Image formation control device

Abstract

To provide an image formation device that detects the moisture state of paper, corrects a fixing temperature adjustment temperature, and appropriately controls the fixing temperature so as to reduce power consumption.SOLUTION: The present image formation device comprises: a fixing unit for causing a toner to be fixed to a recording medium; a temperature detection unit capable of detecting the temperature of the fixing unit; and a control unit capable of controlling the electric power supplied for heating the fixing unit in accordance with the detection result of the temperature detection unit. The control unit determines that the recording medium is dehumidified when the gradient of the temperature detected by the temperature detection unit is below a first threshold, and the electric power supplied for heating the fixing unit is reduced by the control unit and printing is continued at a first fixing target temperature. The control unit determines that the recording medium is wet when the gradient of the temperature detected by the temperature detection unit exceeds the first threshold, and the fixing temperature is controlled so as to supply electric power so that a second fixing target temperature higher than the first fixing target temperature is achieved and continue with printing.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to fixing temperature control of an image forming apparatus. [Background technology]

[0002] In recent years, there has been an increasing demand for reducing the power consumption of image forming apparatuses.

[0003] Image forming apparatuses consume a large amount of power for transporting paper and controlling the temperature for fixing toner onto recording materials.

[0004] Most of the power consumed during printing is consumed by the fixing unit, and fixing temperature control is carried out taking into account a margin to ensure fixability for the wide variety of media that the image forming apparatus supports.

[0005] Factors related to fixation include the dehumidification and moisture absorption states of the paper.

[0006] In some image forming apparatuses, in order to execute temperature control that allows for appropriate fixing under any condition, a large margin is provided for the power supply during printing.

[0007] However, due to the current situation, there is a demand to reduce the power consumption of devices, and it is therefore desirable to print optimally while reducing power consumption as much as possible.

[0008] For example, as disclosed in Japanese Patent Application No. 10-59883, a means is known which detects the dehumidified and hygroscopic states of paper by providing a moisture absorption detection means for detecting humidity in a paper storage device. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Patent Application No. 10-59883 Summary of the Invention [Problem to be solved by the invention]

[0010] In order to ensure proper fixability regardless of the moisture absorption state of the recording material, the image forming apparatus supplies power so as to satisfy fixability in a moisture absorption state where the required amount of heat is large. Therefore, when the recording material is dehumidified, the image forming apparatus may supply more power than the minimum required amount of power during fixing.

[0011] An object of the present invention is to provide an image forming apparatus that can appropriately control the power consumption of the fixing unit based on the moisture absorption state of the recording material, and can reduce power consumption when printing on dehumidified recording material. [Means for solving the problem]

[0012] In order to achieve the above-mentioned object, the image forming apparatus of the present invention comprises a fixing unit that fixes toner onto a recording material, a temperature detection unit that can detect the temperature of the fixing unit, and a control unit that can control the power supplied to heat the fixing unit in accordance with the detection result of the temperature detection unit, and when the temperature gradient detected by the temperature detection unit is below a first threshold value, the control unit determines that the recording material has been dehumidified, and reduces the power supplied to heat the fixing unit by the control unit to continue printing at a first fixing target temperature, and when the temperature gradient detected by the temperature detection unit is above the first threshold value, the control unit determines that the recording material has absorbed moisture, and controls the fixing temperature by supplying power to achieve a second fixing target temperature higher than the first fixing target temperature so as to continue printing. Effect of the Invention

[0013] According to the present invention, when temperature control of the fixing unit is performed using the means described in the claims, the power consumption of the fixing unit can be appropriately controlled depending on the moisture absorption state of the recording material, and power consumption can be reduced when printing on dehumidified recording material. [Brief description of the drawings]

[0014] [Figure 1] 2 is a flowchart of the present invention. [Diagram 2] FIG. 1 is a block diagram of the present invention. [Diagram 3] 1 is a graph showing the state of dehumidification and the state of moisture absorption according to the present invention. [Figure 4] 13 is a flowchart in the case where a plurality of thresholds are set. [Diagram 5] FIG. 13 is an enlarged view of a graph showing the state of moisture absorption. [Figure 6] FIG. 13 is an enlarged view of a graph diagram in the case of having a plurality of thresholds. [Figure 7] FIG. 13 is a diagram showing an example of temperature detection and temperature regulation control by feedback control. [Figure 8] FIG. 4 is a diagram showing the relationship between temperature adjustment control by feedback and fixing temperature. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The following describes an embodiment of the present invention with reference to the accompanying drawings. It should be noted 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. EXAMPLES

[0016] The image forming apparatus (121) of the present invention will be described with reference to FIG.

[0017] In the image forming apparatus (121), a paper feed unit (119) feeds paper from a paper storage device (118) in which paper is loaded, and the control unit (104) detects the outside temperature and humidity using an environmental sensor (106), and then drives a drive motor (108) and a fixing motor (107) to transport the paper.

[0018] In the transfer unit (113), toner of an image corresponding to the document to be printed is transferred onto the paper from the drum (116) operated by the drive motor (108), and the paper is transported to the fixing unit (109).

[0019] The paper and the carried toner transported to the fixing unit (109) are conveyed while being pressurized by a pressure roller (110) in contact with a heated fixing heater (111) and a fixing film (112) in the fixing unit (109), thereby fixing the toner to the paper.

[0020] The fixing heater (111) is disposed at a position where the fixing film (112) and the pressure roller (110) contact each other.

[0021] Thereafter, the paper on which the toner has been fixed is discharged to a paper discharge section (120).

[0022] When the fixing heater (111) is heated, the temperature of the fixing unit is generally controlled as follows.

[0023] The power supply to the fixing heater (111) is performed by precisely controlling the energy of the current from a commercial power source using a triac or the like.

[0024] It is desirable to control the energy so that the contact area between the paper and the fixing film (112) is at a constant temperature.

[0025] The amount of heat required to maintain a constant temperature varies depending on the basis weight / moisture absorption state of the paper, the current temperatures of the pressure roller (110) / fixing film (112) / fixing heater (111), the nip pressure / position unevenness of the pressure roller (110), etc.

[0026] For this reason, an optimal target temperature for the fixing heater (111) is set for each print based on information such as the environmental temperature, the time elapsed since the last print, and the paper basis weight setting, and a temperature detection unit (122) attached near the fixing heater (111) is monitored. Energy control is performed by finely changing the power duty so that the optimal amount of heat can always be supplied while referring to the deviation from the target, integral value, and differential value through feedback control.

[0027] The temperature detection unit 122 detects the temperature using, for example, a thermistor.

[0028] The feedback control is corrected based on the results of the following calculations, for example.

[0029] The control unit (104) determines whether the temperature detection result is higher than the target temperature, and increments or decrements the determination number counter value depending on whether the temperature is higher or lower.

[0030] If the thermistor temperature is greater than the target temperature, the counter is incremented by +1, and if the thermistor temperature is less than the target temperature, the counter is incremented by -1.

[0031] If the increase or decrease in the counter in a specified period exceeds +6, the energy control is corrected to decrease the power by 2.5%, and if it falls below -6, the energy control is corrected to increase the power by 2.5%. This controls the thermistor temperature to approach the target temperature.

[0032] When the power is increased or decreased by feedback correction, the counter is cleared to 0.

[0033] The above feedback correction means that the power is increased or decreased by 2.5% when the relationship between the target temperature and thermistor temperature becomes biased to either the positive or negative side.

[0034] When one cycle during which temperature control is performed is defined as a temperature control period, temperature control is performed based on the AC zero crossing as the starting point of the cycle.

[0035] The point where the AC waveform of a commercial power source becomes 0V is called the zero crossing, and at this point, the period from one zero crossing of the sine wave to the next zero crossing is considered one half-wave.

[0036] For example, when the AC is 50 Hz, one half-wave is 10 ms, so 140 ms for 14 half-waves, and the temperature adjustment control unit is a section of 140 ms. The control unit (104) controls the ON / OFF of each half-wave at a timing determined in advance every 14 half-waves, and repeatedly executes power control.

[0037] For example, the section that is the first period in which temperature adjustment control is performed is defined as A1.

[0038] The control unit (104) determines a target temperature for performing fixing control before the A1 section.

[0039] Thereafter, in the section A1, the magnitude relationship between the temperature detection result and the target temperature is judged and stored in the counter value of the predetermined number of times.

[0040] After that, in the A2 section, the energy control method for the A3 section, specifically, the control method for each of the 14 half waves, is determined based on the result of the counter for the predetermined number of times in A1.

[0041] Based on the result of this determination, power supply / non-power supply is controlled in the A3 section at each AC zero crossing.

[0042] Figure 7 shows an example of temperature detection and temperature control using feedback control.

[0043] Definition of An: A section in which a specific temperature control is performed. The sections following An are denoted as An+1, An+2, etc.

[0044] If the Nth period of the temperature adjustment control is defined as An, the control unit (104) determines a target temperature for fixing control before the An period and performs feedback control as follows.

[0045] In the An interval, the magnitude relationship between the temperature detection result and the target temperature is judged and stored in the counter value the predetermined number of times.

[0046] After that, in the An+1 section, the energy control method for the An+2 section, for example the control method for each half wave of 14 half waves, is determined based on the result of the counter for the predetermined number of times for An.

[0047] Based on the result of this determination, in the An+2 section, energization / non-energization is controlled in units of AC zero crossings to heat the fixing heater (111).

[0048] At this time, a lag occurs in the time during which feedback works from the detection result of the temperature detection unit (122) to the actual temperature control due to the convenience of calculation processing and the unit of temperature control.

[0049] At this time, feedback correction is not possible for the first one or two cycles of temperature control at start-up because the temperature detection results from the two cycles prior are not available. However, since 100% power is input during start-up temperature control, control is performed without feedback.

[0050] Next, when the paper passes through the fixing unit (109) during the printing operation, heat from the fixing film (112) and the pressure roller (110) is transmitted to the paper, and the temperature of the fixing film (112) drops, causing the temperature of the temperature detection unit (122) installed near the fixing heater (111) to decrease.

[0051] At this time, the temperature of the temperature detection unit (122) decreases regardless of whether the paper is in a hygroscopic or dehumidified state. However, if the paper is in a hygroscopic state, the amount of heat removed is large, so the temperature decrease is large, whereas if the paper is in a dehumidified state, the amount of heat removed is small, so the temperature decrease is small.

[0052] During the period when the feedback lag occurs, the amount of decrease in temperature at the temperature detection unit (122) varies depending on the amount of moisture contained in the paper, so it is possible to detect the moisture absorption state of the paper from the detection result.

[0053] As a method for detecting the moisture absorption state of paper other than the above, for example, as disclosed in JP 10-59883 A, a humidity sensor can be provided in the paper storage device (118) to predict the humidity state of the stored paper.

[0054] However, there is a problem that a space is required to install the humidity sensor in the paper storage device (118), and a signal line is also required to transmit the detection signal to the control unit (104).

[0055] The present invention is an invention that detects the dehumidification state of paper by referring to the temperature change of the temperature detection unit (122) without using a humidity sensor in the paper storage device (118) and without adding a signal line.

[0056] The detection method of the present invention is as follows.

[0057] To determine whether the paper is in a moisture-absorbing or moisture-removing state, it is detected whether the gradient of the temperature of the temperature detection unit (122) from when the temperature of the temperature detection unit (122) starts to drop until the feedback of temperature adjustment starts is equal to or lower than a predetermined threshold value.

[0058] At this time, the temperature gradient of the temperature detection part (122) is shown in FIG. 3 and an enlarged view in FIG.

[0059] Before the control is performed, a target temperature T for adjusting the fixing temperature, a threshold value D0 of the temperature gradient for determining the dehumidification state, and a correction temperature are set in the control unit (104) as parameters based on the paper size, paper type, printing information, and environmental temperature according to the configuration of the image forming device (121).

[0060] Then, when printing is performed under the paper conditions for the first sheet of the print job, the gradient D of the temperature change is detected and compared with a threshold D0 of the gradient of the temperature for determination.

[0061] Figure 8 shows the relationship between feedback temperature control and fixing temperature.

[0062] The symbols in Figure 8 are defined below.

[0063] t1: The period from when the paper starts passing through the fixing unit (109) and the temperature of the temperature detection unit (122) starts to decrease until the temperature of the temperature detection unit (122) starts to increase due to feedback control of the temperature adjustment. d: Temperature difference of the temperature detection unit (122) in the section t1 D: The gradient of the temperature change of the temperature detection unit (122) in the section t1 D=d / t1 (Equation 1) D0: Threshold D0 of the temperature gradient to determine whether the device is in a dehumidifying or absorbing state At this time, the temperature adjustment control interval is set to 140 ms, as in FIG.

[0064] When the paper enters the fixing unit (109), the temperature of the temperature detection unit (122) drops in the section An of the Nth cycle, so that feedback control is performed to adjust the temperature to a target temperature.

[0065] However, as mentioned above, there is a lag in the time when the feedback works, so it is not until the N+2th cycle that the temperature actually starts to rise, and because temperature control is performed in the An+2 section, there is a section t1 where there is a lag in the feedback for actually correcting the controlled temperature (at this time, the temperature control in the Nth cycle and the N+1th cycle is performed based on the temperature detection results in the N-2th cycle and the N-1th cycle, respectively). The time required for feedback varies depending on the feedback processing time, the temperature propagation time of the temperature detection unit (122), and the like.

[0066] Feedback processing time: The time taken for the control unit (104) to perform calculation processing of the temperature detection result Propagation time: The time it takes for the temperature to propagate from the fixing heater (111) to the temperature detection unit (122) At this time, t1 is longer than the time required for feedback and differs depending on the image forming apparatus, so t1 is set individually.

[0067] If the gradient D of the temperature change of the temperature detection unit (122) is less than the temperature gradient threshold D0 for determining the dehumidified state, it is determined that the dehumidified state exists because almost no heat has been removed from the fixing unit (109), and the target temperature of the second and subsequent sheets of paper is lowered by the correction temperature for printing.

[0068] If the gradient D of the temperature change of the temperature detection unit (122) is equal to or greater than the gradient threshold value D0, it is determined that the fixing unit (109) is in a hygroscopic state in which a lot of heat has been absorbed, and no correction is performed. The second and subsequent sheets of paper are printed at the target temperature for the first sheet, which is higher than the target temperature for the dehumidified state. A case where the above control is carried out will be described using a concrete numerical example.

[0069] ·Target temperature T: 200℃ Slope threshold D0: 2℃ / 500ms (dehumidification state is determined when slope D is less than 2℃ / 500ms) (A gradient D of 2°C / 500 ms or more indicates moisture absorption.) Slope interval t1: 500 ms.

[0070] Case 1 (1) Start printing with the target temperature for the first sheet set to 200°C. (2) When feedback started, the temperature drop of the temperature detection unit (122) was 1°C, and the temperature gradient D was 1°C / 500 ms. (3) Because the threshold value D0: 2°C / 500 ms > 1°C / 500 ms, the system is determined to be in a dehumidifying state. The target temperature for the second sheet onwards is lowered by 5°C as a correction temperature, and printing is performed with 200-5=195°C as the new target temperature.

[0071] Case 2 (1) Start printing with the target temperature for the first sheet set to 200°C. (2) When feedback started, the temperature drop of the temperature detection unit (122) was 3°C, and the temperature gradient D was 3°C / 500 ms. (3) Because the threshold value D0 is 2°C / 500 ms≦3°C / 500 ms, it is determined that the sample is in a moisture-absorbed state. (4) For the second and subsequent sheets, no correction temperature is applied to the target temperature, and printing is performed at 200°C, which is higher than the dehumidified state.

[0072] As described above, the target temperature is corrected and printing is performed.

[0073] By controlling as described above, the target temperature of the dehumidified paper is set low, so that the power consumed by the fixing unit (109) can be reduced.

[0074] Next, the flow chart shown in FIG. 1 will be described.

[0075] In S1001, a print job is started.

[0076] In S1002, the target temperature for printing the first sheet is determined from the job contents (paper size, paper type, print information, and environmental temperature), a first threshold value D0 that is the threshold value for the temperature gradient is determined, and temperature adjustment is started.

[0077] In S1003, the toner is controlled to be fixed to the recording material in the fixing unit at the target temperature.

[0078] In S1004, in order to detect the temperature gradient of the fixing unit (109), the point when the temperature of the temperature detection unit (122) starts to drop is set as the start point of the gradient, and the point when the temperature rises due to feedback control is set as the end point of the gradient, and a temperature gradient D is calculated from the elapsed time and the change in temperature (at this time, the interval for calculating the temperature gradient D may be defined as a predetermined time t1). In S1005, if the temperature gradient D detected in S1004 is less than the first threshold value D0, it is determined to be in a dehumidifying state and the process proceeds to S1006, and if it is equal to or greater than the first threshold value, it is determined to be in a hygroscopic state and the process proceeds to S1007.

[0079] In S1006, since it is determined that the dehumidified state is present, the target temperature of the fixing unit (109) is lowered to the first fixing target temperature.

[0080] In S1007, since the moisture absorption state exists, the target temperature is not changed.

[0081] In S1008, the second and subsequent pages of the print job are printed at the target temperatures determined in S1006 and S1007.

[0082] In S1009, the print job ends. EXAMPLES

[0083] A control in the case where a plurality of threshold values ​​are used to determine the dehumidification state from the gradient of the temperature detected by the temperature detector (122) will be described.

[0084] The main control is the same as in Figure 1, but the judgment based on the temperature gradient can be subdivided to improve the accuracy of correction. Figure 6 shows a graph with multiple thresholds.

[0085] As an example, FIG. 4 shows a flowchart for implementing control using three thresholds to determine the dehumidification state and moisture absorption state in four stages (the first to third thresholds described in the flowchart of FIG. 4 are set so that the first threshold D1<second threshold D2<third threshold D3).

[0086] In S2001, a print job is started.

[0087] In S2002, the target temperature for the first sheet is determined from the job contents (paper size, paper type, printing information, and ambient temperature), and the first threshold D1, second threshold D2, and third threshold D3, which serve as thresholds for the temperature gradient, are determined from parameters previously set in the control unit, and temperature adjustment is started.

[0088] In S2003, the toner is controlled to be fixed to the recording material in the fixing unit at the target temperature.

[0089] In S2004, in order to detect the temperature gradient of the fixing unit (109), the point when the temperature of the temperature detection unit (122) starts to drop is set as the start point of the gradient, and the point when the temperature rises due to feedback control is set as the end point of the gradient, and a temperature gradient D is calculated from the elapsed time and the change in temperature (at this time, the interval for calculating the temperature gradient D may be defined as a predetermined time t1). In S2005, if the temperature gradient D detected in S2004 is less than the first threshold D1, it is determined that the dehumidification state is established and the process proceeds to S2006, and if it is equal to or greater than the first threshold D1, the process proceeds to S2007 for a second determination.

[0090] In S2006, since the dehumidification state is 1, the target temperature of the fixing unit (109) is lowered to the first fixing target temperature.

[0091] In S2007, a second threshold D2 is set, which is a temperature gradient larger than the first threshold D1 determined in S2005. If the temperature gradient D detected by the temperature detection unit (122) is less than the second threshold D2, the dehumidification state 2 is determined and the process proceeds to S2007. If the temperature gradient D is equal to or greater than the second threshold D2, the process proceeds to S2008 for a third determination.

[0092] In S2008, since the dehumidification state is 2, the target temperature of the fixing unit (109) is lowered to the second fixing target temperature.

[0093] In S2009, a third threshold D3 is set, which is a temperature gradient larger than the second threshold D2 determined in S2007. If the temperature gradient D detected by the temperature detection unit (122) is less than the third threshold D3, it is determined to be in the dehumidification state 3 and the process proceeds to S2010. If the temperature gradient D is equal to or greater than the third threshold D3, it is determined to be in the moisture absorption state and the process proceeds to S2011.

[0094] In S2010, since the dehumidification state is 3, the target temperature of the fixing unit (109) is lowered to the third fixing target temperature.

[0095] In S2011, since the moisture absorption state occurs, the target temperature is not changed.

[0096] In S2012, the second and subsequent print jobs are printed at the target temperatures determined in S2006, S2008, S2010, and S2011.

[0097] In S2013, the print job ends.

[0098] This completes the explanation of the flowchart.

[0099] By the above control, the target temperature of the dehumidified paper can be set stepwise for each threshold value, and the power consumed by the fixing unit (109) can be appropriately reduced depending on the state of the paper. [Explanation of symbols]

[0100] 104 Control section 106 Environmental Sensor 107 Fixing motor 108 Drive motor 109 Fixing part 110 Pressure roller 111 Fixing heater 112 Fixing film 113 Transcription section 116 Drums 118 Paper storage device 119 Paper feed section 120 Paper output section 121 Image forming device 122 Temperature detection unit

Claims

1. In an image forming apparatus, a fixing unit that fixes the toner onto the recording material; a temperature detection unit capable of detecting a temperature of the fixing unit; a control unit capable of controlling power supplied to heat the fixing unit in accordance with a detection result of the temperature detection unit; When the gradient of the temperature detected by the temperature detection unit falls below a first threshold value, the control unit determines that the recording material is dehumidified, and reduces the power supplied to heat the fixing unit by the control unit to continue printing at the first fixing target temperature; When the temperature gradient detected by the temperature detection unit exceeds a first threshold value, the control unit determines that the recording material has absorbed moisture, and controls the fixing temperature by supplying power to achieve a second fixing target temperature that is higher than the first fixing target temperature, thereby controlling the fixing temperature to continue printing.

2. The first threshold value described in claim 1 may have two or more threshold values, such as a second threshold value and a third threshold value, and an image forming apparatus having a fixing target temperature corresponding to each of the threshold values ​​and a configuration in which the fixing target temperature can be set based on the detection result of a temperature detection unit.

3. 2. The image forming apparatus according to claim 1, wherein the temperature detecting section detects the temperature again when the recording material storage device is opened or closed.

4. 2. The image forming apparatus according to claim 1, wherein the temperature detection unit executes detection again after a predetermined time has elapsed.

5. 2. The image forming apparatus according to claim 1, wherein when the environmental temperature changes by a predetermined temperature or more, the temperature detecting section detects the temperature again.

6. 2. An image forming apparatus according to claim 1, wherein the threshold value is changed depending on the printing rate and color or monochrome state of the image, and detection is performed by the temperature detection unit.

7. 2. An image forming apparatus according to claim 1, wherein the temperature detection unit detects the temperature by changing a threshold value depending on a size or a type of the recording material.

8. 2. The image forming apparatus according to claim 1, wherein the temperature detection unit changes the threshold value depending on the environmental temperature.

9. 2. The image forming apparatus according to claim 1, wherein if the section for determining the temperature gradient exceeds a predetermined time, it is determined that an error has occurred, and the target temperature is not changed.

10. 2. The image forming apparatus according to claim 1, wherein when a temperature gradient of a predetermined temperature or more is detected in a section for obtaining a temperature gradient in the control of claim 1, an error is determined, and the target temperature is not changed.

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