JP2005043438A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus of which the inside is efficiently dehumidified in a short time, in which the power consumption is always prevented from exceeding a rated value, and the time required to reach a standby state that allows image formation is comparatively short. <P>SOLUTION: The image forming apparatus includes: a fixing heater 4 which heats a fixing roller; a dehumidifying heater 5 which dehumidifies the inside of the apparatus; a humidity sensor 9 which detects the humidity of the inside of the apparatus; and a control means 11 which controls the supply of power to each of the heaters 4 and 5. The control means 11 controls the supply of power to the fixing heater 4 such that when the detection output of the humidity sensor 9 is not lower than a reference value when a power source is turned on, the supply of power to the fixing heater 4 is stopped and the dehumidifying heater 5 is continuously supplied with power, and when the detection output of the humidity sensor 9 is lower than the reference value, the supply of power to the dehumidifying heater 5 is limited. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile, and more particularly to a technique for efficiently operating a dehumidifying heater provided in the apparatus.
[Prior art]
A conventional image forming apparatus, for example, a copying machine, transfers a paper feed tray for storing paper, a photosensitive drum for forming a toner image visualized in accordance with an electrostatic latent image, and the photosensitive drum to the paper. And a fixing roller for thermally fixing the toner image.
The fixing roller includes a fixing heater such as a halogen lamp for heat fixing. In particular, this fixing heater consumes a large amount of power because it is necessary to heat the surface temperature of the fixing roller to about 200 ° C. in order to thermally fix the toner.
By the way, in the copying machine as described above, when the power is turned on, the interior of the apparatus is substantially the same as the external environment, and when the external humidity is high, the internal humidity is also high. There are many cases. For this reason, paper, toner, and the like absorb moisture, causing problems such as deterioration in transfer performance.
For example, when copying is started using moisture-absorbing paper, the electrostatic latent image on the photosensitive drum cannot be transferred to the paper well, and the paper is wrinkled when heated and pressed by the fixing roller. Smooth conveyance is not possible, causing problems such as paper jams.
As a countermeasure for this, conventionally, a dehumidifying heater is appropriately provided in the paper feed tray or the like, and the dehumidifying heater is energized and heated to perform dehumidification (see, for example, Patent Documents 1 and 2).
As energization control of the dehumidifying heater in this case, (1) the energization of the dehumidifying heater is started as soon as the power is turned on, or (2) a humidity sensor is provided in the vicinity of the paper feed tray in the machine. The dehumidifying heater is energized when the detection output of the sensor exceeds a preset reference level. In both cases (1) and (2), the fixing heater needs to be temporarily raised to the fixing set temperature after the power is turned on to enter a standby state. Regardless of whether the power is turned on, energization is started immediately.
Note that the above-described Patent Document 1 discloses a technique for energizing and heating a dehumidifying heater when the in-machine temperature is lower than a reference value in the state of shifting to the standby mode because the copying operation is not performed for a long time. In addition, Patent Document 2 discloses a technique for energizing and heating the dehumidifying heater when the fixing heater is turned off in the energy saving mode.
[Patent Document 1]
JP-A-8-225169 [Patent Document 2]
JP 2003-58025 A [Problems to be solved by the invention]
As described above, the energization control of the fixing heater and the dehumidifying heater is not related to each other, and the energization to the fixing heater is performed immediately after the power is turned on. If the dehumidifying heater is continuously energized, or if the dehumidifying heater is immediately energized immediately after the power is turned on in the case of (2) above, the heaters will be in a state of simultaneous use. As a result, the amount of power consumption increases and exceeds the rated value.
Therefore, in the conventional technology, even when the inside of the machine after power-on is in a high humidity state, the energization to the dehumidifying heater is unconditionally stopped when the energization control to the fixing heater is performed in order to enter the standby state. Or, when the inside of the machine after the power is turned on is in a high humidity state, measures are taken by suppressing the power supply amount to the dehumidifying heater as much as possible so as not to interfere with the energization control to the fixing heater. .
However, such a countermeasure requires a considerable amount of time from when the power is turned on until the paper is sufficiently dehumidified, and cannot easily reach the standby state. When it becomes sufficient, it still causes problems such as poor transfer and paper jams.
However, the above-mentioned Patent Documents 1 and 2 clearly state the technology for controlling the energization of the fixing heater and the dehumidifying heater at the initial stage from the power-on to the transition to the standby state. Not.
The present invention has been made in order to solve the above-described problems. When energization control of the fixing heater and the dehumidifying heater is performed at an initial stage from when the power is turned on until the standby state is reached, both of them are controlled according to the humidity in the apparatus. By having a certain relationship between them, the paper can be efficiently dehumidified in a short time, effectively preventing the occurrence of transfer defects and paper jams, and the power consumption always exceeds the rated value. It is another object of the present invention to provide an image forming apparatus in which the time required to reach a standby state in which image formation is possible is relatively short.
[Means for Solving the Problems]
The present invention adopts the following configuration in order to solve the above problems.
That is, the image forming apparatus of the present invention includes a fixing heater for heating the fixing roller, a dehumidifying heater for dehumidifying the inside of the apparatus, a humidity sensor for detecting the humidity inside the apparatus, and the humidity sensor when the power is turned on. When the detected output value is equal to or higher than a preset reference value, the dehumidifying heater is continuously energized without energizing the fixing heater, and then the detected output value of the humidity sensor is a preset reference value. Control means for limiting the power supplied to the dehumidifying heater and controlling energization of the fixing heater when the value is less than the value.
Thus, when the humidity in the apparatus is high at the initial stage of power-on, the dehumidifying heater is energized and heated in preference to the fixing heater, so that dehumidification can be efficiently performed in a short time. After the humidity inside the machine has dropped sufficiently, the power supply to the dehumidifying heater is limited and the heating control of the fixing heater is executed, so the power consumption does not always exceed the rated value and within a short time. A standby state in which image formation is possible can be reached. In addition, since the fixing heater and the dehumidifying heater are not continuously energized at the same time, a heater having a large output (power consumption) can be used as the dehumidifying heater, and the dehumidification can be performed efficiently.
Further, the control of the power supplied to the dehumidifying heater performed by the control means is performed by intermittent energization control such as half-wave control and phase control, and the energization time interval in this case depends on the detection output value of the humidity sensor. A fixed configuration may be used.
As a result, it is possible to prevent the occurrence of a problem such that the humidity inside the machine rises again and exceeds the reference value, and the temperature of the dehumidifying heater is set according to the humidity inside the machine, so the humidity inside the machine is always It is adjusted to be within the proper range. Further, by performing intermittent energization control, it is possible to reduce the power consumption of the heater, and thus it is possible to prevent the occurrence of defects such as paper transfer failure and paper jam while suppressing unnecessary power consumption.
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a case where the present invention is applied to a copying machine as an image forming apparatus will be described as an example.
FIG. 1 is a block diagram showing a main configuration of a copying machine according to an embodiment of the present invention.
In the copying machine of this embodiment, a power switch 2 that turns on / off AC power from an AC input plug 1 connected to a commercial AC power source, and AC power supplied via the power switch 2 is converted to DC. A DC power supply circuit 3 such as a DC / DC converter is provided.
A fixing roller (not shown) is provided with a fixing heater 4 made of a halogen lamp or the like, and a dehumidifying heater 5 made of a heat heater or the like is provided at the bottom of the paper feed tray (not shown). A first switch circuit 6 and a second switch circuit 7 are individually connected to the fixing heater 4 and the dehumidifying heater 5 so that the supplied AC power is turned on / off.
For the switching circuits 6 and 7, for example, switching elements such as a triac, a thyristor, and a GTO can be used, and an inverter circuit or the like can be applied instead of these switching elements.
Corresponding to the fixing heater 4, a temperature sensor 8 made of a thermistor or the like is attached in contact with the surface of the fixing roller, for example, and detects the temperature T of the fixing roller. A humidity sensor 9 for detecting the humidity M in the machine is disposed at a predetermined position in the machine, for example, a position close to the paper feed tray.
The detection outputs of the temperature sensor 8 and the humidity sensor 9 are input to a control unit 11 configured by a microcomputer or the like. The control unit 11 receives the detection output of the input sensor and the fixing setting input from the operation unit 10. The energization control of the heaters 4 and 5 is performed based on the set values of the temperature Ts and the reference value Mth for humidity control.
At this time, the control means 11 outputs the first and second gate signals Gd and Gm, thereby turning on / off the first and second switch circuits 6 and 7 to perform intermittent energization control. 5 is controlled.
Next, specific operations of energization control of the fixing heater 4 and the dehumidifying heater 5 in the copying machine having the above configuration will be described with reference to the flowchart shown in FIG. 2 and the time charts shown in FIGS.
When the power is turned on, that is, when the power switch 2 is turned on, the control means 11 is activated (S1), and the control means 11 is detected by the temperature T of the fixing roller detected by the temperature sensor 8 and the humidity sensor 9. Each data of the in-machine humidity M is taken in (S2).
Then, the value of the in-machine humidity M detected by the humidity sensor 9 is compared with a preset reference value Mth (S3). In this case, the reference value Mth is set to a value at which the humidity is such that the sheet does not cause a transfer failure or a paper jam, for example.
When the in-machine humidity M detected by the humidity sensor 9 is less than the reference value Mth, the inside of the machine is at a humidity that does not cause a transfer defect or a paper jam, and as shown in FIG. Starts energization control for raising the temperature of the fixing roller to the fixing set temperature Ts (FIG. 3: time t0).
That is, the control unit 11 always turns on the first switch circuit 6 by the output first gate signal Gd, and keeps the fixing heater 4 in a continuous energization state (S5). When the temperature T of the fixing roller detected by the temperature sensor 8 approaches the fixing set temperature Ts (a temperature lower by a predetermined temperature α than Ts, FIG. 3: time t1), the signal level of the first gate signal Gd is constant. It is changed at the period of time P1 (H / L switching), and the first switch circuit 6 is switched to intermittent energization control in which ON / OFF is repeated, and the fixing roller temperature T is maintained at the fixing set temperature Ts (S6 and S7).
Further, the control means 11 repeats on / off of the second switch circuit 7 at regular time intervals P2 by the second gate signal Gm, thereby performing intermittent energization control of the dehumidifying heater 5. As a result, it is possible to prevent the in-machine humidity M from rising and exceeding the reference value Mth after the apparatus is started, and to maintain the in-machine humidity in a low humidity state at all times.
The timing for starting such intermittent energization control of the dehumidifying heater 5 is not particularly limited, but in the present embodiment, priority is given to the temperature increase of the fixing roller while the fixing heater 4 is in the continuous energization state. Therefore, the intermittent energization control of the dehumidifying heater 5 is started at the stage of shifting to the intermittent energization control of the fixing heater 4 (time t1).
On the other hand, when the in-machine humidity M detected by the humidity sensor 9 is equal to or higher than the reference value Mth, the inside of the machine is at a humidity that causes a transfer defect or a paper jam, and as shown in FIG. The control means 11 turns off the first switch circuit 6 according to the first gate signal Gd to turn off the fixing heater 4, and always turns on the second switch circuit 7 according to the second gate signal Gm. Is continuously energized (FIG. 4: time t0) (S4).
Thus, while the dehumidifying heater 5 is continuously energized, the in-machine humidity M is compared with the reference value Mth at a predetermined time interval, and if the in-machine humidity M falls below the reference value Mth (FIG. 4: At time t2), the control means 11 always turns on the first switch circuit 6 by the first gate signal Gd to keep the fixing heater 4 in a continuous energization state (S5). Then, when the temperature T of the fixing roller approaches the fixing setting temperature Ts (a temperature lower by a predetermined temperature α than Ts, FIG. 4: time t3), the fixing is performed by switching to intermittent energization control that repeats on / off at a period of a predetermined time P1. The heater 4 is maintained at the fixing set temperature Ts.
At this time, the control means 11 keeps the second switch circuit 7 constant by the second gate signal Gm at the stage of shifting to the intermittent energization control of the fixing heater 4 (time t ₃ ) as in the example of FIG. The intermittent energization control of the dehumidifying heater 5 is performed by repeating ON / OFF at every time interval P2.
As described above, in the present embodiment, when the in-machine humidity M is higher than the reference value Mth at the initial stage of power-on, the dehumidifying heater 5 is energized and heated in preference to the fixing heater 4, so In addition, the internal humidity can be efficiently dehumidified, for example, to such an extent that the paper does not cause transfer failure or paper jam. After the in-machine humidity M drops below the reference value Mth, the power supplied to the dehumidifying heater 5 is limited and the energization control of the fixing heater 4 is executed, so that the power consumption of the apparatus always exceeds the rated value. In addition, it is possible to reach a standby state in which an image can be formed in a short time after the power is turned on.
Further, by performing intermittent energization control, it is possible to reduce the power consumption of the heater, and thus it is possible to reliably prevent problems such as transfer defects and paper jams while suppressing unnecessary power consumption.
In addition, since the fixing heater and dehumidifying heater are not continuously energized at the same time, a heater with higher output (power consumption) can be used as a dehumidifying heater than in the past, and dehumidification can be performed efficiently. Become.
Regarding the above embodiment, the following modifications and application examples can be considered.
(1) In the above embodiment, as shown in FIG. 4, after the dehumidifying heater 5 is continuously energized for the first time, the in-machine humidity M becomes less than the reference value Mth, and the process proceeds to energization control of the fixing heater 4. The dehumidifying heater 5 is intermittently energized at a later stage (after time t3). However, if the humidity in the apparatus can be kept low by the heat of the fixing heater 4, the intermittent energizing control of the dehumidifying heater 5 is not performed. It is also possible to completely stop energization.
(2) In the above embodiment, after the time t3 in FIG. 4, the dehumidifying heater 5 is controlled to be intermittently energized at a constant time interval P2, but this time interval P2 is fixed. Instead, the time interval P2 can be varied according to the level of the in-machine humidity M detected by the humidity sensor 9.
As a result, the temperature of the dehumidifying heater 5 is controlled according to the in-machine humidity M, so that the in-machine humidity M is always adjusted to be within the appropriate range. Accordingly, it is possible to prevent the occurrence of defects such as transfer failure and paper jam while suppressing wasteful power consumption.
(3) In order to reliably prevent transfer failure and paper jam, it is preferable to provide the humidity sensor 9 to detect the actual in-machine humidity M. However, the present invention is not limited to this. During the set predetermined time, the energization to the fixing heater 4 is stopped and the dehumidifying heater 5 is continuously energized. After a certain period of time, the energization control of the fixing heater 4 is performed and the dehumidifying heater 5 is energized. Can be stopped or the dehumidifying heater 5 can be intermittently energized. In this case, the same effect as the above embodiment can be obtained.
(4) In this embodiment, the case where the present invention is applied to a copying machine as an image forming apparatus has been described as an example. However, the present invention is not limited to such a copying machine, and other printers, facsimiles, and the like. Of course, the present invention can also be applied to an image forming apparatus.
【The invention's effect】
According to the present invention, when the in-machine humidity is high at the beginning of power-on, the dehumidifying heater is energized and heated in preference to the fixing heater, so that transfer failure and paper jam do not occur within a short time. Can be efficiently dehumidified. In addition, after the humidity in the machine has dropped sufficiently, the power supply to the dehumidifying heater is limited and the heating control of the fixing heater is executed, so the power consumption does not always exceed the rated value, A standby state in which an image can be formed can be reached within a short time. In addition, since the fixing heater and the dehumidifying heater are not continuously energized at the same time, a heater having a large output (power consumption) can be used as the dehumidifying heater, and the dehumidification can be performed efficiently.
Further, by limiting the power supplied to the dehumidifying heater by intermittent energization control, it is possible to reliably prevent the occurrence of a problem such that the in-machine humidity rises again and exceeds the reference value.
Furthermore, since the temperature of the dehumidifying heater is controlled according to the humidity inside the machine, the humidity inside the machine is always adjusted to be within the appropriate range. Further, by performing intermittent energization control, the power consumption of the heater can be reduced, so that it is possible to reliably prevent the occurrence of defects such as transfer failure and paper jam while suppressing unnecessary power consumption.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a main configuration of a copying machine according to an embodiment of the present invention.
FIG. 2 is a flowchart for explaining operation of energization control of a fixing heater and a dehumidifying heater of the copier.
FIG. 3 is a timing chart for explaining an operation when the in-machine humidity at power-on is less than a reference value.
FIG. 4 is a timing chart for explaining the operation when the in-machine humidity at the time of power-on is equal to or higher than a reference value.
[Explanation of symbols]
4 Fixing heater 5 Dehumidifying heater 6 First switch circuit 7 Second switch circuit 8 Temperature sensor 9 Humidity sensor 11 Control means

Claims (4)

In an image forming apparatus provided with a fixing heater for heating a fixing roller and a dehumidifying heater for dehumidifying the inside of the machine,
A humidity sensor that detects the humidity inside the machine,
When the detection output value of the humidity sensor is equal to or higher than a preset reference value when the power is turned on, the dehumidification heater is continuously energized without energizing the fixing heater, and then the detection output value of the humidity sensor Control means for restricting the power supplied to the dehumidifying heater and controlling energization of the fixing heater when the value becomes less than a preset reference value;
An image forming apparatus comprising: The image forming apparatus according to claim 1, wherein the control unit limits power supplied to the dehumidifying heater by intermittent energization control. The image forming apparatus according to claim 2, wherein the control unit changes an energization time interval of the intermittent energization control according to a detection output value of the humidity sensor. In an image forming apparatus provided with a fixing heater for heating a fixing roller and a dehumidifying heater for dehumidifying the inside of the machine,
The dehumidifying heater is continuously energized without energizing the fixing heater within a predetermined time after the power is turned on, and the power supply to the dehumidifying heater is limited and the energizing control of the fixing heater is performed after the predetermined time has elapsed. An image forming apparatus comprising a control unit.

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