JP2002202684A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device capable of efficiently keeping the accuracy of pressuring force without hindering workability and obtaining excellent copying quality. SOLUTION: This fixing device is provided with a pressuring force adjusting device changing pressuring force in accordance with the operational amount of a driving device as a means for changing the pressuring force by selecting the optimum value out of the set values of the pressuring force of a multistage pressure roller and a fixing roller decided in advance according to a condition such as the kind and the thickness of transfer paper and fixing temperature in the case of fixing an unfixed image formed and transferred by an image forming device on transfer paper, a detecting device for detecting the pressuring force at a specified value being reference, and a control means capable of optionally setting the operational amount of the driving device. In the device, the pressuring force is restored to a reference position detected by the detecting device when the specified condition is satisfied and the transfer paper does not pass, and the operational amount of the driving device is initialized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat roller fixing type fixing device having a fixing roller and a pressure roller provided in a copying machine, a facsimile, a printer, and the like.

[0002]

2. Description of the Related Art Conventionally, (1) "Japanese Patent Laid-Open No.
No. 1 (fixing device of a copying apparatus) includes a cam and a driving device as adjusting means for adjusting the pressing force between the fixing roller and the pressing roller, and the pressing force distribution is obtained by changing the cam by an arbitrary amount. The technology for improving the workability of the pressure adjustment operation between the fixing roller and the pressure roller and improving the accuracy of the pressure adjustment is disclosed in (2) Japanese Patent Application Laid-Open No. 8-26.
No. 7852 (Paper misalignment correction apparatus) describes that when a copying machine conveys a sheet, the detecting means for detecting an end position in the lateral width direction of the sheet and the detecting means for detecting the conveying amount detect the lateral displacement of the sheet. And (3) Japanese Patent Application Laid-Open No. 10-282828 discloses a technique for controlling a pressure adjusting device that increases or decreases the pressure applied to at least one end of a pair of conveying rollers to correct lateral displacement.
Publication No. (Fixing device) ”, the pressure applied to the pressure roller of the fixing roller can be changed, and the amount of heat supplied can be controlled appropriately by switching to the appropriate pressure according to the productivity of copying, and copy quality can be improved. Are disclosed.

That is, in a fixing device of a heat roller fixing type used in a copying machine, a facsimile, a printer, or the like, an optimum amount of heat is given to the transfer paper when fixing the toner, depending on the type and thickness of the transfer paper used. Must-have. To achieve this, it is effective to change the amount of heat applied to the transfer paper by making the temperature of the fixing roller variable, but this method takes time for the temperature of the fixing roller to rise or fall. This causes downtime. Therefore, as described in the conventional example (3), by changing the pressure applied by the pressure roller to the fixing roller, the nip width between the roller pair is changed, and the amount of heat applied when the transfer paper passes is changed. There is a way to adjust. In a copying machine with a high copy processing speed or a copying machine in which the heat capacity of the fixing roller is reduced to shorten the time from when the power is turned on to when copying is possible, when a large amount of transfer paper is continuously passed, a heat source is supplied to the fixing roller. In some cases, the amount of heat transferred from the transfer paper by the transfer paper exceeds the amount of heat supplied by the transfer paper, and the temperature of the fixing roller decreases, so that the toner does not sufficiently melt and the fixing property deteriorates. Also in this case, besides suppressing the temperature drop by making the paper feed interval longer than usual, the pressure applied by the pressure roller to the fixing roller is increased, and the shortage of heat is compensated for by increasing the pressure applied to the transfer paper. Methods for ensuring fixing quality have been proposed.

[0004] For these purposes, there have been proposed a number of techniques for changing the pressing force between the roller pairs. For example, a method using a cam as described in the above-mentioned conventional example (1), As described in the conventional example (2), there is a method using a feed screw.
The one using the feed screw of (2) is excellent in practicality because the pressing force can be set with high accuracy and resolution.
This method will be briefly described with reference to FIGS. That is, as shown in FIGS. 3 and 4, at both ends of the fixing device 14, stepping motors 28 constituting a pressure adjusting device are provided, respectively.
The bracket 30 is moved up and down via the gear 31 and the feed screw 32 by the driving force of
Thereby, the pressing roller 17 can be moved toward the fixing roller 16 (pressing direction). Reference numeral 33 denotes a photo sensor, which is adjusted so as to detect when the pressure between the rollers 16 and 17 reaches a reference set value, and serves as a reference when changing the pressure. Is giving a position.
The control device (not shown) calculates an offset from the reference of the pressing force due to the displacement amount of the driving device, and operates the driving device so that the pressing force becomes the selected optimum value.

[0005]

However, in the pressing force adjusting device having the above-described configuration, errors caused by backlash and the like are accumulated when the driving device is operated to change the pressing force for changing the fixing conditions. This may make it impossible to obtain an optimum pressing force. In addition, in the case of a control method in which the pressure is changed to return to the reference position once and then move to the target position in order to prevent such a problem, the operation time of the driving device becomes longer, so that the copy operation is performed. There was a problem that it was necessary to slow down the operation and the operation noise was worrisome.

Accordingly, an object of the present invention is to solve the problems of the conventional fixing device as described above, and to efficiently maintain good accuracy of pressure without impairing workability. An object of the present invention is to provide a fixing device capable of obtaining good copy quality.

[0007]

In order to achieve the above object, the present invention provides a method for fixing an unfixed image formed and transferred by an image forming apparatus to a transfer sheet, the type, thickness and fixing of the transfer sheet. As means for selecting an optimum pressure setting value of the multi-stage pressure roller and fixing roller predetermined according to conditions such as temperature and changing the pressure force, the pressure is changed according to the operation amount of the driving device. A pressure adjusting device for changing the pressure,
In a fixing device having a detecting device for detecting that the pressing force is at a predetermined reference value and a control device capable of arbitrarily setting an operation amount of a driving device, a predetermined condition is satisfied, and the transfer paper is passed. The pressure is returned to the reference position detected by the detection device when the operation is not performed, and the operation amount of the drive device is initialized. Further, when the initialization operation is performed when the number of times the pressure is changed reaches a predetermined value, the correction operation of the pressure error is performed when the number of times of the pressure change operation reaches the predetermined value. By doing so, a correction operation can be performed in anticipation of accumulation of errors.

[0008]

FIG. 1 shows an overall schematic configuration of an image forming apparatus 1 to which the present invention is applied. That is, FIG.
As shown in FIG. 1, inside the apparatus main body, there are provided paper feeding means 4, 4 having a plurality of paper feeding cassettes 2 and paper feeding rollers 3, and the paper 5 fed by these paper feeding means 4, 4 is registered. The toner is conveyed to the photoreceptor 7 which is rotationally driven by the roller 6 at a certain timing. When the photoreceptor 7 is rotationally driven, the surface thereof is uniformly charged by the charging charger 8. On the other hand, the scanner section 9 reads the original reflected light from the exposure lamp, processes the read data, and transmits the read image data to the laser optical system. Then, the laser beam is applied to the charged photoreceptor 7 by this laser optical system to form an electrostatic latent image. The electrostatic latent image is visualized by a developer (toner) when passing through the developing device 12, and the visible image is transferred to the sheet 5 conveyed to the photoconductor 7, and the sheet 5 To the fixing device 14.

As shown in FIG. 2, a fixing roller 16 of the fixing device 14 is coated on its surface with a heat-resistant release layer such as PFA or PTFE, and has a heat source 18 inside. The heat source 18 includes a halogen heater and infrared rays (Nichrome wire).
A heater is used. The pressure roller 17, which forms a pair with the fixing roller 16, has a surface formed of a heat-resistant rubber (silicon rubber) layer. The surface of the fixing roller 16 and the pressure roller 17 are provided with temperature detecting members 21 and 22 such as thermistors, respectively, so that the temperatures of the fixing roller 16 and the pressure roller 17 are respectively set to appropriate values. Not control device by heat source
The energization by 18 is controlled. The pressure roller 17 is pressed against the fixing roller 16 by pushing up both ends of the shaft by a pressure lever 19. One end of the pressure lever 19 is rotatably supported by a shaft, and the other end of the pressure lever 19 is urged upward by a pressure spring 20 being hung. The fixing roller 16 is driven to rotate in a direction indicated by an arrow by a drive unit (not shown), and heats and presses the transfer paper on which the unfixed image is formed by the developing unit 12 to melt and fix the toner. In the drawing, reference numeral 24 denotes a separating claw, 23 denotes a temperature fuse, and 16a denotes an oil application roller for performing oil and cleaning on the fixing roller 16.

FIGS. 3 and 4 are structural views showing an example of a pressing force adjusting device 35 for adjusting the pressing force of the pressing roller 17. That is, this pressure adjusting device has a bracket 30 which is vertically movable along the side plate, and the other end of the pressure spring 20 for pressing the pressure roller 17 is connected to the bracket 30. A female screw 30 a formed in a vertical direction is provided substantially at the center of the bracket 30, and the female screw 30 a is screwed with the feed screw 32. A gear 31 for transmitting a rotational driving force from the stepping motor 28 is attached to an upper portion of the feed screw 32, and is supported by a bearing. further,
A photo sensor 33 is provided on the side plate, and this photo sensor 33 is turned on by the detecting piece 30b of the bracket 30 when the pressure of the pressure roller 17 becomes a reference value (stop of pressure application). The mounting position has been adjusted so that

FIG. 5 is a block diagram showing a schematic configuration of an electric system in the pressure adjusting device. That is, the control unit 38 includes a CPU 39 for performing various processing operations, a timer / counter 40, and an RO in which a control program is fixedly stored in advance.
M41, RAM42 for temporarily storing various information, PIO43
(Parallel input / output terminals). Also,
44 and 45 are stepping motor drivers for sending drive signals (pulses) to the stepping motors 28 and 28, respectively. These stepping motor drivers 44 and 45 are PIs.
Connected to O43. Photo sensors 33, 33 are connected to the PIO 43.
In response to the ON / OFF signal of 33, the stepping motor 28 is rotated via the stepping motor drivers 44 and 45. Note that the pressure adjusting device does not necessarily need to be provided along the side plate, and may be provided, for example, in parallel with the pressure roller 17. In this case, there is a method in which the pressure spring 20 is hooked on another lever, and the lever operates the pressure lever 19. When a pulse is applied to the stepping motor 28 to rotate it from this state, the bracket 30 meshing with the feed screw 32 moves up and down by an amount proportional to the given pulse. In other words, when the bracket 30 moves upward, the urging force of the pressure spring 20 increases, and the pressure roller 17
Is more strongly pressed against the fixing roller 16, and conversely, if the bracket 30 is moved downward, the pressing roller 17
The applied pressure is reduced. Therefore, the photo sensor 33 is
If the relationship between the pressure at the reference point N and the number of pulses applied to the stepping motor 28 and the change in the pressure is determined,
Any desired pressure can be set.

FIG. 6 shows a control processing procedure according to the present invention.
This will be described with reference to the flowchart of FIG. First, conditions such as the currently selected paper type and paper thickness are checked to determine a fixing pressure to be used (step 1). Next, the number of pulses counted from a reference point to which the pressing force is applied is determined and set as the target number of pulses (step 2). Also, the current pulse count is compared with the target pulse number.If the current pulse count is smaller than the target pulse number, a forward rotation pulse is output to increase the count.If the current pulse count number is larger than the target pulse number, a reverse rotation pulse is output to reduce the count. Repeat until the number of pulses matches the target number of pulses (step 3). The pulse count is "0" when the pressing force is at the maximum, and the direction in which the pressing force increases in the rotation direction of the stepping motor 28 (FIG. 4) is "forward rotation".
Here, FIG. 7 shows an example of a conversion table for determining the fixing pressure from the paper conditions (type / paper thickness).

Next, an initialization operation at the time of turning on the power or at the time of recovery from a jam will be described with reference to a flowchart shown in FIG. First, at the time of the initialization operation, the stepping motor 28 is rotated until the photo sensor 33 is turned on in order to set an initial value in the pulse counter. However, when the photo sensor 33 is ON from the beginning, the operation is performed after returning to the position where the photo sensor 33 is once turned OFF (step 1). Next, when the photo sensor 33 (FIG. 4) is turned on, the pulse counter is initialized and the pressure is set to the initial setting in the normal operation (step 2). Thereafter, by repeatedly changing the fixing pressure as described above, a means for removing accumulated errors is counted and the number of times the pressure is changed is counted.
30 is moved to a predetermined reference point, thereby initializing the number of pulses of the stepping motor 28 and removing an error.

The details of the above control will be described with reference to a flowchart shown in FIG. In the control routine for performing the above-described pressing force changing operation, the counter is incremented each time the changing operation is completed (routine 1). Next, the value of the counter is checked by a routine called at regular intervals by a timer / counter 40 built in the main body control unit 38 (FIG. 9) (routine 2, step 1).
When the predetermined value is reached, it is confirmed that the copying operation is not being performed (step 2), and the operation for initializing the number of pulses is started. First, a pulse is sent to the stepping motor 28 to rotate it until the bracket 30 returns to the reference position and the photo sensor 33 is turned on. When the photo sensor 33 is turned on by the rotation of the stepping motor 28, the stepping motor 28 is stopped and the pulse counter is initialized. Thereafter, the pressure is set again to match the conditions such as the current paper type and paper thickness shown in FIG. 7 (step 3). Finally, the counter of the number of times of change operation is cleared (step 4).

As a result, the error can be eliminated, so that better copy quality can be maintained.
An embodiment in which the initialization operation is performed when the image forming operation has not been performed for a predetermined time after the final transfer paper has passed will be described with reference to a flowchart shown in FIG. 10 (claim 2).
That is, in addition to the operation described above, the timer / counter 40 is incremented each time the routine is called at regular time intervals. However, this timer / counter 40 is always cleared during the copying operation (step 1). Next, the value of the counter is checked (step 2). When the value reaches a predetermined value, the operation for initializing the number of pulses is started. The contents of the initialization operation are the same as those described above (step 3). Finally, the counter of the number of times of the pressing force change operation is cleared, and the process ends (step 4).

[0016]

According to the first aspect of the present invention, when an unfixed image formed and transferred by an image forming apparatus is fixed on a transfer sheet, the paper type, paper thickness,
As a means for selecting the optimum pressing force from among a plurality of set values according to conditions such as the fixing temperature and changing the pressing force between the fixing roller and the pressing roller, the pressing force is changed according to the operation amount of the driving device. A fixing device having a pressing force adjusting device, a detecting device for detecting that the pressing force is at a predetermined reference value, and a control device capable of arbitrarily setting an operation amount of the driving device, satisfying predetermined conditions. When the transfer paper is not passed, the pressing force is returned to the reference position detected by the detecting device, and the operation amount of the driving device is initialized. Therefore, the initializing operation is performed to change the pressing force. By removing the accumulation of errors due to repetition, there is an effect that good pressure accuracy can be efficiently maintained with a small number of operations.

According to a second aspect of the present invention, by performing the above-described pressurizing error correction operation when the number of pressurizing force change operations reaches a predetermined value, the correction operation can be performed in anticipation of accumulation of errors. Therefore, there is an effect that the above-mentioned object can be achieved more efficiently. According to a third aspect of the present invention, when the copying machine is not used for a long time by performing the above-described operation of correcting the pressing force error even when the image forming operation has not been performed for a fixed time after the final transfer paper has passed. It is possible to start copying with good accuracy of pressurizing force when using after performing a correcting operation, and to reduce the possibility that workability due to entering the correcting operation during use is hindered. effective.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram showing an example of a copying machine equipped with a fixing device of the present invention.

FIG. 2 is an overall configuration diagram showing an identification landing device.

FIG. 3 is a perspective view showing an example of a pressing force adjusting device in the identification attachment device.

FIG. 4 is an enlarged view of a main part of FIG. 3;

FIG. 5 is an overall block diagram schematically showing the pressing force adjusting device.

FIG. 6 is a flowchart showing a control system of the pressing force control device.

FIG. 7 is a table showing an example of a conversion table for determining pressurization according to paper conditions.

FIG. 8 is a flowchart illustrating a processing procedure in an initial operation.

FIG. 9 is a flowchart illustrating a processing procedure according to the first embodiment of the present invention.

FIG. 10 is a flowchart illustrating a processing procedure according to the second embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 image forming apparatus 2 paper feed cassette 3 paper feed roller 4 paper feed means 5 paper 6 registration roller 7 photoreceptor 8 charging charger 9 scanner unit 12 developing device 13 transport belt 14 fixing device 16 fixing roller 16a oil application roller 17 pressure roller 18 Heat source 19 Pressing lever 20 Pressing spring 21, 22 Temperature detecting member 23 Temperature fuse 24 Separating claw 28 Stepping motor 30 Bracket 33 Photo sensor 35 Pressing force adjusting device 38 Control unit 39 CPU 40 Timer / counter 41 ROM 42 RAM 43 PIO 44, 45 stepping motor driver

Claims (3)

[Claims] 1. A multi-stage pressure roller which is predetermined according to conditions such as the type, thickness and fixing temperature of a transfer sheet when an unfixed image formed and transferred by an image forming apparatus is fixed on a transfer sheet. And a means for selecting the optimum value of the pressing force between the fixing roller and the fixing roller and changing the pressing force, a pressing force adjusting device for changing the pressing force according to the operation amount of the driving device, and a pressing force as a reference. In a fixing device having a detecting device for detecting that the driving value is at a predetermined value and a control device capable of arbitrarily setting the operation amount of the driving device, a predetermined condition is satisfied and the transfer paper is passed. When there is no fixing device, the pressing force is returned to the reference position detected by the detecting device, and the operation amount of the driving device is initialized. 2. The fixing device according to claim 1, wherein the initialization operation is performed when the number of times the pressure is changed reaches a predetermined value. 3. The fixing device according to claim 2, wherein an initialization operation is performed when the image forming operation has not been performed for a predetermined time after the final transfer paper has passed.