Image forming device

Abstract

To provide an image forming apparatus that can prevent wear of a fixing belt or a heater by bringing the fixing belt and the heater into a non-contact state with lubricating oil.SOLUTION: A fixing device 16 comprises: a fixing belt 30; a pressure roller 31; a heater 32; lubricating oil; and a pressure roller driving unit 40. The fixing belt 30 heats a toner image transferred to a sheet S to fix the toner image. The pressure roller 31 rotates the fixing belt 30 while being in contact therewith. The heater 32 heats the fixing belt 30. The lubricating oil forms an oil film between an inner peripheral surface of the fixing belt 30 and the heater 32. The pressure roller driving unit 40 rotates the pressure roller 31 to bring the fixing belt 30 and the heater 32 into a non-contact state with the lubricating oil.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus. [Background technology]

[0002] Patent Document 1 discloses a nip forming member that forms a nip by pressing a pressure roller against a fixing belt, and refers to friction between the nip forming member and the fixing belt. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-107086 A Summary of the Invention [Problem to be solved by the invention]

[0004] Patent Document 1 does not disclose the lubricating oil interposed between the fixing belt and the heater disposed opposite the inner circumferential surface of the fixing belt.

[0005] According to the present invention, the fixing belt and the heater are kept out of contact with each other by using lubricating oil, thereby making it possible to suppress wear of the fixing belt or the heater. [Means for solving the problem]

[0006] The image forming apparatus according to the present invention includes a fixing device. The fixing device includes a fixing belt, a pressure roller, a heater, lubricating oil, and a pressure roller drive unit. The fixing belt heats and fixes a toner image transferred to a sheet. The pressure roller rotates in contact with the fixing belt. The heater heats the fixing belt. The lubricating oil forms an oil film between the inner surface of the fixing belt and the heater. The pressure roller drive unit rotates the pressure roller so that the fixing belt and the heater are not in contact with each other due to the lubricating oil. Effect of the Invention

[0007] According to the image forming apparatus of the present invention, the fixing belt and the heater are kept out of contact with each other by the lubricating oil, so that wear of the fixing belt or the heater can be suppressed. [Brief description of the drawings]

[0008] [Figure 1] 1 is a diagram showing a multifunction peripheral including an image forming apparatus according to an embodiment of the present invention; [Diagram 2] 1 is a block diagram showing a configuration of an image forming apparatus according to an embodiment of the present invention; [Diagram 3] 2 is a cross-sectional view showing a configuration of a fixing device included in the image forming apparatus. [Figure 4] FIG. 2 is a diagram showing the Stribeck curve of a lubricating oil used in a fixing device. [Diagram 5] 1(a) to 1(c) are diagrams showing the relationship between lubricating oil and the Stribeck curve. [Figure 6] 5(a) and 5(b) are schematic diagrams illustrating changes in lubricating oil according to the present embodiment. [Figure 7] 2 is a block diagram showing a control configuration of the image forming apparatus or the fixing apparatus according to the embodiment; [Figure 8] FIG. 2 is a plan view illustrating a configuration of a heater of the fixing device. [Figure 9] FIG. 2 is a plan view illustrating a configuration of a cooling unit provided in a heater of the fixing device. [Figure 10] FIG. 4 is a plan view showing the configuration of the divided heaters. [Figure 11] FIG. 4 is a plan view showing the configuration of a cooling section of the split heater. [Figure 12] 5 is a flowchart showing a control process of the image forming apparatus according to the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference symbols and the description will not be repeated. In this embodiment, the drawings show an X-axis, a Y-axis, and a Z-axis that are perpendicular to each other. The Z-axis is parallel to the vertical plane, and the X-axis and the Y-axis are parallel to the horizontal plane.

[0010] In this embodiment, the Z-axis direction may be referred to as the "main scanning direction", the Y-axis direction may be referred to as the "sub-scanning direction", and the X-axis direction may be referred to as the "direction perpendicular to the main scanning direction and the sub-scanning direction".

[0011] The configuration of a multifunction peripheral 1 will be described with reference to Fig. 1. Fig. 1 is a diagram showing the multifunction peripheral 1 equipped with a fixing device 16 according to the present embodiment. The configuration of an image forming apparatus 3 equipped with the fixing device 16 according to the present embodiment will be described with reference to Fig. 2. Fig. 2 is a block diagram showing the configuration of an image forming apparatus 3 equipped with the fixing device 16 according to the present embodiment.

[0012] 1, the multifunction device 1 includes a document reading device 2 and an image forming device 3. The multifunction device 1 is, for example, an MFP (Multi Function Printer) that combines the functions of a scanner, a copier, a printer, a copy machine, a facsimile, and other devices.

[0013] The document reading device 2 includes, for example, a document tray, a document feeding section, a document transport section, a document reading section, optical members, a document discharge section, and a document discharge tray.

[0014] The image forming apparatus 3 includes a printer control unit 10, a printer driving unit 11, a sheet tray 12, a sheet feeding unit 13, a sheet transport unit 14, an image forming unit 15, a fixing unit 16 (fixing device 16), a sheet discharge unit 17, and a sheet discharge tray 18.

[0015] The printer control unit 10 controls the operation of each unit of the image forming device 3. The printer control unit 10 may function as a control unit that controls the operation of each unit of the multifunction device 1. Specific examples of the printer control unit 10 include a CPU (Central Processing Unit), an MPU (Micro-Processing Unit), or an ASIC (Application Specific Integrated Circuit).

[0016] The printer control unit 10 can control the size of the sheet S that passes through the fixing device 16. The printer control unit 10 selects the size of the sheet S based on the job instructions, and instructs the sheet feeding unit 13 on the size of the sheet S to be fed.

[0017] The printer drive unit 11 drives each part of the image forming device 3. The printer drive unit 11 may be a drive unit that operates each part of the multifunction device 1. Specific examples of the printer drive unit 11 are an electric motor, an electromagnetic solenoid, a hydraulic cylinder, and a pneumatic cylinder.

[0018] The sheet tray 12 stacks the sheets S. The sheets S are an example of a recording medium. The sheet tray 12 may include a tray and a lifting member. The sheet feeding unit 13 picks up and feeds the sheets S stacked on the sheet tray 12. A specific example of the sheet feeding unit 13 is a pickup roller.

[0019] The sheet conveying unit 14 conveys the sheet S fed from the sheet tray 12. The sheet conveying unit 14 has a conveying path. The conveying path starts from the sheet tray 12, passes through the image forming unit 15 and the fixing unit 16, and extends to a sheet discharging unit 17. The sheet conveying unit 14 may include a conveying roller and a registration roller in the conveying path.

[0020] A plurality of transport rollers may be disposed on the transport path and transport the sheet S. The registration rollers adjust the timing of transporting the sheet S to the image forming unit 15. The sheet transport unit 14 transports the sheet S from the sheet tray 12 to the sheet discharge unit 17 via the image forming unit 15 and the fixing unit 16.

[0021] The image forming unit 15 forms a toner image (not shown) on the sheet S by electrophotography based on the document image data. The document image data indicates an image of the original G, for example.

[0022] The fixing section 16 applies heat and pressure to the toner image developed on the sheet S to fix the toner image to the sheet S. The fixing section 16 may be referred to as a "fixing device 16."

[0023] The sheet discharge section 17 discharges the sheet S to the outside of the housing of the multifunction device 1 (image forming device 3). A specific example of the sheet discharge section 17 is a discharge roller.

[0024] The sheet discharge tray 18 holds the sheets S discharged by the sheet discharge section 17.

[0025] Next, a detailed configuration of the fixing device 16 according to the present embodiment will be described with reference to Fig. 3. Fig. 3 is a cross-sectional view showing the configuration of the fixing device 16 according to the present embodiment.

[0026] As shown in FIG. 3, the fixing device 16 includes a fixing belt 30, a pressure member 31, a heater 32, a heater holding member 33, a stay metal plate 34, a stay metal plate holding portion 35, a fixing belt holding portion 36, and a temperature measuring portion 37.

[0027] The fixing belt 30 heats the sheet S (FIG. 1) on which a toner image has been formed in the image forming section 15 shown in FIG. 1 and conveyed to the fixing device 16, thereby fixing the toner image transferred to the sheet S by heat.

[0028] 3 is endless. The fixing belt 30 has a substantially cylindrical shape. The fixing belt 30 is flexible.

[0029] The fixing belt 30 further includes a plurality of layers. For example, the fixing belt 30 includes a polyimide layer including polyimide, an elastic layer including an elastic material such as silicone rubber, and a release layer. The release layer is formed on the outer peripheral surface of the polyimide layer. The release layer is, for example, a heat-resistant film made of a fluororesin.

[0030] The pressure member 31 is in pressure contact (contact) with the fixing belt 30 while being driven to rotate, and causes the fixing belt 30 to rotate. The pressure member 31 is substantially cylindrical, and is disposed opposite the fixing belt 30. An example of the pressure member 31 is a pressure roller 31. Hereinafter, the pressure member 31 may be referred to as a "pressure roller 31".

[0031] The pressure roller 31 has a cylindrical core, a cylindrical elastic layer, and a release layer. The elastic layer is formed on the core. The release layer is formed so as to cover the surface of the elastic layer.

[0032] The core metal is made of, for example, stainless steel or aluminum. The elastic layer has elasticity and is made of, for example, silicone rubber. The release layer is made of, for example, fluororesin.

[0033] The heater 32 is connected to a power source (not shown) and generates heat. The heater 32 heats the fixing belt 30. The heater 32 is disposed at a position facing the inner circumferential surface of the fixing belt 30. The heater 32 may be pressed against the inner circumferential surface of the fixing belt 30 by a pressing member (not shown).

[0034] The heater 32 is, for example, a planar heater or a long and thin plate heater. An example of the heater 32 is a ceramic heater. The ceramic heater has a ceramic substrate and a resistance heating element. The heater 32 has a thickness of, for example, 1 mm. The heater 32 receives pressure from the pressure roller 31 via the fixing belt 30.

[0035] The pressure roller 31 is pressed against the fixing belt 30, thereby forming a nip N at the contact portion between the fixing belt 30 and the pressure roller 31. The pressure roller 31 is pressed against the fixing belt 30, thereby causing the heater 32 to be pressed against the inner circumferential surface of the fixing belt 30. Therefore, the fixing belt 30 is heated by the heater 32, and a toner image formed on a sheet S (FIG. 1) passing through the nip N is fixed to the sheet S.

[0036] Lubricating oil is applied to the inner circumferential surface of the fixing belt 30. The lubricating oil is interposed between the fixing belt 30 and the heater 32. The lubricating oil forms an oil film between the inner circumferential surface of the fixing belt 30 and the heater 32. The lubricating oil reduces friction between the fixing belt 30 and the heater 32.

[0037] A specific example of a lubricating oil is grease. Grease has a higher viscosity η than oil and is not fluid. For this reason, it is semi-solid or semi-fluid at room temperature. An example of grease is a liquid lubricating oil that has been made semi-solid or solid by uniformly dispersing a thickener such as calcium, sodium, lithium, or aluminum soap (salt of fatty acid).

[0038] The heater holding member 33 guides the fixing belt 30 so as to be able to rotate, and holds the heater 32 that heats the fixing belt 30 .

[0039] The stay metal plate 34 reinforces the heater holding member 33. The stay metal plate 34 is, for example, an elongated metallic stay member. The stay metal plate 34 may be formed in a U-shape, a C-shape, or a V-shape.

[0040] The stay sheet metal holding portion 35 holds the stay sheet metal 34 so as to fix it to the heater holding member 33 .

[0041] The fixing belt holding portion 36 guides the fixing belt 30 so as to be able to rotate.

[0042] Next, a Stribeck curve showing the characteristics of a lubricating oil will be described with reference to Fig. 4. Fig. 4 is a diagram showing the Stribeck curve of the lubricating oil used in the fixing device 16.

[0043] As shown in Fig. 4, the characteristics of the lubricating oil can be expressed as a Stribeck curve with the friction coefficient μ on the vertical axis and the oil film thickness h (=viscosity η x linear speed v / load w (Equation 1)) on the horizontal axis. Viscosity η indicates the viscosity η of the lubricating oil. Linear speed v indicates the linear speed v of the circumferential surface of pressure roller 31. Load w indicates the load with which pressure roller 31 presses fixing belt 30.

[0044] The properties of lubricating oils are divided into boundary lubrication, mixed lubrication, and liquid lubrication regions.

[0045] The boundary lubrication region indicates a region where the minimum oil film thickness ho of the lubricating oil is approximately 0. When the minimum oil film thickness ho ≈ 0, the temperature of the lubricating oil is high and the viscosity η is small. Therefore, the contact area between the fixing belt 30 and the heater 32 is large, and the friction between the fixing belt 30 and the heater 32 is large.

[0046] In the boundary lubrication region, as shown in (Equation 1), (viscosity η × linear velocity v) is small and the load w is large.

[0047] During the fixing operation of the sheet S by the fixing device 16, if there is an unused area of ​​the heater 32 where the sheet S does not pass, the lubricating oil in the unused area becomes hot and the viscosity η becomes small. As a result, the minimum oil film thickness of the lubricating oil becomes ho ≒ 0, and friction between the fixing belt 30 and the heater 32 increases. A state in which the lubricating oil is in the boundary lubrication region is not a desirable state because it shortens the lifespan of the fixing belt 30 and the heater 32.

[0048] In the mixed lubrication region, the minimum oil film thickness ho of the lubricating oil is approximately equal to the surface roughness R of the fixing belt 30 or the heater 32. When the minimum oil film thickness ho of the lubricating oil is approximately equal to the surface roughness R, the temperature of the lubricating oil is lower and the viscosity η is higher than in the boundary lubrication region. Therefore, the contact area between the fixing belt 30 and the heater 32 is smaller, and the friction between the fixing belt 30 and the heater 32 is smaller.

[0049] However, even if the lubricating oil is in the mixed lubrication region, it can easily transition to the boundary lubrication region due to changes in conditions, which is not necessarily a desirable state for maintaining the performance of the lubricating oil.

[0050] 4, in the boundary lubrication region and mixed lubrication region where the value of (viscosity η × linear velocity v) in (Equation 1) is small, the friction coefficient μ decreases as the product value increases. Also, in the fluid lubrication region where the value of (viscosity η × linear velocity v) in (Equation 1) is large, the friction coefficient μ increases as the value of (viscosity η × linear velocity v) increases.

[0051] The viscosity η of a lubricating oil changes depending on the temperature and durability of the lubricating oil. For example, in tribology, when there is lubricating oil between two objects in relative motion, the relationship between the value of "the product of viscosity η and linear velocity v" shown on the horizontal axis of Figure 4 and the "friction coefficient μ" shown on the vertical axis of Figure 4 changes depending on the lubrication state.

[0052] There is a fluid lubrication region where the inner circumferential surface of the fixing belt 30 and the heater 32 are separated by the lubricating oil (minimum oil film thickness ho>surface roughness R). In the fluid lubrication region shown in Fig. 4, when the viscosity η of the lubricating oil is high, the shear stress of the lubricating oil between the inner circumferential surface of the fixing belt 30 and the heater 32 increases. This increases the friction coefficient μ between the inner circumferential surface of the fixing belt 30 and the heater 32.

[0053] On the other hand, when the viscosity η of the lubricating oil is low, the shear stress of the lubricating oil between the inner circumferential surface of the fixing belt 30 and the heater 32 decreases. This reduces the friction coefficient μ between the inner circumferential surface of the fixing belt 30 and the heater 32.

[0054] Therefore, the friction coefficient μ of the lubricating oil is smallest when it is at the minimum point of the mixed lubrication region, as shown in Figure 4. However, as mentioned above, there is a risk that the mixed lubrication region can easily transition to the boundary lubrication region, so in order to extend the life of the lubricating oil, it is most preferable to maintain the hydrodynamic lubrication region even if the friction coefficient μ becomes somewhat larger.

[0055] Depending on the lubricating condition of the lubricating oil, the relationship between the value of "product of viscosity η and linear speed v" shown on the horizontal axis of Fig. 4 and the "friction coefficient μ" shown on the vertical axis of Fig. 4 changes. For this reason, the viscosity η and linear speed v of the lubricating oil are optimized according to the lubricating condition of the lubricating oil, and the lubricating oil is shifted to the hydrodynamic lubrication region. This suppresses the increase in the friction coefficient μ.

[0056] Next, the gist of the present invention will be described in more detail with reference to Figs. 5(a) to 6(b).

[0057] Fig. 5(a) is a cross-sectional view of the main part of the fixing device 16 as viewed in the main scanning direction. Fig. 5(a) shows an embodiment in which, for example, in a case where the fixing device 16 is capable of fixing up to A4 sheets S, multiple A5 sheets S, which are smaller than the A4 sheets S, are continuously fixed.

[0058] As shown in Fig. 5(a), in the fixing device 16, in the center where the A5 sheet S passes, the heat generated by the heater 32 is absorbed by the A5 sheet S. Therefore, the lubricating oil between the fixing belt 30 and the heater 32 has a lower temperature than the both ends. In Fig. 5(a), the center in the main scanning direction of the fixing belt 30 where the A5 sheet S passes is referred to as the "low temperature portion P." The oil film thickness h of the lubricating oil in the low temperature portion P is h1.

[0059] In contrast, at both ends in the main scanning direction of the fixing belt 30 where the A5 sheet S does not pass, the heat generated by the heater 32 is not absorbed by the A5 sheet S. Therefore, the lubricating oil between the fixing belt 30 and the heater 32 becomes hotter than the central portion. In FIG. 5(a), both ends in the main scanning direction of the fixing belt 30 where the A5 sheet S does not pass are described as "high temperature portions Q." The oil film thickness h of the lubricating oil at the high temperature portions Q is h2.

[0060] As shown in Fig. 5(b), the viscosity of the lubricating oil increases in the low temperature section P. The viscosity of the lubricating oil decreases in the high temperature section Q. Therefore, as shown in Fig. 5(a), the oil film thickness h1 of the lubricating oil in the low temperature section P is greater than the oil film thickness h2 of the lubricating oil in the high temperature section Q. In other words, h1>h2.

[0061] In an embodiment of the present invention, by adjusting one of the factors (oil film thickness h=viscosity η×linear speed v / load w) in (Equation 1), the oil film thickness h of the lubricating oil in the high temperature part Q, which is in the boundary lubrication region or mixed lubrication region (FIG. 4) of the Stribeck curve shown in FIG. 5(b), is shifted to the hydrodynamic lubrication region as shown in FIG. 5(c).

[0062] In addition, by increasing the temperature of the lubricating oil in the low temperature area P, the lubricating oil in the low temperature area P (center) is moved to the high temperature area Q (both ends), thereby flattening the oil film thickness h of the lubricating oil in the main scanning direction.

[0063] 6(a) and (b) are schematic diagrams showing only the lubricating oil in the fixing device 16 described in FIG. 5(a).

[0064] As shown in Fig. 6(a), the oil film thickness h in the low temperature part P (center) in the main scanning direction of the lubricating oil is h1, and the oil film thickness h in the high temperature parts Q (both ends) in the main scanning direction of the lubricating oil is h2.

[0065] According to the embodiment of the present invention, as shown in Fig. 6(b), the temperature of the lubricating oil in the low temperature part P increases, so the oil film thickness h decreases from h1 to h3. And, the viscosity η of the lubricating oil in the low temperature part P decreases, so the fluidity improves and it becomes easier to move to the high temperature part Q. Therefore, the oil film thickness h of the lubricating oil in the high temperature part Q increases from h2 to h3.

[0066] Therefore, as shown in FIG. 6(b), the oil film thickness h of the lubricating oil in the main scanning direction is flattened to h3, and the lubricating oil is generally stabilized in the hydrodynamic lubrication region of the Stribeck curve.

[0067] Next, with reference to Figs. 1 to 6(b) and further Figs. 7 to 11, the control of the fixing device 16 of the image forming apparatus 3 according to this embodiment and the detailed structure of the heater 32 will be described. Fig. 7 is a block diagram showing the control configuration of the image forming apparatus 3 or the fixing device 16 according to this embodiment. Fig. 8 is a plan view showing the configuration of the heater 32 of the fixing device 16. Fig. 9 is a plan view showing the configuration of a cooling section 45 provided in the heater 32 of the fixing device 16. Fig. 10 is a plan view showing the configuration of a divided heater. Fig. 11 is a plan view showing the configuration of the cooling section 45 of the divided heater.

[0068] As shown in FIG. 5, the fixing device 16 includes a pressure roller driving unit 40, a drive control unit 41, a temperature measurement unit 37, a power control unit 43, a cooling unit 45, a counter 46, and a timer 47.

[0069] The pressure roller driving unit 40 rotates the pressure roller 31 so that the fixing belt 30 and the heater 32 are in a non-contact state. Specific examples of the pressure roller driving unit 40 include a motor, as well as a gear, a transmission belt, and other transmission members that transmit the rotational force of the motor to the pressure roller 31.

[0070] According to this embodiment, the lubricating oil is stably maintained in the fluid lubrication region of the Stribeck curve. The image forming apparatus 3 can suppress wear of the fixing belt 30 or the heater 32 by keeping the fixing belt 30 and the heater 32 in a non-contact state using the lubricating oil. In addition, the life of the fixing device 16 and the image forming apparatus 3 can be extended.

[0071] In addition, when at least a portion of the fixing belt 30 and at least a portion of the heater 32 are in contact with each other, the pressure roller drive unit 40 may reduce the pressure applied by the pressure roller 31 to the fixing belt 30 to a second pressure force that is lower than the first pressure force during non-job processing.

[0072] The non-job processing time may be a warm-up period, or, when multiple jobs are being processed consecutively, a blank period from the end of a preceding job to the start of the next job.

[0073] The first pressure is the pressure applied by the pressure roller 31 to the fixing belt 30 during a normal warm-up period or blank period, and is the pressure applied when there is no imbalance in the oil film thickness h of the lubricating oil. The first pressure may be smaller than the pressure applied during the fixing operation.

[0074] The second pressure is a pressure applied by the pressure roller 31 to the fixing belt 30 during a normal warm-up period or blank period, and is a pressure applied when an imbalance occurs in the oil film thickness h of the lubricating oil. The second pressure may be smaller than the first pressure. When an imbalance occurs in the oil film thickness h of the lubricating oil, the oil film thickness h of the lubricating oil is reduced to such an extent that at least a part of the fixing belt 30 and at least a part of the heater 32 are in contact with each other.

[0075] 5(a), when small-sized sheets S are continuously subjected to the fixing process, the lubricating oil present at both ends of the fixing belt 30 in the main scanning direction becomes hot, generating high-temperature portions Q. The pressure roller driving unit 40 controls the pressure roller 31 to pressurize the high-temperature portions Q of the fixing belt 30 with a second pressure force.

[0076] In the high temperature part Q, which is pressurized by the second pressure force, the pressure force is small, so the oil film thickness h of the lubricating oil increases. That is, as shown in the Stribeck curve explained in FIG. 4, the oil film thickness h of the lubricating oil becomes thicker, and the state shown in FIG. 6(a) transitions to the state shown in FIG. 6(b). The lubricating oil in the high temperature part Q transitions from the boundary lubrication region or the mixed lubrication region to the hydrodynamic lubrication region. The lubricating oil in the low temperature part P remains in the hydrodynamic lubrication region.

[0077] According to this embodiment, the fixing belt 30 and the heater 32 are kept out of contact with each other by the lubricating oil, so that wear of the fixing belt 30 or the heater 32 can be more effectively suppressed.

[0078] The pressure roller driving unit 40 may rotate the pressure roller 31 at a linear speed v2 that is faster than the first linear speed v1 during non-job processing.

[0079] The first linear speed v1 is the linear speed v at which the pressure roller 31 rotates the fixing belt 30 during a normal warm-up period or blank period, and is the linear speed v when there is no imbalance in the oil film thickness h of the lubricating oil. The first linear speed v1 may be smaller than the linear speed v during the fixing operation.

[0080] The second linear speed v2 is the linear speed v at which the pressure roller 31 rotates the fixing belt 30 during a normal warm-up period or a blank period, and is the linear speed v when an imbalance occurs in the oil film thickness h of the lubricating oil. The second linear speed v2 may be greater than the first linear speed v1.

[0081] That is, the second linear velocity v2 may be greater than the first linear velocity v1, and may be smaller than the linear velocity v during the fixing operation.

[0082] As shown in FIG. 5(a), the pressure roller driving unit 40 controls the pressure roller 31 to rotate at a second linear velocity v2.

[0083] When the fixing belt 30 is rotated at the second linear velocity v2, the oil film thickness h of the lubricating oil becomes thicker in the high temperature portion Q of the fixing belt 30, and the state transitions from that shown in Fig. 6(a) to that shown in Fig. 6(b). As the value of (viscosity η × linear velocity v) in (Equation 1) increases, the lubricating oil transitions from the boundary lubrication region or mixed lubrication region to the fluid lubrication region.

[0084] According to this embodiment, the fixing belt 30 and the heater 32 are kept out of contact with each other by the lubricating oil, so that wear of the fixing belt 30 or the heater 32 can be more effectively suppressed.

[0085] The power control unit 43 controls the power supplied to the heater 32. The power control unit 43 supplies the heater 32 with a second power that is smaller than the first power during non-job processing.

[0086] The first power is the power supplied by the pressure roller 31 to rotate the fixing belt 30 during a normal warm-up period or blank period, and is the power when there is no imbalance in the oil film thickness h of the lubricating oil. The first power is smaller than the power during the fixing operation.

[0087] The second power is the power supplied by the pressure roller 31 to rotate the fixing belt 30 during a normal warm-up period or blank period, and is the power when an imbalance occurs in the oil film thickness h of the lubricating oil. The second power is smaller than the first power.

[0088] 8, the heater 32 has a heating element 44. An electrode 51 is connected to the heating element 44. The electrode 51 is connected to a power source (not shown) and supplies power to the heating element 44.

[0089] The electrodes 51 include electrodes 51a, 51b, .... The electrode 51a is connected to the side of the heating element 44 on the downstream side in the sub-scanning direction and extends parallel to the heating element 44. The electrode 51b is connected to the side of the heating element 44 on the upstream side in the sub-scanning direction and extends parallel to the heating element 44.

[0090] The electrode 51 may be divided in the main scanning direction. The electrode 51 may be capable of selectively supplying different amounts of electric power to the low temperature portion P or the high temperature portion Q of the heating element 44.

[0091] The heating element 44 generates Joule heat by power supplied from a power source (not shown) via the electrodes 51 , and heats the fixing belt 30 .

[0092] The heating element 44 extends in the main scanning direction. The heating element 44 has a resistivity higher than that of the material constituting the electrodes 51, and is a resistive heating element such as Ag / Pd (silver palladium), RuO2 (ruthenium oxide), Ta2N (tantalum nitride), or the like.

[0093] The heating element 44 is formed, for example, by printing a paste of ruthenium oxide or the like into a thick film and then firing the printed paste. The heating element 44 may also be formed by a thin film forming technique such as sputtering.

[0094] The electrode 51 is made of, for example, resinate Au with added elements such as rhodium, vanadium, bismuth, silicon, etc. The electrode 51 may be formed by thick-film printing of a paste of resinate Au and then firing the paste. The electrode 51 may be formed by a thin-film formation technique such as sputtering. The electrode 51 may be formed by stacking a plurality of Au layers.

[0095] As shown in FIG. 5(a), the power control unit 43 controls so as to supply the second power to the electrode 51 corresponding to the high temperature portion Q of the heating element 44.

[0096] When a second power is supplied to the electrode 51 corresponding to the high-temperature portion Q of the heating element 44, the second power is selectively supplied to the electrode 51 corresponding to the high-temperature portion Q of the heater 32 shown in Figure 5 (a), and the high-temperature portion Q of the heater 32 generates heat based on the second power.

[0097] Since the second power is smaller than the power during the fixing operation and the first power, the temperature of the high temperature part Q of the heater 32 drops. Therefore, as described in FIG. 4, the oil film thickness h of the lubricating oil becomes thicker, and the lubricating oil in the high temperature part Q transitions from the state shown in FIG. 6(a) to the state shown in FIG. 6(b). That is, the lubricating oil in the high temperature part Q transitions from the boundary lubrication region or the mixed lubrication region to the hydrodynamic lubrication region. The lubricating oil in the low temperature part P remains in the hydrodynamic lubrication region.

[0098] According to this embodiment, the fixing belt 30 and the heater 32 are kept out of contact with each other by the lubricating oil, so that wear of the fixing belt 30 or the heater 32 can be more effectively suppressed.

[0099] Next, the power control unit 43 may control the third power supplied to the heater 32 so as to heat a low-temperature portion P of the lubricating oil caused by the sheet S passing through the nip portion N (FIG. 3).

[0100] 5A, when the sheet S passes through the nip portion N between the heater 32 and the fixing belt 30, the sheet S absorbs heat. Therefore, the temperature of the portion through which the sheet S passes drops, becoming a low-temperature portion P.

[0101] The power control unit 43 controls the third power supplied to the heater 32 so as to heat the low-temperature portion P of the lubricating oil. The power at this time may be larger than the first power supplied by the pressure roller 31 to rotate the fixing belt 30 during the normal warm-up period or blank period. The third power may be larger or smaller than the power during the fixing operation.

[0102] The electrodes 51 connected to the heater 32 may be divided in the main scanning direction, and may be selectively energizable in the main scanning direction.

[0103] As shown in Fig. 5(a), the power control unit 43 selectively supplies a third power to the electrode 51 corresponding to the low-temperature part P of the heater 32. The low-temperature part P of the heater 32 is heated, and the temperature rises. As a result, the oil film thickness h1 decreases to an oil film thickness h3, and the lubricating oil in the low-temperature part P migrates from the right side to the left side in the hydrodynamic lubrication region, as shown by the Stribeck curve in Fig. 6(b).

[0104] On the other hand, when the oil film thickness h1 of the lubricating oil in the low temperature part P decreases, the reduced amount of lubricating oil moves from the low temperature part P to the high temperature part Q of the heater 32. As a result, the oil film thickness h2 of the lubricating oil in the high temperature part Q becomes the oil film thickness h3. Therefore, the oil film thickness of the lubricating oil in the low temperature part P and the high temperature part Q is flattened to the oil film thickness h3.

[0105] According to this embodiment, the oil film thickness h of the lubricating oil present in the nip portion N between the fixing belt 30 and the heater 32 is flattened, the fixing belt 30 and the heater 32 can be brought into a non-contact state, and wear of the fixing belt 30 or the heater 32 can be further effectively suppressed.

[0106] 9, the image forming apparatus 3 may include a cooling section 45 (45a, 45b). The cooling section 45 (45a, 45b) cools a high-temperature portion Q of the lubricating oil caused by the sheet S not passing through the nip portion N.

[0107] 5(a), the sheet S does not absorb heat in the portion of the nip portion N between the heater 32 and the fixing belt 30 where the sheet S does not pass. Therefore, the portion where the sheet S does not pass becomes a high temperature portion Q. The cooling portion 45 (45a, 45b) cools the high temperature portion Q of the lubricating oil.

[0108] A specific example of the cooling unit 45 (45a, 45b) may be a fan. A specific example of the cooling unit 45 (45a, 45b) may be an electronic cooling element such as a Peltier element.

[0109] 9, the cooling section 45 (45a, 45b) may be disposed at a position corresponding to the high temperature portion Q of the heat generating element 44 of the heater 32. That is, the cooling section 60a may be disposed facing the high temperature portion Q on the left side (the (+) side in the Y direction) of the heat generating element 44. The cooling section 60b may be disposed facing the high temperature portion Q on the right side (the (-) side in the Y direction) of the heat generating element 44.

[0110] The cooling section 60 may cool the heater 32 during the fixing operation of the fixing device 16. The cooling section 60 may cool the heater 32 during a warm-up period or a blank period.

[0111] As described in FIG. 6(a) and (b), when the cooling section 60 cools the high temperature section Q of the heater 32, the temperature of the high temperature section Q of the heater 32 decreases. Therefore, the oil film thickness h2 becomes thicker and becomes an oil film thickness h3. The lubricating oil in the high temperature section Q transitions from the boundary lubrication region or the mixed lubrication region to the hydrodynamic lubrication region, as shown in the Stribeck curve in FIG. 6(b). The lubricating oil in the low temperature section P may transition to the high temperature section Q, or may decrease from the oil film thickness h1 to the oil film thickness h3. The lubricating oil in the low temperature section P remains in the hydrodynamic lubrication region. Therefore, the low temperature section P and the high temperature section Q of the lubricating oil are flattened to the oil film thickness h3.

[0112] According to this embodiment, the oil film thickness h of the lubricating oil present in the nip portion N between the fixing belt 30 and the heater 32 is flattened, the fixing belt 30 and the heater 32 can be brought into a non-contact state, and wear of the fixing belt 30 or the heater 32 can be further effectively suppressed.

[0113] Next, the printer control unit 10 (FIG. 2) can control the size of the sheet S supplied to the fixing device 16. Based on the size of the sheet S, the pressure roller driving unit 40 can rotate the pressure roller 31 by the lubricating oil so that the fixing belt 30 and the heater 32 are in a non-contact state.

[0114] 5, the range of the low temperature area P and the high temperature area Q varies depending on the size of the sheet S. The printer control unit 10 can select and set the size of the sheet S to be supplied to the fixing device 16 depending on the contents of the job.

[0115] When the sheet S passes over the entire heating element 44 of the heater 32 (overall from the direction Y(+) to the direction Y(-)), no temperature difference occurs in the heater 32. Therefore, the pressure roller driving unit 40 does not need to correct the temperature of the heater 32.

[0116] When the sheet S passes through a part of the heating element 44 of the heater 32 (a part from the direction Y(+) to the direction Y(-)), a low temperature part P and a high temperature part Q are generated in the heater 32, as shown in Fig. 5. Therefore, the pressure roller driving unit 40 controls the pressure roller 31 to increase the temperature of the low temperature part P and decrease the temperature of the high temperature part Q.

[0117] The power control unit 43 may control the power based on the size of the sheet S. The cooling unit 45 may cool the high temperature unit Q based on the size of the sheet S.

[0118] According to this embodiment, the oil film thickness h of the lubricating oil can be suitably controlled in accordance with the size of the sheet S.

[0119] 8, the fixing device 16 of the image forming apparatus 3 may include a temperature measuring unit 37. The temperature measuring unit 37 measures the temperature of the lubricating oil and outputs temperature information. The pressure roller driving unit 40 may rotate the pressure roller 31 based on the temperature information so that the fixing belt 30 and the heater 32 are in a non-contact state due to the lubricating oil.

[0120] 8, the temperature measuring unit 37 may be disposed at an end in the main scanning direction of the heating element 44. That is, the temperature measuring unit 37 may be disposed at a position where it can measure the temperature of the high temperature part Q shown in FIG.

[0121] The temperature measuring unit 37 may measure the temperature of the heating element 44. The temperature measuring unit 37 may measure the temperature of the fixing belt 30. The temperature measuring unit 37 may measure (predict) the temperature of the lubricating oil by measuring the temperature of the heating element 44 or the fixing belt 30.

[0122] An example of the temperature measuring unit 37 is a thermistor, a thermostat, or a thermocouple.

[0123] The power control unit 43 may control the power based on the temperature information. The cooling unit 45 may cool the high temperature unit Q based on the temperature information.

[0124] According to this embodiment, the oil film thickness h of the lubricating oil can be suitably controlled in accordance with the temperature of the high temperature part Q measured by the temperature measuring part 37.

[0125] Next, the image forming apparatus 3 according to the present embodiment may further include a counter 46. The counter 46 counts the cumulative number of sheets S processed in one job, or the cumulative number of sheets S processed since the image forming apparatus 3 was installed, and outputs the count information. When the count information exceeds a threshold, the pressure roller driving unit 40 may rotate the pressure roller 31 by the lubricating oil so that the fixing belt 30 and the heater 32 are in a non-contact state.

[0126] The counter 46 can be realized by an ASIC (Application Specific Integrated Circuit). For example, if the threshold for the cumulative number of sheets S processed in one job is set to 50, and the cumulative number of sheets S processed in one job is 100, the counter 46 counts to 100. The counter 46 outputs count information indicating that the count exceeds the threshold.

[0127] For example, when the threshold for the cumulative number of sheets since the image forming device 3 was installed in the office is set to 500 sheets, the counter 46 may count that the cumulative number is 600 sheets. The counter 46 outputs count information indicating that the cumulative number has exceeded the threshold.

[0128] The pressure roller driving unit 40 drives the pressure roller 31 so that the fixing belt 30 and the heater 32 are in a non-contact state by the lubricating oil based on the count information indicating that the cumulative number of sheets exceeds the threshold value. As for the specific driving method, all the specific examples of the present embodiment can be applied.

[0129] The drive control unit 41 may predict and calculate the maximum temperature (Tmax) of the lubricating oil.

[0130] The drive control unit 41 may determine whether or not the maximum temperature (Tmax) of the lubricating oil exceeds a first threshold value (A (° C.)).

[0131] The cooling section 45 may cool the high temperature section Q when the maximum temperature (Tmax) of the lubricating oil exceeds a first threshold value (A (° C.)).

[0132] When the maximum temperature (Tmax) of the lubricating oil exceeds a first threshold value (A (°C)), the pressure roller drive unit 40 may rotate the pressure roller 31 at a linear speed v2 that is faster than the first linear speed v1 during non-job processing.

[0133] The drive control unit 41 may determine whether the maximum temperature (Tmax) of the lubricating oil exceeds a second threshold (B (°C)) that is higher than the first threshold (A (°C)). That is, the drive time of the pressure roller 31 may be changed depending on whether the maximum temperature (Tmax) of the lubricating oil is higher than the first threshold (A (°C)) and lower than the second threshold (B (°C)) or whether the maximum temperature (Tmax) of the lubricating oil is higher than the second threshold (B (°C)).

[0134] When it is determined that the second threshold value (B (° C.)) is not exceeded, the drive control section 41 may drive the pressure roller 31 by increasing the drive time of the pressure roller 31 by (+a seconds).

[0135] When the drive control section 41 determines that the second threshold value (B (° C.)) is exceeded, the drive control section 41 increases the drive time of the pressure roller 31 by more than a seconds (+b seconds) and drives the pressure roller 31.

[0136] According to this embodiment, the oil film thickness h of the lubricating oil can be suitably controlled in accordance with the number of sheets S that the fixing device 16 has processed.

[0137] Next, the image forming apparatus 3 may further include a timer 47. The timer 47 may measure the accumulated time processed in one job or the accumulated time elapsed since the image forming apparatus 3 was installed, and output the measurement information. When the measurement information exceeds a threshold value (Tmin), the pressure roller driving unit 40 may rotate the pressure roller 31 so that the fixing belt 30 and the heater 32 are in a non-contact state by the lubricating oil.

[0138] The timer 47 may be realized by an ASIC. For example, when a threshold (Tmin) of the accumulated time processed by one job is set to 1 minute, the timer 47 may time that the accumulated time processed by one job is 2 minutes. The timer 47 outputs timer information indicating that the accumulated time exceeds the threshold (Tmin).

[0139] For example, when a threshold (Tmin) of the accumulated time that has elapsed since the image forming apparatus 3 was installed in the office is set to 50 hours, the timer 47 may time that the accumulated time is 60 hours. The timer 47 outputs timer information indicating that the accumulated time has exceeded the threshold (Tmin).

[0140] Based on timer information indicating that the accumulated time exceeds a threshold value (Tmin), the pressure roller driving unit 40 drives the pressure roller 31 so that the fixing belt 30 and the heater 32 are in a non-contact state by the lubricating oil. As for the specific driving method, all the specific examples of the present embodiment can be applied.

[0141] The drive control unit 41 may predict and calculate the maximum temperature (Tmax) of the lubricating oil.

[0142] The drive control unit 41 may determine whether or not the maximum temperature (Tmax) of the lubricating oil exceeds a first threshold value (A (° C.)).

[0143] The cooling section 45 may cool the high temperature section Q when the maximum temperature (Tmax) of the lubricating oil exceeds a first threshold value (A (° C.)).

[0144] When the maximum temperature (Tmax) of the lubricating oil exceeds a first threshold value (A (°C)), the pressure roller drive unit 40 may rotate the pressure roller 31 at a linear speed v2 that is faster than the first linear speed v1 during non-job processing.

[0145] The drive control unit 41 may determine whether or not the maximum temperature (Tmax) of the lubricating oil exceeds a second threshold value (B (° C.)) that is higher than the first threshold value (A (° C.)).

[0146] When it is determined that the second threshold value (B (° C.)) is not exceeded, the drive control section 41 may drive the pressure roller 31 by increasing the drive time of the pressure roller 31 by (+a seconds).

[0147] When the drive control section 41 determines that the second threshold value (B (° C.)) is exceeded, the drive control section 41 increases the drive time of the pressure roller 31 by more than a seconds (+b seconds) and drives the pressure roller 31.

[0148] According to this embodiment, the oil film thickness h of the lubricating oil can be suitably controlled in accordance with the accumulated processing time of the fixing device 16.

[0149] Next, as shown in FIGS. 10 and 11, the heater 32 may include a first heating element piece 440b, and second heating element pieces 440a and 440c adjacent to the first heating element piece 440b in the main scanning direction.

[0150] 10, the fixing device 16 includes a heater 32, a heating element 44, an electrode 51, and a temperature measuring unit 37. As shown in FIG.

[0151] The heating element 44 includes a plurality of heating element pieces 440. The heating element pieces 440 include a first heating element piece 440b, a second heating element piece 440a, a second heating element piece 440c, . . .

[0152] As described in Fig. 5, for example, when a small-sized sheet S is subjected to a fixing process, the sheet S passes through the first heating element piece 440b. Therefore, the lubricating oil present in the first heating element piece 440b corresponds to the low temperature section P shown in Fig. 5. The lubricating oil present in the second heating element piece 440a and the second heating element piece 440c corresponds to the high temperature section Q shown in Fig. 5.

[0153] 10, the electrodes 51 include an electrode 51c, an electrode 51d, an electrode 51e, .... The first heating element piece 440b is connected to the electrode 51c. The second heating element piece 440a is connected to the electrode 51d. The second heating element piece 440c is connected to the electrode 51e. The electrodes 51 are connected to a power source (not shown) and supply power to the heating elements 44, respectively.

[0154] The electrode 51c is connected to the side of the first heating element piece 440b on the downstream side in the sub-scanning direction and extends parallel to the first heating element piece 440b. The electrode 51d is connected to the side of the second heating element piece 440a and the second heating element piece 440c on the downstream side in the sub-scanning direction and extends parallel to the second heating element piece 440a and the second heating element piece 440c. The electrode 51e is connected to the side of the first heating element piece 440b, the second heating element piece 440a, and the second heating element piece 440c on the upstream side in the sub-scanning direction and extends parallel to the first heating element piece 440b, the second heating element piece 440a, and the second heating element piece 440c.

[0155] The electrodes 51c, 51d, and 51e may each be further divided in the main scanning direction. The electrodes 51 may be capable of selectively supplying different amounts of electric power to the low temperature portion P or the high temperature portion Q of the heating element 44.

[0156] The heating element 44 generates Joule heat by power supplied from a power source (not shown) via the electrodes 51 , and heats the fixing belt 30 .

[0157] As shown in FIG. 10, the temperature measuring unit 37 includes temperature measuring unit 37a, temperature measuring unit 37b, .... Temperature measuring unit 37a is disposed near the first heating element piece 440b, measures the temperature of the lubricating oil present in the first heating element piece 440b, and outputs temperature information. Temperature measuring unit 37b is disposed near the second heating element piece 440c, measures the temperature of the lubricating oil present in the second heating element piece 440c, and outputs temperature information. Temperature measuring unit 37b may be disposed near the second heating element piece 440c.

[0158] The temperature measuring unit 37a may be disposed at the end of the first heating element piece 440b in the main scanning direction (the Y(+) side or the Y(-) side). This is because, when a small-sized sheet S having a width smaller than the width of the first heating element piece 440b in the main scanning direction is subjected to fixing processing, the end of the first heating element piece 440b in the main scanning direction (the Y(+) side or the Y(-) side) may become the high-temperature part Q described in FIG. 5(a).

[0159] The temperature measuring unit 37b may be disposed at the end (Y(-) side) of the second heating element piece 440c in the main scanning direction. This is because when a medium-sized sheet S having a width larger than the width of the first heating element piece 440b in the main scanning direction and smaller than the width of the second heating element piece 440c in the main scanning direction is fixed, the end (Y(-) side) of the second heating element piece 440c in the main scanning direction may become a high temperature area Q.

[0160] Next, as shown in FIG. 11, the cooling section 45 includes a cooling section 45c, a cooling section 45d, a cooling section 45e, a cooling section 45f, . . .

[0161] The cooling section 45d and the cooling section 45e may be disposed at the end of the first heating element piece 440b in the main scanning direction (the Y(+) side or the Y(-) side). This is because, when a small-sized sheet S having a width smaller than the width of the first heating element piece 440b in the main scanning direction is subjected to fixing processing, the end of the first heating element piece 440b in the main scanning direction (the Y(+) side or the Y(-) side) may become a high-temperature part Q.

[0162] The cooling section 45c may be disposed at the end (direction Y(+) side) of the second heating element piece 440a in the main scanning direction. This is because, when a medium-sized sheet S having a width larger than the width of the first heating element piece 440b in the main scanning direction and smaller than the width of the second heating element piece 440a in the main scanning direction is fixed, the end (direction Y(+) side) of the second heating element piece 440a in the main scanning direction may become a high temperature section Q.

[0163] The cooling section 45f may be disposed at the end (Y(-) side) of the second heating element piece 440c in the main scanning direction. This is because, when a medium-sized sheet S having a width larger than the width of the first heating element piece 440b in the main scanning direction and smaller than the width of the second heating element piece 440c in the main scanning direction is fixed, the end (Y(-) side) of the second heating element piece 440c in the main scanning direction may become a high temperature section Q.

[0164] The cooling section 45c, the cooling section 45d, the cooling section 45e, and the cooling section 45f may cool the high temperature section Q, respectively.

[0165] 5(a), when sheets S smaller than the first heating element piece 440b are continuously subjected to the fixing process, the lubricating oil present at the end of the first heating element piece 440b becomes hot, the center of the first heating element piece 440b becomes a low temperature area P, and both end portions of the first heating element piece 440b become high temperature areas Q. The pressure roller driving unit 40 controls the pressure roller 31 to pressurize the fixing belt 30 with a second pressure force.

[0166] Similarly, when medium-sized sheets S larger than the first heating element piece 440b are continuously subjected to the fixing process, the lubricating oil present at the end of the first heating element piece 440b becomes hot, the lubricating oil present in the first heating element piece 440b becomes a low-temperature part P, and the second heating element piece 440a and the second heating element piece 440c become a high-temperature part Q. The pressure roller driving unit 40 controls the pressure roller 31 to pressurize the fixing belt 30 with a second pressure force.

[0167] The pressure roller driving unit 40 may rotate the pressure roller 31 at a linear speed v2 that is faster than the first linear speed v1 during non-job processing.

[0168] The power control unit 43 controls the power supplied to the heater 32. The power control unit 43 may supply, to the heater 32, a second power that is smaller than the first power during non-job processing.

[0169] The power control unit 43 may perform control so as to supply the second power to the electrode 51c corresponding to the high temperature portion Q of the first heating piece 440b.

[0170] According to this embodiment, the first heating element piece 440b and the second heating element piece 440a and second heating element piece 440c can be used depending on the size of the sheet S, and the low temperature part P and high temperature part Q of the lubricating oil are clearly defined, allowing the temperature of the lubricating oil to be efficiently adjusted.

[0171] Next, the control of the image forming apparatus 3 according to the present embodiment will be described with reference to Fig. 12. Fig. 12 is a flowchart showing the control of the image forming apparatus 3 according to the present embodiment. As shown in Fig. 12, the flowchart includes steps S10 to S26.

[0172] 12, the pressure roller driving unit 40 determines whether the cumulative driving time of the pressure roller 31 exceeds a predetermined time (Ymin). If it exceeds the predetermined time (Yes in step S10), the process proceeds to step S12. If it does not exceed the predetermined time (No in step S10), the process proceeds to step S24.

[0173] If the answer is Yes in step S10, the drive control section 41 predicts and calculates the maximum temperature (Tmax) of the lubricating oil in step S12. The process proceeds to step S14.

[0174] In step S14, the drive control unit 41 determines whether the maximum temperature (Tmax) of the lubricating oil exceeds the first threshold value (A (°C)). If it exceeds the first threshold value (Yes in step S14), the process proceeds to step S16. If it does not exceed the first threshold value (No in step S14), the process proceeds to step S24.

[0175] In step S16, the power control unit 43 corrects the fixing temperature by −C (° C.) The process proceeds to step S18.

[0176] In step S18, the drive control unit 41 corrects the drive speed by +X (mm / s). The process proceeds to step S20.

[0177] In step S20, the drive control unit 41 determines whether the maximum temperature (Tmax) of the lubricating oil exceeds the second threshold value (B (°C)). If it exceeds the second threshold value (Yes in step S20), the process proceeds to step S22. If it does not exceed the second threshold value, the process proceeds to step S26.

[0178] In step S22, the drive control unit 41 corrects the drive time by +b (seconds). The process proceeds to step S24.

[0179] In step S24, the drive control unit 41 controls the drive of the pressure roller drive unit 40. Then, the process ends.

[0180] If the result of step S20 is No, the drive control unit 41 corrects the drive time by +a (seconds). The process proceeds to step S24.

[0181] If the answer is No in step S14, the process proceeds to step S24.

[0182] If the answer is No in step S12, the process proceeds to step S24.

[0183] The embodiments of the present invention have been described above with reference to the drawings. However, the present invention is not limited to the above embodiments, and can be implemented in various forms without departing from the scope of the present invention. The drawings are mainly schematic illustrations of each component for ease of understanding, and the thickness, length, number, etc. of each component shown in the drawings are different from the actual ones due to the convenience of drawing. In addition, the materials, shapes, dimensions, etc. of each component shown in the above embodiments are merely examples, and are not particularly limited, and various modifications are possible within a scope that does not substantially deviate from the effects of the present invention. [Industrial Applicability]

[0184] The present invention can be used in the field of image forming apparatuses. [Explanation of symbols]

[0185] 3. Image forming equipment 16 Fixing device 30 Fixing belt 31 Pressure roller 32 Heater 37 Temperature measurement section 40 Pressure roller drive unit 41 Drive control unit 43 Power Control Unit 44 Heating element

Claims

1. An image forming apparatus including a fixing device, The fixing device is a fixing belt for heating and fixing the toner image transferred onto the sheet; a pressure roller that rotates the fixing belt in contact with the fixing belt; a heater for heating the fixing belt; a lubricating oil that forms an oil film between the inner circumferential surface of the fixing belt and the heater; a pressure roller driving unit that rotates the pressure roller so that the fixing belt and the heater are in a non-contact state by the lubricating oil; Equipped with An image forming apparatus, wherein when at least a portion of the fixing belt and at least a portion of the heater are in contact with each other, the pressure roller drive unit reduces the pressure applied by the pressure roller to the fixing belt to a second pressure force that is lower than the first pressure force during non-job processing.

2. The image forming apparatus according to claim 1 , wherein the pressure roller driving unit rotates the pressure roller at a second linear speed that is faster than a first linear speed during non-job processing.

3. A power control unit that controls the power supplied to the heater is further provided. The image forming apparatus according to claim 1 , wherein the power control section supplies a second power to the heater during non-job processing, the second power being smaller than the first power.

4. A power control unit that controls the power supplied to the heater is further provided. The image forming apparatus according to claim 1 , wherein the power control unit controls the third power supplied to the heater so as to heat a low-temperature portion of the lubricating oil caused by a sheet passing through a nip portion.

5. a cooling section for cooling a high-temperature portion of the lubricating oil caused when the sheet does not pass through the nip section; The image forming apparatus of claim 1 , further comprising:

6. An image forming apparatus including a fixing device, The fixing device is a fixing belt for heating and fixing the toner image transferred onto the sheet; a pressure roller that rotates the fixing belt in contact with the fixing belt; a heater for heating the fixing belt; a lubricating oil that forms an oil film between the inner circumferential surface of the fixing belt and the heater; a pressure roller driving unit that rotates the pressure roller so that the fixing belt and the heater are in a non-contact state by the lubricating oil; Equipped with a printer control unit that controls a size of a sheet to be supplied to the fixing device; The pressure roller driving unit rotates the pressure roller based on the size so that the fixing belt and the heater are in a non-contact state by the lubricating oil.

7. a temperature measuring unit for measuring the temperature of the lubricating oil and outputting temperature information; The image forming apparatus according to claim 1 , wherein the pressure roller driving unit rotates the pressure roller based on the temperature information so that the lubricating oil keeps the fixing belt and the heater out of contact with each other.

8. a counter that counts the cumulative number of sheets processed in one job or the cumulative number of sheets processed since the image forming apparatus was installed and outputs count information; 6. The image forming apparatus according to claim 1, wherein the pressure roller driving unit rotates the pressure roller so that the fixing belt and the heater are in a non-contact state by the lubricating oil when the count information exceeds a threshold value.

9. An image forming apparatus including a fixing device, The fixing device is a fixing belt for heating and fixing the toner image transferred onto the sheet; a pressure roller that rotates the fixing belt in contact with the fixing belt; a heater for heating the fixing belt; a lubricating oil that forms an oil film between the inner circumferential surface of the fixing belt and the heater; a pressure roller driving unit that rotates the pressure roller so that the fixing belt and the heater are in a non-contact state by the lubricating oil; Equipped with a timer that measures a cumulative time that has been processed in one job or a cumulative time that has elapsed since the image forming apparatus was installed and outputs the measured time information; When the timing information exceeds a threshold value, the pressure roller drive unit rotates the pressure roller so that the fixing belt and the heater are brought into a non-contact state by the lubricating oil.

10. 10. The image forming apparatus according to claim 1, wherein the heater includes a first heating element piece and a second heating element piece adjacent to the first heating element piece in a main scanning direction.

Images