can be avoided. This makes it possible to maximize the productivity of low-printing prints of commonly used text documents while avoiding problems caused by high-printing. Furthermore, if the user does not select the productivity improvement mode, the advantages of the normal mode set as the default can be obtained. EXAMPLES

[0075] In the fifth embodiment, a configuration is described in which the productivity improvement mode is activated under conditions different from those in the first to fourth embodiments. The mechanical configurations of the printer 203 and the fixing device 22 and the basic flow of the image forming operation are common to those in the first embodiment. In addition, in this embodiment, as in the second to fourth embodiments, the process speed is changed to improve the throughput more than in the normal mode. Hereinafter, elements with the same reference numerals as those in the first embodiment have substantially the same configurations and functions as those described in the first embodiment.

[0076] The printer 203 of this embodiment is equipped with a media sensor 5 (FIG. 1) as a detection means for detecting the properties of the recording material. The media sensor 5 is capable of detecting the thickness (grammage), surface roughness, type of recording material, etc. of the recording material so that the printer 203 can optimize the image formation conditions based on the detection results of the media sensor 5 without the user having to make complicated settings for various recording materials. Then, using the information on the recording material detected by this media sensor 5, the set values ​​of the transfer voltage and the fixing temperature during image formation are optimized.

[0077] An optical sensor that utilizes the fact that the thicker the recording material (the greater the basis weight), the less light passes through it can be used as the media sensor 5. Also, the media sensor 5 is disposed immediately behind the registration rollers 21 (FIG. 1) so that the measurement is performed while the position of the recording material is relatively stable.

[0078] 9 is a diagram for explaining a schematic configuration of the media sensor 5. The media sensor 5 uses an LED 55 as a light emitting means and a phototransistor 52 as a light receiving means, and is capable of detecting the thickness of the recording material P using the ratio (transmittance) between the amount of light emitted by the LED 55 irradiating the back surface of the recording material and the amount of light received by the phototransistor 52. For example, the CPU 207 can determine the basis weight of the recording material P by acquiring the transmittance value from the media sensor 5 and referring to a table showing the correspondence between basis weight categories and transmittance.

[0079] Moreover, the media sensor 5 of this embodiment is configured to simultaneously detect the surface roughness of the recording material P in addition to the thickness. That is, the media sensor 5 has an irradiation LED 51 as an irradiation means for irradiating the surface of the recording material P with light, and an imaging lens 53 as an imaging means for receiving the reflected and scattered light irradiated from the irradiation LED 51 and reflected by the surface of the recording material P and forming an image on a light receiving means (not shown). The media sensor 5 is capable of detecting the surface roughness of the recording material P based on the ratio (reflectance) between the amount of light emitted by the irradiation LED 51 and the amount of light received by a light receiving means such as a phototransistor. For example, the CPU 207 can determine whether the recording material P is a paper with a rough surface or a paper with a smooth surface by acquiring the reflectance value from the media sensor 5 and referring to a table showing the correspondence between the type of recording material based on the surface roughness and the reflectance. In general, the smoother the surface of the recording material, the higher the reflectance. Also, the rougher the surface of the recording material, the more disadvantageous it is in terms of transferability and fixability.

[0080] Note that, although a media sensor 5 having both the function of detecting the thickness (basis weight) of the recording material and the function of detecting the surface roughness of the recording material has been exemplified here, a media sensor having only one of these functions may also be used.

[0081] In this embodiment, the process speed is 280 mm / sec and the basis weight is 80 g / m 2 When outputting images onto paper of the above specifications, the amount of heat applied to the paper from the fixing member may be insufficient, causing poor fixing, which may result in a significant drop in image quality.The process speed in normal mode is set to 232 mm / sec, which is a speed that can sufficiently suppress the occurrence of poor fixing regardless of the basis weight within the range of basis weights expected to be used.

[0082] Therefore, even if the "productivity improvement mode" is selected, the process speed is changed to 280 mm / sec when the basis weight of the recording material detected by the media sensor 5 is 80 g / m 2That is, in this embodiment, the predetermined conditions include conditions based on information about the recording material used in image output (recording material conditions), and the throughput is improved compared to the normal mode only when the basis weight is less than the threshold value (smaller than the threshold value).

[0083] 10 is a flow chart showing the productivity improvement mode judgment process in this embodiment. First, in step S51, it is checked whether the productivity improvement mode has been selected. If the productivity improvement mode has not been selected, the process proceeds to step S52, where the print job is executed in normal mode, i.e., with the process speed set to 232 mm / sec. If the productivity improvement mode has been selected, the process proceeds to step S53, where the detection result of the media sensor 5 indicates that the basis weight of the recording material is 80 g / m 2 Check if it is less than.

[0084] The recording material has a basis weight of 80 g / m 2 If the value is more than this, there is a possibility of poor fixing, so the process proceeds to step S54 and the print job is executed at the same process speed of 232 mm / sec as in the normal mode. In this case, the throughput is the same as in the normal mode. 2 If it is less than this, the process proceeds to step S55, where the process speed is changed to 280 mm / sec and the print job is executed, resulting in a higher throughput than in the normal mode and improved productivity.

[0085] As described above, in this embodiment, the basis weight is 80 g / m 2 Users who use plain paper with a thickness of less than 100 mm can improve their productivity by using the productivity improvement mode. When thick paper is used with the productivity improvement mode selected, the same process speed as in the normal mode is applied, so that poor fixing can be prevented. This makes it possible to maximize the productivity of normally used plain paper while preventing problems that occur when using thick paper. Furthermore, if the user does not select the productivity improvement mode, the advantages of the normal mode, which is set by default, can be obtained.

[0086] As a modification of this embodiment, it may be possible to determine whether or not to apply the process speed (280 mm / sec) of the productivity improvement mode based on the surface roughness detected by the media sensor 5. In this case, the process speed is set to 280 mm / sec when the detection result of the media sensor 5 indicates that the recording material used for the current print job can be classified as "smooth paper." In other words, in this modification, the type of recording material that falls under a predetermined type of smooth surface is used as a predetermined condition for whether or not to apply a throughput higher than that of the normal mode. This configuration also makes it possible to improve productivity with smooth paper such as copy paper, while avoiding poor transfer and fixing problems when paper with a rough surface is used.

[0087] As another modified example, the condition of the basis weight of the recording material and the condition of the surface roughness may be used in combination as the predetermined condition for determining whether or not to apply a throughput higher than that in the normal mode.

[0088] (Other Examples) The conditions (predetermined conditions) for applying a higher throughput than the normal mode when the productivity improvement mode is selected, as exemplified in the above first to fifth embodiments, may be used in one image forming apparatus in any combination. For example, when the productivity improvement mode is selected, a higher throughput than the normal mode may be applied only when the environmental humidity is 60% Rh or less and the environmental temperature is 17°C or more and 30°C or less. As a method for combining a plurality of conditions as the predetermined condition, an AND condition may be used in which a higher throughput than the normal mode is applied only when all the conditions are satisfied. However, a higher throughput than the normal mode may be applied when some of the plurality of conditions set in advance are satisfied.

[0089] In addition, as a method for achieving a higher throughput in the productivity improvement mode than in the normal mode, the method for shortening the paper interval described in the first embodiment and the method for increasing the process speed described in the second to fifth embodiments may be used in combination.

[0090] 1, a direct transfer type laser beam printer has been described as an example of an image forming apparatus, but the present technology is not limited to this and can also be applied to an indirect transfer type image forming apparatus in which a toner image formed on an image carrier is transferred to a recording material via an intermediate transfer body, and an image forming apparatus equipped with other printing mechanisms such as an inkjet type.

[0091] (Other embodiments) The present invention can also be realized by a process in which a program for implementing one or more of the functions of the above-described embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. The present invention can also be realized by a circuit (e.g., ASIC) that implements one or more of the functions. [Explanation of symbols]

[0092] 10... exposure means (laser exposure device) / 11... image carrier (photosensitive drum) / 13... development means (developing device) / 16... transfer means (transfer roller) / 22... fixing means (fixing device) / 203... image forming apparatus (printer) / 204, 206... control means (video controller, engine control unit) / 212... image forming means (print engine)

Claims

1. An image forming apparatus comprising: an image forming means for forming an image on a recording material, the image forming means having an image carrier, an exposure means for exposing the image carrier to light to form an electrostatic latent image, a development means for developing the electrostatic latent image formed on the image carrier into a toner image using toner, a transfer means for transferring the toner image onto the recording material, and a fixing means for heating the toner image transferred onto the recording material to fix it onto the recording material; and a control means for controlling the image forming means, the fixing means includes a cylindrical film, a heater disposed in an internal space of the film, and a roller that contacts an outer peripheral surface of the film and forms a fixing nip portion that heats a toner image while nipping and conveying a recording material together with the heater via the film, the image forming apparatus has a humidity detection unit that detects an environmental humidity of the image forming apparatus, the control means is capable of switching between a first mode, which is set as a default and causes the image forming means to output an image at a first throughput when executing an image forming job for forming an image on a recording material, and a second mode, which is set by a user's selection, in which the process speed of the image forming means is the same as that of the first mode, and an image can be output at a second throughput higher than the first throughput by making an interval between conveyed recording materials narrower than that of the first mode; a distance between adjacent recording materials at the first throughput is longer than a circumferential length of the roller, and a distance between adjacent recording materials at the second throughput is shorter than a circumferential length of the roller; the control means causes the image to be output at the second throughput only when the second mode is selected and when predetermined conditions are satisfied, including a condition that the environmental humidity is equal to or lower than a threshold value.

1. An image forming apparatus comprising:

2. a temperature detection unit for detecting an environmental temperature of the image forming apparatus; the predetermined condition includes a condition that the environmental humidity is equal to or lower than the threshold value and the environmental temperature of the image forming apparatus is within a predetermined range.

2. The image forming apparatus according to claim 1,

3. the predetermined condition includes a condition that the environmental humidity is equal to or lower than the threshold value and the image forming job is set to form an image on only one side of a recording material.

3. The image forming apparatus according to claim 1, wherein the first and second electrodes are arranged in a first direction.

4. the predetermined condition includes a condition that the environmental humidity is equal to or lower than the threshold value and a printing ratio of an image to be formed on a recording material by the image forming job is less than a threshold value.

4. The image forming apparatus according to claim 1, wherein the first and second electrodes are arranged in a first direction.

5. the predetermined condition includes a condition that the environmental humidity is equal to or less than the threshold value and the basis weight of the recording material is less than a threshold value; 5. The image forming apparatus according to claim 1, wherein the first and second electrodes are arranged in a first direction.

6. the control means, when the second mode is selected and the image forming job is executed in a state in which the predetermined condition is not satisfied, causes the image forming means to output an image at the first throughput.

6. The image forming apparatus according to claim 1, wherein the first and second electrodes are arranged in a first direction.

7. the control unit is capable of selecting a third mode in which an image is output at a third throughput lower than the first throughput when the image forming job is executed, the third mode is a mode in which the interval between the recording materials is increased as compared with the first mode, thereby reducing curl of the recording materials on which the image is formed.

7. The image forming apparatus according to claim 1, wherein the first and second electrodes are arranged in a first direction.

Images