Image forming device

Abstract

To prevent a trouble that occurs when the temperature of fixing means does not suit a recording sheet.SOLUTION: An image forming apparatus has fixing means that heats a recording sheet on which an image is formed to fix the image to the recording sheet, and fixing temperature control means 110, 120 that control the temperature of the fixing means, and the image forming apparatus has cooling means that cools the recording sheet after the fixing performed by the fixing means, fixing temperature detection means 25h, 25i, 25j that detect the temperature of the fixing means when the recording sheet passes through the fixing means, and cooling temperature detection mans 26h that detects the temperature of the cooling means when the recording sheet passes through the cooling means. The fixing temperature control means control the temperature of the fixing means based on results of detection performed by the fixing temperature detection means and the cooling temperature detection means.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus. Place It is related to. [Background technology]

[0002] 2. Description of the Related Art Conventionally, there has been known an image forming apparatus having a fixing unit that heats and fixes an image formed on a recording sheet, and a fixing temperature control unit that controls the temperature of the fixing unit.

[0003] Patent Document 1 discloses an electrophotographic image forming apparatus equipped with a paper thickness sensor that measures the thickness of paper, a basis weight sensor that measures the basis weight of paper, and a surface property sensor that measures the surface property of paper (the amount of light reflected by the paper). This image forming apparatus is equipped with a paper type discrimination engine that discriminates paper type information based on the detection output of these sensors. This paper type discrimination engine is a trained model generated by supervised learning using training data in which paper type information set by a user is used as a correct answer label. When printing using paper whose paper type information has been discriminated by the paper type discrimination engine, this image forming apparatus executes printing under printing conditions corresponding to the paper type information. Summary of the Invention [Problem to be solved by the invention]

[0004] However, in conventional image forming apparatuses, even if printing is performed under printing conditions corresponding to the paper type information determined by the paper type determination engine based on the detection outputs of the various sensors described above, cooling hands There was a problem that the temperature of the tray was not suitable for the paper, and problems such as blocking of the discharged paper were likely to occur. [Means for solving the problem]

[0005] In order to solve the above-mentioned problems, the present invention provides an image forming apparatus having a fixing unit that heat-fixes an image on a recording sheet on which an image has been formed, a cooling unit that cools the recording sheet after fixing by the fixing unit, and a cooling temperature control unit that adjusts the temperature of the cooling unit, wherein the image forming apparatus further comprises a fixing temperature detection unit that detects the temperature of the fixing unit when the recording sheet passes through the fixing unit, and a cooling temperature detection unit that detects the temperature of the cooling unit when the recording sheet passes through the cooling unit. an estimation means for estimating physical property information of the recording sheet based on the detection results of the fixing temperature detection means and the cooling temperature detection means; and the cooling means includes a heat absorbing member that absorbs heat from the recording sheet passing through it, and a cooling member that cools the heat absorbing member with air or liquid, The cooling temperature control means The physical property information estimated by the estimation means based on, Controlling the cooling capacity of the cooling member The temperature of the cooling means is controlled. [Effects of the Invention]

[0006] According to the present invention, cooling hands This can prevent problems caused by the temperature of the stage not being suitable for the recording sheet. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic configuration diagram showing a printer according to an embodiment. [Figure 2] FIG. 2 is a schematic diagram showing a fixing device in the printer. [Figure 3] FIG. 2 is a schematic diagram showing a cooling device in the printer. [Figure 4] FIG. 10 is a schematic diagram showing another example of a cooling device. [Figure 5] FIG. 10 is a schematic diagram showing yet another example of a cooling device. [Figure 6] FIG. 2 is a control block diagram relating to temperature control of a fixing device and a cooling device in the embodiment. [Figure 7] 5 is a flowchart showing a flow of temperature control of a fixing device and a cooling device in the embodiment. [Figure 8] 10 is a graph showing the relationship between the brand of recording sheet and the target value of fixing temperature. [Figure 9] FIG. 1 is an explanatory diagram showing an example of an artificial neural network used in an experimental example. [Figure 10](a) is a graph plotting the estimation results of the basis weight of a recording sheet when validation data is input into a trained model created in the examples. (b) is a graph plotting the estimation results of the thickness of a recording sheet when validation data is input into a trained model created in the examples. (c) is a graph plotting the estimation results of the smoothness of a recording sheet when validation data is input into a trained model created in the examples. [Figure 11] (a) is a graph plotting the estimation results when inputting physical property information of a recording sheet estimated by the trained model using an existing estimation program that estimates the temperature of the paper discharge section from input values ​​including physical property information of the recording sheet. (b) is a graph plotting the estimation results when inputting physical property information of a recording sheet using the same existing estimation program. (c) is a graph plotting the estimation results when inputting actually measured physical property information of a recording sheet using the same existing estimation program. [Figure 12] (a) is the temperature profile of various temperature sensors when the fixing temperature is set to 120°C and 500 sheets of 45K paper are fed continuously. (b) is the temperature profile of various temperature sensors when the fixing temperature is set to 120°C and 500 sheets of 70K paper are fed continuously. (c) is the temperature profile of various temperature sensors when the fixing temperature is set to 160°C and 500 sheets of 45K paper are fed continuously. (d) is the temperature profile of various temperature sensors when the fixing temperature is set to 160°C and 500 sheets of 70K paper are fed continuously. [Figure 13] (a) is the temperature profile of various temperature sensors when the fixing temperature is set to 120°C and 500 sheets of POD gloss coated 100 paper are fed continuously. (b) is the temperature profile of various temperature sensors when the fixing temperature is set to 120°C and 500 sheets of 90K paper are fed continuously. (c) is the temperature profile of various temperature sensors when the fixing temperature is set to 160°C and 500 sheets of POD gloss coated 100 paper are fed continuously. (d) is the temperature profile of various temperature sensors when the fixing temperature is set to 160°C and 500 sheets of 90K paper are fed continuously. [Figure 14] A reference diagram showing the difference in surface properties between plain paper and coated paper. DETAILED DESCRIPTION OF THE INVENTION

[0008] An embodiment of an electrophotographic printer will be described below as an image forming apparatus to which the present invention is applied. First, the basic configuration of the printer according to the embodiment will be described. 1 is a schematic diagram showing the configuration of a printer according to an embodiment. In the figure, printer 100 has a paper feed unit (paper feed table) that supplies recording sheets stored inside to a paper feed path, and a printer unit mounted on top of the paper feed unit. The suffixes Y, M, C, and K added to the reference numerals in the figure indicate components for yellow, magenta, cyan, and black.

[0009] Near the center of the printer section, an endless intermediate transfer belt 10 is provided, which is wound around a plurality of support rollers 14, 15, 15', 16, and 63 and is capable of endlessly moving clockwise in the drawing. Of the entire circumferential area of ​​the intermediate transfer belt 10, a belt cleaning device 17 abuts on the front side of the belt at the location where the belt is wound around the cleaning backup roller. This belt cleaning device 17 removes residual toner remaining on the front surface of the intermediate transfer belt 10 after it has passed through a secondary transfer nip, which will be described later.

[0010] Of the entire circumferential area of ​​the intermediate transfer belt 10, the area between the drive roller 14 and the support roller 15 extends in a substantially horizontal direction. A tandem image forming unit 20 is disposed above this area. The tandem image forming unit 20 has four imaging units 18Y, 18M, 18C, and 18K for yellow, magenta, cyan, and black disposed along the front surface of the belt, facing the front surface of the belt.

[0011] An optical writing device 21 serving as latent image writing means is provided above the tandem image forming unit 20. The imaging units 18Y, 18M, 18C, and 18K of the tandem image forming unit 20 each have drum-shaped photoreceptors 40Y, 40M, 40C, and 40K as latent image carriers on which latent images of yellow, magenta, cyan, and black are formed. The surfaces of the photoreceptors 40Y, 40M, 40C, and 40K are uniformly charged (e.g., to −650 V) by charging devices 60Y, 60M, 60C, and 60K, and then optically scanned by the optical writing device 21, which drives a light source based on image data. The light-irradiated portions of the surfaces of the photoreceptors 40Y, 40M, 40C, and 40K, which are illuminated by this optical scanning, have their potential attenuated (e.g., to −50 V), becoming electrostatic latent images.

[0012] The electrostatic latent images formed on the surfaces of the photoreceptors 40Y, 40M, 40C, and 40K are developed into Y, M, C, and K toner images by the developing devices 59Y, 59M, 59C, and 59K. The developing devices 59Y, 59M, 59C, and 59K are supplied with Y, M, C, and K toner from toner bottles 50Y, 50M, 50C, and 50K as needed. Inside the developing devices 59Y, 59M, 59C, and 59K, Y, M, C, and K developers, which are mixtures of Y, M, C, and K toner and magnetic carrier, are stirred. The Y, M, C, and K toner in the Y, M, C, and K developers are negatively triboelectrically charged (e.g., -30 μC / g). Inside the developing devices 59, 59M, 59C, and 59K, developing rollers for Y, M, C, and K are provided, respectively. The Y, M, C, and K developing rollers have portions of their peripheral surfaces exposed to the outside through openings in the casing, and are positioned opposite the photoconductors 40Y, 40M, 40C, and 40K. The Y, M, C, and K developers drawn up by the Y, M, C, and K developing rollers are transported to the developing zones facing the photoconductors 40Y, 40M, 40C, and 40K as the rollers rotate. In the developing zone, a developing bias (e.g., −500 V) is applied between the electrostatic latent images on the photoconductors 40Y, 40M, 40C, and 40K and the developing rollers, which are applied with a developing bias. This developing potential causes the Y, M, C, and K toner on the Y, M, C, and K developing rollers to separate from the magnetic carrier and transfer to the electrostatic latent images on the photoconductors 40Y, 40M, 40C, and 40K. As a result, the electrostatic latent images on the photoconductors 40Y, 40M, 40C, and 40K are developed with Y, M, C, and K toners to become Y, M, C, and K toner images.

[0013] Primary transfer rollers 62Y, 62M, 62C, and 62K are disposed below the photoconductors 40Y, 40M, 40C, and 40K, and press the intermediate transfer belt 10 against the photoconductors 40Y, 40M, 40C, and 40K. This forms primary transfer nips for Y, M, C, and K where the photoconductors 40Y, 40M, 40C, and 40K come into contact with the intermediate transfer belt 10. Around the primary transfer nips for Y, M, C, and K, a primary transfer electric field is formed between the primary transfer rollers 62Y, 62M, 62C, and 62K, to which a primary transfer bias is applied, and the electrostatic latent images on the photoconductors 40Y, 40M, 40C, and 40K.

[0014] When the printer 100 receives image data, it rotates the drive roller 14 using a drive unit, thereby moving the intermediate transfer belt 10 endlessly in the clockwise direction in the figure. At the same time, the printer 100 drives the imaging units 18Y, 18M, 18C, and 18K to form Y, M, C, and K toner images on the photoconductors 40Y, 40M, 40C, and 40K. These toner images are primarily transferred and superimposed onto the front surface of the intermediate transfer belt 10 at the primary transfer nips for Y, M, C, and K. As a result, a four-color superimposed toner image is formed on the front surface of the intermediate transfer belt 10.

[0015] In addition, when forming a black monochrome image on the intermediate transfer belt 10, it is also possible to move the support rollers 15, 15' other than the drive roller 14 to separate the yellow, magenta, and cyan photosensitive elements 40Y, 40M, and 40C from the intermediate transfer belt 10.

[0016] After passing through the primary transfer nips for Y, M, C, and K, residual toner that was not transferred to the intermediate transfer belt 10 adheres to the surfaces of the photoconductors 40Y, 40M, 40C, and 40K. This residual toner is removed from the surfaces of the photoconductors 40Y, 40M, 40C, and 40K by drum cleaning devices 61Y, 61M, 61C, and 61K, and then transported to a waste toner bottle.

[0017] After cleaning, the surfaces of the photoreceptors 40Y, 40M, 40C, and 40K are uniformly charged again by the charging devices 60Y, 60M, 60C, and 60K.

[0018] The printer 100 selectively rotates one of the paper feed rollers 42 on the paper feed table 200 of the paper feed unit. This causes a recording sheet to be fed out from one of a plurality of paper feed cassettes 44 arranged in multiple stages in a paper bank 43. The recording sheets are then separated one by one by a separation roller 45 and sent to a paper feed path 48, after which they are transported by a transport roller 47 and enter the paper feed path 48 of the printer unit. The recording sheet that has entered the paper feed path 48 of the printer unit hits the registration nip of a pair of registration rollers 49 and stops.

[0019] A secondary transfer device 22 is disposed below the intermediate transfer belt 10. The secondary transfer device 22 forms a secondary transfer nip by bringing a secondary transfer roller 16′ into contact with a portion of the entire circumferential area of ​​the intermediate transfer belt 10 where the intermediate transfer belt 10 is wound around a secondary transfer opposing roller 16, which serves as a support roller.

[0020] The pair of registration rollers 49 start rotating at the timing when the recording sheet can be superimposed on the four-color superimposed toner image on the belt at the secondary transfer nip, and feed the recording sheet toward the secondary transfer nip. In the secondary transfer nip, the four-color superimposed toner image on the intermediate transfer belt 10 is secondarily transferred onto the recording sheet by the action of the secondary transfer electric field and nip pressure, becoming a full-color image.

[0021] The recording sheet that has passed through the secondary transfer nip is sent to a fixing device 25, where a full-color image is fixed onto the surface of the recording sheet. The recording sheet, whose temperature has risen after passing through the fixing device 25, is sent to a cooling device 26 where it is cooled, and then is discharged outside the machine via a pair of discharge rollers 56 and stacked on a paper discharge tray 57.

[0022] In a double-sided print mode in which images are formed on both sides of a recording sheet, a recording sheet with a toner image fixed only on the first side thereof passes through the cooling device 26 and is then sent to the re-feeding device 28, rather than the pair of discharge rollers 56. The recording sheet is then re-fed to the paper feed path 48 while being turned over by the re-feeding device 28. The recording sheet is then sent from the paper feed path 48 to the secondary transfer nip, where the four-color superimposed toner image is secondarily transferred onto the second side thereof, and then passed through the fixing device 25 and the pair of discharge rollers 56 and discharged to the outside of the apparatus.

[0023] After passing through the secondary transfer nip, the intermediate transfer belt 10 has residual toner adhering to its surface removed by a belt cleaning device 17, and then re-enters the primary transfer nips for Y, M, C, and K. The toner contained in the belt cleaning device 17 is collected in a waste toner bottle by a transport means.

[0024] Furthermore, this embodiment is provided with a paper type sensor 102, which is an optical sensor for detecting the type of recording sheet transported to the fixing device 25. The paper type sensor 102 can be a paper thickness sensor or a paper size sensor installed in the transport path of the recording sheet from the paper feed unit to the fixing device 25.

[0025] FIG. 2 is a schematic diagram showing the fixing device 25 in this embodiment. 2, fixing device 25 includes fixing belt 25a as a heating member, heating roller 25b, fixing roller 25c, and fixing heater 25d as a heating means provided on heating roller 25b. Fixing device 25 also includes pressure roller 25e as a pressure member, pressure heater 25f as a heating means provided on pressure roller 25e, and pressure roller fan 25g for cooling pressure roller 25e. Fixing device 25 also includes heating roller temperature sensor 25h, fixing roller temperature sensor 25i, and pressure roller temperature sensor 25j as fixing temperature detection means. Of temperature sensors 25h, 25i, and 25j, at least fixing roller temperature sensor 25i has a function of measuring the temperature of the sensor itself (compensated temperature).

[0026] A fixing belt 25a is stretched over the fixing roller 25c and the heating roller 25b with a constant tension. The fixing belt 25a is an endless belt and has a two-layer structure in which an elastic layer such as a silicone rubber layer (300 to 500 μm) is formed on a base material such as nickel, stainless steel, or polyimide. The fixing roller 25c has a metal core on which silicone rubber is formed. The heating roller 25b is a hollow roller made of aluminum or iron and has a fixing heater 25d installed inside.

[0027] The temperature of the fixing belt 25a is controlled by turning on and off the power to the fixing heater 25d of the heating roller 25b. The heating means in the fixing device 25 is not limited to the heaters 25d and 25f, but may be other temperature-controllable heating means such as a lamp or an electromagnetic induction heating device (IH heater).

[0028] The pressure roller 25e is located below the fixing belt 25a and rotatably presses against the portion of the fixing belt 25a that is wound around the fixing roller 25c. The pressure roller 25e is a hollow roller made of aluminum or iron, and has a pressure heater 25f inside. The temperature of the pressure roller 25e is controlled by turning on and off the power to the pressure heater 25f of the pressure roller 25e.

[0029] The pressure of pressure roller 25e is applied by a pressure spring, which serves as a biasing means for biasing the shaft of pressure roller 25e toward fixing roller 25c. Changing the rotation angle of the pressure cam displaces the support member that supports the pressure spring, thereby changing the compression amount of the pressure spring. Therefore, by controlling the rotation angle of the pressure cam, the biasing force of the pressure spring can be changed, and the pressure of pressure roller 25e (nip pressure of the fixing nip) can be changed.

[0030] A fixing nip is formed by the pressure contact between the pressure roller 25e and the fixing belt 25a, and when the recording sheet S passes through this fixing nip, the toner image on the recording sheet S is fixed to the recording sheet S by heat and pressure.

[0031] FIG. 3 is a schematic diagram showing the cooling device 26 in this embodiment. 3, cooling device 26 is arranged so that heat absorption portion 26b (cooling portion that cools recording sheet S) of heat pipe 26a contacts recording sheet S after fixing, and heat radiation portion 26c of heat pipe 26a extends from heat absorption portion 26b to the side of recording sheet S. When cooling device 26 is arranged inside fixing device 25, it is preferable to arrange heat radiation portion 26c of heat pipe 26a so that it is exposed to the outside of fixing device 25. This cooling device 26 is equipped with cooling device temperature sensor 26h as cooling temperature detection means.

[0032] 3, heat dissipation fins 26d are installed on heat dissipation section 26c of heat pipe 26a. By blowing air onto heat dissipation fins 26d using fan 26e, which serves as air blowing means, the temperature of heat absorption section 26b of heat pipe 26a is adjusted to decrease, thereby improving cooling efficiency.

[0033] Furthermore, in order to avoid being affected by the surroundings or to increase cooling efficiency, the heat dissipation portion 26c and heat dissipation fins 26d of the heat pipe 26a may be housed in a duct together with the fan 26e as needed. The duct has an intake port that draws air from outside the machine into the duct and an exhaust port that exhausts the air in the duct to the outside of the machine.

[0034] The cooling device 26 may be configured in any other manner as long as it can cool the recording sheet S with a cooling member and can control the temperature of the cooling member.

[0035] Another configuration of the cooling device may be, for example, as shown in Fig. 4. This cooling device 27 includes a cooling roller 27a which is a cooling member (heat absorbing member), and a conveyor belt 27b which contacts the cooling roller 27a to form a cooling nip. The cooling device 27 also includes two support rollers 27c and 27d which stretch the conveyor belt 27b, guide rollers 27e and 27f which are arranged upstream and downstream of the cooling roller 27a in the sheet conveying direction, and a cooling device temperature sensor 27h which serves as a cooling temperature detection means.

[0036] 4 uses a liquid-cooled (water-cooled) type cooling device as a heat-absorbing member cooling means, which circulates a refrigerant made of a liquid such as water or gas (cooling water is used in this embodiment) to cool the cooling roller 27a. The temperature of the cooling roller 27a is controlled by a chiller (cooling water circulator) 27g, which adjusts the temperature of the circulating cooling water with a refrigerator.

[0037] Further, as shown in FIG. 5, another configuration of the cooling device may be one in which two metal plates 29a and 29b are used as heat-absorbing members disposed adjacent to the recording sheet S after fixing, as cooling members. In the cooling device 29 shown in FIG. 5, the two metal plates 29a and 29b are provided with a heat sink 29c for cooling the metal plates. By blowing air onto the heat sink 29c using a fan 29d, which serves as an air blowing means, the temperatures of the two metal plates 29a and 29b can be adjusted to lower, thereby improving cooling efficiency. This configuration also includes a cooling device temperature sensor 29h as a cooling temperature detection means.

[0038] 5, the temperature of the recording sheet S that has passed through the fixing device 25 is reduced by being transported while being in close proximity to and in contact with metal plates 29a and 29b that form the sheet transport path. The metal plates 29a and 29b, which have been heated by the passage of the recording sheet S, are designed to radiate heat from a heat sink 29c and maintain the cooling effect of the recording sheet S.

[0039] Next, the temperature control of the fixing device 25 and the cooling device 26 in this embodiment will be described. FIG. 6 is a control block diagram relating to temperature control of the fixing device 25 and the cooling device 26 in this embodiment. The temperature control in this embodiment is performed by a paper physical property estimating unit 110 and a temperature control unit 120, which serve as fixing temperature control means and cooling temperature control means.

[0040] The paper physical property estimation unit 110 receives print job information (print mode, image information, number of prints, etc.) from the printer control unit 130. The paper physical property estimation unit 110 also receives a detection result from at least one of the temperature sensors 25h, 25i, 25j installed in the fixing device 25 of the printer 100 (temperature information of the fixing device 25 when paper is passing through). The paper physical property estimation unit 110 also receives a detection result from the temperature sensor 26h installed in the cooling device 26 of the printer 100 (temperature information of the cooling device 26 when paper is passing through). The paper physical property estimation unit 110 may also receive a detection result from the paper type sensor 102. The paper physical property estimation unit 110 estimates the physical property values ​​(physical property information) of the recording sheet S based on this input information.

[0041] The physical property values ​​of the recording sheet S estimated by the paper physical property estimation unit 110 are information on physical properties related to the temperature of the recording sheet S after fixing or the temperature of the recording sheet S after cooling, and specifically include the basis weight, paper thickness, brand (paper type), smoothness, etc. of the recording sheet S.

[0042] In this embodiment, the paper physical property estimation unit 110 estimates the physical property values ​​of the recording sheet S by executing a predetermined estimation program on a computer, and this estimation program uses a trained model created by so-called machine learning. Details of this estimation program (trained model) will be described later.

[0043] The temperature control unit 120 calculates a fixing correction temperature from the physical property values ​​of the recording sheet S estimated by the paper physical property estimation unit 110, and controls the temperature of the fixing unit 25 so that the temperature of the fixing unit 25 is equal to or lower than the fixing correction temperature, and also controls the temperature of the cooling unit 26 accordingly. Specifically, the temperature control of the fixing unit 25 is performed by changing the fixing setting temperature (target fixing temperature) to control the temperature of the fixing heater 25d. The temperature control of the cooling unit 26 is performed by controlling the air volume (rotation speed) of the fan 26e that blows air through the heat dissipation fins 26d provided on the heat dissipation unit 26c of the heat pipe 26a.

[0044] The temperature of the fixing device 25 may be controlled by controlling the temperature of the pressure roller 25e. If the temperature of the recording sheet S after fixing is too high, problems such as hot offset, in which toner adheres to conveying members downstream of the fixing device 25 in the sheet conveying direction, and blocking, in which a recording sheet sticks to a subsequent recording sheet after being stacked on the paper discharge tray 57, occur. Therefore, if the temperature of the recording sheet S immediately after fixing is high, it is preferable to control the temperature of the pressure roller 25e, which comes into direct contact with the recording sheet S (without an unfixed toner image in between).

[0045] However, it is not desirable to always cool the temperature of the cooling device 26 at the maximum cooling capacity from the viewpoint of energy saving and also from the viewpoint of noise of the fan 26e. Therefore, it is required to control the temperature of the cooling device 26 within an appropriate temperature range (i.e., to control the cooling capacity within an appropriate range).

[0046] Furthermore, even if the temperature of cooling device 26 is controlled within an appropriate temperature range, if the post-fixing temperature of recording sheet S is higher than necessary, it becomes necessary to operate cooling device 26 at a high cooling capacity, which is undesirable from the viewpoint of energy saving and also undesirable from the viewpoint of noise generated by fan 26e. In this embodiment, the physical property values ​​(physical property information) of recording sheet S are estimated with high accuracy, and the temperature of fixing device 25 is controlled so that it is stable and equal to or lower than the fixing correction temperature that matches the physical property values ​​of recording sheet S, thereby preventing the cooling device 26 from being operated at a high cooling capacity. Therefore, it is preferable from the viewpoint of energy saving and noise generated by fan 26e.

[0047] If a new temperature sensor is provided to detect the post-fixing temperature of the recording sheet S, it is possible to directly acquire the post-fixing temperature of the recording sheet S. This makes it possible to control the temperature of the fixing device 25 with high precision and appropriately control the temperature of the cooling device 26 without having to use the paper physical property estimation unit 110 to estimate the physical property values ​​of the recording sheet S and calculate a fixing correction temperature suitable for the recording sheet S.

[0048] However, the installation of such a new temperature sensor generally leads to increased costs and larger size, contrary to the reduction in the number of parts and space saving. Moreover, if an attempt is made to detect the temperature of the recording sheet S immediately after fixing using a temperature sensor, it is difficult to detect the sheet temperature with high accuracy due to the influence of heat from the fixing device 25. Furthermore, in this embodiment, the downstream side of the cooling device 26 in the sheet conveying direction is immediately branched into a conveying path to the discharge roller pair 56 and a conveying path to the re-feed device 28, so it is not possible to secure an appropriate space for installing a temperature sensor.

[0049] Therefore, in this embodiment, the paper physical property estimating unit 110 estimates the physical property values ​​of the recording sheet S with high accuracy, and controls the temperature of the fixing device 25 and the temperature of the cooling device 26 based on the estimation results.

[0050] FIG. 7 is a flowchart showing the flow of temperature control of the fixing device 25 and the cooling device 26 in this embodiment. First, when a print job is input to the printer 100, the printer control unit 130 receives the input print job information (print mode, image information to be printed, number of copies to be printed, etc.) (S1). The print mode includes, for example, selection information for the paper thickness category (plain paper, medium weight, thick paper, etc.). In addition to the image data to be printed, the image information also includes setting data such as full color or monochrome, gloss setting, image quality priority, speed priority, etc.

[0051] The printer control unit 130 determines the paper passing mode (fixing temperature setting, printing speed, etc.) based on the print mode and image information included in the input print job information (S2), and starts printing when the temperature sensor of the fixing device 25 reaches the fixable temperature (S3). Specifically, for example, if the brand of the recording sheet S is POD gloss coated paper 128 g / m 2 In this case, the print mode will be the plain paper mode, so the fixing temperature setting (the target temperature of the heating roller temperature sensor 25h) will be set to 160°C, and the print speed will be set to 350mm / s so that 80 sheets (A4 landscape) can be printed per minute.

[0052] Meanwhile, the paper physical property estimation unit 110 obtains printing speed information from the printer control unit 130. The paper physical property estimation unit 110 also obtains temperature detection results during paper passage (temperature information of the fixing device 25 during paper passage) from temperature sensors 25h, 25i, and 25j installed in the fixing device 25. The paper physical property estimation unit 110 also obtains temperature detection results during paper passage (temperature information of the cooling device 26 during paper passage) from temperature sensor 26h installed in the cooling device 26. The paper physical property estimation unit 110 then estimates (predicts) the physical property values ​​of the recording sheet S based on this information (S4), and sends the estimated physical property values ​​(physical property information) of the recording sheet S to the temperature control unit 120.

[0053] The temperature control unit 120 calculates an appropriate fixing correction temperature at which the toner can be properly fixed based on the physical property values ​​(physical property information) of the recording sheet S input from the paper physical property estimation unit 110 (S5). This calculation of the fixing correction temperature is repeated for each predetermined number of recording sheets (for example, for each sheet). If it is determined that the calculated fixing correction temperature exceeds the current set fixing temperature (No in S6), the set fixing temperature is changed to the calculated fixing correction temperature (S7). Thereafter, in accordance with this change, the fan 26e of the cooling device 26 is changed to provide an optimal airflow (S8).

[0054] On the other hand, if it is determined in processing step S6 that the calculated fixing correction temperature is equal to or lower than the current fixing set temperature (Yes in S6), the fixing set temperature is not changed (S9). This is because the current fixing set temperature is set based on the paper thickness category included in the print job information, and if the estimated physical property value is set higher than the current fixing set temperature, there is a risk that toner hot offset or blocking on the paper output tray may worsen. Of course, if such a risk is acceptable, the fixing set temperature may be changed to the calculated fixing correction temperature even when the calculated fixing correction temperature is equal to or lower than the current fixing set temperature. In conjunction with this change, the fan 26e of the cooling device 26 may be changed to provide an optimal airflow.

[0055] In this embodiment, the above process continues until the print job is completed (S10).

[0056] To explain this with a specific example, if the physical property values ​​of the recording sheet S estimated by the paper physical property estimation unit 110 are, for example, 130 g / m 2 If the paper thickness is estimated to be 140 μm, and the smoothness is estimated to be 800 s, the fixing correction temperature calculated from these physical property values ​​is, for example, 155° C. In this case, if the current fixing temperature setting is 160° C., the fixing temperature setting is changed to 155° C., and the duty of the drive signal that drives fan 26e of cooling device 26 is reduced from 80% to 70%.

[0057] Next, the estimation process for estimating the physical property values ​​(physical property information) of the recording sheet S in the paper physical property estimation unit 110 will be described. The paper physical property estimation unit 110 of this embodiment estimates the physical property values ​​of the recording sheet S by executing an estimation program consisting of a model (trained model) optimized by machine learning using a computer. However, the paper physical property estimation unit 110 is not limited to this, and may estimate the physical property information of the recording sheet S using other methods (methods using computer programs programmed by humans). However, there are a wide variety of factors that affect the physical property information of the recording sheet S, and these factors often influence each other. For this reason, using an estimation program (trained model) created by machine learning is advantageous for achieving higher accuracy in estimation.

[0058] Furthermore, estimation of the physical property information of the recording sheet S is not limited to calculations based on a program using a trained model or a program programmed by a human, but may also be performed using a table describing the correspondence between the input and output of the program. For example, a table describing the relationship between the input of the trained model (information from the temperature sensors 25h, 25i, and 25j of the fixing device 25, information from the temperature sensor 26h of the cooling device, printing speed information, etc.) and the output (physical property information of the recording sheet S, such as basis weight, thickness, smoothness, and brand) is stored in advance in a storage unit. The table is then referenced to obtain an output value from an input value. However, if one attempts to obtain the physical property information of the recording sheet S with high accuracy, the number of combinations of input and output to be described in the table will become enormous, which can lead to problems such as difficulty in creating the table. Therefore, it is important to keep the number appropriate to prevent this.

[0059] A method for creating a trained model as an estimation program used in the paper physical property estimation unit 110 will be described. Note that, although the explanation here takes an example of a program executed by a computer device, this is merely an example, and the present invention is not limited to this, as long as the program is executed by a device capable of electronic calculations, etc. Furthermore, the computer device or device may be located either inside or outside the image forming apparatus.

[0060] The trained model in this embodiment estimates physical property information (basis weight, thickness, smoothness, brand) of the recording sheet S from information from the temperature sensors 25h, 25i, and 25j of the fixing device 25, information from the temperature sensor 26h of the cooling device 26, and printing speed information. Note that the printing speed information is not essential when the printing speed of the image forming device is constant.

[0061] A method for creating such a trained model involves, for example, passing a recording sheet to be learned, whose physical property information is known, using the various types of information obtained by printer 100 as input values, and creating a large amount of training data in which the known physical property information of the recording sheet is used as a correct answer label. Then, using a training dataset including these training data, a model is trained by supervised learning to generate the trained model described above.

[0062] The learning data may be collected by repeatedly passing many types of recording sheets S through a single printer 100. The learning data may also be collected from many printers 100 of the same model, in which case the data may be collected via a network from many printers 100 that are on the market and in use by users.

[0063] In this embodiment, learning data is input using a mathematical model called a neural network, and learning is performed to calculate an optimal model (trained model) for estimating physical property information of the recording sheet S. In machine learning, an algorithm automatically determines the parameters of the model so that the output for the input data is optimized.

[0064] In this embodiment, the physical property information (basis weight, thickness, smoothness) of the recording sheet S to be estimated is significantly affected by the temperature-related physical properties of the recording sheet S, specifically, the surface properties, material, basis weight, thermal conductivity, and other physical properties of the recording sheet S, as well as environmentally dependent values ​​such as moisture content. This can be understood from the fact that the target value (optimum fixing temperature) for the fixing temperature differs depending on the brand of recording sheet S, as shown in FIG. 8. For example, coated paper has a smaller surface roughness than plain paper, making it difficult to achieve an anchoring effect, and therefore requires more heat to fix the toner to the sheet. Similarly, synthetic paper, metallic paper, and plastic media also have a smaller surface roughness and require more heat. Similarly, the amount of heat required to fix the toner varies depending on the surface material, thermal conductivity, and other factors.

[0065] Furthermore, even when the target fixing temperature and recording sheet basis weight are the same, the temperature after fixing varies depending on the smoothness of the recording sheet. This is because, even when the temperature of the fixing belt is the same, if the smoothness differs, the contact area between the fixing belt and the recording sheet will differ, and the amount of heat transferred will also differ. Therefore, if the target fixing temperature (set fixing temperature) is changed depending on the type of recording sheet S, or if the smoothness of the recording sheet differs even when the target fixing temperature is the same, the temperature of the recording sheet S after cooling will also vary.

[0066] The above means that the temperature of the fixing device 25 and the temperature of the cooling device 26 change depending on the type (difference in physical property information) of the recording sheet S. Therefore, by performing machine learning using learning data including the temperature of the fixing device 25 and the temperature of the cooling device 26, it is possible to obtain a trained model that can estimate the physical property information of the recording sheet S with high accuracy.

[0067] Below, an example of a trained model for estimating physical property information of the recording sheet S will be described. Table 1 shows some of the data used to create the trained model. As shown in Table 1, data No. 1 to No. 24 are used as learning data (training data) for creating the trained model, and data No. 25 to No. 30 are used as verification data (test data).

[0068] [Table 1]

[0069] In this experimental example, a machine learning model using an artificial neural network (ANN) as shown in Figure 9 was constructed to predict paper physical properties using temperatures measured with an experimental device of the same model as the printer of this embodiment. This model is composed of a large number of interconnected neurons, with the first layer being called the input layer, the last layer being called the output layer, and the intermediate layer being called the hidden layer. Input information is propagated forward through the artificial neural network. The accuracy of the model is evaluated using the mean squared error (MSE) and the coefficient of determination R 2 The error of the predicted value relative to the actual measured value was evaluated using

[0070] When constructing a paper physical property prediction model, heating roller temperature sensor 25h, fixing roller temperature sensor 25i, pressure roller temperature sensor 25j, cooling device temperature sensor 26h, and linear speed are input to the input layer, and paper physical property values ​​(basis weight, thickness, smoothness) are input to the output layer and learned to construct the paper physical property prediction model. When predicting paper physical properties, heating roller temperature sensor 25h, fixing roller temperature sensor 25i, pressure roller temperature sensor 25j, cooling device temperature sensor 26h, and linear speed are input to the input layer of the paper physical property prediction model, and predicted paper physical property values ​​(basis weight, thickness, smoothness) are obtained.

[0071] Figures 10(a) to (c) are graphs plotting the output results (estimation results) when verification data (test data) No. 25 to No. 30 are input to the trained model created in this example.

[0072] 10(a) shows the output result (estimated result) of the basis weight of the recording sheet S on the horizontal axis and the known basis weight of the recording sheet S on the vertical axis, with the plot closer to a straight line in the graph indicating higher estimation accuracy (precision). As shown in FIG. 10(a), according to the trained model of the embodiment, for all of recording sheets S No. 25 to No. 30, the basis weight as physical property information of the recording sheet S can be estimated with high accuracy based on the temperature of the fixing device 25 when the recording sheet S passes (output value of temperature sensors 25h, 25i, 25j), the temperature of the cooling device 26 when the recording sheet S passes (output value of temperature sensor 26h), and linear speed information (conveying speed of the recording sheet S: printing speed information).

[0073] 10(b), the horizontal axis represents the output result (estimated result) of the thickness of the recording sheet S, and the vertical axis represents the known thickness of the recording sheet S, and the closer the plot is to a straight line in the graph, the higher the estimation accuracy (precision). As shown in FIG. 10(b), according to the trained model of the embodiment, for all of recording sheets S No. 25 to No. 30, the thickness as physical property information of the recording sheet S can be estimated with high accuracy based on the temperature of the fixing device 25 when the recording sheet S passes (output value of temperature sensors 25h, 25i, 25j), the temperature of the cooling device 26 when the recording sheet S passes (output value of temperature sensor 26h), and linear speed information (conveying speed of the recording sheet S: printing speed information).

[0074] 10(c) shows the output result (estimated result) of the smoothness of the recording sheet S on the horizontal axis and the known smoothness of the recording sheet S on the vertical axis, with the plot closer to a straight line in the graph indicating higher estimation accuracy (precision). As shown in FIG. 10(c), with the exception of one of recording sheets S No. 25 to No. 30, the trained model of the embodiment was able to estimate the smoothness as physical property information of the recording sheet S with high accuracy based on the temperature of the fixing device 25 when the recording sheet S passed (output value of temperature sensors 25h, 25i, 25j), the temperature of the cooling device 26 when the recording sheet S passed (output value of temperature sensor 26h), and linear speed information (conveying speed of the recording sheet S: printing speed information).

[0075] 11(a) is a graph plotting the temperature of the paper discharge section using an existing estimation program that estimates the temperature of the paper discharge section (the temperature of the recording sheet S when it is discharged to the paper discharge tray 57) from input values ​​including the temperature of the fixing device 25 (output values ​​of temperature sensors 25h, 25i, 25j) and physical property information of the recording paper (basis weight, thickness, smoothness). The graphs of Figures 11(a) to 11(c) have the horizontal axis representing the estimated temperature of the paper discharge section by the known estimation program and the vertical axis representing the actually measured temperature of the paper discharge section, with the plot closer to the solid line in the graph representing higher estimation accuracy (precision), and the range indicated by the dashed line in the graph representing the accuracy of the estimation result.

[0076] FIG. 11(a) plots the estimated results of the discharge section temperature when the estimated results of physical property information (basis weight, thickness, smoothness) of the recording sheet S estimated using the trained model of this embodiment are input. FIG. 11(b) plots the estimated results of the discharge section temperature when no physical property information about the recording sheet S is input. FIG. 11(c) plots the estimated results of the discharge section temperature when the actual measurement results of the physical property information about the same recording sheet S as in FIG. 11(a) are input. Comparing these graphs, the estimation accuracy of the discharge section temperature is superior when the estimated results using the trained model of this embodiment as the physical property information of the recording sheet S are used compared to when no physical property information is input, and also achieves accuracy as high as when actual measurements are used as the physical property information of the recording sheet S.

[0077] FIG. 12(a) shows the temperature profiles of the cooling device temperature sensor 26h, the heating roller temperature sensor 25h, the fixing roller temperature sensor 25i, and the pressure roller temperature sensor 25j when the fixing temperature is set to 120° C. and 500 sheets of 45K paper are continuously fed. FIG. 12(b) shows the temperature profiles of the cooling device temperature sensor 26h, the heating roller temperature sensor 25h, the fixing roller temperature sensor 25i, and the pressure roller temperature sensor 25j when the fixing temperature is set to 120° C. and 500 sheets of 70K paper are continuously fed. FIG. 12(c) shows the temperature profiles of the cooling device temperature sensor 26h, the heating roller temperature sensor 25h, the fixing roller temperature sensor 25i, and the pressure roller temperature sensor 25j when the fixing temperature is set to 160° C. and 500 sheets of 45K paper are continuously fed. FIG. 12(d) shows the temperature profiles of the cooling device temperature sensor 26h, the heating roller temperature sensor 25h, the fixing roller temperature sensor 25i, and the pressure roller temperature sensor 25j when the fixing temperature is set to 160° C. and 500 sheets of 70K paper are continuously fed.

[0078] Although 45K paper and 70K paper are recording sheets with approximately the same smoothness, their basis weights differ, resulting in different thermal capacities. Therefore, the thinner the recording sheet, the higher the temperature of the recording sheet, and the temperature of the cooling device 26 (the temperature of the heat pipe 26a) is higher for 45K paper than for 70K paper. Furthermore, the amount of heat transferred from the fixing roller 25c to the pressure roller 25e via the fixing belt 25a also increases as the recording sheet becomes thinner, so the temperature of the pressure roller 25e increases as the recording sheet becomes thinner. As a result, the temperature of the pressure roller 25e is higher for 45K paper than for 70K paper. It is believed that the trained model for estimating physical property information of recording sheets in this embodiment performs estimation processing by reflecting such differences in the temperature of the cooling device 26 and the temperature of the fixing device 25 (pressure roller temperature) in the differences in basis weight and paper thickness.

[0079] Figure 13(a) shows the temperature profiles of the cooling device temperature sensor 26h, heating roller temperature sensor 25h, fixing roller temperature sensor 25i, and pressure roller temperature sensor 25j when the fixing temperature is set to 120°C and 500 sheets of POD gloss coated 100 paper are continuously passed through. FIG. 13(b) shows the temperature profiles of the cooling device temperature sensor 26h, the heating roller temperature sensor 25h, the fixing roller temperature sensor 25i, and the pressure roller temperature sensor 25j when the fixing temperature is set to 120° C. and 500 sheets of 90K paper are continuously fed. Figure 13(c) shows the temperature profiles of the cooling device temperature sensor 26h, heating roller temperature sensor 25h, fixing roller temperature sensor 25i, and pressure roller temperature sensor 25j when the fixing temperature is set to 160°C and 500 sheets of POD gloss coated 100 paper are passed through continuously. FIG. 13(d) shows the temperature profiles of the cooling device temperature sensor 26h, the heating roller temperature sensor 25h, the fixing roller temperature sensor 25i, and the pressure roller temperature sensor 25j when the fixing temperature is set to 160° C. and 500 sheets of 90K paper are continuously fed.

[0080] POD Gloss Coated 100 paper and 90K paper are recording sheets with approximately the same basis weight but different smoothness. In this case, the heat capacity of the paper is approximately the same, but the difference in surface roughness results in different contact thermal resistance with the fixing belt 25a of the fixing device 25 and the heat pipe 26a of the cooling device 26. Therefore, the smoother the recording sheet, the higher the temperature of the recording sheet, and the temperature of the cooling device 26 (the temperature of the heat pipe 26a) is higher for POD Gloss Coated 100 paper than for 90K paper. However, since the thickness of the recording sheets is approximately the same, the amount of heat transferred from the fixing roller 25c via the fixing belt 25a to the pressure roller 25e does not differ in the temperature of the pressure roller 25e. In this embodiment, the trained model for estimating physical property information of the recording sheet is thought to perform estimation processing by reflecting the difference in smoothness, which reflects the difference in the temperature of the cooling device 26 and the same temperature of the fixing device 25 (pressure roller temperature).

[0081] For reference, the difference in surface properties between plain paper and coated paper is shown in Figure 14.

[0082] The above description is merely an example, and each of the following aspects provides unique effects. [First aspect] The first aspect is an image forming apparatus (e.g., printer 100) having a fixing means (e.g., fixing device 25) that heats and fixes an image on a recording sheet S on which the image has been formed, and a fixing temperature control means (e.g., paper physical property estimation unit 110, temperature control unit 120) that controls the temperature of the fixing means, and further having a cooling means (e.g., cooling device 26) that cools the recording sheet after fixing by the fixing means, a fixing temperature detection means (e.g., heating roller temperature sensor 25h, fixing roller temperature sensor 25i, pressure roller temperature sensor 25j) that detects the temperature of the fixing means when the recording sheet passes through the fixing means, and a cooling temperature detection means (cooling device temperature sensor 26h) that detects the temperature of the cooling means when the recording sheet passes through the cooling means, and the fixing temperature control means controls the temperature of the fixing means based on the detection results of the fixing temperature detection means and the cooling temperature detection means. Conventional image forming apparatuses determine the paper type of paper (recording sheet) before printing based on the results of measurements (detections) of the paper's thickness, basis weight, and surface properties using various sensors, and then print on the paper using printing conditions corresponding to the determination results. However, with methods that directly obtain physical property information such as the thickness, basis weight, and surface properties of the paper before printing using sensors, it is difficult to accurately obtain physical property information of the recording sheet from the sensor's detection output due to variations in sensor measurements and individual differences between sheets of the same type. Therefore, even when using a paper type determination engine, which is a trained model created through machine learning, it is difficult to accurately determine the paper type information because the input is the detection output of such a low-accuracy sensor. As a result, printing may not be performed under printing conditions appropriate for the type of recording sheet to be printed. In particular, when attempting to control the temperature of the fixing unit to match the paper, inaccurate determination of the paper type information can easily lead to problems such as the fixing unit temperature being incompatible with the paper, causing paper blocking due to an excessively high fixing temperature, or poor fixing due to an excessively low fixing temperature. As a result of research, the inventors have found that physical property information of a recording sheet can be accurately estimated using the detection results of the temperature of the fixing means when the recording sheet passes and the detection results of the temperature of the cooling means that cools the recording sheet after fixing. More specifically, they have found that by using these detection results, physical property information of the recording sheet related to the temperature of the fixing means appropriate for that recording sheet can be accurately estimated. As a result, according to this aspect, in which the temperature of the fixing means is controlled based on the detection results of the fixing temperature detection means and the cooling temperature detection means, the temperature of the fixing means can be accurately controlled to be appropriate for the recording sheet on which an image is formed, thereby making it possible to eliminate the above-mentioned problems.

[0083] [Second mode] The second aspect is characterized in that the first aspect has a cooling temperature control means (e.g., a paper physical property estimation unit 110, a temperature control unit 120) that adjusts the temperature of the cooling means, and the cooling temperature control means controls the temperature of the cooling means based on the detection results of the fixing temperature detection means and the cooling temperature detection means. When attempting to control the temperature of the cooling means to a temperature suitable for the recording sheet, if the accuracy of determining the physical property information of the recording sheet is poor, the temperature of the cooling means will not be suitable for the recording sheet, and problems such as the temperature of the cooling device being too high and causing paper blocking, or the temperature of the cooling device being too low and thus countering energy saving and generating noise, are likely to occur. As described above, it has been found that the physical property information of the recording sheet can be accurately estimated using the detection results of the temperature of the fixing means when the recording sheet passes and the detection results of the temperature of the cooling means that cools the recording sheet after fixing when the recording sheet passes. As a result, according to this aspect in which the temperature of the cooling means is controlled based on the detection results of the fixing temperature detection means and the cooling temperature detection means, the temperature of the cooling means can be accurately controlled to be a temperature suitable for the recording sheet on which an image is formed, and the above-mentioned problems can be resolved.

[0084] [Third aspect] The third aspect is an image forming apparatus (e.g., printer 100) having a fixing means (e.g., fixing device 25) that heats and fixes an image on a recording sheet on which the image has been formed, a cooling means (e.g., cooling device 26) that cools the recording sheet after fixing by the fixing means, and a cooling temperature control means (e.g., paper physical property estimation unit 110, temperature control unit 120) that adjusts the temperature of the cooling means, and further having a fixing temperature detection means (e.g., heating roller temperature sensor 25h, fixing roller temperature sensor 25i, pressure roller temperature sensor 25j) that detects the temperature of the fixing means when the recording sheet passes through the fixing means, and a cooling temperature detection means (cooling device temperature sensor 26h) that detects the temperature of the cooling means when the recording sheet passes through the cooling means, and characterized in that the cooling temperature control means controls the temperature of the cooling means based on the detection results of the fixing temperature detection means and the cooling temperature detection means. When attempting to control the temperature of the cooling means to a temperature suitable for the recording sheet, if the accuracy of determining the physical property information of the recording sheet is poor, the temperature of the cooling means will not be suitable for the recording sheet, and problems such as the temperature of the cooling device being too high and causing paper blocking, or the temperature of the cooling device being too low and thus countering energy saving and generating noise, are likely to occur. As described above, it has been discovered that the physical property information of a recording sheet can be accurately estimated using the detection results of the temperature of the fixing means when the recording sheet passes and the detection results of the temperature of the cooling means that cools the recording sheet after fixing when the recording sheet passes. As a result, according to this aspect, in which the temperature of the cooling means is controlled based on the detection results of the fixing temperature detection means and the cooling temperature detection means, the temperature of the cooling means can be accurately controlled to be a temperature suitable for the recording sheet on which an image is formed, and the above-mentioned problems can be resolved.

[0085] [Fourth aspect] The fourth aspect is characterized in that, in either the second or third aspect, the cooling means includes a heat absorption member (e.g., heat pipe 26a, cooling roller 27a, metal plate 29a, 29b) that absorbs heat from the recording sheet passing through, and a cooling member (e.g., heat dissipation fin 26d and fan 26e, chiller 27g, heat sink 29c and fan 29d) that air-cools or liquid-cools the heat absorption member, and the cooling temperature control means controls the cooling capacity of the cooling member to control the temperature of the cooling means. This makes it easy to control the temperature of the cooling means.

[0086] [Fifth mode] A fifth aspect is the fourth aspect, characterized in that the heat absorbing member is a heat pipe. This makes it possible to cool the recording sheet with high cooling capacity.

[0087] [Sixth aspect] A sixth aspect is the fourth aspect, characterized in that the heat absorbing member is a guide member that guides a recording sheet passing through. This allows the recording sheet to be cooled with a relatively simple configuration.

[0088] [Seventh aspect] An estimation device (e.g., paper physical property estimation unit 110) that estimates physical property information of a recording sheet on which an image is recorded by an image forming device (e.g., printer 100) that includes fixing means (e.g., fixing device 25) that heat-fixes an image onto a recording sheet on which an image has been formed, and cooling means (e.g., cooling device 26) that cools the recording sheet after fixing by the fixing means, is characterized in that it estimates the physical property information of the recording sheet based on temperature information of the fixing means when the recording sheet passes through the fixing means and temperature information of the cooling means when the recording sheet passes through the cooling means. According to this aspect, as described above, the physical property information of the recording sheet can be accurately estimated using the detection results of the temperature of the fixing means when the recording sheet passes and the detection results of the temperature of the cooling means that cools the recording sheet after fixing when the recording sheet passes.

[0089] [Eighth aspect] An eighth aspect is the seventh aspect, characterized in that the physical property information is at least one of basis weight, thickness, and smoothness of the recording sheet. This makes it possible to obtain information about the physical properties of the recording sheet, which is useful for controlling the temperature of the fixing device and the temperature of the cooling device so as to suit the recording sheet.

[0090] [Ninth aspect] The ninth aspect is the seventh or eighth aspect, characterized in that the physical property information of the recording sheet is estimated based also on the detection results of an optical sensor that detects the optical properties of the recording sheet. This makes it possible to obtain more accurate physical property information about the recording sheet.

[0091] [Tenth aspect] The tenth aspect is characterized in that, in any of the seventh to ninth aspects, the estimation is performed using an estimation program that has been trained using a plurality of learning data including temperature information of the fixing means when a learning target recording sheet, whose physical property information is known, passes through the fixing means of the learning target image forming device, and temperature information of the cooling means when the learning target recording sheet passes through the cooling means of the learning target image forming device. According to this embodiment, even when the physical property information of the recording sheet S is affected by a wide variety of factors that affect the temperature of the fixing means and the temperature of the cooling means, and these factors affect each other, it is possible to estimate the physical property information of the recording sheet with high accuracy. [Explanation of symbols]

[0092] 10: Intermediate transfer belt 16: Secondary transfer opposing roller 17: Belt cleaning device 18: Imaging unit 20: Tandem image forming unit 21: Optical writing device 22: Secondary transfer device 25: Fixing device 25a: Fixing belt 25b: Heating roller 25c: Fuser roller 25d: Fixing heater 25e: Pressure roller 25f: Pressure heater 25g: Pressure roller fan 25h: Heating roller temperature sensor 25i: Fuser roller temperature sensor 25j: Pressure roller temperature sensor 26: Cooling device 26a: Heat pipe 26b: Heat absorption part 26c: Heat dissipation part 26d: Heat dissipation fin 26e: Fan 26h: Cooling device temperature sensor 27: Cooling device 27a: Cooling roller 27b: conveyor belt 27c, 27d: Support rollers 27e, 27f: Guide roller 27g: Chiller 27h: Cooling device temperature sensor 28:Retransmission device 29: Cooling device 29a, 29b: Sheet metal 29c: Heat sink 29d: Fan 29h: Cooling device temperature sensor 40: Photoreceptor 42: Paper feed roller 49: Registration roller pair 50: Toner bottle 56: Discharge roller pair 57: Paper output tray 59: Developing device 60: Charging device 61: Drum cleaning device 62: Primary transfer roller 100: Printer 110: Paper property estimation department 120: Temperature control unit 130: Printer control unit S: Recording sheet [Prior art documents] [Patent documents]

[0093] [Patent Document 1] Patent Publication No. 2021-060375

Claims

1. A fixing means for heat-fixing the image formed on the recording sheet; a cooling means for cooling the recording sheet after fixing by the fixing means; An image forming apparatus having a cooling temperature control unit that adjusts the temperature of the cooling unit, a fixing temperature detection means for detecting the temperature of the fixing means when the recording sheet passes through the fixing means; a cooling temperature detection means for detecting the temperature of the cooling means when the recording sheet passes through the cooling means; an estimation unit that estimates physical property information of the recording sheet based on the detection results of the fixing temperature detection unit and the cooling temperature detection unit, the cooling means includes a heat absorbing member that absorbs heat from a passing recording sheet, and a cooling member that cools the heat absorbing member with air or liquid, The image forming apparatus according to claim 1, wherein the cooling temperature control means controls the temperature of the cooling means by controlling the cooling capacity of the cooling member based on the physical property information estimated by the estimation means.

2. In the image forming apparatus according to claim 1, The image forming apparatus according to claim 1, wherein the estimation means estimates physical property information of the recording sheet based on a printing speed of the recording sheet.

3. In the image forming apparatus according to claim 1 or 2, a fixing temperature control means for controlling the temperature of the fixing means, The image forming apparatus according to claim 1, wherein the fixing temperature control means controls a temperature of the fixing means based on the physical property information estimated by the estimation means.

4. 4. The image forming apparatus according to claim 1, The image forming apparatus according to claim 1, wherein the physical property information is at least one of basis weight, thickness, and smoothness of the recording sheet.

5. 5. The image forming apparatus according to claim 1, The image forming apparatus according to claim 1, wherein the estimation means estimates physical property information of the recording sheet based on a detection result of an optical sensor that detects optical characteristics of the recording sheet.

6. 6. The image forming apparatus according to claim 1, The image forming apparatus is characterized in that the estimation means estimates the physical property information of the recording sheet using an estimation program trained using a plurality of learning data including temperature information of the fixing means of the training target image forming device when the training target recording sheet, whose physical property information is known, passes through the fixing means of the training target image forming device, and temperature information of the cooling means of the training target recording sheet when the training target recording sheet passes through the cooling means of the training target image forming device.

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