JP2004026394A - Image forming device - Google Patents

Abstract

An object of the present invention is to heat and dry a sheet for a predetermined time after the power is turned on when it is considered that the sheet heating means (heater) has not been energized for a certain period of time and has absorbed moisture. An object of the present invention is to provide an image forming apparatus capable of avoiding problems such as transfer failure and conveyance failure due to moisture absorption.
In order to solve the above problem, a representative configuration of an image forming apparatus according to the present invention includes a sheet storage unit that stores sheets to be fed to an image forming unit, and a sheet storage unit inside or near the sheet storage unit. And a sheet heating unit provided in the image forming apparatus, wherein a predetermined time after the energization is turned on, a temperature of the sheet heating unit, or a temperature of the sheet, The amount of electric power supplied to the heating means is controlled.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile that forms an image by an electrophotographic method.
[0002]
[Prior art]
A conventional image forming apparatus will be described with reference to FIG. FIG. 8 is an overall configuration diagram illustrating a conventional image forming apparatus, and FIG. 9 is a diagram illustrating a conventional sheet storage unit.
[0003]
The image forming apparatus shown in FIG. 8 includes, as an image forming unit, a primary charger 102 for uniformly charging the photosensitive drum 101 around a photosensitive drum 101 as an image carrier, and an electrostatic charger on the photosensitive drum 101. An exposure device 103 for forming a latent image, a developing device 104 for developing an electrostatic latent image to form a toner image, a transfer charger 105 for transferring the toner image to a sheet, and a separation charger for separating the sheet from the photosensitive drum 101 106, a cleaning device 107 for removing residual toner on the photosensitive drum 101 after transfer, and a pre-exposure lamp 108 for removing residual charges on the photosensitive drum 101.
[0004]
Feed cassettes 110, 111, and 112 as sheet storage units are provided at the lower part of the apparatus. Sheets P of different sizes stored in the respective apparatuses are selectively fed by feed rollers 113a to 113c. The sheet is conveyed to the registration roller pair 117 through the conveyance guide 116 by 115a to 115c. A manual feed tray 114 is provided on the side of the apparatus, and is fed to the registration roller pair 117 by the transport roller 119. The sheet P on which the toner image has been transferred from the photosensitive drum 101 in the transfer nip portion N is discharged outside the apparatus after the image is fixed by a fixing device 118 including a fixing roller 118a and a pressure roller 118b.
[0005]
In the place where the image forming apparatus is installed and used, environmental conditions such as temperature and humidity are variously changed depending on conditions such as a season, weather, and a cooling / heating device. Further, the sheet P in the feeding cassettes 110 to 112 also dries and absorbs moisture in accordance therewith, so that the volume resistivity and the surface resistivity of the sheet greatly change. In particular, when the sheet absorbs moisture and the resistivity is lowered, a problem of transfer failure occurs, resulting in an image failure.
[0006]
More specifically, of the total transfer current generated by the transfer charger 105, the transfer current in the drum direction (usually about 10% to 20% of the total transfer current) contributing to transfer is conveyed through the sheet P. It decreases due to leakage to the rollers 115a to 115c and the conveyance guide 116 and interference with the separation charger 106. As a result, the electrostatic force for transferring the toner image on the photosensitive drum 101 to the surface of the sheet P is weakened, and as a result, the image density is reduced, resulting in an image defect.
[0007]
Conventionally, in order to prevent the transfer failure, a heater 120 is provided inside or near the feeding cassettes 110 to 112 as shown in FIG. 9 to directly heat the sheet P or to remove air in the feeding cassette. It is widely practiced to prevent the sheet from absorbing moisture by heating or the like.
[0008]
In this case, the power supply to the heater 120 is usually designed so as to be possible regardless of the ON / OFF of the main body power supply, and a constant power is supplied as long as the power plug is in the ON state. The temperature is controlled to be constant. This prevents the sheets stored in the main body from absorbing moisture irrespective of the state of use of the main body.
[0009]
[Problems to be solved by the invention]
However, in the above-described conventional configuration, there is a case where the operation of the heater 120 is not reliable and moisture absorption of the sheet cannot be prevented. For example, not all image forming apparatuses are designed to supply power to the heater separately from the main body power supply, and there may be ones in which power supply to the main body power supply and power supply to the heater are linked from the viewpoint of power saving.
[0010]
Also, at night or on holidays when the main body is not used, the power plug may be unplugged from the viewpoint of reduction of standby power and energy saving, or to ensure safety when no user is present. In such a case, power is not necessarily supplied to the heater, so the sheet is likely to absorb moisture. Especially at nights and on holidays, the air conditioner in the room where the main body is installed is often stopped, and the humidity rises and moisture absorption is easily accelerated.
[0011]
After such a situation, by turning on the power supply of the main body or turning on the power plug, even if the power supply to the heater is started, the power of the heater is generally sufficient to prevent moisture absorption of the sheet. However, it is difficult to dry the material that has already absorbed moisture, and its effect is limited, for example, only the portion close to the heater or it takes time.
[0012]
Increasing the degree of sealing of cassettes and paper decks is very effective in preventing moisture, but it is difficult to completely seal because there are mechanical mechanisms for replenishing sheets and feeding them to the main unit. It is.
[0013]
Therefore, in the present invention, when it is considered that the sheet heating means (heater) has not been energized for a predetermined time or more and the sheet has absorbed moisture, the sheet is heated and dried for a predetermined time after the energization is turned on, thereby causing the sheet to absorb moisture. It is an object of the present invention to provide an image forming apparatus that can avoid problems such as transfer failure and conveyance failure.
[0014]
[Means for Solving the Problems]
In order to solve the above problems, a typical configuration of an image forming apparatus according to the present invention includes a sheet storage unit that stores sheets to be fed to an image forming unit, and a sheet storage unit provided inside or near the sheet storage unit. In the image forming apparatus having the sheet heating unit, the temperature of the sheet heating unit or the supply of the sheet to the sheet heating unit is determined for a predetermined time after the energization is turned on in accordance with a time period during which no power is supplied to the sheet heating unit. It is characterized by controlling the amount of power to be applied.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
[First embodiment]
A first embodiment of an image forming apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a sequence of ON / OFF control of a sheet heating unit according to the present invention, FIG. 2 is a diagram showing an entire configuration of an image forming apparatus, and FIGS. 3 and 4 are diagrams showing other control sequences of a heater. .
[0016]
(Overall configuration of image forming apparatus)
First, the overall configuration of the image forming apparatus will be described with reference to FIG. The image forming apparatus shown in the figure includes a drum-type photosensitive drum 1 (electrophotographic photosensitive member) as an image carrier, and a primary charger 2 (corona charger), an exposing device 3, a developing device 4, and a transfer device around the photosensitive drum 1. A charger 5, a separation charger 6, a cleaning device 7, and a pre-exposure lamp 8 are provided.
[0017]
In the present embodiment, the photosensitive drum 1 is a negatively charged organic photosensitive member, has a photosensitive layer (not shown) on a drum base (not shown) made of aluminum, and has a predetermined circumference in the direction of an arrow (clockwise). It is driven to rotate at a speed (process speed). The primary charger 2 uniformly charges the surface of the photosensitive drum 1 to a predetermined polarity and potential by corona ions generated by corona discharge. The exposure device 3 performs a laser beam L (image exposure) corresponding to the input image information (image signal) on the surface of the photosensitive drum 1 charged by the primary charger 2. The image exposure with the laser beam L emitted from the exposure device 3 forms an electrostatic latent image corresponding to the input image information on the surface of the photosensitive drum 1. The developing device 4 causes toner to adhere to the electrostatic latent image at a developing position by a rotatable developing sleeve 9 to visualize the electrostatic latent image as a toner image.
[0018]
Next, an image forming operation of the above-described image forming apparatus will be described.
[0019]
At the time of image formation, the photosensitive drum 1 is driven to rotate at a predetermined process speed in a direction indicated by an arrow by a driving unit (not shown), and the surface is uniformly charged to, for example, −700 V by the primary charger 2. Then, the charged photosensitive drum 1 is irradiated with a laser beam from the exposure device 3 to be provided with a laser beam L, and an electrostatic latent image is formed in accordance with image information of an input document (not shown). You. Then, toner is adhered to the electrostatic latent image by a developing sleeve 9 to which a developing bias having the same polarity as the charging polarity of the photosensitive drum 1 is applied, and is developed as a toner image.
[0020]
Then, when the toner image on the photosensitive drum 1 reaches the transfer nip portion N between the photosensitive drum 1 and the transfer charger 5, the registration rollers 17 are used to feed the feed cassettes 10, 11, 12 or manually. The sheet P selected and fed from the tray 14 is conveyed to the transfer nip N, and is transferred onto the surface of the sheet P by the transfer charger 5 to which a transfer bias having a polarity opposite to that of the toner is applied. The toner image is transferred.
[0021]
Sheets P having different sizes are stored in the feed cassettes 10, 11, and 12, respectively. The sheets P are fed one by one by feed rollers 13a, 13b, and 13c, and are transported by feed rollers 15a, 15b, and 15c. Is transported to the registration roller pair 17 through the transport guide 16. Further, sheets of any size can be stored in the manual feed tray 14, and can be conveyed to the registration roller pair 17 by the conveyance rollers 19.
[0022]
Then, the sheet P on which the toner image has been transferred at the transfer nip portion N is separated from the photosensitive drum 1 after the electrostatic attraction between the sheet P and the photosensitive drum 1 is weakened by the separation charger 6. The toner image is conveyed between the fixing roller 18a and the pressure roller 18b of the fixing device 18, and the toner image is thermally fixed on the surface of the sheet P by heating and pressing, and is discharged.
[0023]
In the case of image formation in the double-sided image formation or the multiple image formation mode, after the image formation on the first side of the sheet P is completed, the sheet P passes through the fixing device 18, and then passes from the registration roller pair 17 again through a path (not shown). The sheet is fed to the transfer nip N.
[0024]
Further, the transfer residual toner remaining on the surface of the photosensitive drum 1 after the transfer of the toner image is removed and collected by a cleaning device 7 (cleaning blade). It is removed and prepared for the next image formation.
[0025]
(Sheet heating means)
In each of the feed cassettes 10 to 12, first heaters 20a to 20c are provided as upper portions as sheet heating means, and second heaters 21a to 21c are provided around four sides. The first heater 20 and the second heater 21 are driven by being supplied with electric power by the electric power control means 22, and are controlled in temperature as described below.
[0026]
In the present embodiment, in a normal state in which the image forming apparatus is operating, only the first heater 20 is driven and is controlled to a constant temperature (for example, 50 degrees). Then, the power supply to the second heater 21 is turned on in accordance with the time during which the power supply to the first heater 20 is turned off.
[0027]
FIG. 1 shows a sequence of ON / OFF control of the sheet heating means. Assuming that the main body power is turned off (T1) and the power plug is unplugged several minutes later, the first heater 20 is also turned off at this time (T2).
[0028]
When the power plug of the main body is turned on (T3), if the first heater 20 has been turned off for 8 hours or more, it is determined that the sheet absorbs a large amount of moisture. Therefore, after the power plug of the main body and the power supply are turned on, both the first heater 20 and the second heater 21 are controlled to be turned on to promote drying in the feed cassettes 10 to 12. At this time, both the first heater 20 and the second heater 21 are controlled to a constant temperature (for example, 50 degrees). Then, after a predetermined time (for example, 2 hours) has elapsed (T4) and the drying of the sheet has progressed to some extent, the second heater 21 is turned off in a normal state, and only the first heater 20 is operated to prevent moisture absorption.
[0029]
According to the above configuration, even if the sheet is temporarily absorbed by turning off the heater for a long time, drying can be promoted after the next turn on of the heater, thereby avoiding problems such as poor transfer and poor conveyance. be able to. In addition, by using two heaters for one cassette, drying can be performed uniformly and effectively.
[0030]
Note that if the power supply to the main body and the power supply to the heater are not linked and the image forming apparatus does not affect the power supply to the heater even when the main body power supply is turned off, as shown in FIG. Regardless, the heater is energized. As long as the power plug is not turned off as in the above-described embodiment, there is no need to control the sheet heating means, and it is sufficient to always supply a constant power or control the temperature to be adjusted within a predetermined temperature range. In the case where temperature adjustment is performed, ON / OFF is actually repeated with an appropriate duty even in the portion indicated by the ON time.
[0031]
In the above example, the OFF time of the heater is assumed to be 8 hours. However, if the OFF time is as short as about 2 hours as shown in FIG. The power supply to the heater need not be strengthened. How long the heater OFF time becomes longer when the heater is turned off can be changed as appropriate.
[0032]
[Second embodiment]
A second embodiment of the image forming apparatus according to the present invention will be described with reference to the drawings. FIG. 5 is a diagram showing a sequence of ON / OFF control of the sheet heating means according to the present embodiment. Parts that are the same as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.
[0033]
In the first embodiment, the first heater 20, the second heater 21, and the two heaters are provided as the sheet heating means. However, in the present embodiment, only the first heater 20 is provided to perform predetermined control. It is.
[0034]
As shown in FIG. 5, after the first heater 20 is turned off (T2) and the power supply is restarted (T3), the temperature of the first heater 20 is reduced by 50 degrees until a predetermined time (for example, 2 hours) elapses (T4). Control is as high as> 65 degrees. Thereby, drying of the moisture-absorbed sheet can be promoted, and problems such as transfer failure and transport failure due to moisture absorption of the sheet can be avoided.
[0035]
When the first heater 20 is controlled not by the temperature but by the amount of electric power, the same effect can be obtained by increasing the average amount of electric power between T3 and T4 above the normal amount.
[0036]
[Third embodiment]
A third embodiment of the image forming apparatus according to the present invention will be described with reference to the drawings. FIG. 6 is a diagram showing a sequence of ON / OFF control of the sheet heating means according to the present embodiment. Parts that are the same as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.
[0037]
This embodiment is a combination of the first and second embodiments, and includes two sheet heating means, that is, a first heater 20 on the upper side of the feeding cassette and a second heater 21 around four sides of the feeding cassette. ing.
[0038]
As shown in FIG. 6, after the first heater 20 is turned off (T2) and the power supply is resumed (T3), the temperature of the first heater 20 is reduced by 50 degrees until a predetermined time (for example, 2 hours) elapses (T4). > 65 degrees, and also supplies power to the second heater 21 that is not normally used. Thereby, drying of the moisture-absorbed sheet can be more effectively promoted.
[0039]
[Fourth embodiment]
A fourth embodiment of the image forming apparatus according to the present invention will be described with reference to the drawings. FIG. 7 is a diagram showing a sequence of ON / OFF control of the sheet heating means according to the present embodiment. The same reference numerals are given to the same portions as those in the first embodiment, and the description will be omitted.
[0040]
In the first to third embodiments, the temperature of the sheet heating means or the amount of electric power supplied to the sheet heating means depends on the time when the electricity is not supplied to the sheet heating means, for a predetermined time after the power is turned on. Is configured to be controlled. On the other hand, the present embodiment is characterized in that the temperature of the sheet heating means or the amount of electric power supplied to the sheet heating means is controlled based on the temperature and humidity data inside or near the apparatus. In the present embodiment, description will be made using only one sheet heating unit (first heater 20).
[0041]
The image forming apparatus is provided with temperature and humidity detecting means (not shown), and is configured to be able to detect the temperature and humidity inside or near the apparatus. As shown in FIG. 7A, consider a case where the first heater 20 is turned off (T2) and the power supply is restarted (T3).
[0042]
FIG. 7B shows a case where the temperature is high while the heater is off. This is a condition that tends to occur during the night when the air-conditioning system stops or in holidays, such as in a summer office, and the sheet absorbs moisture significantly. Therefore, the temperature of the first heater 20 is controlled so as to be raised as high as 50 ° C. to 65 ° C. after the resumption of power supply (T3) until a predetermined time (for example, 2 hours) elapses (T4).
[0043]
FIG. 7C shows a case where the temperature is normal temperature and normal humidity while the heater is off. In this case, since the sheet does not absorb much moisture, the temperature is set at a normal value even after the power supply is resumed.
[0044]
FIG. 7D shows a case where the humidity was low while the heater was off. In this case, even if the heater is OFF, there is no possibility that the sheet absorbs moisture. Therefore, the sheet may be kept OFF after the power supply is resumed (T3).
[0045]
With the above configuration, the sheet absorbs moisture without consuming power by controlling the temperature of the heater or the amount of electric power supplied to the heater after re-energizing the heater by judging the degree of moisture absorption of the sheet from the temperature and humidity while the heater is off. Can be dried to an appropriate state, and transfer failure and transport failure due to moisture absorption can be prevented.
[0046]
The temperature and humidity during the heater energization OFF may be comprehensively determined by taking data at regular intervals or continuously. For example, if the humidity rises to about 70% after a transition for 10 hours in a low humidity state, the above control is strengthened after the heater power is restarted. Conversely, if the change is about 40% for 2 hours after 60% for 10 hours, control may be performed at a normal temperature.
[0047]
Further, for simplicity, if the apparatus main body is installed in an environment in which the temperature and humidity when the heater power supply is OFF do not change much with the passage of time, the determination may be made only based on the temperature and humidity conditions when the heater power supply is restarted.
[0048]
[Fifth embodiment]
A fifth embodiment of the image forming apparatus according to the present invention will be described. The same parts as those in the first embodiment will be denoted by the same reference numerals, and description thereof will be omitted. In the present embodiment, the image forming apparatus has a sheet remaining amount detecting unit (not shown) in the feeding cassettes 10 to 12 and performs control using the unit.
[0049]
In each of the above embodiments, the energization time after restarting the energization of the heater has been described as, for example, 2 hours. However, if image formation is repeated and sheets in the feed cassette are used up during this time, the feed cassette is In other words, there is no need to increase the heater power supply.
[0050]
Therefore, if the remaining amount of sheets in the feeding cassette can be detected, the control may be returned to the normal control when the remaining amount of the feeding cassette becomes zero in addition to the control in each of the above embodiments. Alternatively, for example, in the case of a cassette capable of storing a maximum of 500 sheets, the number of sheets fed from a predetermined cassette is counted regardless of the actual number of sheets stored, and the control is returned to the normal control when the number of sheets reaches 500. Good. If there is a remaining amount detecting means, the control may be returned to the normal control when the remaining amount becomes zero. Alternatively, the control may be performed according to the number of remaining sheets.
[0051]
Although the embodiments have been described above, the method of enhancing the heater energization after the start of energization may be performed by one or a combination of techniques such as increasing the temperature of a single heater and turning on a heater that is not normally used. In the present invention, the temperature of the heater, the bias condition applied to the heater, and the type of the heater are not particularly limited. It is also possible to appropriately change the time during which the power is strengthened and the number of sheets fed during that time, and appropriately set the environmental time such as the time during which power is stopped and the temperature and humidity transition inside and near the device during that time. Can be.
[0052]
【The invention's effect】
As described above, in the image forming apparatus according to the present invention, even when the sheet heating unit is not energized for a certain time or more and the sheet absorbs moisture, the power supplied to the heater for a predetermined time after the energization is turned on is more than usual. By increasing the temperature and increasing the temperature, or by turning on a heater which is normally turned off, the drying of the sheet is promoted, thereby making it possible to avoid problems such as transfer failure and conveyance failure due to moisture absorption of the sheet.
[0053]
Further, by controlling the amount of power to the heater based on one or both of the temperature and humidity data inside or near the apparatus while the power is OFF, or the temperature and humidity data at the time when the power is turned ON, the drying of the sheet can be improved. This can be performed optimally, and wasteful power consumption can be suppressed.
[0054]
In addition, by performing the above control until there is no sheet in the sheet storage unit, drying can be performed only on the sheet that has absorbed moisture in the sheet storage unit. Therefore, excessive power is supplied to the heater even after using the sheet that has absorbed moisture. This is effective in reducing power consumption and preventing temperature rise in the machine.
[Brief description of the drawings]
FIG. 1 is a diagram showing a control sequence of a sheet heating unit according to a first embodiment.
FIG. 2 is an overall configuration diagram of the image forming apparatus.
FIG. 3 is a diagram showing another control sequence of the heater.
FIG. 4 is a diagram showing another control sequence of the heater.
FIG. 5 is a diagram illustrating a control sequence of a sheet heating unit according to a second embodiment.
FIG. 6 is a diagram illustrating a control sequence of a sheet heating unit according to a third embodiment.
FIG. 7 is a diagram illustrating a control sequence of a sheet heating unit according to a fourth embodiment.
FIG. 8 is an overall configuration diagram illustrating a conventional image forming apparatus.
FIG. 9 is a diagram illustrating a conventional sheet storage unit.
[Explanation of symbols]
L: Laser beam N: Transfer nip P: Sheet 1: Photoconductor drum 2: Primary charger 3 ... Exposure device 4: Developing device 5: Transfer charger 6: Separation charger 7 ... Cleaning device 8: Pre-exposure lamp 9 Developing sleeve 10 Feeding cassette 11 Feeding cassette 12 Feeding cassette 13 Feeding roller 14 Manual feed tray 15 Transporting roller 16 Transporting guide 17 Registration roller pair 18 Fixing device 18a Fixing roller 18b Pressure roller 19 Transport roller 20 First heater 21 Second heater 22 Power control means 101 Photoconductor drum 102 Primary charger 103 Exposure device 104 Developing device 105 Transfer charger 106 Separation charger 107: Cleaning device 108: Pre-exposure lamp 1 0: feeding cassette 111: feeding cassette 112: feeding cassette 113: feeding roller 114: manual feed tray 115: conveying roller 116: conveying guide 117: registration roller pair 118: fixing device 118a: fixing roller 118b: pressure roller 119: transport roller 120: heater

Claims (8)

A sheet storage unit that stores sheets to be fed to the image forming unit,
In an image forming apparatus having a sheet heating unit provided in or near the sheet storage unit,
The temperature of the sheet heating means or the amount of electric power supplied to the sheet heating means is controlled for a predetermined time after the energization is turned on, in accordance with the time during which the electricity is not supplied to the sheet heating means. Image forming device. 2. The image according to claim 1, wherein when the power supply to the sheet heating means has not been performed for a predetermined time or more, more sheet heating means than a normal state are operated for a predetermined time after the power supply is turned on. Forming equipment. 2. The apparatus according to claim 1, wherein when the power supply to the sheet heating means is not performed for a predetermined time or more, the temperature of the sheet heating means is set higher than normal for a predetermined time after the power supply is turned on. Image forming device. If the power supply to the sheet heating means has not been performed for a certain period of time or more, the average power per unit time supplied to the sheet heating means for a predetermined time after the power supply is turned on is set to be larger than usual. The image forming apparatus according to claim 1, wherein: A sheet storage unit that stores sheets to be fed to the image forming unit,
In an image forming apparatus having a sheet heating unit provided in or near the sheet storage unit,
If the power supply to the sheet heating means has not been performed for a certain period of time or more, the temperature of the sheet heating means or the temperature of the sheet heating means is determined based on temperature / humidity data in or near the apparatus for a predetermined time after the power supply is turned on. An image forming apparatus for controlling the amount of power supplied to the means. 6. The image forming apparatus according to claim 5, wherein the temperature / humidity data is one or both of a history of a state where power is turned off and a time when the power is turned on. Having a sheet remaining amount detecting means for detecting a remaining amount of sheets stored in the sheet storing portion,
If the power supply to the sheet heating means has not been performed for a certain period of time or more, a predetermined time after the power supply is turned on, temperature and humidity data inside or near the apparatus and / or one or both of the sheet remaining amount detection means. The image forming apparatus according to claim 1, wherein a temperature of the sheet heating unit or an amount of power supplied to the sheet heating unit is controlled based on a result. If the power supply to the sheet heating unit has not been performed for a certain period of time or more, the temperature of the sheet heating unit or the sheet heating unit is not changed until the predetermined number of sheets are fed from the sheet storage unit after the power supply is turned on. The image forming apparatus according to claim 1, wherein an amount of power supplied to the unit is controlled.

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