JPS6247669A - Image forming device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Object of the Invention (Field of Industrial Application) The present invention relates to an image forming apparatus using an electrostatic transfer process, such as an electrophotographic copying machine.

(Industrial Application Field) The present invention relates to an image forming apparatus that uses an electrostatic transfer process, such as an electrostatic copying machine.

(Prior Art and Problems to be Solved) In this type of image forming apparatus, the distance between the transfer site and the fixing site of the image forming mechanism is generally the length seen in the conveyance direction of the sheet-like transfer material, mainly paper. It was normal for the height to be approximately equal.

This is the difference between the generatrix of the rotating cylindrical photosensitive drum used as an image carrier and that of the fixing roller in standard devices that use a pair of pressure rollers that have been widely used in the past (including those equipped with heating means). If there is a twist between In this case, the gripping force on the transfer material at the fixing site is much larger than the restraining force on the transfer material at the transfer site, resulting in traction, skewing, etc., resulting in transfer misalignment,
This is because there is a risk that image distortion may occur.

These drawbacks are particularly noticeable in pressure fixing devices because of the large amount of shuffling that occurs when the transfer material enters the device.

In addition, in color image forming apparatuses, accurate overlay of each image is required for multiple transfer, so it is better to make the distance between the transfer site and the fixing site longer than the length of the transfer material. −
' was through.

Due to the above-mentioned circumstances, the necessary distance between the two parts inevitably becomes an obstacle to miniaturization of the image forming apparatus.

FIG. 6 is a schematic diagram of a typical example of a conventionally well-known copying machine, in which the transfer material taken out from the cassette 4 advances in the direction of arrow X and approaches the photosensitive drum 3. The image is then transferred to a transfer site equipped with a transfer charger 4, and further to a fixing device 5 equipped with a pair of fixing rollers having a nip portion 5a. In such a device, the transfer material is the transfer site 2a.
Since they are restrained with different forces by the nip portion 5a and the nip portion 5a, it was necessary to keep a sufficient distance between them as described above.

As a means to avoid such disadvantages, the speed of the transfer material at the fixing site is made slower than the speed at the transfer site to form a loop in the transfer material between the two sites, thereby eliminating the above-mentioned disadvantages. Some attempts have already been made to do so, but nothing satisfactory has yet been achieved.

In other words, such a material not only cannot avoid the traction effect at the beginning, but also the loop gradually becomes larger and eventually springback occurs due to the elasticity of the transfer material itself, causing the rear part of the transfer material to It has not been possible to obtain a device that exhibits a stable function due to the fact that it retreats and causes transfer misalignment.

The present invention has been made in view of the current situation, and eliminates the above-mentioned drawbacks by ensuring a constant loop from the beginning of transferring the transfer material and maintaining the size of the loop, and achieves miniaturization. The purpose of the present invention is to provide an image forming apparatus that can

(2) Structure of the Invention (Technical Means for Solving the Problems and Their Effects) In order to achieve the above-mentioned object 1, the present invention provides a transfer system at a transfer site and a fixing site in an image forming apparatus as described above. The material is conveyed at almost the same speed, and a constant loop is formed between the two from the beginning, and this loop is maintained thereafter.

With this configuration, the impact applied to the transfer material at the fixing site does not affect the transfer site at all, making it possible to obtain a stable image.

(Explanation of Embodiments) FIG. 1 is a schematic explanatory diagram of the case where the present invention is applied to a known electrophotographic copying machine, in which one sheet is taken out from a cassette 4 installed in the main body L. The transfer material (not shown) passes through the conveyance path 41 to the transfer site 2a, receives the toner image, and passes through the upwardly convex path 6 to the fixing device 5.
to the nip portion 5a. Therefore, the transfer material separated from the photosensitive drum 3 and conveyed forms a predetermined loop through the path 6 and reaches the nip portion 5a.

Near the nip portion, means for detecting the transfer material, such as photointerlab toughs a and 7b, are arranged. Reference numerals M1 and M2 in the figure are motors that drive the photosensitive drum 3 and the pair of fixing rollers 5.

” To summarize the operation of the two-legged device, when the transfer material carrying the toner image and advancing passes through the convex path 6 and reaches the nip portion 5a of the fixing device, the photo inerter rapter 7a is moved at that position. , 7b detects its presence, and the fixing roller temporarily stops. Then, after a certain period of time,
The fixing roller is activated again and starts conveying the transfer material.

As mentioned above, by keeping the speeds of the transfer site and the fixing site approximately the same, the transfer material will proceed in a loop from then on, so the state of the transfer material at the fixing site will be absorbed by the aforementioned loop. Since it does not reach the transfer site, high quality images can be obtained.

FIG. 2 shows the control mechanism of the image forming apparatus according to the present invention, in which the input signal 8 of the microprocessor 9 is the output signal of the sensors 7a and 7b, and becomes high when a transfer material is detected. At that time, it becomes low state. Further, when the microprocessor 9 output signal 10 is in a high state, the motor M2 is activated to drive the fixing roller.
When it is in a low state, it is stopped.

FIG. 3 is a flowchart for controlling each signal in FIG. 2 by the microprocessor 9.

Reference numeral 21 is a step of waiting until the transfer material passes the sensor position and the input signal becomes high.

Reference numeral 22 sets the output signal 10 to a low state in order to stop driving the fixing roller F. Reference numeral 23 indicates a step in which a timer in the microprocessor is turned on after the drive motor of the fixing roller is stopped.

Reference numeral 24 is a step in which the fixing roller stops, the transfer material also stops, and a time is prepared for forming a loop thereafter.

Reference numeral 25 is a step of turning off the timer after the above-mentioned time has elapsed.

Reference numeral 26 is a step that sets the output signal to a high state in order to activate the drive motor of the fixing roller.

Reference numeral 27 is a step in which the transfer material passes through the sensor and the output signal 8 is set to a low state.

Since the fixing roller stops only when the transfer material reaches the fixing roller, the above method is suitable for heating and pressure type fixing devices that require uniform heating of the entire surface of the fixing roller. be.

FIG. 4 shows an embodiment in which no other control method is used, and reference numeral 31 is a step for waiting for the input signal to become high when the transfer material reaches the level of -1 level at the sensors 7a and 7b. .

Reference numeral 32 is a step of turning on the internal timer of the microprocessor 9.

Reference numeral 33 is a step of waiting for time to form a loop in the transfer material.

Reference numeral 34 is a step of turning off the timer of the microprocessor 9 after a predetermined period of time has elapsed.

Reference numeral 35 indicates an output signal 10 for driving motor M2.
Steps to get high.

Reference numeral 36 is a step for waiting for the transfer material to pass through the sensor and for the input signal 8 to become low.

Reference numeral 37 is a step of turning on the timer of the microprocessor 8 after the transfer material passes.

Reference numeral 38 is a step for waiting for a certain period of time to elapse from when the transfer material passes the sensor until it leaves the fixing roller.

Reference numeral 39 is a step of turning off the internal timer of the microprocessor after the time has elapsed.

Reference numeral 40 indicates an output signal 1 to stop the motor M2.
This is the step of making 0 low.

In this embodiment, since the roller operates only when the transfer material is at the position of the fixing roller, in an image forming apparatus in which the transfer material is often not supplied after the power is turned on,
Power consumption is saved.

It goes without saying that the times of step 24 in FIG. 3 and step 33 in FIG. 4 are appropriately determined depending on the elasticity and stiffness of the transfer material.

Since the present invention has the configuration described below, the total length of the image forming apparatus can be significantly shortened, and the total length L1 of the image forming apparatus shown in FIG. The length L2 is approximately 0.6.

Next, an example in which the present invention is applied to a color copying machine will be described.

Figure 5 shows a single-drum type color copying machine,
A developing device 9 that is rotatably supported and has four developing devices 9Y (yellow), 9M (magenta), 9C (cyan), and 9B (black) each containing toner of four colors, and toner of each color. a photosensitive drum 3 that forms an image;
It is equipped with a transfer drum 8 made of an insulating screen or film.

The transfer material (not shown) taken out from the cassette 4 attached to the main body 1 reaches the transfer drum 8, is attracted to the drum 8 by the action of the pair of adsorption chargers 8a and 8b, and is transferred to the transfer charger 8C. It leads to the transcription site with

During this time, as is well known, the electrostatic latent image formed on the photosensitive drum 3 by the charger and image forming means (not shown) for forming the optical image of the document is transferred to the developing device 9Y, etc. The resulting color is developed and transferred to a transfer material at a transfer site having a transfer charger 8C. The transfer material is reinforced with the adsorption action to the transfer drum by the adsorption charger pair 8C18d, and after repeating the above-mentioned transfer action to form a colored image, it passes through the transport path 6, passes through the fixing device 5, and is discharged to the outside. Ru.

In such a device, the conveyance path 6 is formed in a convex shape as shown in FIG. 1, and the detection means 7a, 7b
By arranging the transfer material, the transfer material can be controlled in exactly the same way as in the case described above. Note that the reference numeral 8e in the figure is a neutralizing charger, and the adsorption charger pair 8C18d functions to prevent shock from the fixing site from being transmitted to the transfer site.

As mentioned earlier, in a color image forming apparatus, the distance between the transfer site and the fixing site (indicated by the symbol d in Fig. 4) is usually set to be longer than the length of the transfer material in the running direction. , by forming the distance #, d as in the present invention, the total length L3 of the device can be reduced by approximately 7
It can be reduced to 0%.

FIG. 6 shows a case where the present invention is applied to a color image forming apparatus in which a plurality of image forming means are arranged in a row.

Inside the casing 1, there is disposed a bandless belt v made of an insulating screen mesh or film, which is wound around rollers Ra, RB, and Rc, and runs in the direction of the arrow in the figure. A developing device 1 that forms cyan, magenta, yellow, and black images along the belt, respectively.
0C, 10M, IOY, and IOB are arranged.

Reference numerals 11C, IIM, IIY, and IIB are image signal applying means including, for example, semiconductor lasers, polygon mirrors, etc., which apply color-separated image signals to the photosensitive drum 12C, etc., and apply the image signals to the belt V by the action of the transfer charger 16C, etc. Color images are sequentially formed on the image, and the color image completed after passing through all the developing devices is separated from the belt v by the action of the separation charger 15, passes through the conveyance path 6, and is fixed by the fixing device 5. It is then discharged outside.

Incidentally, reference numerals 13a, 13b; 14a, 14b, etc. in the drawings are suction chargers similar to those shown in the previous embodiment, which prevent the transfer material from slipping back.

In such an apparatus, a convex conveyance path 6 and detection means 7a, 7b are formed between the separation site and the fixing site, and as in the case of each of the above embodiments, the transfer material is uniformly distributed. It will progress while forming a loop.

When comparing the device described above with a known device that feeds the transfer material from the transfer site to the fixing site using a conveyance path that is straight and longer than the conveyance path, the length is approximately 80% of the known device. It will be.

It will be easily understood that the charger for adsorbing the transfer material in the embodiment shown in FIGS. 5 and 6 can also be applied to the embodiment shown in FIG.

(3) Effects of the invention Since the present invention has the configuration as explained above,
This greatly contributes to the miniaturization of image forming apparatuses that utilize electrostatic transfer processes without adversely affecting images.

In particular, when applied to a color image forming apparatus, it not only contributes to miniaturization of the apparatus itself, but also effectively prevents positional shift during multiple transfer, and greatly contributes to obtaining high-quality images.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram of the main parts of an image forming apparatus according to an embodiment of the present invention, FIG. 2 is a block diagram without showing the control mechanism, and FIG.
The figure is a flowchart showing the operation, and FIGS. 5 and 6 are schematic explanatory diagrams showing other embodiments. FIG. 7 is a schematic side view of a known image forming apparatus. 311...Photosensitive drum, 5...Fixing device 8 work 11
11 Transfer drum 7a17b+1...Detection means (sensor) 9...Fog developing device Fig. 1 Fig. 2 Fig. 6 Fig. 7

Claims (1)

[Claims] In an image forming apparatus that travels in synchronization with a traveling image carrier to transfer an image on the surface of the image carrier onto a transfer material, the transfer material is conveyed to a pair of fixing rollers that are in pressure contact with each other. The image forming apparatus is configured to stop the transfer material for a predetermined period of time to form a loop when the transfer material reaches the fixing roller pair.