JPS6187180A - Printer - Google Patents

Abstract

PURPOSE:To separate a transfer material from a photosensitive body efficiently and to prevent the photosensitive body from retransfer in a printer such as a laser beam printer by detecting a video signal and impressing a destaticizing voltage from a separation electrifier only to a non-picture area. CONSTITUTION:High voltage of -5.0kV is applied from a high voltage power supply 18 for transfer to a transfer electrifier 16 to electrostatically charge the transfer material 21 with reverse polarity against the polarity of toner. Simultaneously with transfer of a toner image to the transfer material 21, the transfer material 21 electrostatically adhered and held to/on the surface of a photosensitive body. When the transfer material 21 reaches a separation/ destaticizer, the transfer material 21 is destaticized by receiving separation corona discharge obtained by superposing a positive DC voltage to 5.0kVrms AC. When said destaticizing is continued from the detection of the initial picture data on a video signal for a fixed period and then the supply of the high AC voltage is stopped, corona discharge is also stopped, so that the transfer material 21 is not destaticized after the reception of the initial picture data. Therefore, a transfer picture having stable picture quality can be obtained in the picture area without the influence of destaticizing.

Description

Detailed Description of the Invention [Technical Field] The present invention relates to a printing device such as a laser beam printer that scans a photoreceptor with a light beam corresponding to an image signal to form a latent image. In particular, it relates to a printing device using an electrostatic separation method in which alternating current corona discharge is applied from behind the transfer material electrostatically adsorbed to the photoreceptor as a separation method for separating the transfer material from the surface.

[Prior Art] In the method of separating the transfer material and photoreceptor by applying a high-voltage alternating current voltage high enough to peel the transfer material from the surface of the photoreceptor to remove the electric charge on the transfer material, the transfer material and the photoreceptor are separated from each other. Therefore, there is a problem in that the toner once transferred to the transfer material is transferred again to the surface of the photoreceptor. Methods taken in the prior art to solve the above problems include a method of superimposing a DC bias voltage on the AC voltage, and a method of removing static electricity only from a certain area from the leading edge of the transfer material, and removing static electricity from the rest of the area. The solution was to stop it.

However, in the method of superimposing a DC voltage on an AC voltage, in order to simultaneously achieve the different purposes of preventing transfer material peeling and toner re-transfer, it is necessary to select the optimal DC applied voltage for transfer material peeling and to prevent re-transfer. It is necessary to take a compromise method of applying a voltage value intermediate between the DC applied voltage that is optimal for prevention, and as a result, peeling of the transfer material and prevention of re-transfer may occur due to changes in the environment or dirt on the static eliminator. The disadvantage was that it became unstable due to the influence of

Further, the method of eliminating static electricity only from the leading end of the transfer material has the following drawbacks. In other words, in order to ensure that the leading edge is peeled off more reliably, it is necessary to energize the separation static eliminator over a certain area, which is experimentally shown to extend beyond 2011II11 from the leading edge of the transfer material. . However, in the prior art, the current-carrying section of the separation static eliminator is fixed, which has associated drawbacks. Figure 1 (a), (b)
is a diagram for explaining the above-mentioned drawbacks. FIG. 1(L) is a diagram showing the temporal relationship between the transfer material, the image on the transfer material, and the application of the static elimination voltage. -A is an area where no image is formed on the transfer material, AY' is an area where an image is formed, and a static elimination voltage is applied only between X'' and P.
It is assumed that no static elimination voltage is applied between p and y. or,
As mentioned above, point P is a point beyond 20 m+w.

In the case of Fig. 1(a), even if the static electricity is not removed between P' and A,
Since there is no toner there, no retransfer occurs.

However, as shown in FIG. 1(b), when the image on the transfer material X-Y is formed between B-Y'', the static elimination voltage application time x''-p is fixed. , the charge is removed between the image B and P' on the transfer paper, and retransfer occurs in this area, making it impossible to obtain stable image quality.

[Purpose] The purpose of the present invention is to detect a video signal (image signal) and easily distinguish between a non-image area and an image area in a printing apparatus such as a laser beam printer. It is an object of the present invention to provide a printing apparatus in which the transfer material and the photoreceptor can be separated well and re-transfer does not occur, paying attention to the fact that the drawbacks of the prior art described above can be solved by applying .

[Example] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a configuration diagram of a laser beam printer which is an embodiment of the present invention. In the figure, 1 is a video signal, 2 is a laser driver, 3 is a laser generator, 4 is a laser beam, 5 is a polygon mirror, 6 1 is an f/θ lens, 7 is a mud detector, 8 is an optical path changing mirror, 1O is a photosensitive drum, 11 is a developer, L2 is a gear-shaped disc, and 13 is integrally attached to the gear-shaped disc 12. 14 is a temporary charger, 15 is a registration roller, 16 is a transfer charger, 17 is a separation static eliminator, 1
8 is a power source for the transfer charger, 19 is a voltage power source for separating static electricity removal of the separation static eliminator 17, 25 is a power source for a temporary charger, 20 is a paper feed roller, 21 is a transfer material, 22 is a paper feed cassette, 23 is a beam detect 30 is a video detection unit, 50 is a printing device control unit, 200 is an external device, 210 is a printing device control 5
0 and an external device 200.

A laser beam 4 is intermittently generated from a laser generator 3 in accordance with a video signal 1 based on print information. After the laser beam 4 is reflected by the polygon mirror 5,
The light is converged by the f/theta lens 6, reflected by the optical path direction changing mirror 8, and reaches the photosensitive drum 10. Here, main scanning is performed by rotating the polygon mirror 5, and the photosensitive drum 1
By rotating 0 in the direction of the dial, Q performs sub-scanning in a direction perpendicular to the main-scanning direction.

- Since the surface of the photosensitive drum 10 is uniformly charged by the corona discharge of the next charger 14, the laser beam 4
As is known, when the photosensitive drum 10 reaches the photosensitive drum 10, only that portion is electrically neutralized and a latent image corresponding to the video signal l is formed. Amorphous silicon is used as the body, and when it is positively charged by the -order charger 14 and a latent image is formed, the dark area potential Vd and bright area potential Vt in the developing section are different from each other, Vd = +400V, Vl = +50V.

Further, the peripheral speed at the surface of the photosensitive drum 10 is 180 am/sec. The latent image formed on the surface of the photoreceptor is reversely developed by the developing device it. That is, positively charged toner adheres to the bright area (the area where the video signal is turned on and the laser beam is irradiated) and is visualized.

A transfer material 21 fed from a cassette 22 by a paper feed roller 20 is sent by a registration roller 15 to a transfer charger 16 located 1lIllIIla from the photosensitive drum 21. The transfer charger 16 is supplied with -5, OKV from the transfer high voltage power supply 18.
A high voltage is supplied to charge the transfer material 21 to a polarity opposite to that of the toner. As the transfer material 21 passes over the transfer charger 16, the toner image is transferred onto the transfer material 21, and at the same time, the transfer material 21 is electrostatically held in close contact with the surface of the photoreceptor.

When the transfer material 21 reaches the separation static eliminator 17 which is 14 OiJi from the drum surface, it receives a separation corona discharge in which a positive DC DC voltage is superimposed on AC 5.0 KVr+++s, and the static electricity is removed. It is connected to the control circuit 50 so that it can be controlled according to the determination of the logical value of the video signal.

In this case, the discharge should be started before the leading edge of the transfer material reaches the separation static eliminator to ensure that the charge is removed from the leading edge of the transfer material even if there is a rise in corona discharge or variations in the feeding timing of the transfer material. is necessary.

Now, when a high voltage AC voltage is applied to the separation static eliminator 17,
The leading end of the transfer member receives corona discharge and begins to be neutralized. The key point of the present invention is to continue this static elimination for a certain period of time from the detection of the first image data on the video signal, and then stop the static elimination. When the supply of high-voltage AC voltage is stopped, the corona discharge also stops, so the transfer material after the first image data is sent will not be charged. Therefore, the image area will not be affected by the charge removal and the transferred image will have stable image quality. You will be able to obtain it.

In this way, when the leading end of the transfer material is first peeled off from the surface of the photoreceptor, the entire transfer material is sequentially peeled off due to its own weight and elasticity. At this time, high-pressure air may be blown onto the transfer material or suctioned by a vacuum peeling device as an auxiliary means.

Next, how to detect image data on a video signal will be explained. FIG. 3(a) is a diagram showing the exchange of signals between the video signal 1, the video detection section 3o, and the recording device control section 5o. In FIG. 3(a), the video detection unit 9o detects “°black” information (bit is true) in the video signal 11.
It is determined whether the video signal 11 is present or not.
Since it is usually binary value information, its discrimination is extremely easy. Detecting a video signal is meaningless unless the laser beam is properly irradiated onto the drum and the transfer material reaches a predetermined position, so the judgment condition for video signal detection is BD.
Signal 72. and vertical direction effective interval signal 76, BD
72 is a beam detect signal 23 detected by the beam detector 7 immediately before the laser beam 4 excited by the laser generator 3 scans the photosensitive drum 10, and is converted by the control unit 50, and the laser beam 4 is currently This shows that the photosensitive drum IO is effectively irradiated. Figure 3(b) shows the third
In the detailed diagram of the video detection unit 3o in FIG. Only when the transfer material is conveyed to a predetermined position, the video detection circuit 31 determines whether there is "black" information on the video signal l, and if there is "black" information, the controller 5o The video detection signal 62 is output as the video detection signal 62. Video detection signal 6
Upon receiving 2, the printing device control unit 5o enters an interrupt routine.
The 0N10FF timing of the separate high voltage power supply is determined.

Next, using FIG. 4(a), determine the timing of applying the separate static eliminator voltage to the separate static eliminator 17 between the photosensitive drum lO and the transfer material 2.
This will be briefly explained in relation to transportation. C is a position where the laser beam 4 is irradiated onto the photosensitive drum 10, and D is a position where the effect of corona discharge by the separation static eliminator 17 reaches the photosensitive drum 10. F is the position of the center of the registration roller 15 on the conveyance path. Now, consider the case where the distance on the drum circumference between D and 0 is not longer than the distance between D and F (fourth
Figure (a)), since the transfer material 21 must reach point D while the photosensitive drum lo rotates from point 0 to point D, the distance between C and D must be equal to the distance between D and E. When the transfer material reaches a certain point atE, it is necessary to send a video signal l from the external device 200 and start scanning the laser beam.

When the sending of the video signal 1 is started, it becomes possible to detect the "black" information, so if the "black" information is detected now when the leading edge of the transfer material 21 is conveyed to the position of point G, then
The "black" information is exposed onto C and becomes a toner image, so after the time required for the photosensitive drum lO to rotate from C to D, the G point on the transfer paper will be on the D point and the photosensitive drum lO will be Therefore, after the above-mentioned period of time after the "black" information is detected, the separate static elimination voltage power supply 19 is activated.
If this is stopped, the objective of the present invention will be achieved.

It goes without saying that the above-mentioned fixed time is the time required for the photosensitive drum IO to rotate from C to D minus the time required for the high-voltage power supply to be turned off and the corona discharge to disappear.

Next, to briefly explain the case where the distance between C and 0 is longer than the distance between D and F, in FIG. 4(b), the transfer material 2
1 is stopped at the registration rollers 15 (during this time, the transfer material 21 can be aligned with the registration rollers 15), and after the laser beam 4 starts scanning, the photosensitive drum 10 is moved to the distance between D and H and between D and F. It is only necessary to start driving the registration roller 15 when the distance has been rotated to a point II (2) where the distances are equal to each other. If information is detected, the black information will be formed on C, so it is only necessary to stop static electricity removal after the time required for rotation from C to D. -H, that is, even if the "black" information is detected before the registration roller 15 is driven, the situation is exactly the same, so no explanation will be given.

Although the above two positional relationships have been explained, in an actual laser beam printer, the positional relationship of the photosensitive drum 10 and the registration roller 15 is unchanged, so in the following explanation, the laser beam with the positional relationship shown in FIG. 4(a) will be explained. Let me explain about the printer.

Next, the control flow of the printing device control section 50 will be explained using FIG. 6.

FIG. 6 is a block diagram of the printing device control unit, where 51 is a microcomputer (CPU) that uses programs stored in ROM (read-only memory) and RAM (random access memory) installed inside (or outside) of the microcomputer (CPU). Performs overall control. Buffer 52 is a buffer that receives input interface signal t' from external device 200, and buffer 55 and driver 64 are buffers and drivers that send and receive signals from various parts within the printing apparatus. Driver 69 is external! ! This is a driver for sending output interface signals to 1200. interval timer 6
0 is the part that forms the timing necessary for the control flow, and C
The interval timer 60 forms the switching timing of the separated static eliminating voltage of the present invention, which is activated by the PU 51. The separated high voltage ON10FF 66 is a signal that turns the separated static eliminating voltage power source 19 ON10FF.

In FIGS. 5 and 6, the program of the CPU 51 starts when the printer is powered on, and step 10
In step 103, it is checked whether the temperature of the fixing device has risen to a predetermined temperature, and if one condition is satisfied, and the other conditions are also satisfied, in step 103, a state in which communication is possible is indicated to an external device. It is notified through the I READY signal 71. Therefore, this IREADY79 is “true” in the external device.
and there is information to be recorded, use IDRMST (
Drum rotation command) 53 is sent to the CPU 51, and the CPU 51
Then, upon receiving this signal (step l04), the drum transport motor 65 is turned on, and the high-voltage power supplies for the primary charger 14 and transfer charger 16 except for the separation static eliminator are turned on, and the surface potential on the drum surface is in a state where it is possible to record. (Step 10)
5).

When the state is ready for recording, the CPU 51 makes the signal of the IPREB 70 true through the redriver 69 and sends it to the external device (steps 106 and 107), and the state waits for the IPRNST 54 from the external device (step 108). ).

The external device inputs this IPREB78 to check whether the information has been developed in the memory and whether there are any abnormalities.If there is no problem, it transmits IPRNST54 (paper feeding command) to the recording device.

As a result, the CPU 51 drives the paper feed roller 20 through the driver 64 and turns the I PREB 70 into "true".
to enter the print sequence (steps 108, 109
).

From here on, the sensor 13 attached to the photosensitive drum 10
Since the drum clock 57, which is the output of the drum clock 57, is input to the CPU 51 through the buffer 55, the CPU 51 performs sequence control while knowing the position of the transfer material from the drum clock 57.

The transfer material 21 conveyed by the paper feed roller 20 eventually reaches the registration rollers 15 (step 110), and the transfer material 21 is aligned with the registration rollers 15. Although the positional relationship between the registration roller 15 and the photosensitive drum IO is as described above, the case where the distance C-DfJ] is shorter than the distance D-F will now be described. When the photosensitive drum lO rotates to a predetermined level (step 110), the registration roller 15 is driven to stop the paper feed roller 20 (step 111).As mentioned above, when the leading edge of the transfer material reaches two points, it is determined by the drum clock. 57 (step 112), the CPU 51 outputs ITOP 74 for one drum clock through the driver 69 to prompt the external device to send out the video signal l, and also outputs the vertical direction valid section signal 76 (hereinafter referred to as VENB). to be “true.”

At this point, the video detection section 30 starts operating, and the CPU 51 can be interrupted by the video detection signal 62. Also, the separation high voltage 0N10FF66 is turned on to start static elimination (steps 112 and 113).

When the external device receives ITOP74, it outputs the contents of the internal memory to the recording device as video signal 1. This is because the video detection unit 30 has started determining whether there is "black information" on the video signal 1. When the video detection signal 62 becomes true, the interrupt routine shown in FIG. 6(b) is entered.M
In the input routine, an internal timer is started for a certain period of time (
Step 120) Return to main control flow. As mentioned above, in the case of FIG. 4(a), the fixed time is the time required for rotation between C and 0. Main control flow (Figure 6(d)
), the print process continues while waiting for a timer interrupt to occur. During this process, a latent image will be formed on the photosensitive drum 10. Now, when the timer interrupt occurs, it is when the first image area reaches D. When a timer interrupt occurs, 7a- enters the timer interrupt routine shown in FIG. 6(C). In the timer interrupt routine, the separation high voltage 0N10FF66 is turned off to stop static elimination (step 131), and the process returns to the main control flow again. Thereafter, the image area on the transfer material is transported without being neutralized.

On the other hand, after processing the image signal for one page determined by the paper size signal 59 (step 114), the signal IPREND 73 indicating the end of the image section is sent to the external device as a real paper for one drum clock period through the dry input 69. Notify the end of one section.Also, at the same time, VENB 76 is false to predetermine the operation of the video detection unit 30 (step 115).
The transfer material is thus discharged through the fixing device 26. Even in the case of continuous copying, the processing from step 106 is repeated.

When recording is finished, the signal IDRMST53 from the external device, IP
When both RNSTs 54 become false, the drum conveyance motor 65, paper feed roller 20, and registration roller 15 are stopped after all the recording sheets are ejected.

In the method shown in the present invention, it is desirable that the stand-up time of the power source (type for separate static elimination) be quick, and if it is slow I/1, the recording interval will be spaced and time will be required, resulting in a drop in throughput.

As explained above, if we look at how the static elimination timing has been improved in Figure 1, we can see that in Figure 1 (a), the static elimination timing changes from ON to OFF at point A', and in Figure 1 (a), the static elimination timing changes from ON to OFF at point A'.
It is understood that in case b), the state changes from ON to OFF at point B'.

In the above embodiment, the laser beam printer is
Although the case where bright light is applied is shown, the same applies to the case where an LED array or OFT is used as the light source.

Furthermore, in the above embodiment, the operation of the separate static eliminator is controlled by turning on and off the control signal to the separate static eliminator voltage power supply 19, but as shown in FIG. A shutter plate 41 may be provided which is slid by a solenoid 42 to control the effect of the corona discharge of the isolator by moving the shutter plate in response to the video signal.

The control flow shown in FIG. 6 is explained when the photosensitive drum 10 and the registration roller 15 are in the positional relationship shown in FIG. 5(a), but will be explained when they are in the positional relationship shown in FIG. 4(b). FIG. 8 is a flow chart thereof. Step 108
, step 109 are the same as step 108 and step 109 in FIG. I PRNST5 from external device
4 becomes true, paper feeding starts (step 109).
), the transfer material 21 will eventually reach the registration rollers 15 (step 400), the paper feed roller 20 will be turned off and the transfer material 21 will be stopped at the registration rollers 15 (step 401). , 1200, ITOP 74 and VENB 76 are set to "true" to prompt the sending of the video signal l and activate the video detection circuit. In addition, the separation static eliminator 17 is activated (step 402).
), and in step 403, the interval timer 60 is activated to set the time required for the photosensitive drum 10 to rotate from the 0 point to the H point. Eventually, when the photosensitive drum reaches the H point, a timer interrupt occurs, so check whether the interrupt is from the H point in the interrupt routine shown in FIG. 8(C) (step 40).
4) If YES, the registration roller 15 is driven (step 405). When the registration roller 15 is driven, the transfer material 21 and the photosensitive drum 10 move in synchronization. The subsequent flow is the same as that described in FIG. 6, and will therefore be omitted.

Further, in the above embodiment, after the CPU 51 receives the video detection signal 62, the interrupt routine (FIG. 5(b)) is executed.
The interval timer 60 is started to generate a timer interrupt after a certain period of time, but since the certain period corresponds to a certain count of the drum clock 57, the interval timer 60 is not used and the video detection interrupt is generated. A counter may be set in the routine to count up every time the drum clock 57 is input, and when a predetermined count is reached, it may be determined that the image portion has reached a predetermined position.

[Effect] As is clear from the above explanation, by performing separate charge removal in the non-image area from the tip of the transfer material until the video signal (image signal) becomes true, and not performing separate charge removal only in the subsequent area. Stable image quality can now always be obtained in the image area without being affected by static elimination.

[Brief explanation of drawings]

FIGS. 1(a) and (b) are timing diagrams of the transfer/separation method. FIG. 2 is a block diagram showing an embodiment of the present invention. FIGS. 3(a) and (b) are timing diagrams of the transfer/separation method. An explanatory diagram of the video detection section; FIGS. 4(a) and 4(b) are positional relationship diagrams of the photosensitive drum and the registration roller; FIG. 5 is a block diagram of the control section of the apparatus implementing the present invention; FIG. 6(a) , (b) and (c) are diagrams showing flowcharts of an apparatus implementing the present invention. Figure 7 is a diagram of an example in which the effect of separated corona discharge is controlled by a shutter, and Figures 8 (a), (b), and (c) are diagrams of an example in which the photosensitive drum and registration roller are as shown in Figure 4 (b). It is a flowchart figure when there is a positional relationship. Here, l...video signal, 3... laser generator. 4... Laser beam, 7... Beam detector, lO.
...Photosensitive drum, 15...Registration roller, 16...
- Transfer charger, 17... Static elimination separator, 19... Voltage power supply for separation static elimination, 20... Paper feed roller, 21... Transfer material, 30... Video detection section, 50... Printing device control unit, C: laser beam writing point, D: point where the corona discharge effect of the separation static eliminator 17 reaches the photosensitive drum IO. Figure 1 (G) (b) Figure 3 (b) Figure 4 (0) Figure 4 (b)

Claims (2)

[Claims] (1) In a printing apparatus having means for forming a latent image by scanning a photoreceptor with a light beam corresponding to an image signal, and a transfer charger and a separation charge eliminator provided opposite to the photoreceptor, the image signal The method is characterized in that a non-image area on the transfer material is determined based on the timing of detection of image data therein, and a separation and neutralization voltage sufficient to separate the transfer material from the photoreceptor is applied only to the non-image area. Printing device. (2) From the detection time of the image data and the time required for the toner image of the image data on the photoreceptor to reach the separation static eliminator at the detection time, the non-image area of the transfer material on the separation static eliminator is determined. 2. The printing device according to claim 1, wherein the printing device is configured to distinguish the image portion from the image portion.