JP4333431B2 - Paper transport device, image forming apparatus, and paper transport unit - Google Patents

Description

  The present invention relates to a sheet conveying apparatus, and more particularly to a sheet conveying apparatus having a function of preventing condensation that occurs on a sheet conveying path.

In an image forming apparatus that creates a copy using an electrophotographic method, such as an electrophotographic copying machine or a laser beam printer, after transferring a toner image onto a sheet, the sheet is fixed by passing it through a fixing device. To be discharged. In the fixing device, heat and pressure are applied through a sheet between a heating roll and a pressure roll, and the toner is melted by heat and pressed against the sheet to perform fixing. Further, the paper used in the image forming apparatus contains moisture, and when heated, the moisture contained in the paper evaporates as water vapor. For this reason, when the humidity in the air is high, the moisture content becomes particularly large, and the amount of water vapor generated from the paper increases. Further, when the number of jobs increases, the amount of water vapor generated also increases. For this reason, in a general image forming apparatus, the water vapor discharged from the fixing device causes dew condensation on the paper transport rolls in the paper transport path, which causes troubles in paper transport such as jams, skews, and unevenness of discharged paper. There's a problem.
In order to solve such problems, Patent Document 1, Patent Document 2, and Patent Document 3 have been proposed.

The proposal of Patent Document 1 is provided with a dew condensation prevention fan that operates according to temperature, the number of copies, etc. and blows air toward the fixing device, and water vapor generated from the transfer material when passing through the fixing device is a means for discharging the transfer material. It is the structure which prevents beforehand that it forms on the guide member.
Also, the proposal of Patent Document 2 is configured to energize the fixing device through an auxiliary resistor when the main switch is turned off for the purpose of shortening the start-up time of the fixing device, and this auxiliary resistor is connected to the roll paper feeding unit. It functions as a dehumidifying heater.

  Further, the proposal of Patent Document 3 arranges an exhaust fan to exhaust air containing water vapor, transfers heat of the image fixing device to the guide plate of the paper discharge path, and heats the image forming device, sorter, etc. This prevents condensation on the paper discharge path in the post-processing apparatus.

On the other hand, recent image forming apparatuses, for example, electrophotographic copying machines (so-called copying machines) are being unitized, and may be used by connecting a double-sided printing unit to a normal single-sided printing unit.
In these units, for example, a fixing unit having a fixing device is disposed in the lowermost layer, a single-sided printing unit is placed on the upper level, and a double-sided printing unit is placed on the upper level. It has been broken.

  In such a copying machine, when the paper passes through the fixing device, water vapor is generated and rises, and there is a case where dew condensation occurs on the single-sided printing unit located above and the paper conveyance roll in the double-sided printing unit. In particular, when the paper that has passed through the fixing unit is discharged from the single-sided printing unit to the outside, the paper-conveying roll in the double-sided printing unit that is not performing the paper-conveying operation is likely to cause condensation.

Japanese Patent Laid-Open No. 5-134513 Japanese Patent Laid-Open No. 10-213999 JP-A-8-211819

  However, all of the proposals in Patent Documents 1 to 3 prevent condensation and remove condensation by adding another component not related to the paper transport function. That is, it is configured to include a dew condensation prevention fan, a dehumidifying heater, an exhaust fan, and the like. These components require a space for installation, and it is not preferable to install these components from the viewpoint of miniaturization of the sheet conveying device. Also, from the viewpoint of power consumption, it is desirable that these are not installed.

Further, in the proposal of Patent Document 3 in which the heat of the fixing device is transmitted to the guide plate of the paper discharge path to be warmed to prevent condensation on the paper discharge path, the fixing unit, the single-sided printing unit, and the double-sided printing unit are sequentially installed as described above. When connected and used, it cannot be used because the fixing device in the fixing unit is separated from the paper transport roll in each printing unit.
SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to prevent dew condensation and water droplet adhesion on a sheet conveying roll in a sheet conveying path, a shaft of the sheet conveying roll, without adding special components.

In order to achieve such an object, the present invention provides a first sheet conveyance path which is a path downstream of the fixing device and is a path from the opening of the single-sided printing unit to the sheet being discharged by the discharge roll. A path downstream of the fixing unit, on which a sheet is conveyed from a first opening to a second opening on a duplex printing unit placed on the upper side of the single-sided printing unit; In the single-sided printing mode, the sheet that has been subjected to the fixing process by the fixing device is routed through the first sheet conveying path without passing through the second sheet conveying path. In the duplex printing mode, the paper that has been discharged by the discharge roll and fixed by the fixing device is routed through the second paper conveyance path by the paper conveyance roll, and is again fixed by the fixing device and discharged. A sheet conveying apparatus and a control circuit to discharge by Lumpur, wherein the control circuit, when the single-sided printing mode, a sheet conveying apparatus for causing idling the sheet conveying roll (claim 1 ).

In the sheet conveying apparatus having such a configuration, the sheet conveying roll in the second sheet conveying path normally does not rotate in the single-sided printing mode. Therefore, the present invention prevents the condensation of the paper transport roll and the shaft of the paper transport roll by causing the paper transport roll of the second paper transport path to idle in the single-sided printing mode.
In this method, the paper transport roll is idled to form an air layer around the paper transport roll and the shaft of the paper transport roll, and the water vapor that has risen by the air layer is shut out.

Moreover, such a sheet conveying apparatus, Ru can be configured to sheet transport roll is positioned at an upper portion of the first sheet transport path.

Here, the first sheet transport path and said second sheet transport path with are respectively formed on separate units, Ru can be configured to each have a separate drive source.

  That is, even in a single-sided printing unit that is unitized and has a separate drive source, a paper conveying device that is configured by connecting the double-sided printing unit, and an image forming apparatus, the paper passes through the other paper conveying path as described above. Condensation can be prevented by causing the paper transport roll on one of the paper transport paths to idle during transport.

The sheet conveying apparatus as described above can be configured to include a job number counter and a control circuit that performs control to idle the sheet conveying roll when the count value by the job number counter reaches a predetermined number. The

Condensation is caused by moisture contained in the paper that has passed through the fixing device, and there is little possibility that condensation will occur if only a few sheets are passed through the fixing device and printed. That is, when a certain number of sheets are passed through the fixing device, there is a high possibility that condensation will occur. Therefore, it is desirable to determine the number of jobs for which the sheet conveying roll starts to idle in advance and to allow the sheet conveying roll to idle when the number of jobs is reached.
The present invention rotates the paper transport roll even though the paper is not transported, and thus consumes extra power in this respect. With such a configuration, power and energy savings can be achieved. Leads to.

Furthermore, the paper conveying apparatus as described above determines whether or not the dew generation condition is satisfied based on the temperature sensor and / or the humidity sensor and the measurement value of the temperature sensor and / or the humidity sensor. Ru can be configured to have a control circuit that performs control to idle the sheet conveying roll if they become.

The occurrence of condensation depends on the surrounding environment such as temperature and humidity in the vicinity of the condensation occurrence point. Therefore, the temperature and humidity in the vicinity of the paper transport roll are measured, and it is determined whether or not the dew condensation is generated based on the measured values. Based on the determination, it is determined whether or not the paper transport roll is idled. This will lead to power and energy savings.
In addition, it is determined whether or not the dew generation condition is satisfied by taking into account the count value by the job number counter as described above and the measured values of the temperature sensor and the humidity sensor, and based on the determination, the paper transport roll is idling. If it is determined whether or not to perform, more precise control is realized, leading to energy saving.

Further, the sheet conveying device as described above, the control circuit, a sheet conveying roll during idling, may be configured to rotate slower than during paper conveyance (claim 2).

In the present invention, the sheet conveying roll is idled as described above in order to prevent water vapor from spreading around the sheet conveying roll and condensation on the sheet conveying roll and the shaft.
Therefore, the idle speed of the paper transport roll may be a speed that forms a gas layer around the paper transport roll and can shut out water vapor.
Therefore, in order to prevent dew condensation, when it is sufficient for the paper transport roll to rotate at a lower speed than the rotational speed during paper transport, the paper transport roll during idling may be configured to rotate at such a rotational speed. it can. This also saves energy. It also reduces noise during standby.

According to another aspect of the present invention, there is provided an image forming apparatus including the above-described sheet conveying device (claim 3 ). Such an image forming apparatus, Ru can be configured to sheet transport roll is positioned at an upper portion of the fixing device. In the image forming apparatus, in consideration of the efficiency of unitization and paper conveyance, a paper conveyance roll may be disposed above the fixing device. Even in the image forming apparatus having such a configuration, it is possible to efficiently prevent condensation as long as the image forming apparatus includes the sheet conveying apparatus that idles the sheet conveying roll as described above.

Furthermore, another invention of the present invention is a paper transport unit which is installed downstream of the fixing device and is connected to another paper transport unit having a first paper transport path to constitute a paper transport device, sheet transport unit, Ru paper transporting unit der characterized by having a paper transporting roll to idle when the paper is transported the first sheet transport path.

  According to the present invention, one of the two paper transport paths has the paper transport roll that idles when the paper is transported through the other paper transport path. It is possible to prevent dew condensation on the paper transport roll and shaft.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

The sheet conveying apparatus 1 of the present invention forms part of an image forming apparatus and can handle single-sided printing and double-sided printing. FIG. 1 is an explanatory diagram showing an outline of the configuration of the sheet conveying apparatus 1. The sheet conveying apparatus 1 is composed of three units, and a fixing unit 2 is stacked on the lowermost layer, a single-sided printing unit 3 is stacked thereon, and a duplex printing unit 4 is stacked thereon. The paper transport device 1 can switch between the single-sided printing mode and the double-sided printing mode, and the double-sided printing unit 4 is not used in the single-sided printing mode.
Further, the sheet transport apparatus 1 includes a control circuit 16 as shown in FIG. The control circuit 16 is connected to an inverter roll drive motor 17 that drives the inverter roll 9 shown in FIG. 1 and issues a command to the inverter roll drive motor 17.

  The fixing unit 2 includes a fixing device 5 that includes a heating roll and a pressure roll in a housing, and printing paper is supplied from a paper supply unit (not shown).

  The single-sided printing unit 3 includes a set of discharge rolls 6 that are one of paper transport rolls in the housing. The printed paper is discharged to the outside of the housing by the discharge roll 6. As shown in FIG. 1, the single-sided printing unit 3 is placed on the upper side of the fixing unit 2. The housing constituting the single-sided printing unit 3 and the housing constituting the fixing unit 2 include an opening 7 and an opening. There are two communication points. Moreover, the single-sided printing unit 3 is provided with the 1st discharge port 18, as shown in FIG.

A first paper transport path 13 is formed on the single-sided printing unit 3, and the discharge roll 6 is included in the first paper transport path 13. The discharge roll 6 has a configuration in which a cylindrical rubber roll is attached to a shaft. The discharge roll is driven by a drive motor (drive source) (not shown).
Note that the first paper conveyance path 13 is a path indicated by a dotted line in the single-sided printing unit 3 and indicates a path from the opening 7 to discharge to the outside by the discharge roll 6.

  The double-sided printing unit 4 includes a set of inverter rolls 9 and a set of discharge rolls 10 which are one of paper transport rolls in a casing. A route switching plate 15 is attached in the vicinity of the discharge roll 10. As shown in FIG. 1, the duplex printing unit 4 is placed on the upper side of the simplex printing unit 3, and the casing that constitutes the duplex printing unit 4 and the casing that constitutes the simplex printing unit 3 include an opening 11. The two openings 12 communicate with each other. The duplex printing unit 4 includes a second outlet 19 as shown in FIG.

A second paper transport path 14 is formed on the duplex printing unit 4, and the second paper transport path 14 includes an inverter roll 9 and a discharge roll 10. The inverter roll 9 and the discharge roll 10 have a configuration in which a cylindrical rubber roll is attached to a shaft. The inverter roll 9 is driven by a drive motor (drive source) 17 and the discharge roll 10 is driven by a drive motor (drive source) (not shown).
As shown in FIG. 1, the inverter roll 9 is positioned immediately above the fixing unit 5 so that the sheet printed on one side by the fixing unit 5 can be sucked into the duplex printing unit 4.
The second paper conveyance path 14 is indicated by a one-dot chain line among the paper conveyance paths in the double-sided printing mode, which will be described in detail later, and indicates the one existing on the double-sided printing unit 4.

Here, the paper conveyance path of the paper conveyance device 1 will be described.
First, the paper conveyance path in the single-sided printing mode will be described. The sheet conveyance path in the single-sided printing mode is a path indicated by a dotted line in FIG. That is, the paper supplied from the paper supply unit is printed on one side (front side) by the fixing device 5. The paper for which printing has been completed is discharged as it is from the first discharge port 18 and the printing process is completed.

  Next, the paper conveyance path in the duplex printing mode will be described. The sheet conveyance path in the duplex printing mode is a path indicated by a one-dot chain line and a path indicated by a dotted line in FIG. To explain these routes in order, first, the paper supplied from the paper supply unit is printed on one side (front surface) side by the fixing device 5. The paper on which printing on one side (front surface) has been completed passes through the opening 7 and passes through the single-sided printing unit 3, and the leading edge of the paper advances from the opening 11 into the duplex printing unit 4. When the leading edge advances into the duplex printing unit 4, the sheet is sucked into the duplex printing unit 4 by the inverter roll 9. Thereafter, the paper is further lifted upward by the discharge roll 10 and is once discharged from the duplex printing unit 4 to the outside through the second discharge port 19.

Thereafter, the discharge roll 10 reverses and the paper is drawn into the duplex printing unit 4 again. At this time, the sheet passes through the side of the inverter roll 9 as the route switching plate 15 moves. The sheet that has passed the side of the inverter roll 9 passes through the opening 12 and passes through the single-sided printing unit 3. Thereafter, the toner passes through the opening 8, proceeds further downward, and is supplied again to the fixing device 5 from the lower side. Thereby, the back side is printed.
Thereafter, the path is the same as that in the single-sided printing mode, and the paper on which both sides are printed passes through the first paper transport path 13 indicated by the dotted line and is discharged to the outside from the first discharge port 18 to complete a series of printing processes. To do.

In the sheet conveying apparatus 1 configured as described above, the duplex printing unit 4 is not used in the single-sided printing mode, and therefore the inverter roll 9 does not need to be rotated.
However, in the fixing device 5, heat and pressure are applied through a sheet between a heating roll and a pressure roll, and the toner is melted by heat and pressed against the sheet to perform fixing. For this reason, the moisture contained in the paper rises as water vapor 20 and hits the inverter roll 9 disposed immediately above the fixing device 5 in order to lift the paper that has passed through the fixing device 5 into the double-sided printing unit 4 in the double-sided printing mode. Condensation may occur.

Therefore, the control circuit 16 shown in FIG. 2 issues a command to the inverter roll drive motor 17 to rotate the inverter roll 9 even in the single-sided printing mode. At this time, since the inverter roll 9 does not convey the sheet, it is idled.
In this way, the inverter roll 9 can idle to form a gas layer around itself and shut out the rising water vapor 20. Thereby, the dew condensation which arises in the inverter roll 9 can be prevented.

However, the idling inverter roll 9 is controlled by the control circuit 16 so as to be driven at 100 rpm and 0.2 A. The inverter roll 9 is driven at 250 rpm and 0.5 A when performing the normal function of conveying paper, but it is sufficient if an air layer that shuts out the water vapor 20 is formed when idling. It is driven under the above conditions from the viewpoint of energy saving and noise reduction.
Note that information on the rotational speed is stored in a ROM (not shown) of the control circuit 16.

Next, another embodiment of the present invention will be described.
In the first embodiment, from the viewpoint of energy saving and noise reduction, the inverter roll 9 is idled at a low speed and a low output, thereby preventing condensation on the inverter roll 9.
Here, when the cause of the dew condensation generated in the inverter roll 9 is examined, it is caused by the moisture contained in the paper being vaporized by passing through the fixing device 5 and becoming the water vapor 20. The amount of moisture contained in the paper and the conditions for the occurrence of condensation differ depending on the environmental conditions such as ambient temperature and humidity, and whether or not the condensation occurs is also related to the number of jobs through which the paper passes through the fixing device 5. To do.
Therefore, in this embodiment, the data related to the dew condensation occurrence condition is monitored, and when the dew condensation occurs, the inverter roll 9 is idled so that further energy saving and noise reduction can be promoted. A job number counter 21, a temperature / humidity sensor 22, and a timer unit 23 were attached and connected to the controller 16 as shown in FIG.
Hereinafter, specific control will be described with reference to flowcharts shown in FIGS. 4 and 5. However, for convenience of explanation, the description is divided into control based on the number of jobs and control based on the surrounding environment of temperature / humidity.

(1) Control Based on Number of Jobs First, control based on the number of jobs will be described. In this embodiment, the inverter roll 9 is rotated when the number of jobs is 500 or more, and when there is an interval between jobs, the time of the interval is measured. The inverter roll 9 is rotated when the interval time is 5 minutes or less and the cumulative number of jobs is 500 or more.

  The power is turned on in the single-sided printing mode (step S1), and printing is started. The number of jobs is counted by a job number counter 21, and the count number data is continuously sent to the control circuit 16. The control circuit 16 monitors whether the number of jobs has reached 500 or more (step S2). When the number of jobs exceeds 500, the control circuit 16 issues a command to the inverter roll drive motor 17 to rotate the inverter roll 9 (step S3). Thereby, dew condensation of the inverter roll 9 can be prevented.

  If the number of jobs has not reached 500 in step 2, the interval from the previous job measured by the timer 23 is referred to and it is determined whether or not the interval is 5 minutes or less (step S4). If the interval is 5 minutes or less, the process proceeds to step S5, and it is determined whether the cumulative number of jobs with the previous number of jobs is 500 or more (step S5). If the cumulative number of jobs is 500 or more, the control circuit 16 issues a command to the inverter roll drive motor 17 to rotate the inverter roll 9 (step S3).

  On the other hand, if the interval with the previous job is 5 minutes or longer in step S4, it is considered that the previous job is not affected, so the process proceeds to step S6, and the control circuit 16 instructs the inverter roll drive motor 17 to And the inverter roll 9 is not rotated, that is, stopped (step S6).

(2) Control Based on Environmental Conditions Next, control based on environmental conditions such as ambient temperature and humidity will be described. In this embodiment, the temperature and humidity are monitored, and the inverter roll 9 is rotated when the dew condensation is generated.

The power is turned on in the single-sided printing mode (step S7), and printing is started. The temperature / humidity sensor 22 attached to the paper transport apparatus 1 constantly monitors the temperature and humidity, and sends the monitored temperature and humidity data to the control circuit 16 when the power is turned on (step S7) (step S8). . The control circuit 16 determines whether or not the dew condensation generation condition is satisfied based on the data (step S9).
When it is determined in step S9 that the dew condensation generation condition is satisfied, the control circuit 16 issues a command to the inverter roll drive motor 17 to rotate the inverter roll 9 (step S10). Thereby, dew condensation of the inverter roll 9 can be prevented.

  On the other hand, when it is determined in step S9 that the dew condensation generation condition is not satisfied, the control circuit 16 issues a command to the inverter roll drive motor 17 so that the inverter roll 9 is not rotated, that is, is stopped (step S11).

  Although the above description has been divided into control based on the number of jobs and control based on the surrounding environment of temperature / humidity, each control is simplified for the sake of explanation. Therefore, more complicated control can be performed in consideration of use conditions and the like. It is also possible to integrate the two controls and control the number of jobs, temperature, and humidity. In short, it is only necessary to monitor factors that affect the occurrence of dew condensation, calculate whether or not the dew generation condition is based on the data, and determine whether or not to rotate the inverter roll 9. .

  In addition, said Example 1 and Example 2 are only the examples for implementing this invention, This invention is not limited to these, It is the scope of this invention that these Examples are variously modified. It is obvious from the above description that various other embodiments are possible within the scope of the present invention.

For example, in this embodiment, the inverter roll 9 disposed immediately above the fixing device 5 is most likely to condense due to the influence of water vapor, so that the inverter roll 9 is idled. However, the discharge roll 10 is affected by water vapor and is dewed. The discharge roll 10 may be idled if there is a risk of such a situation.

In the embodiment, the paper transport path in the double-sided printing mode and the paper transport path in the single-sided printing mode overlap with each other when the final paper is discharged. It is also conceivable that the path of the double-sided printing mode is completely different, and the printed paper discharge port in the single-sided printing mode is different from the printed paper discharge port in the double-sided printing mode. With such a configuration, when one path is used, the other path is not used, but the discharge roll included in the unused path may be dewed due to the influence of water vapor. If so, the discharge roll may be idled.

Further, in the embodiment, the inverter roll 9 is likely to condense due to the influence of water vapor because the inverter roll 9 is disposed immediately above the fixing device 5.
Therefore, the inverter roll 9 can be arranged so as to be shifted from directly above the fixing device 5. Thus, if the inverter roll 9 is arranged so as to be shifted from directly above the fixing device 5, the influence of water vapor can be reduced, and if the inverter roll 9 is idled after being configured in this way, condensation can be prevented. Can increase the efficiency.
Therefore, compared to the above embodiment, the occurrence of condensation can be prevented even when the inverter roll 9 is rotated at a lower speed, and further energy saving and noise reduction can be achieved.

  As described above, the sheet conveying apparatus as described above provides a high dew condensation prevention effect. However, when the use environment is severe, a fan or the like can be supplementarily attached. However, even in such a case, it is sufficient that the fan or the like to be attached is smaller than the conventional one, and the driving time may be short, thereby saving power and energy.

Note that the paper conveying apparatus of the present invention may be sold for each unit such as a single-sided printing unit or a double-sided printing unit.
Further, it may be sold as an image forming apparatus together with other functional parts such as an image reading unit.

It is explanatory drawing which shows the outline of a structure of the Example of this invention. FIG. 2 is a block diagram of a control circuit incorporated in the embodiment shown in FIG. It is a block diagram of a control circuit incorporated in another embodiment. It is a flowchart which judges whether an inverter roll is rotated according to the number of jobs. It is a flowchart which judges whether an inverter roll is rotated according to the surrounding environment of temperature / humidity.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Paper conveyance apparatus 2 Fixing unit 3 Single-sided printing unit 4 Duplex printing unit 5 Fixing device 6 Discharge roll 9 Inverter roll 10 Discharge roll 13 First paper conveyance path 14 Second paper conveyance path 16 Control circuit 17 Inverter roll drive motor 20 Water vapor 21 Job counter 22 Temperature / humidity sensor 23 Timekeeping section

Claims (3)

A first paper transport path which is a path downstream of the fixing device and is a path from the opening of the single-sided printing unit to the time when the paper is discharged by the discharge roll;
A path downstream of the fixing device, which is a path through which a sheet is conveyed from a first opening to a second opening on a duplex printing unit placed on the upper side of the simplex printing unit. A second paper transport path;
In the single-sided printing mode, the paper subjected to the fixing process by the fixing device is not passed through the second paper transporting path but is passed through the first paper transporting path, and the paper is discharged by the discharge roll. A control circuit that causes the paper, which has been fixed by the fixing device, to pass through the second paper transport path by the paper transport roll, and is again fixed by the fixing device and discharged by the discharge roll in the mode. A conveying device,
The control circuit causes the paper transport roll to idle in the single-sided printing mode. The paper transport device according to claim 1, wherein the control circuit rotates a paper transport roll during idling at a lower speed than during paper transport. An image forming apparatus comprising the sheet conveying device according to claim 1 .

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