JPH02109064A - Color image forming device - Google Patents

Abstract

PURPOSE:To obtain a toner image of proper color reproducibility on an OHP film by providing a two-way detecting sensor which detects the conveyance of a recording medium from two directions between the fixing roller and the paper ejecting roller of a fixing part which constitutes the image forming device and switching medium conveyance in normal and reverse directions by means of a signal issued from the sensor. CONSTITUTION:In the fixing part 40 in which a toner image transferred on the recording medium is thermally fixed, a toner recovering part 38, the fixing roller 40a and the paper ejecting roller 40b are provided, and the two-way detecting sensor 43 which detects the conveyance of the recording medium from two directions is arranged between the rollers 40a and 40b. Then the sensor 43 is composed of an light emitting part 43a, a light receiving part 43b and a detecting lever 43c positioned between them. The lever 43c is moved up and down by a switch not shown in a figure to pass or shield light. Then the switch is turned into an ordinary mode in which ordinary image recording is performed and into a re-fixing mode (OHP) in which fixing temperature is set higher than the temperature in the ordinary mode. Thus, fixing operation is repeated for several times and the toner is perfectly melted. Resultantly, the color reproducibility is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a color image forming apparatus, and more specifically,
Sufficient color reproducibility when throwing = j? The present invention relates to a color image forming apparatus that can produce an OHP film that can produce 1F by electrophotography.

(Background of the Invention) Next, a conventional example will be explained using the drawings. FIG. 5 is a block diagram illustrating a conventional color image forming apparatus.

In the figure, 1 is a photosensitive drum rotating in the direction of arrow 1;
2 is a charger that applies a uniform charge to the photoreceptor drum 1 and charges the surface of the photoreceptor drum 1 in a sweeping manner; 3 is a charger that drives a laser diode (not shown) based on image signals of multiple colors;
This is an exposure section that forms electrostatic latent images of each color on the photoreceptor drum 1. Numeral 4 consists of developing units 4a, 4b, and 4c loaded with red, blue color toner, and black toner, respectively, and 1 and 4 of the corresponding color are placed on the photoreceptor drum 1 on which an electrostatic latent image is formed.
This is a developing section that forms images. 5 is a first paper feeding section.

The first paper feeding section 5 is provided with paper feeding cassettes 6a and 6b provided for each size or type of recording medium P.

73 and 7b in the first paper feed section 5 are paper feed cassettes 6a and 6b.
This is a feeding belt that feeds out the recording medium P placed therein one by one.

Reference numeral 8 denotes a second paper feed unit that feeds the recording medium P fed out from the first paper feed unit in the direction of the photosensitive drum 1 at a constant timing. 9 shines light onto the photoreceptor drum 1 after development. C,
A pre-transfer exposure device (P
TL), 10 is a transfer section that transfers toner from the photosensitive drum 1 to the recording medium P. 11 performs AC discharge,
This is a separation section that separates the recording medium P from the photoreceptor drum 1. Reference numeral 12 denotes a separating claw that securely separates the recording medium P from the photosensitive drum 1. A cleaning section 13 removes residual toner on the photosensitive drum 1.

14 is a pre-charging exposure device (PCL) for erasing the residual potential on the photosensitive drum 1.

Reference numeral 15 designates a fixing unit that thermally fixes the toner image transferred onto the recording medium P, and reference numeral 16 designates a transport unit that transports the recording medium P separated from the photosensitive drum 1 in the direction of the determining unit 15. .

Next, the operation of the above configuration will be explained. First, the photoreceptor drum 1 is charged by the charger 2, and an electrostatic latent image is formed on the photoreceptor drum 1 at the exposure section 3 based on a first image signal (for example, red). This electrostatic latent image corresponding to red is developed as a red toner image by a developing device 4a. The photosensitive drum 1 rotates once, and then the second image 1
An electrostatic latent image is formed on the photoreceptor drum 1 based on the 9 signals (for example, blue). Shizuka corresponding to this blue? 'l! The latent image is developed as a blue toner image by a developing device 4b. Furthermore, the photoreceptor drum 1 rotates once, and based on the image signal (for example, black) of the third file, the photoreceptor drum 1
An electrostatic latent image is formed thereon. This electrostatic latent image corresponding to black is developed as a black toner image on the photosensitive drum 1 by the developing device 4C.

After the three-color toner images are formed on the photosensitive drum 1 in this manner, the transfer operation begins.

That is, the recording medium P placed in the selected cassette 6a, 6b of the first paper feed section 5 and fed out to the second paper feed section 8 by the corresponding delivery belt 7a, 7b is moved to the second paper feed section 8. 2 is transported to the transfer unit 1O by the paper feeding unit 8 at the appropriate timing. Then, the three-color toner image is transferred onto the recording medium P in the transfer section 1 ( ).
The recording medium P is separated from the recording medium P. The recording medium P separated from the photoreceptor drum 1 is conveyed to the fixing section 15 by the conveyance section 16, where the three-color toner image 19 on the recording medium P is
is thermally fixed onto the recording medium P.

On the other hand, residual toner is removed from the photosensitive drum 1 from which the recording medium P has been separated in a cleaning section 13. Furthermore, P.T.
L9 and PCL14 are activated from the moment the main switch of the device is turned on.

(Problems to be Solved by the Invention) In the conventional example of Mizosei Kamiki, when an OHP film is used as the recording medium P and a monochrome image or a color image is formed on the OHP film, 11 copies are taken in the normal mode. If you do this, the toner on the OHP film will not be completely fixed.
1. The surface of the layer becomes uneven. When such an OHP film is applied to a projector, light scatters in the toner layer, impairing the color reproduction of the projected image. Therefore, in order to improve the fixability of toner to OHP film, when forming an image on OHP film, it is necessary to switch to a mode that is provided separately from the normal mode and increase the fixing temperature to perform fixing. In addition, this problem is dealt with by setting the speed at the fixing section slower than the speed until fixing.

However, when increasing the regular temperature, the temperature cannot be set very high, and sufficient heat is not provided to melt the toner, resulting in insufficient color reproducibility. Also, even when the speed at the fixing section is reduced, if continuous copying is performed, there is a risk that the subsequent OHP film will collide with the previous OHP film at the fixing section.
%, and in this case, too, there is a problem that sufficient heat is not given to melt the toner, resulting in insufficient 11f color development.

The present invention has been made in view of the above problems, and its object is to provide a color image forming apparatus that can form toner images with good color reproducibility on OHP films.

(Means for Solving the Problems) The present invention, which solves the above problems, includes a charging section that uniformly charges the surface of a photoreceptor, and an electrostatic latent image of each color on the photoreceptor based on image signals of multiple colors. an exposure section that forms an image, a development section that forms an image using toner of a corresponding color from the electrostatic latent image, a paper feed section that feeds a recording medium, and a toner that uses toner of all colors. a transfer section that transfers an image onto a recording medium fed from the paper feeding section; a separating section that separates the recording medium from the photoreceptor; a fixing section that fixes the toner image on the recording medium; and a fixing section that fixes the toner image on the recording medium; A color image forming apparatus including a conveyance section that conveys a medium from the separating section to the fixing section, wherein a bidirectional detection device that detects conveyance of the recording medium from both directions between a fixing roller in the fixing section and a paper ejection roller. A sensor is provided, and a control means is installed that receives a signal from the bidirectional detection sensor and switches the conveyance of the recording medium between forward and reverse directions.
It was designed so that

(Function) In the color image forming apparatus of the present invention, when the control means receives a signal from the bidirectional detection sensor, it switches the conveyance direction of the recording medium between forward and reverse.

(Example) Next, one embodiment of the present invention will be described using the drawings.

FIG. 1 is a block diagram illustrating an embodiment of the present invention, a perspective view of the essential parts of the bidirectional detection sensor shown in FIG. 1, FIG. 3 is a control block diagram of the main parts in FIG. 1, and FIG. 1 is a diagram illustrating a flow of the color image forming apparatus shown in FIG. 1. FIG.

First, in FIG. 1, 21 is a photosensitive drum that rotates in the direction of arrow 1, 22 is a scorotron charger that uniformly charges the surface of the photosensitive drum 21, and 23 is a laser diode ( (not shown), and forms an electrostatic latent image of each color on the photoreceptor drum 21. Developing units 24a, 24b, and 24c loaded with red, blue color toner, and black toner, respectively;
This is a developing section that forms a toner image of a corresponding color on the photoreceptor drum 21 on which an electrostatic latent image is formed.

25 is a first paper feeding section. In this first paper feeding section 25, 26 is a paper feeding cassette that continuously feeds recording media.

Reference numeral 31 denotes a feeding roller that feeds out the recording medium placed in the paper feed cassette 26. Reference numeral 32 denotes a second paper feeding section that conveys the unfed recording medium toward the photosensitive drum 21 at a proper timing. 33 is the photosensitive drum 21 after development
A pre-transfer exposure device (PTL) 34 irradiates light to maintain the potential on the photoreceptor drum 21 at a constant level, and 34 is a transfer section that transfers the toner image formed on the photoreceptor drum 21 to a recording medium. 35 performs AC discharge, and the photosensitive drum 21
This is a separating section that separates the recording medium from the recording medium. , 36 are separating claws that ensure the separation of the recording medium from the photosensitive drum 21. A cleaning section 37 removes residual toner on the photosensitive drum 21. 38 is cleaning section 3
This is the recovery section 1 for recovering the residual [-ner removed in step 7]. '39 is a pre-charging exposure device (PCL) for erasing the residual potential on the photosensitive drum 21.

40 is a fixing section that thermally fixes the toner image transferred onto the recording medium, and 41 is a conveyance section that conveys the recording medium separated from the photoreceptor drum 21 toward the fixing section 40. Inside the fixing unit 40, there is a fixing roller 40a that applies heat to the recording medium to heat-fix the toner image onto the recording medium, and a paper discharge roller 40b that discharges the heat-fixed recording medium to the outside of the apparatus. and is provided. Reference numeral 43 denotes a bidirectional detection sensor 43 that is provided between the fixing roller 40a and the discharge roller 40b and detects conveyance of the recording medium from both directions.
It is. 42 is a cooling fan that cools the inside of the apparatus.

Here, the bidirectional detection sensor 43 will be explained using FIG. The bidirectional detection sensor 43 includes a starting part 43a,
It consists of a light receiving section 43b and a detection lever 43c rotatable in the recording medium conveyance direction. Normally, this detection lever 43c is located at a position where it blocks the detection beam emitted from the light emitting section 43a toward the light receiving section 43b, and at this time, the bidirectional detection lever 43 emits an off signal.

The color image forming apparatus of this embodiment is provided with a normal mode in which normal image recording is performed and a resetting mode (OHP mode) in which the fixing temperature is set higher than in the normal mode. This switch can be done using the OH button on the operation panel.
This is done by pressing the P mode switch 44 (see FIG. 3).

Next, the control block of this embodiment will be explained using FIG. In the figure, 50 is a CPU that captures various data, performs calculations based on the captured data, and outputs the calculation results, 51 is a motor drive circuit, and 52 is a CPU that controls the fixing temperature in the fixing unit 40 by 1. This is a fixing temperature control circuit that controls the fixing temperature.

Next, the operation of the above configuration will be explained. Here, since the image forming process in the normal mode is the same as in the conventional example, the explanation will be omitted, and the fixed digit resetting mode (OHP mode) will be explained using FIG.

For the reset blue mode, select the OHP mode switch 44,
Start by pressing the copy button. At this time, the fixing temperature in the fixing section 40 is set higher than in the normal mode via the fixing temperature 11 control circuit 52.

Then, charging is performed in the charging section 22 (step 1),
Exposure is performed in the exposure section 23 (step 2), and the development section 24
Development is performed at the second paper feeding section 32 (step 3), paper is fed at the second paper feeding section 32 (step 4), transfer separation is performed at the transfer/separation section 34, 35 (step 5), and then the fixing section 40
The fixing roller 40a performs fixing one time (step 6).

Next, it is monitored whether the bidirectional detection sensor 43 is turned on. That is, the leading edge of the recording medium (OHP film) conveyed by the fixing roller 40a toward the discharge roller 40b is detected by the detection lever 43 of the bidirectional detection sensor 43.
It is monitored whether c has been rotated counterclockwise in FIG. 1 (step 7). If it does not turn on, monitoring continues until it does.

Next, it is monitored whether the bidirectional detection sensor 43 is turned off. That is, it is monitored whether the recording medium has passed the bidirectional detection sensor 43 and the detection lever 43c has returned to the position where it blocks the detection beam (step 8). If it does not turn off, monitoring will continue until it does.

In step 8, when the bidirectional sensor 43 is turned on, the drive motor is immediately reversed by reducing the transport speed via the motor drive circuit 51 (step 9). At this time, the rear end of the recording medium is held between the paper discharge rollers 40b.

Then, monitoring continues until the bidirectional detection sensor 43 is turned on (step 1.0).

When the bidirectional detection sensor 43 is turned on, it means that the recording medium is conveyed in the opposite direction, and the recording medium is transported by the fixing roller 4.
Second fixing is performed at 0a (step 1).

Next, it is monitored whether the bidirectional detection sensor 43 is turned off. That is, it is monitored whether the recording medium has passed the bidirectional detection sensor 43 and the detection lever 43c has returned to the position where it blocks the detection beam (step 12). here,
If it does not turn off, continue monitoring until it does.

Then, the conveyance in the reverse direction is further continued for a certain period of time (T) (step 13). Here, the recording medium is held on the conveying section 41 with the rear end thereof being held between the fixing rollers 40a.

Next, the drive motor is rotated forward (step 14), and fixing is performed three times (step 15).

Monitoring is then continued until the bidirectional detection sensor 43 is turned on (step 16).

Next, it is monitored whether the bidirectional detection sensor 43 is off, that is, whether the recording medium has passed the bidirectional detection sensor 43 (step 17).

Then, the drive motor continues to transport the recording medium in the normal rotation direction for a certain period of time (T2) until the recording medium is discharged to the outside of the apparatus by the paper discharge roller 40b (step 18), and then the series of operations ends.

According to such a configuration, fixing is performed in step 6.11.15.
By repeating this process three times, the toner can be completely melted and an OHP film with good color reproducibility can be obtained without providing any special fixing device.

Further, since almost no bending force is applied to the recording medium when fixing is performed three times, there is no problem such as the toner image peeling off from the recording medium.

(Effects of the Invention) As described above, according to the present invention, a bidirectional detection sensor that detects conveyance of a recording medium from both directions is disposed between the fixing roller in the fixing unit and the paper ejection roller, and the bidirectional detection sensor By providing a control means for switching the conveyance of the recording medium between forward and reverse directions in response to a signal from the sensor,
A color image forming apparatus capable of forming a toner image with good color reproducibility on an OHP film can be realized.

[Brief explanation of the drawing]

In these figures, FIG. 1 is a configuration diagram illustrating an embodiment of the present invention, a perspective view of the main parts of the bidirectional detection sensor shown in FIG. 1, and FIG. 3 a control block diagram of the main parts in FIG. FIG. 4 is a diagram illustrating the flow of the color image forming apparatus shown in FIG. 1, and FIG. 5 is a block diagram illustrating the conventional color image forming apparatus.

Claims (1)

[Scope of Claims] A charging section that uniformly charges the surface of the photoreceptor, an exposing section that forms an electrostatic latent image of each color on the photoreceptor based on image signals of a plurality of colors, and an electrostatic latent image formed from the electrostatic latent image. A developing section that forms a toner image using toner of a corresponding color, a paper feeding section that feeds the recording medium, and a toner image formed of toner of all colors onto the recording medium fed from the paper feeding section. a transfer section that transfers the image; a separation section that separates the recording medium from the photoreceptor; a fixing section that fixes the toner image on the recording medium; and a conveyance section that conveys the recording medium from the separation section to the fixing section. In the color image forming apparatus, a bidirectional detection sensor for detecting conveyance of a recording medium from both directions is disposed between the fixing roller and the paper ejection roller in the fixing section, and a bidirectional detection sensor that detects the conveyance of the recording medium from both directions is provided. A color image forming apparatus, further comprising a control means for switching the conveyance of the recording medium between forward and reverse directions.