JP2006301260A - Color image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus that ensures excellent power consumption efficiency, in matching with the actual conditions for a printing form. <P>SOLUTION: The image forming apparatus can be driven at a plurality of processing speeds, and to print on usual regular paper, a regular paper mode in which 1/1 speed is assigned is used; whereas when a user sets a power saving mode through the printer driver 27 of a host computer D or a control panel 22 within the image forming apparatus A, image formation is carried out by first setting the processing speed to 1/2 speed and then setting a fixing temperature so as to obtain glossiness equal to that obtained in the regular paper mode. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a color image forming apparatus having a heat fixing means using an electrophotographic system or the like.

  Conventionally, a heat roller system has been widely used as a heat fixing device for recording materials in image forming apparatuses (see, for example, Patent Document 1). This system is basically composed of a fixing roller in which a core metal provided with a heater is coated with an elastic material such as silicone rubber, and a pressure roller in which a core metal in pressure contact is coated with an elastic material such as silicone rubber. A recording material is introduced and passed through a fixing nip portion formed by a pair of rollers to heat and press-fix the toner image.

  In general, such a heat roller system has a large heat capacity of the roller, so it takes a very long time to raise the roller surface to a temperature required for fixing, and it takes time to warm up the image forming apparatus. . For this reason, the first printout time (FPOT), which is the time from the start of printing until the recording material is discharged, becomes longer and makes the user wait.

Therefore, in order to shorten the FPOT, there is a method in which a standby mode in which the surface of the fixing roller is always heated in advance at a temperature lower than the fixing temperature is provided even when the main body is not used, so that the temperature can be quickly heated to the fixing temperature at the time of printing. It is taken.
JP-A-6-186874 (page 5, FIG. 1)

  However, as described above, the heat roller method generally requires a large electric power for heating because the heat capacity of the fixing roller is large. Further, in recent years, the speed of image forming apparatuses has been increased, and it is necessary to increase the amount of heat given to the recording material per unit time. Therefore, the temperature of the fixing roller has to be further increased, and the power required for heating has further increased. In addition to these, an image forming apparatus provided with the above-described standby mode always consumes a large amount of power even when printing is not being performed. Therefore, when a printing operation is not performed for a predetermined time, a sleep mode for stopping heating of the fixing device is further provided to suppress power consumption.

  On the other hand, a user does not always perform a large amount of printing, but may perform a small amount of printing on several sheets at intervals. In such a case, after fixing the image forming apparatus by heating the fixing roller to the fixing temperature, if the printing is not performed for a predetermined time, the image forming apparatus enters the sleep mode and the fixing apparatus is stopped from heating and the fixing roller is kept at room temperature The operation is repeated until it cools. As described above, since the fixing roller has a large heat capacity, once the temperature is raised to the fixing temperature, the temperature can be maintained without consuming a large amount of power thereafter. However, if a small amount of printing is performed at intervals, the power consumption becomes very inefficient such that the heated roller is heated again when it has cooled to room temperature. In addition, the time required for heating becomes very long, which makes the user wait.

  In view of the above situation, an object of the present invention is to provide a color image forming apparatus with good power consumption efficiency that matches the actual state of printing.

  In order to achieve the above-described object, the present invention has a color image forming apparatus having the following configurations (1) to (8).

(1) A color image forming apparatus comprising fixing means for obtaining a fixed image by heat-fixing a color toner image formed on a recording material, and capable of fixing at a plurality of fixing speeds.
The color toner is a toner containing wax, and when the same image is fixed on the same type of recording material at the entire fixing speed of the color image forming apparatus, at least two of the obtained fixed images are obtained. The color image forming apparatus is characterized in that the difference in glossiness between the primary colors is within 5 and the difference in glossiness between the secondary colors is within 10.

  (2) Of at least two fixing speeds for obtaining a fixed image in which the difference in glossiness between the primary colors is within 5 and the difference in glossiness between secondary colors is within 10, one is the fastest fixing speed. The color image forming apparatus as described in (1) above.

  (3) The fixing temperatures at at least two fixing speeds for obtaining a fixed image in which the difference in glossiness between the primary colors is within 5 and the difference in glossiness between secondary colors is within 10 are different. The color image forming apparatus according to (1).

  (4) In the color image forming apparatus, the difference in glossiness of the primary color is within 5 and the difference in glossiness of the secondary color is within 10 depending on the number of printed sheets from the start of the printing operation to the stop of the printing operation. The color image forming apparatus according to (1), wherein the fixing speed is selected from among at least two fixing speeds for obtaining a fixed image.

  (5) The color image forming apparatus according to (4), wherein the number of printed sheets from the start of the printing operation to the stop of the printing operation is measured by a host computer, a print server, or a controller in the image forming apparatus.

  (6) The color image according to (1), wherein the fixing unit is composed of two elastic rollers, and is a heat roller type fixing unit having a heating element in at least one of these elastic rollers. Forming equipment.

  (7) The fixing unit (1) is characterized in that the fixing unit has heat resistance and releasability, and is a fixing unit comprising an endless film sheet having a heating unit inside or outside and a pressing unit. The color image forming apparatus described.

  (8) The color image forming apparatus according to (1), wherein the image forming apparatus has a standby mode in which the fixing unit is maintained at a predetermined temperature lower than the fixing temperature during non-image formation.

  According to the invention of the present application, when a small amount of plain paper is printed at an interval, the fixing speed is lowered and the fixing temperature is lowered after the fixing speed is lower than that at the normal time so that the glossiness is equal to that at the normal time. Power consumption can be reduced while obtaining an image, and an image forming apparatus with high power consumption efficiency that matches the actual printing mode can be provided.

  The best mode for carrying out the present invention will be described below based on examples.

  FIG. 1 shows an example of an image forming apparatus according to the present invention. In FIG. 1, a color image forming apparatus A is connected to a host computer D via a stand-alone or network. In some cases, the color image forming apparatus A may be connected to a network via a print server (not shown) that temporarily stores print data.

  The color image forming apparatus A includes a controller unit B and an engine unit C. Image data created by application software or the like in the host computer D is output as print information through the printer driver 27 and sent to the controller unit B. The controller unit B performs processing such as color conversion and rasterization based on the received image data, and sends it to the engine unit C. A control panel 22 is connected to the controller unit B, and the operation of the color image forming apparatus A can be set.

  Next, the operation of the engine unit C will be described. The engine unit C in the present embodiment is an electrophotographic inline full-color image forming apparatus. The engine unit C includes four image forming units (image forming stations), that is, yellow (Y), magenta (M), and cyan (C) in order from the upstream side along the conveyance direction (arrow R27) of the recording material P. , Black (Bk) image forming units SY, SM, SC, and SBk for forming toner images of respective colors. Under these image forming portions SY, SM, SC, and SBk, a transfer belt 14 is provided around rollers 13a, 13b, 13c, and 13d. The transfer belt 14 is rotationally driven to carry a recording material P (for example, paper) on the surface and convey it in the direction of arrow R14.

  Each of the image forming units SY, SM, SC, and SBk includes an integrated process cartridge including drum units 10Y, 10M, 10C, and 10Bk and developing units 8Y, 8M, 8C, and 8Bk. Among these, the former drum units 10Y, 10M, 10C, and 10Bk are photosensitive drums 1Y, 1M, 1C, and 1Bk each having an OPC (organic optical semiconductor) photosensitive layer, cleaners 9Y, 9M, 9C, and 9Bk, and a charging roller 2Y. The latter developing units 8Y, 8M, 8C, and 8Bk include developing sleeves 5Y, 5M, 5C, and 5Bk, and nonmagnetic one-component developers 3Y, 3M, 3C, 3Bk, developer application rollers 6Y, 6M, 6C, and 6Bk, and developer application blades 7Y, 7M, 7C, and 7Bk.

  Each of the image forming units SY, SM, SC, and SBk is provided with exposure devices 11Y, 11M, 11C, and 11Bk configured by a scanner unit or an LED array that scans laser light with a polygon mirror, and these exposure devices 11Y. , 11M, 11C, and 11Bk irradiate the photosensitive drums 1Y, 1M, 1C, and 1Bk with the scanning beams 12Y, 12M, 12C, and 12Bk modulated based on the image signal to form an electrostatic latent image.

  Inside the transfer belt 14, transfer rollers 4Y, 4M, 4C, and 4Bk that press the transfer belt 14 from below to the photosensitive drums 1Y, 1M, 1C, and 1Bk are disposed. Transfer power sources 23Y, 23M, 23C, and 23Bk are connected to the transfer rollers 4Y, 4M, 4C, and 4Bk, respectively, and a transfer bias is applied to transfer the toner images on the photosensitive drums 1Y, 1M, 1C, and 1Bk. The image is transferred to the recording material P carried on the transfer belt 14.

  When the image forming operation starts, the photosensitive drums 1Y, 1M, 1C, and 1Bk, the transfer belt 14, and the like start to rotate in the directions of arrows R1 and R14 at a predetermined process speed. The photosensitive drums 1Y, 1M, 1C, and 1Bk are uniformly charged to predetermined polarities and potentials by the charging rollers 2Y, 2M, 2C, and 2Bk, and then the scanning beams 12Y from the exposure devices 11Y, 11M, 11C, and 11Bk, An electrostatic latent image based on image information is formed by 12M, 12C, and 12Bk.

  When the photosensitive drums 1Y, 1M, 1C, and 1Bk further rotate, the electrostatic latent images are visualized (developed) by the developing units 8Y, 8M, 8C, and 8Bk, and the photosensitive drums 1Y, 1M, 1C, and 1Bk are displayed on the photosensitive drums 1Y, 1M, 1C, and 1Bk. , Yellow, magenta, cyan, and black toner images are formed.

  On the other hand, the recording material P loaded in the paper feed cassette 15 is fed by a half-moon-shaped paper feed roller 16, separated into one sheet by a separation roller 17, and conveyed to a registration roller 19 by a conveyance roller 18. Is temporarily stopped. The recording material P once stopped is supplied to the conveying belt 14 by the registration rollers 19 in synchronization with the toner images on the photosensitive drums 1Y, 1M, 1C, and 1Bk. The recording material P is electrostatically attracted to the transfer belt 14 by applying a voltage between the suction roller 20 and the roller 13a, and then the yellow toner image on the photosensitive drum 1Y of the image forming unit SY is recorded by the transfer roller 4Y. Transferred onto P. Then, in synchronization with the recording material P being conveyed by the transfer belt 14, magenta, cyan, and black toner images are formed and transferred to the recording material P.

  The recording material P onto which the four color toner images have been transferred is separated from the transfer belt 14 and sent to the fixing device 21. Reference numeral 21a denotes a fixing roller, and a pressure roller 21b is brought into pressure contact with the fixing roller 21a so as to perform a driven rotation while forming a nip portion with the fixing roller 21a. The fixing roller 21a is in the form of a hollow cylinder, and a halogen heater 21c is built in the hollow space so as to supply heat necessary for fixing. On the other hand, the pressure roller 21b is heated by the fixing roller 21a through a contact nip with the fixing roller 21a. For temperature control of the roller, a temperature sensor 21d as a temperature detection element is placed in contact with the non-sheet passing area of the fixing roller 21a, and the surface temperature of the roller is detected by a change in resistance value according to the detected temperature, and temperature control (not shown) The apparatus controls the current of the halogen heater 21c so that the roller surface temperature becomes a predetermined value.

  The recording material P sent to the fixing device 21 is heated and pressed by the fixing roller 21a and the pressure roller 21b to melt and fix the toner image on the surface. The fixing speed is a speed at which the fixing device 21 conveys the recording material P, and is approximately equal to the process speed in this embodiment. Thereby, a four-color full-color image is obtained. If more heat capacity is required, a halogen heater may be incorporated in the pressure roller 21b and heated.

  On the other hand, the toner (residual toner) that is not transferred to the recording material P and remains on the photosensitive drums 1Y, 1M, 1C, and 1Bk is removed by cleaning devices 9Y, 9M, 9C, and 9Bk such as a fur brush and a blade. Unnecessary toner adhering to the transfer belt 14 is removed by a transfer belt cleaning device 24 such as a blade, a fur brush, or a web.

  The engine unit C has two types of operation modes: a normal mode (1/1 speed mode) operating at a process speed of 100 mm / s and a 1/2 speed mode operating at a process speed of 50 mm / s. Next, the toner used in the image forming apparatus of the present invention will be described. The toner used in the present invention includes a wax as a release agent in a binder having a colorant component to enable oilless fixing, and its melt viscosity has an MI value of 0.5 g according to the Melt Index measurement method. To 100 g. Hereinafter, the toner will be described in detail. As the toner, a non-magnetic one-component fine particle toner containing a binder resin, a colorant, a charge control agent and a low softening material is preferably used.

  First, as the binder resin, those usually used for color toners may be used. Examples thereof include styrene copolymers such as styrene-polyester and styrene-butyl acrylate; polyester resins; epoxy resins.

  Next, the colorant may be one commonly used for color toners. For example, for yellow toners, benzine yellow pigments, phoron yellow, acetoacetanilide anilide insoluble azo pigments, monoazo dyes, azomethine dyes Etc. For magenta toner, xanthene-based magenta dye phosphotungsten molybdate acid lake pigment, 2,9-dimethylquinacridone, naphthol-based insoluble azo pigment, anthraquinone dye, coloring material composed of xanthene dye and organic carboxylic acid, thioindigo, Examples thereof include naphthol-based insoluble azo pigments. Examples of cyan toner include copper phthalocyanine pigments.

  As the charge control agent, those usually used for color toners may be used. For example, examples of the negative charge control agent include alkyl salicylic acid metal complexes, digalbonic acid metal complexes, and polycyclic salicylic acid metal salts. Examples of the positive charge control agent include quaternary ammonium salts, benzothiazole derivatives, guanamine derivatives, dibutyltin oxide, and other nitrogen-containing compounds.

  Low softening materials include polymethylene waxes such as paraffin wax, polyolefin wax, microcrystalline wax, and Fischer tropish wax; amide waxes; higher fatty acids; long chain alcohols; ester waxes; and their graft compounds and block compounds. Derivatives may be mentioned, and the content is preferably 5 to 30% by weight based on the toner.

  The toner is a polymerized toner obtained by a polymerization method in which toner particles are produced by polymerizing a polymerizable monomer composition containing a polymerizable monomer, a colorant, a charge control agent, and a low softening point substance. It is preferable that the polymerized toner obtained by polymerizing the polymerizable monomer composition in a liquid medium can have a spherical shape. In particular, in the case of a suspension polymerization toner obtained by suspension polymerization of a polymerizable monomer composition in an aqueous medium, the material contained in the polymerizable monomer composition in the aqueous medium. By using the polarity difference, the wax as the low softening point substance can be encapsulated in the toner particles, so that it is preferably used.

  The toner has a shape factor SF1 of 100 to 140, preferably 100 to 120, a shape factor SF2 of 100 to 120, and a non-magnetic one-component fine particle having a substantially spherical shape having a weight average particle diameter of 5 to 7 μm. A particle size polymerized toner is preferably used. The shape factor SF1 here is a value indicating the ratio of the roundness of the shape of the spherical substance, as shown in FIG. 2A, and is an elliptical figure formed by projecting the spherical substance on a two-dimensional plane. Is expressed by a value obtained by dividing the square of the maximum length MXLNG by the figure area AREA and multiplying by 100π / 4. That is, the shape factor SF1 is defined by the following equation.

SF1 = {(MXLNG) ² / AREA} × (100π / 4)

  The larger the value of SF1, the more irregular the shape of the spherical substance. If SF1 is too large, the characteristics associated with the spherical shape may be weakened, and the electric field cleaning performance may be weakened. As shown in FIG. 2B, the shape factor SF2 is a numerical value indicating the ratio of the unevenness of the shape of the substance, and the square of the perimeter PERI of the figure formed by projecting the substance on the two-dimensional plane is the figure area. It is expressed as a value when divided by AREA and multiplied by 100π / 4. That is, it is defined by the following expression of the shape factor SF2. The larger the value of SF2, the more conspicuous the surface of the substance becomes.

SF2 = {(PERI) ² / AREA} × (100 / 4π)

  In this embodiment, a FE-SEM (S-800) manufactured by Hitachi, Ltd. is used, a toner image is randomly sampled 100 times, and the image information is introduced into an image analyzer (LUSEX 3) manufactured by Nireco Corporation for analysis. And calculated from the above equation.

Next, FIG. 3 shows a schematic cross-sectional view of one embodiment of polymerized toner particles. The polymerized toner 30 is spherical. It has a core 33 / shell 32 structure, the main component of the core part 33 of the core / shell structure is preferably a low softening point material, and the melting point of the low softening point material is preferably 40 to 120 ° C. For example, an ester wax that is a low softening point substance is included in the core 33, and a polymerized toner having a structure of styrene-butyl acrylate for the resin layer that is the shell portion 32 and styrene-polyester for the surface layer 31 can be used. Because it has a three-layer structure and wax is included in the core 33, an effect of preventing offset in the fixing process can be obtained, and by providing a resin layer on the surface layer 31, charging efficiency can be increased. In actual use, an oil-treated silica can be externally added to stabilize the tribo. To the toner, other additives and lubricant powders such as fluororesin powder, zinc stearate powder and polyvinylidene fluoride powder, such as cerium oxide powder, silicon carbide powder, titanium, within a range that does not substantially adversely affect the toner. Abrasives such as strontium acid powder, eg, silica powder, titanium oxide powder, aluminum oxide powder, and fluidity imparting agents such as powders obtained by treating these with silane coupling agent and / or silicone oil, anti-caking agent, eg, carbon black powder Further, a conductivity imparting agent such as zinc oxide powder or tin oxide powder, and a developability improving agent such as organic particles having opposite polarity and inorganic particles having opposite polarity can also be used.

  Examples of the method for producing the polymerized toner include the following methods.

  That is, a release agent, a colorant, a charge control agent, a polymerization initiator, and other additives are added to the polymerizable monomer, and the solution is uniformly dissolved or dispersed by a mixer such as a homogenizer or an ultrasonic disperser. The monomer composition is dispersed in a water phase containing a dispersion stabilizer by a disperser such as a homomixer. The granulation is stopped when the droplets made of the monomer composition have the desired toner particle size. Thereafter, stirring may be performed to such an extent that the particle state is maintained and the sedimentation of the particles is prevented by the action of the dispersion stabilizer. The polymerization is carried out at a polymerization temperature of 40 ° C. or higher, generally 50 to 90 ° C. For the purpose of controlling the molecular weight distribution, the temperature may be raised in the latter half of the polymerization reaction, and in order to remove the unreacted polymerizable monomer and by-products, the reaction latter half or a part of the aqueous medium after completion of the reaction May be distilled off. After completion of the reaction, the produced toner particles are recovered by washing and filtration and dried.

  In the suspension polymerization method, it is usually preferable to use 300 to 3000 parts by weight of water as a dispersion medium with respect to 100 parts by weight of the monomer composition.

  With the above-described manufacturing method, the toner has a melt viscosity of about 0.5 g to 100 g in the Melt Index measurement method described later (the larger the MI value, the smaller the viscosity), so that the offset property at the time of fixing is good. Glossiness is not too high, and images with good visibility can be obtained from documents to graphics and photographic images. The MI value was measured using a semi-automatic 2-A Melt Index manufactured by Tokyo Seiki Co., Ltd., and the measurement conditions were 2 mm orifice / load 5 kg / heat chamber 125 ° C./10 minutes.

FIG. 4 shows the relationship between the fixing temperature and the glossiness of cyan obtained when fixing at that temperature, the solid line is when fixing plain paper with a basis weight of 75 g / m ³ at 1/1 speed, and the dotted line is When a thick paper with an amount of 105 g / m ³ is fixed at 1/2 speed, a one-dot chain line is when a plain paper with a basis weight of 75 g / m ³ is fixed at 1/2 speed. Note that the relationship between the fixing temperature of other colors and the glossiness is approximately the same.

  In this embodiment, the fixing temperature at 1/1 speed is 180 ° C. and the glossiness is about 20. In general, in order to fix thick paper at 1/1 speed, it is necessary to further increase the amount of heat given per unit time, so the fixing temperature must be raised above 180 ° C. However, if the fixing temperature is increased too much, the life of the fixing roller and the pressure roller is shortened, the temperature in the image forming apparatus is increased, and power consumption is increased for heating, which is not preferable. Therefore, the amount of heat given to the paper per unit time is increased by setting the process speed to 1/2 speed.

  It can be seen from FIG. 2 that the fixing temperature may be 160 ° C. in order to obtain a gloss level comparable to that of plain paper. On the other hand, when fixing plain paper at 1/2 speed and 160 ° C. for thick paper, the glossiness becomes 30, and the fixed image has an impression clearly different from glossiness 20 when plain paper is fixed at 1/1 speed. Become.

  It can be seen from FIG. 2 that the fixing temperature may be 150 ° C. so that the glossiness when the plain paper is fixed at 1/2 speed is comparable to the glossiness at 1/1 speed. Therefore, if a 1/2 speed fixing mode for plain paper different from that for thick paper is provided, a fixed image equivalent to that at 1/1 speed can be obtained even at 1/2 speed. In addition, since the fixing temperature can be lowered from 180 ° C. to 150 ° C. at this time, the power used for heating can be reduced, and this can be used as a power saving mode.

  In this embodiment, therefore, a 1/1 speed mode (plain paper mode) for forming an image on plain paper, a 1/2 speed mode (thick paper mode) for forming an image on thick paper, and further reducing power consumption and 1/1. And a 1 / 2-speed power saving mode in which a plain paper-fixed image equivalent to that in the high-speed mode is obtained. The setting values in each mode are as follows.

  In this configuration, when a small amount of printing is often performed, if the user sets the power saving mode printing option with the printer driver 27 of the host computer D or sets the power saving mode with the control panel 22 of the main body during printing, plain paper Print in the power saving mode with a process speed of 1/2 speed and a fixing temperature of 150 ° C. In this way, it is possible to improve the power consumption efficiency by enabling the selection of the 1/1 speed mode when printing a large amount or frequently, and the power saving mode when performing a small amount of printing at intervals. .

  The smaller the difference in glossiness between 1/1 speed and 1/2 speed, the better. However, considering the balance with the fixability, the fixing temperature is set and the difference in glossiness is the primary color. If it is within 5 and within 10 with the secondary color, an equivalent image can be obtained with almost no difference perceived by human eyes.

  Conventionally, as a color toner, a sharp melt color toner using a polyester resin as a binder resin has often been used. Since the sharp melt color toner has a high affinity and is easily offset during fixing, it is necessary to cover the surface of the fixing roller with a thin film of an anti-offset liquid such as silicone oil or fluorine oil.

  However, this method cannot obtain an image equivalent to the image obtained at 1/1 speed even if the process speed is reduced to 1/2 speed and the fixing temperature is lowered as described above. That is, when the process speed is lowered, a large amount of offset preventing liquid is supplied to the recording material, and thus the tactile sensation of the recording material after fixing is clearly different. In order to improve this, a mechanism capable of changing the application amount of the application device for the liquid for preventing offset according to the process speed is required, so that the fixing device is complicated and expensive. On the other hand, if the toner contained in the wax is used, the amount of wax supplied is determined only by the amount of toner loaded regardless of the process speed, so that the tactile feeling of the recording material is not changed and the fixing obtained at 1/1 speed is achieved. The fixed image obtained when the fixing temperature is lowered at 1/2 speed is equivalent to the image.

  Next, a second embodiment will be described. Components having the same configuration and function as those in FIG.

  FIG. 5 is a longitudinal sectional view of the engine unit C of the image forming apparatus according to the second embodiment. The present embodiment is different from the first embodiment in that a conveyance belt 25 is separately provided between the transfer belt 14 and the fixing device 21.

  Since the conveying belt 25 is stretched around rollers 26 a and 26 b and driven separately from the transfer belt 14, it can be driven at a speed different from that of the transfer belt 14. In this configuration, when the user sets the power saving mode, the fixing device 21 is driven at 1/2 speed and heated to a fixing temperature of 150 ° C. for the power saving mode, and the others operate at 1/1 speed. Perform image formation.

  When the recording material P is completely moved from the transfer belt 14 onto the conveying belt 25, the conveying belt 25 driven at the 1/1 speed is decelerated to 1/2 speed, and the recording material P is transferred to the fixing device 21. Transported at 1/2 speed.

  If the process speed is reduced to 1/2, the first printout time (FPOT), which is the time from the start of image formation until the recording material P is discharged, increases. If the speed is reduced to 1/2 speed, the increase in FPOT can be minimized.

  Next, Embodiment 3 will be described.

  While the power saving mode is effective for suppressing power consumption when printing in a small amount, if a large amount of printing is performed in the power saving mode, the amount of power consumption may increase. FIG. 6 is a diagram showing the relationship between the number of continuous prints and the amount of power consumed in the 1/1 speed and 1/2 speed power saving modes. You can see that the amount is reversed. This is because at 1/2 speed, the heating time of the fixing device is twice as long as at 1/1 speed, so that even if the power consumption is small, the power consumption increases.

  Therefore, in this embodiment, even if the user sets the power saving mode, when the controller B processes the print signal, it is 1 when it is determined that the number of continuous prints exceeds a predetermined number (here, 63). / The image is formed in the normal mode of 1-speed. This determination may be made by the host computer or the print server. In this case, the print signal includes a mode designation signal and is sent to the image forming apparatus.

  As a result, when a small amount of printing is performed, the printer operates in a power saving mode. When a large amount of printing is performed, printing is performed at a normal speed, so that it is possible to always efficiently form an image with minimum power consumption.

  Next, a fourth embodiment will be described.

  In general, in the heat roller system, since the heat capacity of the fixing roller is large, it takes a very long time to raise the surface of the fixing roller to a temperature necessary for fixing, and it takes time to warm up the image forming apparatus. For this reason, when the fixing roller is cooled to room temperature, the first printout time (FPOT), which is the time from the start of printing until the recording material is discharged, becomes long, and the user is kept waiting.

  Therefore, in order to shorten the FPOT, there is a method in which a standby mode in which the surface of the fixing roller is always heated at a temperature lower than the fixing temperature in advance even when the main body is not used is provided so that the temperature can be quickly heated to the fixing temperature at the time of printing. Taken.

  The present invention can also be applied when such a standby mode is provided. In this case, the temperature of the fixing roller in the standby mode is preferably set to be equal to or lower than the fixing temperature in the power saving mode, and is set to 140 ° C. in this embodiment.

  In this configuration, the image forming operation will be described with reference to the flowchart of FIG.

  First, when printing information is sent from the host computer D and image formation is started (S71), the controller unit B determines whether the printing is for plain paper or thick paper (S72). If it is for thick paper, image formation is performed in the thick paper mode (S73). On the other hand, if it is for plain paper, it is checked whether the power saving mode is set (S74). If the power saving mode is not set, image formation is performed in the plain paper mode (S75). If the power saving mode is set, it is next checked whether the temperature TR of the fixing roller is higher than the fixing temperature TE (150 ° C. in this case) in the power saving mode (S76). When TR> TE, it is determined that the time has not passed since the previous printing, and the fixing roller can be quickly heated to the fixing temperature in the plain paper mode, so image formation in the plain paper mode is performed (S75). . When TR ≦ TE, the image can be formed in the power saving mode because the fixing temperature in the power saving mode can be quickly heated (S77).

  As described above, even when the standby mode is set, the image can be efficiently formed with the minimum power consumption.

  Next, a fifth embodiment will be described. The image forming apparatus using the heat roller type fixing device has been described so far, but in recent years, a fixing device using a film heating method instead of the heat roller has been used. The present invention can also be applied to an image forming apparatus having such a film heating type fixing device.

  The film heating type fixing device 28 according to the present embodiment will be described in detail with reference to FIG. The fixing device 28 can be directly replaced with the fixing device 22 of FIG. FIG. 8 is a longitudinal sectional view showing a schematic configuration of the electromagnetic induction heating type fixing device 28 according to the present embodiment.

  Reference numeral 280 denotes a cylindrical fixing film as a rotating body having a heat generating layer (conductive magnetic member). Reference numerals 284a and 284b denote film support members (film guides) having a substantially semicircular arc shape in cross section on the lower side and the upper side, and form a substantially cylindrical film guide 284 with the opening sides facing each other. The cylindrical fixing film 280 is loosely fitted outside the film guide 284.

  Inside the film guide 284, magnetic field generating means comprising an exciting coil 286 and magnetic cores 287a, 287b, 287c combined in a T shape are disposed. An excitation circuit (not shown) is connected to the excitation coil 286. Reference numeral 282 denotes a laterally long pressurizing rigid stay disposed in contact with the inner surface flat portion of the upper film support member 284b. Reference numeral 285 denotes an insulating member for insulating the magnetic cores 287a, 287b, 287c and the exciting coil 286 from the pressurizing rigid stay 282.

  Reference numeral 283 denotes a pressure roller. The fixing film 280 is sandwiched between the pressure roller 283 and the film guide 284, and a predetermined pressure is applied from the pressure roller 283 to the film guide 284, whereby the film guide 284 and the pressure roller 283 are fixed with a predetermined width. A nip portion N is formed and mutually pressed. The magnetic core 287a is disposed corresponding to the position where the fixing nip portion N is formed.

  The pressure roller 283 is rotated by the driving means M in the counterclockwise direction indicated by the arrow a. By the rotational driving of the pressure roller 283, a frictional force is generated between the pressure roller 283 and the outer surface of the fixing film 280, and the rotational force acts on the fixing film 280. The fixing film 280 has a peripheral speed substantially corresponding to the peripheral speed of the pressure roller 283 while sliding the inner surface of the fixing film 280 in close contact with the lower surface of the film guide 284 in the fixing nip portion N, and the clockwise direction indicated by the arrow b. The outer periphery of the film guide 284 is rotated (pressure roller drive system).

  The exciting coil 286 generates an alternating magnetic flux by an alternating current supplied from an exciting circuit (not shown). Since the magnetic core 287a of the T-shaped magnetic core 287 is provided corresponding to the position of the fixing nip portion N, the alternating magnetic flux is concentrated in the fixing nip portion N, and the alternating magnetic flux is the fixing nip portion N. , An eddy current is generated in the heat generating layer of the fixing film 280. This eddy current generates Joule heat in the heat generating layer due to the specific resistance of the heat generating layer.

  As for the temperature of the fixing nip portion N, a temperature sensor 281 as a temperature detecting element is disposed immediately before the nip, and the current supply to the exciting coil 286 is controlled by a temperature control device (not shown) from a resistance value change accompanying the detected temperature. Thus, the predetermined temperature is adjusted to be maintained.

  In such a film heating type fixing device, the heat capacity of the film, which is a heating member, is much smaller than that of a conventional heat roller type fixing device, so that the heat energy from the heating means is efficiently used in the fixing process. Most of the power required for heating can be used for fixing. Therefore, when the present invention is applied to an image forming apparatus having such a fixing device, the fixing temperature is lowered in the power saving mode, so that the power consumption required for heating is reduced and further power saving can be achieved. In addition to the electromagnetic induction heating, the heating method may use a linear heater.

  The image forming apparatus according to the present invention is not limited to the above-described embodiment, and can be variously modified within the scope of the gist. That is, in each of the above-described embodiments, the process speed or the fixing speed is two types of 1/1 speed and 1/2 speed, but other than the 1/1 speed such as 1/3 speed and 1/4 speed. A plurality of low-speed modes may be provided, and in that case, at least one of the low-speed modes may be output so as to output an image equivalent to the plain paper mode.

  Although the wax-encapsulated toner is described as being produced by a polymerization method, a wax-encapsulated toner produced by melting and kneading a binder resin and wax and then pulverizing them may be used. The fixing temperature may be other than the above, and the color order may be other than Y, M, C, and Bk. Further, the image forming apparatus may be a system other than in-line, and can be applied to a monochrome image forming apparatus.

1 is a longitudinal sectional view showing a schematic configuration of an image forming apparatus according to a first embodiment. Explanatory diagram of toner shape factors SF1 and SF2 Cross-sectional model of polymerized toner Diagram showing the relationship between fixing temperature and glossiness A longitudinal sectional view showing a schematic configuration of an image forming apparatus according to a second embodiment. Diagram showing the relationship between the number of printed pages and power consumption A flowchart showing a method of switching an image forming mode when a standby mode is provided FIG. 6 is a longitudinal sectional view showing a schematic configuration of an electromagnetic induction heating type fixing device according to a fifth embodiment.

Explanation of symbols

1Y, 1M, 1C, 1Bk Photosensitive drum 2Y, 2M, 2C, 2Bk Charging roller 3Y, 3M, 3C, 3Bk Developer 4Y, 4M, 4C, 4Bk Transfer roller 5Y, 5M, 5C, 5Bk Developing sleeve 6Y, 6M, 6C , 6Bk Developer coating roller 7Y, 7M, 7C, 7Bk Developer coating blade 9Y, 9M, 9C, 9Bk Cleaner, cleaning device 11Y, 11M, 11C, 11Bk Exposure device 12Y, 12M, 12C, 12Bk Scanning beam 14 Transfer belt 20 Adsorption roller 21 Fixing device 23Y, 23M, 23C, 23Bk Transfer bias power supply

Claims (8)

A color image forming apparatus comprising fixing means for obtaining a fixed image by heat-fixing a color toner image formed on a recording material, and capable of fixing at a plurality of fixing speeds,
The color toner is a toner containing wax, and when the same image is fixed on the same type of recording material at the entire fixing speed of the color image forming apparatus, at least two of the obtained fixed images are obtained. The color image forming apparatus is characterized in that the difference in glossiness between the primary colors is within 5 and the difference in glossiness between the secondary colors is within 10.   Of at least two fixing speeds for obtaining a fixed image in which the difference in glossiness between primary colors is within 5 and the difference in glossiness between secondary colors is within 10, one is the fastest fixing speed. The color image forming apparatus according to claim 1.   The fixing temperature at at least two fixing speeds for obtaining a fixed image in which a difference in glossiness between primary colors is within 5 and a difference in glossiness between secondary colors is within 10 is different. The color image forming apparatus according to 1.   According to the color image forming apparatus, a fixed image in which the difference in glossiness of the primary color is within 5 and the difference in glossiness of the secondary color is within 10 depending on the number of printed sheets from the start of the printing operation to the stop of the printing operation. 2. The color image forming apparatus according to claim 1, wherein a fixing speed is selected from among at least two fixing speeds to be obtained.   5. The color image forming apparatus according to claim 4, wherein the number of printed sheets from the start of the printing operation to the stop of the printing operation is measured by a host computer, a print server, or a controller in the image forming apparatus.   2. A color image forming apparatus according to claim 1, wherein said fixing means is composed of two elastic rollers, and is a heat roller type fixing means having a heating element in at least one of these elastic rollers.   2. A color image according to claim 1, wherein said fixing means is a fixing means having heat resistance and releasability and comprising an endless film sheet having a heat generating means inside or outside and a pressure means. Forming equipment.   2. The color image forming apparatus according to claim 1, wherein the image forming apparatus has a standby mode in which the fixing unit is maintained at a predetermined temperature lower than the fixing temperature during non-image formation.