JPH02275479A - Image forming device - Google Patents

Abstract

PURPOSE:To maintain a stable image by providing aperture limiting means which measure the axial potential of a photosensitive body by a sensor and varies the quantity of exposure according to the measurement result, on the optical path of a light beam. CONSTITUTION:The sensor 3 which measures the surface potential of the photosensitive body 1 is provided and measures the potential of the photosensitive body 1 in the axial direction A and the aperture limiting means 34 and 35 which vary the quantity of exposure of each position to a light beam according to the measurement results at respective positions of the photosensitive body 1 are provided on the optical path of the light beam. The aperture limiting means 34 and 35 are arms and form a slit for light quantity limitation at the part of dust-proof glass 11 on the optical path of the light beam. Consequently, stable image forming operation is performed irrelevantly to the generation of a potential difference between positions of the photosensitive body 1 in the axial direction A.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, and a printer.

[Conventional technology]

Conventionally, in image forming apparatuses, as a feedback means for stabilizing image quality, the surface potential of the photoconductor is directly measured with an electrometer, toner is attached to the photoconductor, and an optical sensor is used to measure the amount of toner adhesion. The surface potential of the photoreceptor is predicted from , and the image forming conditions (
Feedback corrections were made to the exposure amount, development bias, etc.).

[Problem to be solved by the invention]

The above conventional technology measures only the potential of the circumferential portion of the photoreceptor and does not correct the image forming conditions at each location in the rotational axis direction of the photoreceptor, so the image quality is also sufficiently stable. I couldn't say that it was what I had done.

An object of the present invention is to provide an image forming apparatus that can maintain stable images.

[Means to solve the problem]

According to the above object 1, in an image forming apparatus having a photoreceptor, a light beam that exposes the photoreceptor, a charger that charges the surface of the photoreceptor, and a sensor that measures the surface potential of the photoreceptor, An aperture limiting means is provided in the optical path of the light beam to measure the potential in the axial direction of the photoreceptor and change the amount of exposure of the light beam to each part based on the measurement result of each part of the photoreceptor. This is achieved by

[Effect]

A sensor measures the potential of each part in the axial direction of the photoreceptor, and based on the measurement result, the amount of exposure of the light beam to each part is changed by the aperture limiting means, and the potential difference of each part in the axial direction of the photoreceptor is changed. A stable image forming operation can be performed regardless of the occurrence of.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a block diagram showing the outline of a copying machine which is an embodiment of an image forming apparatus according to the present invention, in which l is a rotatable photosensitive drum which is an electrostatic latent image carrier, and 1a is a photosensitive drum. 2 is a rotating shaft; 2 is a charger; 3 is a sensor that is a detection means for detecting the surface potential of the electrostatic latent image carrier 1; 4 is an eraser; 5 is a developing sleeve; 6 is a pre-transfer static elimination lamp; 7 is a transfer charger; 8 is a fur brush, 9 is a cleaning blade, 10 is a static elimination lamp, 11 is a dustproof glass, 12.
13, 14, and 15 are reflecting mirrors; 16 is a lens; 17 is an irradiation lamp; 18 is a white pattern; 19 is a contact glass; and B is a light beam for exposing the photosensitive drum 1.

In the figure, an original placed on a contact glass 19 is placed between an irradiation lamp 17 and a reflecting mirror 12°13.14.1.
5 and a lens 16, the surface of the photoreceptor drum 1 is exposed to the light beam B, an electrostatic latent image corresponding to the original image is formed, and the charged area around the photoreceptor drum 1 is Charger 2° Developing sleeve 5. The operation of developing the transfer paper using a developer (not shown) by a developing means such as the transfer charger 7, the operation of eliminating static electricity using the pre-transfer static elimination lamp 6 and the static elimination lamp 10, and the photosensitive drum 1 using the fur brush 8 and cleaning blade 9. A cleaning operation is performed in a known manner.

FIG. 1 is a front view showing the configuration of a moving means for a sensor 3 which is a detection means, and 3 is disposed between the charger 2 and the eraser 4 as shown in FIG. , 20 is a stepping motor (STM), 21 is 3
7M20 (7) Worm gear provided on the rotating shaft, 22
23 is a drive gear that meshes with the worm gear 21; 23 is a drive pulley provided coaxially with the drive gear 22; 24 is a driven pulley; 25 is installed between the two pulleys 23 and 24, and the sensor 3 is fixed to a part thereof. This is the wire that was used.

FIG. 3 is a plan view of the moving means for the sensor 3,
6 is a key-shaped actuator that moves by coming into contact with a part of the sensor 3; 27 is a spring that presses the actuator 26; 28 detects the presence of one end of the actuator 26 and sets the home position of the sensor 3; This is a home position sensor that detects return.

In FIGS. 1 and 3, when the photosensitive drum 1 is stopped (non-rotating), the sensor 3
The surface potential detection operation on the photoreceptor drum 1 starts. The position of the sensor 3 shown by the solid line in FIG.
3 rotates and moves the wire 25. The sensor 3 fixed to the wire 25 moves in the direction A of the rotation axis of the photoreceptor drum 1, and reads the potential of each part on the surface of the photoreceptor drum 1, as will be described later.

When the sensor 3 reaches the driven pulley 24, the 37M20 rotates in the opposite direction, moving the sensor 3 in the direction of the driving pulley 23. At this time, the sensor 3 pushes back the actuator 26 that has been pushed out by the spring 27, and when the sensor 3 returns to the home position, the home position sensor 28 detects the presence of one end of the actuator 26. One cycle of operation is completed. This cycle can be made shorter than the time required for one normal rotation of the photoreceptor drum 1, and the operation is less noisy than the rotation of the photoreceptor drum 1.

FIG. 4(a) is an explanatory diagram showing the position of the sensor 3, FIG.
bl is an explanatory diagram showing the potential of each part at +11 in FIG. The potential at a valley portion E between a peak potential portion C of the charger 2 portion and a peak potential portion of the eraser 4 portion is measured.

FIG. 5 is a plan view showing the aperture limiting mechanism, in which 11 is a dustproof glass extending in the direction A of the rotation axis of the photoreceptor drum l;
0.31 is the opening stepping motor (STM), 3
2.33 is an aperture worm gear provided on the rotating shaft of the aperture STM 30°31; 34.35 is an arm that is an aperture limiting means that rotates to limit the amount of light beam B incident on the dustproof glass 11 portion; Reference numerals 36 and 37 denote opening driving gears fixed to the ends of the arms 34 and 35 and meshing with the opening worm gears 32 and 33, and 38 and 39 the ends F of the opening portions of the arms 34 and 35.

This is an opening home position sensor that detects G.

In the same figure, arms 34 and 35 are used to limit the amount of light beam B that exposes the charged surface of the photoreceptor drum 1 based on the detection result of the surface potential of the photoreceptor drum 1 by the sensor 3. Dustproof glass 1 in the optical path of B
A slit for limiting the amount of light is formed in one portion. Further, the arms 34 and 35 are arranged on the front side (referred to as the F side) and the rear side (referred to as the R side) of the photosensitive drum l in FIG.

The arms 34 and 35 receive an actuation signal from an opening ST.
M30.31 rotates, and this opening STM30.31 connects the opening worm gears 32, 33 and the opening drive gear 3.
6. Through 37, rotate by a certain angle and remove the dustproof glass 1.
A part of 1 is shielded from light. And when inactive, arm 3
4.35 does not shield the dustproof glass 11 from light and is waiting at a position detected by the opening home position sensor 38.39.

Figure 6 (a), Figure 7 (a), Figure 8 (a), Figure 9 (
al is an explanatory diagram showing the light amount before correction, Fig. 6 (kl, 7th
Figure (b).

Figures 8(b) and 9) are explanatory diagrams showing changes in light intensity after correction, Figures 6(C), 7(C), 8(C), and 9(C1 are FIG. 7 is a configuration diagram showing the operation of arms 34 and 35 during light amount correction.

FIG. 6(a) shows a case where the potential on the photoreceptor drum lOF side (front side) is high, and at this time, the arm 34 on the R side (rear side) of the photoreceptor drum 1 as shown in FIG. is rotated to increase the amount of light on the R side as shown in FIG. 6(b), and to equalize the potential on the photosensitive drum 1.

FIG. 7 fa) shows a case where the potential on the R side of the photoreceptor drum 1 is high, and at this time, the arm 35 on the F side of the photoreceptor drum 1 is rotated to the F side as shown in FIG. The amount of light is increased as shown in FIG. 7(b).

Figure 8 (al shows when the potential at the center of the photoreceptor drum 1 is high; at this time, both arms 34 and 35 are rotated as shown in Figure 8 (C1), and the R side and F side are The light intensity is increased as shown in FIG. 8 (bl).

FIG. 9(a) shows when the potential on the R side and F side of the photosensitive drum 1 is high. At this time, both arms 34 and 35 are rotated greatly as shown in FIG. 9th light amount
Raise it as shown in Figure (b).

By correcting the amount of light using the arms 34 and 35 as described above, the surface potential of the photoreceptor drum 1 can be made uniform, and background smear can be prevented from occurring during image formation.

FIG. 10 is a block diagram of the control system, in which 40 is a main control unit (CPU), 41 is a RAM which is a non-volatile memory built into the CPU 40, 42 is a charging power back, 43 is a fixing thermistor, and 444' ! Optical system? )'
tl part, 45 C operation-A Ct#1Ili part 1, 4
6 is an AC drive circuit, 47 is various position sensors, 48 is a scanner drive circuit, 51 is a display means, 52 is a fixing heater, 5
3 is a drive motor.

In the figure, the CPU 40 includes an eraser 4, a charging power pack 42 of the charging charger 2, and each STM 20.30.3.
1, and also receives detection signals from the fixing thermistor 43, sensor 3, and home position sensors 28, 38, and 39. Furthermore, the CPU 40 exchanges signals with an optical control section 44 and an operation/AC control section 45. In the optical control section 44, a scanner drive circuit 48 and a variable magnification drive circuit 49 brake the optical system, and control the operation/AC control section 44.
The control section 45 receives the signal from the key power section 50, causes the display means 51 to display, and also controls the AC drive circuit 46 and the CP
Send signal to U40. The AC drive circuit 46 turns on and off the fixing heater 52, various drive motors 53, and irradiation lamp 17.

FIG. 11 (Part 1) and (Part 2) are flowcharts showing the operation when measuring the potential by the sensor 3.
power switch) is turned on (step 1l-1), and if the number of copies already copied in the counter (CNTI) does not exceed 10,000 (N in step 11-2), the mode shifts to normal copy mode (step 1l-1). 1l-3), when the number of copies is 10,000 or more (Y in step 11-2) and the fixing temperature XL is higher than the predetermined value X0 (Y in step 11-3), the potential measurement operation execution flag is set. Can stand (
Y in step 11-4). The fixing temperature Xt is a predetermined value X
If it is lower than 0, an execution flag is set to raise it to a predetermined value X0 (step 1l-5).The predetermined value X0 of the fixing temperature is determined as shown in the explanatory diagram in FIG. Assuming that the constant for each machine is A, the heat capacity of the fixing section is B, and the time is t, the temperature of the fixing section (d e g) has the relationship of d e g ('C) mA ε-yI/l, and the 12th As shown in the figure, the fixing temperature X becomes sufficient after the predetermined value X0.

If potential measurement is not required, the operation execution flag is not set (N in step 11-4) and the process shifts to normal copy mode (step 1l-3). When the potential measurement operation execution flag is set (Y in step 11-4), the normal copying operation is disabled (step 1l-5), the counter (CNTI) is cleared (step 1l-6), and the forming operation is started (step 1l-6).
Step 1l-7).

Here, as in normal copying, the charger 2 is turned on, the photoreceptor drum l is rotated, the bias voltage is raised sufficiently to prevent toner from sticking, and the sensor (electrometer) 3 is moved to the home position (H .

P) (step 1l-8).

Next, sampling of potential measurement on the surface of the photoreceptor drum l (
(described later) is performed (step 1l-9). The stepping motor (STM) 20 does not start. Step 1l-1
0), the sensor 3 moves in the rotation axis direction A, and the surface potential of the photosensitive drum 1 increases. (step 1l-11),
This read data is stored in the memory 41 (step 11-12).

When the sensor 3 reaches the end of the photosensitive drum 1 in the rotation axis direction A (Y in step 11-13), the sensor 3 returns to H.
, P (step 1l-14), the potential measurement operation flag is turned off (step 1l-15), and arm 3
4.35 drive starts (step 1l-16).

FIG. 13 shows the home position (H) of the sensor 3.

P) is a flowchart showing the detection operation, and when the home position sensor 28 is off (step 13-
1 N), the back flag for moving the sensor 3 is turned on (Step 13-2), the timer is also turned on (Step 13-3), the STM 20 is driven (Step 13-4), and the timer is set to the predetermined value M. + of sensor 3 until
A y movement is performed (N in step 13-5).

Here, if the timer exceeds the predetermined value M, step 13-
5), an abnormality flag is set (step 13-6). If this abnormality flag is raised, the home position sensor 28
is turned on (Y in step 13-1), the back flag is turned off (step 13-7), the timer count is cleared (step 13-8), and STM2
0 has stopped (step 13-9), and the sensor 3 has returned to normal.

FIG. 14 is a flowchart showing the operation during charging. In this embodiment, since the photoreceptor drum 1 is charged without rotating, the relationship between the charging potential of the photoreceptor drum 1 and time is shown in FIG. 15. The predetermined charging potential (■.)
The on-time of the charging power pack 42 required to become 0
．． It will be 5 seconds.

In Figure 14, first the 0.5 second timer is cleared (
Step 14-1), the timer start flag becomes O (step 14-2). If the timer start flag is not on (N in step 14-3), the start flag is set (step 14-4), the charging power pack 42 is turned on (step 14-5), and the 0.5 second timer is started. When the time is up (step 14-7), the charging power pack 42 is turned off (step 14-8), and the 0.5 second timer is reset and cleared (step 14-9).

FIG. 16 is a flowchart showing the operation of the eraser 4, and in this embodiment, the charging voltage of the photosensitive drum 1 is set as shown in FIG. The eraser 4 causes the residual potential to reach the vR level after 0.4 seconds.

In FIG. 16, first, the eraser 4 is reset (step 16-1), the data of all lighting modes is set to serially light up (step 16-2), the 4ms timer is cleared (step 16-3), and the eraser 4 is reset (step 16-1). Turn on (all lights on) (step 16-4). At this time, the 4ms timer starts (step 16-5), and when it counts up (
Step 16-6), eraser 4 is turned off (step 16-7), the 4ms timer and eraser 4 are reset,
Cleared (step 16-8).

FIG. 18 shows the potential V0. This is a flowchart of VR sampling, in which the sensor 3 is moved in the rotation axis direction A of the photosensitive drum 1 in synchronization with a step angle of 37M20,
The potential ■. , V are measured, but first the step angle of 37M20 rises (step 18-1), and sensor 3
When the sensor 3 moves, the measurement result of the sensor 3 is input to the register of the CPU 40 via the AN board (step 18-2).
). This input is input from the register in the CPU 40 to the memory 4.
1 (step 18-3), and the memory address of the memory 41 is set to +1 (step 18-4).

As shown in FIG. 19, the memory 41 internally has 256 memories from memory (1) to memory (256), and the memory (1) = (256) is shown in FIG. It is divided into 16 parts as shown in FIG.

FIG. 21 is a flowchart showing the operation of the memory 41. First, the counter of the average value memory is cleared (step 21-1), the memory address and the average value memory address are set (step 2l-2), and the values are added. Clear the number counter and memory addition register (step 2l-3). Then, add +1 to the memory data of the memory address and the addition register each in step 2l-4.
), if the number of additions is less than 16 (N in step 21-5), it is further added to the memory address and the addition register, and when the number of additions reaches 16 (Y in step 21-5).
), divide the memory addition register into 16 equal parts (step 2l
-6). The measured data is stored in the average value memory address (Step 2l-7), and the average value memory counter is sequentially set to +.
1 is added (step 2l-8), and when the count number of the average value memory counter becomes larger than 16 (step 2l-8),
1-9 Y), Clear various counters and registers Step 2l-10) If the count number is less than 16, enter the step (21-3) (Step 21-10).
9 N).

In the average value memory ■~[phase], the average value (data A) of ■~[phase] is the potential average (potential ■., V*) of the entire photoreceptor drum 1, and the average value of ■~[phase] ( Data F) is the average potential of the front side of the photoreceptor 1, the average value of ■~[phase] (data C) is the average potential of the center of the photoreceptor drum 1, and the average value of @~■ (data R ) is processed to be the average potential on the back side of the photoreceptor 1.

FIG. 22 is a flowchart showing the calculation operation of the potentials VO, V, and step 22-
1), the developing bias is corrected based on the calculation result (step 22-2), and the charging potential is corrected (step 22-2).
Step 22-3).

FIG. 23 is an explanatory diagram showing the relationship between the potential of the photosensitive drum 1 and the number of copies, and as shown in the figure, the charging potential of the lower photosensitive drum 1 changes over time. The residual potential ■e rises and ■.

-■ The range becomes narrower, and this causes deterioration of image quality such as background smearing, so the above-mentioned correction is required.

Figures 24 (Part 1) and (Part 2) are flowcharts for determining the correction value, in which the absolute value ΔA of the difference between the set value and the measured data is calculated (step 24-1), and ΔA is less than the set value. If it is larger (Y in step 24-2), a lamp voltage correction routine is entered (step 24-3). Data F
is larger than data C (Y in step 24-4), calculate the difference as ΔFC (step 24-5), data F
is smaller than data C (N in step 24-4), the difference is output as ΔCF (step 24-6).

Compare data R and data C in the same way.Step 2
4-7), step 24-8) to calculate the difference ΔCR, and calculate the difference ΔRC (step 24-9). Further data R
and data F (Step 24-10), the difference ΔF
step 24-11) to calculate R, and step 24-12) to calculate the difference ΔRF.

If the ΔCF is larger than the set value (step 24-13
), STM-F on the front side of STM30.31 for opening
31 (step 24-14), and similarly, if ΔFC≧set value (step 24-1)
5) Set a minus flag in STM-F31 (Step 24-16) If ΔRC≧setting value (Step 2
4-17), set a plus flag on the STM-R30 on the back side (step 24-18), and if ΔCR≧setting value (
Step 24-19), and sets a minus flag in the STM-R30 (Step 24-20).

The above steps (24-14), (24-16).

(24-18), (24-20) are STM3 for opening
A step of setting a flag for correction of 0.31,
If you use this as a data table, you can also adjust the amount of correction.

The opening home position 38°39 shown in Fig. 5 is
The front side is HP, F39, and the back side is HP.

If R38 is selected, HP, F39 and HP, if R38 is not on (N in step 24-21), STM-F31
and drives the STM-R30 to return the arms 34 and 35 to the home position (HP) (step 24-22).

Here, the reference position of arms 34 and 35 is when they return to HP, but in FIG.
The position where Hz is parallel is the position where no light amount correction is performed by the arms 34 and 35. Therefore, for control, the arm 34 is always controlled once by STM-F31 and STM-R30.
．． 35 to HP, then set the STM-F plus (minus) flag or STM-R plus (minus) to the position where the surfaces H8 and R2 without correction are parallel.
The width of the opening (slit) created by the arms 34 and 35 is corrected using the flag.

Step 24-23 when the STM-F plus flag is set
), the STM-F data is incremented (step 24-24), and when the STM-F minus flag is set (
Steps 24-25) and decrements the STM-F data (Steps 24-26). Also, when the STM-R plus flag is set (steps 24-27), the STM-
Increment R data (steps 24-28)
, when the STM・R minus flag is set (step 24-
29) Decrement the STM-R data (steps 24-30). and plane H1 of arm 34.35,
STM-F2O and STM-R3 so that Ht is parallel
1 (step 24-31). However, in order to correct the opening width of the arms 34 and 35, the irradiation lamp 17
It is necessary to correct the absolute amount of illuminance (up or down) by changing the lamp voltage.

Irradiation lamp I based on the data table according to the above ΔA
Step 24-3: Increase or decrease the lamp voltage of 7.
2) If the positive flags of STM-F and STM-R are set (Y in step 24-33), increase the lamp voltage (step 24-34), and
If the minus flag of M-R is set (step 24)
-35 Y), lower the lamp voltage (step 2
4-36).

FIG. 25 is a flowchart showing the reset operation of each data. When the above correction is completed, each memory data of potentials Vo and Vm is cleared (step 25-1), and the main drive motor is turned on (step 25-1). 2), bias is applied to the developing sleeve 5 (step 25-3)
, the cleaning means such as the cleaning blade 9 is activated (step 25-4), the static elimination lamp 10 is turned on (step 25-5), and the photosensitive drum 1 rotates 1.5 times (Y of step 25-6). ), the start flag becomes 0 (step 25-7).

When the start flag becomes 0, the main drive motor
Bias, cleaning means9. The static eliminating means 10 and the like are turned off (step 25-8), the copy prohibition flag is set to O (step 25-9), and the process shifts to normal copy mode (step 25-IO).

〔Effect of the invention〕

As described above, the present invention provides an image forming apparatus that can change the amount of exposure of a light beam to a photoreceptor based on the potential difference of each part in the axial direction of the photoreceptor, and can maintain stable image quality. can.

[Brief explanation of drawings]

FIG. 1 is a front view showing an embodiment of the moving means in the detection means of the image forming apparatus according to the present invention, FIG. 2 is a configuration diagram of a copying machine, and FIG. 3 is a plan view of the moving means stage of FIG. 1. Figure 4 (
a) is an explanatory diagram showing the position of the sensor, FIG. ), Figures 8(a) and 9(a) are explanatory diagrams showing the light amount before correction, and Figure 6(b)
, Fig. 7(b), Fig. 8(b), Fig. 9 (bl is an explanatory diagram showing the change in light amount after correction, Fig. 6(C). Fig. 7(C), Fig. 8(C) ), Fig. 9 (C1 is a configuration diagram showing the operation of the arm, Fig. 10 is a block diagram of the control system, Fig. 11 is a flowchart showing the overall operation of potential measurement, Fig. 12 is an explanatory diagram of the increase in fixing temperature. , FIG. 13 is a flowchart showing the home position detection operation of the sensor.
Figure 4 is a flowchart of charging operation, Figure 15 is an explanatory diagram showing the relationship between charging potential and time, Figure 16 is a flowchart showing eraser operation, Figure 17 is an explanatory diagram explaining residual potential, and Figure 18. 19 is an explanatory diagram showing internal memory, FIG. 20 is an explanatory diagram showing memory division, FIG. 21 is a flowchart showing memory operation, and FIG. 22 is a flowchart showing potential calculation operation. , FIG. 23 is an explanatory diagram showing the relationship between the potential and the number of copies, FIG. 24 is a flowchart showing the correction value determination operation, and FIG. 25 is a flowchart showing the reset operation. DESCRIPTION OF SYMBOLS 1... Photoreceptor, 2... Charger, 3... Sensor, 34.35... Aperture limiting means, A... Axial direction, B... Light beam. Funeral map (a) Funeral map (b) Funeral map (c) +1 Figure (a) Funeral map (b) Funeral map (a) Red map Funeral map (a) Funeral map (b) Figure (C) I Figure (a) Funeral diagram Figure (C) Figure Figure Q Figure 13 Figure Figure Figure Figure 19 Figure 20 Figure 23

Claims (1)

[Claims] In an image forming apparatus that includes a photoreceptor, a light beam that exposes the photoreceptor, a charger that charges the surface of the photoreceptor, and a sensor that measures the surface potential of the photoreceptor, the sensor detects the axial direction of the photoreceptor. An image forming apparatus characterized in that an aperture limiting means is provided in the optical path of the light beam for measuring the potential of the photoreceptor and changing the amount of exposure of the light beam to each part based on the measurement result of each part of the photoreceptor. .