JPH0619281A - Image forming device - Google Patents

Abstract

PURPOSE:To obtain accuracy in the setting of transfer output and electrification output in relation to electrical disturbance when producing a lot of outputs and to prevent the faulty operation of a device resulting from electrical noise by using a contact electrifying-means as a means for electrifying an electrified body. CONSTITUTION:The device judges by the use an output-current detection means for high-voltage output whether an output is normal or not, and when it is abnormal, further judges whether it is continuous or not. In the case where an abnormal current flows at the time of setting the output voltages for the contact electrifying-members 52 and 55, the result of the detection is ignored. Thus, the cause of errors in output currents for the contact electrifying-members 55 and 52 in the setting of the output voltages for the contact electrifying- members such as a transfer roller 55 and an electrification roller 52, which result from electrical disturbance such as pinhole short, etc., between a pair of fixing rollers 59 and 60 and between the electrified body 51 and the contact electrifying-members 52 (55), is removed, and the outputs for the contact electrifying-members 55 and 52 can be properly set.

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 forming an image by an image forming process such as electrophotography, electrostatic recording, etc., including a step of charging an object to be charged such as a photoconductor, a dielectric and a transfer material. Regarding

More specifically, the charging means of the member to be charged brings a roller-type or blade-type conductive member into contact with the surface of the member to be charged as a charging member, and applies a voltage from a power source to the charging member. The present invention relates to an image forming apparatus that is a contact charging unit that charges a surface of an object to be charged to a predetermined polarity and potential.

[0003]

2. Description of the Related Art Conventionally, in an image forming apparatus such as an electrophotographic device or an electrostatic recording device, a charging process for primary charging an image carrier such as an electrophotographic photosensitive member or an electrostatic recording dielectric to a predetermined polarity and potential. And a transfer charging means for electrostatically transferring the transferable image carried on the surface of the image carrier by electrostatically processing the transfer material to the surface of the transfer material. The corona discharge device was commonly used.

However, in recent years, contact charging devices have come to be adopted because they have the advantages that the power supply can be lowered in pressure and that the generation of ozone is extremely small.

As described above, in the contact charging device, a roller-type or blade-type charging member (conductive member) is brought into contact with the member to be charged, and a voltage is applied to the charging member from a power source so that the surface of the member to be charged is predetermined. Charged to the polarity / potential of (including static elimination)
It is what makes me.

FIG. 5 shows a schematic structure of an example of an image forming apparatus using a primary charging processing means of an image carrier and a contact charging means as a transfer charging means. The image forming apparatus of this example is a copying apparatus or a printer using an electrophotographic process.

Reference numeral 51 denotes an electrophotographic photosensitive drum as an image bearing member, which is rotationally driven in a clockwise direction indicated by an arrow at a predetermined peripheral speed (process speed).

Reference numeral 52 denotes a charging roller as a contact charging member which is arranged substantially parallel to the photosensitive drum 51 and is brought into contact with the photosensitive drum 51 with a predetermined pressing force. The charging roller 52 is made of a conductive cored bar 52a such as iron or SUS. A conductive elastic layer 52b of carbon-containing urethane rubber or the like is concentrically and integrally formed on the outer periphery, and both ends of the cored bar 52a are rotatably held by bearings, and a pressure spring (not shown) or the like is also provided. It is pressed against the surface of the photosensitive drum 51 by the pressing means and is driven to rotate as the photosensitive drum 51 rotates.

Reference numeral 53 is a high voltage power source for applying a voltage to the charging roller 52. By applying a predetermined DC voltage or an oscillating voltage (alternating voltage; a voltage whose voltage value changes cyclically with time) to the charging roller 52, the surface of the rotating photosensitive drum 51 is made uniform in a predetermined polarity and potential. Is charged.

The voltage applied to the charging roller 52 may be only the DC voltage (DC method), but the application of the oscillating voltage (AC method) is superior in the uniformity of charging.

In particular, the present applicant has previously proposed (Japanese Patent Application Laid-Open No. 63-
149669, etc.), the DC voltage DC,
The oscillating voltage (DC + AC) superposed with the AC voltage AC having a peak-to-peak voltage that is more than twice the charging start voltage on the surface of the charged body when only the DC voltage is applied to the charged body is applied to the surface of the charged body. The method of charging the toner is effective because it can be uniformly charged.

Next, the charged surface of the rotary photosensitive drum 51 is exposed to light image L by light image exposure means (imaging slit exposure of original image, laser beam scanning exposure, etc.) not shown. , An electrostatic latent image of desired image information is formed on the surface of the rotary photosensitive drum 51. Then, the electrostatic latent image is developed as a toner image by the developing device 54.

On the other hand, a transfer material S is fed from a sheet feeding mechanism (not shown) to a transfer portion between the rotary photosensitive drum 51 and a transfer roller 55 as a transfer means at a predetermined timing and is transferred and transferred. The formed and carried toner image on the side of the photosensitive drum 51 is transferred to the surface of the transfer material S in the process of passing through the section.

The transfer material S that has passed through the transfer portion is separated from the surface of the photosensitive drum 51 and is conveyed and introduced into the image fixing device 58. The transfer material S is passed between the upper and lower fixing roller pairs 59 and 60 to be subjected to image fixing to form an image. It is output as a thing. Reference numeral 57 is a cleaning device for the surface of the photosensitive drum 51 after transfer.

Similar to the charging roller 52, the transfer roller 55 is composed of a conductive cored bar 55a and a conductive elastic layer 55b, arranged substantially parallel to the photosensitive drum 51, and both ends thereof are rotatably held by bearings. The surface of the photoconductor drum 51 is pressed against the surface of the photoconductor drum 51 by a pressure means such as a pressure spring (not shown), and the photoconductor drum 51 rotates in the forward direction at substantially the same peripheral speed.

The transfer material S is introduced into a pressure contact nip portion (transfer portion) between the photosensitive drum 51 and the transfer roller 55 which is in pressure contact with the photosensitive drum 51 so as to be in close contact with the surface of the photosensitive drum 1 and to have a high pressure with respect to the transfer roller 55. By applying a predetermined transfer bias from the power source 56, the back surface of the transfer material is contact-charged with a polarity opposite to the charging polarity of the toner of the formed carrier toner image on the surface of the photosensitive drum 51. Toner image is electrostatically transferred to the surface side of the transfer material S.

A bias voltage is applied to the fixing roller (lower roller) 60 by taking out from the output voltage of the high voltage power source 56 for applying the transfer bias to the transfer roller 55.

The bias output current It 'to the fixing roller 60 (leakage current due to the fixing bias) is smaller than the output current It to the transfer roller 55 (It >>It').
Therefore, it can usually be ignored.

The fixing roller (upper roller) 59 is grounded via a diode 104. Fixing roller 59/60
Because there is an insulating layer, the current is only leakage current. In FIG. 6, 101 is a thermistor for temperature adjustment of the fixing roller 59, which is in contact with the roller 59 in the non-image area.

[0020]

SUMMARY OF THE INVENTION In the above conventional device,
Since the bias voltage to the fixing roller 60 is taken out from the output voltage to the transfer roller 55, a pinhole is generated in the insulating film of the fixing roller 60, or the temperature adjusting thermistor 101.
When the insulating film is peeled off due to abrasion with (a hatched portion a in FIG. 6), the output current to the fixing roller 60 largely flows in an impulse, so that the relation of It >> It 'does not hold. As a result, the output setting to the transfer roller 55 is adversely affected.

The high-voltage power supply control unit of the charging roller 52 can also be made to be similar to the circuit of the transfer roller 55, and the bias voltage to the fixing roller 60 can be taken out from the output voltage to the charging roller 52. As in the case of the transfer roller 55, or when a low withstand voltage defect portion such as a pinhole occurs on the photoconductor drum 51, the charging roller 5
A large impulse current flowing to the charging roller 2 adversely affects the output setting to the charging roller 52.

Therefore, according to the present invention, at the time of setting the output voltage to the contact charging member such as the transfer roller and the charging roller, between the fixing roller pair 59 and 60, or the charged body 51 and the contact charging member 5.
It is possible to eliminate the error factor for the output current to the contact charging member 55/52 due to the electrical disturbance such as the pinhole short circuit between the two (55) and to set the appropriate output of the contact charging member 55/52. The purpose is to do.

[0023]

The present invention is an image forming apparatus having the following configuration.

(1) An image forming apparatus for forming an image by an image forming process including a step of charging a charged body, wherein the charging means of the charged body applies a charging member to the surface of the charged body. Contact charging means for contacting and charging the surface of the body to be charged to a predetermined polarity and potential by applying a voltage to the charging member from a power source, and a voltage control means for controlling the voltage to the charging member, and the voltage control means. Output current detection means for detecting the output current value during voltage control by means of, the judgment means for judging whether or not the output current value has reached a desired value, and the calculation based on the judgment means The calculating means for determining the output voltage, the first judging means for judging whether the output current value is abnormal from the detection result by the output current detecting means, and the abnormality judged by the first judging means are continuous. The second determines whether or not a state
An image forming apparatus, comprising:

(2) When the result of the second judging means is not continuous, the detection result is ignored and the output voltage to the charged body is determined. apparatus.

(3) The member to be charged is a transfer material that is fed between the image carrier and the transfer unit to receive the transferable image formed and carried on the image carrier side, and the transfer unit is the transfer member. It is a contact charging unit that has a charging member that comes into contact with a transfer material as a member to be charged and that charges the transfer material to a predetermined polarity and potential by applying a voltage from a power source to the charging member ( The image forming apparatus according to 1).

(4) The member to be charged is an image carrier for performing image formation by applying an image forming process including a charging process to the member to be charged, and the charging unit of the image carrier is the image carrier. The image according to (1), which is a contact charging unit that has a charging member in contact with the charging member and charges the image bearing member to a predetermined polarity and potential by applying a voltage from a power source to the charging member. Forming equipment.

[0028]

As described above, in the image forming apparatus using the contact charging means as the charging processing means for the body to be charged, it is judged by the output current detecting means of the high voltage output whether or not the output is normal. When it is determined that there is a means for determining whether or not it is continuous, and when an abnormal current flows when setting the output voltage to the contact charging member, means for ignoring the detection result By providing the above, it is possible to eliminate an error factor with respect to the output current to the contact charging member due to the electrical disturbance, and it is possible to appropriately set the output of the contact charging member.

[0029]

Embodiments <First Embodiment> (FIGS. 1 and 2) In this embodiment, the device configuration of the image forming apparatus is the same as that shown in FIG. FIG. 1 shows a circuit diagram of the high-voltage power supply controller of the transfer roller 55.

A positive high voltage is applied to the transfer roller 55, and the high voltage is output by the inverter transformer 3. The inverter transformer 3 is driven by the pulse oscillator 2 via the transistor 8. The pulse signal is rectified by the diode 27 and the capacitor 28 on the secondary side of the inverter transformer 3.

In the high voltage controller 1, OSC is an ON / OFF signal of the pulse oscillator 2, that is, O of high voltage output.
This is an N / OFF signal. DA is a signal that determines the output voltage of the high voltage output, and AD is a signal that indicates the output current of the high voltage output.

The DA output from the high voltage controller 1 is amplified by the operational amplifier 4 and input to the base of the transistor 30. The emitter potential of the transistor 30 is proportional to the high voltage output of the inverter transformer 3. Therefore, the high voltage output Vout is approximately expressed by the following equation from the output voltage of DA.

Vout = {V _DA × (1 + R ₁₅ / R ₁₄ ) −V _BE } N (1) Vout; High-voltage output voltage V _DA ; DA output voltage R ₁₅ of high-voltage controller 1; Resistor 15 R ₁₄ ; resistance 14 V _BE ; _Tr 30 base-emitter voltage N; winding ratio of the inverter transformer 3 When the high voltage output Vout is applied to the transfer roller 55, the output current It is converted into a high voltage by the operational amplifier 5, and the high voltage is output. Input to AD of control unit 1. The output current It at this time is represented by It = V _AD / R ₂₁ (2) V _AD ; AD input voltage R ₂₁ to the high voltage control unit 1;

As described above, the voltage applied to the transfer roller 55 is appropriately set according to the equations (1) and (2).

Here, the high voltage output Vout to the transfer roller 55
Is output as a bias voltage to the fixing roller (lower roller) 60 which is stepped down by the varistor 31 and the resistor 29.

However, since the bias output current It 'to the fixing roller 60 is minute (It >>It') with respect to the output current It of the transfer roller 55, it can usually be ignored. Further, the fixing roller (upper roller) 59 is the same as that shown in FIGS.
Is grounded via the diode 104 in the same manner as.

FIG. 2 is a control flowchart when the transfer output is set in the high voltage controller 1.

.. First, transformer drive pulse oscillator 2
Is turned on (step 10).

.. Next, the DA output is increased by 1 LSB until the AD input reaches a desired value (step 11).
~ 13).

At this time, in step 12, it is monitored whether the AD input is normal. Specifically, a slice level (Vth) is provided at the AD input, and [AD <Vt
h] or not.

.. If it is determined to be abnormal in step 12 (when AD ≧ Vth and an excessive output current flows), the AD input is monitored while the DA output remains constant for a predetermined time (step 14), and the normal state is restored. The processing of steps 11 to 13 is continued, and if not recovered, it is determined that there is a failure and the processing is stopped (step 18).

.. In step 13, when the AD input reaches a desired value, the AD output is sequentially changed within a predetermined time (one round of the transfer roller) so that the AD input becomes constant thereafter.

Further, the average of the DA output during that time is calculated (step 15), and the transfer output is determined from the result (step 19).

.. Also, during the processing of step 15,
Even when it is determined that the AD input is abnormal, the AD input is monitored within the predetermined time (steps 16 and 17), and when the normal state is restored, the process of step 15 is immediately continued.

However, the AD output at the time of abnormality is ignored from the calculation in step 15 until the target value of AD is reached and the processing is continued.

.. If the AD input does not return to the normal state in step 17, it is determined that there is a failure and the processing is stopped (step 18).

.. After the processing of step 15 is completed, the transfer output (DA output) is determined according to the calculation result (step 1
9).

Although the output of the DA is used as the means for determining the high voltage output in this embodiment, it is also possible to use a configuration such as a PWM (pulse width modulation) signal and an LPF (low pass filter). Any voltage setting means may be used. The same applies to the current-voltage conversion means by the operational amplifier 5.

<Second Embodiment> (FIG. 3) FIG. 3 is another control flowchart when the transfer output is set in the high voltage controller 1.

Steps 10 to 14 are the same as the control flowchart of FIG.

In step 14, if the AD input is returned to the normal state, the DA output is temporarily returned by some percentage (DA =
DA * K ... K <1), immediately continue the processing of steps 11 to 13.

In step 14-2, since the position of the transfer roller 55 in the circumferential direction is different during the process of step 14, the AD input is input in step 13 when the process is restarted due to the uneven resistance of the transfer roller 55 in the circumferential direction. This is done so that the target value is not exceeded.

In step 13, when the AD input reaches the desired value, the DA output is successively changed within a predetermined time so that the AD input becomes constant. Further, the average of the DA output during that time is calculated (step 15), and the transfer output is determined from the result (step 19).

During the processing of step 15, AD
If the input is judged to be abnormal, A
D input is monitored (steps 16 and 17), and if it returns to a normal state, DA output is felt for some percentage (step 1).
7-2) Immediately, the process of step 15 is continued.

However, the AD output during the processing of step 17 and the DA output until the target value of the AD input is reached again after the processing of step 17-2 are ignored from the calculation of step 15 and the processing is continued.

If the AD input does not return to the normal state in step 17, it is determined that there is a failure and the processing is stopped (step 18).

After the processing of step 15 is finished, the transfer output (DA output) is determined according to the calculation result (step 19).

<Third Embodiment> (FIG. 4) FIG. 4 is a flow chart showing still another control when the transfer output is set in the high voltage controller 1.

In the control flow of this embodiment, the judgment criteria of whether the AD input is normal in steps 12 and 16 in the control flow of FIG.
-3, step 16-3.

That is, in this embodiment, the DA output is increasing in steps 11 to 13 or A in step 15
During the calculation of the D output, if the AD input change amount with respect to the change of AD1LSB exceeds a predetermined value (ΔAD ≧ ΔVth), it is determined to be abnormal.

The other control processing is the same as the flow of FIG.

Although the contact charging member is the transfer roller 55 in the first to third embodiments, the charging roller 52 is used.
Can be similarly controlled.

[0063]

As described above, according to the present invention, the image forming apparatus using the contact charging means as the charging processing means for the body to be charged includes: a. It is possible to secure the setting system of transfer output and charging output against electric disturbance at the time of multiple outputs. B. Prevents device malfunction due to electrical noise. C. This has the effect of being able to reliably detect abnormal device operation.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a high voltage controller in the image forming apparatus according to the first embodiment.

FIG. 2 is a control flowchart when a transfer output is set in a high voltage controller.

FIG. 3 is a control flowchart when a transfer output is set in a high voltage controller in the image forming apparatus according to the second embodiment.

FIG. 4 is a control flowchart when a transfer output is set in a high voltage controller in the image forming apparatus according to the third embodiment.

FIG. 5 is a schematic configuration diagram of an example of an image forming apparatus.

FIG. 6 is a front view of a fixing roller pair.

[Explanation of symbols]

51 Image Carrier (Electrophotographic Photoreceptor Drum) as Charged Member 52 Charging Roller as Contact Charging Member 53 Charging Bias Applying High Voltage Power Supply 54 Developing Device 55 Transfer Roller as Contact Charging Member 56 Transfer Bias Applying High Voltage Power Supply 57 Cleaning Device 58 image fixing device 59/60 fixing roller pair S transfer material as charged body

Front page continuation (72) Inventor Tatsunori Ishiyama 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Koichi Hiroshima 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. In the company

Claims (4)

[Claims] 1. An image forming apparatus for forming an image by an image forming process including a step of charging a charged body, wherein the charging means of the charged body contacts a charging member to the surface of the charged body. And a charging means for charging the surface of the body to be charged to a predetermined polarity and potential by applying a voltage from the power source to the charging member, the voltage controlling means controlling the voltage to the charging member, and the voltage controlling means. Output current detection means for detecting the output current value during voltage control, judgment means for judging whether or not the output current value has reached a desired value, and output to the charged body by calculation based on the judgment means. The calculating means for determining the voltage, the first judging means for judging whether the output current value is abnormal from the detection result by the output current detecting means, and the abnormality judged by the first judging means are continuous. An image forming apparatus comprising: a second determining unit that determines whether or not the image forming apparatus is in such a state. 2. The image forming apparatus according to claim 1, wherein when the result of the second determination means is not continuous, the detection result is ignored and the output voltage to the charged body is determined. . 3. A charged material is a transfer material which is fed between an image carrier and a transfer means to receive a transferable image formed and carried on the image carrier side, and the transfer means is a transfer material. A contact charging unit that has a charging member that comes into contact with a transfer material as a charging body, and charges the transfer material to a predetermined polarity and potential by applying a voltage from a power source to the charging member. The image forming apparatus according to Item 1. 4. A member to be charged is an image carrier for performing image formation by applying an image forming process including a charging process to the member to be charged, and a charging unit of the image carrier is attached to the image carrier. The image according to claim 1, further comprising a contact charging unit that has a charging member in contact with the charging member and charges the image bearing member to a predetermined polarity and potential by applying a voltage to the charging member from a power source. Forming equipment.