JPH10198194A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of performing stable transfer regardless of the change of the environment. SOLUTION: In the image forming device applying electrophotographic system, by forming plural toner pattern in the same density on a photoreceptor, and letting the transferring output successively changed for every toner pattern, the respective toner pattern is transferred on recording paper, transfer film or the like. Then, on detecting transfer efficiency of the respective toner pattern being transferred, based on such as the detected transfer efficiency of the respective toner pattern, transferring condition and the developing condition is severally controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming apparatus such as a copying machine employing an electrophotographic system.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine employing an electrophotographic system, it is desired that an image having a constant density for the same image data be reproduced on a recording paper. In response to this demand, in order to reproduce a stable density image on recording paper, before performing copying, or when a predetermined mode is set, a toner pattern of a constant density formed on the photoconductor is formed. An image forming apparatus that detects a transfer efficiency on the recording paper when the image is transferred onto the recording paper at a constant transfer output, and controls a transfer condition based on the detected value so that the transfer efficiency is equal to or higher than a reference value. It is known (for example, the device disclosed in Japanese Patent Application Laid-Open No. 5-134561).

[0003]

In [0006] Conventional image forming apparatus is controlled so that the transfer efficiency is higher than the reference value by controlling the transfer output, the transfer current becomes the reference transfer efficiency eta _ref or best It is not possible to determine whether the values are appropriate. FIG. 1 is a diagram showing the transfer efficiency for each transfer output. A transfer characteristic under a certain environment is shown by a solid line graph. At the output A, a transfer efficiency equal to or higher than the reference transfer efficiency η _ref is obtained. However, even if the transfer characteristic slightly changes to a graph shown by a dotted line due to a change in environment, it is impossible to obtain a transfer efficiency higher than the reference transfer efficiency η _ref at the output A. For this reason, in the conventional image forming apparatus,
A series of control processes such as formation of a reference pattern, detection of transfer efficiency, comparison with a reference value, and switching of a transfer output must be frequently performed, and frequent adjustment time is required before the image forming process is started. Will be.

An object of the present invention is to provide an image forming apparatus which performs stable image formation irrespective of environmental changes.

[0005]

According to a first aspect of the present invention, there is provided an image forming apparatus employing an electrophotographic method, comprising: a toner pattern forming means for forming a plurality of toner patterns having the same density on a photosensitive member; Transfer means for continuously changing the transfer output for each toner pattern to transfer each toner pattern onto recording paper; transfer efficiency detecting means for detecting the transfer efficiency of each toner pattern transferred onto recording paper;
A control unit is provided for controlling transfer conditions based on the transfer efficiency of each toner pattern detected by the transfer efficiency detection unit. By monitoring the transition of the transfer efficiency of each toner pattern resulting from the continuous change of the transfer output by the transfer means, more appropriate transfer condition control can be performed.

According to a second image forming apparatus of the present invention, in an image forming apparatus employing an electrophotographic system, a toner pattern forming means for forming a plurality of toner patterns of the same density on a photoreceptor; Transfer means for continuously changing the transfer output to transfer each toner pattern onto recording paper; transfer efficiency detecting means for detecting the transfer efficiency of each toner pattern transferred onto the recording paper; A characteristic amount detecting means for detecting at least one of a charge amount immediately before transfer of a toner pattern formed on a recording sheet; a transfer efficiency detected by the transfer efficiency detecting means; and a resistance detected by the characteristic amount detecting means. Control means for controlling the transfer conditions based on one or both of the value and the charge amount. In this way, the transfer efficiency of the toner pattern as a result of continuously changing the transfer output by the transfer means is monitored, and the resistance value of the recording paper, the charging immediately before the transfer of the toner pattern formed on the photoconductor, are monitored. By detecting one or both of the amounts, the states of the recording paper and the toner can be accurately grasped, and more appropriate control of the transfer conditions can be performed.

In a third image forming apparatus of the present invention,
In an image forming apparatus adopting an electrophotographic method, a toner pattern forming means for forming a plurality of toner patterns of the same density on a photoreceptor, and a transfer output for each toner pattern are continuously changed to print each toner pattern on a recording paper. Transfer means for transferring the toner pattern onto the film, transfer efficiency detecting means for detecting the transfer efficiency of each toner pattern transferred onto the recording paper and the film, and controlling the transfer condition based on the detection result by the transfer efficiency detecting means. Control means. By monitoring and comparing the transfer efficiency of the toner pattern onto the recording paper and the transfer efficiency onto the film resulting from the continuous change of the transfer output by the transfer means, the transfer of the recording paper and the toner is performed. The state can be accurately grasped, and more appropriate control of the transfer condition can be performed.

Further, in the image forming apparatus employing the fourth electrophotographic method of the present invention, a toner pattern forming means for forming a plurality of toner patterns of the same density on a photosensitive member, and a transfer output for each toner pattern are continuously performed. Change,
Transfer means for transferring each toner pattern onto the transfer film, transfer efficiency detection means for detecting the transfer efficiency of each toner pattern transferred on the transfer film, and transfer efficiency of each toner pattern detected by the transfer efficiency detection means Control means for controlling the transfer condition based on the The transfer conditions can be more appropriately controlled based only on the transfer efficiency to the transfer film. Further, in the image forming apparatus employing the fifth electrophotographic method of the present invention, a toner pattern forming means for forming a plurality of toner patterns of the same density on the photoreceptor, and the transfer output is continuously changed for each toner pattern. Let
Transfer means for transferring each toner pattern onto the transfer film, transfer efficiency detection means for detecting the transfer efficiency of each toner pattern transferred on the transfer film, and transfer efficiency of each toner pattern detected by the transfer efficiency detection means Control means for controlling the development conditions based on the The development conditions can be more appropriately controlled based only on the transfer efficiency to the transfer film.

[0009]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of an image forming apparatus according to a first embodiment of the present invention; In these drawings, those given the same reference numerals indicate the same or similar ones. (1) First Embodiment FIG. 2 is a sectional view of a digital full-color copying machine according to a first embodiment. The copying machine is broadly divided into an image reader unit 100 for reading an image of a document and a printer unit 200 for forming an image on a recording sheet based on image data of the read document. Image reader unit 100
The document placed on the platen glass 1 is illuminated by a lamp 3 provided in the scanner 2. Light reflected from the document surface forms an image on a CCD line sensor 8 via mirrors 4, 5, 6 and an imaging lens 7. The scanner 2 is moved by the scanner motor 10 in the direction of the arrow (sub-scanning direction) at a speed of V according to the set magnification. Thus, the original placed on the original platen glass 1 is scanned over the entire surface. The mirrors 5 and 6 also move in the arrow direction (sub-scanning direction) at the speed of V / 2 with the movement of the scanner 2. The R, G, and B multi-valued electrical signals obtained by the CCD line sensor 8 are converted to 8-bit gradation data by the read signal processing unit 9 and then output to the printer unit 200. Note that an operation panel 50 for setting the number of copies and executing the copy is provided above the image reader unit 100. The operation panel 50 is provided with an execution key for performing a transfer output adjustment process (not shown). When the execution key of the transfer output adjustment process is pressed, the transfer output adjustment process is executed in a procedure described later.

In the printer section 200, the print head section 20 generates a laser diode drive signal based on the gradation data input from the read signal processing section 9, and causes the semiconductor laser to emit light in accordance with the drive signal. The laser beam emitted from the print head unit 20 is
The surface of the photosensitive drum 23 is exposed and scanned via 1 and 22. The surface of the photoconductor drum 23 is irradiated with an eraser lamp 24 before being exposed for each copy, and is uniformly charged by a charging charger 25. When exposure is performed in this state, an electrostatic latent image of the document is formed on the photosensitive drum 23. Of the cyan, magenta, yellow, and black toner developing units 27 to 30, first, the cyan toner developing unit 2
7 is selected, and the electrostatic latent image on the photosensitive drum 23 is developed. Appropriate recording paper (including OHP sheets if set) is transported from the paper feed cassettes 31 to 33 to the timing roller pair 34. Timing roller pair 34
Transports the recording paper to the transfer drum 40 at a timing when the leading edge of the toner image developed on the photosensitive drum 23 coincides with the leading edge of the recording paper. The transfer drum 40 includes a transfer film on an outer surface portion. The transported recording paper is transferred to the transfer drum 4 by the suction charger 35 and the suction roller 37.
0 is electrostatically attracted to the transfer film. The pressing member 36
The transfer drum 40 is pressed in the direction of the attraction roller 37 in order to bring the recording paper into close contact with the transfer drum 40 and to make the recording paper adhere more strongly. The cyan toner image developed on the photoconductor drum 23 is transferred to a recording paper wound around the transfer drum 40 by the transfer charger 38. The pressing member 39 presses the transfer drum 40 in the direction of the photosensitive drum 23 in order to increase the degree of adhesion between the recording paper and the photosensitive drum 23 and enhance transferability. The toner remaining on the photosensitive drum 23 after the transfer of the toner image is removed by the cleaner 26. Subsequent to cyan, magenta, yellow, and black toner developing units are sequentially selected, and charging, exposure, and
Then, toner development is performed. The toner images of each color developed on the photosensitive drum 23 are sequentially transferred onto the recording paper wound on the transfer drum 40 in a superimposed manner. The recording paper on which the toner images of the four colors have been transferred is destaticized on the surface of the transfer drum 40 by the separation static elimination charger 41, and then pushed up by the push-up member 42. Thus, the transfer drum 40 is separated from the surface. The recording paper separated from the transfer drum 40 is discharged to a tray 45 after being fixed through a fixing device 44. The transfer film on the surface of the transfer drum 40 is discharged by the transfer film discharging chargers 46a and 46b after the recording paper is separated. Further, the toner adhering to the transfer film is removed by the cleaner 47.

The resistance value of the paper and the amount of toner charge affect the transfer efficiency when a toner image visualized on the photosensitive drum 23 is transferred onto recording paper. The characteristics of the recording paper and the toner charge amount will be described below. If the recording paper absorbs moisture or dries due to the surrounding environment, its electrical characteristics change. FIG. 3 is a graph showing the relationship between the volume resistivity (Ω · cm) of the recording paper and the absolute humidity (g / m ³ ). As you can see from this graph, as the absolute humidity increases,
The volume resistance of the recording paper decreases. Further, the charge amount of the toner before being transferred to the recording paper also changes depending on the humidity. FIG.
Is a graph showing the relationship between the toner charge amount (μC / g) before transfer and the absolute humidity (g / m ³ ). As can be seen from the graph, as the absolute humidity increases, the toner charge amount before transfer decreases.

Next, an example in which the two values of the resistance value of the paper (transfer material) and the toner charge amount before the transfer greatly affects the transfer characteristics will be described. FIG. 5 shows that the image was output by changing the transfer output (charge wire current of a transfer charger to be described later) after allowing the apparatus to stand for 7 to 8 hours in each of the three environments to adjust to the environment. 6 is a graph showing a change in toner density in the case. The curve represented by the solid line is the temperature 23
It shows the characteristics under the environment of ° C and 50% RH. When the transfer output is within the range of L1, the transfer efficiency becomes the best and the toner density on the recording paper becomes the maximum. The toner density gradually decreases when the transfer output exceeds about 400 μA. The curve represented by the broken line is a temperature of 18 ° C. and a humidity of 20%.
This shows the characteristics under the environment of RH. As compared with the case of the humidity of 50% RH, the rate of increase of the toner density with the increase of the transfer output is low, and the transfer efficiency is the best, that is, the value of the transfer output at which the toner density is maximized is large. The toner density on the recording paper becomes maximum when the transfer output is within the range of L2. The toner density decreases more gradually than when the transfer output exceeds 550 μA and the humidity is 50% RH. The curve represented by the dashed line indicates the characteristics under the environment of a temperature of 28 ° C. and a humidity of 80% RH. As can be understood from the graph, the increase rate of the toner density with the increase in the transfer output is higher than that in the case of the humidity of 50% RH, and the toner density sharply increases.
The toner density is maximized when the transfer output is in the range of 100 to 300 μA, and drops sharply from the point where the transfer output exceeds 300 μA as compared with the case where the humidity is 50% RH.
As understood from the above three characteristic curves, when the humidity is high, the rate of increase of the toner density with the increase of the transfer output increases, and the rate of decrease after reaching the maximum density also increases.
When the humidity is low, the rate of increase of the toner density with the increase of the transfer output decreases, and the rate of decrease after reaching the maximum density also decreases. In addition, the range of the transfer output in which the maximum toner density can be obtained is wider when the humidity is lower. The proper transfer output area at the time of high humidity will be described with reference to FIG. As shown in FIG. 5, when the humidity is high (for example, 80% RH), the range of the transfer output at which the toner density is maximum on the paper is much narrower than when the humidity is low. This is because the timing at which the toner density starts to decrease particularly on the high output side is early. As shown in FIG. 4, the decrease in the toner density on the high output side is caused by the fact that the toner charge amount is reduced in a high humidity environment and the toner is charged to the opposite polarity by the transfer output of the transfer charger 38. The major cause is that the toner remains on the photosensitive drum 23 without being transferred onto the paper. This reverse charging of the toner can be prevented by increasing the toner charging amount to some extent. Also,
As shown in FIG. 3, the resistance value of the recording paper also decreases with an increase in humidity, but when the resistance value is sufficiently high, the transfer output can be suppressed low, and the reverse charging of the toner can be suppressed.

FIG. 6 shows a detailed configuration and a control system around the photosensitive drum 23 and the transfer drum 40 of the copying machine according to the first embodiment. The control system mainly includes the CPU 14. The CPU 14 has a RAM 1 as a work area.
3 and a ROM 16 storing control data such as a control table described later. The environment sensor 15 for detecting the humidity of the environment and the toner concentration detection sensor 213 provided on the downstream side of the transfer unit are connected to the RAM 13. The transfer charger 38 includes a transfer charger high voltage (HV) power supply 2 for supplying a charge wire current (hereinafter referred to as a transfer output).
12 are connected. The CPU 14 controls the high-voltage power supply 21
2 is controlled. In addition, four developing devices 27 to 3
A high voltage (HV) power supply for supplying a developing bias voltage of 0 is also controlled by the CPU 14.

At the time of normal copying, the CPU 14 detects the absolute humidity of the printer unit 200 by the environment sensor 15, and changes the transfer output based on the result to keep the transfer efficiency constant. Table 1 is a control table for specifying a transfer output corresponding to the detected absolute humidity. This control table is a table used for forming a full-color image in a normal copy mode, and is stored in the ROM 16 together with various control data. As shown in Table 1, based on the experimental data, the transfer output is set to increase as the absolute humidity decreases. The transfer output in each humidity section is set so as to increase in order from the first color to the second color, from the second color to the third color, and so on. This takes into account the effect of charge-up of the transfer film due to the output of the previous color. The ROM 16 stores, as data, the relationship between the representative transfer output corresponding to each humidity category shown in Table 1 and the toner density transferred to the recording paper after humidity control.

[0015]

[Table 1]

When the execution key of the transfer output adjustment processing provided on the operation panel 50 is pressed, the CPU 14 executes the transfer output adjustment processing according to the flowchart shown in FIG. Hereinafter, the contents of the processing will be described according to the flow of this flowchart with reference to the related drawings. First, a toner pattern is formed (Step S1). The formation of the toner pattern is performed in the following procedure. First, the print head unit 20 emits light at a constant interval and with a constant light amount to form 17 line-like latent image patterns P1 to P17 on the photosensitive drum 23. Under the same conditions, the formed latent image patterns P1 to P17 are
7 to make a visible image. Developed toner pattern P1
P17 to P17 are transferred to the recording paper wound around the transfer drum 40 in the transfer section. FIG. 8 is a graph showing the transfer output between the leading edge and the trailing edge of the recording paper when forming the toner pattern. As shown in the drawing, the transfer output is increased stepwise from 0 μA to 800 μA in 17 steps from the edge of the recording paper. FIG. 9 shows toner patterns P1 to P17 transferred onto recording paper when the transfer output is changed stepwise, as shown in the graph of FIG.
FIG. Next, the density (image density) of the toner patterns P1 to P17 transferred onto the recording paper is measured by a toner density detection sensor 213 provided on the downstream side of the transfer section, and RA is measured.
It is stored in M13 (step S2). Then, the darkest pattern is detected from the toner patterns P1 to P17 transferred on the recording paper, and the transfer output at this time is specified (step S3).

The transfer output specified in step S3 changes with time according to the degree of humidity control of the recording paper. In FIG.
The dashed curve shows the transfer efficiency when the recording paper before humidity control is used when the absolute humidity detected by the environment sensor 15 is lower than that of the recording paper, and the solid curve shows the transfer efficiency after the humidity control. The transfer efficiency when a recording paper is used is shown. As shown, as the humidity control progresses, the amount of toner transferred onto the recording paper at the lower transfer output side changes greatly. This is because under relatively low humidity conditions, as shown in FIG. 4, the amount of charge of the toner before transfer is high, and on the high output side, the reverse charge of the toner does not occur even if the resistance value of the recording paper changes due to humidity control. On the other hand, on the low output side, the humidity of the recording paper advances, and as the absolute humidity decreases, the resistance increases and the dielectric constant of the paper decreases, resulting in a change in transfer efficiency. That's why. On the other hand, in FIG. 11, when the absolute humidity detected by the environment sensor 15 is higher than that of the recording paper, the dashed curve indicates the transfer efficiency when the recording paper before humidity control is used, and the solid line indicates the transfer efficiency. The curve shows the transfer efficiency when using the recording paper after humidity control. As shown in the figure, as the humidity control progresses, the amount of the toner transferred onto the recording paper changes greatly on the side where the transfer output is higher. This is because, as shown in FIG. 4, the charge amount of the toner is relatively low under the condition of relatively high humidity, and on the high output side, the humidity of the recording paper advances as shown in FIG. This is because the resistance value decreases and reverse charging of the toner easily occurs. On the other hand, on the low output side, since the charge amount of the toner is sufficiently low with respect to the transfer output, the transfer efficiency does not largely change even if the resistance value of the recording paper changes due to humidity control.

Next, the transfer condition (transfer output) is corrected in consideration of the above-mentioned change in the transfer characteristic due to the humidity control of the recording paper. Specifically, the density of the toner patterns P3 and P15 detected when the transfer output is 100 μA and 700 μA,
The difference is obtained by comparing the density with the density to be obtained when using the recording paper adjusted to the absolute humidity detected by the environment sensor 15 (step S4). The density data to be obtained when the humidity-controlled recording paper is used is stored in the ROM 16. The shift amount is specified based on Table 2 and Table 3 based on the obtained density difference, and a value shifted by the specified shift amount from the transfer output value at which the maximum density is obtained is set as the transfer output (step S).
5). As described above, by correcting the transfer output in consideration of the change in the transfer efficiency due to the humidity control of the recording paper, it is possible to control appropriate transfer conditions corresponding to the change in the humidity control state of the paper.

[0019]

[Table 2]

[Table 3]

Next, the transfer output specified by the control table in Table 1 corresponding to the absolute humidity detected by the environment sensor 15 is compared with the transfer output set in step S5 (step S6), and there is a difference. In this case, the relationship between the absolute humidity classification and the transfer output in the control table is shifted so that the transfer output set in step S5 is selected (step S7). Here, shifting the control table means, for example, reducing the value of the transfer output as a whole by a predetermined shift amount (for example, 50 μA). The control table corrected in this way is stored in the RAM 13,
Until the transfer output adjustment processing is performed next, it is used to control the transfer output during the normal copy execution.
If processing for four colors has not been completed (N in step S8)
O), a series of control processes of steps S1 to S7 are repeatedly executed by the number of magenta, yellow, and black toner developing devices in addition to cyan. After the control process for the four colors is completed (YES in step S8), the process ends.

In the above-described method of forming a toner pattern, a total of four recording papers are used. However, the width and interval of the toner pattern are narrowed to form a pattern for four developing units on one recording paper. You may. In addition, since the characteristics of the developing materials in the four developing devices due to time and environment hardly change, the toner pattern is formed on one developing device as a representative without forming the toner patterns repeatedly for the four developing devices. The transfer conditions may be controlled based on the density of the pattern. As means for measuring the density transferred onto the recording paper, a toner density detection sensor 213 is provided downstream of the transfer section.
Alternatively, the print image discharged to the paper discharge tray 45 may be placed on the platen glass 1 and read by the CCD line sensor 8, and the transfer conditions may be controlled based on the read image data.

(2) Second Embodiment Next, a digital full-color copying machine according to a second embodiment of the present invention will be described. Hereinafter, portions different from the copying machine of the first embodiment will be described. In the copying machine according to the second embodiment, when the execution key of the transfer output adjustment process provided on the operation panel 50 is pressed, the photosensitive drum 23 is pressed.
A plurality of toner patterns having the same density are formed thereon, and the toner patterns are transferred onto recording paper while changing the transfer output for each toner pattern. Then, in addition to detecting the toner density as data representing the transfer efficiency on the paper at each transfer output, there are three pieces of information such as the resistance value of the recording paper, the charge amount of the toner before transfer, and the relationship between the transfer output and the toner density. The transfer condition is controlled based on Monitor the transition of the transfer efficiency of each toner pattern transferred on the recording paper,
By detecting the resistance value of the recording paper and the charge amount immediately before the transfer of the toner pattern formed on the photoreceptor, environmental changes,
For example, an appropriate transfer condition that is not affected by the humidity control state of the recording paper is set. FIG. 12 is a diagram illustrating a more detailed configuration around the photosensitive drum 23 and the transfer drum 40 of the copying machine according to the second embodiment. In the copying machine according to the second embodiment, the first
In addition to the toner density detection sensor 213 provided in the copying machine (FIG. 6) of the embodiment, a voltage application unit 81, a resistance value measurement unit 82, a pre-transfer charger 108 for raising the toner charge immediately before transfer, and a toner just before transfer A sensor 109 for detecting the amount of adhesion and a sensor 110 for measuring the surface potential of the photosensitive drum 23 immediately before transfer are provided. Voltage application unit 81
During the time when the recording paper passes through the pair of timing rollers 34,
A predetermined voltage is continuously applied to the connected roller. The resistance value measuring unit 82 measures a current value flowing through the recording paper, and obtains a resistance value of the recording paper from the measured current value and a voltage value applied by the voltage applying unit 81. The obtained resistance value is RA
M13 and further sent to the CPU 14 via the RAM 13. The CPU 14 determines the transfer condition based on the measured three values of the resistance value of the recording paper, the toner charge amount before transfer, and the transfer output and the toner density. (HV) The output of the power supply 131 and the output of the high voltage power supply 212 of the transfer charger 38 are controlled.

FIG. 13 is a flowchart of the transfer output adjustment process executed by the CPU 14 when the execution key of the transfer output adjustment process provided on the operation panel 50 is pressed. A toner pattern is formed on the photosensitive drum 23 (Step S10). To form the toner pattern, the print head unit 20 emits light at a constant interval and with a constant light amount, and 17 line-like latent image patterns P1 to P1 are formed on the photosensitive drum 23.
P17 is formed, and the latent image patterns P1 to P17 are visualized by the cyan toner developing device 27 under the same conditions. Next, the toner charge amount per weight is obtained from the toner adhesion amount measured by the pre-transfer toner adhesion amount sensor 109 and the potential on the toner pattern measured by the potential sensor 110 (step S11). Instead of the process executed in step S11, the developing current flowing through the developing sleeve of the developing device at the time of development is measured, and the measured developing current and the information of the toner adhesion amount measured by the toner adhesion amount sensor 109 before transfer are measured. Based on this, the toner charge amount per weight may be determined. Next, the resistance value of the recording paper conveyed to the timing roller pair 34 is measured by the voltage application unit 81 and the resistance value measurement unit 82 (step S1).
2). The toner pattern formed on the photosensitive drum 23 is transferred onto the recording paper wound around the transfer drum 40 (Step S13). Then, toner patterns P1 to P1 are detected by a toner density detection sensor 213 provided on the downstream side of the transfer section.
The concentration of P17 is measured and stored in the RAM 13 (Step S14). Next, the relationship between the transfer output and the toner density stored in the ROM 16 and the toner density of each toner pattern written in the RAM 13, which is specified from the absolute humidity value detected by the environment sensor 15, is compared. (Step S15). As a result of the comparison, since the absolute humidity detected by the environment sensor 15 is relatively high, the charge amount of the toner has decreased.
When the actual density of the toner pattern written in the AM 13 drops greatly on the high transfer output side and the resistance value of the recording paper measured by the resistance value measuring unit 82 is high, for example, the maximum density value and , The difference in density at 700 μA is 0.5 mg / cm ² or more, and the resistance value of the recording paper is 1 ×
If it is equal to or greater than 10 ⁹ Ω (YES in step S16, NO in step S17), the output of the pre-transfer charger 108 is increased, and the toner charge amount before transfer is increased (step S1).
8). Thus, sufficient transfer efficiency can be obtained without modifying the control table. Further, since the absolute humidity detected by the environment sensor 15 is relatively high, the charge amount of the toner is reduced.
13, the density of the actual toner pattern written in 13 falls greatly on the high transfer output side, and the resistance value of the recording paper measured by the resistance value measuring unit 82 is low.
For example, the difference between the maximum concentration value and the concentration at 700 μA is 0.
5 mg / cm ² or more, and the resistance value of the recording paper is 1 × 10 ⁷
Ω (YE in steps S16 and S17)
S), it is determined that simply increasing the output of the pre-transfer charger 108 cannot cope with the change in the resistance value of the recording paper, and the following steps S19 to S26 are executed. First, the output of the pre-transfer charger 108 is increased (step S1).
9) A toner pattern is formed again with the toner charge amount being raised (step S20). The density of the toner patterns P1 to P17 formed on the recording paper is measured by the toner density detection sensor 213 (step S21), and the transfer output with the maximum density is specified (step S2).
2). Next, the transfer output is corrected in consideration of the change in the transfer characteristics due to the humidity control of the recording paper. Specifically, the transfer output is 10
The densities of the toner patterns P3 and P15 detected at 0 μA and 700 μA are compared with the densities to be obtained when using the recording paper after humidity control to the absolute humidity detected by the environment sensor 15. Each difference is determined (step S23). The shift amount is specified based on Table 2 and Table 3 based on the obtained difference in density, and a value shifted by the specified shift amount from the transfer output value at which the maximum density is obtained is set as the transfer output. (Step S2
4). As described above, by setting the transfer output in consideration of the change in the transfer efficiency due to the humidity control of the recording paper, it is possible to control appropriate transfer conditions corresponding to the change in the humidity control state of the paper.

Thereafter, the transfer output specified by the control table shown in Table 1 corresponding to the absolute humidity detected by the environment sensor 15 is compared with the transfer output set in step S24. (YES in S25),
The relationship between the absolute humidity classification and the transfer output in the control table is shifted so that the transfer output set in step S24 is selected (step S26). The shifted control table is stored in the RAM 13 and is used to control the transfer output during normal copy execution until the transfer output adjustment processing is performed next. If the processing for four colors has not been completed (NO in step S27), steps S10 to S10 are performed.
A series of control processes in S26 are repeatedly executed by the number of magenta, yellow, and black toner developing devices in addition to cyan. After the control process for four colors is completed (YE in step S27)
S), the process ends. In the second embodiment, based on the charge amount of the toner before the transfer and the resistance value of the recording paper, whether the cause of the decrease in the transfer efficiency is due to the deterioration of the toner or the decrease in the resistance value of the recording paper. Is determined.In addition to the transfer efficiency of each toner pattern, only one of the resistance value of the recording paper and the charge amount of the toner before transfer is detected,
The transfer condition may be controlled based on the detected value. For example, when the transfer efficiency and the resistance value of the recording paper are each equal to or less than the reference value, it is determined that the cause of the reduction in the transfer efficiency is the reduction in the resistance value of the recording paper in a high humidity environment, and the transfer charger is determined. Only the output of the HV power supply 212 is controlled. If the transfer efficiency and the charge amount of the toner before transfer are respectively equal to or less than the reference values, it is determined that the decrease in transfer efficiency is due to the deterioration of the toner, and the output of the high voltage power supply 131 of the charger 108 before transfer is determined. Only control.

(3) Third Embodiment Next, a digital full-color copying machine according to a third embodiment of the present invention will be described. Hereinafter, portions different from the copying machine of the first embodiment will be described. In the copying machine according to the third embodiment, when a predetermined mode is set before copying is performed, a plurality of toner patterns having the same density are formed on the photosensitive drum 23 as control processing for stabilizing the image density. Then, the transfer output is changed for each pattern and transferred to recording paper. Then, as data representing the transfer efficiency at each transfer output, the toner density remaining on the photosensitive drum 23 is detected, and the transfer output is controlled based on the detected value. By monitoring the transition of the transfer efficiency of each toner pattern transferred onto the recording paper, an appropriate transfer condition that is not affected by environmental changes, for example, the humidity control state of the recording paper, is set. FIG. 14 is a diagram illustrating a more detailed configuration around the photosensitive drum 23 and the transfer drum 40 of the copying machine according to the third embodiment. The same components as those of the copying machine according to the first embodiment are denoted by the same reference numerals, and redundant description will be omitted (see FIG. 6). The copying machine according to the third embodiment has a first
Toner density detection sensor 213 provided in copying machine of embodiment
Instead, a sensor 112 for detecting the concentration of the toner remaining on the photosensitive drum 23 is provided downstream of the transfer unit. FIG.
5 is a graph showing the transition of the residual toner concentration when the transfer output is changed after the apparatus is left for 7 to 8 hours to adjust to the environment under the three environments. The curve represented by the solid line shows the characteristics under the environment of a temperature of 23 ° C. and a humidity of 50% RH. A curve represented by a broken line indicates characteristics under an environment of a temperature of 18 ° C. and a humidity of 20% RH. The curve represented by the dashed line indicates the characteristics under the environment of a temperature of 28 ° C. and a humidity of 80% RH. As can be understood from the three curves, when the humidity is high, the rate of decrease in the residual toner density increases as the transfer output increases, and the rate of increase after reaching the maximum density also increases. When the humidity is low, the decrease rate of the residual toner density with the increase of the transfer output decreases, and the increase rate after reaching the maximum density also decreases. Further, the range of the transfer output in which the minimum residual toner concentration can be obtained is wider when the humidity is lower.

FIG. 16 is a flowchart of the transfer output adjustment processing executed by the CPU 14 when the execution key of the transfer output adjustment processing on the operation panel 50 is pressed. First, a toner pattern is formed (Step S30).
The formation of the toner pattern is performed in the following procedure. First,
The print head unit 20 emits light at a constant interval and a constant light amount, and 17 latent image patterns P
1 to P17 are formed. Formed latent image patterns P1 to P
17 is developed by the cyan toner developing device 27 under the same conditions. The developed toner patterns P1 to P17 are
The image is transferred to the recording paper wound around the transfer drum 40 by the suction unit. When performing this transfer, as shown in FIG.
The transfer output is increased stepwise for each toner pattern. Thereby, the toner patterns P1 to P17 shown in FIG. 9 are transferred onto the recording paper. Next, the toner concentration of the toner pattern remaining without being transferred onto the photosensitive drum 23 is detected by the residual toner concentration detection sensor 112, and the detected value is written in the RAM 13 (step S31). RAM 13
The transfer output that minimizes the density is specified by referring to the toner density of each toner pattern written in (step S).
32). Next, the transfer output is corrected in consideration of the change in the transfer characteristics due to the humidity control of the recording paper. Specifically, the transfer output is 1
The densities of the toner patterns P3 and P15 detected in the case of 00 μA and 700 μA are compared with the densities to be obtained when using the recording paper after humidity adjustment to the absolute humidity detected by the environment sensor 15. Each difference is determined (step S33). The density data to be obtained when the humidity-controlled recording paper is used is written in the ROM 16. The shift amount is specified based on Table 2 and Table 3 based on the obtained density difference, and a value shifted by the specified shift amount from the value of the transfer output at which the maximum density is obtained is set as the transfer output (step). S34). After this, CP
U14 compares the transfer output specified by the control table in Table 1 corresponding to the absolute humidity detected by the environment sensor 15 with the transfer output set in step S34, and if there is a difference (YES in step S35). ), So that the transfer output set in step S34 is selected
The relationship between the absolute humidity classification and the transfer output in the control table is shifted (step S36). The shifted control table is stored in the RAM 13 and is used to control the transfer output during the normal copy execution until the transfer output adjustment processing is performed next. If the processing for four colors has not been completed (NO in step S37), steps S30 to S3
A series of control processes of No. 6 is repeatedly executed by the number of magenta, yellow, and black toner developing units in addition to cyan. After the control process for four colors is completed (YE in step S37)
S), the process ends.

(4) Fourth Embodiment Next, a digital full-color copying machine according to a fourth embodiment of the present invention will be described. The parts different from the copying machine of the second embodiment will be described. In the copying machine according to the fourth embodiment, when the execution key of the transfer output adjustment process provided on the operation panel 50 is pressed, a plurality of toner patterns of the same density are formed on the photosensitive drum 23, and each toner pattern is formed. Change the transfer output and transfer to recording paper. Then, in addition to detecting the density of the toner remaining on the photosensitive drum 23 as data representing the transfer efficiency, the resistance value of the recording paper, the charge amount of the toner before transfer, and the relationship between the transfer output and the toner density The transfer condition is controlled based on the information. In this manner, the transition of the transfer efficiency of each toner pattern transferred onto the recording paper is monitored, and furthermore, the resistance value of the recording paper and the charge amount immediately before the transfer of the toner pattern formed on the photoconductor are detected. By grasping the characteristics of the recording paper and the toner and controlling the transfer conditions as necessary, it is possible to suppress a change in the environment, for example, a change in the transfer efficiency due to a change in the humidity control state of the recording paper. FIG. 17 shows a more detailed configuration around the photosensitive drum 23 and the transfer drum 40 of the copying machine according to the fourth embodiment. This copying machine includes a toner density detection sensor 21 provided in the copying machine of the second embodiment.
Instead of 3, a sensor 112 for detecting the concentration of the toner remaining on the photosensitive drum 23 is provided downstream of the transfer unit.
The sensor 112 is connected to the RAM 13.

FIG. 18 shows the CPU 1 when the execution key of the transfer output adjustment processing provided on the operation panel 50 is pressed.
4 is a flowchart of a transfer output adjustment process executed by a fourth embodiment. First, a toner pattern is formed on the photosensitive drum 23 (Step S40). The toner pattern is formed by causing the print head unit 20 to emit light at a constant interval and with a constant light amount, to form 17 linear latent image patterns P1 to P17 on the photosensitive drum 23, and to form the latent image patterns P1 to P17. P1
7 is visualized by the cyan toner developing device 27 under the same conditions. Next, the pre-transfer toner adhesion amount sensor 10
And the potential sensor 11
The toner charge amount per weight is obtained from the potential on the toner pattern measured by 0 (step S41). Instead of the process executed in step S41, a developing current flowing through the developing sleeve at the time of development is measured, and based on the measured developing current and information on the toner adhesion amount measured by the toner adhesion amount sensor 109 before transfer, The toner charge amount per weight may be determined. Further, the resistance value measuring unit 82
Then, the resistance value of the recording paper conveyed to the timing roller pair 34 is measured (step S42). Next, the toner pattern formed on the photosensitive drum 23 is transferred onto the recording paper wound around the transfer drum 40 (Step S43). Next, the residual toner concentration detection sensor 112
With this, the toner density of the toner pattern remaining without being transferred onto the photosensitive drum 23 is detected, and the detected value is stored in the RAM.
13 (step S44). And it is specified from the value of the absolute humidity detected by the environment sensor 15.
The relationship between the transfer output and the residual toner density stored in the ROM 16 in advance and the residual toner density of each toner pattern written in the RAM 13 are compared (step S4).
5). As a result of the comparison, since the absolute humidity detected by the environment sensor 15 is relatively high, the charge amount of the toner is reduced, and the actual residual toner density written in the RAM 13 in step S14 is higher than the higher transfer output. When the resistance value of the recording paper measured by the resistance value measuring unit 82 is high, for example, the difference between the minimum value of the residual toner density and the residual toner density at 700 μA is 0.
5 mg / cm ² or more, and the resistance value of the recording paper is 1 × 10 ⁹
Ω or more (YES in step S46, step S4
Then, the output of the pre-transfer charger 108 is increased to increase the charge amount of the pre-transfer toner (step S48).
Thus, sufficient transfer efficiency can be obtained without modifying the control table. Further, since the absolute humidity detected by the environment sensor 15 is relatively high, the charge amount of the toner is reduced.
If the actual density of the residual toner written on the recording paper greatly increases on the side where the transfer output is high, and the resistance value of the recording paper measured by the resistance value measuring unit 82 is low, for example, If the difference between the value and the residual toner concentration at 700 μA is 0.5 mg / cm ² or more and the resistance value of the recording paper is 1 × 10 ⁷ Ω or less (YES in steps S46 and S47), the output of the pre-transfer charger 108 is output. It is not possible to cope with a change in the resistance value of the recording paper only by increasing the Therefore, the following steps S49 to S56 are executed. First,
Increase the output of the pre-transfer charger 108 (step S4
9) A toner pattern is formed again with the toner charge amount raised (step S50). Toner patterns P1 to P remaining without being transferred onto photosensitive drum 23
The density of No. 17 is measured by the sensor 112 for detecting the residual toner density (step S51), and the transfer output that minimizes the density of the residual toner is specified (step S52). The transfer output is corrected in consideration of a change in transfer characteristics due to humidity control of the recording paper. Specifically, the transfer output is 100 μA and 700 μA.
Toner patterns P3 and P15 detected in case of μA
Is compared with the residual toner concentration to be obtained when using the recording paper after the humidity is adjusted to the absolute humidity detected by the environment sensor 15, and each difference is obtained (step S53). ). Note that the residual toner concentration to be obtained when the humidity-controlled recording paper is used is stored in the ROM 16. The shift amount is specified based on Table 2 and Table 3 based on the difference between the obtained residual toner densities, and a value shifted by the specified shift amount from the transfer output value at which the residual toner density becomes minimum is set as the transfer output ( Step S54).
As described above, by correcting the transfer output in consideration of the change in the transfer characteristics due to the humidity control of the recording paper, it is possible to suppress a large change in the transfer output due to the humidity control of the recording paper.

Thereafter, the transfer output specified by the control table shown in Table 1 corresponding to the absolute humidity detected by the environment sensor 15 is compared with the transfer output set in step S54. YE in S55
S), the relationship between the absolute humidity classification and the transfer output in the control table is shifted so that the transfer output set in step S54 is selected (step S56). The shifted control table is stored in the RAM 13 and is used to control the transfer output during normal copy execution until the transfer output adjustment processing is performed next. If the processing for the four colors has not been completed (NO in step S57), step S
A series of control processes from 40 to S56 is repeatedly executed by the number of magenta, yellow, and black toner developing devices in addition to cyan. After the end of the control process for four colors (step S5
Then, the process ends.

In the fourth embodiment, based on the toner concentration remaining on the photosensitive drum 23 after the transfer and the resistance value of the recording paper, it is determined whether the cause of the decrease in the transfer efficiency is due to the deterioration of the toner or the recording paper. Although it is determined whether the change is due to a decrease in the resistance value, in addition to the transfer efficiency of each toner pattern, only one of the resistance value of the recording paper and the charge amount of the toner before transfer is detected, and based on the detected value. Alternatively, the transfer conditions may be controlled. For example, when the transfer efficiency and the resistance value of the recording paper are each equal to or less than the reference value, it is determined that the cause of the reduction in the transfer efficiency is the reduction in the resistance value of the recording paper in a high humidity environment, and the transfer charger is determined. Only 38 outputs are controlled. If the transfer efficiency and the charge amount of the pre-transfer toner are respectively equal to or less than the reference values, it is determined that the decrease in the transfer efficiency is due to the deterioration of the toner.
08 is controlled only.

(5) Fifth Embodiment Next, a digital full-color copying machine according to a fifth embodiment of the present invention will be described. This copying machine has the same configuration as the copying machine of the first embodiment, but differs in the control of the transfer efficiency. In the copying machine according to the fifth embodiment, the operation panel 50
As a control process for stabilizing the image density when the execution key of the transfer output adjustment process provided in the printer is pressed, the transfer output is changed for each toner pattern by transferring a plurality of toner patterns having the same density on the photosensitive member. The density (toner adhesion amount) of the toner pattern when transferred onto the recording paper and the transfer film on the surface of the transfer drum 40, respectively,
The method is characterized in that the transfer conditions are detected as data representing the transfer efficiency, and the transfer conditions are controlled based on the comparison results of the respective detected values. In this way, by monitoring and comparing the transfer efficiency of each toner pattern transferred onto the recording paper and the transfer efficiency onto the film, the characteristics of the recording paper and the toner are grasped, and the transfer conditions are determined as necessary. To suppress a change in transfer efficiency due to a change in the environment, for example, a change in the humidity control state of the recording paper.

The transfer efficiency in the case where the recording paper is not conditioned and the case where the humidity is conditioned in a high humidity environment will be described below. FIG. 19 shows 28 ° C., 80% R
9 is a graph showing an amount (density) of toner transferred (adhered) onto a transfer target in accordance with each transfer output in an environment of H. The curve indicated by the solid line represents the amount of toner when a recording sheet that has not been subjected to humidity control is used as the transfer object. The curve shown by the broken line represents the amount of toner when the toner pattern is directly transferred onto the transfer film. When comparing the unadjusted recording paper and the transfer film, it can be seen that there is a difference in the absolute value of the attached toner, but the difference is substantially constant regardless of the transfer output.

FIG. 20 shows that each recording output is obtained when a recording sheet having a low resistance value after humidity control for 7 to 8 hours is used as an object to be transferred in an environment of 28 ° C. and 80% RH. 4 is a graph showing the amount of toner transferred onto a transfer object in response. The curve indicated by the solid line represents the amount of toner when the recording paper after humidity control is used as the transfer target. The curve shown by the broken line represents the amount of toner when the toner pattern is directly transferred onto the transfer film. In the case of the humidity control paper, it can be seen that not only the absolute value of the attached toner but also the difference greatly varies depending on the transfer output. In this way, for the recording paper and the transfer film, the amount of toner adhered to each transfer output is examined and compared to determine whether or not the resistance of the recording paper is reduced in a high-humidity environment due to humidity control. Can be determined. The relationship between the recording paper and the transfer film is a relationship that is established between a recording paper that absorbs moisture and a film such as an OHP sheet that does not easily absorb moisture.

FIG. 21 shows a case where the execution key of the transfer output adjustment processing provided on the operation panel 50 is depressed.
4 is a flowchart of a control process executed by a PU 14.
First, a plurality of toner patterns of the same density formed on the photosensitive drum 23 are transferred while changing the transfer output stepwise to form toner patterns P1 to P17 shown in FIG. 9 on the recording paper (step S60). , P stored on the recording paper
1 to P17 are measured (step S6).
1). Similarly, the toner patterns P1 to P17 are transferred onto the transfer film on the surface of the transfer drum 40 (Step S).
62), the toner pattern P formed on the transfer film
1 to P17 are measured (step S6).
3). Next, the density of the toner transferred on the recording paper is compared with the density of the toner transferred on the transfer film (step S64). Here, the difference is almost constant irrespective of the transfer output, but when the density is significantly reduced at both high outputs, for example, the difference between the maximum density and the density when the transfer output value is 700 μA is both 0. If it is 5 mg / cm ² or more, the resistance value of the recording paper has not decreased and is appropriate, but it is determined that the toner charge amount has decreased significantly (YES in step S65, NO in step S66), and
The output of the charger 108 before transfer is increased, and the charge amount of the toner is increased immediately before transfer. By this processing, a sufficient transfer efficiency can be obtained without modifying the control table.

On the other hand, as a result of comparing the density information at the time of transfer onto the transfer film and the density information at the time of transfer onto the recording paper, if the difference greatly differs depending on the output, and if the density decreases greatly at the time of high output, for example, The difference between the maximum density and the density when the transfer output is 700 μA is both 0.5 mg / cm ² or more, and the difference between the density on the recording paper and the density on the transfer film is 0.2 mg.
/ Cm ² or more, it is determined that both the resistance value of the recording paper and the toner charge amount have decreased (step S65).
And YES in S66), the following steps S68 to S75
Execute the processing of First, the output of the pre-transfer charger 108 is increased (step S68), and a toner pattern is formed again with the toner charge amount raised (step S69). The density of the toner patterns P1 to P17 remaining without being transferred onto the photosensitive drum 23 is
12 (step S70), the transfer output that minimizes the residual toner density is specified (step S71).
The transfer output is corrected in consideration of a change in transfer characteristics due to humidity control of the recording paper. Specifically, the transfer output is 100 μA and 7
The toner patterns P3 and P3 detected in the case of 00 μA
15 is compared with the residual toner concentration to be obtained when using the recording paper after the humidity is adjusted to the absolute humidity detected by the environment sensor 15, and the difference is obtained. S72). Then, based on the difference between the obtained residual toner densities, the shift amount is specified by Tables 2 and 3, and a value shifted by the specified shift amount from the transfer output value at which the residual toner density becomes minimum is set as the transfer output. (Step S73). As described above, by correcting the transfer output in consideration of the change in the transfer characteristics due to the humidity control of the recording paper,
It is possible to suppress a large fluctuation in the transfer output due to the humidity control of the recording paper.

Thereafter, the transfer output specified by the control table shown in Table 1 corresponding to the absolute humidity detected by the environment sensor 15 is compared with the transfer output set in step S73. YE in S74
S) The relationship between the absolute humidity classification and the transfer output in the control table is shifted so that the transfer output set in step S73 is selected (step S75). The shifted control table is stored in the RAM 13 and is used to control the transfer output during normal copy execution until the transfer output adjustment processing is performed next. If the processing for four colors has not been completed (NO in step S76), step S
A series of control processes from 60 to S75 is repeatedly executed by the number of magenta, yellow, and black toner developing devices in addition to cyan. After the end of the control process for four colors (step S7
(YES at 6), ends the process. Also, the paper cassette 3
A film such as an OHP sheet that is not easily absorbed by moisture is set in any one of the sheets 1-33, and in step S62, a sheet is fed from a sheet cassette in which the film is set.
The toner pattern may be transferred onto the film.

In the fifth embodiment, based on the toner density remaining on the photosensitive drum 23 after the transfer and the resistance value of the recording paper, it is determined whether the cause of the decrease in the transfer efficiency is due to the deterioration of the toner or the recording paper. Although it is determined whether the change is due to a decrease in the resistance value, in addition to the transfer efficiency of each toner pattern, only one of the resistance value of the recording paper and the charge amount of the toner before transfer is detected, and based on the detected value. Alternatively, the transfer conditions may be controlled. For example, when the transfer efficiency and the resistance value of the recording paper are each equal to or less than the reference value, it is determined that the cause of the reduction in the transfer efficiency is the reduction in the resistance value of the recording paper in a high humidity environment, and the transfer charger is determined. Only 38 outputs are controlled. If the transfer efficiency and the charge amount of the pre-transfer toner are respectively equal to or less than the reference values, it is determined that the decrease in the transfer efficiency is due to the deterioration of the toner.
08 is controlled only.

(6) Sixth Embodiment Next, a digital full-color copying machine according to a sixth embodiment of the present invention will be described. This copier has the same configuration as the copier of the third embodiment, but differs in the control of the transfer efficiency. When the execution key of the transfer output adjustment process provided on the operation panel 50 is pressed, the copying machine of the sixth embodiment performs a plurality of processes of the same density on the photosensitive drum 23 as a control process for stabilizing the image density. Forming a toner pattern of
The transfer output is changed for each toner pattern, and the amount of toner remaining on the photoconductor 23 after being transferred onto the recording paper and the transfer film on the transfer drum 40 is detected as data representing the transfer efficiency. It is characterized in that transfer conditions are controlled based on a comparison result of each detection value. The residual toner concentration detection sensor 112 disposed opposite to the photoconductor drum 23 measures the amount of toner remaining on the photoconductor drum 23 after transferring the toner pattern onto the recording paper and the transfer film. Both of these concentration information are RA
It is sent to M13 and CPU14. In this way, by monitoring and comparing the transfer efficiency of each toner pattern transferred onto the recording paper and the transfer efficiency onto the film, the characteristics of the recording paper and the toner are grasped, and the transfer conditions are determined as necessary. To suppress a change in transfer efficiency due to a change in the environment, for example, a change in the humidity control state of the recording paper.

The transfer efficiency in the case where the recording paper is not humidified and the case where the humidity is conditioned in a high humidity environment will be described below. FIG. 22 shows 28 ° C., 80% RH
6 is a graph showing the amount of toner remaining on the photosensitive drum 23 after being transferred onto a transfer target in accordance with each transfer output under the environment of FIG. The curve shown by the solid line represents the amount of residual toner when a recording sheet that has not been conditioned is used as the transfer object. The curve indicated by the dotted line represents the amount of residual toner when the toner pattern is directly transferred onto the transfer film on the surface of the transfer drum 40. Comparing the amount of residual toner generated for the transfer film with the amount of residual toner generated for unhumidified recording paper, there is a difference in the absolute value of the remaining toner, but the difference is almost constant regardless of the transfer output. It turns out to be.

FIG. 23 shows that each recording output is obtained when a recording sheet having a low resistance value after humidity control for 7 to 8 hours is used as an object to be transferred in an environment of 28 ° C. and 80% RH. Accordingly, the photosensitive drum 2 after being transferred onto the transfer target
6 is a graph showing the amount of toner remaining on the image No. 3; In the case of the recording paper after the humidity control, it is understood that not only the absolute value of the residual toner but also the difference greatly differs depending on the output as compared with the transfer film. Thus, for the transfer film and the recording paper,
By comparing the relationship between each transfer output and the residual toner, it can be determined whether or not the recording paper has been humidified and the resistance value has become low in a high humidity environment. Note that the relationship between the recording paper and the transfer film is a relationship that is established between a recording paper that absorbs moisture and a film such as an OHP sheet that absorbs little moisture.

FIG. 24 shows a case where the execution key of the transfer output adjustment processing provided on the operation panel 50 is pressed,
14 is a flowchart of a control process executed by the control unit 14. First, a plurality of toner patterns of the same density formed on the photoreceptor are transferred while changing the transfer output stepwise to form toner patterns P1 to P17 shown in FIG. 9 on recording paper (step S80). After transferring the patterns P1 to P17 onto the recording paper, the amount of toner remaining on the photosensitive drum 23 is measured (step S81). Subsequently, the toner patterns P1 to P17 are formed on the transfer film (Step S82), and the amount of toner remaining on the photosensitive drum 23 after the transfer of the toner patterns P1 to P17 onto the transfer film is measured (Step S83). .

Then, the residual toner density information at the time of transfer to the transfer film sent to the CPU 14 is compared with the residual toner density information at the time of transfer to the recording paper (step S84). Here, the interval of the difference is almost constant irrespective of the transfer output, but when the density rise at the time of high output is large, for example, when the difference between the minimum density and the density at 700 μA is both 0.5 mg / cm ² or more. In some cases, it is determined that the resistance value of the recording sheet has not decreased and is appropriate but the toner charge amount has decreased significantly (YES in step S85, NO in step S86), and the output of the pre-transfer charger 108 is increased. Raise the charge amount of the toner before transfer (Step S
87). Thereby, sufficient transfer efficiency can be obtained without modifying the control table.

Also, as a result of comparing the density information at the time of transfer onto the transfer film and the density information at the time of transfer onto the recording paper, if the interval of the difference is largely different depending on the output, and the density rise at the time of high output is large, for example, The difference between the minimum density and the density at 700 μA is both 0.5 mg / cm ² or more, and the amount of the residual toner when the transfer medium is a recording paper and the amount of the residual toner when the transfer film is a transfer film. If the difference is 0.2 mg / cm ² or more, it is determined that both the resistance value of the recording paper and the toner charge amount have decreased (YE in steps S85 and S86).
S), the following steps S88 to S95 are executed. (Step S88). First, the pre-transfer charger 10
8 (step S88), the toner pattern is formed again with the toner charge amount raised (step S89), and the density of the toner patterns P1 to P17 remaining without being transferred onto the photosensitive drum 23. The sensor 112
(Step S90). The transfer output of the toner pattern that minimizes the residual toner is specified from the detection result (step S91). Next, the transfer output is corrected in consideration of the change in the transfer characteristics due to the humidity control of the recording paper. More specifically, when the recording paper after humidity adjustment to the residual toner concentration of the toner patterns P3 and P15 detected when the transfer output is 100 μA and 700 μA and the absolute humidity detected by the environment sensor 15 is used. The difference is obtained by comparing with the residual toner concentration to be obtained (step S9).
2). Then, based on the difference between the obtained residual toner densities, the shift amount is specified by Tables 2 and 3, and a value shifted by the specified shift amount from the transfer output value at which the residual toner density becomes minimum is set as the transfer output. (Step S93).
As described above, by correcting the transfer output in consideration of the change in the transfer characteristics due to the humidity control of the recording paper, it is possible to suppress a large change in the transfer output due to the humidity control of the recording paper.

Thereafter, the transfer output specified by the control table shown in Table 1 corresponding to the absolute humidity detected by the environment sensor 15 is compared with the transfer output set in step S93. YE in S94
S), the relationship between the absolute humidity classification and the transfer output in the control table is shifted so that the transfer output set in step S93 is selected (step S95). The shifted control table is stored in the RAM 13 and is used to control the transfer output during normal copy execution until the transfer output adjustment processing is performed next. If the processing for the four colors has not been completed (NO in step S96), the process proceeds to step S96.
A series of control processing of 80 to S95 is repeatedly executed by the number of magenta, yellow, and black toner developing devices in addition to cyan. After the end of the control process for four colors (step S9
(YES at 6), ends the process. Also, the paper cassette 3
A film such as an OHP sheet that is not easily absorbed by moisture is set in any one of the sheets 1 to 33, and in step S82, paper is fed from a paper cassette in which the film is set, and a toner pattern is formed on the film. It may be transferred.

In the sixth embodiment, based on the toner density remaining on the photosensitive drum 23 after the transfer and the resistance value of the recording paper, it is determined whether the cause of the decrease in the transfer efficiency is due to the deterioration of the toner or the recording paper. Although it is determined whether the change is due to a decrease in the resistance value, in addition to the transfer efficiency of each toner pattern, only one of the resistance value of the recording paper and the charge amount of the toner before transfer is detected, and based on the detected value. Alternatively, the transfer conditions may be controlled. For example, when the transfer efficiency and the resistance value of the recording paper are each equal to or less than the reference value, it is determined that the cause of the reduction in the transfer efficiency is the reduction in the resistance value of the recording paper in a high humidity environment, and the transfer charger is determined. Only 38 outputs are controlled. If the transfer efficiency and the charge amount of the pre-transfer toner are respectively equal to or less than the reference values, it is determined that the decrease in the transfer efficiency is due to the deterioration of the toner.
08 is controlled only. In the copying machines of the first to sixth embodiments, the transfer charger 38 is used, but a contact-type transfer brush or a transfer roller may be used. Further, instead of the transfer drum 40, a transfer belt may be used.

(7) Seventh Embodiment In the copying machine of the above-described embodiments, the corona charger 38 is used as a transfer charge applying means for transferring a toner pattern by controlling the constant current. In the case of using a corona charger, the electric charge generated from the wire flows into the back surface of the transfer film and the stabilizer, but the current flowing into each changes when the impedance of the flow destination changes. For example, when the resistance value of the paper becomes low due to humidity control at high humidity, the impedance on the back side of the transfer film becomes smaller than that on the stabilizer side, so the current value flowing into the back side of the transfer film increases. The electric field for transferring the toner from the photoreceptor is basically determined by the current flowing from the transfer electric field applying member to the photoreceptor, in other words, the current flowing on the back side of the transfer film. The current to the back side of the transfer film changes under the influence of the condition, and the transfer electric field is unstable.

Next, a digital full-color copying machine according to a seventh embodiment of the present invention will be described. In the present embodiment, the transfer output is controlled by a constant current using a contact-type transfer charge applying means (for example, a transfer brush). As a result, the current to the transfer film side can always be kept constant, so that the influence of the humidity control of the paper can be suppressed. In addition, it controls development output. In the present embodiment, the transfer output is determined only by detecting the toner pattern on the transfer film. FIG. 25 shows a more detailed configuration around the photosensitive drum and the transfer drum of the copying machine according to the seventh embodiment. Instead of the transfer charger 38 and the pressing member 39 of the first embodiment shown in FIGS.
8 'is used. Further, a high-voltage power supply 127-1 for the developing device
30 applies a developing bias voltage on which an AC component is superimposed to the developing sleeves of the developing devices 27 to 30.

FIG. 26 shows a case where a plurality of toner patterns having the same density are formed on a photoreceptor, and these are respectively transferred onto a transfer film and a conditioned paper (at 28 ° C., 80% RH for 8 hours). Shows the transition of the concentration of. From the figure, it can be seen that the outputs at which the maximum density is obtained for each of the transfer film and the paper overlap over a wide range.
Therefore, if the contact-type charge applying means is used under constant current control, it is possible to determine a transfer output that is almost suitable only by detecting the transfer pattern without detecting the toner pattern (test pattern) on the paper. can do. However, when transferring to high-temperature, high-humidity or low-temperature, low-humidity paper that has been conditioned for a long time, the output range at which the maximum density is obtained becomes narrower because the area where the transfer film and the paper overlap is narrower.
The accuracy of output control is slightly reduced.

Next, control of the developing conditions will be described. As shown in FIG. 26, when the contact type charge applying means is used under constant current control and the relationship between the transfer output and the density is obtained,
The change in the density of the toner pattern transferred onto the transfer film is substantially determined by the toner charge amount before the transfer. FIG.
The transition of the density when a plurality of toner patterns having the same density are formed on a photoreceptor under an environment of 0 ° C. and 85% RH and then transferred onto a transfer film is shown. At the initial stage, the transfer output at which the maximum density can be obtained is obtained with a certain width, but after the end of 20,000 sheets, the transfer output at which the maximum density can be obtained is almost nonexistent. This is largely due to a decrease in the toner charge amount before transfer. The toner charge amount before transfer is
It changes greatly depending on the environment and durability, but also changes depending on the AC component when an AC voltage is superimposed on the developing bias voltage of the developing device. By utilizing this fact, when there is almost no transfer output width at which the maximum density can be obtained due to durability, the AC component of the developing bias voltage is controlled so that a wide transfer output width can be obtained. FIG. 28 shows data obtained by measuring the transfer output characteristic while varying the AC component of the developing bias voltage after the end of 20,000 sheets. The figure shows the case where the peak-to-peak voltage V _pp of the AC component is 1 kV and 2 kV. 1k
In the case of V, the width of the transfer output at which the maximum density can be obtained is obtained to some extent. Therefore, even when the control accuracy of the transfer efficiency drops due to environmental, by applying a developing bias voltage of the appropriate V _pp, the width of the transfer current maximum density can be obtained is widened.

Next, the process of adjusting the transfer output and the developing bias voltage in the present embodiment will be described. When the execution key of the transfer output adjustment process provided on the operation panel 50 is pressed, a plurality of toner patterns having the same density are formed on the photosensitive drum 23 in order to stabilize the image density (S10).
1). Next, the transfer output is changed for each toner pattern and transferred onto the transfer film, and the density of the toner pattern on the transfer film (toner adhesion amount) is used as data representing the transfer efficiency.
Is detected (S102). Then, the transfer output at which the maximum toner density is obtained is specified (S103). Since the toner density to be obtained after the humidity control has been obtained in advance, the difference between the toner density and the transfer output specified in S103 is obtained (S104). If there is a difference, the shift amount specified based on this difference is determined. The transfer output is shifted only by
5). In this way, the transition of the transfer efficiency of each toner pattern transferred onto the transfer film is monitored, the characteristics of the toner are grasped, and the transfer conditions are controlled as necessary, so that the transfer efficiency due to the environmental change is reduced. Changes can be suppressed. Further, the transfer output of the maximum toner density is compared with the transfer output obtained from the control table of the relationship between the transfer output and the absolute humidity as shown in Table 1 (S106). The control table is corrected by shifting the relationship between the temperature division and the transfer output by a predetermined shift amount (S
107). Further, when it is determined that the toner charge amount before transfer has decreased (in an environment such as high temperature, high humidity or low temperature, low humidity, or when the photoconductor has been used for a long time) (S1).
08), the developing bias voltage (for example, V _pp ) is changed by controlling the high voltage power supply for the developing device (S109). The amount of change in the developing bias voltage is determined based on a relationship obtained in advance. The processing of S101 to S109 described above is repeated until the processing for four colors of cyan, magenta, yellow, and black is completed (S110).

[0051]

According to the first image forming apparatus of the present invention, the transition of the transfer efficiency of each toner pattern transferred onto the recording paper by the transfer means is monitored to grasp the state of the recording paper and the toner. , The transfer condition can be changed based on the change of the transfer efficiency.

Further, in the second image forming apparatus, the transition of the transfer efficiency of each toner pattern transferred onto the recording paper by the transfer means is monitored, and further, the resistance value of the recording paper and the toner pattern formed on the photoreceptor are monitored. By detecting one or both of the charge amounts immediately before the transfer of the toner pattern, the state of the recording paper and the toner can be grasped, the transfer conditions can be changed as necessary, and the transfer efficiency changes due to environmental changes. Can be suppressed.

In the third image forming apparatus, the transfer efficiency of each toner pattern transferred onto the recording paper by the transfer means is monitored and compared with the transfer efficiency on the film, so that the recording paper and the toner are transferred. Of the transfer efficiency can be controlled, and the transfer conditions can be controlled as necessary, thereby suppressing a change in transfer efficiency due to a change in environment.

In the fourth image forming apparatus of the present invention, the state of the toner is grasped by monitoring the transition of the transfer efficiency of each toner pattern transferred onto the transfer film by the transfer means, and the transfer is performed based on this. By changing the conditions, it is possible to suppress a change in transfer efficiency due to a change in environment.

In the fifth image forming apparatus according to the present invention, the transition of the transfer efficiency of each toner pattern transferred onto the transfer film by the transfer means is monitored to grasp the state of the toner, and the developing is performed based on the state. By changing the conditions, it is possible to suppress a change in transfer efficiency due to a change in environment and durability.

[Brief description of the drawings]

FIG. 1 is a diagram showing a transfer efficiency with respect to each transfer output.

FIG. 2 is a cross-sectional view of the digital full-color copying machine according to the first embodiment.

FIG. 3 is a graph showing a relationship between a volume resistance value (Ω · cm) of recording paper and an absolute humidity (g / m ³ ).

FIG. 4 shows a toner charge amount (μC / g) before transfer.
4 is a graph showing a relationship between the absolute humidity and g / m ³ .

FIG. 5 shows that each of the devices is 7 to
6 is a graph illustrating a change in toner density when an image is output by changing a transfer output after being left for 8 hours to adjust to an environment.

FIG. 6 is a diagram illustrating a detailed configuration around a photosensitive drum and a transfer drum of the copying machine according to the first embodiment.

FIG. 7 is a flowchart of a transfer output adjustment process.

FIG. 8 is a graph showing a transfer output from the leading edge to the trailing edge of a sheet when forming a toner pattern.

FIG. 9 is a diagram illustrating toner patterns P1 to P17.

FIG. 10 is a graph showing the transfer efficiency when the recording paper before and after the humidity control is used when the absolute humidity detected by the environment sensor is lower than that of the recording paper.

FIG. 11 is a graph showing the transfer efficiency when the recording paper before and after the humidity control is used when the absolute humidity detected by the environment sensor is higher than that of the recording paper.

FIG. 12 is a diagram illustrating a more detailed configuration around a photosensitive drum and a transfer drum of a copying machine according to a second embodiment.

FIG. 13 is a flowchart of a transfer output adjustment process.

FIG. 14 is a diagram illustrating a more detailed configuration around a photosensitive drum and a transfer drum of a copying machine according to a third embodiment.

FIG. 15 shows that each of the devices is 7 under three environments.
10 is a graph showing a change in the residual toner concentration when the transfer output is changed after being left for 〜8 hours to adjust to the environment.

FIG. 16 is a flowchart of a transfer output adjustment process.

FIG. 17 is a diagram illustrating a more detailed configuration around a photosensitive drum and a transfer drum of a copying machine according to a fourth embodiment.

FIG. 18 is a flowchart of a transfer output adjustment process.

FIG. 19 is a graph showing the density of toner transferred onto recording paper and a transfer film before humidity control when the transfer output is changed.

FIG. 20 is a diagram illustrating the density of toner transferred onto a recording sheet and a transfer film after humidity control when the transfer output is changed.

FIG. 21 is a flowchart of a transfer output adjustment process.

FIG. 22 is a diagram illustrating a toner density remaining on a photosensitive member after being transferred onto a recording paper and a transfer film before humidity control when a transfer output is changed.

FIG. 23 is a diagram illustrating a toner density remaining on a photosensitive member after being transferred onto a recording paper and a transfer film after humidity control when a transfer output is changed.

FIG. 24 is a flowchart of a transfer output adjustment process.

FIG. 25 is a diagram illustrating a more detailed configuration around a photosensitive drum and a transfer drum of a copying machine according to a seventh embodiment.

FIG. 26 is a graph showing the density of toner transferred onto a recording sheet and a transfer film before humidity control when the transfer output is changed using a transfer brush.

FIG. 27 is a graph showing the density of toner transferred onto a transfer film at the initial stage and after the end of 20,000 sheets when the transfer output is changed using a transfer brush.

FIG. 28 is a graph showing the density of toner transferred onto a transfer film when the transfer output is changed using a transfer brush and the AC developing bias voltage is changed.

FIG. 29 is a flowchart of a transfer output adjustment process.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 13 ... RAM 14 ... CPU 15 ... Environment sensor 16 ... ROM 20 ... Print head part 23 ... Photoconductor drum 27-30 ... Toner developing device 40 ... Transfer drum 81 ... Voltage application part 82 ... Resistance value measurement part 108 ... Pre-transfer charger 109: adhesion amount detection sensor 110: potential sensor 112: residual toner concentration detection sensor 213: toner concentration detection unit

Claims (5)

[Claims] An image forming apparatus employing an electrophotographic method, wherein a toner pattern forming means for forming a plurality of toner patterns of the same density on a photoreceptor; and a transfer output which is continuously changed for each toner pattern. Transfer means for transferring the toner pattern onto the recording paper; transfer efficiency detection means for detecting the transfer efficiency of each toner pattern transferred onto the recording paper; and transfer efficiency of each toner pattern detected by the transfer efficiency detection means. An image forming apparatus comprising a control unit for controlling a transfer condition. 2. An image forming apparatus employing an electrophotographic method, comprising: a toner pattern forming means for forming a plurality of toner patterns of the same density on a photoreceptor; and a transfer output continuously changing for each toner pattern. Transfer means for transferring the toner pattern onto the recording paper; transfer efficiency detecting means for detecting the transfer efficiency of each toner pattern transferred onto the recording paper; resistance value of the recording paper; and transfer of the toner pattern formed on the recording paper. A characteristic amount detecting means for detecting at least one of the charge amounts immediately before transfer; a transfer efficiency detected by the transfer efficiency detecting means; and a resistance value and / or a charge amount detected by the characteristic amount detecting means. An image forming apparatus, comprising: a control unit that controls a transfer condition based on the control information. 3. An image forming apparatus employing an electrophotographic method, wherein: a toner pattern forming means for forming a plurality of toner patterns of the same density on a photoreceptor; Transfer means for transferring the toner pattern onto the recording paper and film, transfer efficiency detection means for detecting the transfer efficiency of each toner pattern transferred on the recording paper and film, and An image forming apparatus comprising: a control unit that controls a transfer condition. 4. An image forming apparatus employing an electrophotographic method, wherein: a toner pattern forming means for forming a plurality of toner patterns having the same density on a photoreceptor; Transfer means for transferring the toner pattern onto the transfer film, transfer efficiency detection means for detecting the transfer efficiency of each toner pattern transferred on the transfer film, and transfer efficiency of each toner pattern detected by the transfer efficiency detection means. An image forming apparatus comprising: a control unit that controls a transfer condition based on the control information. 5. An image forming apparatus employing an electrophotographic method, wherein a toner pattern forming means for forming a plurality of toner patterns of the same density on a photoreceptor, and a transfer output is continuously changed for each toner pattern. Transfer means for transferring the toner pattern onto the transfer film, transfer efficiency detection means for detecting the transfer efficiency of each toner pattern transferred on the transfer film, and transfer efficiency of each toner pattern detected by the transfer efficiency detection means. An image forming apparatus comprising: control means for controlling development conditions based on the control information.