JP3379812B2 - Transfer transfer device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a copying machine, a printer,
The present invention relates to a transfer / transport device using a dielectric belt provided in an electrophotographic image forming apparatus such as a facsimile.

[0002]

2. Description of the Related Art In electrophotographic image forming apparatuses such as copying machines, printers and facsimiles, for example, transfer paper (recording medium) is electrostatically adsorbed on a transfer belt which is a dielectric belt, In some cases, there is provided a transfer / transport device that transfers a toner image (image) on an image carrier and transports the toner image to the next step by a rotating transfer belt.

In an image forming apparatus having such a transfer / transport device, when the transfer paper on which the toner image is transferred is separated from the transfer belt, the separation causes an increase in the gap between the transfer paper and the transfer belt. As the voids increase, the electric charge of the transfer paper rapidly increases the potential between the voids, causing peeling discharge, which may cause image distortion.

Therefore, in such a transfer / conveying device of the related art, as shown in, for example, Japanese Unexamined Patent Publication No. 4-139475, a charge removal charger for removing charge from the toner and the transfer paper at a position where the transfer paper is separated from the transfer belt. It also has a corona charger. An alternating current corotron is generally used as such a corona charger. Further, some conventional transfer / conveyance devices are provided with a charge eliminating brush at a position where the transfer paper is separated from the transfer belt.

[0005]

However, in the case of the above-mentioned static elimination charger, when it is operated to perform corona discharge, ozone and nitrogen oxides harmful to the human body and the environment at that time are discharged. Since this occurs, there is a problem that the processing is troublesome and the cost of the processing makes the entire apparatus expensive.

Further, even when the static elimination brush is provided, there is still a problem that ozone and the like are generated, though not as much as the static elimination charger of the AC corotron, and in the case of the static elimination brush, the static elimination target object is removed. On the contrary, if the contact conditions, the brush material, the resistance, etc. are not set quite rigorously, there is a problem that the static elimination brush may cause image disturbance of the brush pitch.

The present invention has been made in view of the above problems, and a recording medium such as a transfer paper is a dielectric material such as a transfer belt without providing a discharging means for performing corona discharge that generates ozone or the like. The object is to prevent image distortion at a position where the image is separated from the belt. It is also an object to prevent image distortion even in a situation where the resistance of the recording medium is high.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a transfer and transport device as described above, in which a recording medium is provided near a position where the recording medium is separated from the dielectric belt. The conductive member is provided substantially parallel to the belt surface of the linear transport unit , the conductive member is grounded, and the surface of the dielectric belt of the conductive member facing the belt surface of the linear transport unit and the belt of the dielectric belt. Distance between faces is 5
It is obtained by a mm or less.

Further, an electric field generating means is connected to the conductive member, and the distance between the surface of the conductive member facing the belt surface of the linear conveying portion of the dielectric belt and the belt surface of the dielectric belt is set. It may be 10 mm or less. In the transfer / transport device, the guide member for guiding the recording medium immediately after being separated from the dielectric belt may be formed of a conductor or a medium resistance body having a volume resistivity of 10 ¹² Ωcm or less.

[0010]

According to the transfer / conveying apparatus having such a structure, since the conductive member is provided in the vicinity of the position where the recording medium is separated from the dielectric belt, the recording medium on which the toner image is transferred is not In the vicinity of the position where the belt is separated from the body belt, a new electric field is generated between the conductive member and the recording medium, so that the electric field fluctuation is suppressed, so that the image disturbance can be prevented.

Further, the conductive member is grounded, and the distance between the surface of the conductive member facing the belt surface of the linear conveying portion of the dielectric belt and the belt surface of the dielectric belt is set to 5 mm or less . Therefore , a stronger new electric field is effectively generated between the conductive member and the recording medium, and the effect of preventing the image distortion becomes great.

Further, when the electric field generating means is connected to the conductive member, the electric field for suppressing the fluctuation of the electric field between the conductive member and the recording medium is strengthened, so that the conductive member and the belt surface of the dielectric belt are connected. Even if the above distance is set to 10 mm or less, image distortion can be prevented. This makes it difficult for the toner image held on the recording medium and still in the unfixed state to come into contact with the conductive member, so that image rubbing that occurs when the toner image comes into contact with the conductive member can be prevented.

If the guide member is formed of a conductor or a medium resistance member having a volume resistivity of 10 ¹² Ωcm or less, the recording medium separated from the dielectric belt is formed by both the conductive member and the guide member. Since the electric field fluctuation can be effectively suppressed, the image disturbance can be prevented more effectively.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a schematic block diagram showing the structure of a transfer / transport device and its vicinity in an electrophotographic image forming apparatus showing an embodiment of the present invention, and FIG. FIG.

In the transfer / transport device 1, a part of a transfer belt 10, which is a dielectric belt, is provided in contact with a photosensitive drum 2, which is an image carrier, as shown in FIG. The transfer / transport device 1 rotates the transfer belt 10 through a ground roller 9 and a transfer belt 10 that is rotatable in the direction of arrow A while electrostatically adsorbing a transfer paper P that is a recording medium. A driving unit including a motor 11 for moving the power source, a power source 12 that is a unit that applies an electric charge to the transfer belt 10, and a plate-shaped guide member 13 that guides the transfer sheet immediately after being separated from the transfer belt 10 are provided. There is.

Then, the toner image formed on the photosensitive drum 2 through the known electrophotographic process is transferred onto the transfer paper P by the transfer / transport device 1, and the transfer belt 10 which rotates the transfer paper P. Fixing device for the next process (not shown)
Transport to. As shown in FIG. 2, the transfer / conveyance device 1 has a plate-shaped conductive member near the position where the transfer paper is separated from the transfer belt 10 and is substantially parallel to the belt surface of the linear transfer unit 10 a of the transfer belt 10. The elastic member 14 is provided.

As shown in FIG. 1, the transfer belt 10 is stretched between a bias roller 6 and a ground roller 9, which are rotatably supported, and the ground roller 9 is driven to rotate by a motor 11. Rotate in the direction of arrow A.
The bias roller 6 also functions to apply a transfer voltage. The transfer belt 10 has, for example, a medium volume resistance (electrical resistance) of 10 ⁶ to 10 ¹² Ωcm.

A backup roller 7 is rotatably provided on the rear surface of the linear conveying portion 10a of the transfer belt 10, and the contact width of the transfer belt 10 with respect to the photosensitive drum 2 by the backup roller 7 (left and right direction in FIG. 1). Width),
It has a predetermined width suitable for transfer.

A grounding roller 8 is provided between the backup roller 7 and the grounding roller 9, and the grounding roller 8 is mounted on the transfer belt 10.
It is possible to transfer to the back of the. Further, the tip of the cleaning blade 5 is slidably brought into contact with the surface of the portion of the transfer belt 10 which is wound around the ground roller 9, so that the toner and the like adhering to the surface of the transfer belt 10 is removed. When rotating, it is scraped off for cleaning.

Below the cleaning blade 5,
The recovery bottle 4 is provided so that the cleaning blade 5 collects the toner and other adhered substances scraped off the surface of the transfer belt 10. The transfer belt 10 is provided on the left side of the ground roller 9 in FIG.
A guide member 13 is provided for guiding the transfer paper after being separated from the next transfer process.

The bias roller 6, the backup roller 7, and the grounding rollers 8 and 9 which are grounded respectively.
Are rotatably supported by the same support frame 15 (only a part of which is shown for the sake of complexity), and the support frame 15 is rotatably supported with the shaft portion of the ground roller 9 as a fulcrum. Has been done. Its support frame 1
5, one end portion of a swing lever 16 whose center portion is swingably supported is rotatably attached to the lower right portion in FIG.

The other end of the swing lever 16 is rotatably attached to the movable iron core of the solenoid 3, and when the solenoid 3 is turned on, the swing lever 16 is turned on.
Is oscillated counterclockwise to the position shown in FIG. 1, and the support frame 15 is rotated to the right upward in the figure with the shaft portion of the ground roller 9 as a fulcrum, and the linear transport portion 10a of the transfer belt 10 is rotated.
Contacts the surface of the photoconductor drum 2 with the above-mentioned predetermined width.

When the solenoid 3 is turned off,
The support frame 15 is rotated downward from the position shown in FIG. 1 by its own weight or a biasing force of a weak spring, and the transfer belt 1
0 separates from the surface of the photosensitive drum 2.

In this image forming apparatus, transfer sheets are fed out one by one at a predetermined timing from a sheet feeding cassette (not shown), and the leading end of the transfer sheet is held by the registration roller 17 and the roller 18 which is pressed against and rotated by the transfer roller. After being stopped and adjusted in timing, it is conveyed again.

When the leading edge of the transfer paper P reaches near the contact portion between the photosensitive drum 2 and the transfer belt 10, the solenoid 3 is turned on at that timing, and the swing lever 16 is turned on.
1 is oscillated counterclockwise to the position shown in FIG. 1 to move the support frame 15 together with the transfer belt 10 and the rollers around which the support frame 15 is stretched upward in FIG. As a result, the linear transport unit 10a of the transfer belt 10 contacts the surface of the photosensitive drum 2.

When the transfer belt 10 comes into contact with the photosensitive drum in this manner, a current is supplied from the power source 12 to the bias roller 6 or 7 (or both of them as shown). Then, as described above, since the transfer belt 10 is formed to have a medium volume resistance of 10 ⁶ to 10 ¹² Ωcm, the electric charge charged there is closer to the ground roller 9 side. The voltage gradually drops to 9 and 9, so that the voltage gradually drops.

In such a charged state of the transfer belt 10,
The transfer / transport device 1 transfers the toner image (image) formed on the photosensitive drum 2 onto the transfer paper P. That is, in the vicinity of the photosensitive drum 2 of the transfer belt 10,
The toner image electrostatically held on the photoconductor drum 2 by being charged with a polarity opposite to the polarity applied to the transfer belt 10 is transferred onto the transfer paper P.

The transfer paper P on which the toner image is transferred is polarized by the electric charge applied by applying the transfer voltage to the bias roller 6 or 7, and the true electric charge on the transfer belt 10 and the transfer paper P are transferred. An electrostatic force is generated by the polarized electric charges of the transfer paper P, and the transfer paper P is adsorbed on the transfer belt 10.

In this way, the transfer paper P attracted onto the transfer belt 10 is transferred to the transfer belt 1 which rotates in the direction of arrow A.
0 is conveyed to the left in FIG. 1, and in the course of the conveyance, the electric charge charged there gradually flows to the grounding rollers 8 and 9 through the transfer belt 10 of medium resistance, so that the charge amount is gradually eased. Will be done. The speed at which the charge amount is eased depends on the resistance value R of the transfer paper P.
And is greatly influenced by the capacitance C and is represented by a time constant τ of τ = CR.

The transfer paper P conveyed by the transfer belt 10 has the weakest electrostatic force (adsorption force) to the transfer belt 10 in the vicinity of the ground roller 9, so that it is wound around the ground roller 9 having a relatively small diameter. The transfer belt 10 is separated from the transfer belt 10 by the curved surface portion of the transfer belt 10 and the separation force (curvature separation) due to the strength of the transfer paper itself.

Then, the transfer paper P is the guide member 13
It is conveyed to the fixing section while being guided by. In order to use the curved surface portion of the transfer belt 10 to separate the curvature of the transfer paper according to the strength of the waist of the transfer belt, the roller diameter of the ground roller 9 is set to 14 mm.
It should be about φ16 mm.

In this way, at the timing when the trailing edge of the transfer paper P transported in the direction of arrow A in FIG. 1 by the transfer transport device 1 passes through the nip portion where the photosensitive drum 2 and the transfer belt 10 are in contact with each other, The solenoid 3 is turned off. Then, since the support frame 15 that supports each roller such as the ground roller 9 in a unit shape rotates in the clockwise direction in FIG. 1 opposite to the above case with the shaft portion of the ground roller 9 as a fulcrum,
The transfer belt 10 separates from the surface of the photosensitive drum 2.

As described above, since the transfer belt 10 is separated from the photosensitive drum 2 when the image is not transferred to the transfer paper and is not transferred, deterioration of the surface of the photosensitive drum 2 caused by contact friction between them is prevented. You can

On the transfer belt 10 which rotates in the direction of arrow A in FIG. 1, there is also residual toner that is not transferred onto the transfer paper but is scattered and directly adheres to it, but this residual toner is also grounded. Since the charge amount is relieved by the charge removal by the roller 9, the toner is scraped off by the cleaning blade 5 in a state where the electrostatic attraction force to the transfer belt 10 is weakened and collected in the collection bottle 4.

By the way, in the transfer / transport device 1, as described above, the plate-shaped conductive member 14 is disposed near the position where the transfer paper is separated from the transfer belt 10, as shown in FIG. There is. Then, the lower surface 14 of the conductive member 14
The distance between a and the surface 10a of the transfer belt 10 facing it is d.

[0036]

[Table 1]

Table 1 shows that the transfer member 1 is provided with the conductive member 14.
The results of experiments conducted to examine the state of image disturbance due to the difference in the presence or absence of grounding and the difference in the distance d with and without is shown. , △, ○, ×: There is image distortion,
Δ: slight image disturbance, ◯: no image disturbance (the same applies to Tables 2 and 3). According to this experimental result, when the conductive member 14 is provided, a good result with respect to image distortion is obtained as compared with the case where the conductive member 14 is not provided.

That is, if the conductive member 14 is provided, it is possible to suppress image disturbance even if it is not grounded, as compared with the case where it is not provided. Then, if the conductive member 14 is grounded as shown in FIG. 2, the effect of suppressing image distortion is increased.

If the distance d in FIG. 2 is set to 5 mm or less, the effect of suppressing the image distortion is further enhanced. in this way,
The reason why the provision of the conductive member 14 has the effect of suppressing the image disturbance is as follows. That is, when the transfer paper is separated from the transfer belt 10, the transfer paper and the transfer belt 1
As described above, when the gap between the gap and 0 increases, the potential of the gap sharply rises due to the electric charge of the transfer paper as the gap increases, and peeling discharge occurs.

The above-mentioned image disturbance occurs due to the electric discharge at that time. However, if the conductive member 14 is provided in the vicinity of the separation position of the transfer paper, a new gap is created between the conductive member 14 and the transfer paper. Since such a large electric field is generated, it is possible to suppress a rapid potential change between the gaps when the transfer paper is separated from the transfer belt 10 described above, and thus it is possible to prevent image disturbance.

According to this embodiment, the image disturbance is such that the resistance of the transfer paper becomes high, for example, in the case of a copying machine, when the double-sided or composite copying mode in which the sheet is once fed through the fixing device and then re-fed is performed. Alternatively, even when a recording medium such as an OHP sheet or a second original drawing sheet is used, or even when it is used in a low humidity environment, image disturbance can be prevented.

FIG. 3 is a schematic view showing an embodiment in which a DC bias having a polarity opposite to that of the toner is applied to a conductive member provided in the vicinity of a separation position where the transfer paper is separated from the transfer belt. Corresponding parts are designated by the same reference numerals.

The transfer paper is charged to the same polarity as the toner on the transfer belt 10 when viewed from the front side by the peeling discharge when the transfer paper is separated from the photosensitive drum 2 (see FIG. 1). However, in this embodiment, when the transfer paper P is separated from the transfer belt 10, a DC bias having a polarity opposite to that of the toner or the transfer paper is applied to the conductive member 14 by the power supply 22 which is an electric field generating means. Therefore, the electric field between the transfer paper and the conductive member 14 is strengthened.

Therefore, it is possible to more effectively prevent the image disturbance when the transfer paper is separated from the transfer belt 10. In this way, if a DC bias having a polarity opposite to that of the toner (minus in this example) is applied to the conductive member 14, image distortion is suppressed even if the distance d is larger than 5 mm, as shown in Table 2. be able to. If the distance d is set to 10 mm or less, the above image disturbance can be effectively prevented.

[0045]

[Table 2]

The method for strengthening the electric field between the transfer paper and the conductive member 14 in order to suppress the image disturbance is not limited to the method of applying a DC bias to the conductive member 14, and other methods are applicable. You may make it perform using an electric field generation means. Table 3 shows the results of experiments conducted to investigate the relationship between the volume resistivity of the guide plate that guides the transfer paper after being separated from the transfer belt and the image disturbance. This experiment was conducted at a distance d = 5 mm with the conductive member 14 grounded.

[0047]

[Table 3]

According to the results of this experiment, the guide member 13 shown in FIG. 2 has a conductive material such as a metal plate or a volume resistivity of 10 ¹² Ωcm rather than an insulating material having a high volume resistivity (electrical resistance). It was found that the one formed by the following medium resistor is more effective against the image distortion.

This is because the material used for the guide member 13 functions so as to obtain the electrode effect similarly to the conductive member 14 provided above the guide member 13. This is because the medium resistance member suppresses the above-mentioned potential increase in the gap when the transfer paper is separated from the transfer belt 10, and suppresses the image disturbance due to the synergistic effect with the conductive member 14.

[0050]

As described above, according to the image forming apparatus of the present invention, the recording medium is separated from the dielectric belt by providing the conductive member without using the discharging means for corona discharge. Since the fluctuation of the electric field near the position can be suppressed, it is possible to prevent the image distortion without generating ozone or the like which has a bad influence on the human body and the environment.

Therefore, the resistance of the recording medium when the sheet is re-fed after passing through the fixing device, when the recording medium such as the OHP sheet or the second original drawing sheet is used, and when the recording medium is used in a low humidity environment, etc. It is possible to suppress the occurrence of image distortion even in a situation in which is high.

Further, the conductive member is grounded, and the distance between the surface of the conductive member facing the belt surface of the linear conveying portion of the dielectric belt and the belt surface of the dielectric belt is set to 5 mm or less . Therefore , the effect of preventing the image distortion becomes great.

Further, when the electric field generating means is connected to the conductive member, the electric field for suppressing the fluctuation of the electric field between the conductive member and the recording medium is strengthened, so that the surface of the conductive member and the belt surface of the dielectric belt. Even if the distance between the sheet and the sheet is 10 mm or less, the image disturbance can be prevented. Therefore, when the distance between the sheet and the recording medium passing therethrough is curled, the transfer paper Although the image surface of may contact the conductive member and cause image rubbing,
It can be prevented.

If the guide member is made of a conductive material or a medium resistance material having a volume resistivity of 10 ¹² Ωcm or less, the recording medium separated from the dielectric belt is made of the conductive material and its material. Due to the synergistic effect of both of the guide members, the electric field fluctuation can be effectively suppressed and the image disturbance can be prevented.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a configuration of a transfer conveyance device and its vicinity in an electrophotographic image forming apparatus according to an embodiment of the present invention.

FIG. 2 is an enlarged configuration diagram showing a main part of the transfer / transport device according to the present invention.

FIG. 3 is a schematic view showing an example in which a DC bias having a polarity opposite to that of the toner is applied to a conductive member provided near a separation position where the transfer paper is separated from the transfer belt.

[Explanation of symbols]

1: Transfer / transport device 2: Photoreceptor (image carrier) 10: Transfer belt (dielectric belt) 10a: linear transport section 11: motor (driving means) 12: Power supply 13: Guide member 14: Conductive member P: Transfer paper (recording medium) 22: Power source (electric field generating means)

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-60-48859 (JP, A) JP-A-6-230682 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G03G 15/16 G03G 15/14

Claims (3)

(57) [Claims] 1. A dielectric belt which is rotatable while electrostatically adsorbing a recording medium, drive means for rotating the dielectric belt, and means for applying an electric charge onto the dielectric belt. A guide member for guiding the recording medium immediately after being separated from the dielectric belt, transferring an image held on an image carrier onto the recording medium, and rotating the dielectric belt to perform the recording. In a transfer / transport device for transporting a medium , a conductive member is provided in the vicinity of a position where the recording medium is separated from the dielectric belt , the conductive member being substantially parallel to a belt surface of a linear transport portion of the dielectric belt . The member is grounded, and the member
Facing the belt surface of the linear transport section of the dielectric belt
The distance between the surface and the belt surface of the dielectric belt is 5
A transfer / transport device characterized by having a size of not more than mm . 2. A recording medium is rotated while being electrostatically adsorbed.
Movable dielectric belt and rotating the dielectric belt
Driving means and means for applying electric charge on the dielectric belt
And a recording medium immediately after being separated from the dielectric belt.
And a guide member inside the image carrier,
Transfer the image onto the recording medium and rotate the dielectric belt.
In a transfer conveyance device that moves the recording medium to convey the recording medium , the recording medium is moved at a position where the recording medium is separated from the dielectric belt.
Approximately flat with the belt surface of the linear conveyor of the dielectric belt in the vicinity.
Provided a conductive member in a row, and connecting the electric field generating means to said conductive member, said belt surface of the linear transport section of the dielectric belt and a surface facing said belt surface of the dielectric belt of the conductive member and A transfer / conveyance device characterized in that the distance between them is 10 mm or less. 3. The transfer / transporting device according to claim 1 , wherein the guide member has a conductor or a volume resistivity of 1 or less.
A transfer / conveyance device, which is formed of a medium resistance element of 0 ¹² Ωcm or less.