JP2001083825A - Fixing device for image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a fixing device for image forming device capable of smoothly carrying a transfer paper to the fixing device without being excessively affected by sucking force at an inlet guide and preventing fixing heat from lowering. SOLUTION: This fixing device is provided with a fixing part having a fixing roll 11a and a pressure roll 11b, a carrying part 12 for carrying the transfer paper (13) carrying a toner image toward the fixing roll 11a, the inlet guide 14 guiding the transfer paper (13) from this carrying part 12 to a nip between the two rolls 11a and 11b and having plural through holes 11b for sucking air, and a sucking means 15 by which the sucking force is generated for the sucking through holes 11b. In this case, the device is provided with transfer paper detecting means 16 and 17 in a transfer paper feeding in part and a transfer paper feeding out part of the inlet guide 14, and a control means to control the operation of the sucking means 15 based on signals from the transfer paper detecting means 16 and 17.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for an image forming apparatus, and more particularly, to a fixing device which facilitates supply of transfer paper to a fixing section having a fixing roller.

[0002]

2. Description of the Related Art Generally, in a fixing device used in an image forming apparatus, for example, as shown in FIG. 4, transfer paper 2 transported by a transport belt 1 extending from a transfer area side.
Through the entrance guide 3 so as to enter a nip portion between the fixing roller 4 and the pressure roller 5. However, in the fixing device provided with such an entrance guide 3, various use conditions, such as use of roll paper, continuous leaving for a long period of time, or being placed in a high humidity environment, for example. Under the respective conditions, the transfer paper 2 conveyed to the fixing device often undergoes deformation such as curling, and if the transfer paper 2 is fed into the fixing device as it is, the transfer roller 2 is heated by the fixing roller 4 described above. Due to the nip portion between the transfer paper 2 and the pressure roller 5, a crease or wrinkles may be formed on the transfer paper 2.

Therefore, a transfer paper suction mechanism for preventing or forcing the transfer paper 2 from being deformed or curled in the entrance guide 3 has been conventionally proposed. For example, in the example of FIG. 4 described above, a plurality of air suction holes 3a are provided in the paper guide surface of the entrance guide 3, and suction holes are provided below the paper guide surface of the entrance guide 3. A suction means 6 such as a fan is provided. In this case, the transfer paper 2 is brought into close contact with the entrance guide 3 by a suction force when external air is sucked through the through-hole 3 a by the suction means 6. As a result, first, as shown in FIG.
Will be sucked flat on the paper guide surface of
Deformation such as curling of the transfer paper 2 is prevented or forced.

[0004]

However, in such a conventional transfer paper suction mechanism, the suction force becomes too large depending on the size of the transfer paper 2, and the transfer resistance of the transfer paper 2 becomes excessive. In some cases, a conveyance failure, a jam, or the like may occur, or in the worst case, the operation of feeding the transfer paper 2 may be stopped. In addition, since the high-temperature air in the portion where the fixing is performed is sucked, the fixing temperature is lowered, which may cause a fixing defect.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is possible to prevent a suction force acting on an entrance guide from excessively acting on a transfer sheet and to smoothly transfer the transfer sheet. It is another object of the present invention to provide a fixing device of an image forming apparatus that can prevent the temperature of a fixing unit from lowering.

[0006]

According to a first aspect of the present invention, there is provided a fixing apparatus for an image forming apparatus, comprising: a pair of fixing rollers; and a transfer sheet carrying a toner image. Transport unit that transports the paper toward the fixing roller, an entrance guide that guides the transfer paper transported by the transport unit to enter the fixing unit between the fixing rollers, and a plurality of air suction units provided at the entrance guide. A fixing unit for an image forming apparatus, comprising: a through hole; and a suction unit that generates suction force in the suction through hole to bring the transfer sheet into close contact with the entrance guide. Transfer paper detection means for detecting the arrival of the transfer paper is provided on each of the transfer paper detection side and the delivery section, and the suction means is provided based on a detection signal from each of the transfer paper detection means. Control means for controlling the operation are provided.

Further, in the fixing device of the image forming apparatus according to the present invention, the suction means includes a suction fan, and the control means detects the transfer paper on the transfer paper receiving portion side. The operation of the suction fan is started based on the detection of the transfer paper by the means, and the suction fan is moved at a low speed or stopped based on the detection of the transfer paper by the transfer paper detection unit on the transfer paper sending unit side. It has a function of guiding to the fixing roller.

Further, in the fixing device of the image forming apparatus according to the third aspect of the present invention, the control unit controls the suction only when large-size transfer paper or roll transfer paper is used or in a high humidity environment. It has a function of controlling the means to operate.

[0009]

In the fixing device of the image forming apparatus according to the first aspect of the present invention, the transfer paper sent to the fixing unit is sucked toward the entrance guide only when entering the fixing nip of the fixing roller. As a result, the necessary minimum suction is possible, so that the load on the transfer paper due to the suction force during the fixing operation is reduced, and the unnecessary suction force on the transfer paper is reduced. As a result, the fixing roller does not suffer any breakage of the edges or wrinkles, so that transfer paper of extremely high quality can be conveyed. Further, since the decrease in fixing heat due to the suction of external air is minimized, the fixing state is improved, and the heating efficiency in the fixing step is improved.

On the other hand, in the fixing device for an image forming apparatus according to the second or third aspect of the present invention, the operation according to the first aspect is performed extremely smoothly.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. First, FIG. 1 is a schematic sectional view of a fixing device provided in an image forming apparatus such as a copying machine and the vicinity thereof, and extends from a transfer area (not shown) in the image forming apparatus toward the fixing device 11. The transport unit 12 includes a transport belt that transports the transfer paper 13 onto which the toner image has been transferred to the fixing device 11.

Further, the fixing device 11 includes the transport belt 1.
2 includes a fixing roller 11a and a pressure roller 11b that promote fixing of the toner image while nipping the transfer paper 13 conveyed by the transfer roller 13.
An entrance guide 14 for guiding the transfer paper 13 to enter the fixing unit is disposed near the upstream side (right side in the figure) of the fixing unit, which is the nip portion of b. Further, on the downstream side (left side in the figure) of the fixing unit of the rollers 11a and 11b, the transfer paper 13 which has undergone the fixing operation is transferred to the rollers 11a and 11b.
Separating claws 11c for peeling off from the fixing rollers 11a and 11b are in contact with the fixing roller 11a. These structures are the same as those of the conventional fixing device shown in FIGS. 4 and 5 described above.

On the other hand, the above-mentioned transport belt 12 and both fixing rollers 11a and 11b
A guide plate 14a is provided so as to bridge a portion between the fixing unit and the fixing unit, and the guide plate 14a
The transfer paper 13 to which the toner image is transferred is configured to be transferred. The guide plate 14a has a plurality of suction holes 1
The suction means 4b is formed below the guide plate 14a, and a suction means comprising a suction fan 15 for applying a suction force to the suction holes 14b is formed below the guide plate 14a.
The suction fan 15 is provided with a support plate 15a that stands upright to support an upstream (right end in the figure) edge of the guide plate 14a.
Are mounted substantially horizontally with respect to the support plate 15a and the guide plate 14a by performing suction in the horizontal direction.
Is formed in a negative pressure state.

In the fixing device, the guide is provided on the guide plate 14a of the entrance guide 14 on the side where the transfer paper 13 is received (the right end in the drawing), that is, on the downstream end of the conveyor belt 12. The first transfer paper detecting means 16 is provided near the plate 14a. Also,
Transfer paper 13 on guide plate 14a of entrance guide 14
A second transfer sheet detecting means 17 is provided on the sending side (left end side in the figure), that is, on the downstream edge of the guide plate 14a. The second transfer paper detecting means 17 is arranged so as to be close to the entrance side of a fixing portion (nip portion) by the fixing roller 11a and the pressure roller 11b.

In the present embodiment, the first and second transfer paper detecting means 16 and 17 are constituted by tilting bar switches which are oscillated by the passage of the transfer paper 13. It is possible to employ a wide variety of other sensors, such as optical sensors for optically detecting. Each of these transfer paper detecting means 16,
Reference numeral 17 is connected to control means for controlling the apparatus starter (not shown), the transfer paper transporting unit, the suction fan 15 and the like, and controls the operation of the suction fan 15 when the transfer paper 13 passes. Has the function of outputting the detection signal to the control device. More specifically, the control means outputs an operation command signal for starting the operation of the suction fan 15 upon receiving the detection signal of the transfer paper 13 by the above-mentioned first transfer paper detection means 16 on the upstream side, It has a function of receiving a detection signal of the transfer paper 13 passing through the entrance guide 14 from the second transfer paper detection means 17 on the downstream side, and outputting an operation command signal for lowering and stopping the operation of the suction fan 15. .

On the other hand, the control means takes precedence over the detection signals from the two transfer paper detecting means 16 and 17 when the transfer paper 13 is of a large size or roll paper.
Alternatively, it has a function of outputting an operation command signal for causing the suction fan 15 to operate only in a high-humidity environment where the transfer resistance of the transfer paper 13 to the entrance guide 4 becomes large. In order to detect the size of the transfer paper 13 and the humidity at that time, separate detection means are appropriately provided, and the detection signals are input to the control means, and the detection signal is supplied to the suction fan 15. An operation command signal is output.

In the fixing device having the above-described structure, as shown in FIG. 3, when the image forming apparatus starts to be started (step 1), the transfer paper 13 on which the image has been transferred is fixed by the conveying belt 12 to the fixing section of the fixing device 11. Is sent to
If the size of the transfer paper 13 is a large size larger than a predetermined size, if it is roll paper, or if it is a predetermined high humidity environment (Yes in step 2), the state in which the suction fan 15 is operated is continued, On the other hand, if the state is the opposite (No in step 2), the suction fan 15 is maintained in the non-operation state.

When the transfer paper 13 is fed onto the guide plate 14a of the entrance guide 14 having the suction holes 14b by the transport belt 12, the first transfer paper detection provided on the transfer paper receiving portion side of the entrance guide 14 is detected. When the leading edge of the transfer paper 13 is detected by the means 16 (Ye in step 3)
s) On the basis of the operation command signal from the control means having received the detection signal, the rotation drive of the suction fan 15 is started (step 4). Thereby, the above-mentioned entrance guide 1
4, external air is sucked into the inlet guide 14 through the suction hole 14b of the guide plate 14a, and at this time, a suction force acts on the leading edge portion of the transfer paper 13, and the leading end of the transfer paper 13 The edge portion is brought into close contact with the guide plate 14a. As a result, the transfer paper 1 is transferred to the fixing unit including the fixing roller 11a and the pressure roller 11b.
The sheet 3 is fed while being prevented from being deformed such as curling or being forced flat.

On the other hand, the guide plate 14a of the entrance guide 14
When the transfer paper 13 approaches the fixing unit, the leading edge portion of the transfer paper 13 is detected by the second transfer paper detection means 17 (Yes in step 5). The suction fan 15, which has received the operation command signal based on this detection signal, first becomes slow and the suction force is weakened, and then stops after a predetermined time has elapsed (step 6). That is,
The transfer resistance of the transfer paper 13 at the entrance guide 14 is:
Once the paper has been reduced to a predetermined size, the conveyance is continued for a certain period of time, and after the transfer paper 13 has been conveyed by a certain amount, there is no suction resistance by the entrance guide 4 at all. The paper is sent out between the rollers 11a and 11b of the apparatus 11.

As described above, the transfer paper 13 sent to the fixing unit
The guide plate 1 of the entrance guide 14 is used only when entering the fixing nip portion between the fixing rollers 11a and 11b.
Since the suction is performed toward the side 4a, the necessary minimum suction is performed. That is, the unnecessary suction force on the transfer paper 13 is reduced or stopped, and the load on the transfer paper 13 due to the suction force during the fixing operation is greatly reduced.
Of the fixing roller 1
No breaks or wrinkles are generated in 1a and 11b, and extremely high quality transfer paper is conveyed.

Further, as described above, the fixing unit is connected to the transfer paper 13.
Is passed, the suction means 15 is stopped, so that the heat of the suction section is transferred to the suction holes 14 in the entrance guide 14.
b, therefore, a decrease in fixing heat is prevented, and a decrease in fixing heat due to suction of external air is minimized.
Power waste is also reduced.

Although the embodiments of the present invention have been specifically described above, the present invention is not limited to the above embodiments, and it is needless to say that various changes can be made without departing from the gist of the present invention. Nor. For example, the second transfer paper detecting unit 17 in the above-described embodiment is provided on the feed side of the fixing unit. However, if the suction force at the entrance guide 14 is small, the outside of the fixing unit, that is, the separation It is also possible to provide at a position close to the claw 11c.

Further, the suction means is not limited to the suction fan as in the above-described embodiment, but various suction means such as a negative pressure generating means can be adopted. Further, the present invention can be similarly applied to an image forming apparatus other than a copying machine.

[0024]

The fixing device according to the present invention having the above configuration has the following effects. According to the present invention, a suction hole is provided in an entrance guide of a fixing device, suction means for generating a suction force is provided in the suction hole, and transfer paper of an entrance guide close to a transport unit for transporting the transfer paper to a fixing unit is provided. Recording paper detecting means are provided at the receiving section and at the sending section to the fixing section at the entrance guide, respectively, and the detecting means at the transfer paper receiving section detects the transfer paper and activates the suction section, while the entrance guide at the fixing section side of the entrance guide Since the control means for stopping the suction means by detecting the transfer paper by the transfer paper detection means is provided, the transfer paper is sucked to the entrance guide only when entering the fixing nip of the fixing section, and the fixing is performed. The load on the transfer paper due to the suction force can be reduced while preventing heat suction, and unnecessary operation of the suction means is eliminated. The roller can transport high-quality transfer paper with no creases and wrinkles, enabling extremely good transport operation, and preventing a reduction in fixing heat to improve fixing performance and prevent waste of power. It has excellent effects.

Further, in the present invention, both the deformation prevention of the transfer paper and the transport operation are performed satisfactorily by stopping the suction fan of the suction means at a low speed. A paper transport operation can be obtained.

The present invention is also applicable to the case where large-size transfer paper or roll paper having a large resistance is used during conveyance so that the suction means does not cause a conveyance failure depending on the size of the transfer paper, or in a high humidity environment. Since the control is performed so that the suction means is operated only in the case, etc., under the condition that the suction force is strongly received, the suction means is controlled to reduce the suction force and the transfer of the transfer paper is performed. It can be performed smoothly.

[Brief description of the drawings]

FIG. 1 is a side view of a fixing device in an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a side view illustrating a transfer state of transfer paper in the fixing device of FIG. 2;

FIG. 3 is an explanatory diagram of an operation of a control unit in the fixing device.

FIG. 4 is a schematic side view of a fixing device in a conventional image forming apparatus.

FIG. 5 is a side view illustrating transfer of transfer paper in the fixing device of FIG. 4;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Fixing apparatus 11a Fixing roller 11b Pressure roller 12 Conveying belt 13 Transfer paper 14 Inlet guide 14a Guide plate 14b Suction hole 15 Suction fan (suction means) 16 1st transfer paper detection means 17 2nd transfer paper detection means

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H033 AA02 AA14 BA08 BA12 BB01 CA11 CA16 CA17 CA22 CA26 3F048 AA01 AB01 BA05 BA07 BD07 CC03 CC17 DA06 EA15 EB27 3F049 FA03 FA05 FC07 FC19 LA02 LA07 LB03 3F101 FB07 FC04 LA01LB03

Claims (3)

[Claims] An image forming apparatus comprising: a pair of fixing rollers; a transport unit configured to transport a transfer sheet carrying a toner image toward the fixing roller; and fixing the transfer paper transported by the transport unit between the fixing rollers. Guide, a plurality of air suction holes provided in the inlet guide, and suction means for generating a suction force in the suction holes to bring the transfer paper into close contact with the inlet guide. And a transfer sheet detecting means for detecting the arrival of the transfer sheet at each of the transfer sheet receiving section side and the transfer section side of the entrance guide. And a control unit for controlling the operation of the suction unit based on a detection signal from each of the transfer paper detection units. 2. The suction means includes a suction fan, and the control means starts operation of the suction fan based on transfer paper detection by transfer paper detection means on the transfer paper receiving section side. And a function of guiding the transfer sheet to a fixing roller after the suction fan is slowed down or stopped based on transfer sheet detection by a transfer sheet detection unit on the transfer sheet sending unit side. Item 2. A fixing device for an image forming apparatus according to Item 1. 3. The control means has a function of controlling the suction means to operate only when large-size transfer paper or roll transfer paper is used or only in a high-humidity environment. The fixing device according to claim 1, wherein: