Image forming device

Abstract

To prevent problems from becoming obvious early which are caused by repetition of contact and separation operations in a fixing unit.SOLUTION: When a parameter related to the cumulative usage of a fixing unit is a first value, the frequency to release or reduce applied pressure is a first frequency, and when the parameter related to the cumulative usage is a second value larger than the first value, the frequency to release or reduce the applied pressure is a second frequency lower than the first frequency.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus such as a copying machine or a printer. [Background technology]

[0002] An image forming apparatus that uses an electrophotographic method, an electrostatic recording method, or the like has a transfer device that transfers a toner image onto a recording material, and a fixing unit that fixes the toner image onto the recording material by applying heat and pressure to the toner image on the recording material.

[0003] In the above image forming apparatus, some kind of error may cause the conveyance of the recording material to be delayed in the fixing unit, resulting in a so-called jam. Patent Document 1 discloses a technology that automatically releases the pressure of the fixing unit when a jam is detected by providing a recording material detection unit that detects the retention of the recording material in the fixing unit and a pressure release mechanism that releases the pressure of the fixing unit. This technology makes it easier to remove the recording material from the fixing unit when a jam occurs in the fixing unit.

[0004] Furthermore, Patent Document 2 discloses a technology in which an image forming apparatus goes into a sleep mode when the power supply to the image forming apparatus is turned off or when the image forming apparatus has not been used for a while, and the pressure applied to the fixing unit is automatically released. This technology makes it possible to suppress deterioration, such as deformation of the fixing member, caused by the pressure being maintained for a long period of time in the fixing unit.

[0005] As a pressure adjusting mechanism for applying pressure and releasing or reducing the pressure, a configuration in which the expansion and contraction state of a compression coil spring or the like is adjusted by a cam member or the like is known. Also, as types of fixing units, a heat roller type using a fixing roller and a pressure roller containing a halogen heater, and a film heating type using a fixing film are known. In a fixing unit of the film heating type, a fixing nip is formed by sandwiching the fixing film between a heater and a heater holder arranged inside the fixing film and a pressure member arranged on the outer surface of the fixing film.

[0006] In a film heating type fixing unit, a heater is attached to a heater holder that is placed in the internal space of a cylindrical film. Between the heater holder and the heater, there are provided components such as a thermistor for detecting the heater temperature, a thermoswitch as a safety element, etc. (These components are hereinafter referred to as pressing members.) These pressing members apply pressure to the heater in a direction that pulls the heater away from the heater holder.

[0007] When the image forming apparatus detects a jam, when the power is turned off, or when the image forming apparatus transitions to a sleep mode, the pressure of the fixing unit is automatically released. At this time, if the heater is separated from the heater holder due to the pressure from the pressing member, the following phenomenon occurs. For example, the support state of the pressing member may change, causing thermistor temperature detection and safety element operation to become unstable, or the edge of the heater may hit the inner surface of the film, causing scratches on the inner surface of the film. Patent Document 3 discloses a configuration in which an adhesive is interposed at a predetermined location between the heater and the heater holder to support the heater, thereby suppressing the heater from being pulled away by the pressing member. As the adhesive, for example, a silicone rubber-based adhesive having elasticity is used to absorb the stress caused by the difference in thermal expansion coefficient between the heater and the heater holder and to withstand high temperatures of 200°C or higher. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 7-129018 [Patent Document 2] JP 2008-191372 A [Patent Document 3] JP 2016-12077 A Summary of the Invention [Problem to be solved by the invention]

[0009] In the above-mentioned fixing units using a heat roller or a film heating method, when the pressure adjustment mechanism repeatedly applies and releases pressure (hereinafter referred to as contact and separation), the following phenomenon occurs: Specifically, the compression coil spring used in the pressure adjustment mechanism plastically deforms due to repeated expansion and contraction, and is no longer able to apply the intended pressure.

[0010] In addition, in the above-mentioned fixing unit using the film heating method, when the heater and the heater holder are repeatedly brought into contact and separated with an adhesive therebetween, the following phenomenon occurs: Specifically, when stress is applied in the thickness direction of the adhesive, which is the direction in which the heater and the heater holder are separated, the adhesive strength of the adhesive decreases and the adhesive becomes more likely to peel off.

[0011] Furthermore, when the terminal of the connector for supplying power to the heater acts as the pressing member described above, repeated contact and separation movements may cause slight displacement of the heater position, resulting in slight sliding between the pressing portion of the terminal and the heater electrode, which may cause wear of the member. Even when an adhesive is interposed between the heater and the heater holder as described above, repeated contact and separation movements may cause the adhesive itself to expand and contract in the thickness direction of the heater, which may also cause wear of the member.

[0012] The above problem is one that gradually worsens with repeated contact and separation operations. In general, the specifications of the members constituting the fixing unit are set to ensure a sufficient margin for the number of contact and separation operations expected within the lifespan of the member so that the above problem does not become apparent within the lifespan of the member while still providing satisfactory quality.

[0013] However, the number of times the fixing unit performs contact and separation operations depends on the usage conditions of the user, so it is necessary to suppress problems caused by the repeated contact and separation operations of the fixing unit regardless of the usage conditions of the user. [Means for solving the problem]

[0014] In order to solve the above-mentioned problems, the present invention provides an image forming apparatus having an image forming section that forms an image on a recording material, a heating member, a pressure member that forms a nip portion with the heating member, a pressure adjustment mechanism that applies pressure to the nip portion and releases or reduces the pressure, and a fixing unit that heats the recording material passing through the nip portion to fix an image formed on the recording material to the recording material, the image forming apparatus comprising: an image forming unit that fixes an image formed on the recording material to the recording material, the image forming unit being configured to fix the ... a sheet number counting means for counting the number of sheets of recording material that have passed through the fixing unit, and the parameter relating to the cumulative usage amount is the number of sheets counted by the sheet number counting means. It is characterized in that: The present invention also provides a method for producing a method for manufacturing a semiconductor device comprising the steps of: The image forming device has an image forming unit that forms an image on a recording material, a heating member, a pressure member that forms a nip portion with the heating member, a pressure adjustment mechanism that applies pressure to the nip portion and releases or reduces the pressure, and a fixing unit that fixes the image formed on the recording material to the recording material by heating the recording material passing through the nip portion, characterized in that when a parameter related to accumulated usage of the fixing unit is a first value, the frequency at which the pressure is released or reduced is a first frequency, and when the parameter related to accumulated usage is a second value greater than the first value, the frequency at which the pressure is released or reduced is a second frequency less than the first frequency, and further has a drive time measurement means that measures the drive time of the fixing unit, and the parameter related to accumulated usage is the drive time measured by the drive time measurement means. Effect of the Invention

[0015] As described above, according to the present invention, it is possible to prevent early manifestation of problems caused by repeated contact and separation operations of the fixing unit, regardless of the usage conditions of the user. [Brief description of the drawings]

[0016] [Figure 1] Cross-sectional view of an image forming apparatus 100 [Diagram 2] Cross-sectional view of the fixing unit 200 [Diagram 3] FIG. 2 is a diagram for explaining the adhesive structure of the heater 210 and the heater holder 220 in the first embodiment. [Figure 4] Flowchart 1 for controlling release of pressure force of fixing unit 200 in embodiment 1 [Diagram 5] Flowchart 2 for controlling release of pressure force of fixing unit 200 in embodiment 1 [Figure 6] Flowchart 3 for controlling release of pressure force of fixing unit 200 in embodiment 1 [Figure 7] FIG. 13 is a diagram showing the cumulative number of times the pressure force of the fixing unit 200 is released in a model case using the control flow chart 3 of the first embodiment. [Figure 8]11 is a flow chart showing a control flow of releasing the pressure applied to the fixing unit 200 in the second embodiment. [Figure 9] FIG. 13 is a diagram showing the cumulative number of times the pressure force of the fixing unit 200 is released in two model cases using the control flow chart of the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, the embodiments of the present invention will be described with reference to the drawings. Note that the following embodiments do not limit the invention of the claims, and all of the combinations of features described in the embodiments are not necessarily essential to the solution of the present invention. EXAMPLES

[0018] 1. Configuration of image forming device FIG. 1 is a schematic diagram of an image forming apparatus 100 in this embodiment. The image forming apparatus 100 is a laser printer using electrophotographic recording technology. The photoconductor 19 is charged to a predetermined polarity by a charging roller 16. When the image forming apparatus 100 receives a print signal from an external device, the scanner unit 21 irradiates the photoconductor 19 with laser light corresponding to the received image information, exposing the photoconductor 19. As a result, an electrostatic latent image is formed on the photoconductor 19. The cartridge 15 includes a developing device 17. The developing device 17 supplies toner to the electrostatic latent image on the photoconductor 19, thereby forming a toner image on the photoconductor 19 corresponding to the image information. A paper feed cassette (paper feed section) 11 holds recording materials (recording paper) P. The recording materials P held in the paper feed cassette 11 are fed one by one by a pickup roller 12 and conveyed toward a registration roller 14 by a roller 13. The recording material P is conveyed from the registration roller 14 to the transfer position in accordance with the timing when the toner image on the photoreceptor 19 reaches the transfer position formed by the photoreceptor 19 and the transfer roller 20. When the recording material P passes the transfer position, the toner image on the photoreceptor 19 is transferred to the recording material P. After that, the recording material P is heated by the fixing unit 200, so that the toner image transferred to the recording material P is fixed to the recording material P. The recording material P with the fixed toner image is discharged to a tray at the top of the image forming apparatus 100 by rollers 26 and 27. Note that 18 is a cleaner that cleans the photoreceptor 19. In addition, a control circuit 40 connected to a commercial AC power source 41 supplies power to the fixing unit 200. The photoreceptor 19, the charging roller 16, the scanner unit 21, the developing device 17, and the transfer roller 20 described above constitute an image forming section that forms an unfixed image on the recording material P.

[0019] 2. Structure of the fixing unit FIG. 2 is a cross-sectional view of the fixing unit 200.

[0020] The heater 210 is a thin-walled heating element, and includes a plate-shaped base substrate made of ceramic such as alumina or metal such as SUS, and a resistance heating element provided on the substrate that generates heat when electricity is applied. The heater holder 220 is a heating element support made of heat-resistant resin such as liquid crystal polymer, and supports the heater 210 via an adhesive member described later. The pressure roller 290 is a pressure member that forms a fixing nip portion N as a pressure contact nip together with the heater 210 via the film 230. The pressure roller 290 has a core metal 291 made of iron, aluminum, or the like, and an elastic layer 292 made of silicone rubber, or the like, and rotates in the direction of the arrow by receiving power from a motor M1. The film 230 is made of a cylindrical flexible member, and is heated by the heat of the heater 210 in the fixing nip N formed by the heater 210 and the pressure roller 290. The film 230 may be based on a heat-resistant resin such as polyimide or a metal such as stainless steel, and an elastic layer such as heat-resistant rubber or a release layer made of heat-resistant resin may be provided on the base. The pressure adjustment mechanism 300 is a mechanism for applying and releasing the pressure for forming the fixing nip N.

[0021] On the surface of the heater 210 opposite to the surface facing the film 230, members such as a thermistor 250 and a safety element 260 shown in FIG. 3 are pressed and arranged in contact. The thermistor 250 is a temperature detection member for detecting the temperature of the heater 210 and feeding back the temperature control. In this embodiment, the thermistor 250 is a unit having a resistance element whose resistance value changes with temperature, a heat-resistant member such as ceramic paper that supports the resistance element, and a pressure-resistant member such as polyimide film that covers the resistance element and the heat-resistant member. The thermistor 250 is also arranged in contact with the heater 210 by the pressure of a thermistor pressure spring 250a held by a pressure member holder 270. The safety element 260 is a protection element such as a thermoswitch or a temperature fuse that operates in an abnormally high temperature state and cuts off the power supplied to the heater 210. The safety element 260 is arranged in contact with the heater 210 by the pressure of a safety element pressure spring 260a held by a pressure member holder 270.

[0022] The pressure stay 240 is a thick member made of a rigid material such as metal, and is disposed in contact with the surface of the heater holder 220 opposite the heater support surface.

[0023] The pressure adjustment mechanism 300 is made up of a fixing frame 201, a pressure spring 202, a pressure plate 203, and a pressure release cam 204. When applying pressure in the fixing nip N, the pressure adjustment mechanism 300 applies the pressure of the pressure spring 202 held by the fixing frame 201 to both longitudinal ends of the pressure stay 240 via the pressure plate 203. The pressure of the pressure spring 202 is transmitted to the pressure roller 290 side via the contact portion with the heater holder 220, thereby forming the fixing nip N.

[0024] A pressure release cam 204 is disposed in contact with the pressure plate 203. When the pressure is to be released in the fixing nip N, the pressure release cam 204 receives power from the motor M2 and rotates a predetermined amount in response to a command to release the pressure of the fixing unit 200. The pressure release cam 204 rotates a predetermined amount to lift the pressure plate 203, thereby releasing the pressure that forms the fixing nip N. The operation flow for releasing the pressure of the fixing unit 200 will be described in detail later. Note that releasing the pressure in this embodiment includes not only bringing the device into a non-pressurized state, but also reducing the pressure to a level that is acceptable for jamming processability and deformation of the parts of the fixing unit, with respect to the pressure required to heat and fix a toner image on the recording material P.

[0025] 3. Heater and heater holder bonding structure FIG. 3 is a diagram illustrating the adhesive structure of the heater 210 and the heater holder 220. As shown in FIG.

[0026] 3A is a plan view of the heater 210 as viewed from the fixing nip portion N side. The heater 210 has a resistance heating element 212, an electrode 213 for passing electricity through the resistance heating element 212, and a protective layer 214 for insulating and protecting the resistance heating element 212, on a substrate 211. In this embodiment, the surface on which the resistance heating element 212 is formed is the surface on the pressure roller side, and the opposite surface is the adhesive surface for the heater holder 220, but the surface on which the resistance heating element 212 is formed may also be the adhesive surface for the heater holder 220.

[0027] 3(b) is a plan view of the heater support surface of the heater holder 220 as viewed from the fixing nip portion N side, and FIG. 3(c) is a cross-sectional view along the line XX in FIG. 3(b) in a state in which the heater 210 and the heater holder 220 are bonded with an adhesive 280.

[0028] The heater support surface side of heater holder 220 has through holes at predetermined positions in the longitudinal direction, and thermistors 250, 251, 252 and safety element 260 are arranged so as to be pressed and abutted against heater 210 through the respective through holes. Adhesive points 281 are provided for each of the thermistors 250, 251, 252 and safety element 260 so as to sandwich them in the longitudinal direction of heater holder 220, and heater 210 and heater holder 220 are adhered with silicone rubber-based adhesive 280.

[0029] 4. Control to adjust pressure of fixing unit Next, a description will be given of control for adjusting the pressure of the fixing unit 200 in this embodiment. Note that the following control is executed by a CPU (not shown) provided in the image forming apparatus 100.

[0030] In this embodiment, the image forming apparatus 100 has a jam detection mechanism (not shown) as a transport failure detection means for detecting a transport failure of the recording material P. The jam detection mechanism (not shown) can detect that the recording material P is stuck in the fixing unit 200 when a jam is detected.

[0031] Furthermore, the image forming apparatus 100 has a power switch (not shown) as a power switching means for switching between starting up the apparatus and feeding paper. A user can start (on) or stop (off) the apparatus by switching the power switch.

[0032] Furthermore, the image forming apparatus 100 has a normal power mode in which the fixing unit 200 fixes a toner image on the recording material P, and a sleep mode which is a low power mode with low power consumption. In the normal power mode, the apparatus transitions to the sleep mode when it is not used for a predetermined time, and in the sleep mode, it returns to the normal power mode when it receives a print signal. In this embodiment, the normal power mode is also called the first state, and the low power mode and the sleep mode are also called the second state. The image forming apparatus 100 has a timer (not shown) that measures the elapsed time after the image formation or fixing operation is completed. Then, when the elapsed time after the image formation or fixing operation is completed reaches a predetermined time, the apparatus transitions to the sleep mode. The predetermined time may be set by the user as desired.

[0033] The image forming apparatus 100 performs an operation to release the pressure of the fixing unit 200 when any one of the following conditions (release conditions (predetermined conditions)) is satisfied. (1) When a signal to detect a jam of recording material P is received (2) When a signal to turn off the power of the image forming apparatus 100 is received (3) When the image forming apparatus 100 has not been used for a predetermined period of time and has received a signal to transition to a sleep mode. Then, the image forming apparatus 100 performs an operation of applying the pressure of the fixing unit 200 when any one of the following conditions (application conditions) is satisfied. (1) When the recording material P remaining in the fixing unit 200 is removed (2) When the image forming apparatus 100 is turned on (3) When the image forming apparatus 100 returns from the sleep mode

[0034] 5. Control to release pressure from the fixing unit Next, the control for releasing the pressure of the fixing unit 200 will be described.

[0035] The image forming apparatus 100 in this embodiment has a sheet counter (not shown) as a sheet counting means for measuring the "number Cp of recording materials P that have passed through the fixing unit 200 (sheet count Cp)" as a parameter related to the cumulative usage of the fixing unit 200. In addition, as the predetermined threshold value Cp1, for example, a threshold value corresponding to the number of sheets assumed to satisfy the quality of the fixing unit 200 is set.

[0036] In this embodiment, before the sheet count Cp reaches the threshold Cp1 while the image forming apparatus 100 is in operation, the following control is executed. That is, when any one of the release conditions (1) to (3) is satisfied, the pressure force of the fixing unit 200 is released. On the other hand, after the sheet count Cp reaches the threshold Cp1, even if any one of the release conditions (1) to (3) is satisfied, a case is set in which the pressure force is not released. Specifically, the control of the flowcharts shown in the following Figs. 4 to 6 is executed. Note that when the value of the sheet count Cp is a value before it reaches the threshold Cp1, the value is also referred to as a first value. Also, when the value of the sheet count Cp is a value after it reaches the threshold Cp1, the value is also referred to as a second value.

[0037] 6. Control after the number of sheets count Cp reaches the threshold Cp1 4 to 6 show control flowcharts 1 to 3 in this embodiment (flowchart 1).

[0038] 4 shows an example in which the pressure of the fixing unit 200 is not released when the release condition (3) among the three release conditions is satisfied after the sheet count Cp reaches the threshold Cp1. That is, after the sheet count Cp reaches the threshold Cp1, the pressure of the fixing unit 200 is not released even if the image forming apparatus 100 has not been used for a predetermined time and has received a signal to transition to a sleep mode.

[0039] When the image forming apparatus 100 receives a print signal (S402), the fixing unit 200 applies pressure (S403). A print sequence is executed in the image forming apparatus 100 (S404), and when the recording material P passes the fixing unit 200, a sheet counter (not shown) counts up the sheet count Cp (S405). When any of the release conditions (1) to (3) is satisfied (S406), it is determined whether the sheet count Cp reaches a threshold Cp1 (S407). When the sheet count Cp reaches the threshold Cp1, it is determined whether the release condition "(3) When the image forming apparatus 100 has not been used for a predetermined time and has received a signal to transition to a sleep mode" is satisfied (S408). That is, if the image forming apparatus 100 receives a sleep mode transition signal, the pressure is not released and the process proceeds to S410. If the release condition 3 is not satisfied, the pressure is released (S409). Thereafter, in S410, image forming apparatus 100 operates according to the condition that was satisfied in S406 out of cancellation conditions (1) to (3). For example, when cancellation condition 1 is satisfied, image forming apparatus 100 notifies the user that recording material P has jammed. When cancellation condition 2 is satisfied, image forming apparatus 100 turns off the power. When cancellation condition 3 is satisfied, image forming apparatus 100 transitions to a sleep mode.

[0040] By the control of the flowchart 1, the frequency of releasing the pressure force of the fixing unit 200 decreases after the sheet count Cp reaches the threshold value Cp1. For example, as a model case, the breakdown of the conditions for releasing the pressure force of the fixing unit 200 may be release condition (1): release condition (2): release condition (3) = 1: 39: 60. In this case, when the control of the flowchart 1 is executed, the frequency of releasing the pressure force of the fixing unit 200 decreases to about 40% after the threshold value Cp1 is reached, and the cumulative number of times the pressure force of the fixing unit 200 is released is less likely to increase. Therefore, it is possible to suppress problems caused by repeated contact and separation operations of the fixing unit 200. The frequency of releasing the pressure force of the fixing unit 200 before the sheet count Cp reaches the threshold value Cp1 is also referred to as the first frequency, and the frequency of releasing the pressure force of the fixing unit 200 after the sheet count Cp reaches the threshold value Cp1 is also referred to as the second frequency. As described above, according to this embodiment, the second frequency is less than the first frequency.

[0041] (Flowchart 2) 5 shows an example in which the pressure is released when the release conditions (1) and (3) are satisfied after the sheet count Cp reaches the threshold Cp1, but the pressure is not released when the release condition (2) is satisfied. In other words, after the sheet count Cp reaches the threshold Cp1, the pressure of the fixing unit 200 is not released even if a power-off signal of the image forming apparatus 100 is received.

[0042] S501 to S511 in the flowchart 2 in Fig. 5 correspond to S401 to S411 in the flowchart 1 in Fig. 4, and only S508 is different from Fig. 4. In S508, the image forming apparatus 100 determines whether the cancellation condition “(2) When a power-off signal for the image forming apparatus 100 is received” is satisfied.

[0043] By the control of this flowchart 2, the frequency with which the pressing force of the fixing unit 200 is released decreases after the sheet count Cp reaches the threshold value Cp1. For example, in the above-mentioned model case, when the flowchart 2 is executed, the frequency with which the pressing force is released decreases to about 60% after the sheet count Cp reaches the threshold value Cp1. Therefore, problems caused by the repeated contact and separation operations of the fixing unit 200 can be suppressed.

[0044] (Flowchart 3) The control flow chart 3 of FIG. 6 shows an example of a combination of the above two flow charts. For example, a first threshold Cp1 is set as a threshold corresponding to the number of sheets assumed to satisfy the quality of the fixing unit 200 over its lifespan, and a second threshold Cp2 is set as a value greater than the first threshold Cp1. Then, if the release condition (3) is satisfied after the sheet count Cp reaches the first threshold Cp1, the pressure is not released. Also, if the release condition (2) is satisfied after the sheet count Cp reaches the second threshold Cp2, the pressure is not released. The release condition (3) considered after the sheet count Cp reaches the first threshold Cp1 is also referred to as the first condition, and the release condition (2) considered after the sheet count Cp reaches the second threshold Cp2 is also referred to as the second condition.

[0045] Since S601 to S606 in the flowchart 3 in FIG. 6 correspond to S401 to S406 in the flowchart 1 in FIG. 4, the process from S607 onward will be described. When the image forming apparatus 100 satisfies any of the release conditions (1) to (3) (S606), it is determined whether the sheet count Cp has reached the first threshold Cp1 (S607). When the sheet count Cp has not reached the first threshold Cp1, it is determined whether the sheet count Cp has reached the second threshold Cp2 (S608). When the sheet count Cp has not reached the second threshold Cp2, it is determined whether the release condition (3) is met (S610). When the release condition (3) is not met, it is determined whether the pressurizing force is released (S611), and when the release condition (3) is met, it proceeds to S612 without releasing the pressurizing force. If the sheet count Cp reaches the second threshold Cp2 in S608, it is determined whether or not the release condition (2) is satisfied (S609). If the release condition (2) is not satisfied, the process proceeds to S610. If the release condition (2) is satisfied in S609, the process proceeds to S612 without performing the pressure release operation. The processes of S612 and S613 are the same as S410 and S411 in FIG. 4, and therefore will not be described.

[0046] By the control of this flowchart 3, the frequency of releasing the pressurizing force decreases after the sheet count Cp reaches the first threshold Cp1, and the frequency of releasing the pressurizing force further decreases after the sheet count Cp reaches the second threshold Cp2. For example, in the above-mentioned model case, when the flowchart 3 is executed, the frequency of releasing the pressurizing force decreases to about 40% after the sheet count Cp reaches the threshold Cp1, and the frequency decreases to about 1% after the sheet count Cp reaches the second threshold Cp2. Therefore, the cumulative number of times the pressurizing force is released is less likely to increase. As described above, it is possible to suppress problems caused by the repeated contact and separation operations of the fixing unit 200.

[0047] FIG. 7 shows the transition of the cumulative number of times the pressure is released (vertical axis) with respect to the sheet count Cp (horizontal axis) when the process of the flowchart 3 in FIG. 6 is executed in the above-mentioned model case.

[0048] As shown in FIG. 7, before the sheet count Cp reaches the first threshold Cp1, the pressure is released for all of the release conditions (1) to (3). Therefore, as the number of sheets of recording material P passing through the fixing unit 200 increases, the cumulative number of times the pressure is released per unit number of sheets, for example, per 1000 sheets, increases at a substantially constant rate. In contrast, after the sheet count Cp reaches the first threshold Cp1, the pressure is not released if the release condition (3) is satisfied, so the frequency of the release of the pressure decreases and the slope of the graph becomes smaller. Furthermore, after the sheet count Cp reaches the second threshold Cp2, the pressure is not released if at least one of the release conditions (2) and (3) is satisfied. In other words, after the sheet count Cp reaches the second threshold Cp2, the case in which the pressure is released is only the case of the release condition (1), so the frequency of the release of the pressure further decreases and the slope of the graph further becomes smaller.

[0049] By appropriately setting the threshold values ​​Cp1 and Cp2, within the period in which the quality of the fixing unit 200 is satisfactory, deterioration such as deformation of the fixing members can be suppressed by releasing the pressure force when the fixing unit 200 is not used for a long time, such as when the power is off or in sleep mode. If the period in which the quality of the fixing unit 200 is satisfactory is exceeded, the frequency of releasing the pressure force can be reduced to suppress a situation in which the pressure force decreases due to plastic deformation of the pressure spring 202 used in the pressure force adjustment mechanism 300. If the fixing unit is of a film heating type, the problem of a decrease in the adhesive force between the heater 210 and the heater holder 220 can be suppressed.

[0050] In this embodiment, the thermistor 250 and the safety element 260 are arranged as the pressing members on the rear surface of the heater (the surface opposite to the surface of the heater facing the fixing nip portion N). However, the same effect can be obtained by adopting the control of this embodiment in a configuration in which the terminal of the connector for supplying power to the heater electrode is arranged as the pressing member. By reducing the frequency of releasing the pressure force as in this embodiment, it is possible to suppress the problem that the position of the heater 210 is slightly displaced and the terminal of the power supply connector and the heater electrode slide slightly against each other, resulting in wear of the members.

[0051] Although the embodiment of the fixing unit 200 has been described using an example of a film heating type fixing unit, the present invention is not limited to this. The same effect as this embodiment can be obtained by performing the control as in this embodiment in various fixing units, including a heat roller type, that have a heating member, a pressure member that forms a pressure nip with the heating member, and a pressure adjustment mechanism.

[0052] In addition, although an example has been shown in which the sheet count Cp of the recording material P is used as a parameter relating to the cumulative usage amount of the fixing unit 200, the present invention is not limited to this. A driving time t such as a rotation time of a rotating body in the fixing unit 200 or a heating time by a heater may also be used as a parameter. In this case, a driving time measuring means for measuring the driving time t may be provided.

[0053] Furthermore, although the above description uses the example of when the power is turned off and when the mode is changed to a sleep mode as an example of reducing the frequency of releasing the pressure force, this is not limiting. The frequency of releasing the pressure force when a jam is detected may also be reduced. In addition, in an image forming apparatus that performs a pressure force release operation under a fourth or fifth release condition other than the release conditions (1) to (3), the frequency of releasing the pressure force associated with the fourth or fifth release condition may be reduced. EXAMPLES

[0054] In the first embodiment, an example was described in which the sheet count Cp of the recording material P and the driving time t of the fixing unit 200 were used as the parameter related to the cumulative usage of the fixing unit 200. In the present embodiment, an example will be described in which the cumulative number of times the pressure force is released is used as the parameter related to the cumulative usage of the fixing unit 200. Note that the configurations of the image forming apparatus 100 and the fixing unit 200 in this embodiment are the same as those in the first embodiment, and therefore description thereof will be omitted.

[0055] 7. Control to release pressure from the fixing unit A description will be given of the control for releasing the pressure of the fixing unit 200 in this embodiment. Note that the subsequent control is executed by the fixing unit 200 or a CPU (not shown) provided in the image forming apparatus 100 in which the fixing unit 200 is mounted.

[0056] The fixing unit 200 in this embodiment measures the "number of times the pressure force is actually released or reduced (pressure force release count)" when any one of the release conditions (1) to (3) described in the first embodiment is satisfied. The image forming apparatus 100 has a number counter (not shown) as a pressure force release count means. Also, similarly to the first embodiment, a first threshold value Ck1 and a second threshold value Ck2 that is greater than the first threshold value Ck1 are set.

[0057] In this embodiment, before the pressure release count Ck reaches the first threshold value Ck1 while the image forming apparatus 100 is in operation, the following control is executed. That is, when the release conditions (1) to (3) described in the first embodiment are satisfied, the pressure of the fixing unit 200 is released. On the other hand, after the pressure release count Ck reaches the first threshold value Ck1, the control shown in the flowchart in FIG. 8 is executed.

[0058] 8. Control after the pressure release count Ck reaches the first threshold Ck1 FIG. 8 shows a control flowchart 4 in this embodiment (flowchart 4).

[0059] The control flow chart 4 of FIG. 8 shows an example in which the pressure force is not released if the release condition (3) is satisfied after the pressure force release count Ck reaches the first threshold Ck1. That is, after the pressure force release count Ck reaches the first threshold Ck1, the pressure force is not released even if the image forming apparatus 100 receives a signal to transition to a sleep mode. Also, after the pressure force release count Ck reaches the second threshold Ck2, the pressure force is not released if the release condition (2) is satisfied. That is, after the pressure force release count Ck reaches the second threshold Ck2, the pressure force is not released even if the image forming apparatus 100 receives a power-off signal.

[0060] S801 to S805 in the flowchart 3 of FIG. 8 correspond approximately to S601 to S606 in the flowchart 1 of FIG. 6, so the process after S806 will be described. When the image forming apparatus 100 satisfies any one of the release conditions (1) to (3) (S805), it is determined whether the number count Ck has reached the first threshold value Ck1 (S806). When the number count Ck has not reached the first threshold value Ck1, a pressure force release operation is performed (S810), and the number count Ck is counted up (S811). When the number count Ck has reached the first threshold value Ck1, it is determined whether the number count Ck has reached the second threshold value Ck2 (S807). When the number count Ck has not reached the second threshold value Ck2, it is determined whether the release condition (3) is met (S809). If the release condition (3) is not satisfied, a pressure force releasing operation is performed (S810), and if the release condition (3) is satisfied, the process proceeds to S812 without performing the pressure force releasing operation. If the number count Ck has reached the second threshold value Ck2 in S807, it is determined whether the release condition (2) is satisfied (S808). If the release condition (2) is not satisfied, the process proceeds to S809. If the release condition (2) is satisfied in S808, the process proceeds to S812 without performing the pressure force releasing operation. The processes in S812 and S813 are the same as S410 and S411 in FIG. 4, and therefore will not be described.

[0061] By the control of this flow chart 4, the frequency of the pressing force being released decreases after the pressing force release count Ck reaches the first threshold value Ck1. Furthermore, the frequency of the pressing force being released further decreases after the pressing force release count Ck reaches the second threshold value Ck2. For example, in the case of the model case described in the first embodiment, when the flow chart 4 is executed, the frequency of the pressing force being released decreases to about 40% after the pressing force release count Ck reaches the first threshold value Ck1. Furthermore, the frequency decreases to about 1% after the pressing force release count Ck reaches the second threshold value Ck2. Therefore, the cumulative number of pressing force releases is less likely to increase. As described above, it is possible to suppress the problems caused by the repeated contact and separation operations of the fixing unit 200.

[0062] FIG. 9 is a graph comparing two model cases with different usage conditions of the fixing unit 200. That is, it shows the transition of the cumulative number of pressure release operations (vertical axis) against the number of sheets of recording material P that have passed through the fixing unit 200 (horizontal axis). Here, an example of usage conditions in each model case will be described. Model case 1 (solid line) is the model case described in Example 1, and is a case in which the breakdown of the pressure release conditions is release condition (1): release condition (2): release condition (3) = 1: 39: 60. In this case, the number of times the pressure is released per 1000 sheets of recording material P that have passed is 10. On the other hand, model case 2 (dashed line) is a case in which the breakdown of the pressure release conditions is release condition (1): release condition (2): release condition (3) = 1: 9: 90. In this case, the number of times the pressure is released per 1000 sheets of recording material P that have passed is 5 times.

[0063] 9, the slope of the graph (frequency of pressure release per unit number of sheets) is different between model case 1 and model case 2. Therefore, the number of sheets of recording material P that pass before the pressure release count Ck reaches the first threshold value Ck1 is different, and the slope after the pressure release count Ck reaches the first threshold value Ck1 is also different.

[0064] The problem caused by the repeated contact and separation operation of the fixing unit is largely dependent on the cumulative number of times the pressure force of the fixing unit is released. Therefore, as in this embodiment, by setting a threshold value for the cumulative number of times the pressure force is released and reducing the frequency of releasing the pressure force, it is possible to appropriately deal with the above problem. EXAMPLES

[0065] In the first and second embodiments, a parameter related to the cumulative usage of the fixing unit 200 is used to set a threshold value that satisfies the quality of the fixing unit 200, and the frequency of the contact / separation operation is reduced. In this embodiment, a parameter related to the cumulative usage of the fixing unit 200 is also used. This embodiment differs from the previous embodiment in that the time elapsed from a predetermined timing to the release of the pressure force of the fixing unit 200 is set in advance in stages. In this embodiment, the frequency of releasing the pressure force of the fixing unit 200 is reduced by lengthening the time elapsed from a predetermined timing to the release of the pressure force of the fixing unit 200 every time the value of the parameter related to the cumulative usage of the fixing unit 200 increases. Note that the configurations of the image forming apparatus 100 and the fixing unit 200 in this embodiment are the same as those in the first embodiment, and therefore will not be described.

[0066] 9. Control to release pressure from the fixing unit A description will be given of the control for releasing the pressure of the fixing unit 200 in this embodiment. Note that the subsequent control is executed by the fixing unit 200 or a CPU (not shown) provided in the image forming apparatus 100 in which the fixing unit 200 is mounted.

[0067] The image forming apparatus 100 of this embodiment measures the number of times the pressure force is released, Ck, described in the second embodiment. A plurality of threshold values ​​Ckj (j=1 to n) are set, and the threshold value Ckj is set to a larger value as j is larger. For example, the threshold value Ck1 is set to an upper limit value of the number of times the pressure force is released, assuming a lifespan that satisfies the quality of the fixing unit 200. The threshold value Ckn is set to an upper limit value of the number of times the pressure force is released, assuming a range in which operational defects of the pressure spring 202 do not become apparent. The other threshold values ​​Ckj are set to values ​​obtained by equally dividing the range between Ck1 and Ckn according to the number of threshold values, for example.

[0068] In this embodiment, while the image forming apparatus 100 is in operation, before the pressure force release count Ck reaches the threshold value Ck1, the following control is executed. That is, when the release conditions (1) to (3) are satisfied, the pressure force is immediately released. On the other hand, after the pressure force release count Ck reaches the threshold value Ck1, the following control is executed. That is, each time the pressure force release count Ck reaches the threshold value Ckj, the conditions for releasing the pressure force are changed so that the frequency of releasing the pressure force gradually decreases.

[0069] 10. Control after the pressure release count Ck reaches the threshold Ck As shown in Table 1, the image forming apparatus 100 sets, for each of the threshold values ​​Ckj (j=1 to 3), an elapsed time tsj (j=1 to 3) from the time the image forming apparatus 100 transitions to the sleep mode. The pressure is not released until the set elapsed time tsj has elapsed. Also, as shown in Table 1, the image forming apparatus 100 sets, for each of the threshold values ​​Ckj (j=1 to 3), an elapsed time tdj (j=1 to 3) from when the image forming apparatus 100 is turned on to when it is turned off. The pressure is not released until the set elapsed time tdj has elapsed. Note that the elapsed time tsj and the elapsed time tdj are set to be longer as j increases.

[0070] When the pressure release count Ck is smaller than the threshold Ck1 (=10,000), the pressure is immediately released when the release conditions (1) to (3) are satisfied, as described above. On the other hand, after the pressure release count Ck reaches the threshold Ck1, the pressure is not released until the set elapsed time tsj and the set elapsed time tdj have elapsed each time the pressure release count Ck reaches the threshold Ckj.

[0071] [Table 1]

[0072] By implementing the control as in this embodiment, after the pressure release count Ck reaches the threshold Ck1, the pressure release conditions change step by step, so that the frequency of pressure release per unit number of sheets gradually decreases. Therefore, it is possible to suppress abrupt changes in the quality of the fixing unit 200 caused by changes in the frequency of pressure release.

[0073] In this embodiment, a discrete threshold is set for the parameter related to the cumulative usage of the fixing unit 200, and the predetermined condition for releasing the pressure of the fixing unit is changed each time the threshold is reached, but the present invention is not limited to this. The predetermined condition for releasing the pressure of the fixing unit may be continuously set according to a continuous value that changes in the direction of increasing the cumulative usage. This allows the frequency of releasing the pressure to be continuously reduced. [Explanation of symbols]

[0074] 200 Fixing unit 210 Heater 220 Heater holder 250, 251, 252 Thermistor 260 Safety Elements 280 Adhesive 300 Pressure adjustment mechanism

Claims

1. an image forming section for forming an image on a recording material; A heating element; a pressure member that forms a nip portion with the heating member; a fixing unit that fixes an image formed on a recording material by heating the recording material passing through the nip portion; and a pressure adjusting mechanism that applies a pressure to the nip portion and releases or reduces the pressure. In an image forming apparatus having when a parameter related to an accumulated usage amount of the fixing unit is a first value, a frequency at which the pressure force is released or reduced is a first frequency, and when the parameter related to the accumulated usage amount is a second value that is greater than the first value, a frequency at which the pressure force is released or reduced is a second frequency that is less than the first frequency; a sheet counting unit for counting the number of recording materials that have passed through the fixing unit; The image forming apparatus according to claim 1, wherein the parameter relating to the accumulated usage amount is the number of sheets counted by the sheet counting means.

2. An image forming section for forming an image on a recording material; A heating element; a pressure member that forms a nip portion with the heating member; a fixing unit that fixes an image formed on a recording material by heating the recording material passing through the nip portion; and a pressure adjusting mechanism that applies a pressure to the nip portion and releases or reduces the pressure. In an image forming apparatus having when a parameter related to an accumulated usage amount of the fixing unit is a first value, a frequency at which the pressure force is released or reduced is a first frequency, and when the parameter related to the accumulated usage amount is a second value that is greater than the first value, a frequency at which the pressure force is released or reduced is a second frequency that is less than the first frequency; a drive time measuring unit for measuring a drive time of the fixing unit; The image forming apparatus according to claim 1, wherein the parameter relating to the accumulated usage amount is a drive time measured by the drive time measuring means.

3. A threshold value is set for a parameter related to an accumulated usage amount of the fixing unit, The image forming apparatus according to claim 1 or 2, characterized in that the pressure adjustment mechanism of the fixing unit is set so that, if a predetermined condition is satisfied before the parameter reaches the threshold value, the pressure is released or reduced by the pressure adjustment mechanism of the fixing unit, and, if the predetermined condition is satisfied after the parameter reaches the threshold value, the pressure is not released or reduced.

4. 4. The image forming apparatus according to claim 3, wherein the specified condition is at least one of the following: when a signal is received to detect a recording material jam, when a signal is received to turn off the power of the apparatus, and when a signal is received to transition to a sleep mode after the apparatus has not been used for a specified period of time.

5. A plurality of thresholds are set for the parameter, 4. The image forming apparatus according to claim 3, wherein the predetermined condition is changed to a condition that reduces the frequency of releasing or reducing the pressure each time the parameter reaches a threshold value in a direction in which the cumulative usage amount increases.

6. The image forming apparatus according to any one of claims 1 to 5, characterized in that the heating member has a cylindrical film and a heater arranged inside the film, the film is sandwiched between the heater and the pressure member, and the image on the recording material is heated through the film in the nip portion formed between the film and the pressure member.

Images