KR19980024077A - Fixing Device for Electrophotographic Printing Device - Google Patents

Abstract

The fixing of the toner image on the transparent sheet for transparencies compared to the normal paper requires electrolytic photography because the transparent sheet for the transparencies requires a circular conveying path to the fixing unit in order to obtain the light transmittance and to increase the fixing time. It has hindered the miniaturization of the printing apparatus. Slowing down the rotation of the fixing roller of the fixing unit causes the distortion of the image due to the change of the speed of the whole image forming process, and improves the complexity of the control of the entire photo process, and makes it easier to control the electrophotographic processor. Provided is a fixing device of a small and inexpensive electrophotographic printing apparatus with stable image quality.

When the printout medium is an OHP transparent sheet, the fixing device 14 is inserted into the heating roller 14b, which is the fixing roller, and the fixing backup roller 14c, and the fixed sheet OHP transparent sheet Q is rotated forward and Rotate in reverse and perform several heating and fixing processes on the transparent sheet Q for OHP.

Description

Fixing Device for Electrophotographic Printing Device

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing apparatus which heat-fixes a toner image onto a recording medium after transferring the toner from the consultation medium to the recording medium in a hard copying apparatus such as a printer and a copying apparatus.

7 is a sectional view of a conventional electrophotographic printing apparatus described in, for example, Japanese Patent Laid-Open No. 4-7564. Such an electrophotographic printing apparatus is composed of the following process steps. A charging process that uniformly charges the surface of the photosensitive member, a light emitting process that partially discharges the charged charge by irradiating the photosensitive member to form a latent image according to image information, a developing process of forming a toner image by attaching a toner as a developer to the latent image A transfer process for transferring an image onto a recording medium (hereinafter referred to as paper), a cleaning process for removing toner remaining on the photoconductor, and a fixing process for fixing the transferred toner image on paper by heating.

In the figure, the cylindrical photosensitive member 1 is freely attached to a frame (not shown). The charger 2 performs the charging process by evenly charging the surface of the photoconductor 1. The furnace luminous flux 3 is irradiated to the photoconductor 1 by the light irradiation means of an optical system, is irradiated to the photoconductor 1, and partially charges the charge of the photoconductor 1. In other words, the luminous process is carried out. Thereafter, the developer 4 attaches the toner to the latent image 1 on the photoconductor 1 to form a toner image. In other words, the development process is performed. The developing unit 4 possesses four toners of yellow (T), magenta (M), cyan (C), and black (BK).

A belt-shaped consultation member 6 in an endless form is disposed adjacent to the photosensitive member 1. The consultation member 6 rotates in synchronization with the photosensitive member 1. The toner developed for each color on the photoconductor 1 is superimposed by the first transfer device 7 to produce a color toner image. The second transfer machine 8 is disposed below the consultation member 6. The second transfer machine 8 transfers the color toner image on the consultation body 6 to the paper P conveyed by the paper feeder by electrostatic action.

The first transfer machine 7 and the second transfer machine 8 perform a transfer process.

The cleaner 5 is arrange | positioned around the photosensitive member 1 between the consultation support body 6 and the charger 2. The cleaner 5 performs a cleaning process for removing the toner remaining in the photoconductor 1.

A fixing unit 9 is disposed on the right side of the drawing of the second transfer machine 8. The paper P is conveyed from the second transfer machine 8 to the fixing unit 9 by the conveyance belt 10.

The fixing unit 9 fixes the toner image transferred on the sheet P by melting it on the sheet P. In other words, the fixing process is performed. In the lower part of the conveyance belt 10, the re conveyance path 11 is attached in order to pass the paper P several times, and to let it pass through the 2nd transfer machine 8. At the exit of the fixing unit 9, a separator for selecting whether to return the paper P to the retransmission path 11 or to carry it out as a complete image is arranged.

In the electrophotographic printing apparatus as described above, image printing can be performed using a transparent sheet for overhead projector (OHP) in addition to image printing on plain paper (opaque). In the case where the toner image is fixed to the transparent sheet, in order to increase the reproducibility of the color, it is necessary to completely melt the colored donor image on the transparent sheet and to flatten the surface thereof to ensure light transmittance. As a method of completely melting the toner to secure light transmittance, a fixing time in the fixing process is relatively longer than that of ordinary paper. For this reason, it bypasses the said re conveyance path 11 and passes through the fixing unit 9 several times, and time to fully melt a toner is obtained.

In addition to the above-mentioned examples, the electrophotographic printing apparatus which detects that the paper P is transparent and automatically lowers the fixing speed on the plain paper to the fixing speed, thereby prolonging the fixing time and improving the melt state of the toner. Is also.

In the case of re-feeding the paper to the fixing unit and fixing a plurality of times, the refeeding path 11 to the fixing unit having a length corresponding to the paper size must be provided. In other words, the retransmission path 11 requires a length in the path from when the end of the paper is completely discharged from the fixing unit to the end of the paper entering the fixing unit again. Therefore, a long conveyance path corresponding to the paper size is required. For this reason, there is a problem that the apparatus main body becomes very large and the cost is increased.

In addition, in the case of fixing by slowing the fixing speed, it is necessary to uniformly change the conveying speed over the entire surface of the paper in order to prevent the toner image from being disturbed (image deterioration) due to expansion and contraction in the conveying direction of the paper.

Therefore, in the case of slowing down the fixing speed, it is necessary to slow down the rotational speed of the consultation member 6 together with the rotational speed of the fixing roller. In other words, in each of the modes of fixing colored toner to plain paper and of fixing to transparent sheet, the control of the entire electrophotographic process is complicated. In particular, immediately after switching modes, it is difficult to obtain the best electrophotographic process conditions (property values) suitable for the respective imaging speeds, and thus there is a problem that the stability of image quality is impaired.

Moreover, since there are several thicknesses of the transparent sheet for OHP generally marketed, the fixing conditions for obtaining the optimal permeability differ for each transparent sheet.

Therefore, in the case of fixing to a thick transparent sheet, the fixing operation must be repeated several times three to four times. Since the paper passes through the long paper conveying path 11 each time, there is a problem that the surface of the transparent sheet is damaged and the image deteriorates.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and in obtaining an image requiring light transmissivity such as an image on a transparent sheet, the control of the electrophotographic process is easy, and the fixing device of a small and inexpensive electrophotographic printing apparatus with stable image quality. The purpose is to provide.

The fixing apparatus of the electrophotographic printing apparatus according to claim 1 of the present invention is provided with a reciprocating lamp means for heating and fixing several times by rotating the fixing roller of the fixing apparatus forward and reverse when the print output medium is a transparent sheet for OHP. It is.

The fixing apparatus of the electrophotographic printing apparatus according to claim 2 of the present invention makes it possible to vary the number of times of fixing reciprocation or the like in correspondence with the type of transparent sheet.

The fixing apparatus of the electrophotographic printing apparatus according to claim 3 of the present invention is capable of varying the speed of the fixing roller only when the fixing roller is reversed in correspondence with the type of transparent sheet.

1 is a view showing the main configuration of the electrophotographic printing apparatus of the present invention;

2 is a view for explaining the operation of the first embodiment of the present invention;

3 is a chart showing an example of the relationship between the thickness of the transparent sheet of Embodiment 2 and the speed at the time of reversal of the heating roller;

4 is a view showing an outline of a fixing unit part of Embodiment 3 of the present invention;

5 is a view for explaining the operation of the third embodiment of the present invention;

6 is a view showing an outline of a fixing device part according to Embodiment 4 of the present invention;

7 is a cross-sectional view of a conventional electrophotographic printing apparatus.

Explanation of symbols on the main parts of the drawings

1: photosensitive member, 2: charger,

3: furnace beam by light irradiation means, 4: developer,

5: cleaner, 6: counseling delay

6c: transfer backup roller, 7, printing machine, 8: second transfer machine,

9: fixing unit, 13: transfer roller, 14: fixing unit,

14a: heating heater, 14b: heating roller, 15: control unit,

14c: fixed backup roller, 16, 17: auxiliary roller,

18: paper guide, 18a: opening, 19, 20: sensor,

22: paper evacuation path, P: paper, Q: transparent sheet.

Embodiment 1

Fig. 1 is a diagram showing the main parts of the electrophotographic printing apparatus of the present invention.

In the drawings, 1 to 7 are the same as those described in the above conventional example. A drive motor 6b is attached to the inside of the consultation member 6. The drive motor 6b transmits the rotational torque through the drive roller 6a and circulates the consultation body 6. The transfer backup roller 6c also extends the consultation member 6 and also serves as one electrode of the transfer apparatus described later.

The transfer roller 13 is provided so as to be foldable with the transfer backup roller 6c while sandwiching the consultation member 6 and the sheet P. FIG. When the transfer roller 13 moves in the transfer backup roller 6c direction, the consultation member 6 and the paper P come into contact with each other. The folding operation of the transfer roller 13 is controlled by the controller 15. DC voltage is applied between the transfer roller 13 and the transfer backup roller 6c. This DC voltage is transferred onto the sheet P on the toner of the consultation body 6. In other words, the transfer roller 13 constitutes a second transfer device. A fixing device 14 is disposed on the left side of the drawing of the transfer roller 13. The fixing device 14 includes a drive motor for driving the fixing back-up roller 14c and the heating roller 14b which are in contact with the heating roller 14b and the heating roller 14b, which are built-in heating heaters 14a. 14d). The drive motor 14d is controlled by the control unit 15 to rotate the heating roller 14b. The control unit 15 controls the forward and reverse rotation speed of the heating roller 14b and the number of times of rotation (rotation time).

On both outer sides of the fixing device 14, two auxiliary rollers 16 and 17 are arranged, respectively. The auxiliary rollers 16 and 17 are rotated at the same speed in the same direction in synchronism with the heating roller 14b. The auxiliary rollers 16, 17 are arranged to be foldable with the sheet P. FIG. Between the transfer roller 13 and the fixing device 14, a paper guide 18 for guiding the paper P from the transfer roller 13 to the fixing device 14 is disposed.

Sensors 19 and 20 are arranged adjacent to both sides of the fixing device 14. The sensors 19 and 20 detect the front end and the rear end of the paper P or the transparent sheet Q described later.

In the electrophotographic printing apparatus configured as described above, when fixing plain paper, the paper P conveyed from a paper cassette (not shown) is passed between the transfer roller 13 and the transfer backup roller 6c, and the transfer roller 13 is transferred and backed up. The turner on the consultation body 6 is transferred onto the sheet P by the force of the electric field against the side of the roller 6c. The paper P on which the toner is transferred is passed through the paper guide 18 between the heating roller 14b and the fixing backup roller 14c while being heated, and the toner melts and is fixed to the paper P therebetween. At this time, the auxiliary roller 17 is squeezed from the sheet P, and the unfixed toner is not disturbed by the auxiliary roller 17. In this way, the electrophotographic printing process on the plain paper is terminated. However, in the case of the transparent sheet Q for OHP, the toner must be completely melted on the transparent sheet in order to improve color reproducibility. In addition, the fixing process time is short as the fixing process time, such as the plain paper. Therefore, in the present invention, the control unit 15 recognizes that the fixing sheet is fixed to the transparent sheet by input from another sensor or control condition setting unit. Then, once the sensor 20 detects the rear end of the transparent sheet passing through the fixing device 14, the heating roller 14b is rotated in reverse to heat the transparent sheet again through the fixing device 14 again. The sensor 19 detects that the second heat setting is completed, and the heating roller 14b is rotated again (forward rotation) to continue the heat setting.

This state is explained with reference to FIG.

(a) The toner on the consultation member 6 is transferred to the transparent sheet Q by the transfer roller 13. The tip of the transparent sheet Q is conveyed to the fixing device 14, and the toner is melted by the forward rotation of the heating roller 14b. The auxiliary roller 17 is in a position away from the transparent sheet Q.

(b) When the sensor 20 detects the rear end of the transparent sheet Q, the rotation of the heating roller 14b stops and rotates in reverse.

(c) When the toner is heated and melted by the reverse rotation of the heating roller 14b, and the sensor 19 detects the tip of the transparent sheet Q, the reverse rotation of the heating roller 14b is stopped. At this time, the auxiliary roller 17 is in contact with the transparent sheet Q so that the transfer roller 13 is separated from the consultation member 6.

(d) Subsequently, the rotation of the heating roller 14b is returned to the normal rotation. The toner on the transparent sheet Q is conveyed to the discharge side with repressurization and reheating. The toner transferred onto the transparent sheet Q is sufficiently melted and the necessary permeability is obtained. And the transparent sheet Q is discharged | emitted from the fixing apparatus 14, and the fixing process is complete | finished.

(e) The number of fixation reciprocations is increased by the type thickness of the transparent sheet for OHP and the toner is completely melted.

Embodiment 2

Since the transparent sheet for OHP has many kinds, such as thickness, optimal toner melt-fixing is not necessarily performed by the integral multiple of the uniform heating settling time demonstrated in Embodiment 1 mentioned above. Either way, it overheats and the transparent sheet Q may deform in some cases.

It is only necessary to change the rotational speed of the heating roller 14b by the type of transparent sheet Q. However, as described in the section of the prior art problem, the change of the speed of the transfer roller becomes a cause of image disturbance and is difficult. Therefore, only at the time of reverse rotation of the heating roller 14b, by setting the speed to the optimum rotational speed by the type of the transparent sheet Q, the complete melt fixing of the toner and the deformation of the transparent sheet Q are prevented. An example of the relationship of the thickness of this transparent sheet and the speed at the time of reverse rotation of a heating roller is shown in FIG.

Embodiment 3

Fig. 4 is a diagram showing an outline of a fixing device part in Embodiment 3 of the present invention. In the drawings, (6), (13), (14), and (18 to 20) are the same as those described in the first embodiment. The discharge roller 21 is not necessarily synchronized with the peripheral speed of the heating roller 14b. The sensors 19 and 20 are separated from the distance L1 and L2 from the contact position of the heating roller 14b and the fixing backup roller 14c, respectively.

This is because the sensors 19 and 20 need to have a certain diameter because the heating roller 14b has a built-in heating heater 14a in order to reduce the influence of heat from the heating roller 14b. Because.

The operation of the third embodiment will be described with reference to FIG. 5. 5 (a) shows a state where the toner is transferred to the transparent sheet Q, and the front end of the transparent sheet Q is exposed to the fixing apparatus. From this state, the transparent sheet Q is conveyed to the drawing left side, and the state where the rear end of the transparent sheet Q was detected by the sensor 19 is shown in FIG. 5 (b). Since the distance L1 of the sensor 19 is known from the contact position of the heating roller 14b and the fixing backup roller 14c, and the rotational speed of the heating roller 14b is also known, the sensor 19 is the rear end of the transparent sheet Q. After detecting, the transparent sheet Q is transferred only for a predetermined time, and the heating roller 14b is neatly arranged so that the heating roller 14b is converted into reversal.

That is, the heating roller 14b is reversed in the state in which the heating roller 14b and the fixing backup roller 14c hold | maintain the state which hold | maintained the rear end of the transparent sheet Q. The state in which the sensor 20 detects the front end of the transparent sheet Q by reversing the heating roller 14b is shown in Fig. 5C. From this state, as described above, the heating roller 14b and the fixing backup roller 14c hold the front end of the transparent sheet Q, and the reversal of the heating roller 14b is stopped to switch to forward rotation.

In this way, the transparent sheet Q is always inserted between the heating roller 14b and the fixing backup roller 14c to reciprocate the transparent sheet Q, so that the auxiliary rollers 16 and 17 described in Embodiment 1 are not necessary and the apparatus is not necessary. Can simplify the configuration and contribute to miniaturization of the device.

Embodiment 4

Fig. 6 is a diagram showing an outline of a fixing device portion according to Embodiment 4 of the present invention. In the drawings, (6), (13), (14), and (18 to 21) are the same as those described in the third embodiment. In the opening 18a formed in the middle of the paper guide 18, a paper escape passage 22 is provided continuously.

The following operation is described. The front end of the transparent sheet Q, to which the toner is transferred from the consultation member 6 by the transfer roller 13, is sent to the fixing device 14. Fig. 6 (a) shows this state. At this time, the opening 18a has a step so that the tip of the transparent sheet Q exceeds the opening 18a. Then, when the fixing by the reversal of the heating roller 14b is started from the fixing by the forward rotation of the heating roller 14b, the rear end of the transparent sheet Q to be conveyed back is the paper evacuation path 22 due to the step of the opening 18a. Enter

In this way, by evacuating the rear end of the transparent sheet Q to the paper evacuation path 22 at the time of reversal of the heating roller 14b, the rear end of the transparent sheet Q does not come into contact with the counseling member 6, Contamination of the image by the adhesion of the remaining toner in 6) is prevented.

In addition, in the absence of the paper evacuation path 22, the rear end of the transparent sheet Q contacts the consultation body 6 even if the toner of the next image is developed on the consultation body 6 when the fixing time to the transparent sheet Q is long. Since the developing image is destroyed, it is necessary to wait for the completion of the fixation and start the next printing phenomenon, and the printing processing speed becomes slow. By evacuating to the paper escape path 22, the developing process of the next image is executed in the consultation member 6 regardless of the fixing process.

In claim 1 of the present invention, in the case of the transparent sheet for OHP, heat fixing is performed several times by rotating the fixing roller of the fixing device forward and reverse to improve the melting of the toner and the light transmittance on the transparent sheet for OHP. Good images are obtained.

According to claim 2 of the present invention, the number of reciprocating reciprocations and the like can be varied in correspondence with the type of transparent sheet, so that the toner can be completely melted, and an image with better color can be obtained.

In claim 3 of the present invention, since the speed of the fixing roller is varied only when the fixing roller is reversed in correspondence with the type of the transparent sheet, the overheating of the transparent sheet for OHP during fixing is eliminated and the beep due to the heat of the transparent sheet for OHP is fixed. The distortion can be prevented.

It is an object of the present invention to provide a fixing device for a small and inexpensive electrophotographic printing apparatus, in which an electrophotographic process is easily controlled and an image quality is also stable in obtaining an image requiring translucency of an image on a transparent sheet.

Claims (3)

A fixing apparatus of an electrophotographic printing apparatus, wherein a toner image that has developed an electrostatic latent image is transferred to a printout medium, and then heat-fixed. And an reciprocating means for performing a plurality of heating and fixing operations by rotating the fixing roller of the fixing apparatus forward and reverse when the print output medium is a transparent sheet for an overhead projector (OHP). Fixing device. The method of claim 1, A fixing apparatus for an electrophotographic printing apparatus, characterized in that the number of reciprocating reciprocating tunnels can be variably selected in correspondence with the type of transparent sheet. The method of claim 1, A fixing apparatus of an electrophotographic printing apparatus, characterized in that the speed of the roller is variably selected only when the fixing roller is reversed in correspondence with the type of transparent sheet.