Image formation apparatus

Abstract

To suppress deterioration of image quality due to a delay of a replacement timing of a fixation device by highly accurately predicting a product life of the fixation device for each individual.SOLUTION: There is provided an image formation apparatus including a fixation device that fixes a toner image onto a recording medium. Therein the fixation device includes: a heating rotor that heats a recording material; and a pressuring rotor that abuts with the heating rotor so as to form a nip part, and pressurizes the recording material, and in a longitudinal direction of the heating rotor. The image formation apparatus includes: storage means for storing information on pressuring force corresponding to a plurality of areas of the nip part; and determination means for determining a replacement timing of the fixation device on the basis of the information stored in the storage means.SELECTED DRAWING: Figure 5

Description

Technical Field

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

Background Art

[0002] An image forming apparatus that forms a toner image forms a toner image on a recording material (also referred to as recording paper, a recording medium, or a sheet-like medium), and fixes the image on the recording material by heating and pressing it with a fixing device.

[0003] For example, in a fixing device using a fixing belt, a nip portion is formed between the fixing belt and a pressure roller, and the toner image is fixed on the recording material by sandwiching and conveying the recording material between the nip portions.

[0004] In order to form the above-described nip portion, the pressure roller presses against the fixing belt with a high surface pressure. For this reason, the recording material that attempts to pass through the nip portion is strongly pressed against the fixing belt by the pressure roller. At the edge portion of the recording material, a step occurs between the portion with the recording material and the portion without the recording material, so that stress is particularly concentrated and scratches (hereinafter referred to as edge scratches) may occur on the surfaces of the fixing belt and the pressure roller.

[0005] When the recording material is repeatedly passed through the nip portion in this way, the edge scratches progress, and streak-like scratch marks are generated on the surface of the fixing belt. When the toner image is fixed in a state where these streak-like scratch marks are generated on the fixing belt, the glossiness of the region of the toner image corresponding to the scratch mark portion decreases, leading to a deterioration in image quality. Therefore, when the wear of the fixing belt progresses, it is desirable to determine that the fixing belt has reached its wear life and replace the fixing belt or the fixing unit including the fixing belt.

[0006] In the fixing device described in Patent Document 1, the progress of the wear life is counted based on the size, type, number of sheets, and printing orientation of the printed paper. When the count value reaches a predetermined value, the replacement time of the fixing belt is notified to prompt the user to replace the fixing belt. Further, in the fixing device described in Patent Document 2, the parameters related to the wear of the fixing belt are not limited to those described above, and it is shown that the way the wear of the fixing belt progresses differs depending on the state of the temperature distribution of the fixing belt when transporting the recording material. Therefore, by accurately notifying the replacement time of the fixing belt in consideration of the state of the temperature distribution of the fixing belt, the replacement frequency of the fixing belt is suppressed.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] The fixing device forms a nip portion by a heating rotating body (for example, a fixing belt) and a pressure rotating body. In the longitudinal direction of the heating rotating body, it is desirable that the pressure in the nip portion is uniform. However, due to variations occurring during the manufacture of the fixing device, a pressure difference in the nip portion in the longitudinal direction is generated. This pressure difference in the nip portion in the longitudinal direction varies from one fixing device to another.

[0009] For example, in the longitudinal direction, when the pressure in a predetermined region of the nip portion is high and a cob portion repeatedly passes through the predetermined region, cob scratches are generated on the surface of the heating rotating body earlier than normal, leading to a deterioration in image quality and grade.

[0010] Therefore, an object of the present invention is to suppress a deterioration in image quality due to a delay in the replacement timing of a fixing device by accurately predicting the life of each fixing device.

Means for Solving the Problems

[0011] In view of the above problems, an image forming apparatus according to the present invention is an image forming apparatus having a fixing device that fixes a toner image on a recording material, wherein the fixing device includes a heating rotating body that heats the recording material, and a pressure applying rotating body that forms a nip portion by contacting the heating rotating body and applies pressure to the recording material, and in the longitudinal direction of the heating rotating body, there are provided storage means for storing information regarding the pressure applied to a plurality of regions of the nip portion, and determination means for determining the replacement timing of the fixing device based on the information stored by the storage means.

Effects of the Invention

[0012] According to the present invention, the replacement timing of the fixing device can be accurately predicted, and a delay in the replacement timing of the fixing device can be suppressed.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Best Mode for Carrying Out the Invention

[0014] <Image forming apparatus> FIG. 1 is a cross-sectional view of a color electrophotographic printer (hereinafter referred to as a printer) as an example of an image forming apparatus equipped with a fixing device according to the present embodiment, and is a cross-sectional view along the conveyance direction of a recording material (sheet).

[0015] The printer shown in FIG. 1 includes image forming units 10 for each color of Y (yellow), M (magenta), C (cyan), and Bk (black). The photosensitive drum 11 is pre-charged by a charger 12. Thereafter, the photosensitive drum 11 forms a latent image by a laser scanner 13. The latent image becomes a toner image by a developing device 14. The toner image on the photosensitive drum 11 is sequentially transferred to, for example, an intermediate transfer belt 31 which is an image carrier, by a primary transfer blade 17. After the transfer, the toner remaining on the photosensitive drum 11 is removed by a cleaner 15. As a result, the surface of the photosensitive drum 11 becomes clean and is ready for the next image formation.

[0016] On the other hand, the recording material P is fed one by one from a paper feed cassette 20 or a multi-sheet feed tray 25 and fed into a registration roller pair 23. Then, the registration roller pair 23 feeds the recording material P between the intermediate transfer belt 31 and a secondary transfer roller 35 in synchronization with the toner image on the intermediate transfer belt 31.

[0017] The color toner image on the intermediate transfer belt 31 is transferred to the recording material P by, for example, a secondary transfer roller 35 which is a transfer member. Thereafter, the toner image on the sheet P is fixed to the sheet P by being heated and pressurized by a fixing device 40 (FIG. 2) having a heating unit on the inner surface side of the fixing film.

[0018] <Fixing device> Next, the fixing device according to this embodiment will be described. As shown in FIG. 2, in this embodiment, a fixing device using a belt heating method is employed. The recording material P is nipped and conveyed between a fixing belt 41, which is a rotatable endless belt provided so as to be replaceable as a heating rotating member, and a pressure roller 44, which is a driving rotating member, and the toner image is fixed. The heater 43 is a ceramic heater (hereinafter referred to as the heater) as a heating member for heating the image on the recording material. This heater 43 is basically composed of an elongated thin plate-shaped ceramic substrate in the longitudinal direction (the direction perpendicular to the plane of FIG. 2) intersecting the conveyance direction of the recording material, and an energization heating resistor layer provided on this substrate surface. By energizing the heating resistor layer, it becomes a heater with a low heat capacity that raises the temperature with a steep rising characteristic as a whole. Further, according to the width size in the longitudinal direction of the recording material P, which is the recording material, a configuration is provided for switching the energization region.

[0019] The fixing belt 41 is a cylindrical (endless) heat-resistant belt as a heating member for transferring heat, and is loosely externally fitted to a support member including the heater 43. The fixing film 41 in this embodiment has a four-layer composite structure of a surface layer 41a, an elastic layer 41c, a base metal layer (base layer) 41b, and an inner surface layer 41d as shown in FIG. 3.

[0020] As the surface layer 41a, a fluororesin material with a thickness of 100 μm or less, preferably 10 to 70 μm can be used. Examples of the fluororesin layer include PTFE (polytetrafluoroethylene), PFA (perfluoroalkoxyalkane), etc. In this embodiment, a PFA tube with a thickness of 20 μm was used. The base metal layer 41b can use a metal film such as SUS or nickel as a heat-resistant material with a thickness of 100 μm or less, preferably 50 μm or less and 20 μm or more in order to improve the quick start property. In this embodiment, a cylindrical nickel metal belt with a thickness of 30 μm and a diameter of 25 mm was used.

[0021] The elastic layer 41c is sandwiched between the surface layer 41a and the base layer 41b. Further, in order to reduce the heat capacity and improve the quick start performance, a filler for enhancing the thermal conductivity is added. In this embodiment, a silicone rubber with a rubber hardness of 10 degrees (JIS-A), a thermal conductivity of 1.3 W / m·K, and a thickness of 200 μm is used.

[0022] The inner layer 41d is suitably made of a resin having high durability and high heat resistance such as a polyimide resin. In this embodiment, a polyimide precursor solution obtained by reacting substantially equimolar amounts of an aromatic tetracarboxylic dianhydride or its derivative and an aromatic diamine in an organic polar solvent is used. This solution is applied to the inner surface of the base metal layer 41b, dried, and heated to form a polyimide resin layer by a dehydration ring-closing reaction, which is used as the inner layer 41d.

[0023] Specifically, in this embodiment, as the polyimide precursor solution, an N-methyl-2-pyrrolidone solution of a polyimide precursor composed of 3,3‘,4,4’-biphenyltetracarboxylic dianhydride and paraphenylenediamine is used. Then, a polyimide resin with a thickness of 15 μm is formed and used as the inner layer 41d.

[0024] The pressure roller 44 as a pressure rotating body is a heat-resistant elastic roller as a pressure member, and is composed of a core metal and an elastic layer made of a heat-resistant rubber such as silicone rubber or fluororubber, or a foam of silicone rubber. Both ends of the core metal are rotatably supported by bearings. The fixing belt 41 and the heater 43 are arranged above the pressure roller 44 in parallel with the pressure roller 44 on the heater 43 side and are pressed by a pressing member (not shown). Thereby, through the fixing belt 41, the lower surface of the heater 43 and the upper surface of the pressure roller 44 are pressed against each other against the elasticity of the roller elastic layer to form a fixing nip portion (nip portion) N with a predetermined width as a heating portion.

[0025] The pressure roller 44 receives a rotation command of the driving means M from the control circuit, and is rotationally driven at a predetermined rotational peripheral speed in the direction of the arrow in Fig. 2 (counterclockwise) by the driving means M and the transmission means G such as gears. By the rotational driving of this pressure roller 44, a rotational force acts on the cylindrical fixing belt 41 due to the pressing frictional force at the fixing nip portion N between the pressure roller 44 and the fixing belt 41. Then, the fixing belt 41 comes into close contact with the downward surface of the heater 43 and slides while being driven to rotate in the direction of the arrow in Fig. 2 (clockwise). Here, the support member of the fixing belt 41 also serves as a rotational guide member for the cylindrical fixing belt 41.

[0026] In this way, the pressure roller 44 is rotationally driven, and accordingly, the cylindrical fixing belt 41 is driven to rotate in a driven manner. Then, in a state where the heater 43 is energized and the heater 43 rapidly heats up to reach a predetermined temperature and is temperature-controlled, a recording material P carrying an unfixed toner image T is introduced between the fixing belt 41 and the pressure roller 44 at the nip portion N. Then, the toner image-carrying side surface of the recording material P comes into close contact with the outer surface (surface) of the fixing belt 41, and the recording material P is sandwiched and conveyed at the nip portion N together with the fixing belt 41.

[0027] In this sandwiching and conveying process, the recording material P is heated by the heat of the fixing belt 41 heated by the heater 43, and the unfixed toner image T on the recording material P is heated and pressed on the recording material P to be melted and fixed. Then, the recording material P that has passed through the nip portion N is separated from the surface of the fixing belt 41 by the curvature and discharged and conveyed.

[0028] In Fig. 2, 45a is a contact thermometer (thermistor) behind the heater, which measures the temperature of the heater 43. As shown in Fig. 4, the heater-back thermistor 45a is arranged at three locations in the longitudinal direction, namely, a central portion 45a1, and both end portions 45a2 and 45a3. The central portion 45a1 is at the center in the longitudinal direction, and the both end portions 45a2 and 45a3 are arranged at positions ±150 [mm] from the center in the longitudinal direction.

[0029] Also, 45b is a contact thermometer (thermistor) on the back of the fixing belt, and measures the temperature of the inner surface (inner circumferential surface, back surface) of the fixing belt 41 heated by the heater 43. As shown in FIG. 4, the fixing belt back thermistor 45b is arranged at three positions in the longitudinal direction: a central portion 45b1, and both end portions 45b2 and 45b3. The central portion 45b1 is at the center in the longitudinal direction, and the both end portions 45b2 and 45b3 are arranged at positions ±150 [mm] from the center in the longitudinal direction. And these temperature detection results are configured to be passed to temperature control means (not shown).

[0030] The central portion 45b1 of the fixing belt back thermistor 45b is a first temperature detection means for detecting the temperature of the fixing belt 41 in a first region where a recording material having a predetermined width narrower than the maximum width size of the recording material that can be introduced into the apparatus in the longitudinal direction of the fixing belt 41 passes through the nip portion.

[0031] Also, both end portions 45b2 and 45b3 of the fixing belt back thermistor 45b are a second temperature detection means and a third temperature detection means for detecting the temperatures of one end side and the other end side of the fixing belt 41 in a second region outside the first region in the longitudinal direction of the fixing belt 41.

[0032] Note that the longitudinal positions of these thermistors may be changed as necessary.

[0033] In FIG. 2, 46 is a heater holder, which is a member for holding the heater 43 that generates heat at a high temperature. In this embodiment, the diameters of the fixing belt 41 and the pressure roller 44 are set to 30 [mm]. And by bringing the fixing belt 41 and the pressure roller 44 into contact with a pressing force of a total pressure of 30 [kgf], about 8 [mm] is ensured as the width of the nip portion N (in the conveyance direction of the recording material P). Here, the process speed of this image forming apparatus is 250 [mm / s], and the productivity of A4 size plain paper is 60 ppm both for monochrome and color.

[0034] This fixing device adjusts the input power of the heater 43 so that the back surface thermistor 45b1 of the central fixing belt reaches 170 [°C]. Then, the temperature control of the back surface thermistor 45b1 of the central fixing belt is changed according to the environment where the image forming apparatus is installed and the type of paper being fed.

[0035] When the environment where the image forming apparatus is set is 23 [°C] and plain paper 1 (81 g / m² or less) is being fed, it is set so that the back surface thermistor 45b1 of the central fixing belt reaches 170 [°C]. And when the environment where the image forming apparatus is set is 23 [°C] and plain paper 2 (105 g / m² or less) is being fed, it is set so that the back surface thermistor 45b1 of the central fixing belt reaches 180 [°C].

[0036] When the environment where the image forming apparatus is set is 15 [°C] and plain paper 1 (81 g / m² or less) is being fed, it is set so that the back surface thermistor 45b1 of the central film reaches 180 [°C]. And when the environment where the image forming apparatus is set is 15 [°C] and plain paper 2 (105 g / m² or less) is being fed, it is set so that the back surface thermistor 45b1 of the central film reaches 190 [°C].

[0037] When the environment where the image forming apparatus is set is 30 [°C] and plain paper 1 (81 g / m² or less) is being fed, it is set so that the back surface thermistor 45b1 of the central fixing belt reaches 160 [°C]. And when the environment where the image forming apparatus is set is 30 [°C] and plain paper 2 (105 g / m² or less) is being fed, it is set so that the back surface thermistor 45b1 of the central fixing belt reaches 170 [°C].

[0038] In this embodiment, in order to reduce the sliding resistance between the inner surface of the fixing belt and the heater, grease is applied to the sliding surface of the heater 43. As the grease, 1.0 [g] of MOLYKOTE HP-300 manufactured by Toray Dow Corning is applied to the heater surface.

[0039] <Prediction of the life of the fixing device from the viewpoint of surface layer wear of the fixing belt> The surface wear of the fixing belt 41 varies in wear amount due to the temperature difference between the paper-passing part and the non-paper-passing part in the longitudinal direction when the recording material passes through the nip part N. Also, the wear amount varies depending on the length of the paper being passed (paper-passing distance), the thickness of the paper being passed (basis weight), and the magnitude of the pressure at the longitudinal paper edge (peak pressure in the recording material conveyance direction).

[0040] The reason why the surface wear amount of the fixing belt varies due to the temperature difference between the central part and the end part in the longitudinal direction is as follows. In the non-paper-passing part in the longitudinal direction, heat is not taken away by the recording material, and that part is partially heat-stored. Therefore, the temperature rises due to the temperature increase in the non-paper-passing part, and the fixing belt 41 and the pressure roller 44 expand, and their diameters become larger. As a result, the fixing belt 41 moves relatively faster with respect to the recording material (paper) P being passed, and a speed difference occurs between the fixing belt 41 and the recording material (paper) P. And the surface wear based on this speed difference increases as the temperature difference becomes larger.

[0041] Conversely, if the temperature at the end part in the longitudinal direction is lower than that at the central part, the fixing belt 41 moves relatively slower with respect to the recording material (paper) P being passed, and a speed difference occurs between the fixing belt and the recording material (paper) P. The surface wear based on this speed difference increases as the temperature difference becomes larger.

[0042] The reason why the surface wear amount of the fixing belt varies is that when a speed difference occurs between the fixing belt and the recording material, the wear amount increases as the pressure applied to the surface of the fixing belt at the paper edge becomes larger. Especially when using a recording material (paper) with a thick paper thickness or when the pressure at the paper edge position is large, the wear degree of the fixing belt becomes large even if the same number of prints are performed.

[0043] Here, that the recording material has passed through the nip part N can be detected as follows. That is, as passing detection means, a pre-fixing sensor 2 that detects the entry of the recording material shown in FIG. 1 and a post-fixing sensor 61 that detects the discharge of the recording material from the nip part N are used. Also, it may be possible to count the paper passing by predicting that the recording material will pass through the nip part N several seconds after transporting the recording material from the registration roller pair 23 shown in FIG. 1.

[0044] Then, the control unit 100 functions as an acquisition unit including a first acquisition unit and a second acquisition unit that acquire the detected temperature of the first temperature detection unit 45b1 and the detected temperature of the second temperature detection unit 45b2 or 45b3 when the recording material passes through the nip portion N. This acquisition unit includes a counting unit that counts based on the detected temperature of the first temperature detection unit and the detected temperature of the second temperature detection unit when a recording material of a predetermined width passes through the nip portion each time the recording material of the predetermined width passes through the nip portion N. When counting, counting is performed on the drive (D) side and the anti-drive (AD) side, respectively. Then, when the counting unit counts a predetermined value, it notifies that the fixing belt is to be replaced based on the acquisition unit (details will be described later).

[0045] <Method for obtaining pressure application information of fixing device> The storage unit 110 stores the pressure application information of the fixing device 40 at the time of manufacturing the fixing device. The storage unit 110 also stores the pressure application information of a plurality of regions in the longitudinal direction.

[0046] As the method, measurement is performed by a surface pressure measurement distribution system I-SCAN (manufactured by Nitta Corporation). Fig. 5 shows the longitudinal pressure application distribution (peak pressure) of the fixing device.

[0047] In this embodiment, as an example, since the predicted value of the fixing device life at A4 size is used, the pressure application (the maximum value of the peak pressure in the recording material conveyance direction) at both ends of the A4 size in the longitudinal direction of the fixing belt is used.

[0048] The measured pressure application at both ends is compared with the pressure application measured in advance in the center product of the part variation tolerance, and the differential pressure application ΔP is calculated respectively. The differential information is input to and stored in the storage unit 110. The storage unit 110 is provided in the main body of the image forming apparatus in this example, but may be provided in the fixing device. In the part variation in this example, a pressure application difference of ΔP of up to ±0.1 MPa occurs.

[0049] 1) Fixing Belt Paper Passing Distance, First, Second, and Third Weighting Coefficients In view of such a situation, in this embodiment, for each temperature difference zone between the central portion and the end portion in the longitudinal direction, the paper passing distance of the fixing belt is acquired, and a temperature coefficient (first weighting coefficient) is set for each temperature difference zone between the central portion and the end portion. Further, a basis weight coefficient (second weighting coefficient) is set for each type of paper (basis weight of the paper) as the recording material (paper). Further, coefficients (third weighting coefficients) are set for the driving side and the non-driving side respectively based on the pressing force information of the fixing device.

[0050] Then, when the sum of the product of the paper passing distance of the fixing belt and the temperature coefficient, the basis weight coefficient, and the pressing force coefficient exceeds a certain predetermined value, it is determined as the life of the fixing device, and a notification prompting replacement is given.

[0051] Table 1 shows the paper passing distance and the temperature difference coefficient (first weighting coefficient) in the temperature difference zone classification (for each temperature difference range) between the central portion and one end portion in the longitudinal direction of this embodiment. Also shown in Table 1 are the paper passing distance and the temperature difference coefficient (first weighting coefficient) in the temperature classification between the central portion and the other end portion in the longitudinal direction. Further, the basis weight coefficient (second weighting coefficient) is shown in Table 2. In Table 2, while the basis weight coefficient (second weighting coefficient) is represented as c1, c2, c3, the 1.0, 2.0, 3.0 shown on the right side thereof are representative values. It is used when fixed values (representative values) are used instead of the changing values c1, c2, c3.

[0052] Furthermore, the pressing force coefficient is shown in Table 3. In Table 3, coefficients are provided according to the differential pressing force ΔP. The 1.12, 1.06, 1.00, 0.94, 0.88 shown on the right side of the coefficients d1, d2, d3, d4, d5, d6 are representative values. It is used when fixed values (representative values) are used instead of the changing values d1, d2, d3, d4, d5, d6.

[0053]

Table 1

[0054]

Table 2

[0055]

Table 3

[0056] As shown on the left side of Table 1, the temperature divisions between the center of the back side of the fixing belt and the end on the drive side (D side) of the back side of the fixing belt are represented as a matrix of three temperature divisions of 170 [°C] or less, higher than 170 [°C] and less than 190 [°C], and 190 [°C] or more, respectively. And in the matrix of nine temperature divisions between the center and one end (the end on the drive side) on the left side of Table 1, the fixing belt paper passage distance (L13 etc.) and the temperature coefficient (the first weighting coefficient) (b13 etc.) obtained appear.

[0057] Similarly, on the right side of Table 1, the temperature divisions between the center of the back side of the fixing belt and the end on the anti-drive side (AD side) of the back side of the fixing belt are represented as a matrix of three temperature divisions of 170 [°C] or less, higher than 170 [°C] and less than 190 [°C], and 190 [°C] or more, respectively. And in the matrix of nine temperature divisions between the center and the other end (the end on the anti-drive side) on the right side of Table 1, the fixing belt paper passage distance (L23 etc.) and the temperature coefficient (the first weighting coefficient) (b23 etc.) obtained appear.

[0058] It is not necessary to stick to nine for the above-mentioned temperature divisions, and the temperature divisions may be increased or decreased. By increasing the temperature divisions, the accuracy of the life improves. However, since the calculation area of this image forming apparatus increases, measures such as increasing the memory of the image forming apparatus are required.

[0059] Furthermore, the temperature ranges of the drive-side thermistor and the anti-drive-side thermistor may be changed respectively. For example, when the attachment positions of the drive-side thermistor and the anti-drive-side thermistor are not symmetric left and right, or when the paper passing position is not in the center, the coefficients may be changed. Also, although the temperature range is determined by the temperature on the back of the fixing belt, it may be divided according to the temperature on the back of the heater.

[0060] 2) Obtaining (measuring) the paper passing distance of the fixing belt The obtaining (measuring) of the paper passing distance of the fixing belt is measured based on the size (conveying direction) of the recording material (paper) of the image formation request sent from the control unit. More specifically, it is obtained as the sum of the values obtained by multiplying the size in the conveying direction of the recording material (paper) by the number of conveyed sheets and adding them for different sizes (conveying direction) of the recording material.

[0061] 3) Temperature measurement timing and temperature coefficient (first weighting coefficient) The temperature measurement timing for each thermistor is set when the rear end position of the recording material (paper) passing through comes to the center in the recording material conveying direction of the nip portion N. Then, the values of each paper passing distance are stored corresponding to the temperature ranges to which the measured temperatures of the respective thermistors belong. For example, when running a job of A4 size, if the center temperature is 170 [°C] and the D-side end temperature is 180 [°C] when the rear end position of the A4 size paper comes to the center of the nip portion N, the paper length of A4 size: 210 [mm] is stored at the position of L12 in Table 1. Note that the units of L11 to L19 and L21 to L29 are [mm].

[0062] Here, each temperature coefficient (the first weighting coefficient) is determined with the fixing belt passing distance at which surface wear of the fixing belt occurs in an image when passing paper durability is achieved in a certain mode as the reference (weighting coefficient is 1). In this embodiment, it is based on the case when the center thermistor on the back of the fixing belt, the D-side thermistor on the back of the fixing belt, and the AD-side thermistor on the back of the fixing belt are at 170°C, the paper being passed is plain paper with a basis weight of 105 [g / m^2], and passing paper durability is achieved. The method for checking whether surface wear of the fixing belt has occurred in the image is to form a blue solid on coated paper (OKTOP 128 [g / m^2]) for each predetermined number of sheets. Then, if a fixing defect image occurs at the edge portion of the paper after passing paper durability, it is determined as NG (judged that wear has occurred).

[0063] Assume that when passing paper durability is achieved in each temperature zone, the fixing belt passing distance at which surface wear of the fixing belt occurs is as follows. Center-edge thermistor temperature difference: 0 [°C], durability... La [mm] Center-edge thermistor temperature difference: 10 [°C], durability... Lb [mm] (※ the edge is higher) Center-edge thermistor temperature difference: 20 [°C], durability... Lc [mm] (※ the edge is higher) Here, since the temperature coefficient (the first weighting coefficient) is based on the fixing belt passing distance when the difference between the center and edge thermistors is 0, the coefficient when durability is achieved at a temperature difference of 10 [°C] is obtained (calculated) as La / Lb (if La > Lb, the coefficient will be greater than 1). Also, the coefficient when durability is achieved at a temperature difference of 20 [°C] is obtained (calculated) as La / Lc.

[0064] Note that this time, the temperature coefficient (the first weighting coefficient) is determined by the absolute value of the temperature difference, but the temperature coefficient (the first weighting coefficient) may be changed depending on the fixing device configuration.

[0065] In this embodiment, regarding the durability for each temperature, the temperature at the center and the ends on the back of the fixing belt was changed, and durability was performed by passing GF-C104 A4 size (manufactured by Canon). The determination of the occurrence of surface wear of the fixing belt is as described above. The fixing belt passing distances at which surface wear of the fixing belt occurred were La = 2.2E+7 [mm], Lb = 2.0E+7 [mm], and Lc = 1.8E+7 [mm].

[0066] The coefficients b11, b15, and b19 of the center-D side thermistor were set to 1.0, the coefficients b12, b14, b16, and b18 were set to 1.1, and the coefficients b13 and b17 were set to 1.2.

[0067] Regarding the temperature coefficient (first weighting coefficient) on the center-AD side, it was set to the same value as the temperature coefficient (first weighting coefficient) on the center-D side. Note that if the temperature difference during paper passing is different for the center-D side and the center-AD side, the temperature coefficients (first weighting coefficients) may be changed respectively. For example, when the mounting positions of the D-side thermistor and the AD-side thermistor are not symmetric, or when the paper passing position of the recording material (paper) is not at the center, the temperature coefficient (first weighting coefficient) may be changed.

[0068] 4) Basis weight coefficient (second weighting coefficient) The basis weight coefficient (second weighting coefficient) is based on the fixing belt passing distance when the basis weight is 105 [g / m²] (weighting coefficient is 1). When the basis weight of the recording material (paper) was changed and durability was performed by passing paper, the passing distances at which surface wear of the fixing belt occurred were as follows. At that time, durability was performed so that the center thermistor temperature and the end thermistor temperature were 170°C.

[0069] For basis weight of 105 [g / m²] or less: Ld [mm]: (Durability with GF-C104 A4 (manufactured by Canon)) For basis weight of 210 [g / m²] or less: Le [mm]: (Durability with GF-C209 A4 (manufactured by Canon)) For basis weight of 300 [g / m²] or less: Lf [mm]: (Durability with Color Copy A4 Mondi 300 A4 (manufactured by Mondi)) The fixing belt passing distance at which surface wear of the fixing belt occurred was Ld = 2.2E+7 [mm], Le = 1.1E+7 [mm], and Lf = 7.2E+6 [mm].

[0070] Since the basis weight coefficient (the second weighting coefficient) is based on the fixing belt passing distance when the basis weight is 105 [g / m²], the basis weight coefficient when durable at a basis weight of 210 [g / m²] or less is obtained (calculated) as Ld / Le (if Ld > Le, the coefficient is greater than 1). Similarly, the basis weight coefficient when durable at a basis weight of 300 [g / m²] or less is obtained (calculated) as Ld / Lf.

[0071] There is no need to strictly adhere to three basis weight classifications. The number of classifications can be increased or decreased. Increasing the number of classifications improves the accuracy of the lifespan. However, since the calculation area of this image forming apparatus increases, measures such as increasing the memory of the image forming apparatus are required.

[0072] 5) Pressure coefficient (the third weighting coefficient) The pressure coefficient (the third weighting coefficient) is based on a pressure of 0.2 MPa at the end of the fixing device for the central part of the component variation tolerance (weighting coefficient is 1). By changing the pressure on the D side (ΔP) (the AD side is fixed at 0), the passing distance at which image defects occur due to surface wear of the fixing belt during passing durability was as follows. At that time, the durability was carried out so that the central thermistor temperature and the end thermistor temperature were 170°C. ΔP = 0: Lg [mm]: (Durability with GF-C104 A4 (manufactured by Canon)) ΔP = +0.05: Lh [mm]: (Durability with GF-C104 A4 (manufactured by Canon)) ΔP = +0.1: Li [mm]: (Durability with GF-C104 A4 (manufactured by Canon)) The fixing film passing distance at which image defects occur due to surface wear on the D side of the fixing belt was Lg = 2.2E+7 [mm], Lh = 2.0E+7 [mm], and Li = 1.83E+7 [mm].

[0073] The pressure coefficient (the third weighting coefficient) is based on the pressure at the end of the fixing device when the component variation (ΔP) is centered. Therefore, the coefficient when enduring with ΔP = +0.1 is obtained (calculated) as Lg / Li (if Lg > Li, the coefficient will be greater than 1). Similarly, the basis weight coefficient when enduring with ΔP = +0.05 is obtained (calculated) as Lg / Lh.

[0074] There is no need to stick to five categories for the pressure coefficient classification. Whether increasing or decreasing the classification, the accuracy of the lifespan will be improved by increasing the classification. However, since the calculation area of this image forming apparatus will increase, corresponding measures such as increasing the memory of the image forming apparatus are required.

[0075] (LIFE1 of the fixing device from the perspective of the surface wear of the fixing belt) In this embodiment, LIFE1 of the fixing device from the perspective of the surface wear of the fixing belt is defined by Equation 1 shown below.

[0076]

Equation

[0077] Thus, in the present embodiment, the passing distance of the recording material passing through the nip portion is acquired as the first information. Further, in the present embodiment, the temperature of the first fixing member heated by the heat source or the temperature of the central portion and the end portion in the longitudinal direction of the heat source, and the recording material information regarding the basis weight or type of the recording material are acquired as the second information, and the pressing force information is acquired as the third information. Furthermore, a value obtained by multiplying the first information by the weighting coefficient corresponding to the second information and the third information is acquired as the fourth information, and the device life is predicted.

[0078] When the above LIFE1 value reaches 100 [%], it is possible to notify by the notification means that the fixing belt, which is the first rotating body, needs to be replaced. The control unit 100 functions as the notification means and notifies a signal to the operation unit 101 of the image forming apparatus main body. The operation unit 101 is a touch panel, and its display functions as a notification unit (display unit). In this way, the life prediction of the fixing device is performed.

[0079] Note that a determination means capable of determining whether or not to perform notification to the operation unit 101 may be provided. Further, not only the operation unit 101 but also the life notification of the fixing device may be performed on the screen of the user's printer driver (not shown).

[0080] (Block Circuit and Control Flow) The block circuit of the present embodiment is shown in FIG. 6. It shows the control system of the image forming apparatus including the fixing device 40 of the present embodiment. The overall control of the image forming apparatus is performed by the control unit 100, to which an operation unit 101 composed of a liquid crystal touch panel, buttons, etc. is connected. The image forming apparatus starts operating by input of various conditions of the user from the operation unit 101.

[0081] Information such as the size and basis weight of the recording material (paper) to be passed is transmitted from the paper information acquisition means 102 to the control unit 100. Also, the pressure information stored in the storage means 110 is transmitted to the control unit 100. The temperature and drive (rotation) information of the central part and the end part in the longitudinal direction of the fixing device 40 are transmitted from the central thermistor information acquisition means 103, the D-side thermistor information acquisition means 104, the AD-side thermistor information acquisition means 105, and the motor information acquisition means 106 to the control unit 100. Then, the paper feed distance acquisition means 100a inside the control unit 100 acquires the paper feed distance. Further, the control unit 100 acquires the first, second, and third weighting coefficients, multiplies these by the paper feed distance, and predicts the life (device life) LIFE1 of the fixing device.

[0082] The control flow of the present embodiment is shown in FIG. 7. First, the control unit 100 receives a JOB (job) of the image forming apparatus, and acquires the paper size (conveying direction), paper basis weight, and pressure information of the recording material (paper) to be passed. Then, the fixing motor is driven, power is supplied to the heater, and the temperatures of the center of the back surface of the fixing belt and the end thermistors are measured. And the value of the paper feed distance is stored at the location according to the temperature classification of the center and end thermistors. The paper feed distance for each temperature zone is integrated, and the LIFE1 value is calculated by multiplying (multiplying) by the temperature coefficient, basis weight coefficient, and pressure coefficient. As a result, if the LIFE1 value is 100 [%] or more, a life warning of the fixing device is displayed.

[0083] When it is determined by a paper feed count as in the prior art whether an image defect occurs due to surface wear of the fixing belt, the occurrence count varies depending on the usage situation of the customer, such as 60K sheets or 100K sheets. However, by applying the present embodiment, when the LIFE1 value is 100 [%], an image defect due to surface wear of the fixing belt occurs in the image, and it becomes easier to set a replacement standard. For example, if there is a customer whose LIFE1 progresses by 10 [%] every month, when the current LIFE1 value is 80 [%], the fixing device should be replaced after two months, and it also becomes easier to make a service call plan.

[0084] Furthermore, when the current LIFE1 value is 80 [%], by displaying the remaining life as 20 [%], the user can check the replacement guideline. An example of the display is shown in FIG. 8. On the operation unit of the image forming apparatus and on the printer driver screen (not shown) used by the user, the current LIFE value and the remaining LIFE value of the consumable part (of the fixing device), and the estimated replacement date (guideline date) are output (displayed). According to such an embodiment, the life of the fixing device can be accurately detected, and the user can be prompted to replace the fixing device at an appropriate timing (by warning means).

[0085] In this embodiment, when there is a difference in the life of the fixing device depending on the paper feeding mode and the paper feeding state, the paper feeding distance is weighted according to the temperature zones of the central part and the end part, and the paper feeding distance is integrated considering the basis weight of the paper to be fed and the pressing force of the fixing device. Thereby, regardless of the paper feeding mode and the variation of the parts, the life of the fixing device can be accurately predicted, and the user can be prompted to replace the fixing device at an appropriate time.

[0086] <Second Embodiment> The configuration according to the second embodiment of the present invention is substantially the same as that of the first embodiment. In this embodiment, the life is predicted using the surface layer film thickness of the initial fixing belt as well.

[0087] Regarding the life prediction due to the surface layer wear of the fixing belt 41, as in the first embodiment, when the count value of the life reaches a predetermined value, it is notified that the fixing device needs to be replaced.

[0088] The predetermined value, which is the threshold for determining the life of the fixing device, varies depending on the surface layer film thickness of the initial fixing belt. The surface layer film thickness of the fixing belt has manufacturing variations. When the film thickness of the initial fixing belt is thinner than the nominal value, the surface layer of the fixing belt reaches the end of its life earlier, so the threshold for determining the life of the fixing belt needs to be reduced. Conversely, when the film thickness of the initial fixing belt is thicker than the nominal value, the life of the surface layer of the fixing belt is extended, so the threshold for determining the life of the fixing belt needs to be increased.

[0089] <Method for Obtaining the Surface Layer Film Thickness of the Fixing Belt> For the initial surface film thickness of the fixing belt 41, the measured value previously measured in the state of the fixing belt is used.

[0090] The measured surface film thickness of the fixing belt 41 is compared with the central value of the surface film thickness, and the differential film thickness Δt is calculated. The differential information is input to and stored in the storage means 110. In the variation of parts in this example, a film thickness difference of Δt up to ±5 μm occurs.

[0091] 6) Film thickness correction value The film thickness correction value is based on the central product of the variation tolerance of the film thickness of the fixing belt. When various characteristics passed the paper durability of GF-C104 A4 size (manufactured by Canon Inc.) under central conditions, the paper passing distance a per 1 μm of surface wear of the fixing belt was 5.5E+5 [mm]. From this result, in this embodiment, a film thickness correction classification was created according to the initial differential film thickness Δt.

[0092]

Table 4

[0093] There is no need to stick to five for the film thickness correction classification, and the classification may be increased or decreased. By increasing the classification, the accuracy of the life is improved.

[0094] Using the corresponding film thickness correction value A from each film thickness correction classification, the value of the normalization constant B, which is the threshold for determining the life when the surface film thickness of the fixing belt is the nominal value, is corrected. First, the film thickness correction value A is determined according to the differential film thickness Δt stored in the memory when the fixing device is initial and mounted on the main body, and added to the normalization constant B to calculate the life reference value C. The calculated life reference value C is used to predict the life LIFE.

[0095] In this embodiment, the life LIFE1 of the fixing device from the viewpoint of the surface wear of the fixing belt is defined by Equation 2 shown below, but it is the same as the first embodiment except that the life reference value C is changed.

[0096]

Equation

[0097] Thus, in this embodiment, the passing paper distance serving as the lifetime threshold is corrected according to the film thickness information of the initial fixing belt. For those with a thinner initial film thickness, the lifetime reference value becomes smaller due to the film thickness correction value, so the lifetime threshold is small. For those with a thicker initial film thickness, the lifetime reference value becomes larger due to the film thickness correction value, so the lifetime threshold becomes larger. Also, the passing distance of the recording material passing through the nip portion is acquired as the first information. In this embodiment, the temperature of the first fixing member heated by the heat source or the temperature between the central portion and the end portion in the longitudinal direction of the heat source, and the recording material information regarding the basis weight or type of the recording material are acquired as the second information, and the pressing force information is acquired as the third information. Further, the sum of the values obtained by multiplying the first information by the weighting coefficients corresponding to the second information and the third information is acquired as the fourth information, and the device lifetime is predicted.

[0098] When the above LIFE1 value reaches 100 [%], it is possible to notify by the notification means that the fixing belt, which is the first rotating body, needs to be replaced. The control unit 100 functions as the notification means and notifies a signal to the operation unit 101 of the image forming apparatus main body. The operation unit 101 is a touch panel, and its display functions as a notification unit (display unit). In this way, the lifetime prediction of the fixing device is performed.

[0099] In this embodiment, when there is a difference in the lifetime of the fixing device depending on the paper passing mode and the paper passing state, the passing paper distance serving as the lifetime threshold is corrected according to the film thickness of the initial fixing belt, and the weighted passing paper distance considering the weighting according to the temperature zones of the central portion and the end portion and the basis weight of the paper to be passed and the pressing force of the fixing device is integrated. Thereby, regardless of the paper passing mode or the variation of parts, the lifetime of the fixing device can be accurately predicted and the user can be urged to replace the fixing device at an appropriate time.

[0100] (Other modifications) As described above, the preferred embodiments of the present invention have been described. However, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist thereof.

[0101] (Modification Example 1) In the above-described embodiment, the value at the end of the A4 size is used as the pressure information of the fixing device, but values measured at locations other than the A4 size may also be used. (As an example, it may be measured for each paper size and the pressure coefficient may be determined for each paper size.)

[0102] (Modification Example 2) In the above-described embodiment, the pressure distribution of the initial fixing device was measured. However, not limited to the initial stage, the pressure distribution may also be measured in the used state, and then the coefficient may be changed and used.

[0103] (Modification Example 3) In the above-described embodiment, the temperature at the center and the end in the longitudinal direction of the first fixing member when the recording material passes through the nip portion, the recording material information regarding the basis weight or type of the recording material, and the longitudinal pressure distribution information were obtained. However, it may be configured to obtain any one of them.

[0104] (Modification Example 4) In the above-described embodiment, the passing distance of the recording material passing through the nip portion was obtained. However, it may also be configured to obtain the passing time of the recording material passing through the nip portion. In this case, for example, a light projecting means (light source) and a light receiving means (sensor) may be provided with the recording material interposed therebetween, and by utilizing the fact that the light receiving output decreases when the recording material is present, a configuration may be adopted in which a timer obtains the added value of the time during which the light receiving output decreases. Note that the value obtained by multiplying the passing time thus obtained by the process speed can also be handled as the passing distance.

[0105] (Modification Example 5) In the above-described embodiment, the basis weight coefficient (second weighting coefficient) was set for each basis weight of different recording materials (papers). However, when different types of recording materials (papers) with the same basis weight are considered, the coefficient (second weighting coefficient) may be set for each different type of recording material (paper).

[0106] (Modification Example 6) In the above-described embodiment, an endless belt is provided on the first rotating body with respect to the first and second rotating bodies that form the nip portion in the fixing device. However, the present invention is not limited to this. A roller pair system may be used, or the endless belt may be provided on both the first rotating body and the second rotating body. Also, among the second rotating bodies that form the nip portion together with the first rotating body in the fixing device, the case where the first rotating body is pressed as a pressure roller is shown. However, the present invention is not limited to this, and it can be similarly applied to the case where the second rotating body as an opposing body is pressed by the first rotating body instead of as a pressing body.

[0107] (Modification Example 7) In the above-described embodiment, the surface wear life of the fixing belt is described as an example. However, the present invention is not limited to this, and it can be similarly applied to the surface wear life of the pressure roller.

Explanation of Reference Numerals

[0108] 10 Image forming unit 11 Photosensitive drum 12 Charger 13 Laser scanner 14 Developing device 15 Cleaner 17 Primary transfer blade 20 Paper feed cassette 23 Registration roller pair 25 Multi-feed tray 31 Intermediate transfer belt 35 Secondary transfer roller 40 Fixing device 41 Fixing belt 41a Fixing belt surface layer 41b Fixing belt base layer 41c Fixing belt elastic layer 41d Fixing belt inner surface layer 43 Heating body 44 Pressure roller 45a Heater back contact type thermistor 45b Belt back contact type thermistor 46 Heater holder 100 Control unit 101 Operation unit 110 Memory means P Recording material (paper) T Toner image N Fixing nip

Claims

1. An image forming apparatus having a fixing device for fixing a toner image on a recording material, wherein the fixing device includes: a heating rotating body for heating the recording material; and a pressure-applying rotating body that forms a nip portion by contacting the heating rotating body and applies pressure to the recording material, wherein storage means stores information regarding the pressure applied to a plurality of regions of the nip portion in the longitudinal direction of the heating rotating body; and determination means determines the life of the fixing device based on the information stored by the storage means. The image forming apparatus is characterized by comprising the above.

2. The storage means stores information on the width of the recording material in the longitudinal direction, and the determination means determines the life based on the width information. The image forming apparatus according to claim 1, characterized by the above.

3. The storage means stores the length of the recording material in the conveyance direction of the recording material, and the determination means determines the life based on the length. The image forming apparatus according to claim 2, characterized by the above.

4. The heating rotating body is a cylindrical belt. The image forming apparatus according to claim 1, characterized by the above.

5. The fixing device includes a heater disposed on the inner peripheral surface of the belt. The image forming apparatus according to claim 4, characterized by the above.

Images