JPH02140764A - Image forming device - Google Patents

Abstract

PURPOSE:To appropriately picture density to be adjusted and to obtain a picture with stable density by evaluating toner attaching quantity according to transmitting light quantity. CONSTITUTION:The title device is provided with an evaluating means evaluating the amount of toner attaching to transfer material, based on signals from a light receiving means 31b which detects transmitting light from the transfer material illuminated by an illuminating means 31a which illuminates the transfer material where a toner picture carried on a path 29 is formed. The light receiving means 31b outputs signals in response to light receiving quantity. Transmitting density is operated according to the output, and based on the operated one the toner attaching quantity is evaluated. In this case, the transmitting density and the toner attaching quantity are in linearly proportional relation, and therefore the toner attaching quantity can be evaluated with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an image forming apparatus such as a copying machine or a printer that uses a powder developer.

(Prior Art) In an image forming apparatus using a powder developer, the amount of toner adhering to an electrostatic latent image is a major factor in determining the quality of the image.

Therefore, conventionally, a pattern image for density detection is formed on an electrostatic latent image carrier or transfer material, and the reflected density is measured from the amount of reflected light obtained by illuminating the pattern image, and the amount of toner adhesion is calculated from that value. An image density control method using a reflection method has been proposed in which the toner density of the developing device or the developing conditions are adjusted based on the evaluation.

Note that the reflection density refers to the logarithmic value of the ratio of the amount of reflected light between the standard white surface and the pattern image.

(Problem to be solved by the invention) However, in the image density control method, it is physically impossible to arrange the illumination device and the light receiving device on the same straight line with respect to the normal line of the transfer material, and the toner particles This has the disadvantage that the influence of shadows occurring in the background is included in the measured value of the light receiving device, making it impossible to evaluate the true amount of toner adhesion.

Further, the relationship between the toner adhesion amount and the measured value is different depending on the state before the toner particles are saturated on the surface of the pattern image and the state after the toner particles are saturated. In other words, the relationship between reflection density and toner adhesion amount is determined by the area of the underlying portion exposed between toner particles until the pattern image is saturated with toner particles, and once the pattern image is saturated with toner particles. Since it is determined by the toner surface layer regardless of the toner layer thickness, the change state is significantly different before and after saturation. In a fixed image, the spread of the toner and the surface condition of the toner layer change, and the above-mentioned tendency becomes remarkable.

Specifically, when image density is measured by the reflection method, the first
As shown in Figure 2, the amount of toner adhesion and the reflection density show a linear proportional relationship in areas where the amount of toner adhesion is small, but when the amount of toner adhesion exceeds 0.5 mg/cm, the relationship becomes linear. The relationship collapses and the slope of the curve gradually becomes gentler.When the amount of toner adhesion exceeds 0.8 mg/cm', the reflection density becomes constant regardless of the increase in the amount of toner adhesion.

From the above, when controlling image density using the reflection method, the amount of toner adhesion cannot be accurately evaluated from the reflection density, toner density management is inaccurate, and excessive toner is supplied to the developing device, causing fogging on the image. The problem was that unevenness appeared, leading to poor image quality.

Therefore, as a result of various studies, the inventor of the present invention found that when using a translucent transfer material such as paper, illumination is applied to the transfer material to which toner has adhered.
It has been found that the transmission density calculated by measuring the amount of transmitted light exhibits a nearly linear proportional relationship with the amount of toner adhesion, as indicated by "○" in FIG.

(Means for Solving the Problems) The present invention has been made based on the above findings, and will be described with reference to FIGS. 1 and 6 showing one embodiment. Copying machine] (1), a passage (29) for conveying a transfer material with a toner image transferred thereto, and an illumination means [light emitting element] (31a) for illuminating the transfer material conveyed through the passage (29); A light receiving means [light receiving element] (31b) detects transmitted light from the transfer material illuminated by the illumination means (31a), and toner attached to the transfer material based on a signal from the light receiving means (31b). This system is equipped with an evaluation means for evaluating the amount (second CPU (60), etc. (see FIG. 6)).

(Function) In the image forming apparatus, the transfer material on which the toner image has been transferred is illuminated by the illumination means (31a) while being conveyed through the passage (29), and the transmitted light is detected by the light receiving means (31b). .

The light receiving means (31b) outputs a signal at a level corresponding to the amount of received light to the evaluation means (60), etc., and the transmission density is calculated according to the output value, thereby evaluating the amount of toner adhesion.

Here, since the transmission density and the amount of toner adhesion are in a linear proportional relationship as shown in FIG. 12, the amount of toner adhesion can be evaluated with high accuracy.

(Example) Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a copying machine (1) which is an image forming apparatus according to the present invention.
) is a sectional view showing a schematic configuration of a copying machine (1). Images are formed in the following manner in this copying machine (1).

The document placed on the document table glass (3) covered with the opening/closing cover (2) is illuminated by the exposure lamp (5) as the image league unit (4) moves, and the reflected light is illuminated by the lens array (6). is exposed to the line sensor (7) through the R (red), G (green), B (blue)
It is read as a color signal of three primary colors.

These R, G, and B color signals are processed by an image processing circuit (Y(
The signal is converted into a three-value or four-value signal of yellow), M (magenta), C (cyan), or these with Bk (black) added, and is transmitted to the laser optical system (8). The copying machine of this embodiment does not have images for three colors, and the image league unit (4) scans each time when forming an image for each color, and based on this, sequentially Y, M, C or Y, M, C,
The Bk signal is transmitted to the laser optical system (8).

The laser optical system (8) is Y, M, C or Y.

Image forming laser beams for each color based on M, C, and Bk signals are transmitted through a polygon mirror (9) and an fθ lens (10).
, and illuminates the photosensitive drum (12) via the reflective mirror (11).

The photosensitive drum (12) is charged by a charger (13), and an electrostatic latent image is formed by exposure to the laser light.

This electrostatic latent image moves in the direction of arrow (a) as the photoreceptor drum (12) rotates, and is developed by being supplied with toner at a portion facing the developing devices (14) to (17). Note that the developing devices (14) to (17) use a two-component powder developer consisting of toner and carrier.
4) is yellow toner, developer (15) is magenta toner, developer W (16) is cyan toner, and developer 1as
(17) contains black toner, and toner is replenished from toner replenishing devices (41) to (44) in an amount corresponding to the amount consumed by development.

The toner images formed by the developing devices (14), .

Nao, the vapor is transferred from the paper feed cassette (21) to the feeding roller (
22), it is once conveyed to the timing roller (23), and then, at the right timing, is conveyed to the lower part of the transfer drum (24) by the timing roller (23). The vapor conveyed below the transfer drum (24) is held at its tip by a chuck (25), and the vapor is transported under the transfer drum (24).
Based on the rotation of step 4), it is held on the outer peripheral surface and passes through the portion facing the transfer charger (18). In addition, the timing of the toner image and vapor is controlled by a transfer drum inch (26) provided on the side of the transfer drum (24).
) is detected, and the laser optical system (
8) is taken by driving.

After the surface of the photosensitive drum (12) that has passed through the portion facing the transfer charger (18), residual toner is removed by a cleaning device (19), and then the residual charge is erased by light irradiation from an eraser lamp (20). Prepare for the next development.

If the image to be created is a multicolor image, the image reader unit (4) scans multiple times, and each time the laser optical system (8) emits a laser to create an electrostatic latent image corresponding to the color to be reproduced. At the same time, the above-mentioned developing operation is repeated by switching the drive of the developing device according to the color, thereby forming a multicolor unfixed color toner image on the vapor.

When all development and transfer are completed, the vapor is separated from the transfer drum (24) and transported to the fixing device (27) by the conveyor (27).
28), the unfixed color toner image is heated and fixed on the vapor, and transferred to the υ tray (28) via the passage (29).
30).

Figure 2 shows the operation panel (100) of the copying machine, which includes a print key (101), numeric keypad (102), clear/stop key (103), image sample creation switch (104), and this image sample creation switch. (104
) is pressed (+05), developer select key (106), simultaneous multi-color copying mode selection key (107), LED indicating that simultaneous multi-color copying mode is selected (108). ), developer select key (1
1, ED (111), . . . (115) are provided for displaying the toner color of the developing device selected by 06).

Figure 3 is a control circuit diagram of the copying machine, where the first cPU (50) receives signals from various switches etc. provided on the operation panel (+00) and outputs necessary information.
At the same time, the main motor, developing motor, paper feed roller clutch, timing roller clutch, electrification charger (13), eraser lamp (
20), transfer charger (18), toner supply motor (
45), -, (48), etc.

Image density control of the copying machine having the above configuration will be explained.

As shown in the flowchart of FIG. 4 and the time chart of FIG. 5, when the image sample creation switch (104) on the operation panel (100) is pressed (step Sl)
, the main motor, developing motor, charging and transfer charger are turned on, the photoreceptor drum (12) and peripheral equipment are set to a developing state, and the developing device (14) containing yellow toner is set to a developing state. be done. Also, the timers (T-A) and (T-B) are started, and vapor is fed by the paper feed roller (22) based on the ON operation of the paper feed roller clutch (21). (Step S2). The timer (TA) is set to a length such that the vapor supplied from the paper feed cassette (21) contacts the timing roller (23) with its tip and forms a loop.

When the timer (TA) ends (step S3), the paper feed roller clutch is turned off and the paper feeding operation from the paper feed cassette (21) is stopped (step S4).

Subsequently, when the timer (T-B) ends, in step S5), the timing roller clutch is turned on to rotate the timing roller (23) and hold the tip of the vapor in the chuck (25) of the transfer drum (24). , transfer drum (
24) to guide the paper to a portion facing the transfer charger (18). In addition, the eraser lamp (20) is turned on, and the timers (T-C), (T-D) and (T-E) are turned on.
is started (step S6).

Here, timer (T-C) is timer (T-D), (T
It is set considerably longer than E), and while the timer (TC) is counting, the image sample creation operations from steps S8 to 810 are repeatedly executed.

In this image sample creation operation, the following operation is executed while the timer (TE) is counting.

That is, the photoreceptor drum (12) is exposed to laser light from the laser optical system (8) to form an image sample pattern ik.
) image is formed, this pattern latent image is visualized as a yellow toner image by supplying yellow toner from a developing device (14), and is transferred onto transfer paper at a portion facing the transfer charger (18). On the other hand, the photoreceptor drum (12) that has lost its yellow toner image is cleaned by a cleaning device (19) after which residual toner is removed from the surface by an eraser lamp (20).
) The residual charge is erased by light irradiation.

When the timer (TE) ends (step S9), the eraser lamp (20) is turned off (step 510).

Subsequently, when the timer (T-D) ends, the eraser lamp (20) is lit again and the timer (T-D) is turned on again.
), (T-E) are reset (step 511), and the drive of the developing motor is switched from the yellow developer (14) to the magenta developer (15) containing magenta toner (step 512), and the same as described above. An image sample of magenta toner is formed on the vapor.

The above-described image sample creation operation is repeated until the timer (TC) expires, and as many image samples as the number of developing units installed in the copying machine are formed on the vapor. The copying machine of this embodiment has four developing machines (14
), -, (17) are attached, so a pattern image created with those colors is formed on the vapor.

When the timer (T-C) ends, step S7), the developing motor, charging and transfer charger, and timing roller clutch are turned off, and the timer (T-F) is set (step 313), and the eraser lamp (20) is turned off.
The residual charge is erased from the surface of the photoreceptor drum (12) by the light irradiation.

When the timer (T-F) expires, the main motor and eraser lamp (20) are turned off and this subroutine ends.

The image sample created in step 1 in this way is attached to the fixing device (
The image is fixed on the vapor at step 28), and the transmitted density is read by the image density detection sensors (31), .

Image temperature detection sensors (31), ~, (34) are light emitting elements (3] a), ~, (34a) and light receiving elements (3l).
b), .
2b), (33a) and (33b), (34a) and (3
4b) are facing each other.

FIG. 6 shows the configuration of the image density control circuit including the image density detection sensor (31), where (60) is the second CPU, (
61), (62), and (63) are resistors, (65) is an amplifier, (64), (66) are comparators, and (67) is a motor drive circuit. Although not shown, other circuits including the image density detection sensors (32) to (34) are similarly configured.

Figure 7 shows the output A from the light receiving element (31a) to the comparator (64), and Figure 8 shows the output A from the comparator (64) to the second CPU (60).
Output A' to the amplifier (65) to the comparator (6) is shown in Figure 9.
Output B to G), FIG. 10 is from comparator (66) to 2C
Output B' to PU (60) is shown.

As shown in FIGS. 7 and 9, when the tip of the vapor passes through the fixing device (28) and enters the part facing the density detection sensor (31) through the passage (29) (at time T), light is emitted. The amount of light received by the light receiving element (31b) that receives the light from the element (31a) decreases as the light is blocked by the paper, and the outputs A and B each decrease accordingly. Note that since the output B is amplified by the amplifier (65), its output voltage (18) is generally higher in potential than the output voltage (2) of the output A.

When the vapor is roughly conveyed and the yellow toner image sample on the paper reaches the part facing the image density detection sensor (31), the amount of light received by the light receiving element (31b) (transmitted light amount) further decreases and is output. Both AB further decreases at time T, after which the image sample is transferred to the sensor (3).
When passing through the opposing part of 1), outputs A and B reach time T. The state recovers from to T1. Then, when the rear end of the paper passes through the part facing the image density detection sensor (31), an output A is generated.

B returns to its original state (K.

In the comparators (64) and (66), the voltage value V of the outputs A and B
A, V, and reference voltage V0 are compared, and V, , V
, ≧Vo, the “High” (H) signal is sent to the second CPU.
(60), and if V,,V,<V, the “Low” (L) signal is sent to the second C.
Output to PU (60).

In addition, the reference voltage ■. is the yellow! contained in the yellow developing device (14).・Compatible with the standard values that control the concentration of toner.

Here, as mentioned above, the output B to the comparator (66) is amplified by the amplifier (65) and has a higher potential than the output A, so the output A° of the comparator (64) is as shown in FIG. As shown in FIG. 3, the (L) signal is continuously output while the paper passes through the opposite part of the image density detection sensor (31).
The output B' of the comparator (66) is as shown in FIG.
The image sample on the vapor is the image density detection sensor (31)
(from time T1 to T) only while passing through the opposite part of (
L) Output a signal.

In the second CPU (60), the output A from the comparator (64)
The timing at which ° changes from (H) to (L), that is, the timing at time T0, is detected, and the timing from time (T, ) to (T,
) It is determined whether the output B' is (T4) or (L) based on the read signal (see FIG. 11) issued during the period (see FIG. 11).

If the signal from the comparator (66) is (H), it means that the density of the image sample made of yellow toner is lower than the predetermined reference degree, and in this case, the motor drive circuit (
67), the toner replenishment motor (45) is driven to replenish the developing device (14) with the required amount of toner. Further, if the signal from the comparator (66) is (YES), it means that the density of the image sample is higher than the reference density, and at this time, toner is not replenished.

Here, the toner adhesion amount and transmission density of the image sample are:
As shown in FIG. 12, there is a linear proportional relationship, and the amount of transmitted light of the light illuminated on the vapor from the light emitting element (31a) is proportional to the density of the image sample. Concentration can be adjusted.

Similarly, the toner density detection sensor (
The transmission density is measured in steps 32), (33), and (34), and the necessary amount of toner is supplied to the necessary developing devices.

Note that in the above embodiment, image density control is performed by measuring transmitted light by pressing the image sample creation switch (104) provided on the operation panel (100).
The print switch (101) serves as both the image sample creation switch (104) and the print switch (101).
When the button is pressed, a normal image is created on the paper, and the image sample is created at the corner of the vapor, and the image density may be managed based on this.

Further, in the embodiment described above, an image density detection sensor (31) etc. is provided downstream of the fixing device (28) with respect to the paper conveyance direction, and this detects the image sample fixed on the vapor. However, the image density detection sensor (31
) etc. may be provided upstream of the fixing device (28), and image density may be evaluated from an image sample before fixing.

Furthermore, density management is not performed only by the image density detection sensor (31), etc., but by providing a magnetic sensor, etc. in the developing device, which constantly measures the toner density in the developing device, and based on the results, the toner concentration is determined. may be maintained constant.

(Effects of the Invention) As is clear from the above description, according to the image forming apparatus according to the present invention, the amount of toner adhering to the transfer material and the transmitted density are in an almost linear proportional relationship, so the amount of transmitted light is also The toner adhesion amount evaluated is extremely accurate.

Therefore, the image a degree adjusted based on the evaluation result becomes appropriate, and less toner spills from the developing device, making it possible to obtain an image with stable density.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a copying machine which is an image forming apparatus according to the present invention, FIG. 2 is a plan view of an operation panel, FIG. 3 is a control circuit diagram related to image creation, and FIG. 4 is a flowchart of an image sample creation subroutine. , FIG. 5 is a time chart, FIG. 6 is a circuit diagram related to image density evaluation, FIGS. 7 to II are diagrams showing the output of each part in the circuit of FIG. 6, and FIG. FIG. 1...copying machine, 31. ~, 34... image density detection sensor, 31 a, ++, 34 a- light emitting element, 3
lb, ~, 34 b... Light receiving element, 60 -... Second CPU. Patent Applicant: Minolta Camera Co., Ltd. Agent, Patent Attorney, Haka 1, Figure 1, Figure T1. $lO diagram Figure 11

Claims (1)

[Claims] (1) An image forming apparatus using a powder developer includes a path for conveying a transfer material onto which a toner image has been transferred, an illumination means for illuminating the transfer material conveyed through the passage, and an illumination means for illuminating the transfer material conveyed through the passage. a light receiving means for detecting transmitted light from the transferred transfer material;
An image forming apparatus comprising: evaluation means for evaluating the amount of toner attached to the transfer material based on a signal from the light receiving means.