JPH03293677A - Image forming device - Google Patents

Abstract

PURPOSE:To obtain a recording image of high definition even when the body width of the paper to be recorded is varied by delaying recording timing of a second piece of the paper body when the paper width of the two paper bodies are varied. CONSTITUTION:Outputted signals 49 to 51 of sensors 46 to 48 by which the size of the paper on a tray 1 are detected are inputted to a control part 21. Light is transmitted through the paper on the tray in a vertical direction by these paper size detecting sensors and the paper width of four grades is detected by this signal. Thus the variation of the paper width vertical in the paper carry ing direction is detected, and when the paper size is varied from a narrow one to a wide one, a fixed time is imparted (printing of the wider size is delayed). Thus, a recorded image of the high definition with little density differ ence is obtained, and since there is no offsetting phenomenon to a fixing roll, the backside of the next piece of paper is not soiled.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an image forming apparatus using electrophotographic technology, and particularly relates to paper conveyance and printing (recording) control thereof.

[Conventional technology]

A conventional image forming apparatus is shown in FIG. In Figure 4, 1
is a paper feed tray, on which paper 2 is placed. Reference numeral 3 denotes a paper feed roller, which feeds the paper 2'' by rotating in the direction of arrow A. The paper feed roller 3 is turned on/off using a clutch mechanism (not shown).

The fed paper 2 hits the paper feed sensor lever 4, and a photointerrupter 5 generates a paper position signal.

6 is a photosensitive drum, which rotates in the direction of arrow B. Reference numeral 7 denotes an optical unit, in which a laser beam output from a laser chip is scanned by a polygon motor 8 and irradiated onto the drum 6 through a lens. Reference numeral 9 denotes a laser beam which is on/off modulated in accordance with the image signal to be printed (distributed).

10 is a charging roller for charging the surface of the drum 6 to a uniform potential. A developing sleeve 11 charges toner particles to one potential in order to spray the toner onto the drum 6.

Reference numeral 12 denotes a transfer roller for transferring the toner by applying ten potentials, and transfers the toner image that becomes a visible image on the drum to paper. The transferred paper is heated and pressurized by an upper fixing roller 13 and a lower fixing roller 14, and the toner is fixed. 15
is a halogen heater placed inside the upper fixing roller,
Keep the upper roller surface at a specified temperature.

The fixed paper is output onto the paper output tray 17 by the paper output roller 16 (the above conveyance path is indicated by arrow C). [Problems to be Solved by the Invention] In such an image forming apparatus, When continuous printing is performed and the paper used for printing changes from small size paper to large size paper, a defective image may occur in part of the image on the first page of the large size paper. . For example, when you switch to A4 size while printing continuously on B5 size paper, the density of the area in the axial direction of the drum where the paper has not passed before (the shaded area in Figure 5) becomes lighter. One reason for this is the difference in the electric charge charged per toner particle on the developing sleeve.The other reason is that a transfer roller is used, This is because potential memory occurs in areas where the paper has not passed, and the charging roller 6 does not uniformly charge the drum.

Furthermore, since there is a temperature difference between the temperature on the upper and lower fixing rollers between the part where the paper passed and the part where the paper did not pass (the part where the paper did not pass is 30 to 30 degrees higher than the predetermined control temperature). (The temperature is about 50° C.), an offset phenomenon occurs to the fixing roller, and the fixing roller becomes dirty.

An object of the present invention is to provide an image forming apparatus that solves the above problems.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides continuous feeding 2
A detection means for detecting the paper width of two sheets of paper, and a means for delaying the recording timing of the second sheet of paper when the width of the two sheets of paper changes based on the detection result of the detection means. Equipped with.

[Function] According to the present invention, changes in paper width perpendicular to the paper conveyance direction are detected, and for example, when the paper size changes from a narrow one to a wide one, the printer is made to wait for a certain period of time (the printing of a wide size is delayed). ), a high quality recorded image with little difference in density can be obtained. Furthermore, there is no offset phenomenon to the fixing roller (therefore, the back side of the next sheet will not be stained).

〔Example〕

FIG. 1 shows a block diagram of an embodiment of the present invention.

In FIG. 1, reference numeral 21 denotes a control section for controlling paper conveyance and printing of the image forming apparatus according to the present invention, and includes a control program ROM, a work area for control, a RAM serving as a register, and the like. A controller 22 is connected to an external host computer, converts image data input from the host computer into pixel data, and outputs it to the control section 21 as an image signal.

The control unit 21 and the controller 22 are mainly connected through five input/output signal lines. 23 is a signal (RDY) output from the control unit 21, and is a signal for notifying whether or not the image forming apparatus is in a printable state. 24 is a signal (P
RNT), and if this signal is true, the image forming apparatus rotates the paper feed roller 3 and starts and continues the printing operation.

25 is a TOP signal, which is output from the control section 21 in synchronization with the signal from the paper feed sensor photointerrupter 5.

When the controller receives the TOP signal 25, it suffices to subsequently output the image signal (VDP) 27 (vertical synchronization of images). Reference numeral 26 denotes an image horizontal synchronization signal (BD), which is output from the control section 21 to the controller 22.

A sensor 28 detects the presence/absence of paper on the tray 1, and sets a signal 29 to true when there is paper present. 30 is a paper feed sensor, which becomes true when there is paper in the sensor. 32 is a clutch for turning on/off the paper feed roller 3; when the control signal 33 is set to true, the paper feed clutch 32 is operated and the paper feed roller 3 is rotated.

34 is a charging roller 10. Developing sleeve 11. This is a high voltage unit for applying a predetermined high voltage to the transfer roller 12, and is controlled by control signals 35 (plurality) from the control section 21. 36, 37, and 38 are eight force lines to the charging roller 10, the developing sleeve 11, and the transfer roller 12.

39 is a thermistor that detects the temperature on the upper fixing roller 13, and its output signal 40 is sent to 8 by the A/D converter 41.
The data is input to the control section 21 as bit digital data 42.

The control unit 21 monitors the digital data 42 and outputs a heater control signal 43 to maintain a predetermined temperature, and the AC control unit 44 operates a relay to turn on/off the halogen heater 15 and perform fixing. Keep the roller surface temperature constant.

46 to 48 are sensors for detecting the size of paper on the tray 1, and are inputted to the control unit 21 as signals (49 to 51).

These paper size detection sensors transmit light vertically through the paper 2 on the tray, and detect four levels of paper width based on the signals.

A timing chart is shown in FIG. 2, and a flowchart is shown in FIG. 3.

In FIG. 2, the upper half of the chart shows that sheets of B5 size paper are placed on tray 1 one by one and printed continuously.

The control unit 21 checks the presence/absence of paper and the size of the paper (remove the checked paper width and store it in the register).
K, the RDY signal 23 is set to true (SL, S
2), the controller 22 sets the PRNT signal to true in S3), and in S4 judges whether the current paper width (L,) is larger than the previous paper width (Ln -+), and if it is not, S
If it is too thick, proceed to S5.

In S6, the control unit turns on the paper feed clutch 32 (sets the drive signal 33 to true).The paper feed roller 3 rotates and the paper is fed, and the paper contact reaches the paper feed sensor for a certain period of time, and the paper is fed. The sensor signal 31 is turned on (S7), and in synchronization with it, the TOP signal 25 is output to the controller 22 (S8).
), the horizontal synchronizing signal 26 (BD) is output at the same time, and the controller 22 outputs the image signal (VDO). Next, in S9, the control unit 21 finishes the printing operation for one sheet of paper (the state in which the paper is present in the paper feed sensor is almost the same as that during printing), and then returns to Sl to check the presence or absence of the next paper and the paper width.

If the paper width is the same, when the PRNT signal is output from the controller 22, the paper feed clutch should be turned on immediately (control signal 33 is set to true.However, if the paper size is A4 size at this point (S4)) , control signal 3
The timing of setting 3 to true is delayed by Tsec (S5). By doing so, all subsequent sequences will be delayed by Tsec. This delay time T
sec is determined by the positions of the charging roller 10, the developing sleeve 11, the transfer roller 12, and the peripheral speed of the drum 6.

Although it is better not to make the drum rotate as much as possible, the time it takes for the drum 6 to rotate twice is generally sufficient.

[Other Examples]

In the embodiment described above, the distance between the sheets is controlled in anticipation of the timing when the charging roller 10 will be uniformly charging the drum 6.

FIG. 6 shows another embodiment in which potential sensors are arranged.

FIG. 6 shows how the potential sensor is arranged downstream from the position of the charging roller 10 in the direction of rotation of the drum. In Figure 6,
SL, S2. S3 is a sensor for detecting the surface potential on the drum 6, and the sensors arranged in order from the position closest to the paper feeding reference are Sl (61), S2 (62), and S.
3 (63). The sensor position is 4. from the paper reference. ,
n, is the position of β3.

S2 is located at a position where it is wider than envelope paper < narrower than 85 size, and S3 is located at a position where it is wider than B5 size (and narrower than A4 size). 2. is approximately the minimum paper width used in the image forming device. The distance is approximately 50 mm. β is approximately 150 mm, and A is 190 mm.

FIG. 7 shows a signal processing section for inputting the outputs of these potential sensors to the control section 22. The other parts are the same as in Figure 1, so they are omitted.

In FIG. 7, 64.65 is a comparator, and 64 is S
The output signal 66 of l and the output signal 67 of 32 are compared, and 65
compares the output signal 66 of Sl and the output signal 68 of 83. Comparators 64 and 65 both output signals that turn on when the two input signals are approximately equal.

FIG. 8 shows the control flow. It is basically the same as Fig. 3. In FIG. 8, if the paper size (paper width data) has changed compared to the previous paper, the process moves from S14 to 315, where it is checked whether the current paper width is A4 or 85.

If the size is B5, the output signal 6 of the comparator 64 is increased in S16 until the output of the potential sensor S2 and the output of the potential sensor 31 become the same.
9 is checked, and when the signal 69 turns on, the drum 6
Paper feeding operation (818~
521). However, if the current paper width is A4,
In S17, the outputs of the sensors S1 and S3 are compared, and the paper feeding operation is started after waiting for the output signal 70 of the comparator 65 to turn on.
818-521).

In the first embodiment, the paper size of the paper feed tray was detected for each paper using transmitted light, but the present invention is not limited to this. For example, in a case where there are two paper feed cassettes, the code (paper size) attached to the frame of each cassette is read, and the paper width data (stored in the program ROM in the control unit 21) based on that code is read. ) may be used to change the delay time.

Specifically, it is assumed that three types of paper are used.

Put each paper into an envelope (paper width t,), B5 (same Lx),
A4 (same), and as above < L++Li, Ls
data is stored in the program ROM, and L+<L
It is assumed that there is a relationship of i<Lx. 85 from envelope size
If the time to be delayed when switching from envelope size to A4 size is T1, and the delay time to switch from envelope size to A4 size is T2, then T,=kT, for example. In this way, when the previous size is the same but the switched size is different, by making the delay time variable, it is possible to extend the life of the motor, drum, and each drive unit.

Furthermore, by having a means for counting the time of continuous printing, it is possible to obtain a good image more effectively (without always causing a delay time).

For example, if no more than 5 envelope-sized sheets of paper are being printed in a row, no delay time will occur even when switching to B5 size. However, if the envelope size is 5 or more, a delay time is required.

Note that in this embodiment, a delay time is generated by shifting the timing at which the control unit 21 starts the paper feeding operation.
The present invention is not limited to this, and any other method may be used.

For example, in the first embodiment, in an image forming apparatus having a register roller, the timing at which the register roller starts to be driven may be changed.

Furthermore, in the second embodiment, the potential on the drum surface was measured by sensors arranged in the drum axis direction, but the results may be notified to the controller 22. By doing this,
The delay time may be controlled on the controller 22 side.

[Effect of the Invention J As described above, according to the present invention, a high-quality recorded image can be provided even when the width of the paper sheet to be recorded changes.

[Brief explanation of drawings]

Fig. 1 is a block diagram of image formation according to the present invention to the embodiment, Fig. 2 is a diagram showing a timing chart in the embodiment, Fig. 3 is an operation flowchart in the embodiment, and Fig. 4 is a diagram of the embodiment. 5 is a sectional view showing the configuration, FIG. 5 is a diagram showing the location where image defects occur, FIG. 6 is a configuration diagram of the second embodiment of the present invention, FIG. 7 is a block diagram of the same embodiment, and FIG. 8 is an operation flowchart of the same embodiment. 21...Controller, 22...Controller, 10...Charging roller, 11...Developing sleeve, 12...Transfer roller, 6...Drum. Figure 5 Figure 6 Figure 7

Claims (1)

[Scope of Claims] 1) Detection means for detecting the paper widths of two continuously fed paper sheets; and the paper widths of the two paper sheets changed based on the detection results of the detection means. An image forming apparatus characterized by comprising means for delaying the recording timing of the second paper sheet.