JPH10282828A - Fixing device - Google Patents

Abstract

[PROBLEMS] To provide a fixing device capable of controlling the amount of heat supplied according to the productivity of copying. SOLUTION: In the case of standard productivity (normal speed mode) according to the image reading speed, a cam 3 is used.
7, the movable plate 32 is set at a low position, and the pressing force of the pressing roller 24 against the fixing roller 21 is set as a standard first pressing force. When the image is stored in the memory to increase the productivity and the number of copies per fixed time is equal to or higher than the standard time (high speed mode), the movable plate 32 is pushed up by the rotation of the cam 37 and the urging force of the spring 31 is increased to fix the image. The second pressing force in which the pressing force of the pressing roller 24 to the roller 21 is increased is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device provided in a copying machine, a facsimile, a printer, and the like, for example, a fixing device having a multicolor image forming means.

[0002]

2. Description of the Related Art In a copying machine, a facsimile, a printer, or the like, when a toner having a different productivity is fixed to a transfer sheet by changing the copy productivity, the amount of heat applied to the transfer sheet is reduced. Must be given in optimal amount. If the amount of heat applied is too large, hot offset will occur, and if the amount of heat applied is small, cold offset will occur or fixability will decrease. That is, if the copying productivity is different, the optimum amount of heat applied to the transfer paper by the fixing device is also different. Therefore, an object of the present invention is to provide a fixing device capable of controlling the amount of heat supplied by the copying productivity. .

To change the amount of heat applied to the transfer paper, it is effective to vary the temperature of the fixing roller.
In this case, it takes time for the temperature of the fixing roller to rise or fall, and there is a disadvantage that downtime occurs. Accordingly, the present invention provides a method for controlling the amount of heat applied to
That is, to provide a fixing device capable of reducing downtime by increasing or decreasing the pressure of a fixing roller and a pressure roller, and varying the width of a nip portion between the roller pair to increase or decrease the amount of heat applied to a transfer sheet. With the goal.

In a copying machine or the like having a high copy processing speed, the amount of heat taken by the transfer paper is larger than the amount of heat supplied from a heat source (eg, a halogen heater) to the fixing roller. Will come. When the temperature of the fixing roller is lower than the predetermined temperature, the amount of heat applied to the transfer paper is too low, and the toner does not melt sufficiently and passes through the nip of the pair of fixing rollers. In such a state, in such a state, the feeding timing is controlled so that the temperature of the fixing roller does not further decrease by feeding the paper at an interval longer than a normal interval. This control is called “CPM down control”.

In the CPM down control, the number of sheets to be passed is generally determined in advance in accordance with, for example, the size of the transfer sheet, and setting is performed so that the operation is performed when the number of sheets is reached. This C
The PM down control is a control for guaranteeing the fixability of the toner on the transfer paper, but the fixability of the toner is based on the fixing roller temperature, the fixing nip width, the fixing pressure, the type of the transfer paper, and the size of the productivity. Etc. It changes. Conventionally, in the case of a copying machine or the like having a constant productivity, since the fixing nip width and the fixing pressure are factors that do not fluctuate, control is performed in consideration of only the fixing temperature and the type of transfer paper. However, copiers and the like that have variable productivity and differ in the amount of transfer paper that is fixed for a certain period of time are increasing. Therefore, an object of the present invention is to provide a fixing device capable of further improving the copy quality by changing the control content according to the productivity to be used in such a copying machine having variable productivity. I do.

Further, in order to ensure the fixing property, a control for stopping the feeding of the transfer paper when the temperature of the fixing roller falls below a predetermined value is known. The conditions for fixability are also different. SUMMARY OF THE INVENTION It is an object of the present invention to provide a fixing device capable of improving copy quality by changing a condition for stopping the feeding of transfer paper in accordance with a change in productivity.

[0007]

According to a first aspect of the present invention, there is provided a fixing roller having a heat source for fixing an unfixed image transferred by an image forming apparatus to a transfer sheet. In a fixing device capable of changing the productivity including a pressure roller disposed opposite to the fixing roller and pressed against the fixing roller, and a memory for storing image information corresponding to the transferred unfixed image, Means for switching the pressure by the pressure roller to a plurality of types; means for switching the pressure by the pressure roller selectively changing the pressure by the pressure roller by changing the productivity of the image forming apparatus. It is characterized by switching.

According to a second aspect of the present invention, there is provided a fixing roller having a heat source for fixing an unfixed image transferred by an image forming apparatus onto a transfer sheet, and a fixing roller disposed opposite to the fixing roller and provided with a heat source. A pressure roller to be pressed and pressed; a temperature detecting member for detecting a surface temperature of the fixing roller; a temperature control means for controlling the fixing roller temperature based on information detected by the temperature detecting member; In a fixing device having a memory for storing image information corresponding to a landing image and capable of changing productivity, when the transfer paper is continuously conveyed, control is performed to increase the paper passing interval from a predetermined paper passing interval. CPM down control means;
The M-down control unit changes control contents by changing the productivity of the image forming apparatus.

According to a third aspect of the present invention, there is provided a fixing roller having a heat source for fixing an unfixed image transferred by an image forming apparatus to a transfer sheet, and a fixing roller disposed opposite to the fixing roller so as to face the fixing roller. Pressure roller, a temperature detecting member for detecting the surface temperature of the fixing roller, temperature control means for controlling the fixing roller temperature based on information detected by the temperature detecting member, and the transferred unfixed image. In a fixing device having a memory for storing image information corresponding to an image and capable of changing productivity, when the transfer paper is continuously conveyed, the temperature of the fixing roller is reduced, and the temperature of the fixing roller is reduced to a predetermined temperature. A control unit for stopping the transfer of the transfer sheet when the transfer of the transfer sheet is stopped is changed by changing the productivity of the image forming apparatus. And it features.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a conceptual diagram showing an image forming apparatus of a copying machine using a fixing device according to the present invention. This image forming apparatus forms a negative-positive latent image by performing a first image exposure 3 by an optical system (not shown) on a photoreceptor 2 uniformly charged by a first charger 1. The first image is developed on the photoreceptor 2 by the container 4. For example, the black toner is developed by contact two-component development. Subsequently, the second charger 13
As a result, the surface of the photoconductor 2 is recharged including the black toner image area developed as described above and the non-image area not developed, and the second image exposure 6 is performed by an optical system (not shown). A positive latent image is formed, and the first latent image is formed by the second developing device 5;
Negative-positive development is performed by non-contact development using a toner having a different color tone, for example, a red toner.

The black-red two-color image formed as described above is
The image is transferred to a transfer paper 10 by a transfer belt 9 to which a voltage is applied by a voltage application device 8 through a bias roller 7,
The sheet is conveyed to a fixing device (not shown) by the transfer belt 9.
The second developing device 5 is operated by a solenoid 11 and a spring 12 so as to maintain a small gap with the photoconductor 2 only during development.
The photosensitive member 2 is moved to a position close to or away from the photosensitive member 2.

The conditions of the recharging by the second charger 13 in the two-color development described above are to prevent the mixed color development of the red toner in the black toner development area and to set the red developer (the second developer 5). Is set so that the reverse development of the black toner can be prevented. For example, a black toner image is formed with the first charging potential = −850 V, the first exposure potential = −100 V, the first developing bias = −550 V, and the second charging is determined by an experiment in order to satisfy the above conditions. To achieve the black toner image portion recharge potential = −800 to −900 V, the second charge grid potential = −900 V, and the second exposure potential = −10.
At 0 V and the second developing bias = −750 V, a red toner image is formed by the second developing device 5.

When a mode of black or red or a mode of simultaneous two colors of black and red is selected by an operation unit on a copying machine main body side (not shown), a black developing device,
The red developing device is operated to transfer black toner and red toner to the transfer paper. Then, the transfer paper carrying the black toner and the red toner is transported to the fixing device, and the image is fixed. In addition, a function is provided for storing image information read from an image reading unit (not shown) in a memory and changing the number of copies (productivity) in a certain period of time.

FIG. 2 is a perspective view showing an example of a fixing device provided in the above-described copying machine. Fixing roller 2 of this device
No. 1 has its surface coated with a heat-resistant release layer such as PFA or PTFE, and has a heat source 22 inside. As the heat source 22, a halogen heater or an infrared (Nichrome wire) heater is used. The temperature of the fixing roller 21 heated by the heat source 22 is:
The heating by the heat source 22 is controlled so that the temperature of the fixing roller 21 is detected by the temperature detecting means 23 and becomes a predetermined temperature. The pressure roller 24 that forms a pair with the fixing roller 21 has a surface formed of a heat-resistant rubber (silicon rubber) layer. Further, bearings 25 are provided on the shafts at both ends, and a portion of the bearing 25 is pushed up from below by a pressing lever 26 to be pressed against the fixing roller 21. One end of the pressure lever 26 is rotatably supported by a shaft 27, and the other end of the pressure lever 26 is biased upward by a spring 31. The fixing roller 21 is rotatably driven by a driving unit (not shown) in the direction of the arrow in the figure, and fixes the toner while conveying the transfer paper.

The spring 31 has pressure adjusting means for adjusting the pressing force of the pressure roller 24. The pressure adjusting means has a movable plate 32 provided vertically movably along the side plate 33. The movable plate 32 is provided with a long hole extending in the vertical direction, and the long hole is rotated by the side plate 33. The pivotally supported pivot shaft 34 is slidably fitted. A gear 35 for transmitting rotational driving force from a driving unit (not shown) is provided at one end of the rotating shaft 34.
The other end is provided with a partition plate 36 having a notch at the other end, and a cam 37 is mounted between them.
The cam 37 is always engaged with the movable plate 32 as shown in the figure, and is moved to a first pressing position (the state shown in FIG. 3A) where the lowest portion engages with the movable plate 32 by a driving unit (not shown). The part can be switched so as to be in the second pressing position (the state shown in FIG. 3B) which engages with the movable plate 32.

When the cam 37 is located at the first pressing position, the cam 37 is provided so that the notch of the partition plate 36 can be detected by the detecting member 38. From this state, the driving of a pulse motor or the like (not shown) is performed. By rotating the cam 37 by a predetermined pulse by means, the cam 37 is rotated to the second pressing position. Between the first pressing position and the second pressing position, the cam 3 is moved so that the second pressing position pushes the movable plate 32 upward.
7 operates, the urging force of the spring 31 also increases,
The pressure roller 24 is more strongly pressed against the fixing roller 21. For this reason, for example, in the case of standard productivity (normal speed mode) in accordance with the image reading speed, the first pressure is used, the image is stored in a memory to increase the productivity, and the number of copies per fixed time is reduced. When the time is higher than the standard time (high speed mode), the second pressing force can be used.

Next, an embodiment will be described in which the pressing force by the pressing roller is not selectively switched as described above, but the number of sheets passed is controlled. As described above, when the number of sheets per unit time is large and the fixing process is fast, the heat source 2
Since the amount of heat given to the transfer paper 10 by the fixing roller 21 is larger than the amount of heat supplied to the fixing roller 21 from 2, the temperature of the fixing roller 21 lowers and the fixability deteriorates when continuous paper passing is performed. In the case of performing continuous paper passing more than the number of sheets N0 (hereinafter referred to as CPM down start number),
When the paper is passed after the CPM down start number N0, the CPM is controlled so that the paper passing interval per unit time is set to be, for example, 0.75 times the normal number of sheets to be passed, by extending the paper passing interval as compared with the normal case. Perform down control to prevent fixing failure.

In the CPM down control in the fixing device of this embodiment, the number of sheets C0 for starting the CPM down is set to the value shown in FIG. 4 according to the type of copying productivity, and the control shown in the flowchart of FIG. 5 is executed. In this example, in the case of the normal speed mode, the CPM down start number N0 = N1
In the high speed mode, N0 = N2.

This control counts the number N of sheets to be continuously fed, determines whether the number of passed sheets has reached the CPM down start number N0, and starts the CPM down control. This control will be described with reference to the flowchart of FIG. First, after the operation of the copying machine or the like is started, the selection mode of the productivity mode is checked (step 1).
Next, the CPM down start number N0 is determined according to the selected mode (step 2), and thereafter, the number of passed sheets is counted (step 3).
It is determined whether or not N ≧ N0 by comparing the PM down start number N0 (step 4). If N <N0, paper is fed at a normal paper passing interval (step 5).
The number of passed sheets is reduced by the M down control (step 6).

At this time, the CPM down start number N0 (N
1, N2) differs depending on the size of the transfer paper. In this case, assuming that the length of the transfer sheet is L and the normal sheet passing interval is X, the sheet passing gap Y required to make the CPM down rate 0.75 is

## EQU1 ## Since Y = [(1−0.75) L + X] /0.75, when the CPM is down, the paper passing at the paper passing interval X is changed to the paper passing interval Y. You just need to pass it. In this way, deterioration of the fixing property is prevented from occurring, and a high quality fixed product can be obtained.

Next, in order to prevent a decrease in fixing property and a defective fixing when a large number of sheets are passed and the fixing process is fast, the temperature of the fixing roller 21 is maintained at a predetermined temperature (normal fixing property can be guaranteed). A description will be given of an embodiment in which the control for stopping the sheet feeding when the temperature becomes lower than the above is performed. In a fixing device having such control, when there are a plurality of types of productivity, the fixing property cannot be guaranteed unless the control mode is changed in accordance with the magnitude of the productivity. Therefore, as shown in FIG. 6, the temperature TS for stopping the sheet feeding (sheet passing stop temperature) is set to T1 in the normal speed mode depending on the type of each productivity.
In the high speed mode, the temperature is set to T2 ° C., and the control shown in the flowchart of FIG. 7 is executed.

In this control, when the fixing operation is performed, first, the selected productivity mode is checked (step 1), and then the paper passing stop temperature T corresponding to the productivity mode is checked.
S is determined as shown in FIG. 6 (step 2).
Thereafter, the temperature T of the fixing roller 21 is measured by the temperature detecting means 23 (Step 3), and it is determined whether or not the difference between the set temperature TS of the fixing roller 21 and the measured temperature T is T0−T ≧ TS (Step 4). ), If T0−T <TS, paper is fed at a normal paper passing interval (step 5), and T0−T ≧ TS
In the case of (1), the paper feeding is stopped (step 6). In this manner, the stop condition is changed in accordance with the change in the type of productivity, so that the copy quality is improved without the occurrence of poor fixability.

[0023]

As described above, in the fixing device according to the first aspect, when fixing images to different numbers of transfer papers in a certain period of time with different productivity, the fixing heat amount adapted to the productivity. The fixing roller pair (fixing roller and pressure roller)
Since the pressure can be varied and provided in an optimum amount by increasing or decreasing the pressing force, there is an effect that the copy quality can be improved. Also, compared with the method of changing the amount of heat applied to the transfer paper by changing the temperature of the fixing roller, the width of the nip portion of the roller pair can be adjusted only in a very short time, and the downtime can be reduced. There is also.

According to the second aspect of the present invention, as described above, in a device in which the copying process speed is high and continuous copying is performed, the temperature of the fixing roller is lowered to deteriorate the fixing property. Since the CPM down control for changing the interval is changed according to the productivity of copying, there is an effect that the copy quality can be further improved.

According to the third aspect of the present invention, as described above, the control for stopping the feeding of the transfer paper when the temperature of the fixing roller falls below a predetermined value in order to secure the fixing property is performed.
Since the condition for stopping the feeding of the transfer paper is changed according to the change in productivity, there is an effect that the copy quality can be further improved.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing an image forming apparatus of a copying machine using a fixing device according to the present invention.

FIG. 2 is a perspective view showing an example of a fixing device provided in the copying machine of FIG.

FIG. 3 is a conceptual diagram showing two pressing positions of the fixing device of FIG. 2;

FIG. 4 is a CPM in an embodiment of the fixing device according to the present invention.
It is a figure which shows the content of down control.

FIG. 5 is a CPM in one embodiment of the fixing device according to the present invention.
It is a figure which shows the flow of a down control.

FIG. 6 is a diagram showing the content of a paper stop control in an embodiment of the fixing device according to the present invention.

FIG. 7 is a diagram illustrating a flow of a sheet passing stop control in an embodiment of the fixing device according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 first charger 2 photoreceptor 3 first image exposure 4 first developer 5 second developer 6 second image exposure 7 bias roller 8 voltage application device 9 transfer belt 10 transfer paper 11 solenoid 12 spring 13 second charger DESCRIPTION OF SYMBOLS 21 Fixing roller 22 Heat source 23 Temperature detection means 24 Pressure roller 25 Bearing 26 Pressure lever 27 Shaft 31 Spring 32 Movable plate 33 Side plate 34 Rotating shaft 35 Gear 36 Partition plate 37 Cam 38 Detection member

Claims (3)

[Claims] 1. A fixing roller having a heat source for fixing an unfixed image transferred by an image forming apparatus to transfer paper, and a pressure roller disposed opposite to the fixing roller and pressed against the fixing roller. And a memory for storing image information corresponding to the transferred unfixed image, wherein the fixing device can change the productivity. The fixing device has means for switching the pressing force of the pressure roller to a plurality of types. A fixing device, wherein the means for switching the pressure by the pressure roller selectively switches the pressure by the pressure roller by changing the productivity of the image forming apparatus. 2. A fixing roller having a heat source for fixing an unfixed image transferred by an image forming apparatus to transfer paper, and a pressure roller disposed opposite to the fixing roller and pressed against the fixing roller. A temperature detecting member for detecting a surface temperature of the fixing roller; a temperature control unit for controlling the fixing roller temperature based on information detected by the temperature detecting member; and image information corresponding to the transferred unfixed image. And a memory for storing productivity, the control unit performing control to increase the paper passage interval from a predetermined paper passage interval when the transfer paper is continuously conveyed.
M down control means, said CPM down control means,
A fixing device, wherein the control content is changed by changing the productivity of the image forming apparatus. 3. A fixing roller having a heat source for fixing an unfixed image transferred by the image forming apparatus to a transfer sheet, and a pressure roller disposed opposite to the fixing roller and pressed against the fixing roller. A temperature detecting member for detecting a surface temperature of the fixing roller, a temperature control means for controlling the fixing roller temperature based on information detected by the temperature detecting member, and image information corresponding to the transferred unfixed image. In a fixing device having a memory for storing and changing the productivity, the temperature of the fixing roller is reduced when the transfer paper is continuously conveyed, and the temperature of the transfer paper is reduced when the temperature of the fixing roller falls below a predetermined temperature. A fixing device, comprising: control means for stopping conveyance, wherein the control means changes the condition when the conveyance is stopped by changing the productivity of the image forming apparatus.