JPH0391787A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent malfunction from generating even when leaked light from a flash light emission is detected by an optical detecting part by asking output of the optical detecting part for a specified time from the flash light emission time of a flash fixing part. CONSTITUTION:In the image forming device provided with an image forming part 1 which forms a pulverous image on a printing medium CP, a flash fixing part 2 which falshes and fixes the pulverous image on the carried printing medium CP, and the optical detecting part 4 which detects the printing medium CP on a medium carrying path, a control part 5 which controls the action of the flash fixing part 2 and carries out observation of the carrying of the printing medium CP from the output of the optical detecting part 4 maskes the output of the concerned optical detecting part 4 for the specified time from the time of the flash light emission at the flashing fixing part 2. Thus even when leaking of light is detected by the optical detecting part 4 at the time of flash emission at the flash fixing part 2, the output is made ineffective, and malfunction can be prevented.

Description

[Detailed description of the invention] [Table of contents] Overview Industrial field of application Prior art (Figure 6) Means for solving the problem to be solved by the invention (Figure 1) Working example (a) 1 Description of Examples (Figures 2 to 5) (c)
Description of other embodiments Effects of the invention [Summary] Regarding an image forming device that fixes a powder image on a print medium by emitting light from a flash lamp, an optical detection unit detects light leakage from a flash fixing unit. In order to prevent malfunctions due to In an image forming apparatus having an optical detection section that detects a print medium, a control section that controls the operation of the flash fixing section and monitors the conveyance of the print medium based on the output of the optical detection section is configured to detect the flash fixation section. The output of the optical detector is masked for a predetermined period of time after the flash is emitted. [Industrial Application Field] The present invention provides the following advantages:
The present invention relates to an image forming apparatus that fixes a powder image on a print medium.

In image forming devices such as electrophotographic devices and electrostatic recording devices, an electrostatic latent image is formed on a photoreceptor or a printing medium, and this electrostatic latent image is developed into a powder image using a powder developer. In electrophotographic devices, a powder image on a photoreceptor is transferred onto a print medium.

A flash fixing method is used to fix the powder image on the print medium using the inner tip of a flash lamp.

In an image forming apparatus using such a flash fixing method, consideration must be given to prevent the internal flash light from adversely affecting the operation of the apparatus.

[Conventional technology]

FIG. 6 is an explanatory diagram of the prior art.

The powder image formed on the photosensitive drum of the image forming unit 1 is transferred onto the printing medium (hereinafter referred to as paper) CP that is transported by the transport roller 3, and the powder image on the paper CP is transferred to the flash fixing unit 2. is fixed with flash.

An optical sensor 4 is provided on the exit side of the flash fixing section 2 to detect the ejection of the print medium CP from the flash fixing section 2, and the output of the optical sensor 4 indicates the completion of ejection of the print medium CP. Detect.

[Problem to be solved by the invention]

By the way, in the flash fixing method, the powder is melted and fixed by the light energy generated by the radiant heat of the light, so it emits intense light.

For this reason, light leakage occurs in the flash fixing section 2 when the flash is emitted, and this is sensed by the optical sensor 4 at the entrance and exit of the flash fixing section 2, resulting in a problem of erroneously detecting the paper CP.

For example, if the optical sensor 4 on the exit side emits a flash when there is paper, it will detect that there is no paper due to the leakage, and even if a paper jam occurs in the flash fixing unit 2, it will not be able to complete the ejection. This will result in false positives.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an image forming apparatus that can prevent malfunctions caused by an optical detection section detecting light leakage from a flash fixing section.

[Means to solve the problem]

FIG. 3 is a diagram showing the principle of the present invention.

As shown in FIG. 1, the present invention includes an image forming section 1 that forms a powder image on a printing medium CP, and
In an image forming 1fc device having a flash fixing section 2 for flash fixing the above powder image, and an optical detection section 4 for detecting the print medium CP on the medium conveyance path, the flash fixing section 2 is operated and controlled. , a control unit 5 that monitors the conveyance of the print medium CP based on the output of the optical detection unit 4;
However, the output of the optical detection section 4 is masked for a predetermined period of time after the flash fixing section 2 emits the flash.

[Effect]

In the present invention, since the output of the optical detection section 4 is masked for a predetermined period of time after the flash fixing section 2 emits the flash,
Even if the optical detection section 4 detects light leakage due to flash emission, its output becomes invalid, thereby preventing malfunctions.

In addition, in order to block light leakage, it is possible to provide a protective wall at the light receiving part of the optical detection part 4 or to detect light from the light emitting part, but the structure becomes complicated and the mounting precision must be high. . Similarly, it is conceivable to set the sensing wavelength in the detection 8 outside the flash emission wavelength band, but this would require the use of a special sensor and would be expensive.

Therefore, the present invention can easily and inexpensively prevent malfunctions caused by light leakage. [Embodiment] (a) Description of one embodiment FIG. 2 is a block diagram of one embodiment of the present invention.

In the figure, the image forming section l is organized in the electrophotographic printing section and has the following structure. The photosensitive drum 10 is made of a photoconductive material such as OPC, and is rotated in the direction of the arrow.The front charger 11 charges the photosensitive drum 10.The image exposure section 1
2 is composed of a pair of LED arrays 12a and 12b, which performs image exposure on the photosensitive drum 1O, and a developing device I3 is used to develop the electrostatic latent image on the photosensitive drum 10 with a powder developer; A transfer charger l4 is used to transfer the powder image on the photosensitive drum 10 onto paper, a static eliminator l5 is used to remove static electricity from the photosensitive drum 10, and a cleaner 16 is used to remove static electricity from the photosensitive drum 10. This is for cleaning the drum 10.

The flash fixing unit 2 is composed of four flash lamps, which emit light at the same time to irradiate a predetermined area with flash.

The paper transport unit 3 transports paper (print media) along a predetermined transport bus, and includes transport rollers 30, 3l,
A standby roller 32 that waits the paper in front of the transfer charger l4, a peeling roller 33 that peels the transferred paper from the photosensitive drum IO and conveys it, a guide plate 34 that guides the peeled paper, and a flash fixing unit 2. It includes an introduction port 35 for introducing paper into the holder, a suction transport section 36 facing the flash fixing section 2 for suctioning and transporting the paper, and a discharge port 37.

On the paper conveyance path, in order to detect the paper, there are light transmissive paper sensors 4a to 4a whose light-emitting part and light-receiving part face each other across the path.
4C is provided.

The write timing sensor 4a detects the paper and
The fixing timing sensor 4b, which is used to create the writing (image exposure) timing of the D arrays 12a and 12b, is
A discharge sensor 4c is provided between the transfer charger 4 and the flash fixing unit 2 to detect paper and create a flash emission timing for the flash fixing unit 2. The purpose is to detect the emissions of

Briefly explaining the operation of the above configuration, when paper is conveyed and detected by the write timing sensor 4a, the LED
The arrays 12a and 12b perform writing, and the photosensitive drum 10
to form an electrostatic latent image.

The paper is further conveyed, and after waiting for a predetermined time by the standby roller 32, the sheet is conveyed by the standby roller 32 so as to be synchronized with the powder image on the photosensitive drum IO developed by the developing device 13, and the powder is transferred by the transfer charger 14. The image is transferred.

The photosensitive drum 10 is neutralized by a static eliminator 15 and cleaned by a cleaner l6.

On the other hand, the paper is peeled off from the drum by a peeling roller 33 and conveyed along a guide plate 34.

When the fixing timing sensor 4b detects paper, a fixing timing signal is generated to control the flash fixing section 2, as will be described later.

The paper is flash-fixed while passing through the flash fixing section 2 by an inlet roller 35 and a suction conveyance section 36, and then discharged by a discharge roller 37.

FIG. 3 is a block diagram of an embodiment of the present invention.

i1i? The f1 section 5 has a main control section 5a and a light emission control section 5b.

Lord if JI? The i1 section 5a includes a microprocessor (MP
U), in response to the paper detection signal PS1 from the fixing timing sensor 4b, outputs a charge-on signal *CHON to the light emission control unit 5b, and in response to the charge OK signal *CHOK from the light emission control unit 5b, In addition to outputting the trigger signal TRG to the light emission control section 5b to perform flash fixing control, the timer TM1 is used to control the mask %lJ? 11L, and a timer TM2 is used to control the transport.

The light emission control unit 5b charges the internal capacitor according to the charge-on signal *CH○N, and when a certain amount of charge is reached, the charge OK signal *C H O K is sent to the main control unit 5a.
The trigger electrode 2I of the flash lamp 20 is triggered to emit light in response to the trigger signal TRG from the main control section 5a.

FIG. 4 is a processing flow diagram of an embodiment of the present invention, and FIG. 5 is an explanatory diagram of the operation of an embodiment of the present invention.

■ As shown in Figure 4 (A), the fixing tying sensor 4b
When the paper detection signal PS1 is outputted as an interrupt to the main control unit (hereinafter referred to as MPU) 5a, the MPU 5a outputs a charge-on signal *CHON after T time has elapsed to instruct flash charging.

As a result, the light emission control unit 5b charges the capacitor for α time.

Here, the α time is the time required for the capacitor to accumulate the amount of charge necessary for light emission.

■ The MPU 5a waits for the charge OK signal *CHOK from the light emission control section 5b. , when there is a charge OK signal *CHOK, the MPU 5a sends a trigger signal T to the light emission control unit 5b after (T+α) time from the output of the paper detection signal PS1.
Output RG.

Thereby, the light emission control section 5b triggers the trigger electrode 2l to cause the flash lamp 20 to emit light.

Note that the (T+α) time is the time required for the leading edge of the paper CP to reach the exit of the flash fixing section 2 from the sensor 4b. ■ Along with the output of this trigger signal TRG, the MPU5
a starts the masking timer TMI for the timer over time t, and ends the series of processing.

Then, the flash fixing control based on the sensor 4b ends. Next, processing based on the output of the sensor 4C will be explained with reference to FIG. 4(B) and FIG. 5.

- When there is a change in the output of the discharge sensor 4C, the MPU 5a starts the process shown in FIG. 4(B) by an interrupt. First, the MPU 5 a detects that the output of the discharge sensor 4 c rises (
(change point from no paper to paper present).

■ If the output of the output sensor 4c rises, the paper CP has reached the sensor 4c, and the paper CP has entered between the light emitting part and the light receiving part of the sensor 4C, so the MP tJ5a starts the transport timer TM2 for jam detection. Start and complete a series of processing.

Here, in the light transmission type sensor, when the paper CP exists between the light emitting part and the light receiving part of the sensor, the emitted light from the light emitting part to the light receiving part is cut off, and the paper CP is output at a high level. If the light receiving section does not exist between the light emitting section and the light receiving section, the light receiving section receives the emitted light from the light emitting section and outputs the light at a low level.

■ On the other hand, if the output of the discharge sensor 4c is falling, the MPU
5a checks the masking timer TMI to determine whether masking is in progress.

Since the masking timer TMI counts a predetermined masking period t from the start of light emission and issues a time-over output, the timer TMI that is counting is currently masking.

If the masking timer TMI does not issue a time-over output, the MPU 5a determines that the masking period is in progress, ignores the output of the discharge sensor 4c, and ends the process.

■ If the mask period is not in step ■, the MPU5a
checks the transport timer TM2.

The transport timer TM2 is set with a scheduled time from when the leading edge of the paper reaches the sensor 4c to when the trailing edge of the paper passes the sensor 4c, and outputs a time-over signal when the scheduled time has passed.

Therefore, if the transport timer TM2 has not timed out, the MPU 5a determines that the ejection has been completed normally and ends the process. On the other hand, if the transport timer TM2 has timed out, the MPU 5a assumes that there is a transport failure (paper jam) and stops the operation.

In this way, as shown in FIG. 5, the paper detection output of the discharge sensor 4c is masked during the masking period t determined by the masking timer TMI from the start of flash emission.

During this mask period t, the sensor 4c
For example, t may be slightly longer than ms with respect to the light leakage influence time ts. Specifically, if t o = 9 ms, in the embodiment, t
Since s is about 3ms, it is sufficient to set L=6ms. In this manner, even if the light receiving section of the sensor 4C senses leakage and erroneously detects paper present as no paper when the flash is emitted, malfunction due to the erroneous detection is prevented. (b) Description of other embodiments In the embodiments described above, the image forming section is an electrophotographic printing section, but other known powder image forming means may be used, and the optical detection section 4 may also be used. Although the example of the stray sensor 4C on the exit side of the flash fixing section 2 has been described, it may be a sensor on the population side, such as the sensor 4b, and in short, any sensor at a position affected by flash emission may be used. Further, the masking operation of the sensor output is executed by the firmware of the MPU 5a, for example, the masking timer TM
This can also be realized by separately providing a prohibition circuit that prohibits output to the MPU 5a by the output of I.

Furthermore, an interrupt may be generated when the transport timer TM2 times out, and the operation may be stopped.

Although the present invention has been described above using examples, the present invention can be modified in various ways according to the gist of the present invention, and these are not excluded from the present invention.

〔Effect of the invention〕

As explained above, according to the present invention, (1) By masking the output of the optical detection section 4 for a predetermined period of time from the time when the flash fixing section emits the flash, the optical detection section 4 detects light leakage due to the flash emission. too,
■ Since the output of the optical detection section 4 is simply masked, there is no need to use a special Ja structure or special element for the detection section 4.
Another effect is that malfunctions due to light leakage can be easily and inexpensively prevented.

[Brief explanation of drawings]

Fig. 1 is a principle diagram of the present invention, Fig. 2 is a structural diagram of an embodiment of the invention, Fig. 3 is a block diagram of an embodiment of the invention, and Fig. 4 is a processing flow diagram of an embodiment of the invention. , FIG. 5 is an explanatory diagram of the operation of one embodiment of the present invention, and FIG. 6 is an explanatory diagram of the prior art. In the figure, 1-image forming section, 2-flash fixing section, 4-optical detection section, 5-control section, cp--printing medium.

Claims (1)

[Claims] Image forming unit (1) that forms a powder image on a print medium (CP)
a flash fixing unit (2) that flash-fixes a powder image on the conveyed print medium (CP); and an optical detection unit (4) that detects the print medium (CP) on the medium conveyance path. In the image forming apparatus, the flash fixing section (2) is operated and the printing medium (CP) is controlled by the output of the optical detection section (4).
An image forming apparatus characterized in that a control section (5) that monitors the conveyance of the image forming apparatus masks the output of the optical detection section (4) for a predetermined period of time from the time when the flash fixing section (2) emits a flash.