JPH0420982A - Two-color image forming device - Google Patents

Abstract

PURPOSE:To always obtain a sharp image having less color mixture by detecting the consumption of first and second developers and carrying out color mixture separation control based on these relations. CONSTITUTION:When a printing action is finished, a counted value L1 integrated by a first dot counter 50 is compared with a first prescribed value a1. When the counted value L1 is smaller than the prescribed value a1 (L1<a1), it is judged that the consumption of color toner is still a little, and the color mixture is within an allowable level. When the counted value L1 is larger than the counted value L2 of a second dot counter 51 at L1>=a1, in other words, when the consumption of the color toner is more than that of black toner, a transfer to a separating mode is carried out. In the separating mode, first, the value of a timer for setting a separating time is set at a required value, and a photosensitive drum, first and second electrifying chargers, and a second developing unit are turned on, and driven. The color toner (negative polarity) mixed into a second developing unit 7 is stuck to the surface of the photosensitive body 1, and removed the developing unit 7.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a two-color image forming apparatus that simultaneously forms two-color images using a plurality of colors, and particularly relates to an improvement in color mixing and separation technology during development.

[Conventional technology]

For example, a simultaneous two-color copying machine that uses black and red (color toner) as a two-color image forming device reads black and red images with a light receiving element and is exposed to laser light of two wavelengths modulated accordingly. Two different locations on the body drum are exposed in the circumferential direction to form a latent image of each color. Here, in order to improve the visibility of the image, the exposure position of each color is usually charged and exposed for the red image on the upstream side in the rotational direction from the black image.
The image is developed in a first developer containing red toner.

Further, after the red color is developed, black color is recharged and exposed, and then developed in a second developer containing black toner. Therefore, the red toner is scraped by the developer in the second developing device and mixed into the second developing device, and during black development, an image that is originally black becomes an image that is a mixture of black and red. There is. As a conventional color mixture separation technique to prevent this, JP-A-58-
The one disclosed in No. 72158 is known. A two-component developer consisting of red toner and carrier is stored in a first developing device located upstream of the photoreceptor drum, and a two-component developer consisting of black toner and carrier is stored in a second developing device located downstream. It stores developer.

The red toner and black toner used here are non-magnetic, and when the red toner is mixed into the second developing device containing the black toner, it has the property of being charged to opposite polarities due to frictional charging. have different physical properties.

The red toner having such characteristics and mixed into the second developing device will cause the non-image area of the photoreceptor drum (
(charged section) and is removed from the second developing device. Since the attached red toner has the same polarity as the applied voltage of the transfer charger, it is not transferred to the paper, but remains attached to the photoreceptor, and is scraped off and collected by a cleaner. In this way, color mixture separation is automatically performed during development.

[Problem to be solved by the invention]

However, as mentioned above, even if the physical properties of the two toners are different, if the amount of red toner mixed in increases, the amount of mixed red toner will be larger than the amount of separation, and color mixing separation in which red toner adheres to non-image areas alone is insufficient. There was a problem that color mixture separation could not be performed and the color mixture ratio increased.

In particular, if the image density of the red image, that is, the ratio of the image area to the total area of the image is high, and the image density of the black image is low, the amount of mixed toner will increase and it will be difficult to remove the mixed toner. becomes sufficient, and the color mixture ratio increases.

On the other hand, in the case of color toner that is charged to opposite polarity when mixed, the separation ability is determined by the physical property difference between the color toner and black toner as described above, that is, the difference in the charging series, as well as the mixing of the carrier of the second developer and the black toner. It depends on the ratio and the stirring time and strength of the second developer.

Here, the larger the mixing ratio, the higher the separation ability, and conversely, if the mixing ratio is 3% or less, the separation ability disappears. Further, the separation ability decreases as the stirring time increases, and the greater the amount of new black toner supplied, the higher the separation ability becomes.

Further, in the above-mentioned case, the amount of color toner mixed into the second developer depends on the development method, carrier physical properties, second development conditions such as setting conditions, and the consumption amount of color toner. On the other hand, even if color toner is mixed in, when development with black toner is performed, color toner adheres to non-image areas and is removed, so if the amount of black toner consumed is large, the amount of mixed toner gradually decreases.

The present invention has been made based on such knowledge, and the present invention is based on the first
developer (color toner) and second developer (black toner)
It is an object of the present invention to provide a two-color image forming apparatus that can always obtain clear images with less color mixture by detecting the consumption amount of color and performing color mixture separation control based on the relationship between the two.

[Means to solve the problem]

A two-color image forming apparatus according to the present invention is arranged around a rotating photoreceptor, and first and second images of different colors and characteristics are arranged around a rotating photoreceptor.
first and second developing means each containing a developer separately and developing a latent image formed on the photoreceptor, and an upstream developer mixed into the second developing means on the downstream side in the rotation direction of the photoreceptor a two-color image forming apparatus that includes a mixing and separating means for separating the first developing portion of the first developing means based on the characteristics, and performs an image forming operation and a mixed color separating operation simultaneously or sequentially; The first developer detects values related to the consumption amounts of the developer and the second developer separately. a second consumption amount detection means; and a detected first consumption amount detection means;
and a mixture separation control means for controlling the operation of the mixture separation means based on a value related to the consumption amount of the second developer.

[Effect]

In the present invention, for example, the first and second
The values related to the consumption amounts of the first and second developers, such as counting the number of dots in image formation using the developing means or the replenishment amounts of the first and second developers, are detected separately, and the detected first It is determined whether or not to enter the color mixing separation operation based on the consumption amount of the developer, and depending on the relationship between the consumption amounts of the first and second developer, for example, the consumption amount of the first developer is determined as the consumption amount of the second developer. When the number of colors is greater than that, the operation time of the color mixture separation operation is determined according to the difference.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on drawings showing embodiments thereof.

FIG. 1 is a sectional view showing a schematic configuration of a two-color laser beam printer, which is a two-color image forming apparatus according to the present invention, together with a block configuration of a control system.

In the figure, l is a photoreceptor drum, and the surface has, for example, a-
A photoconductive film such as Si is formed. The photosensitive drum 1 is installed so as to be rotatable in the direction of arrow a, and a first charging charger 2, a first optical system 3, a first developing unit 4, and a second charging unit are arranged around the photosensitive drum 1 in order along the direction of rotation. A charger 5, a second optical system 6, a second developer 7, an eraser lamp 8, a transfer charger 9, a blade-type cleaning device 10, and a main eraser lamp 11 are installed.

1st. The second charger 2.5 uniformly applies a constant charge (positive polarity in this embodiment) to the surface of the photoreceptor drum 1 by its corona discharge.

1st. The second optical system 3.6 is the first optical system. Second driver circuit 32
．． 62, the first. This is for forming a predetermined image as a negative electrostatic latent image on the surface of the photoreceptor drum 1 using laser light from a second laser diode (hereinafter referred to as LD) 31.61. Each driver circuit 32.62 is controlled by the image control section 22 described below.
The first optical system 3 creates ruled lines as an image, and the second optical system 6 creates predetermined characters printed within the ruled lines as an image.

1st. The second developing device 4.7 is of a magnetic brush type and includes a developing sleeve 41 containing a magnetic roller. The first developer 4 contains a first developer made of a mixture of insulating color toner (for example, red toner) and small-diameter magnetic carrier, and the second developer 7 contains an insulating black toner and a small-diameter magnetic carrier. A second developer consisting of a mixture with a small diameter magnetic carrier is contained.

Further, the color toner is located in a more negative direction than the black toner on the triboelectric charging array, and when the color toner mixes into the second developing device 7, it comes into contact with the black toner and is triboelectrically charged to a negative polarity. This charging characteristic is opposite in polarity to the charging characteristic (positive polarity) of the photoreceptor drum l. Further, in this embodiment, each toner is triboelectrically charged to a positive polarity, and the carrier is triboelectrically charged to a negative polarity. In addition, 1. As the second developing device 4.7, multiple developing devices of the same type are prepared, each containing a developer containing various toners with different tones, and it is possible to form a two-color image using any combination of colors. In order to do so, it is said to be replaceable.

Next, the structure and general operation of the developing device will be explained using the second developing device 7 as an example.

FIG. 2 is a sectional view of a main part showing the structure of the second developing device 7. As shown in FIG.

As shown in FIG. 2, the second developing device 7 has an N pole and an S pole in the circumferential direction.
A magnetic roller 72 whose poles are sequentially magnetized is built into the developing sleeve 71, and a scraper 73 is provided on the outer peripheral surface of the developing sleeve 71.
The tips of a and 73b are pressed together.

Further, a packet roller 74 having a packet 74a is provided near the developing sleeve so as to be rotatable in the direction of arrow e.
Furthermore, a developer guide plate 75 is located close to the developing sleeve 71.
, a carrier collection roller 76, and a duct 79 are provided.

The carrier recovery roller 76 rotatably accommodates a magnetic roller 77 therein, and the tip of a scraper 78 is pressed against its outer peripheral surface. Further, a dust collector equipped with a suction fan (not shown) is connected to the duct 79.

The developing sleeve 71 and the magnetic roller 72 are driven to rotate in the direction of the arrow C, and the developer receives a conveying force in the direction of the arrow C by the rotation of the developing sleeve 71, and also receives a conveying force in the direction of the arrow d by the rotation of the magnetic roller 72. The developing sleeve 71 receives a conveying force, and is conveyed in the direction of arrow d on the outer circumferential surface of the developing sleeve 71 due to the difference between the two conveying forces.

That is, the developer supplied to the lower part of the developing sleeve 71 in each packet 74a of the packet roller 74 is conveyed along the outer peripheral surface of the developing sleeve 71 in the direction of arrow d as described above, and when passing through the developing area A, the developer is The second optical system formed by the second optical system 6
The electrostatic latent image is developed and then scraped off with a scraper 73a. Further, as the developing sleeve 71 rotates in the direction of arrow C, the developer transported in the same direction is scraped off by the scraper 73b.

On the other hand, the carrier attached to the surface of the photosensitive drum 1 is captured by the outer peripheral surface of the carrier recovery roller 76 by the magnetic force of a magnetic roller 77 rotatably provided in the carrier recovery roller 76, and the magnetic roller 77 is used for developing. The magnetic roller 72 in the sleeve 71 is rotated synchronously in the direction of the arrow f by the magnetic force, thereby being transported on the outer peripheral surface of the carrier recovery roller 76 in the direction of the arrow g, and is scraped off by the scraper 78 .

Next, the image control section 22 will be explained with reference to FIG.

This image control section 22 is connected to the first image control section 22. Second driver circuit 32
．． 62 to generate a desired image signal, and also to generate a signal for creating a reference image for toner supply control. It also includes image selection means 20 that gives priority to the second image when there is an overlap between the first image and the second image.

That is, the first stroke sample number M outputted from the CPU 21 using a microcomputer is read by the reading circuit 23a.
When the second image sample number M2 is read by the reading circuit 23b and an image priority signal (operated by the operator) that gives priority to the second image is input by the image selection means 20, both image signals M, , M2 are read by the reading circuit 23b. are compared in the comparison circuit 24, and the signal M' of only the overlapped part is inputted to the erasure circuit 26 via the storage circuit 25, where the overlapped part signal M' is erased from the first image sample number M1, and the The signal is stored in the memory circuit 27a.
to be memorized.

Further, the second Nm signal Mt is stored as it is in the storage circuit 27b. Image signals in the memory circuits 27a and 27b are read by driver circuits 32.62, and converted into laser light signals by operating the first and second LDs 31.61. Here, the first (or second) driver circuit 32 (or 6
2) and the memory circuit 27a (or 27b).
(or second) first (or second) don't counter 50 (or second) for detecting the light emission time of LD 31 (or 61);
or 51) is interposed, so that the consumption amount of color toner (or black toner) can be detected.

The first (or second) dot counter 50 (or 51) counts the light emitting time of the first (or second) LD 31 (or 61) per a certain period of time, that is, the number of dots in a certain period of time. The counting results are given to the CPU 21.

Further, the converted laser light signal is scanned on the surface of the photoreceptor drum l in the axial direction (main scanning direction) to form a negative electrostatic latent image. Incidentally, a sensor 33 is installed at the scan start end of the first optical system 3 with respect to the photoreceptor drum 1. This sensor 33 is for instructing the driver circuit 32.62 to start reading an image, and outputs this instruction signal when laser light is incident on the sensor 33. A delay circuit 28 is interposed with respect to the second driver circuit 62, and reading of the second image sample number is started after a certain period of time from the instruction signal from the sensor 33. here,
The fixed time is the time required for the image formation start point of the photosensitive drum 1 to reach the second exposure position from the first exposure position.

On the other hand, when the image priority signal is not issued from the image selection means 20, the first image sample number Ml is stored as it is in the storage circuit 27a without passing through the comparison circuit 24.

The reference image pattern circuit 29 stores a reference image pattern for toner replenishment control, and controls the first and second driver circuits 32 and 62 to change the image on the photoreceptor drum 1 for each image formation. First, reference latent images for controlling the toner of the first developing agent and those for controlling the toner of the second developer are formed at one end separated from the forming section with their positions shifted in the rotational direction. This reference latent image is formed in the first and second developing units 4, respectively.
At step 7, the image is reversely developed under the same conditions as the image, and transferred together with the image onto the transfer paper 16. Immediately after the transfer, one density detection sensor 18 detects the density at a certain timing.

The density detection sensor 18 is an optical type consisting of a light emitting element and a light receiving element, and detects the amount of toner adhering to the reference image as a reflection density. The detected value here is the toner replenishment control circuit 19.
The toner density in the developer in each developing device 4.7 is compared with the reference reflection density when it is at the set value.

When the detected reflection density is lower than the reference reflection density, a toner replenishment signal is issued, and the first and second toner replenishment means 4
2.43 is activated to replenish a predetermined amount of toner into the developer in the first and second developing devices 4.7.

FIG. 3 is a block diagram showing a schematic configuration of the CPU 21. The first dot counted by the second dot counter 50.51. The light emitting time of 2nd LD 31.61 is CPU
21 to the comparison unit 210 in which the first LD 31
The light emitting time of the light emitting time is compared with a predetermined value, and the two light emitting times are compared. Signals of the two comparison results are given to the separation control section 211, and when the light emission time of the first LD 31 is longer than a predetermined value, a separation signal indicating this is given to the drive control section 212 in order to shift to a separation mode to be described later. Also two LD3
The operation time of the separation mode is determined by the difference in the light emission time of L61. The drive control unit 212 controls the drive of the photoconductor drum 1 and various devices around it, and when it receives the separation signal, it controls the photoconductor drum motor, the first . Second electrification charger 2
, 5. On/off control of the second developing device 7.

Further, the CP[I 21 receives a control signal and an image signal sent from a host computer (not shown), processes the control signal, sends it to the drive control section 212, processes the image signal, and processes the first and second image signals. The second image sample numbers M, , M, are output.

Next, the operation of the image forming apparatus of the present invention will be explained. FIG. 4 is a flowchart showing the control contents of the CPU 21.

First, when the power is turned on, RAM and ROM (not shown)
Then, an initial setting process is performed to initialize the contents of registers and counters in the CPU 21 (step 510), and a timer that determines the time of the print operation is set to time A.
1st. The light emission time of the second LD 31.61, that is, the first LD.
Second dot counter count value L1. Reset L2 (step 511). Next, data processing is performed with the host computer (step 512), a control signal and an image signal are received from the host computer, a printing operation is performed based on them (step 513), and the count value L
1 and L2 in the current print operation. 2nd LD31
．． The count value 11.12 indicating the light emission time of 61 is added and the count values Ll and L2 are integrated (step 514).
, this integration process is performed at the first . 2nd L
The light emitting time of D31.61 is added, and the total toner consumption is calculated based on this integrated value. The printing operation here is as shown in FIG. 5, in which the photosensitive drum 1 is rotated at a constant speed in the direction of the arrow a, first, the first charging charger 2 charges the drum with a first charge. The surface of the photoreceptor drum 1 is charged to a potential of Vo.

Next, a first exposure is performed in the first optical system 3, and the potential of the image area is reduced to approximately Ov, and a negative electrostatic latent image of the image, such as a ruled line, is formed. Then, the first developing device 4
First development is performed at . This development is performed while applying a developing bias of Vb to the developing sleeve 41, and the positively charged color toner Tc is applied to the image area (charge erased area).
It is a reversal development that adheres to the surface.

Next, second charging is performed in the second charging charger 5,
The surface of the photosensitive drum 1 is returned to a potential of approximately Vo. Subsequently, a second exposure is performed in the second optical system 6, and the potential of the image area is reduced to approximately OV, forming a negative electrostatic latent image of an image such as a character within a ruled line. Then, the second developing device 7 performs second development. This development is performed while applying a developing bias of vb to the developing sleeve 71,
This is a reversal development in which positively charged black toner Tb adheres to the image area (charge erased area), and a second image is formed overlapping the first image.

At this time, the color toner Tc mixed in the second developing device 7 comes into contact with the black toner Tb and is frictionally charged to a negative polarity. This charging polarity is the opposite polarity (negative polarity) to the charging polarity (positive polarity) of the surface of the photoreceptor drum 1, so that the color toner Tc that is negatively charged has a charging potential V at the time of second development.
Since the transfer charger has the same polarity (negative polarity), it is removed from the surface of the photoreceptor drum 1 by the cleaning device 10 without being transferred to the transfer paper 16.

On the other hand, the transfer paper 16 is conveyed as a continuous paper in the direction of the arrow on the path shown by the light chain line in FIG.
The toner Tc is discharged with negative polarity.

After the toner Tb is transferred, the toner Tc and Tb are melted and fixed by a fixing device (not shown). This completes the printing operation.

Note that the charge on the photosensitive drum 1 is erased by an eraser lamp 8 immediately before the transfer process.

The photosensitive drum 1 continues to rotate in the direction of arrow a even after the transfer, residual toner is removed by a cleaning device 10, and residual charges are erased by a main routine 11.

The processing contents of the print operation are as shown in FIG.
31) When a page feed command is input, the print flag F is set to 1, the photosensitive drum 1 is rotated, and the first page feed command is input. 2nd charger 2°5, 1st charger 2°5. second developing device 4,
7 and transfer charger 9 (Step 5133)
, 1st. The second LD 31.61 is controlled to perform a normal printing operation (step 5136), and the process returns to the main routine.

If a page break command has not been input, each device turned on is turned off in step 5133, and the process returns to the main routine.

When the integration processing is completed, it is determined in step S15 whether or not the printing operation has ended. If it has not been completed, the process returns to step 513 and the printing operation is continued. 516), reset the print flag F (step 517), and compare the integrated count value L1 with the first predetermined value a (step 518). When the count value L1 is smaller than the first predetermined value a (Ll<a+), it is determined that the color toner consumption is still small (and the color mixture is within the allowable level, and step S
Return to ll. When L1≧a, the count value L1 is compared with the second predetermined value at (step 519), and L1≧a
When the value is 2, a comparison is further made with a third predetermined value a (step 520).

In this way, the count value and the three predetermined values al r at r
``3, and when a1≦Ll<a, the coefficient T that determines the timer value B, which will be described later, is set to 1 cent (step 522), and when at≦Ll<a, the coefficient T is
.

is set to 2 cents (step 523), and when L1≧a3, the coefficient TI is set to 4 cents (step 521). Next, the count value L1 is compared with the same count value L2 (step 524).
, the timer value B depending on their magnitude relationship and degree.
A reference value T2 is determined. When the count value L1 is larger than the same L2, that is, when the consumption amount of color toner is greater than the consumption amount of black toner, the reference value T is set to 60 (seconds), and Ll
When <L2, it is then determined whether L1≧0.6L2 (step 526), and when Ll<0.6L2, further L is determined.
Determine whether or not 1≧0.2L2 (step 528) That is, in these steps S24, 26, and 28, the magnitude relationship between the count value L1 and the same L2 is determined in four stages, and 0.6L is determined.
When 2≦Ll<L2, set the reference value T to 50 (seconds)
Step 527), 0.2L2≦[, I
When < 0.6L2, T value = 40, Ll < 0.2L
2, set Tt=20 (step S
29.530), and the timer value B is obtained by multiplying the cent coefficient T1 by the reference value Tt (step 531).
), the mode shifts to the separation mode (step 532). FIG. 7 is a flowchart showing the processing contents of the separation mode. Step 5321),
Photosensitive drum 11 1st. The second charger 2.5 and the second developing device 7 are turned on and driven, and the second developing device 7 is turned on and driven.
The color toner (negative polarity) mixed inside the photoreceptor drum
and removed from the second developing device 7 (step 5322).

On the other hand, some of the color toner mixed into the second developing device 7 may be neutralized by contact with the carrier. The color toner whose charge amount has been neutralized to almost zero in this way tends to become dusty smoke, and becomes dusty smoke at the nod [B] on the upstream side of the development side conveyance direction of the development area A. This toner powder smoke is collected and removed through a duct 79 in the second developing device 7 which is maintained at negative pressure by a suction fan.

Then, it waits for the timer set in step 5321 to end (step 5323), turns off each device that was turned on in step 5322 (step 5324), and returns to the main routine.

When returning to the main routine, the process returns to step S11 and moves to the next image processing.

In this embodiment, the consumption amounts of color toner and black toner are determined based on the first. Although the detection is performed using the count value of the don't counter that counts the light emission time of the second laser diode, the present invention is not limited to this. For example, the color and black toner replenishment times of the first and second developer toner replenishment means Alternatively, the consumption amounts of color toner and black toner may be detected based on the number of times of replenishment.

Furthermore, in this embodiment, the number of dots is counted for a certain period of time using a don't counter, and the amount of color toner consumed is thereby detected. The amount of toner consumption may also be detected.

〔effect〕

As explained above, in the present invention, each time an image forming operation is completed, values related to the consumption amounts of the first developer and the second developer are detected by counting the number of dots, the amount of toner replenishment, the number of times of toner replenishment, etc. When the consumption amount of the first developer exceeds a predetermined value, the control is automatically transferred from the image forming operation to the color mixing and separation operation, and the time for performing the color mixing and separation operation is determined based on the relationship between the two values. Since the first developer mixed in the second developing means is removed, color mixture separation is properly performed according to the amount of mixture, and an equivalent effect is achieved in which a clear two-color image with less color mixture can always be obtained.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing a schematic configuration of a two-color laser beam printer, which is a two-color image forming apparatus according to the present invention, together with the configuration of a control system, and FIG. 2 is a main part showing the structure of a second developing device. A cross-sectional view, Figure 3 is a block diagram showing the configuration of the CPU, and Figure 4 is a block diagram showing the configuration of the CPU.
5 is a flowchart showing the main routine control content of the CPU, FIG. 5 is a flowchart showing the operation during printing, FIG. 6 is a flowchart of the printing operation, and FIG. 7 is a flowchart showing the processing content in the separation mode. 1... Photosensitive drum 2... First charging charger 3
...First optical system 4...First developer 5...Second
During charging 6...Second optical system 9...Transfer charger 10...Cleaning device 21...C
PU 50, 51...First and second dot counters 210...Comparison unit 211...Separation control unit Patent Applicant Minolta Camera Co., Ltd. Representative Patent attorney Noboru Kono Figure (a) 1st charge v 2nd charge Fig. wa Fig.

Claims (1)

[Scope of Claims] 1. First and second developers disposed around a rotating photoreceptor and having different colors and characteristics are stored separately, and a latent image formed on the photoreceptor is developed. a mixing separation means for separating the first developer of the first developing means on the upstream side mixed into the second developing means on the downstream side in the rotational direction of the photoreceptor based on the characteristics; a two-color image forming apparatus that performs an image forming operation and a color mixing and separating operation simultaneously or sequentially, comprising: a first developer that separately detects values related to consumption amounts of the first developer and the second developer; , a second consumption amount detection means, and a mixture separation control means for controlling the operation of the mixture separation means based on the detected value related to the consumption amount of the first and second developer. Two-color image forming device.