JPH0460653A - Image forming device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an image forming apparatus such as a copying machine or a laser beam printer, and particularly to an image forming apparatus capable of forming a multicolor image.

Conventionally, in image forming apparatuses such as electrophotographic copying machines and laser beam printers, environmental sensors detect changes in the environment in which the developer is placed for a certain period of time in order to keep the density of the formed image constant. The image forming conditions are changed by a control means based on the history of environmental changes and the type of developer.

In addition to this control, even when the environment detection result of the device main body and the environment where the developer is placed are different, such as immediately after the start of use of the device, there is a means to rewrite the stored environmental data, thereby allowing the Image forming apparatuses in which forming conditions can be controlled have also been proposed.

However, in the conventional example described above, the environmental conditions inside the developer and the machine may change, such as when the environmental data is not measured for a predetermined period of time when the power is turned on, or when the developer is used immediately after opening the package. Since the stored environmental data is rewritten at different times, the rewritten environmental data and newly measured data are mixed together, making it impossible to obtain an accurate environmental history. Each time the environmental data is rewritten, the absolute moisture content (mixing ratio), which is a control parameter, must be recalculated, which has the disadvantage of being time consuming.

Therefore, the purpose of the present invention is to correct the environmental data not by rewriting the environmental data (but only within a certain period of time), even when the environmental detection results cannot be obtained accurately, such as immediately after equipment repair, or immediately after opening the developer. Image formation that is capable of always forming images with appropriate density by preparing image formation parameters that are effective and whose correction amount decreases over time, and setting image formation conditions using a combination of these parameters and environmental history. The purpose is to provide equipment.

The above objects are achieved by an image forming apparatus according to the present invention. To summarize, the present invention provides an image forming method in which an electrostatic latent image is formed on a static N latent image carrier, and an image is formed by visualizing the electrostatic latent image using a developing means that develops the electrostatic latent image. The apparatus includes: environment detection means for detecting the environment in the vicinity of the developing means; storage means for storing the detection results of the environment detection means for a predetermined period of time; and setting means for setting image forming conditions for determining image density. , a counting means for counting time,
The image forming apparatus is characterized in that image forming conditions for determining image density are set based on the contents of the counting means and the contents of the storage means.

According to a preferred embodiment of the present invention, the environment sensing means detects absolute humidity near the developing means.

According to another preferred embodiment of the present invention, the image forming conditions include the charging potential and exposure amount of the electrostatic latent image carrier, the electrostatic latent image potential of the electrostatic layer image carrier, and the development of the developing means. It is determined by the bias potential.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Example 1 Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 is a schematic sectional view of an embodiment in which the present invention is applied to an electrophotographic color image forming apparatus, and shows the configuration of an electrophotographic color printer equipped with a developing device called a so-called rotary developing device. shows. This type of color printer has a latent image carrier, in this example a photosensitive drum 3, which is rotatably supported and rotates in the direction of the arrow, and an image forming means is arranged on the outer periphery of the latent image carrier. This image forming means may be any means, but in this example, a primary charger 4 that uniformly charges the photoreceptor drum 3 and a color-separated light image or a light image equivalent thereto are irradiated to the photoreceptor drum 3. The photosensitive drum 3 includes an exposure means 26 formed of, for example, a laser beam exposure device, which forms an electrostatic latent image on the drum 3, and a rotary developing device 1, which converts the electrostatic latent image on the photoreceptor drum 3 into a visible image.

The rotary developing device 1 includes four developing devices IY and IM each housing four color developers, for example, a yellow developer, a magenta developer, a cyan developer, and a black developer.
, IC1IBK, and these four developing devices IY, IM, I
It is composed of a substantially cylindrical casing that holds C1IBK and is rotatably supported. The rotary developing device 1
By the rotation of the housing, a desired developing device is conveyed to a position facing the outer peripheral surface of the photoreceptor drum 3, and the electrostatic latent image on the photoreceptor drum is developed. It is constructed so that full-color development can be performed. In addition, each developing device has four hoppers that separately store four color developers: yellow developer, magenta developer, cyan developer, and black developer from the developer (toner) replenishing device 2. Replenish toner of the corresponding color from 2Y, 2M, 2C, and 2BK as needed.

Next, regarding the overall operation of the color printer with the above configuration,
A brief explanation will be given using the full color mode as an example. First, the photosensitive drum 3 is uniformly charged by the primary charger 4. Next, image exposure is performed using laser light E modulated by the yellow image signal of the original (not shown).
An electrostatic latent image is formed on the photoreceptor drum 3, and the electrostatic latent image is developed by a yellow developer IY placed in advance at a developing position.

On the other hand, paper feed guide 5a, paper feed roller 6, paper feed guide 5b
The transfer paper P fed via the gripper 7 is held by the gripper 7 in synchronization with a predetermined timing, and is electrostatically wound around the transfer drum 9 by the contact roller 8 and its opposite pole. The transfer drum 9 rotates in the direction of the arrow shown in the figure in synchronization with the photosensitive drum 3, and the developed image developed by the yellow developer IY is transferred to the transfer paper P by the transfer charger 10 in the transfer section.
transcribed into. The transfer drum 9 continues to rotate and prepares for the transfer of a developed image of the next color (magenta in FIG. 2).

After the photosensitive drum 3 is neutralized by the charger IJ and cleaned by the cleaning member 12, it is uniformly charged again by the primary charger 4 and exposed to the next magenta image signal in the same manner as described above. During this time, the developing device 1 rotates and the magenta developing device IM is fixed at a predetermined developing position, and predetermined magenta development is performed. Next, the same process as above is performed for cyan and black, and when the transfer of the four colors is completed, the four-color developed image on the transfer paper is neutralized by the charger 13 and 14, and the transfer paper is By releasing the gripper 7 and operating the separation claw 15, the image is separated from the transfer drum 9, sent to a fixing device (thermal roller fixing device) 17 by a conveyor belt 16, fixed thereon, and discharged outside the machine. Ru. Thus, a series of full-color printing operations is completed, and a desired full-color print image is formed.

Furthermore, in this embodiment, in addition to the above configuration, a humidity sensor and a temperature sensor are installed at positions where the moisture absorption of the toner is well reflected, such as near the toner hoppers 2Y, 2M, and 2C12BK or near the developing device. An environmental sensor 19 is equipped.

Next, the control system of the color printer having the above configuration will be explained.

FIG. 1 is a block diagram showing one embodiment of the present invention, -
a primary high voltage power supply 4a that supplies the required high voltage to the wide charger 4;
A grid bias power supply 4b supplies a required bias voltage to the grid of the primary charger 4, which controls the amount of charge applied to the photoreceptor drum 3 to a desired value, and a grid bias power supply 4b supplies the required bias voltage to the grid of the primary charger 4, which controls the amount of charge applied to the photoreceptor drum 3 to a desired value. )
A control means 18, such as a microcomputer, is provided to control each of the developing bias power supplies 1a that apply . Data signals regarding humidity and temperature from the environmental sensor 19 are input to the control means 18, and 8-force signals from the potential sensor 20 for detecting the surface potential of the photoreceptor drum 3 are also input to the control means 18. Furthermore, the control means 1
Reference numeral 8 denotes an operation unit 21, a random access memory (RAM) 22 as a storage means, and a read-only memory (ROM) in which control contents for each of the above-mentioned power supplies are stored.
23 and a timer 24.

The operation of the control system having the above configuration will be explained below.

FIG. 3 is a graph showing the relationship between the grid bias voltage (horizontal axis) and the surface potential of the photoreceptor drum 3 (vertical axis), and curve ■ in the figure. represents the surface potential when not irradiated with light, and curve 2 represents the surface potential when irradiated with light. From the same figure, the surface potential V. , that is, the amount of charge is the grid bias voltage V within the usage range. is proportional to. In addition, the surface potential VL after light irradiation has a similar tendency, but the ratio of change to the amount of change in grid bias voltage V0,
In other words, the proportionality coefficient is V. is larger than ■, the third
As shown in the figure, if the proportional coefficient of Vo is α and the proportional coefficient of VL is β, then there is a relationship α>β. Therefore, before performing the print sequence, the control means 18 sets the grid voltage to the preset grid voltage. 1 and V. V at 2. , VL are measured by the potential sensor 20, and from each measurement data, the change in grid voltage as shown in FIG. 3 is determined. , VL are assumed. After that, when actually forming an image, the image contrast V is determined from the charging curve obtained by the above-mentioned operation. oNT, that is, the difference between the DC component of the developing bias described below and the surface potential after light irradiation, or ■. -VL becomes a predetermined value by calculating the grid voltage, and from this, the grid bias power supply 4b
control.

Further, the control means 18 is set at a constant potential 8 from VD to prevent toner from adhering to the part corresponding to the white background of the image (in this embodiment, since the reversal development method is used, the part corresponding to Vo). A developing bias having a low value is determined, and the developing bias power supply 1a is controlled using this value.

Figure 4 is a graph showing the influence of image density on humidity when printing under the same image forming conditions.As shown in the figure, under the same image forming conditions, the lower the humidity, the lower the density, and the higher the humidity. As the concentration increases, the concentration increases. Therefore, by detecting the humidity, determining the contrast potential V C0NT corresponding to the detected humidity, and setting the image forming conditions based on that value, it is possible to obtain a stable image regardless of changes in environmental conditions. becomes possible. In addition, as shown in the figure, since the density relative to humidity differs depending on the color, if the image forming conditions are made variable for each color, it is possible to compensate for the difference in image density due to the difference in developer color. I can do it.

Next, the operation of this embodiment will be specifically explained based on the flowcharts shown in FIGS. 8(a) and 8(b), FIG. 9, and FIG. 10.

First, processing A will be explained using FIGS. 8(a) and 8(b). The temperature is measured by the environmental sensor 19, for example, once every 30 minutes or several times every 30 minutes, and the average value is stored in the buffer area of the memory (RAM) 22 for 8 hours. At this time, if the control means 18 has not operated before, such as when the power is turned on (determination block S1), the current environmental data for eight hours is stored in the buffer (block S2). Next, the mixing ratio (absolute humidity) is calculated from the 8 hours' worth of environmental data using a predetermined formula and stored in the RAM 22.
The average values x, y, and z of the mixing ratio (absolute humidity) for 1 hour, 4 hours, and 8 hours are calculated, respectively (block S3). These average values x, y, and Z are used for the condition determination described below, and are used as a variable H when calculating the contrast potential, which will be described later. First, in judgment block S4, it is judged whether the 2-hour average value
．． If it is 5g or more, set the contrast flag to C0NT1. This indicates that the high temperature state continued for more than 2 hours. Next, in judgment block S5, the current value W is 16.5.
It is determined whether or not it is greater than 16.5 g, and if it is greater than 16.5 g, the contrast flag is set to C0NT2. This indicates that the humidity has been low for two hours but is now heading towards high temperatures. Next, in judgment block S6, it is judged whether the average value 2 for 8 hours is 9 g or more, and if it is 9 g or more, the contrast flag is set to C0NT3. This indicates that the humidity should remain at medium temperature for 8 hours or more. Next, in judgment block S7, it is judged whether the average value y for 4 hours is 9 g or more, and if it is 9 g or more, the contrast flag is set to C0NT4. This indicates that we are heading towards low humidity to moderate temperatures. In cases other than the above, that is, when the average value y for 4 hours is 9 g or less, it is determined that the humidity is low and the contrast flag is set to C0NT5.

Incidentally, the above processing is performed because the rate of moisture absorption and dehumidification of the toner is different depending on whether the toner goes from low humidity to high temperature or from high temperature to low temperature. That is, image density is proportional to absolute humidity, but this is determined not by the humidity of the atmosphere (but by how much moisture the toner absorbs), and therefore the above-mentioned condition judgment is performed.

Next, in block S8, a variable H for contrast calculation is determined using the contrast flag.

For example, in the case of C0NT 1, the humidity is completely controlled to a high level, so the variable H becomes the average value X for 2 hours.

Furthermore, in the case of C0NT 2, the condition is between low humidity and high humidity, so the variable H is (X+W)/2, which is the average value of the 2-hour average value X and the current value W.

The general formula for calculating contrast potential is: ■ Where c is contrast potential and a and b are coefficients, V c = a H+
It becomes b. Here, H is the variable described above. Table 1 shows the contrast flags (CONTI, C0NT2, C0NT
This is part of a list of variable H1 coefficients a and b corresponding to development colors (magenta M, cyan C, yellow Y, black BK). This content is stored in the ROM 23, and the coefficients a and b of the calculation formula are calculated from the contrast and development color information.
and how to select variable H (block S8).
. From this search result, contrast potential ■. Calculate (
Block S9).

Table 1 Figure 5 plots the above calculation formula. As shown in the figure, since the coefficients are changed for each color, it is possible to absorb and correct the difference in density change for each color shown in FIG. 4.

Here, the time-limited contrast potential, which is the main purpose of this embodiment, will be explained with reference to FIGS. 6 and 7. ■ Contrast potential as described above. Even if the toner was determined, the required density was often not output because the environment of the machine body and the environment in which the toner was placed were different, such as when using toner immediately after opening the package. Therefore, in the present invention, the maximum time T until the developer adapts to the current environment is...
A time-limited contrast correction value vct for correcting the contrast potential Vc calculated up to 8 is prepared. Figure 6 is ■.

This is a diagram showing the relationship between and time, and the familiarization time T□8
After that, V, , =O. Although this embodiment shows an example in which Vct>0 at the start of time-limited contrast correction, it is also possible to set vct<0, and the magnitude of each absolute value can be freely controlled from the operation unit 21. It can now be set to . In addition, in FIG. 6, a linear function is assumed in which {circle around (2)} monotonically decreases with the passage of time, but more complex control is also possible if the changes in Vet are tabulated as necessary.

FIG. 7 is a diagram comparing the case with and without the correction shown in FIG. 6. Contrast potential V is used to make the explanation easier to understand. is assumed to remain constant over time.

Returning to FIG. 8(b), if the time-limited contrast correction described above is required (decision block 5ll), the timer 24 counts the elapsed time from the start of correction.
Based on this coefficient result, the time-limited contrast correction value y e
Compute t (block 512). When time-limited contrast potential correction is not necessary, ct=0 is set (block 513), and contrast potential calculation, which will be described later, is performed.

Next, contrast potential correction (without time limit) will be explained.

Unlike the time-limited contrast potential described above, the contrast potential is constantly corrected. This is used, for example, when the contrast potential Ve does not output an appropriate density due to variations in each developer. Contrast correction value V
Since cc can be freely set using the operation unit 21 and is stored and backed up in the RAM 22, the data is saved even when the power is turned off, and the contrast potential can be corrected as long as the value is not changed. If there is a correction of this contrast potential (decision block 514), a contrast correction value Vcc is calculated (block 515). If there is no correction, contrast is calculated as vec:O (block 816). The contrast potential Ve obtained in this way, the time-limited contrast correction value V ct,
When all contrast correction values Vee are added, the control contrast potential becomes ■ゎ. 7. determines (block 517)
. Since these values are calculated independently for each developing color used, the operation ends after the calculations for the four colors are completed (decision block 818).

Next, processing B will be explained using FIG. 9. Processing B
The relationship between the grid bias voltage v6 and the surface potential V shown in FIG. 3 described above is measured when the laser is on and when the laser is off. The photoreceptor drum 3 is rotated in the same way as in the normal copy sequence, and - the secondary pressure source 4a is
Turn on. Next, a predetermined value Va+ is output from the grid bias power supply 4b (block 5100), and the surface potential Vo+ of the photosensitive drum 3 is measured by the potential sensor 20 and stored in the memory (block 5101). Next, the laser is turned on to irradiate the photoreceptor drum 3 with the maximum amount of light, and the surface potential V Ll after the laser light irradiation is measured and stored in the memory (block 5102). Next, VO2 in Figure 3
, vLt, the grid bias from the grid bias power supply 4b is set to another predetermined value ■. □ Next step 5103), VL2 is similarly measured and stored in memory (block 5104). Next, ■. The laser is turned off to measure 2, and Vow is measured and stored in memory (block 5105). Then, the secondary pressure power source 4a and the grid bias power source 4b are turned off to complete the operation.

Note that the order of turning on/off the laser and the timing of the grid bias voltages Va+ and Vat may be changed depending on the sequence. Further, in this embodiment, the potentials were measured when the laser was turned on and off, but it is also possible to measure the potentials of a plurality of sample outputs using a laser output system capable of multi-value output. Further, processing A and processing B are independent of each other, and either one may be performed first (and the timing of the processing may not be simultaneous).

Next, processing C will be explained based on FIG. 10. Note that processing C must be performed after processing A and B.

First, Vol, Vo2 and measurement data ■l) 1, Vo
The slopes α, β, and α-β of the respective charging curves shown in FIG. 3 for Vo and VL from w, VLI, and V Ll are calculated according to the following equations (block 5200).

Next, the aforementioned fog removal voltage V stored in the buffer area of the memory and the contrast voltage V cant calculated in Process A are read out (block 5201). and grid bias voltage V. This ■. The voltage obtained is determined by the sum of ant and 6. That is, the following calculation is performed (block 5202).

Once the grid bias voltage is determined using the above formula, Vo is then calculated (block 5203).

Vo = G (Va Va+) + V.

Furthermore, in block 5204, the DC components (2) and (2) of the developing bias are determined.

V dI,=V o −V s When it is determined that the above processing has been completed for the four colors (decision block 5205), the processing is ended.

As described above, the grid bias control value Vo and the developing bias control value ■6° have been obtained for the four colors.

The grid bias and development bias determined in this way take into account environmental conditions, and also take into account differences in environmental conditions for each color, so that an extremely stable image with an appropriate density can be obtained.

Next, how to operate the process A, process B, and process C will be explained in detail using an example of the operation section 21.

In the present invention, as described above, the history of temperature and humidity is a factor in determining the image forming conditions. However, since the toner filled in the machine at the time of installation has been adjusted to the moisture content of the environment sealed at the time of shipment from the factory, the environment may be completely different from the environment at the time of installation. In such a case, the image (density) is adjusted using the time-limited contrast correction of process A.

FIG. 11 shows a liquid crystal operation section 21a which is an example of the operation section 21. As shown in FIG. The display on the LCD operation unit 21a is a screen in the so-called service mode used by service personnel when making adjustments.The cursor 21b in the figure indicates the sheet number setting key (numeric keypad), density key, start key, stop key, etc. (not shown). It can be moved freely to the required position using keys etc.

Furthermore, the setting value at the position pointed to by the cursor 21b can be changed freely using a numeric keypad or the like. Further, the number in parentheses at the current position in the figure pointed by the cursor 21b indicates the initial value of time-limited contrast correction, and corresponds to Vctl in FIG. 6. The number immediately to the left indicates the current timed contrast control value.
Control value V when time T8゜1 has elapsed from the start of restriction
Corresponds to c tz. In FIG. 11, a time-limited contrast correction value Vct, a contrast correction value Vec, and a fog removal potential vIl can be set.

Next, a method of adjustment by a service person will be explained using FIG. 12.

First, set the initial value of time-limited contrast correction,
Control begins (block 5300).

The above-mentioned processes A, B, and C are executed from a screen not shown, and control values such as block 5301), vc611t%vt1, etc. are determined. Next, an image sample is collected in the normal copy mode (block 5302), and it is determined whether the density is appropriate (decision block 5303). If the concentration is not appropriate, start over from the initial setting.

In this way, the time-limited contrast correction can be set in the service mode, and T ma,
When the time elapses, the timed contrast control value ■. = 0, so when the developer is adapted to the current environment, normal environment correction control is performed, so that an appropriate image can always be obtained.

In the above embodiment, the grid bias voltage is ■. , the DC component of the developing bias voltage v61. Although the output density was adjusted by controlling the -order high voltage VP and the exposure E, the output density can also be controlled by adjusting the -order high voltage VP and the exposure E. A second embodiment of the present invention using this system will be described below with reference to FIG. This second embodiment is also an electrophotographic color printer having the same configuration as that shown in FIG. 1, but in this embodiment, a laser control unit 25 is added as an exposure source. This laser control unit 25 is composed of a known laser drive circuit, a polygon mirror, an f-theta lens, etc., and the laser light intensity is controlled by the control means 18. Note that the other configurations are the same as those in Figure 1, so
Corresponding parts are given the same reference numerals and their explanations will be omitted.

When controlling the charging current and laser light intensity for the primary charger 4 described above, a plurality of experimental data showing the relationship between the charging current and the surface potential are used, as shown in a representative example in FIG. The curve pattern and a plurality of curve patterns, which are experimental data showing the relationship between the laser light intensity (exposure amount) and the surface potential, are stored in advance in the ROM 23, as shown in FIG. 15 as a typical example. Then, one curve pattern is selected from among the plurality of curve patterns according to the value of the detected surface potential to control the charging current value and laser light intensity.

In the above embodiments, the present invention was applied to an electrophotographic color printer, but it goes without saying that the present invention is equally applicable to various digital and analog type printers, copying machines, and other image forming apparatuses. .

! (7) As is clear from the above description, the image forming apparatus according to the present invention can perform development even when the environment in which the main body of the apparatus is placed and the environment in which the developer is sealed are significantly different. Since the density can be corrected only during the time it takes for the agent to adapt to the environment, there is a remarkable effect that images with appropriate density can always be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of an image forming apparatus according to the present invention. FIG. 2 is a schematic cross-sectional view showing the internal structure of the image forming apparatus shown in FIG. FIG. 3 is a diagram showing the relationship between the grid bias voltage and the surface potential of the photoreceptor drum. FIG. 4 is a diagram showing density changes with respect to humidity for each color of developer. FIG. 5 is a diagram showing the relationship between set contrast potential and humidity. FIG. 6 is a diagram showing the concept of time-limited contrast correction. FIG. 7 is a diagram showing the relationship between the time-limited contrast correction value and the contrast potential. FIGS. 8(a) and 8(b), FIG. 9, and FIG. 10 are flowcharts showing the control procedure of the first embodiment of the present invention, respectively. FIG. 11 is a schematic diagram showing a display example of the liquid crystal operation section of the operation section according to the first embodiment of the present invention. FIG. 12 is a flowchart showing a control procedure for contrast correction operation according to the first embodiment of the present invention. FIG. 13 is a schematic configuration diagram showing a second embodiment of an image forming apparatus according to the present invention. FIG. 14 is a diagram showing the relationship between the primary charging current and the surface potential of the photosensitive drum. FIG. 15 is a diagram showing the relationship between the exposure amount and the surface potential of the photoreceptor drum. 1: Rotary developing device 3: Photosensitive drum 4, Primary charger 4a, Primary high voltage power source 4b, Nigellid bias power source 7: Shield plate bias power source 18, 2 Control means 19: Environment sensor 20: Potential sensor 21: Operation unit 22 : Memory (RAM) 23: Memory (ROM) 24: Timer 25: Laser control unit 26: Exposure means Humidity α) 5αX 4 C0NT3 C0NT2 Cα
Figure 1 Figure 6 Figure 7 (Time) Figure 8 (b) Figure 9 Figure 11 Figure 12 Figure 10 Figure 14 Charging current (arbitrary unit) Figure 15 Exposure amount (arbitrary unit)

Claims (1)

[Scope of Claims] 1) Image formation in which an electrostatic latent image is formed on an electrostatic latent image carrier and an image is formed by visualizing the electrostatic latent image using a developing means that develops the electrostatic latent image. The apparatus includes: environment detection means for detecting the environment in the vicinity of the developing means; storage means for storing the detection results of the environment detection means for a predetermined period of time; and setting means for setting image forming conditions for determining image density. , and counting means for counting time, and setting image forming conditions for determining image density based on the contents of the counting means and the contents of the storage means. 2) The image forming apparatus according to claim 1, wherein the environment detection means detects absolute humidity. 3) The image forming condition is determined by the charging potential of the electrostatic latent image carrier, the exposure amount, the electrostatic latent image potential of the electrostatic latent image carrier, and the developing bias potential of the developing means. The image forming apparatus according to claim 1.