Image forming device

Abstract

To reduce power consumption necessary for maintaining a temperature of a fixing heater.SOLUTION: An image forming apparatus has: a fixing device that includes a cylindrical fixing film (808), a fixing heater (811) arranged in an internal space of the fixing film (808) and generating heat upon energization from a commercial power supply (902), and a pressure roller (809), and that sandwiches and conveys a sheet on which a toner image is formed at a fixing nip (810) to fix the toner image to the sheet; control means (820) that controls power supplied from the commercial power supply to the fixing heater; and a plurality of paper feeding units (816, 201, 202) that feed sheets toward the fixing nip. The paper feeding units have different conveyance distances from a paper feeding position to the fixing nip, and the control means (820) sets the maximum energization duty on the basis of the paper feeding unit to be used.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Conventionally, electrophotographic image forming apparatuses have a fixing device that heats and conveys a toner image transferred onto a sheet of paper, thereby forming a fixed image. The fixing device includes a heating section including a fixing heater with a heating resistor that generates heat when energized from a commercial power source, a pressure roller for forming a fixing nip with respect to the heating section, a temperature detection section that detects the temperature of the heating section, and a power supply control section that controls the power supply to the fixing heater. The amount of power supplied to the fixing heater per unit time is controlled based on the difference between the detection result of the temperature detection section and a target temperature determined based on the basis weight, size, etc. of the paper, thereby controlling the temperature of the fixing heater. The toner image is then heated and fixed to the paper by nipping and conveying the paper through the fixing nip.

[0003] Fixing devices are designed to ensure that the time required from receiving a print command until the first sheet of paper is completely ejected from the paper ejection section of the image forming device (First Print Out Time, hereafter referred to as "FPOT") satisfies the desired product performance. The lower the resistance value of the heating resistor, the greater the amount of heat generated per unit time, allowing the temperature of the heating section to rise in a shorter time. On the other hand, the lower the resistance value of the heating element, the greater the amount of current flowing per unit time. This necessitates the need for higher ratings for the electrical components mounted in the control section that controls the current flow. Therefore, the heating resistor is set to a value appropriate for product specifications, such as the transport time from the start of paper transport until it reaches the fixing nip, as well as the type of paper, such as paper size and basis weight.

[0004] Patent Document 1 discloses a means for reducing the influence of the temperature rise waiting time of the fixing device on FPOT by starting power supply control to the fixing device at the same time as the image forming apparatus receives image information. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 5-328075 Summary of the Invention [Problem to be solved by the invention]

[0006] The temperature control of the fixing device described in Patent Document 1 controls the amount of power supplied based on the difference between the detection result of the temperature detection unit and the target temperature, so power is supplied to the fixing device regardless of the required transport time. Furthermore, because temperature control is initiated in response to a print start command, if paper is fed from a paper feed unit with a long transport distance from the paper feed position to the fixing nip, the fixing device reaches the target temperature quickly in accordance with the difference in transport time due to the difference in paper feed position. As a result, it is necessary to maintain the temperature of the heating unit against natural heat dissipation during the period from when the fixing heater reaches the target temperature until the recording material reaches the fixing nip, which consumes unnecessary power for heat fixing of the toner image on the paper.

[0007] SUMMARY OF THE INVENTION In view of the above, an object of the present invention is to reduce power consumption during the period from when the fixing heater reaches a target temperature until the recording material reaches the fixing nip. [Means for solving the problem]

[0008] In order to achieve the above object, an image forming apparatus according to the present invention includes a fixing device including a cylindrical fixing film, a fixing heater that is disposed in an internal space of the fixing film and generates heat when energized by a commercial power source, and a pressure roller, and fixes a toner image formed on the paper by nipping and conveying the paper at a fixing nip formed by the fixing film and the pressure roller, the fixing device comprising: a control means that controls power supplied from the commercial power source to the fixing heater; and a plurality of paper feed units that feed paper toward the fixing nip, wherein a paper transport distance from a paper feed position of each of the plurality of paper feed units to the fixing nip is different for each paper feed unit, and the control means sets a maximum supply power that can be supplied to the fixing heater per unit time to a first value when using a first paper feed unit among the plurality of paper feed units, the first paper feed unit having a paper transport distance from the paper feed position to the fixing nip being a first transport distance; No. When a second paper feed unit having a second transport distance longer than the first transport distance is used, the maximum supply power is limited to a second value lower than the first value. [Effects of the Invention]

[0009] According to the present invention, by setting the maximum power supply per unit time to the fixing heater according to the paper feed position, it is possible to reduce the power consumption required to maintain the temperature of the fixing heater during the period until the paper reaches the fixing nip. [Brief explanation of the drawings]

[0010] [Figure 1] Flowchart for setting the maximum current duty per unit time [Figure 2] Schematic diagram of an image forming apparatus [Figure 3] A diagram showing the transport distance from the paper feed position of each paper feed unit to the fixing nip [Figure 4] A diagram showing the maximum power duty for each paper feed unit [Figure 5] FIG. 1 shows the temperature gradient of the fixing heater during the heating period before fixing. [Figure 6] FIG. 10 is a diagram showing the relationship between the commercial power supply voltage and the pre-fixing heating period and required duty for each paper feed unit in the second embodiment. [Figure 7] 10 is a flowchart for setting a maximum current duty per unit time in the second embodiment. [Figure 8] Schematic diagram of an image forming apparatus equipped with one paper feed unit [Figure 9] Schematic diagram of the power supply circuit to the fixing heater DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. [Example]

[0012] FIG. 2 is a schematic diagram of an electrophotographic laser beam printer, an example of an image forming apparatus. The photosensitive drum 801 is an image carrier with a photosensitive layer formed on its surface. After the surface of the photosensitive drum 801 is charged by a charging roller 802, an electrostatic latent image is formed on the photosensitive drum 801 by laser light irradiated from a laser scanner 803. Then, a developing roller 804 transfers toner 805 onto the photosensitive drum 801 as a toner image. The transfer roller 906 is an example of a transfer unit that supplies transfer charge to paper (recording material) 807. The toner image is transferred to the paper 807 at the transfer nip between the photosensitive drum 801 and the transfer roller 806. The fixing film 808 is a cylindrical rotating body whose longitudinal direction is the depth direction in FIG. 2. The pressure roller 809 is a rotating body that forms a fixing nip 810 by applying pressure to the fixing film 808. The fixing heater 811 is located within the fixing film's internal space. The fixing heater 811 is made of, for example, a ceramic substrate, a heat-generating layer, and a protective layer. A stay 812 and a reinforcing member 813, which serve as supporting members for supporting the fixing heater 811, are provided within the fixing film 808. A thermistor 814 is a temperature detector that detects the temperature of the fixing heater 811. The fixing device fixes the toner image onto the paper 807 by heating the fixing heater 811, which is connected in series to an overheat protection element (not shown) made of a thermal fuse and a power supply drive unit. The paper 807 is then ejected from the fixing nip 811 to the outside of the image forming apparatus via a paper ejection port 815. A first paper feed unit 816 is provided in the image forming apparatus main body as a paper feed unit for the paper 807. A paper feed roller 817 feeds the paper 807 from a paper feed position, and the paper fed by the paper feed roller 817 is transported along the transport path 203 by transport rollers 818 and 819.

[0013] FIG. 9 is a schematic diagram of the electrical connection of a power supply circuit to the fixing heater 811. The CPU 820, which is the control means of the image forming apparatus, controls the supply of power to the fixing heater 811 from a commercial power source 902 via a triac 901. When the image forming apparatus starts printing, temperature control of the fixing heater 811 begins. The CPU 820 controls the output of the FSRD signal based on the detection result of the thermistor 814. To increase the temperature of the fixing heater 811, the CPU 820 outputs an H level FSRD signal to turn on a transistor 903. Current flowing through the transistor 903 drives a phototriac coupler 904, supplying a gate current to the triac 901. As a result, the triac 901 transitions to a conductive state, and current is supplied to the fixing heater 811 via an overheat protection element 905. A coil 906 suppresses electrical noise generated when the triac 901 transitions to a conductive state. Resistors 907 and 908 limit the current. The FPOT (the time it takes for the first sheet of paper to be ejected from the image forming device after printing has started) of an image forming device is, for example, 2 It is specified that the time is 7 seconds when the conveyance speed of the paper 807 is 150 mm / sec, the width of the fixing nip 810 is 10 mm, and the distance from the fixing nip 810 to the paper discharge port 815 is 50 mm. In this case, the heating period t1 before fixing from the start of the printing operation until the paper 807 reaches the fixing nip 810 is expressed as t1 = FPOT - (297 + 10 + 50) / conveyance speed, which is approximately 4.62 seconds.

[0014] Assume that the image forming apparatus is installed in an environment with an ambient temperature of 15°C, and that the fixing heater 811 must be heated to, for example, 200°C by the time of the pre-fixing heating period t1 to properly fix the toner image to the paper 807. In this case, the fixing device requires, for example, approximately 3080 J of energy. If the power supply voltage of the commercial power supply 902 is, for example, 100 Vac and the power is supplied at 100% duty for the period t1, the appropriate resistance value of the fixing heater 811 is approximately 15 Ω. The triac 901 control period of the CPU 820 is, for example, in units of four half-waves of the commercial power supply 902 frequency, the minimum unit of power supply to the fixing heater 811 is in units of 1.8° of the phase angle of the commercial power supply 902, and the power supply voltage of the commercial power supply 902 is 100 Vac.

[0015] Incidentally, in order to allow image forming apparatuses to store and accommodate a greater amount or a greater variety of paper in the paper feed unit, an optional external paper feed device may be added to the apparatus body as a product development option. Figure 8 is a schematic diagram of an image forming apparatus equipped with only one paper feed unit. In contrast, Figure 2 is a schematic diagram of an image forming apparatus equipped with multiple paper feed units and connected to an optional external paper feed device.

[0016] When using paper stored in an optional external paper feed device, the transport time required from the start of paper feeding to transporting the paper to the fixing nip is longer than when feeding paper from a main body paper feed device. Specifically, the image forming apparatus of this embodiment has three paper feed units that store paper 807 and feed the stored paper. The first paper feed unit is the first paper feed unit 816, which is standard equipment on the image forming apparatus. The second paper feed unit is the second paper feed unit 201, which is connected below the first paper feed unit 816 as an optional external paper feed device. The third paper feed unit is the third paper feed unit 202, which is connected below the second paper feed unit 201 as an optional external paper feed device. The transport path 203, indicated by a dotted line, is a common transport path for paper 807 from each paper feed unit to the fixing nip 810. The transport paths from each paper feed unit to the transport roller 818 are indicated by path 204 (dashed line), path 205 (one-dot dash line), and path 206 (two-dot dash line). Paper feed rollers 207 and 208 are paper feed means for feeding paper 807 from each paper feed position.

[0017] The FPOT of the image forming apparatus in this embodiment is for an installation environment where the ambient temperature is 15° C. or higher, paper is fed from the first paper feed unit 816, and for example, A4 size (length 297 mm) with a basis weight of 80 g / m 2 Assume that the time is 7 seconds when using paper of this size. The transport speed of the paper 807 is 150 mm / sec, the width of the fixing nip 810 is 10 mm, and the distance from the fixing nip 810 to the paper discharge port 815 is 50 mm. In order to properly fix the unfixed image to the paper 807 in an environment with an ambient temperature of 15 degrees, the fixing heater 811 needs to be heated to, for example, 200°C by the time the pre-fixing heating period t1 begins. The pre-fixing heating period t1 from the start of the printing operation until the paper 807 reaches the fixing nip 810 is 4.62 seconds, and since the image heating fixing device requires energy of, for example, about 3080 J, the resistance value of the fixing heater 811 is set to 15 Ω.

[0018] 3 is a diagram showing the transport distance from each paper feed unit to the fixing nip 810. As shown in FIG. 3, the transport distance of paper from the paper feed unit to the fixing nip 810 varies depending on the paper feed position of the paper feed unit. Specifically, the transport distance from the paper feed position of paper 807 stored in third paper feed unit 202 to the fixing nip 810 is longer than the transport distance from the paper feed position of paper 807 stored in the second paper feed unit to the fixing nip 810. Furthermore, the transport distance from the paper feed position of paper 807 stored in second paper feed unit 201 to the fixing nip 810 is longer than the transport distance from the paper feed position of paper 807 stored in first paper feed unit 816 to the fixing nip 810.

[0019] The period t1, which is the period for heating the fixing device before performing the fixing process on the paper fed from the first paper feed unit, cannot be shortened because the laser scanner 803 is started, a toner image is formed, etc. As a result, as shown in Figure 3, there is a difference in the pre-fixing heating period depending on the difference in the conveyance distance from each paper feed unit to the fixing nip 810 and the conveyance speed.

[0020] 4 is a diagram showing the relationship between the pre-fixing heating period tx for each paper feed unit and the maximum energization duty of the triac 901 required to supply the 3080 J to the fixing heater 811 during each pre-fixing heating period tx. The longer the conveyance distance to the fixing nip 810, the longer the pre-fixing heating period tx, and therefore the lower the required maximum energization duty for the fixing heater 811.

[0021] Fig. 1 is a flowchart for setting the maximum current duty per unit time. Each step shown in the flowchart in Fig. 1 is executed by the CPU 802. The CPU 802 also executes each step of the flowchart in Fig. 1 by executing a program read from a ROM (not shown) and loaded into a RAM.

[0022] When the image forming apparatus starts a printing operation, the CPU 802 determines in S11 and S12 whether the paper feed unit for paper 807 is the first paper feed unit 816, the second paper feed unit 201, or the third paper feed unit 202. The paper feed unit to be used is selected based on information about the size and basis weight of the paper to be used. Based on the determination results in S11 and S12, the CPU 802 sets the maximum power-on duty per unit time of the triac 901 during the pre-fixing heating period in S13 to S15. Specifically, if the paper feed unit is the first paper feed unit 816, the maximum power-on duty is set to 100%. If the paper feed unit is the second paper feed unit 201, the maximum power-on duty is set to 90%. If the paper feed unit is the third paper feed unit 202, the maximum power-on duty is set to 81%. After completing the settings in S13 to S15, the CPU 802 starts temperature control of the fixing heater 811 in S16. This sets a limit on the maximum power supply duty per unit time that is applied only during the heating period before fixing. Upon completion of the printing operation, the temperature adjustment control of the fixing heater 811 ends in S17.

[0023] FIG. 5 shows the temperature gradient of the fixing heater 811 during the pre-fixing heating period, resulting from the control described above. As shown in FIG. 5, the temperature rise varies depending on the paper feeder. The longer the paper feeder transport distance of the paper 807 from the paper feeder to the fixing nip 810, the slower the temperature rise. For example, in a printing operation in which paper 807 is fed from the first paper feeder 816, the target temperature of 200°C is reached at t1=4.62 seconds during the pre-fixing heating period. In contrast, in a printing operation in which paper 807 is fed from the third paper feeder 202, the target temperature of 200°C is reached at t3=5.69 seconds during the pre-fixing heating period. As a result, without using the control shown in FIG. 1, the temperature maintenance period of the image fixing device, which is required for the waiting period (t3-t1) for the paper 807 to reach the fixing nip 810 after the fixing heater 811 reaches its target temperature during a printing operation from the third paper feeder 202, is not required.

[0024] In the first embodiment, the control for varying the maximum power supply per unit time to the fixing heater 811 depending on the paper feed position has been described. According to this control, by changing the maximum power supply duty to be used during the pre-fixing heating period to the fixing heater 811 depending on the paper feed position of the paper 807, it is possible to raise the fixing heater 811 to a target temperature by the time the paper 807 reaches the fixing nip 810, while suppressing excess power consumption.

[0025] In the first embodiment, the minimum unit of energization to the fixing heater 811 is phase control according to the phase angle of the commercial power source 902. However, similar control can also be performed using wave number control in which the minimum control unit is a half-wave unit of the commercial power source 902. For example, if the energization control cycle is 15 half-waves of the commercial power source 902, the maximum number of energization half-waves per energization control cycle is set to 15 half-waves if the paper feed unit is the first paper feed unit 816, 14 half-waves if the paper feed unit is the second paper feed unit 201, and 13 half-waves if the paper feed unit is the third paper feed unit 202. As a result, the fixing heater 811 can be heated to a target temperature by the time the paper 807 reaches the fixing nip 810, while excess power consumption can be suppressed.

[0026] In the first embodiment, the maximum power supply duty during the pre-fixing heating period is set before power is supplied to the fixing heater 811. However, the same effect can be obtained by setting the maximum power supply duty after power supply control to the fixing heater 811 is started, rather than before power supply is started.

[0027] Furthermore, in the first embodiment, the paper feed positions are three paper feed units, namely, the first paper feed unit 816, the second paper feed unit 201, and the third paper feed unit 202, but any configuration having a plurality of paper feed units may be used.

[0028] In the first embodiment, the maximum current duty used is set when the initial temperature of the fixing heater 811 is 15° C. However, the maximum current duty used may be appropriately corrected depending on the difference between the initial temperature of the fixing heater 811 at the start of the printing operation and the target temperature. [Example]

[0029] In the first embodiment, the maximum power-on duty for the fixing heater 811 during the pre-fixing heating period is set based only on the paper feed position of the paper 807. However, the effective value of the commercial power supply voltage to which the image forming apparatus is connected varies depending on the country of sale. Therefore, the resistance value of the fixing heater 811 with respect to FPOT can be optimized depending on the country of sale to set the optimal power input to the image heating and fixing device.

[0030] However, in consideration of the product costs that would result from individual optimization, the specifications of the fixing heater 811 may be standardized between countries where the effective commercial power supply voltage is similar. For example, a fixing heater 811 with common specifications is used for products for Japan, where the effective commercial power supply voltage is 100 V, and for products for North America, where the effective commercial power supply voltage is 115 V. In this case, the resistance of the fixing heater 811 is set to 15 Ω, which satisfies FPOT at the low effective commercial power supply voltage of 100 V, as in the first embodiment. Meanwhile, the peak power that the fixing heater 811 can consume at an effective commercial power supply voltage of 100 V is approximately 667 W, whereas the peak power that the fixing heater 811 can consume at an effective commercial power supply voltage of 115 V is approximately 882 W, allowing the fixing heater 811 to reach the target temperature in a shorter time.

[0031] FIG. 6 is a diagram showing the maximum current duty required per unit time when 3080 J is supplied when the effective voltage value of the commercial power supply 902 is 100 Vac and 115 Vac. It can be seen that the maximum current duty required per unit time is more finely divided than in Example 1 by taking into account the commercial power supply voltage. FIG. 7 is a flowchart for setting the maximum current duty required to be used during the pre-fixing heating period in consideration of the voltage of the commercial power supply 902. Each step of the flowchart in FIG. 7 is executed by the CPU 802. The CPU 802 also executes each step of the flowchart in FIG. 7 by executing a program read from a ROM (not shown) and loaded into a RAM.

[0032] The voltage information of the commercial power supply 902 may be stored in the CPU 820 as effective voltage information of the shipping country when the image forming apparatus is shipped from the manufacturing factory. Alternatively, a power supply voltage detection unit for the commercial power supply 902 may be provided in the image forming apparatus. Alternatively, the user may set the effective voltage value of the commercial power supply 902 via a user interface unit provided in the image forming apparatus. When the image forming apparatus starts a printing operation, in S21 the effective voltage value of the commercial power supply 902 is confirmed. In S22 or S23, the CPU 802 sets the voltage information of the commercial power supply 902 as a. Then, in S24, the CPU 802 sets the 100 V AC voltage based on an AC voltage value of 100 V AC. 2 / a 2is set as the power supply voltage correction value b. Next, in S25 and S26, it is determined whether the paper feeder for the paper 807 is the first paper feeder 816, the second paper feeder 201, or the third paper feeder 202. Based on the result of this determination, in S27 to S29, the CPU 802 sets the maximum power supply duty per unit time of the triac 901 during the heating period before fusing. Specifically, if the paper feeder is the first paper feeder 816, 100% × power supply voltage correction value b is set. If the paper feeder is the second paper feeder 201, 90% × power supply voltage correction value b is set. If the paper feeder is the third paper feeder 202, 81% × power supply voltage correction value b is set. After completing the settings, the CPU 802 starts temperature control of the fixing heater 811 in S30. This sets the maximum power supply duty per unit time limit that is applied only during the heating period before fusing. Upon completion of the printing operation, the temperature control of the fixing heater 811 ends in S31.

[0033] In the second embodiment, the control for varying the maximum power supply per unit time to the fixing heater 811 depending on the paper feed position has been described. That is, the maximum power-on duty used during the pre-fixing heating period to the fixing heater 811 is changed depending on the paper feed position of the paper 807, depending on the transport of the paper 807 from the paper feed unit to the fixing nip 810 and the effective value of the power supply voltage of the commercial power source 902. As a result, it is possible to set further usage conditions that can raise the fixing heater 811 to a target temperature while suppressing excess power consumption by the time the paper 807 reaches the fixing nip 810.

[0034] The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and having one or more processors in the computer of the system or device read and execute the program. It can also be realized by a circuit (e.g., ASIC) that realizes one or more functions. [Explanation of symbols]

[0035] 201 Second paper feed section 202 Third paper feed section 801 Photosensitive drum 803 Laser Scanner 804 Developing roller 806 Transfer roller 808 Fixing film 809 Pressure Roller 810 Fixing nip 811 Fixing heater 812 Stay 813 Reinforcing members 814 Thermistor 816 First paper feed section 820 CPU 901 Triac 902 Commercial power supply 904 Phototriac coupler 909 Resistance

Claims

1. a fixing device including a cylindrical fixing film, a fixing heater disposed in an internal space of the fixing film and generating heat by energization from a commercial power source, and a pressure roller, wherein a paper sheet on which a toner image has been formed is sandwiched and conveyed through a fixing nip formed by the fixing film and the pressure roller, thereby fixing the toner image to the paper sheet; a control unit for controlling the power supplied from the commercial power source to the fixing heater; a plurality of paper feed units that feed paper toward the fixing nip; a conveyance distance of the sheet from the sheet feeding position of each of the plurality of sheet feeding units to the fixing nip differs for each of the sheet feeding units; The control means sets the maximum supply power that can be supplied to the fixing heater per unit time to a first value when using a first paper feed unit among the multiple paper feed units, where the paper transport distance from the paper feed position to the fixing nip is a first transport distance, and limits the maximum supply power to a second value lower than the first value when using a second paper feed unit among the multiple paper feed units, where the paper transport distance from the paper feed position to the fixing nip is a second transport distance that is longer than the first transport distance.

2. 2. The image forming apparatus according to claim 1, wherein the control means varies the maximum supply power during a period in which the fixing heater is heated from the start of a printing operation until the first sheet of paper reaches the fixing nip.

3. 3. The image forming apparatus according to claim 1, wherein the control of the power supply to the fixing heater by the control means is phase control.

4. 3. The image forming apparatus according to claim 1, wherein the control means controls the power supply to the fixing heater by wave number control, with a power supply control period consisting of a plurality of half waves of the commercial power supply.

5. 2. The image forming apparatus according to claim 1, further comprising a voltage detection unit that detects voltage information of the commercial power source, and the control means varies the maximum supply power based on the paper feed unit used when performing a printing operation and the voltage information.

6. The image forming apparatus of claim 1, characterized in that the multiple paper feed sections include a first paper feed section and a second paper feed section connected below the first paper feed section, and the paper transport distance from the paper feed position of the paper stored in the second paper feed section to the fixing nip is longer than the paper transport distance from the paper feed position of the paper stored in the first paper feed section to the fixing nip.

7. 2. The image forming apparatus according to claim 1, wherein the fixing film is sandwiched between the fixing heater and the pressure roller, and the toner image formed on the paper is heated through the fixing film in the fixing nip.

8. a transfer unit that transfers a toner image onto the paper fed from the plurality of paper feed units; a conveying unit that conveys the paper fed from the paper feeding unit toward the transfer unit and the fixing device; The image forming apparatus according to claim 1 , further comprising:

Images