JP3369377B2 - Image forming device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for charging a photoconductor with a contact charging member, and more particularly, to an appropriate value for a charging voltage applied to the contact charging member according to the wetness of the contact charging member. Regarding the technology to adjust.

[0002]

2. Description of the Related Art In a conventional electrophotographic image forming apparatus represented by the Carlson process, a corona discharge method which is a non-contact method has been used in order to uniformly charge a photosensitive member. A large amount of ozone was generated because the photoconductor was ionized and charged. This ozone is generated more often when a negative discharge is performed, but in addition to the fact that the photoreceptor has become an organic photoreceptor (OPC) for negative charging in recent years and the environmental standard for the generated gas has become strict, It is a serious problem.

On the other hand, the contact charging method in which the charging member is brought into contact with the OPC for charging has the advantages that the voltage applied to the charging member is small and the ozone generation is very small. The contact charging member (hereinafter, charging roller) has been commercialized. This charging roller is provided with a shaft having rigidity at the center for supporting both ends by bearings, and the outer peripheral surface needs to contact the OPC uniformly, so that elasticity at the time of contact is required. The shaft is also made of metal due to the need to apply a voltage across the roller. At this time, if the conductive rubber portion that surrounds the shaft is thin, the elasticity is poor, and if it is a curved surface of the OPC, a gap is generated, which causes uneven potential. Again O
If the foreign matter attached to the PC is hard, the foreign matter may be applied to the OPC in the contact area with the charging roller and the OPC may be damaged if it is not elastic.

For the above reason, the conductive rubber portion of the charging roller is required to have a certain thickness (1 mm or more experimentally). In addition, as the material, the functional group itself in the molecular constitution is conductive (for example, epichlorohydrin rubber),
There are rubbers in which conductive particles are dispersed and mixed (for example, EPDM rubber in which carbon particles are dispersed, urethane rubber in which zinc particles are dispersed) and the like. In the latter case, in which conductive particles are dispersed and blended in rubber, there is a large potential unevenness, and there is a possibility that a local low resistance portion may occur due to defective blending of the conductive particles. OPC may be damaged by leakage at the low resistance portion.
On the other hand, the former, that is, the one having a conductive portion in the functional group, has a small electric potential unevenness because it has uniform electric resistance and does not cause a leak, but on the other hand, it has a large humidity dependency and the OPC potential ( The problem is a decrease in the charged area.

In order to improve this, there is a technique of detecting the temperature of the contact charging member and controlling the voltage application condition based on the value judged against the preset voltage application condition.
No. 186,381.

[0006]

However, the electrical conductivity of the charging roller is different in environments where the humidity conditions are different even at the same temperature. In this case, it is impossible to correct the applied voltage by temperature detection, especially when the water content is small and the electrical conductivity is small in a low temperature and low humidity environment, there is a possibility that the charging potential is too small due to the small applied voltage. .

On the other hand, contact with the OPC causes contamination of the surface of the charging roller, and an increase in electric resistance in the adhesion area due to toner adhesion causes uneven electric potential over time, which shortens the life of the roller.

An object of the present invention is to prevent the surface of the contact charging member from being contaminated and to make the charging potential uniform (prevent potential unevenness) even under the condition that the contact charging member absorbs different water due to environmental changes. And

[0009]

As a means for preventing roller contamination, it is possible to solve the problem by using as the surface layer a material having a good releasability from the adherent such as toner. Nylon is known as a material having a small surface friction resistance and good releasability. By the way, when the conductive rubber layer is coated with a nylon resin in a thickness of about 10 μm, the humidity dependency is large, and there is a problem that the charging potential of the photoconductor is lowered under low humidity conditions. In particular, the humidity dependency of the roller coated with nylon on a material having a conductive tube functional group in its molecular structure is greatly increased, and image unevenness due to an abnormal decrease in the potential under low humidity conditions (white clear in the positive / positive system, negative / positive system) , Black stripes and black bands) are likely to occur.

Therefore, the image forming apparatus of the present invention is a contact charging member which is composed of two or more different members, has at least a conductive rubber layer and a surface resistance layer made of nylon resin, and contacts the photosensitive member to charge the photosensitive member. In addition, a light emitter that irradiates the contact charging member with light of different wavelengths and a light receiver that detects the light reflected by the contact charging member; a charging power source that applies a voltage designated by the control means to the contact charging member; Corresponding to the water content, memory means storing voltage data to be applied to the contact charging member in order to charge the photoreceptor substantially constant at the water content; relative relationship between different light levels detected by the light receiver And a control means for detecting the water content of the contact charging member, reading out voltage data corresponding to the detected water content from the memory means, and designating application of a voltage corresponding to the voltage data to the charging power source. That.

According to this, since the surface resistance layer of the contact charging member is made of nylon resin and has a good releasability from the deposit, the contamination of the surface of the contact charging member is reduced. On the other hand, although the contact charging member has a high humidity dependency, the control means detects the water content of the contact charging member from the detection signal of the water content measuring device including the light emitter and the light receiver, and determines the charging voltage corresponding to the water content. Since the voltage is applied to the contact charging member, the charging voltage is adjusted according to the humidity, and thus a substantially constant charging potential can be uniformly formed on the photoconductor despite the fluctuation of the water content, which causes image unevenness. Does not happen.

Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.

[0013]

DETAILED DESCRIPTION OF THE INVENTION

[0014]

FIG. 1 shows a first embodiment of the image forming apparatus of the present invention, FIG. 2 shows the charging roller 102 shown in FIG. 1 in an enlarged manner, and FIG. 3 shows the image shown in FIG. The combinational relationship between the controller C that controls the operation of the forming mechanism, the humidity detection sensor D, and the charging power source 207 is shown. First, referring to FIG. 1, in FIG. 1, 101 is a photosensitive drum (charge carrier) on which an electrostatic latent image is formed, and 102 is a photosensitive drum 101.
A charging roller (contact charging member) for charging by contacting with
Reference numeral 103 is an exposure device that projects image light onto the photosensitive drum 101, 104 is a developing device that attaches a toner to the electrostatic latent image on the photosensitive drum 101, and 105 is a recording medium conveyed from a paper feed unit (not shown). The image on the photoconductor drum 101 (toner)
Image)), a registration roller that conveys the image at a timing,
Reference numeral 06 is a transfer charger for transferring the toner image on the photosensitive drum 101 to recording paper, and 107 is the photosensitive drum 101.
Separation charger for separating recording paper stuck to the surface, 10
Reference numeral 8 is a cleaning device for removing and recovering the residual toner on the surface of the photosensitive drum 101, and 109 is a quenching lamp (static eliminating device) for removing the residual potential of the photosensitive drum 101 and restoring the initial level. Note that, in FIG. 1, other functional units normally required in the electrophotographic process are omitted.

A basic image forming operation in the electrophotographic apparatus configured as described above will be described. The surface of the photosensitive drum 101 is uniformly charged to a high potential by supplying a DC voltage to the charging roller 102 in contact with the photosensitive drum 101 from a charging power source 207. Immediately after that, when the exposure device 103 projects image light onto the surface of the photosensitive drum 101, the potential of the portion irradiated with the image light decreases. Since the image light has a light amount distribution corresponding to black / white of the image, the potential distribution corresponding to the recorded image, that is, an electrostatic latent image is formed on the surface of the photosensitive drum 101 by the irradiation of the image light. When the portion on which the electrostatic latent image is formed passes through the developing device 104, the toner adheres according to the level of the potential,
A toner image is formed by visualizing the electrostatic latent image. Toner
The registration roller is applied to the part where the image is formed at a predetermined timing.
The recording paper is conveyed by the laser 105 and overlaps the toner image. After the toner image is transferred to the recording paper by the transfer charger 106, the recording paper is separated from the photosensitive drum 101 by the separation charger 107. The separated recording paper is conveyed through the conveyance path. Then, after being thermally fixed by a fixing unit (not shown), it is discharged to the outside of the machine.

After the transfer process is completed, the surface of the photosensitive drum 101 is cleaned by the cleaning device 108, and the residual charge is erased by the quenching lamp 109 to prepare for the next image forming process. In addition,
In the above electrophotographic apparatus, since the charging roller 102 is used instead of the usual corona discharge type charging charger, the ozone generation thereof is 40% as compared with the charging charger.
~ 60% less. If it is desired to further reduce the generation of ozone gas, the transfer charger 106
A transfer belt or a transfer roller may be used instead of.

The controller C controls the operation (on / off) timing of various elements for the above-mentioned image forming processing.

Next, the construction of the charging roller 102 and its charging system will be described with reference to FIG. In the figure, 201 is a cored bar, which is made of a conductive material such as SUS (stainless steel) material, steel + plated material, and A1 (aluminum bar) material. The cored bar 201 is provided with a conductive rubber layer 202 and a surface layer 203. The conductive rubber layer 202 is
A medium resistance elastic body such as epichlorohydrin rubber having a wall thickness of about 1 to 4 mm, or a synthetic rubber such as silicon rubber, ethylene propylene rubber, nitrile rubber, norponene rubber is used, and conductive powder (for example, It is formed by a composition in which carbon black, zinc oxide, titanium oxide, metal powder, etc.) are mixed. Further, as these characteristics, the volume resistance is 10 ² Ω · cm or more and 10 ⁵ or more.
Ω · cm or less, preferably 10 ² Ω · cm or more and 10 ³ Ω ·
cm or less, rubber hardness (JIS-A) 20 to 90 degrees, preferably 35 to 50 degrees are common.

A surface layer 203 is formed on the outer peripheral surface of the conductive rubber layer 202 to have a layer thickness of 3 to 25 μm, preferably 4.5 to 12 μm.
It is made of the following materials. The material of the surface layer 203 is nylon (for example, Toray's trade name CM8000, C
M4000, trade name Daiamide T171 manufactured by Daicel)
To use. The volume resistance of the surface layer 203 is 10
⁵ to 10 ¹³ Ω · cm, preferably 10 ⁶ to 10 ¹² Ω · cm
Is good. In order to adjust to this electric resistance range, conductive particles such as carbon black may be dispersed and mixed in the surface layer. Further, it is desirable that the volume resistance from the conductive rubber layer 202 to the surface layer 203 has conductivity of about 10 ⁶ to 10 ¹² Ω · cm.

Both ends of the cored bar 201 are rotatably supported by bearings 204. The bearing 204 is urged by a spring 205 to move the charging roller 102 to the photosensitive drum 1
01 is brought into pressure contact with a predetermined pressure. The mechanism for pressing the charging roller 102 to the photosensitive drum 101 is not limited to this, and the photosensitive drum 101 is not limited to this.
Another mechanism may be used as long as the charging roller 102 is brought into contact with the charging roller 102 and the driving force of the photosensitive drum 101 causes the charging roller 102 to rotate together by friction with the charging roller 102. A power supply receptacle 206 is provided on one end surface of the charging roller 102 so as to be in contact therewith, and a power supply 20 for applying a voltage to the power supply receptacle 206.
7 is connected. Further, 210 is the charging roller 102.
It is a roller cleaning member for contacting with the roller to remove the deposits on the roller surface, and specifically, a pad member, emery paper, or the like is used.

In the above structure, the charging roller 102
Is supplied with voltage from the power supply 207 whose application timing is controlled by the control means (C: FIG. 3) to the cored bar 201 via the power supply receptacle 206. Due to this power supply, an electric current flows through the core metal 201, the conductive rubber 202, the surface layer 203, and the photosensitive drum 101, and the photosensitive drum 101 is charged. The power supply system is not particularly limited to this form as long as the current path as described above can be obtained. For example, the power source 207 may be connected to the spring 205 and the bearing 204 may be a conductive member.

FIG. 3 shows the detector D and the charging voltage control system. The moisture detector D includes two light emitters DeA and DeB.
And a light receiver Dr that receives the reflected light reflected from the charging roller surface layer 203 and generates an electric signal corresponding to the received light level, and is arranged in a non-contact manner facing the charging roller surface.

FIG. 5A shows the emission intensity distributions of the light emitters DeA and DeB and the light receiving sensitivity (spectral sensitivity) of the light receiver Dr.
Indicates. First light emitter DeA for irradiating the charging roller 102
The emission A of the second emission device DeB, which also irradiates the charging roller 102, has an intensity peak at a wavelength of 1.45 μm. The light emission A is used as a comparative wavelength, and for this purpose, the first light emitting device DeA may be another light emitting device having an intensity peak at a wavelength of 0.4 to 0.8 μm.

The reflected light from the charging roller surface layer 203 is
The light enters the light receiver Dr arranged at a position of 10 to 40 degrees on the normal line of the light emitting portion. The photoelectric conversion sensitivity of the light receiver Dr is
The reflected light having a wavelength of 0.7 to 1.7 μm and incident on the light receiver Dr is subjected to signal processing (level calibration) by the amplifier circuit G and is given to the controller C. The controller C is A / D converted and read.

The comparison wavelength band (emission A) is the charging roller 102.
There is almost no sensitivity (change in reflected light intensity) with respect to the water content of, but 1.45 μm (emission B) has a large sensitivity as an absorption spectrum of water. That is, the charging roller 10
When the water content of 2 is large, water absorbs light having a wavelength of 1.45 μm, so that the comparison value A / B (reflected light intensity of emitted light A / reflected light intensity of emitted light B) becomes large. That is,
A / B corresponds to the amount of water on the surface of the charging roller 102. The relationship between the water content and A / B is shown in FIG. This Figure 5
The graph showing the relationship between the water content and A / B shown in (b) of
FIG. 3 is a diagram showing a correspondence relationship between a detection value and a voltage application value when the detection device of the present invention is mounted on an actually used image forming apparatus. That is, a voltage application value for keeping the charging potential of the photosensitive drum at a predetermined constant value and a moisture detection value are previously measured and graphed for charging rollers having different moisture contents (rates). Numerical tables equivalent to the graph are stored (stored) in the memory in the controller C as voltage application conditions. As can be seen from the graph, when the water content of the charging roller is high, the comparison value A
/ B is detected as a value larger than the above principle, and at that time, it is recognized that the electric conductivity of the charging roller is large, and the voltage application value is updated to a smaller value and output.

FIG. 5B shows A / B and charging roller 1.
No. 02 shows the relationship with the surface water content and the charging voltage to be applied to the charging roller 102 necessary to uniformly charge the photoconductor 101 to a predetermined potential (constant potential) at the water content. , A / B and moisture content are substantially proportional (linear)
Since there is a relation, A / B is applied to the charging roller 102 from the three relations of A / B, moisture content and voltage to be applied to the charging roller 102 shown in FIG. 5B. We asked for the relationship between the two, which should be the voltage. The relationship between the two is shown in FIG. Then, the charging roller 10 corresponding to each value of A / B
The voltage to be applied to 2 is stored in the internal memory of the controller C. That is, with A / B as the address, the A / B
The voltage data corresponding to is stored in the memory.

The controller C performs a lighting operation of the second light emitter DeB of the moisture detection device D when A / B calculation is necessary, and synchronizes with the signal instructing the device D to receive the light receiver D.
The photoelectric conversion signal of r (analog voltage calibrated by the amplifier G) is digitally converted, and it is checked whether the obtained data B substantially matches the set value, and the data B is set to a value larger than the set value. When it is shown, the gain of the amplifier G is decreased by one step, and when the data B shows a value smaller than the set value, the gain of the amplifier G is increased by one step. Then, the lighting operation of the second light emitter DeB is performed, and the photoelectric conversion signal of the light receiver Dr is digitally converted in synchronization with the signal instructing the device D. When the data B substantially matches the set value, the data B at that time is stored in the internal memory of the controller C, and the gain adjustment of the amplifier G is completed. Next, the first light emitter De
The lighting operation of A is performed, the photoelectric conversion signal of the light receiver Dr is digitally converted in synchronization with the signal instructing the detection device D, and the obtained data A is stored in the internal memory of the controller C. Controller C then calculates A / B and stores it in internal memory.

When the gain adjustment accuracy (gain resolution) of the amplifier G is high, A / the set value is calculated.
That is, A is used as A / B calculation data (1 / the above-mentioned set value is a constant or a coefficient).

FIG. 4 shows the control operation of the controller C. First, the outline of the control operation of the controller C will be described with reference to the main routine shown in FIG. 4A. When the power source of the device is turned on and a regular voltage is applied to the controller C, the controller C is controlled. Executes "initial setting processing" (steps 1 and 2). In the following, in parentheses, the word step is omitted and only the step number code is described. In the "initial setting process" (2), the controller C initializes the registers, counters, timers, etc. assigned to the internal memory or sets initial values, and the controller C controls the on / off timing. Output to (instruction signal)
Is set to off.

Next, the controller C is for "water content detection".
Execute (3A). The contents of this “water content detection” (3A) will be described later with reference to FIG. Then, the measurement of the elapsed time Tm from the end of one water content detection is started (3B).

Next, the opening / closing of a document pressure plate (not shown) is checked (4). When the document pressure plate is at the document pressing position, "document size detection" (5) is executed to input the image forming start (start). -Toggle SW on). While waiting for the input of the image forming start, "moisture amount detection" is performed at a predetermined cycle (Ts).
Repeat (3A). That is, the measurement time Tm is compared with the set value Ts (12B), and "water content detection" (3A) is not executed while Tm <Ts, but when Tm≥Ts, "water content detection" ( 3A) is executed and the measurement of the elapsed time Tm is newly started (3B).

When the image forming start is input, the required paper (recording paper) size corresponding to the document size, the recording size designation and / or the image forming magnification designation is determined, and a cassette (Fig. (Not shown) is set as paper feed (7). Next, the controller C starts image formation (8), executes "charging potential control" (9), and forms a specified number of images (copies). When the specified number of images have been formed, the end cycle is set (11), the process returns to the image forming start input waiting state, and when the end cycle ends,
Therefore, the element that was turned on for the end cycle is turned off, and the image forming start input is waited for. While waiting for this start input, as described above, "water content detection" (3
Repeat A) in a predetermined cycle.

"Water content detection" with reference to FIG.
The contents of (3A) will be described. Here, controller C is
First, "gain adjustment of amplifier G" (21) is executed. That is, the second light emitter DeB of the water content detection device D is turned on, the output signal (voltage) of the amplifier G is converted into digital data and read, and if the read data B is larger than the set value, the amplifier G outputs. 1 when the gain is smaller by one step and smaller than the set value
The output signal of the amplifier G is digitally converted and read, and the gain is changed again by comparing with the set value. When the read data B becomes substantially equal to the set value, the data B is written in the register B. Control
Next, La C turns off the second light emitter DeB (22) and turns on the first light emitter DeA (23), digitally converts the output signal of the amplifier G, and reads the read signal. Data A is written into register A (24). And the first light emitter DeA
Is turned off (25), and data B and A of registers B and A are turned off.
The ratio A / B of the values represented by is calculated and written in the register A / B (26).

The contents of the "charge potential control" (9) will be described with reference to FIG. Controller C here
Reads the data A / B of the register A / B (3
1), it is checked whether it is within the set range (hatched area in (c) of FIG. 5, that is, 5.53 / 100 or more and 5.70 / 100 or less) (32).

If it is within the setting range, the previous value register Ap
It is checked whether the difference between the data Ap / Bp of / Bp and the data A / B is less than a predetermined value, and if it is less than the predetermined value, the data A / B is set to the previous value register Ap / Write to Bp, and
A table (controller C) in which the charging roller applied voltage shown in FIG. 5C is stored using the data A / B as an address.
The charging roller applied voltage data is read out from one area of the internal ROM of the device, that is, the charging voltage data V corresponding to A / B.
Read C and write it in the charging voltage register VC,
The data VC is converted into an analog voltage (charging voltage instruction signal) and supplied to the charging power source 207. The charging power source 207 supplies a charging voltage substantially proportional to the analog voltage to the charging roller 10.
2 (33, 34). Previous value register Ap / Bp
When it is checked whether the difference between the data Ap / Bp and the data A / B is less than the predetermined value, if the difference is more than the predetermined value, there is a high possibility that the water content detection error occurs. VC
Is read out, converted into an analog voltage (charging voltage instruction signal), and given to the charging power source 207 (33, 3).
5). That is, A / B calculated based on the latest water content detection is ignored, and the previously output charging voltage is also output this time.

By the control operation of the controller C described above, while waiting for the input of the image forming start, that is, the timing when the image forming is not performed, that is, the exposure apparatus 1
03 does not project the image light and the static elimination device 109 does not irradiate the static elimination light in the cycle Ts.

The surface layer 203 nylon used in the above examples has the following properties: Friction resistance is low (foreign substances are easily displaced from the surface).
As a result, even if foreign matter such as toner or paper dust is attached due to contact with the photoconductor 101, it is easily removed (by re-contact with the photoconductor or contact with a cleaning member).

A hermetic photoreceptor piece is placed on the peripheral surface of the charging roller 102, a weight of 100 g is placed on the photoreceptor piece, and a thread attached to the photoreceptor piece pulls a thread in the axial direction of the roller. When the frictional resistance of the charging roller 102 is measured by the measuring method, it is an example of the present invention, that is, Daiamide T171, CM-4000.
Alternatively, the friction coefficient of the charging roller 102 having the surface layer 203 of CM-8000 (all layer thickness is 8 μm) was 0.1 to 0.4 in all cases. The friction coefficient of the surface of the roller having the resin layer (thickness 8 μm) in which Lumiflon resin, hydrin rubber and silica were mixed and distributed as the surface layer 203, which was measured as a comparative example, was 1.5 or more. It can be seen from this that the friction resistance of the charging roller coated with nylon resin is low.

2. Verification of electric potential uniformity (hygroscopicity of nylon and controllability by moisture detection method) As described above, nylon has high hygroscopicity and electrical conductivity greatly changes depending on ambient humidity conditions. The potential drop is marked. There 2
A photoreceptor 101 using a charging roller 102 having Dyamid T171 as a surface layer 203 by changing the humidity level in an environment of 3 ° C.
An experiment was conducted to investigate the charging potential of the. The experimental results are shown in FIG. The charging potential of the photosensitive member 101 with the applied voltage of the charging roller 102 being constant has a potential unevenness of 60 V from low humidity to high humidity, whereas the moisture amount detection / charging voltage of the embodiment of the present invention described above. When adjustment is performed, the charging potential unevenness is 1
It has reached 5 V, achieving the purpose of making the potential uniform. The potential target value when charging the photoconductor 101 to a negative potential was −880V. The potential unevenness of 15 V is estimated to be due to the humidity dependency of the epichlorohydrin rubber of the conductive rubber layer 202.

In the above experiment, the surface layer 203 was treated with diamide T1.
The results obtained by changing from 71 to CM-4000 and CM-8000 are shown in FIG. 7. By applying applied voltage correction ((c) of FIG. 5) corresponding to the water content of each roller, it is possible to control the charging potential to a substantially constant level regardless of humidity, as in the case of DAIAMID T171. In all cases, the target value of the charging potential is -800V, and CM-40
The applied voltage was corrected in the direction of increasing the potential of both 00 and CM-8000.

The results of the above experiment when the conductive rubber layer 202 is of epichlorohydrin rubber, that is, a type having a conductive functional group, are shown by white circles in FIG. In this case, even after the control of the water content detection / charging voltage adjustment described above, potential unevenness occurs due to a slight difference in humidity environment. As a method for eliminating this, a rubber material which does not affect humidity may be used for the conductive rubber layer, and as described above, it is preferable to use synthetic rubber in which conductive particles are dispersed and blended.

The effect of changing the conductive rubber layer to the conductive particle-dispersed type synthetic rubber was examined, and the potential unevenness was evaluated when the humidity condition was changed. The results are shown by black circles in FIG. From this, comparing the potentials after control of water content detection / charge voltage adjustment, the roller with conductive particle dispersion type conductive rubber layer (black circle) is better than the roller with rubber layer with conductive tube functional group (white circle). It can be said that it is excellent in terms of potential uniformity.

According to the above-described embodiments, the following effects can be obtained: (1) By using the surface layer 203 of nylon resin, the roller surface cleaning property is improved, and the water content detection / charging is performed. By performing the voltage adjustment control, it is possible to maintain the potential uniformity regardless of changes in the humidity environment. Further, since the water content detecting device D is configured to detect a plurality of light emission outputs by one light receiving section, a size and a detection speed which can be mounted on a charging system by a charging roller are realized.

(2) Since the moisture detector D applies the characteristic of the absorption spectrum wavelength of water, the moisture amount can be detected with high accuracy and reliability, and the amount of moisture on the surface of the charging roller can be measured in a non-contact manner. Directly detect. As a result, damage to the roller surface, such as that caused by a contact-type detection device, or a correction failure due to a difference between the atmosphere and the amount of water in the roller when controlling the charging voltage by detecting atmospheric moisture in the ambient environment with a humidity sensor, etc. Resolve.

(3) The water content of the charging roller 102 is executed at a predetermined cycle Ts during standby, when the image is formed, and when the set number of copies have been completed and the cycle Ts has elapsed. Since the charging voltage is corrected in accordance with the detected water content, the photoconductor 101 is charged to the optimum charging potential even if the water content of the charging roller changes.

(4) In one embodiment, since the conductive rubber layer 202 is made of conductive particle-dispersed type synthetic rubber, the conductive rubber layer itself has a small change in electric conductivity due to a humidity environment.
The potential uniformity, which is the effect of (1), is further improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing an outline of an image forming mechanism according to an embodiment of the present invention.

FIG. 2 is an enlarged front view of the charging roller 102 shown in FIG. 1, with a part cut away.

FIG. 3 is a side view showing the configuration of the moisture detector D shown in FIG.

4 is a flowchart showing the control operation of the controller C shown in FIG. 3, in which (a) shows an outline of control,
(B) shows the content of "water content detection" (3A) of (a), (c) shows the content of "charge potential control" (9) of (a).

5A is a graph showing the spectral sensitivity of the light receiver and the light emitter of the moisture detector D shown in FIG. 1, and FIG. 5B is a level ratio A / B based on the detection value of the moisture detector D. , The moisture content of the charging roller 102 and the charging roller corresponding thereto.
3 is a graph showing the relationship of the charging voltage to be applied to the roller 102, and FIG. 6C is a level ratio A / B based on the detection value of the moisture detector D and the charging to be applied to the charging roller 102 corresponding to it. It is a graph which shows the relationship of voltage.

FIG. 6 is a graph showing a charging potential of a photoconductor by a charging roller according to an exemplary embodiment of the present invention, in which a horizontal axis represents a moisture detecting device D.
Indicates the humidity measured in. The black circle indicates moisture detection /
The results of carrying out the charging voltage adjustment are shown, and the white circles show the results without this adjustment.

FIG. 7 is a graph showing a charging potential of a photoconductor by a charging roller according to another embodiment of the present invention, in which the horizontal axis represents the humidity measured by the moisture detector D. The black mark shows the result of moisture detection / charging voltage adjustment according to the present invention, and the white mark shows the result without this adjustment.

FIG. 8 is a graph showing the charging potential of the photoconductor by two types of charging rollers having different materials of the conductive rubber layer 202 according to the present invention, and the horizontal axis shows the humidity measured by the moisture detector D.
Both are the results of moisture detection / charging voltage adjustment.

[Explanation of symbols] 101: Photosensitive drum 102: Charging roller 103: Exposure device 104: Developing device 105: Registration roller 106: Transfer charger 107: Separation charger 108: Cleaning device 109: Quenching lamp 201: Core 202: Conductivity Rubber layer 203: Surface layer 204: Bearing 205: Spring 206: Power supply receptacle 207: Power supply 210: Roller cleaning member

Continuation of front page (56) Reference JP-A-4-316064 (JP, A) JP-A-5-307315 (JP, A) JP-A-6-348095 (JP, A) JP-A-5-46001 (JP , A) JP 6-288906 (JP, A) JP 3-115838 (JP, A) JP 6-34531 (JP, A) JP 9-62062 (JP, A) JP 9-114200 (JP, A) Japanese Patent Laid-Open No. 7-72688 (JP, A) Japanese Patent Laid-Open No. 5-27550 (JP, A) Actually developed 7-18252 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/02 G03G 15/16 103

Claims (4)

(57) [Claims] 1. A photoconductor; comprising two or more different members,
A contact charging member that has at least a conductive rubber layer and a surface resistance layer made of nylon resin, and that contacts the photoconductor to charge the photoconductor; an exposure unit that projects image light onto the charged surface of the photoconductor; Developing means for developing the electrostatic latent image formed by the projection of the image light; transfer means for transferring the visible image formed by the development of the photoconductor onto a recording medium; light having different wavelengths on the contact charging member. A light-emitting device for irradiating the light and a light-receiving device for detecting light reflected by the contact charging member;
A charging power source for applying a voltage designated by the control means to the contact charging member; should be applied to the contact charging member in order to charge the photoconductor at a substantially constant amount of water corresponding to the amount of water of the contact charging member. Memory means for storing voltage data; the water content of the contact charging member is detected from the relative relationship of the different light levels detected by the light receiver, and the voltage data corresponding to the detected water content is stored in the memory means. An image forming apparatus comprising: a control unit that reads out from the charging power source and designates application of a voltage corresponding to the voltage data to the charging power source. 2. The image forming apparatus according to claim 1, wherein the conductive rubber is rubber in which conductive particles are dispersed. 3. The light emitter has an intensity peak at a wavelength of substantially 0.8 μm.
The first light emitter that emits a certain amount of light and a wavelength of substantially 1.
2. A second light emitter for radiating light having an intensity peak at 45 [mu] m, wherein the light receiver is one photoelectric converter having photoelectric conversion sensitivity at wavelengths 0.8 [mu] m and 1.45 [mu] m. 2. The image forming apparatus according to 2. 4. The control means executes the detection every time a set time elapses, and when the photosensitive member is charged next time, the voltage data is read from the memory means and the charging power source responds to the voltage data. The image forming apparatus according to claim 1, wherein the application of the voltage is designated.