Image forming apparatus

Abstract

To perform temperature adjustment control for fixing temperature while reducing power consumption.SOLUTION: An image forming apparatus 121 comprises: a fuser 109 that heats a sheet to fix an image to the sheet; control means 104 that detects the amount of power supplied to the fuser 109, and on the basis of a rate of change per predetermined time of a power integrated value obtained by integrating the detected amount of power, determines a target fixing temperature when the fuser 109 heats the sheet; and a power supply control unit 103 that controls the amount of power supplied to the fuser 109 on the basis of the target fixing temperature.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to adjustment and control of the fixing temperature of an image forming apparatus having a fixing unit that heats paper to fix an image. [Background technology]

[0002] In recent years, there has been an increasing demand for reducing the power consumption of image forming devices. Image forming devices consume a large amount of power to adjust the fixing temperature of the fixing unit that fixes toner onto paper. To maintain fixability for a wide variety of paper types and printing conditions, image forming devices adjust and control the fixing temperature according to the type of paper and printing conditions. One factor related to fixability is the amount of moisture contained in the paper.

[0003] In order to ensure proper fixation in an image forming apparatus, a target fixing temperature is set so that poor fixing does not occur even when the paper is wet, and the fixing temperature is adjusted accordingly. Patent Document 1 discloses a technology for detecting the amount of moisture (hygroscopicity) contained in the paper and feeding it back to temperature adjustment control to appropriately adjust the fixing temperature. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-255361 Summary of the Invention [Problem to be solved by the invention]

[0005] Paper that contains a large amount of moisture (high moisture absorption) requires a large amount of heat to ensure fixability, so the target fixing temperature is set high. This means that the image forming device supplies a lot of power to the fixing unit. Furthermore, if the moisture absorption of the paper is determined and fed back to the temperature adjustment control of the fixing temperature, a sensor that detects the moisture absorption must be placed near the paper. This requires the image forming device to secure space for the sensor. Furthermore, the additional parts increase costs.

[0006] In view of the above-mentioned problems, the main object of the present invention is to provide an image forming apparatus that can perform temperature adjustment control of the fixing temperature while suppressing power consumption without providing additional components such as a sensor for detecting moisture absorption. [Means for solving the problem]

[0007] The image forming apparatus of the present invention is characterized by comprising a fixing means for fixing an image onto paper by heating, a determining means for detecting the amount of power supplied to the fixing means and determining a target fixing temperature when the fixing means heats the paper based on the rate of change per predetermined time of an integrated power value obtained by integrating the detected amount of power, and a power supply control means for controlling the amount of power supplied to the fixing means based on the target fixing temperature. [Effects of the Invention]

[0008] According to the present invention, it is possible to perform temperature adjustment control of the fixing temperature while suppressing power consumption without providing any additional components. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating the configuration of an image forming apparatus. [Figure 2] FIG. 4 is an explanatory diagram of temperature adjustment control of the fixing temperature. [Figure 3] 10 is a flowchart showing a printing process. DETAILED DESCRIPTION OF THE INVENTION

[0010] Preferred embodiments of the present invention will be described in detail below with reference to the drawings. Note that unless otherwise specified, the dimensions, materials, shapes, and relative positions of the components are not intended to limit the scope of the present invention.

[0011] 1 is a diagram illustrating the configuration of an image forming apparatus according to this embodiment. Image forming apparatus 121 includes a paper storage device 118 that stores paper. Image forming apparatus 121 forms an image on paper fed from paper storage device 118. Paper storage device 118 includes a paper feed unit 119 that feeds paper.

[0012] The image forming apparatus 121 includes a transfer unit 113 having a photosensitive drum 116, and a fuser 109 having a fixing film 112 and a pressure roller 110, in order to form an image on paper. The photosensitive drum 116 is driven to rotate by a drive motor 108. A toner image is formed on the photosensitive drum 116. The toner image is transferred from the photosensitive drum 116 to the paper fed by a paper feed unit 119 by the transfer unit 113. The paper onto which the toner image has been transferred is transported to the fuser 109 by the rotation of the photosensitive drum 116.

[0013] In the fuser 109, the pressure roller 110 is rotated by the fuser motor 107. The fuser film 112 has a fuser heater 111 and a temperature detection unit 122 inside. The fuser 109 sandwiches and conveys the paper onto which the toner image has been transferred between the fuser film 112 and the pressure roller 110. At this time, the fuser film 112 heats the toner image with the fuser heater 111. The pressure roller 110 is biased toward the fuser film 112 and presses the paper. As a result, the toner image on the paper is melted by heating, and is pressed onto the paper by pressure. In this way, the image is fixed to the paper. The paper with the fixed image is discharged to the paper discharge unit 120 by the rotation of the pressure roller 110.

[0014] The image forming apparatus 121 includes a control unit 104 for controlling the operation of each of the built-in components. In this embodiment, the temperature adjustment control of the fixing temperature of the fixing unit 109 by the control unit 104 will be described, but the control unit 104 can also control the overall operation of the image forming apparatus 121. The control unit 104 includes a calculation unit 102. The control unit 104 is connected to the fixing motor 107 and drive motor 108, and controls the operations of the fixing motor 107 and drive motor 108. In addition, the control unit 104 is connected to an environmental sensor 106 and a power supply control unit 103. The environmental sensor 106 is used to detect the environmental temperature and humidity of the installation environment of the image forming apparatus 121.

[0015] The power supply control unit 103 includes a power detection unit 105. Power is supplied to the power supply control unit 103 from the commercial power supply 101. The power supply control unit 103 generates power of a predetermined voltage value from the supplied power for operating each component in the image forming apparatus 121. The power supply control unit 103 supplies the generated power to each component in the image forming apparatus 121. In this embodiment, the power supply control unit 103 supplies the power supplied from the commercial power supply 101 to a fixing heater 111 of the fixing unit 109. The fixing heater 111 generates heat using the power supplied from the power supply control unit 103.

[0016] The temperature adjustment control of the fixing temperature by the image forming apparatus 121 configured as described above will now be described. As described above, the power supply control unit 103 supplies power supplied from the commercial power supply 101 to the fixing heater 111 under the control of the control unit 104, thereby causing the fixing heater 111 to generate heat. The power supply control unit 103 precisely controls the amount of power supplied to the fixing heater 111, thereby performing precise temperature adjustment control so that the fixing temperature of the fixing unit 109 reaches the target fixing temperature.

[0017] It is preferable to adjust the temperature so as to maintain a constant temperature at the contact point between the paper and the fixing film 112. The amount of heat required to maintain a constant fixing temperature constantly changes depending on the paper size, paper type, moisture absorption, the current temperatures of the pressure roller 110, fixing film 112, and fixing heater 111, the pressure applied by the pressure roller 110, positional irregularities of the pressure roller 110, etc.

[0018] To achieve this, the control unit 104 sets an optimal target fixing temperature for each print job based on the type of paper, the ambient temperature, the warm-up state inside the machine, etc. The control unit 104 monitors the fixing temperature detection results from the temperature detection unit 122 located near the fixing heater 111, and adjusts the temperature to the optimal fixing temperature by feedback control while referring to the deviation from the target fixing temperature, the integral value, and the differential value. The temperature detection unit 122 can be, for example, a temperature sensor such as a thermistor.

[0019] The control unit 104 determines whether the fixing temperature detected by the temperature detection unit 122 is higher than the target fixing temperature, and updates a determination counter according to the determination result. For example, the control unit 104 increments the determination counter by 1 when the fixing temperature detected by the temperature detection unit 122 is higher than the target fixing temperature, and decrements the determination counter by 1 when the fixing temperature is lower. When the value of the determination counter becomes larger or smaller than a predetermined value, the control unit 104 performs temperature adjustment control so that the fixing temperature approaches the target fixing temperature.

[0020] For example, if the value of the determination counter exceeds "+6," the control unit 104 controls the power supply control unit 103 to reduce the amount of power supplied to the fixing heater 111 by a predetermined amount, for example, 2.5%. When the value of the determination counter becomes larger than the predetermined value in the positive direction, this means that the detection result of the fixing temperature continues to be higher than the target fixing temperature. Therefore, the control unit 104 reduces the amount of power supplied to the fixing heater 111 to lower the fixing temperature.

[0021] Conversely, if the value of the determination counter falls below "-6," the control unit 104 controls the power supply control unit 103 to increase the amount of power supplied to the fixing heater 111 by a predetermined amount, for example, 2.5%. If the value of the determination counter becomes larger than the predetermined value in the negative direction, this means that the detection result of the fixing temperature continues to be lower than the target fixing temperature. Therefore, the control unit 104 increases the amount of power supplied to the fixing heater 111, thereby raising the fixing temperature.

[0022] In this way, feedback control of the fixing temperature is performed based on the detection result of the temperature detection unit 122. When the amount of power supplied to the fixing heater 111 is adjusted by feedback control, the control unit 104 clears the determination counter to 0. In this way, feedback control adjusts the amount of power supplied when the relationship between the target fixing temperature and the detection result of the fixing temperature by the temperature detection unit 122 is biased to either the positive or negative side.

[0023] When paper passes through the fuser 109 during printing, heat is transferred from the fuser film 112 to the paper. This causes the fuser film 112 to cool. This causes the fuser temperature detected by the temperature detection unit 122 to drop. At this time, the fuser temperature detected by the temperature detection unit 122 drops regardless of the amount of moisture (hygroscopicity) contained in the paper. When the paper is in a hygroscopic state where the moisture absorption is higher than a predetermined value, the amount of heat removed by the fuser film 112 increases, causing the fuser temperature to drop. When the paper is in a dehumidified state where the moisture absorption is lower than in a hygroscopic state, the amount of heat removed by the fuser film 112 decreases, causing the fuser temperature to drop less than in a hygroscopic state.

[0024] As a result, the power consumption required to maintain the target fixing temperature for hygroscopic paper increases, and the slope of the integrated value of the amount of power supplied to the fixing unit 109 (integrated power value) increases. Conversely, the power consumption required to maintain the target fixing temperature for dehumidified paper decreases compared to hygroscopic paper, and the slope of the integrated power value decreases. In this embodiment, the slope of the integrated power value is used to determine the moisture content of the paper, making it possible to determine the moisture absorption of the paper without adding a sensor or the like.

[0025] 2 is an explanatory diagram of temperature adjustment control of the fixing temperature. The amount of power supplied to the fixing unit 109 is calculated by the calculation unit 102 based on the voltage supplied to the fixing unit 109 detected by the power detection unit 105 provided in the power supply control unit 103 and the current passed through the fixing unit 109. The calculation unit 102 can calculate the slope A of the integrated power value by recording the time t during continuous printing on multiple sheets of paper and the integrated power value f(t) at that time. The slope A of the integrated power value represents the rate of change of the amount of power per specified time.

[0026] When printing the first sheet immediately after starting printing, the amount of power supplied to the fixing unit 109 fluctuates greatly, making it difficult to detect the slope of a stable integrated power value f(t). For this reason, in this embodiment, the integrated power value is detected in a section where the amount of power supplied to the fixing unit 109 fluctuates little when printing a predetermined number of sheets from the second sheet onwards. Specifically, the calculation unit 102 detects the integrated power value by integrating the amount of power supplied to the fixing unit 109 when printing the second through fourth sheets. The calculation unit 102 calculates the slope A of the integrated power value based on the detected integrated power value.

[0027] For this purpose, the calculation unit 102 saves time t1, when printing of the second sheet begins, which marks the start of the time Δt, and the integrated power value f(t1) at that time, and saves time t2, when printing of the fourth sheet ends, which marks the end of the time Δt, and the integrated power value f(t2) at that time. The calculation unit 102 calculates the slope A of the integrated power value using these saved values. In this embodiment, the slope A of the integrated power value is calculated based on the amount of fluctuation in the amount of power (integrated power value) integrated over the printing time (time Δt) of the second to fourth sheets, but the time Δt is set depending on the device configuration, specifications, etc. Therefore, the time Δt (integrated time) is not limited to this.

[0028] The gradient A of the integrated power value is calculated, for example, by the following formula: Note that the gradient A of the integrated power value may be derived, instead of using the following formula, for example, by using a table showing the relationship between the time Δt and the integrated power value f(t). A = (f(t2) - f(t1)) / (t2 - t1) ... (Equation 1) f(t): Integrated power value f(t) = At ​​+ B t: time A: Slope of the integrated power value B: Intercept t1: Start time of judging the slope of the power integration value (start time of printing the second page) t2: End time of power integration slope judgment (start time of printing the fourth page)

[0029] The target fixing temperature T during temperature adjustment control is set according to the operating conditions of image forming apparatus 121 during printing (paper size, paper type, print information, ambient temperature, internal warm-up state, etc.). The target fixing temperature when printing the first sheet is set to first target fixing temperature T1, and the target fixing temperatures for correction are set to second target fixing temperature T2 and third target fixing temperature T3. The first target fixing temperature T1 is a target fixing temperature at which fixing can be performed on hygroscopic paper. The second target fixing temperature T2 is a target fixing temperature at which fixing can be performed on normal paper. The third target fixing temperature T3 is a target fixing temperature at which fixing can be performed on dehumidified paper. The magnitude relationship between the first to third target fixing temperatures T1, T2, and T3 is such that the first target fixing temperature T1 is the highest and the third target fixing temperature T3 is the lowest. T1>T2>T3

[0030] The target fixing temperature T is set to the first target fixing temperature T1 when printing the first sheet and when detecting the slope of the integrated power consumption value for the second to fourth sheets. The target fixing temperature T for the fifth sheet and thereafter is determined to be one of the first to third target fixing temperatures T1, T2, or T3 using the method described below. The moisture absorption of the paper is determined by comparing the slope A of the integrated power consumption value obtained by (Equation 1) with first and second thresholds A1 and A2 obtained from the operating conditions of the image forming apparatus 121 (paper size, paper type, print information, ambient temperature, and internal warm-up state). The first threshold A1 is a threshold for determining whether the paper is in a moisture-absorbing state. The second threshold A2 is a threshold for determining whether the paper is in a dehumidified state. The second threshold A2 is a value smaller than the first threshold A1. First threshold A1: A1=C×X1+D×Y1+E×Z1 ... (Equation 2) Second threshold A2:A2=C×X2+D×Y2+E×Z2…(Formula 3) (A1>A2) C: Table value for each paper type when printing (Define the predetermined values ​​for each paper size (A3, A4, LTR, etc.) and paper type (thin paper, thick paper, etc.) D: Predetermined value for each environmental temperature during printing (define predetermined values ​​for each temperature, such as 15°C, 25°C, etc.) E: Predetermined value for each internal warm-up state during printing (The warm-up state is defined as a coefficient based on the previous print job information and the time elapsed since printing.) X1: Coefficient for the type of paper when it is in a moisture-absorbed state Y1: Coefficient for the ambient temperature when hygroscopic Z1: Coefficient for the hygroscopic state of the cabin when the air is warm X2: Coefficient for paper type in dehumidified state Y2: Coefficient for dehumidified conditions relative to the ambient temperature Z2: Coefficient for dehumidification in the interior warm-up state The values ​​of C, D, E, X1, Y1, Z1, X2, Y2, and Z2 are determined in advance depending on the image forming apparatus 121 and the state at the time of printing.

[0031] To determine the moisture absorption of the paper, the gradient A of the power integrated value is compared with first and second threshold values ​​A1 and A2 of the gradient for determination. If the comparison result shows that the gradient A of the integrated power value is equal to or greater than the first threshold A1 (A≧A1), it is determined that the paper is in a moisture-absorbed state because a large amount of heat has been absorbed from the fixing device 109. In this case, printing continues without changing the first target fixing temperature T1. If the gradient A of the integrated power value is between the first threshold A1 and the second threshold A2 (A1>A≧A2), the paper is determined to be in an intermediate state (normal state) between the moisture-absorbing state and the dehumidifying state because some heat has been removed from the fixing unit 109. In this case, the target fixing temperature T is subsequently lowered to the second target fixing temperature T2 and printing is performed. If the gradient A of the integrated power value is less than the second threshold A2 (A2>A), it is determined that the paper is in a dehumidified state because not much heat has been removed from the fixing device 109. In this case, the target fixing temperature T thereafter is lowered to the third target fixing temperature T3 and printing is performed.

[0032] 3 is a flowchart showing a printing process including adjustment of the fixing temperature of the fixing unit 109. This process is executed in response to a print job that instructs continuous printing of multiple sheets. The print job is input from a user interface provided in the image forming apparatus 121 or an external device such as a server connected to the image forming apparatus 121.

[0033] When the control unit 104 acquires a print job, it sets first and second threshold values ​​A1 and A2 for the slope of the integrated power value based on the operating conditions (paper size, paper type, print information, ambient temperature, internal warm-up state, model, content of the previous print job, and time elapsed since the previous print process) (S1001). The paper size, paper type, and print information are identified from the content of the print job. The ambient temperature is acquired from the detection result by the environmental sensor 106. The internal warm-up state, model, content of the previous print job, and time elapsed since the previous print process are stored in the memory of the image forming device 121.

[0034] The control unit 104 starts accumulating the amount of power supplied to the fixing unit 109 (S1002). The control unit 104 sets the target fixing temperature T to a first target fixing temperature T1 (S1003). The control unit 104 performs printing processing for the first sheet (S1004, S1005). The fixing temperature during printing processing for the first sheet is adjusted to be the first target fixing temperature T1.

[0035] The control unit 104 records the time t1 when printing of the second sheet starts and the integrated power consumption value f(t1) at that time in the memory built in the calculation unit 102, and starts printing processing of the second sheet (S1006, S1007). Thereafter, the control unit 104 performs printing processing up to the fourth sheet. When printing processing of the fourth sheet is completed, the control unit 104 records the time t2 at that time and the integrated power consumption value f(t2) at that time in the memory of the calculation unit 102 (S1008).

[0036] The control unit 104 calculates the slope A of the power accumulation value based on the time Δt (= t2 - t1) between the printing processes of the second to fourth sheets and the difference (f(t2) - f(t1)) between the power accumulation values ​​f(t1) and f(t2) (S1009).

[0037] The control unit 104 determines whether the calculated slope A of the integrated power consumption is equal to or greater than the first threshold A1 (S1010). If the slope A of the integrated power consumption is equal to or greater than the first threshold A1 (S1010: Y), the control unit 104 determines that the paper is in a moisture-absorbed state. In this case, the control unit 104 determines that the target fixing temperature T is not updated, and that the printing process will continue at the first target fixing temperature T1 (S1011).

[0038] If the slope A of the integrated power consumption value is less than the first threshold value A1 (S1010: N), the control unit 104 determines whether the slope A of the integrated power consumption value is equal to or greater than the second threshold value A2 (S1012). If the slope A of the integrated power consumption value is equal to or greater than the second threshold value A2 (S1012: Y), the control unit 104 determines that the paper is in a normal state. In this case, the control unit 104 lowers the target fixing temperature T from the first target fixing temperature T1 to the second target fixing temperature T2, and determines to continue the print process (S1013).

[0039] If the slope A of the power integration value is less than the second threshold A2 (S1012: N), the control unit 104 determines that the paper is in a dehumidified state. In this case, the control unit 104 lowers the target fixing temperature T from the first target fixing temperature T1 to a third target fixing temperature T3, and determines to continue the printing process (S1014).

[0040] The control unit 104 executes the printing process for the fifth and subsequent sheets (S1015) while adjusting the fixing temperature to the target fixing temperature T set in the process of S1011, S1013, or S1014. When printing on the number of sheets specified in the print job is completed, the control unit 104 ends the printing process.

[0041] Through the above process, the target fixing temperature is adjusted according to the moisture absorption of the paper. Specifically, the target fixing temperature T is set to the highest first target fixing temperature T1 at the beginning of continuous printing. Thereafter, the target fixing temperature T is reset based on the moisture absorption of the paper. The target fixing temperature T is maintained at the first target fixing temperature T1 when the paper is in a moisture-absorbing state (the slope of the integrated power value is equal to or greater than the first threshold). The target fixing temperature T is lowered to the second target fixing temperature T2 when the paper is in a normal state (the slope of the integrated power value is less than the first threshold and equal to or greater than the second threshold). The target fixing temperature T is lowered to the third target fixing temperature T3 when the paper is in a dehumidified state (the slope of the integrated power value is less than the second threshold). This type of control makes it possible to reduce power consumption while appropriately adjusting the target fixing temperature.

[0042] In this embodiment, there is no need to provide a humidity detector such as a humidity sensor inside the image forming apparatus 121 as in the past. Therefore, no space is required for providing a humidity detector. Furthermore, there is no need to add a signal line for transmitting a detection signal from the temperature detector to the control unit 104. In this embodiment, the moisture absorption of paper can be detected based on the slope A of the power integrated value without using a temperature detector or adding a signal line. In this way, the image forming apparatus 121 of this embodiment enables optimal power control without providing a separate device for detecting the state of paper, thereby reducing power consumption.

[0043] When multiple print jobs are executed consecutively, each printing multiple sheets, and the paper storage device 118 is not opened or closed and the printing is performed on the same paper type, the state of the fixing unit 109 can be maintained and the subsequent print job can be performed. In this case, the target fixing temperature T set in the previous print job is used for the subsequent print job from the first printed sheet onwards. In this process, the fixing temperature is adjusted to the optimum target fixing temperature from the first printed sheet onwards.

Claims

1. a fixing means for fixing the image on the paper by heating; a determining means for determining a target fixing temperature when the fixing means heats the paper based on a rate of change per predetermined time of an integrated power value obtained by integrating the detected amount of power supplied to the fixing means; and a power supply control unit that controls the amount of power supplied to the fixing unit based on the target fixing temperature. Image forming device.

2. the determining means determines the target fixing temperature to be a first target fixing temperature, which is the highest, when the rate of change is equal to or greater than a first threshold value, and determines the target fixing temperature to be a second target fixing temperature, which is lower than the first target fixing temperature, when the rate of change is less than the first threshold value.

2. The image forming apparatus according to claim 1.

3. the determining unit determines the target fixing temperature to be a third target fixing temperature lower than the second target fixing temperature when the rate of change is less than a second threshold value that is smaller than the first threshold value.

3. The image forming apparatus according to claim 2.

4. further comprising an environmental sensor for detecting an environmental temperature; the determining unit sets the first threshold value and the second threshold value based on operating conditions including the type of paper on which an image is printed and the environmental temperature.

4. The image forming apparatus according to claim 3.

5. The determining unit derives the rate of change per predetermined time from an integrated power value obtained by accumulating the amount of power consumed when a print job for continuously printing a plurality of sheets is started and a predetermined number of sheets are printed from the second sheet onward.

2. The image forming apparatus according to claim 1.

6. the determining means derives the rate of change per predetermined time from the time when printing of the second sheet starts and the integrated power value at that time, and the time when printing of the predetermined number of sheets ends and the integrated power value at that time.

6. The image forming apparatus according to claim 5.

7. When a plurality of print jobs for printing a plurality of sheets are executed in succession, if the printing is performed on paper of the same paper type, the determining means uses the target fixing temperature determined in the previous print job as is when printing the first sheet of the subsequent print job.

2. The image forming apparatus according to claim 1.

8. Further, a temperature detecting means for detecting the temperature of the fixing means is provided, the power supply control means controls the amount of power supplied to the fixing means based on the temperature detection result by the temperature detection means so that the temperature of the fixing means reaches the target fixing temperature.

2. The image forming apparatus according to claim 1.

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