JP3002630B2 - Electrophotographic recording 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 electrophotographic recording apparatus for performing both development and recovery of undeveloped developer in a developing means.

[0002]

2. Description of the Related Art In recent years, in order to reduce waste of toner, a cleanerless type of electrophotographic recording apparatus has been developed in which untransferred toner is collected in a developing apparatus and reused. A conventional electrophotographic recording apparatus of this type is realized by using a non-contact type developing device using a negatively chargeable organic photoreceptor, a two-component developer, and a fixed toner disturbance brush.

[0003]

However, in the case of using a two-component developer, it is necessary to control the toner concentration, so that the structure of the developing device is inevitably complicated and the developing device becomes large. is there. Also, if the potential difference between the charging potential of the photoconductor and the potential of the developing roller is too large, a carrier having a polarity opposite to that of the toner may fly, leading to deterioration of the photoconductor and deterioration of image quality. In addition, there are restrictions on the setting of the voltage applied to the developing roller.

Therefore, it has been considered to use a one-component developer instead of a two-component developer. However, in this case, the potential difference between the charging potential of the photosensitive member and the potential of the developing roller must be increased. And the voltage applied to the developing roller is D
Since it is necessary to use an AC voltage superimposed on C, there is a problem that a power supply for generating this voltage becomes complicated and expensive. In addition, since the toner flies between the developing roller and the photoconductor by an AC electric field, the charge amount of the toner needs to be kept low. In the case of the cleanerless type, however, the transfer residual toner is recharged by the photoconductor charging means, Since the charge is collected by the developing roller using the charge, the non-contact one-component method is difficult to apply.

In view of such circumstances, it is conceivable to use a developing device of a contact developing system using a non-magnetic one-component developer. In this case, since the photoconductor and the developing roller are close to each other via the toner, development faithful to the latent image can be performed. Therefore, if the transfer residual toner on the photoconductor is in the unexposed area (white area), the toner is smoothly collected by the developing roller.

However, in the case of the contact developing method, paper powder adhering from the recording paper to the photoreceptor enters the developing device together with the toner to be collected, and prevents charging of the toner in the developing device. In particular, when a negatively charged photoconductor is used, the toner is negatively charged, but talc among the inorganic fillers (such as talc and calcium carbonate) contained in the paper powder has a good triboelectric chargeability, and has a negative polarity. It has the property of charging the surrounding toner to a positive polarity with a polarity opposite to the original. When the toner is positively charged in this way, the toner adheres to an unexposed area (white area), causing image quality deterioration such as image fogging.

On the other hand, a non-contact type typified by corotron is used for the transfer device. In the case of the non-contact type, the transfer efficiency of the toner fluctuates due to a change in the surrounding environment.
The amount of untransferred toner also varies. Therefore, it is difficult to set an optimal voltage to be applied to the toner disturbance brush on the downstream side. In order to improve this, there is a method of stabilizing the discharge by using a scorotron. However, the transfer device is expensive and the grid is stained by the toner.

As described above, in the conventional electrophotographic recording apparatus, the cost is increased and the image quality is deteriorated due to the complicated configuration of each part.

The present invention has been made in view of such circumstances, and an object of the present invention is to reduce the size and weight of the apparatus, reduce the cost, and deteriorate the photosensitive member while maintaining good image quality. It is an object of the present invention to provide an electrophotographic recording apparatus capable of preventing an increase in the life of an electrophotographic recording medium, always performing good transfer in an optimal state, and reliably collecting the untransferred developer in the developing apparatus. .

[0010]

SUMMARY OF THE INVENTION In order to achieve the above objects, the present invention provides a positively charged photoreceptor, a charging means for charging the surface of the photoreceptor, and a charging means for charging the surface of the photoreceptor. Exposure means for irradiating the surface of the photoconductor with light in accordance with an image to be recorded to form an electrostatic latent image corresponding to the image, and a developer such as a developing roller on the surface of the photoconductor. Developing means for forming a developer image corresponding to the electrostatic latent image formed by the exposure means by adhering a positively charged non-magnetic one-component developer (toner) carried on a carrier; A transfer roller which abuts on the surface of the photoreceptor to pinch and convey a predetermined recording medium together with the photoreceptor and an electric field for moving the non-magnetic one-component developer attached to the photoreceptor to the transfer roller side; Variable transfer bias Transfer means for generating a transfer bias, a transfer means for transferring a developer image formed by the developing means on the surface of the photoreceptor to the recording medium, and a transfer roller after passing through a position where the transfer roller abuts. When the conductive brush that slides on the surface of the photoconductor and the region where the developer image is formed on the surface of the photoconductor passes through a position where the conductive brush slides, the surface potential of the photoconductor is lower than the surface potential of the photoconductor. A low predetermined voltage is applied to the conductive brush, and a region of the surface of the photoconductor where the developer image is not formed passes through a position where the conductive brush slides. A disturbance unit having a power supply unit for applying a predetermined voltage higher than the potential to the conductive brush, a counting unit for counting the number of recording sheets, and a transfer bias setting condition set in advance. Come, and a transfer bias control means for controlling the transfer bias generating means so as to obtain a predetermined level corresponding to the transfer bias to the recording number to said counting means counts.

[0011]

By taking such means, a positively charged photoreceptor, a charging means, a developing means of a contact developing type using a non-magnetic one-limited developer charged to a positive polarity and a transfer of a contact transfer type are used. The means realizes an electrophotographic process and records an image.

Further, the transfer residual toner in the transfer means is recovered by the conductive brush of the disturbance means by applying a predetermined voltage higher than the surface potential of the photosensitive member to the conductive brush during recording. Then, the transfer residual toner collected by the conductive brush is applied to the surface of the photoconductor photoconductor by applying a predetermined voltage lower than the surface potential of the photoconductor to the conductive brush after recording is completed. And is collected in the developing device. Thereby, cleanerlessness is realized.

Further, the transfer bias applied to the transfer roller of the transfer means is variably controlled to a predetermined level in accordance with the number of recording sheets, so that the transfer conditions and the photosensitive member 1 due to the change in the electrical resistance of the transfer roller are changed. Of the potential difference between the surface of the conductive brush roller 61 and the conductive brush roller 61 is compensated.

[0014]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a main configuration of an electrophotographic recording apparatus according to this embodiment.

In FIG. 1, reference numeral 1 denotes a drum-shaped photosensitive member formed of a positively charged organic material, which is rotated in a direction indicated by an arrow by a rotation driving device (not shown). Around the photosensitive member 1, a charging device 2, an exposing device 3, a developing device 4, a transfer device 5 and a toner disturbing device 6 are provided along the peripheral surface thereof.
Are arranged in order toward the downstream side in the rotation direction.

The charging device 2 is of a so-called scorotron type comprising a charging high voltage power supply 21, a wire 22, a grid 23 and a zener diode 24. That is,
High voltage (+ 200μ)
A is controlled at a constant current).
The surface of the photoreceptor 1 is charged by corona discharge generated in step (1).
A zener diode 2 is provided between the wire 22 and the photoconductor 1.
A grid 23, which is grounded via the reference numeral 4, is arranged to uniformly charge the surface potential of the photoconductor 1 to a predetermined potential (for example, +700 V).

The exposure device 3 includes, for example, an LED head, and irradiates the surface of the photosensitive drum 1 with light based on image data to form an electrostatic latent image corresponding to an image to be recorded.

The developing device 4 forms a toner image on the surface of the photoconductor 1 by adhering a non-magnetic one-component toner T to the surface of the photoconductor 1 in accordance with the electrostatic latent image formed by the exposure unit 3. The photosensitive member 1 carries the toner T stored in a toner hopper (not shown).
And a supply roller 42 that supplies the toner T stored in the toner hopper to the developing roller 41.
A developing blade 43 for thinning the toner T carried on the developing roller 41 and frictionally charging the toner T to a positive polarity; and a predetermined voltage (for example, +300)
V) to a developing bias power supply 44 for applying a developing bias and a predetermined voltage (for example, +400) to the supply roller 42.
And a supply bias power supply 45 for applying a supply bias of V). The developing roller 41 and the supply roller 42 are each rotated in the direction of the arrow by a rotation driving device (not shown).

The transfer device 5 transfers the toner image formed on the surface of the photoreceptor 1 by the developing device 4 to the recording paper P, and includes a transfer roller 51 in contact with the photoreceptor 1,
A transfer bias power supply 52 for applying a transfer bias (variable) having the opposite polarity (negative polarity) to the charge potential of the photoconductor 1 to the transfer roller 51; A cleaning bias power supply 53 for applying a transfer roller cleaning bias of a voltage (for example, +1000 V) and a switch 54 for ON / OFF of bias application to the transfer roller 51 and selection of the transfer bias power supply 52 and the cleaning bias power supply 53 are provided. Have. The transfer roller 51 is rotated in a direction indicated by an arrow by a rotation driving device (not shown).

The toner disrupter 6 has a predetermined resistance value (for example, about 10 ⁶ Ω) formed by implanting a large number of hairs 61b made of a conductive material around a shaft 61a. The conductive roller member 6 in contact with the surface of the photoconductor 1
1 and a predetermined voltage (for example, +30)
A brush bias power source 62 for applying a brush bias of 0 V) and a switch 63 for selecting whether to connect the brush bias power source 62 to the conductive roller member 61 or to ground the conductive roller member 61.

Reference numeral 7 denotes a main controller, which controls the entire components of the electrophotographic recording apparatus and realizes a recording operation.
The main control unit 7 has, for example, a microcomputer as a main control circuit, and in addition to a general control unit for controlling each unit to realize an electrophotographic process, a recording sheet counting unit 7a and a transfer bias control unit. 7b. Here, the recording number counting means 7a counts the number of recordings. Transfer bias control means 7b
Controls the level of the transfer bias output from the transfer bias power supply 52 based on the number of recordings counted by the recording number counting means 7a.

Reference numeral 8 denotes a recording control unit, which receives a transfer bias power supply 52, a switch 54,
63, another bias power supply, a rotation drive device for each roller, and the like are actually operated.

FIG. 2 is a circuit diagram showing a specific configuration of the transfer bias power supply 52. Transfer bias power source 52 as shown in this figure, a high-voltage output section 52a for converting the output voltage V _OUT of the predetermined level of the input voltage V _IN as a transfer bias, the output voltage V _OUT of the high-voltage output section 52a Is formed as a switching regulator including a feedback circuit section 52b for stabilizing. Also, the feedback circuit section 52b
, The voltage value Vo obtained by converting the feedback current I by the resistor 201 and the setting voltage obtained by D / A converting the transfer bias setting data given from the recording control unit 8 by the D / A converter 202. The value Vref is compared by a comparator 203,
The result of the comparison is provided to the control circuit 204 of the high voltage output unit 52a. In the high-voltage output unit 52a, the control circuit 204 changes the switching frequency of the switching transistor 205 according to the comparison result of the comparator 203,
The level of the output voltage V _OUT is set to a value corresponding to the transfer bias setting data provided from the recording control unit 8.

Next, the operation of the electrophotographic recording apparatus configured as described above will be described.

First, the surface of the photoreceptor 1 is uniformly charged to +700 V by the charging device 2 and then exposed by the exposing device 3 in accordance with image data to form an electrostatic latent image. At this time, the surface potential of the photoreceptor 1 decreases to about 120 V in the light-irradiated area, that is, the area of the black image, and remains at 700 V in the area not irradiated with the light, that is, the area of the white image.

Subsequently, a developing device 4 is provided on the surface of the photoreceptor 1.
As a result, the toner T adheres in accordance with the electrostatic latent image to form a toner image. Specifically, in the developing device 4, a toner T charged to the same polarity (positive polarity) as the charged potential of the photoconductor 1 is carried on the developing roller 41, and the toner T is brought into contact with the photosensitive drum 1. A developing bias of the same polarity as the charging potential of the photoconductor 1 (potential of the unexposed area) and a low voltage (+300 V) is applied to the developing roller 41 from a developing bias power supply 44, and the developing bias between the electrostatic latent image and the developing bias is By action, photoreceptor 1
Is selectively adhered to the toner T. That is, the photoconductor 1
The toner T does not adhere to the upper charged portion because the photoconductor 1 is at a high potential, and the toner T adheres to the exposed portion where the potential is lowered because the photoconductor 1 is at a low potential. .

The toner T thus adhered to the photosensitive member 1 is transferred to the recording paper P by the transfer device 5. Specifically, during a recording operation (when transfer processing is necessary), the switch 54 is controlled by the transfer bias power supply 52 under the control of the main control unit 7.
Side, and a transfer bias of a polarity opposite to the charging polarity of the photoconductor 1 and the toner T generated by the transfer bias power supply 52 is applied to the transfer roller 51. Due to the electric field generated between the photoconductor 1 and the transfer roller 51 by the transfer bias, the toner T adhered to the surface of the photoconductor 1
The image is transferred onto a recording sheet P that is nipped and conveyed between the photoconductor 1 and the transfer roller 51.

However, it is difficult for the transfer device 5 to transfer all of the toner T adhered to the photoreceptor 1 to the recording paper P, and even if the transfer efficiency is good, it is 10 to 30%.
Of the toner T remains on the photoconductor 1. When the recording paper P comes into contact with the photoreceptor 1, paper powder S adheres to the surface of the photoreceptor 1. The toner T and the paper dust S that have passed through the contact position between the photoconductor 1 and the transfer roller 51 while adhering to the photoconductor 1 in this way reach the conductive brush roller 61. The conductive brush roller 61 is rotationally driven by a rotational driving device, and the bristles 61b are in sliding contact with the surface of the photoreceptor 1. Therefore, the bristle 61b of the conductive brush roller 61 removes and holds the paper dust S attached to the surface of the photoconductor 1. As a result, the paper dust S adhered to the surface of the photoconductor 1 in the transfer process
Is removed from the surface of the photoconductor 1. Paper powder S is toner T
Since the conductive brush roller 61 is not in close contact with the photoconductor 1, the conductive brush roller 61 can be removed from the photoconductor 1 by sliding contact.

In the toner disturber 6, at least the recording area of the photoconductor 1 (the area used for image recording regardless of exposure / non-exposure) is a conductive brush roller 61.
The switch 63 grounds the conductive brush roller 61 under the control of the main controller 7 during the period of passing through the contact position. That is, the brush bias applied to the conductive brush roller 61 is set to 0V. Therefore, if the toner T adhered to the photoreceptor 1 remains positive, the surface potential of the toner T of the positive polarity at the adhering position (reduced to, for example, 70 V due to the transfer bias).
Is higher than the potential of the conductive brush roller 61, the toner T is attracted to the conductive brush roller 61 side. In addition, for the toner T whose polarity has been inverted to the negative polarity due to the influence of the transfer bias, the surface potential at the adhesion position is lower than the potential of the conductive brush roller 61, so that the toner T is a photosensitive member. It passes through the contact position of the conductive brush roller 61 while being adhered to 1.

The negatively charged toner T that has passed through the contact position of the conductive brush roller 61 while being adhered to the photoreceptor 1 is again inverted in polarity to the positive polarity by the charging device 2, and then the photoreceptor 1 and the developing roller 41. Reaches the contact position. At this time, if light is applied to the area where the toner T is adhered, the toner T charged to the positive polarity is attracted to the photoconductor 1 side and the photoconductor 1 is directly applied to the photoconductor 1 according to the development principle described above. If the remaining area and the area where the toner T is adhered are not irradiated with light, the positively charged toner T
Is attracted to the developing roller 41 side and is collected by the developing device 4. Incidentally, the amount of the toner T whose polarity is inverted to the negative polarity due to the influence of the transfer bias is very small.
Therefore, the exposure by the exposure device 3 is not hindered.

If the paper dust S remaining on the conductive brush roller 61 adheres to the photoreceptor 1, this is collected together with the toner T by the developing roller 41. Even if S is mixed, the toner T
The paper powder S does not hinder the charging of the toner T because of the positive polarity. Therefore, it is possible to avoid various problems caused by the presence of the paper dust S.

Most of the transfer residual toner charged to the positive polarity is collected by the conductive brush roller 61 during the recording operation. The toner T collected by the conductive brush roller 61 in this manner is returned to the photoconductor 1 when the non-recording area of the photoconductor 1 passes through the contact position with the conductive brush roller 61. That is,
At this time, the switch 63 is turned on to the brush bias power supply 62 side under the control of the main control unit 7, and the conductive brush roller 61 is supplied with +300 V from the brush bias power supply 62.
Is applied. The non-recording area of the photoconductor 1 is transferred to the transfer roller 5 without the recording paper P.
1 is directly contacted, and is greatly affected by the transfer bias, and the surface potential is about -80V. Thus, the toner T collected by the conductive brush roller 61
For (positive polarity), the photoconductor 1 side has a lower potential than the conductive brush roller 61 and is attracted to the photoconductor 1 side. Therefore, the toner T collected by the conductive brush roller 61 is returned to the surface of the photoconductor 1.

The toner T returned to the surface of the photoreceptor 1 is sufficiently charged to a positive polarity by the charging device 2 and then reaches a contact position between the photoreceptor 1 and the developing roller 41. At this time, if light is applied to the area where the toner T is adhered, the toner T charged to the positive polarity is attracted to the photoconductor 1 side and the photoconductor 1 is directly applied to the photoconductor 1 according to the development principle described above. If the remaining area where the toner T is adhered is not irradiated with light, the positively charged toner T is attracted to the developing roller 41 side and collected by the developing device 4.

By the way, since paper dust and toner adhere to the transfer roller 51 in repeated recording operations, the electric resistance value of the transfer roller 51 (hereinafter, referred to as transfer roller resistance value) gradually increases. There is nature. When the transfer roller resistance value increases, the intensity of the electric field formed between the photosensitive member 1 and the transfer roller 51 decreases, and transfer efficiency deteriorates.

If the resistance value of the transfer roller increases, the influence of the transfer bias on the surface potential of the photosensitive member 1 decreases,
After passing through the contact position of the transfer roller 51, the surface potential of the photoconductor 1 changes.

FIG. 3 shows the result of measuring the change in the surface potential of the photosensitive member 1 at the contact position with the conductive brush roller 61 when the transfer bias is fixed at 900 V. FIG. FIG. 3B shows a case where the transfer roller 51 is not used, and FIG. 3B shows a case where the transfer roller 51 is used (used for a recording operation of 20,000 sheets).

As is apparent from this figure, the surface potential of the photosensitive member 1 is about -80 V in the case where the unused transfer roller 51 is used, particularly in a region where the recording paper P is not interposed between the transfer roller 51 and the transfer roller 51. Compared to the case of using the used transfer roller 51, the voltage is significantly changed to about +300 V to +400 V. As described above, the surface potential of the photoconductor 1 at the contact position with the conductive brush roller 61 is +3.
When the voltage is about 00 V to +400 V, the surface of the photoconductor 1 has a higher potential even if a brush bias of +300 V is applied to the conductive brush roller 61. T will not be discharged.

Therefore, in this embodiment, in order to avoid the above-mentioned problems, the main controller 7 counts the number of recordings by the recording number counting means 7a, and controls the transfer bias control means 7
The level of the transfer bias generated by the transfer bias power supply 52 is changed according to the number of recordings according to b.

FIG. 4 shows the light exposure at the contact position with the conductive brush roller 61 when the same transfer roller 51 (transfer roller resistance = 1.6 × 10 ⁹ Ω / cm ² ) is used and the transfer bias is changed. FIG. 4A shows the result of measuring the change in the surface potential of the body 1. FIG.
FIG. 4B shows a case where the transfer bias is set to −1300 V, respectively.

As can be seen from this figure, by changing the transfer bias, the surface potential of the photoreceptor 1 at the contact position with the conductive brush roller 61 can be changed.

In this embodiment, the relationship between the transfer roller resistance value and the transfer bias capable of favorably performing the transfer as shown in FIG. 5 and the transfer roller resistance value with respect to the number of recording sheets as shown in FIG. The change characteristics are obtained by experiments, calculations, or simulations, and based on these data, the relationship between the number of recordings and the transfer bias at which the transfer as shown in FIG. The transfer bias control means 7b of the main control unit 7 changes the transfer bias according to the number of recording sheets so that the relationship between the number of recording sheets and the transfer bias falls within the optimum transfer area as much as possible.

More specifically, as shown by A in FIG. 7, the initial value of the transfer bias is set to -900 V, and the transfer bias is increased to the negative side by 100 V at every printing of 5000 sheets.

Thus, according to the present embodiment, the photosensitive member 1 is of a positive charge type, and the toner T is charged to a positive polarity. This paper dust S does not hinder the charging of the toner T to the positive polarity, and thus has no effect. Therefore, the developing device 4 can be of a small non-magnetic one-component contact developing method with a simple configuration.

In this embodiment, when the recording area on the surface of the photosensitive member 1 passes through the contact position with the conductive brush roller 61, the toner disturbing device 6 uses the toner adhering to the area. Most of T is conductive brush roller 6
1, the non-recording area on the surface of the photoconductor 1 is discharged to the surface of the photoconductor 1 when passing through the contact position with the conductive brush roller 61, and is collected in the developing device 4. A cleaner-less configuration can be realized while having the non-chargeable photosensitive member 1, the developing device 4 of the non-magnetic one-component contact developing method, and the transfer device 5 of the contact transfer system.

According to the present embodiment, the transfer bias is changed in accordance with the number of recording sheets, so that a change in the resistance value of the transfer roller can be compensated for and the optimum transfer can always be performed. Degradation can be prevented. In addition, since the change in the influence of the transfer bias on the surface potential of the photoconductor 1 is reduced, the surface potential of the photoconductor 1 at the contact position with the conductive brush roller 61 can be kept constant. The suction and discharge of the toner T into and out of the toner 61 can be reliably functioned. Therefore,
Even if the resistance value of the transfer roller changes, the transfer residual toner in the developing device 4 can be reliably collected.

The present invention is not limited to the above embodiment. For example, the change state of the transfer bias voltage value by the transfer bias control means 7b is not limited to the one indicated by A in FIG. 7, and may be any state as long as it does not deviate from the optimum transfer area. That is, for example, if the step of changing the transfer bias is reduced, the transfer conditions and the potential difference between the surface of the photoconductor 1 and the conductive brush roller 61 can be more stably controlled.

In addition, various modifications can be made without departing from the gist of the present invention.

[0049]

According to the present invention, a positively chargeable photoreceptor,
A charging unit for charging the surface of the photoreceptor; and an electrostatic latent image corresponding to the image by irradiating light on the surface of the photoreceptor charged by the charging unit in accordance with an image to be recorded. And a non-magnetic one-component developer (toner), which is positively charged and carried on a developer carrying member such as a developing roller, is attached to the surface of the photoreceptor by the exposing means. A developing means for forming a developer image corresponding to the formed electrostatic latent image; a transfer roller which abuts on the surface of the photoreceptor and nips and conveys a predetermined recording medium together with the photoreceptor; Transfer bias generating means for variably generating a transfer bias for generating an electric field for moving the non-magnetic one-component developer to the transfer roller side, formed on the surface of the photoconductor by the developing means. Transfer means for transferring a developer image onto the recording medium, a conductive brush slidably in contact with the surface of the photoconductor after passing through a position where the transfer roller abuts, and the developer image on the surface of the photoconductor. When the area where the conductive brush passes through the position where the conductive brush slides, a predetermined voltage lower than the surface potential of the photoconductor is applied to the conductive brush, and the developer is applied to the surface of the photoconductor. Disturbing means having a power supply means for applying a predetermined voltage higher than the surface potential of the photoconductor to the conductive brush when an area where an image is not formed passes through a position where the conductive brush slides, Counting means for counting the number of recording sheets; and setting the transfer bias to a predetermined level corresponding to the number of recording sheets counted by the counting means based on a preset transfer bias setting condition. With the transfer bias control means for controlling the transfer bias generation means, while maintaining good image quality, it is possible to reduce the size and weight of the apparatus, reduce costs and prevent deterioration of the photoconductor, and extend the life of the apparatus. Thus, an electrophotographic recording apparatus can always perform good transfer in an optimum state, and can surely collect the untransferred developer in the developing device.

[Brief description of the drawings]

FIG. 1 is a diagram showing a main configuration of an electrophotographic recording apparatus according to one embodiment of the present invention.

FIG. 2 is a circuit diagram showing a specific configuration of a transfer bias power supply 52 in FIG.

FIG. 3 shows a result of measuring a change in the surface potential of the photoconductor 1 at a contact position with the conductive brush roller 61 when the transfer bias is fixed at 900 V.
3A shows a case where the transfer roller 51 is unused, and FIG. 3B shows a case where the transfer roller 51 is used (2000).
FIG. 11 is a diagram illustrating a case where the recording operation is performed for zero sheets).

FIG. 4 shows the same transfer roller 51 (transfer roller resistance = 1.
FIG. 6 shows the results of measuring the change in the surface potential of the photoconductor 1 at the contact position with the conductive brush roller 61 when the transfer bias was varied using 6 × 10 ⁹ Ω / cm ² ). 4A shows the case where the transfer bias is set to -900 V, and FIG. 4B shows the case where the transfer bias is set to -1300.
FIG.

FIG. 5 is a diagram illustrating a relationship between a transfer roller resistance value and a transfer bias capable of performing good transfer.

FIG. 6 is a diagram illustrating a change characteristic of a transfer roller resistance value with respect to the number of recording sheets.

FIG. 7 is a diagram showing a relationship between the number of recording sheets and a transfer bias capable of performing good transfer and a change state of a voltage value of a transfer bias by a transfer bias control unit 7b.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photoconductor 2 charging device 3 exposure device 4 developing device 41 developing roller 5 transfer device 51 transfer roller 52 transfer bias power supply 6 toner disturbing device 61 conductive brush roller 62 brush bias power supply 63 ... Switch 7... Main control section 7a... Recording number coefficient means 7b.

Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) G03G 21/00 370-540 G03G 21/14 G03G 21/00 G03G 21/10-21/12 G03G 13/14-13 / 16 G03G 15/14-15/16 103

Claims (1)

(57) [Claims] 1. A positively charged photoreceptor, charging means for charging the surface of the photoreceptor, and light on the surface of the photoreceptor charged by the charging means in accordance with an image to be recorded. Exposure means for irradiating and forming an electrostatic latent image corresponding to the image, by attaching a positively charged non-magnetic one-component developer carried on a developer carrier to the surface of the photoreceptor. A developing unit that forms a developer image corresponding to the electrostatic latent image formed by the exposing unit; a transfer roller that abuts on a surface of the photoconductor, and that sandwiches and conveys a predetermined recording medium together with the photoconductor; Transfer bias generating means for variably generating a transfer bias for generating an electric field for moving the non-magnetic one-component developer attached to the photoconductor to the transfer roller side, wherein the developing means is provided on the surface of the photoconductor. Formed by Transfer means for transferring the developer image onto the recording medium, a conductive brush slidably in contact with the surface of the photoconductor after passing through a position where the transfer roller abuts, and the developer among the surface of the photoconductor. When a region where an image is formed passes through a position where the conductive brush slides, a predetermined voltage lower than a surface potential of the photoconductor is applied to the conductive brush, and the developing is performed on the surface of the photoconductor. Disturbing means having a power supply means for applying a predetermined voltage higher than the surface potential of the photoconductor to the conductive brush when an area where the agent image is not formed passes through a position where the conductive brush slides, Counting means for counting the number of recording sheets; and, based on a preset transfer bias setting condition, setting the transfer bias to a predetermined level corresponding to the number of recording sheets to be counted by the counting means. Ku electrophotographic recording apparatus characterized by comprising a transfer bias control means for controlling the transfer bias generating means.