JP2972021B2 - 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, and more particularly to an electrostatic image forming apparatus having a function of improving the performance of separating non-image paper passing through a transfer section from a photosensitive drum.

[0002]

2. Description of the Related Art In an electrostatic image forming apparatus shown in FIG. 2, a charging section 2 having a corona charger 2a, a developing section 3 having a developing section 3a, and a transfer section 4a are provided around a photosensitive drum 1. A transfer unit 4 having a charge removal unit 5 and a charge removal unit 5 having a charge removal unit 5a are arranged in this order in the rotation direction X of the photosensitive drum 1, and a transfer unit 4 is provided with a sheet charge removal unit 6; A cleaner 7 is provided between the neutralization unit 6 and the neutralization unit 5. In addition, a paper feed unit 8 having a paper feed roller (registration roller) 8a, a paper transport unit 9, and a fixing unit 10 are provided.

In this image forming apparatus, an original image is exposed on the surface of the photosensitive drum 1 charged by the corona charger 2a by the action of an optical system (not shown) to form an electrostatic latent image. Then, the toner is adhered in the developing unit 3, and a toner image is formed on the surface of the photosensitive drum 1. Then, the transfer unit 4 electrostatically transfers the toner image to the sheet 100 fed from the sheet feeding unit 8. The paper 100 to which the toner image has been transferred is sent to the fixing unit 10 via the paper transport unit 9 and the toner image is thermally fixed. Also, the photosensitive drum 1
After the dust is removed by the cleaner 7, the charge is removed by the charge removing unit 5, whereby one cycle is completed.

[0004] As shown in FIG.
A paper entry guide 11 is provided between the printer and the transfer unit 4. The distance between the leading end of the entry guide 11 and the photosensitive drum 1 is set to a narrow interval of 1.5 mm or less in order to prevent image bleeding due to transfer. Paper 1 to move to 4
It is unavoidable that a resistance occurs at the time of the transition from 00 to 00, and the resistance at that time becomes a factor that lowers the transportability of the paper 100.

Therefore, as can be inferred from the time chart of FIG. 4, before the rear end of the paper 100 to which the feeding force is applied by the paper feed roller 8a is separated from the paper feed roller 8a, The transfer output of the transfer unit 4 is turned on before the leading end reaches the leading end of the toner image on the photosensitive drum 1, and even after the trailing end of the sheet 100 is separated from the paper feed roller 8a, the photosensitive drum 1 The paper 100 is stably conveyed by the electrostatic attraction effect generated between the paper drum 100 and the rotating operation of the photosensitive drum 1. The ON state of the transfer output is maintained until the rear end of the sheet 100 is separated from the leading end of the entrance guide 11. Thereafter, since the above-described resistance to the paper 100 is eliminated, the paper 100 is sent to the fixing unit 10 by the transport force of the transport unit 9. On the other hand,
The separation output of the paper discharging unit 6 is set to O immediately after the transfer output is turned on.
N is set, and when the separation output is turned on, the sheet 100 electrostatically attracted to the photosensitive drum 1 is turned on.
Is removed, and the paper 100 is easily separated from the photosensitive drum 1 by the stiffness (rigidity, stiffness) of the paper 100.

[0006]

In the above-described image forming apparatus, the sheets 100 are separated from a sheet bundle in which non-image sheets such as slip sheets and covers and sheets (normal sheets) on which images are formed are mixed. When the image forming process described above is performed by feeding the sheet to the sheet feeding unit 8 one by one, the image exposure on the surface of the photosensitive drum 1 is not performed on the non-image paper (the electrostatic latent image is not formed). Of charge output in 2
F, or the blank lamp 12 is turned on to erase the charge on the surface of the photosensitive drum 1. Therefore, the toner is not attached to the non-image paper in the developing unit 3.

In this case, in the transfer section 4, no toner is interposed between the surface of the photosensitive drum 1 and the non-image paper. Therefore, the electrostatic attraction between the photosensitive drum 1 and the non-image paper due to the transfer output being turned on is too strong, and even if the separation output of the paper static elimination unit 6 is turned on, the non-image paper is turned on. Depending on the waist, a situation occurs in which the non-image paper hardly peels off from the photosensitive drum 1, which leads to the occurrence of a jam.

In order to solve such a situation, in the image forming process when the non-image paper is fed into the transfer unit 4, the transfer output of the transfer unit 4 is turned off to cause the above-mentioned electrostatic attraction effect. In such a case, the conveyance force applied to the non-image paper is eliminated due to the electrostatic attraction action. The image paper may not be conveyed, which may lead to a jam.

As described above, in the conventional image forming apparatus, the transfer output of the transfer unit is turned on at a fixed timing regardless of whether the paper fed to the transfer unit is normal paper or non-image paper. Since the paper was conveyed using the electrostatic attraction force between the photosensitive drum and the paper generated with it, the non-image paper may not be easily separated from the photosensitive drum in some cases. However, there is a problem that this makes the conveyance state of the non-image paper particularly unstable.

The present invention has been made in view of the above problems. That is, the present invention prevents the electrostatic attraction action from occurring between the photosensitive drum and the non-image paper when the conveyance force of the paper feed roller of the paper supply unit is applied to the non-image paper. The non-image paper is prevented from being attracted to the photosensitive drum, and when the conveyance force of the paper feeding roller of the paper feeding unit is not applied to the non-image paper, the above-mentioned electrostatic attraction effect is generated to cause the non-image paper to be statically applied to the non-image paper. It is an object of the present invention to provide an image forming apparatus capable of applying a conveying force by an electro-adsorption effect and a rotation operation of a photosensitive drum.

[0011]

According to a first aspect of the present invention, there is provided an image forming apparatus, comprising: a charging section, a developing section, a transfer section, and a charge removing section around a photosensitive drum; In the image forming apparatus in which the paper fed from the paper feeding unit is arranged in this order in the rotation direction of the photosensitive drum and fed to the fixing unit via the transfer unit, the transfer unit is used when forming an image on the paper. to transfer output, and wherein the set configured to non-image sheet which is not an image formed on the sheet is oN transfer current delay in the middle stage of passing through the transfer portion.

[0012] According to the image forming apparatus according to claim 2 of the present invention, transfer output of the transfer portion of the non-image sheet which is not the image formation, the rear end of the radio image paper sheet feeding roller of the paper feed portion characterized in that it is set to be oN before leaving
And

[0013]

According to the first aspect of the present invention, since the paper is non-image paper, there is no need to transfer the toner image on the photosensitive drum onto the paper. Therefore, even if the transfer output is OFF, there is no hindrance to the execution of the image forming process. On the other hand, when the transfer output is set to OFF at the initial stage of feeding the paper to the transfer unit, the paper is not attracted to the photosensitive drum at that stage, and the separability of the paper from the photosensitive drum is improved. Then, in the middle stage where the paper is passing through the transfer portion, delayed transfer output is set to ON by Tei because electrostatic attraction acting between the photosensitive drum and the paper with it occurs, By this action and the rotation action of the photosensitive drum, a conveying force is applied to the sheet. And the transfer unit
Since the transfer output is turned on with a delay, it may be turned on unnecessarily.
And not.

According to the second aspect of the present invention, the transfer output is turned on before the trailing edge of the sheet leaves the sheet feeding roller of the sheet feeding section.
In the initial stage of feeding the paper to the transfer unit, the paper feed roller applies a conveying force to the paper, and in the middle of the passage of the paper through the transfer unit, the rear end of the paper is fed by the paper feed roller. Before moving away from the sheet, the conveyance force due to the above-mentioned electrostatic attraction action and the rotation action of the photosensitive drum is applied to the sheet.
Therefore, the sheet is always in a state in which the conveying force is applied.

[0015]

FIG. 1 is a time chart showing a transfer output, a feed roller driving clutch and a separation output in an image forming apparatus according to an embodiment of the present invention. The image forming apparatus according to the embodiment of the present invention includes the same components as those of the image forming apparatus described with reference to FIG.

In the following, the first sheet and the third sheet fed from the sheet feeding section 8 to the fixing section 10 via the transfer section 4 are ordinary paper, and the second sheet is non-image paper. An example is described.

As shown in FIG. 1, the first normal paper is
Is inserted into the sheet feed roller 8a within the time from t1 to t2.
Is applied to the ordinary paper. t1 is the time when the drive clutch of the paper feed roller 8a is turned on, and t2
Is the time immediately after the rear end of the normal paper has passed the paper feed roller 8a. Then, the normal paper inserted into the paper feed unit 8 is temporarily stopped when its leading end reaches the paper feed roller 8a, and the leading end of the image on the photosensitive drum 1 and the leading end of the normal paper are transferred to the transfer unit 4. Are set to coincide with each other. Then, at that timing, the drive clutch of the paper feed roller 8a is turned on, and the normal paper is fed out of the paper feed unit 8 by the conveyance force of the paper feed roller 8a, and supplied to the transfer unit 4 via the entrance guide 11 (see FIG. 3). Sent.

In the case of the first normal sheet, the transfer output of the transfer unit 4 is slightly before the leading end of the paper reaches the transfer unit 4 (t).
(Within the time of 1 to t2) (the transfer voltage
The supply is started) , and a short time after the rear end of the paper has passed through the transfer unit 4 (after the time t2 ) , the sheet is turned off (the transfer unit 4).
The supply of the transfer voltage to the sheet is stopped) , and the sufficient transfer performance over the entire sheet can be obtained by such control. The separation output of the paper discharging unit 6 is such that the transfer output is O
ON immediately after N, and OF immediately after transfer output OFF
F is controlled.

The same applies to the third ordinary sheet to which the conveying force by the sheet feeding roller 8a is applied within the time period from t5 to t6.

When the second non-image paper is inserted into the paper feeding section 8, the conveying force of the paper feed roller 8a is applied to the non-image paper within the time period from t3 to t4. t3 is a time point when the drive clutch of the paper feed roller 8a is turned on, and t4 is a time point immediately after the rear end of the non-image paper has passed the paper feed roller 8a. The non-image paper inserted into the paper feeding unit 8 is temporarily stopped when the leading end thereof reaches the paper feeding roller 8a,
The timing is set such that the position corresponding to the leading end of the image on the photosensitive drum 1 and the leading end of the non-image paper coincide in the transfer unit 4. Then, at that timing, the drive clutch of the paper feed roller 8a is turned on, and the non-image paper is sent out of the paper feed unit 8 by the conveyance force of the paper feed roller 8a, and is sent to the transfer unit 4 via the entrance guide 11 (see FIG. 3). Will be fed.

In the case of non-image paper, the transfer output of the transfer unit 4 is
At the initial stage when the first half of the paper passes through the transfer unit 4, the control is turned off. Even if such control is performed, the transfer of the toner image is not necessary for the non-image paper, so that the image forming process is not performed. Does not hinder execution.
When the transfer output is controlled to be OFF as described above, no electrostatic attraction action occurs between the photosensitive drum 1 and the paper 100 in the transfer unit 4, so that the non-image paper is stuck on the photosensitive drum 1. There is no electroadsorption, and the separation performance is improved accordingly. However, if the transfer output is maintained in the OFF state until the rear end of the non-image paper passes through the transfer unit 4, no conveyance force is generated by electrostatic attraction, so that the rear end of the non-image paper is At a point away from the paper feed roller 8a, a conveyance failure occurs.

Therefore, the transfer unit 4 transfers the paper to the transfer unit 4.
In the middle of passing through , ie, in this embodiment ,
As shown in the time chart of FIG.
Compared with chart second half of the non-image sheet is controlled by delaying the transfer output so that turns ON at the stage of passing. And
More specifically, the timing at which the transfer output is controlled to ON is set slightly before the timing at which the trailing end of the non-image paper leaves the paper feed roller 8a (indicated by the symbol T in FIG. 1). ing.

According to the image forming apparatus having the transfer unit 4 controlled as described above, when the first half of the non-image paper passes through the transfer unit 4, the conveying force of the paper feed roller 8a is reduced. When the second half passes through the transfer section 4, the conveying force due to the electrostatic attraction between the photosensitive drum 1 and the non-image paper and the rotating action of the photosensitive drum 1 are applied to the non-image paper, respectively. No electrostatic attraction action occurs when the first half passes through the transfer unit 4. Therefore, stable conveyance (paper passing) is performed even on non-image paper, and occurrence of jam due to poor separation is suppressed.

When an image forming process is performed on non-image paper, the transfer output of the transfer unit 4 is generally turned off until the entire non-image paper passes through the transfer unit 4.
By doing so, electrostatic attraction of non-image paper to the photosensitive drum 1 is prevented. Therefore, in this one:
The releasability of the non-image paper from the photosensitive drum 1 becomes extremely good. However, if the transfer output is maintained in the OFF state until the trailing end of the non-image paper passes through the transfer unit 4, no conveyance force is generated due to electrostatic attraction.
When the trailing end of the non-image paper is separated from the paper feed roller 8a, a conveyance failure occurs. On the other hand, as in the above-described embodiment, the transfer output of the transfer unit 4 is turned off at the initial stage of sheet feeding to the transfer unit 4 and turned on at the middle stage of the sheet passing through the transfer unit 4. In this way, after the trailing end of the non-image paper is separated from the paper feed roller 8a, as described above, the electrostatic adsorption of the non-image paper to the photosensitive drum 1 and the rotation of the photosensitive drum 1 are performed. The imageless paper is stably conveyed by the conveying force due to the action.

As shown in FIG. 3, the transport unit 9 often has a paper suction unit 9a.
When the non-image paper is attracted to a, the non-image paper is reliably transported by the transport unit 9. However, such a transport state cannot be expected in the case of an image forming apparatus employing the transport unit 9 without the paper suction unit 9a. Further, since the non-image paper is small in size, the trailing end of the non-image paper may be separated from the paper feed roller 8a before the suction action by the paper suction unit 9a is exerted. When the trailing end of the non-image paper is separated from the paper feed roller 8a, a conveyance failure occurs. On the other hand, if the non-image paper is separated from the photosensitive drum 1 due to its stiffness in the initial stage of the non-image paper feeding to the transfer unit 4 as in the above embodiment, the non-image paper is Even if the photosensitive drum 1 is electrostatically attracted in the course of passing through the transfer section 4, reliable peeling is performed, and at the same time, a stable conveyance force is obtained by the electrostatic attraction action at the transfer point.

[0026]

Effects of the Invention by the invention of claim 1, wherein lever, forms an image
Only when it is necessary to apply the conveying force to the non-image paper in the case where it is not formed , the non-image paper is attracted to the photosensitive drum and the conveying force is applied, so that the transfer unit is wastefully turned ON.
Without this will transfer part no image sheet having passed through the are easily separated from the much photosensitive drum, its it leads to improved separation of non-image sheet from the photosensitive drum, jam occurrence
Can be suppressed .

According to the second aspect of the present invention, the conveying force by the paper feed roller and the conveying force caused by the attraction of the non-image paper to the photosensitive drum are continuously applied to the non-image paper. The separation of the non-image paper from the body drum is improved, and the occurrence of a jam when the image forming process is performed on the non-image paper is suppressed.

[Brief description of the drawings]

FIG. 1 is a time chart showing a sheet feed roller clutch, a transfer output, and a separation output in an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of an image forming apparatus.

FIG. 3 is an enlarged configuration diagram of a main part of FIG. 2;

FIG. 4 is a time chart showing a paper feed roller clutch, a transfer output, and a separation output in a conventional image forming apparatus.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photoconductor drum 2 charging unit 3 developing unit 4 transfer unit 5 static elimination unit 8 paper feed unit 100 paper X rotation direction of photoconductor drum

──────────────────────────────────────────────────続 き Continued on the front page (72) Yoshikazu Harada 22-22, Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (56) References JP-A-55-153953 (JP, A) JP-A-60 −118165 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) G03G 15/16

Claims (2)

(57) [Claims] A charging unit, a developing unit, a transfer unit, and a charge removing unit are arranged around a photosensitive drum in this order in a rotation direction of the photosensitive drum, and a sheet fed from a paper supply unit is transferred to the transfer unit. In the image forming apparatus which is fed to the fixing unit through the transfer unit, the transfer unit outputs the transfer output when the non-image paper on which the image is not formed on the paper is passing through the transfer unit with respect to the transfer output when forming the image on the paper. an image forming apparatus comprising set configured is turned ON with a delay. 2. The transfer output of the transfer section of the non-image paper on which no image is formed is set to be turned on before the rear end of the non-image paper leaves the paper feed roller of the paper feed section. The image forming apparatus according to claim 1, wherein: