JPH07225518A - Color image forming device - Google Patents

Abstract

PURPOSE:To provide a color image forming device provided with a transfer body using a bias drum capable of making the separating bias of a separating electrifier low in a voltage and small in a current. CONSTITUTION:A function as a first transfer material peeling means is imparted to a clipper 2 and a separating pawl 3 is used as a second transfer material peeling means, to forcibly peel a transfer material 5 from the transfer material body 4'. On the other hand, the bias supply of the low voltage and small current is connected to the separating electrifier 1 and it functions only for preventing irregularities in an image caused by a peeling discharge occurring at the time of peeling the transfer material 5 from the transfer body 4'. Thus, the quantity of generated ozone is made extremely little, a large-sized ozone filter and a large-sized fan for discharging are not required and cost is drastically reduced. Moreover, the separating electrifier 1 and the bias supply can be made smaller in size, the cost is further reduced and a device can be miniaturized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic type or electrostatic recording type image forming apparatus such as a printer or a copying machine, and more particularly to a color for superimposing a visible image of a plurality of colors on the same transfer material. The present invention relates to an image forming apparatus.

[0002]

2. Description of the Related Art In a conventional color image forming apparatus, an electrophotographic system as shown in FIG. 10 is often used. These color image forming apparatuses include developing units 91, 92, 93, 94 containing color developers such as yellow (Y), magenta (M), cyan (C) and black (BK), respectively.
And a developing device 9 for developing the electrostatic latent image formed on the image carrier 6 and carrying the supplied transfer material 5.
An electrostatic latent image written by an optical signal generated by an exposure device 16 having a light source such as a transfer body 4 and a laser for transferring an image on the image carrier 6 to a visible image developed by the developing device 9. An image carrier 6 that carries an image together, a primary charger 7 that charges the surface of the image carrier 6, a cleaner 8 that cleans the developer remaining on the image carrier 6 after the image is transferred to the transfer material 5, The color visible image transferred to the transfer material 5 is roughly configured by a fixing device 10 that fixes the color visible image on the transfer material 5.

As shown in FIG. 11, the transfer body 4 in the above apparatus has a hollow drum casing 41 with a side surface cut out only in the transfer area, and a polyethylene terephthalate (P) is formed in the cutout portion.
ET), polyvinylidene fluoride (PVdF), fluorinated ethylene propylene copolymer (FEP), polycarbonate, polyurethane, etc. Hereinafter, this transfer body 4 will be referred to as a transfer body using a notch drum.

A gripper 2 as a transfer material holding means for holding the transfer material 5 and a means for electrostatically adsorbing the transfer material 5 to the flexible sheet 42 are provided inside and outside the transfer body 4 along the rotation direction thereof. The attraction roller 14, the attraction charger 13 for charging the flexible sheet 42 facing the attraction roller 14, the transfer charger 15 as a means for transferring an image formed on the image carrier 6, A separation charger 1 for separating the transfer material 5 electrostatically attracted to the flexible sheet 42, a separation claw 3 as a transfer material peeling means, a transfer body cleaner 11 for removing the developer adhering to the surface of the transfer body, and The sheet static eliminator 12 for initializing the electric potential of the flexible sheet 42 is arranged.

Next, an image forming process of the color image forming apparatus having the above-mentioned general structure will be described. First, a developing device 91 containing, for example, a yellow (Y) developer, the electrostatic latent image of the first color formed on the image carrier 6 by exposure based on the image signal of the first color from the exposure device 16.
To develop and visualize. In parallel with this process, the transfer body 4
Holds the front end of the supplied transfer material 5 with the gripper 2 or the like, and then rotates the transfer material 5 around the surface of the transfer body. At this time, the transfer material 5 is the suction roller 1
4 and the flexible sheet 42 forming the surface of the transfer body 4, and at the same time, held so as to be in close contact with the surface of the transfer body 4 by the electric charge applied to the back surface of the flexible sheet 42 by the attraction charger 13. .

Subsequently, the transfer material 5 is conveyed by the rotation of the transfer body 4 to an image transfer portion at a position opposite to the image carrier 6, and the image formed on the image carrier 6 is transferred onto the transfer material 4. The image is transferred by the transfer charger 15 that is arranged to face the image carrier 6 with the flexible sheet 42 interposed therebetween. After this, the image carrier 6
The residual developer remaining thereon is removed by the cleaner 8 and the exposure device 16 again forms an electrostatic latent image on the image carrier 6 based on the image signal of the second color. This electrostatic latent image is developed into a visible image by the developing device 92 containing, for example, a magenta (M) developer corresponding to the image signal of the second color. The visible image of the second color is transferred by the transfer charger 15 again to the transfer material 5 on the transfer body 4 onto which the visible image of the first color has been transferred.

Next, for example, as a third color, cyan (C),
The third color and the fourth color visible image are formed on the image carrier 6 by using a developer such as black (BK) as the fourth color, and the transfer material on the transfer body 4 is formed in the same manner as the second color visible image. 5 and transfer.

The transfer material 5 on which the color visible images of the respective colors have been transferred as described above is conveyed by the rotation of the transfer member 4 to the separation charging device 1 which is disposed inside and outside the transfer member 4 so as to face each other. The electrostatic attraction force between the transfer material 5 and the flexible sheet 42 is removed, and the transfer material 5 and the flexible sheet 42 are separated via the separation claw 3 as the transfer material separating means. The separated transfer material 5 is guided to the fixing device 10, and the visible image transferred by the fixing device 10 is fixed. After the transfer material 4 is separated, the transfer material cleaner 11 removes the developer adhering to the surface of the transfer material, the sheet charge-eliminating charger 12 removes the electric charge, and the electric charge is initialized to the next step.

In the color image forming apparatus provided with the transfer body 4 using the cutout drum described above, the separation charging device 1 for discharging the transfer material 5 electrostatically adsorbed to the transfer body 4 to promote separation.
Is the transfer material 5 onto which the toner image has been transferred and the flexible sheet 42.
Is removed to about 0 V, the transfer material 5 is easily peeled from the flexible sheet 42, and image disturbance due to peeling discharge generated at the time of peeling is also prevented. A corona charger that performs non-contact charging so as not to disturb the transferred visible image is used as the separation charging device 1 as the charge applying means, and both the transfer material 5 and the flexible sheet 42 are discharged to about 0V. For this reason, as shown in FIG. 10, AC biases having different phases are applied to the facing corona chargers arranged inside and outside the transfer body 4 from the separate bias power sources 101 and 101 while superimposing some DC components. There is.

As a typical example of the transfer member 4 used in the case of forming a color image by the multiple transfer method, as shown in FIG.
The transfer body 4 using the cutout drum shown in FIG. 1 has been described. However, as shown in FIG. 12, a conductive elastic member 43 such as urethane foam or silicone rubber foam is attached to the conductive drum 41 ′ having no cutout portion. The multiple transfer similar to that of the cutout drum can be performed also by a method of applying a bias to the transfer body 4'having a structure in which the surface is covered with the flexible sheet 42 as described above.

In the transfer body 4'of a conductive drum (hereinafter referred to as a bias drum) having no notch portion, the inside can be simplified as compared with the transfer body 4 having the notch structure described above.
Since the cost can be reduced and the flexible sheet 42 is supported from the inside, deformation and damage of the sheet, which is a problem of the transfer body 4 having the cutout structure, can be reduced.
The bias drum 4'is less likely to cause peeling discharge than the cutout drum 4 for the reason described in detail later. Therefore, a color image forming apparatus using a bias drum is currently receiving attention. The image forming process of the color image forming apparatus using the bias drum is very similar to that of the apparatus using the cutout drum described above.

Of the image forming process of the color image forming apparatus using the bias drum, referring to FIG.
Particularly, the transfer process will be described. Incidentally, of the image forming means shown in the figure, those having the same arrangement and function as those of the color image forming apparatus shown in FIG. Omit it.

First, the transfer material 5 supplied to the transfer body 4 ′ from the conveying path is gripped by the gripper 2 and further between the transfer body 4 ′ and the suction roller 14 by the suction roller 14 which comes into contact with and separates from the transfer body 4 ′. Sandwiched. Drum 4 at the same time
Adsorption and a transfer bias are applied to 1'and the adsorption roller 14, and the transfer material 5 is electrostatically adsorbed and held on the transfer body 4'by the electric charge induced by the adsorption and transfer bias. Then, the transfer material 5 held by the transfer body 4 ′ is conveyed to the image transfer portion by the rotation of the transfer body 4 ′, and the visible image of the first color formed on the image carrier 6 is transferred. Next, when transferring the visible image of the second color, the transfer bias value is changed to correct the potential dropped by the transfer material 5 on the transfer body 4 ′ transferring the visible image of the first color. . Such a correction is similarly performed at the time of transferring the third color and the fourth color, and the visible image formed on the image carrier 6 is transferred onto the transfer material 5 on the transfer body 4 ′ in an overlapping manner. The transfer material 5 that has completed the transfer process is neutralized by the separation charging device 1 as a charge applying means, the electrostatic attraction force between the transfer material 5 and the transfer body 4 is removed, and then the transfer material 5 is separated via the separation claw 3. The transfer material 5 onto which the visible image is transferred is conveyed to the fixing device 10 and fixed by the fixing device 10 to obtain a permanent image.

[0014]

In the color image forming apparatus having the transfer body 4'using the bias drum described above, the transfer material 5 and the flexible sheet are also considered based on the same idea as that of the cutout drum. So that both 42 are discharged to about 0V,
As shown in FIG. 13, the separation bias power supply 102 applies an AC bias in which a DC component approximately equal to the transfer bias applied to the separation charger 1 and the transfer body 4 ′ serving as the counter electrode thereof is superimposed. At this time, the AC bias supplied to the corona charger as the separation charger needs to be corona-discharged in positive and negative polarities in order to converge the potential to about 0 V regardless of the drum shape. A high voltage of 8 to 10 KVpp and a current of several tens to several hundreds μA have been required.

When the separation charger 1 which requires a high voltage and a large current as described above is applied to the transfer body 4'using a bias drum, a large amount of ozone is generated by AC corona discharge, so that ozone is generated. It was necessary to use a large-sized exhaust fan and an expensive ozone filter in order to quickly remove it while removing it. In addition, a huge shield corresponding to the edge distance of the applied bias is required, and in addition to this, a separate bias power supply that covers high voltage and large current,
Since it requires a transformer having a larger capacity than other developing bias power supplies, for example, it is expensive and large.

Therefore, a first object of the present invention is to provide a color image forming apparatus provided with a transfer member using a bias drum, which can extremely suppress the generation of ozone.

A second object of the present invention is to provide a color image forming apparatus provided with a transfer member using a bias drum, which does not require a large fan for discharging ozone and an ozone filter.

A third object of the present invention is to provide a color image forming apparatus provided with a transfer member using a bias drum, which can make the bias power source for the charge applying means inexpensive and compact. .

[0019]

The above object can be achieved by a color image forming apparatus according to the present invention. In summary, the present invention provides a transfer body having a structure in which a conductive elastic layer is provided on a conductive base and the surface of the conductive elastic layer is covered with a flexible sheet,
In a color image forming apparatus having a transfer material holding unit that holds a transfer material on the transfer body, the transfer material holding unit also has a function of peeling the transfer material from the transfer body, and the transfer material holding unit performs a peeling operation. The color image forming apparatus is characterized in that it is provided with a DC electric charge applying unit at a position upstream of the entering position to prevent peeling discharge that occurs when peeling the transfer material from the transfer body.

Preferably, the separation bias of the DC charge applying means is controlled to a constant current of 5 to 20 μA.

Preferably, a means for measuring the length of the transfer material is provided, and the DC charge applying means operates only for a time substantially equal to the time for which the transfer material on which the final image is transferred passes through the transfer material separating point. To do.

It is preferable that a temperature / humidity sensor for detecting temperature / humidity in the main body of the apparatus is provided, and the operation of the DC electric charge imparting means is controlled according to the detected temperature / humidity.

Preferably, the DC charge applying means is a corona charger.

Preferably, the means for applying DC electric charge is a charge elimination needle.

[0025]

Embodiments of the color image forming apparatus according to the present invention will be described below in more detail with reference to the drawings. In the description of the embodiments, members that are the same as or similar to the members of the color image forming apparatus shown in the above-described conventional example have the same reference numerals and detailed description thereof will be omitted. Further, only the characteristic part of the present invention will be described.

Embodiment 1 FIG. 1 is a schematic structural view of a color image forming apparatus embodying the present invention, which is equipped with a transfer body 4'using a bias drum.

In the figure, the separation charger 1 as a DC charge applying means for preventing separation discharge that occurs when the transfer material 5 is separated from the transfer body 4'is a corona charger, and is separated from the separation claw 3 similarly to the conventional example. The transfer member 4 ′ is arranged at a position substantially equal to the transfer material separation point on the upstream side in the rotation direction, and is connected to the DC separation bias power source 103.

Further, as shown in FIG.
Serves as a transfer material holding means and a first transfer material peeling means, and mechanically peels the tip of the transfer material 5 from the transfer body 4 as shown by a broken line with the rotation axis 2a as a fulcrum.
The transfer material 5 is forcibly separated from the leading end portion where the separation claw 3 as the second transfer material separating means is separated, as a starting point.

As described above, in this embodiment, the transfer material is forcibly separated from the transfer body by the gripper 2 and the separation claw 3,
It is characterized in that the separation assisting action of the conventional separation charging device is unnecessary and the separation charging device is operated only for preventing the peeling discharge.

Next, the operation of separating the transfer material from the transfer body will be described. The transfer material 5 to which the toner image of the final color has been transferred is conveyed to the transfer material separation point by the rotation of the transfer body 4 ′, and the tip of the transfer material 5 is released by the gripper 2 holding the transfer material 5 at the transfer material separation point. The separation claws 3 are lifted up and downwardly of the transfer material 5 which is lifted up.
Is inserted. Further, when the transfer body 4'is rotated, the transfer material is completely separated from the transfer body 4 '.

The separation charger 1 is several hundreds ms from the time T _{1 when} the tip of the transfer material 5 is flipped up by the gripper 2.
It operates at a time T _{0 a} few seconds earlier, forms a positive discharge atmosphere to prevent peeling discharge near the separation portion of the transfer material 5 to be separated, and at least until the transfer material 5 on the transfer body 4 ′ is completely separated. Operates for hours. As a result, it is possible to prevent image scattering due to peeling discharge, that is, image disturbance.

As described above, the separation bias used in this embodiment has only to have a magnitude capable of preventing peeling discharge, and a DC voltage of approximately 3.5 K to 4.0 KV and a current value of 5 to the total current. The current value can be about 20 μA.
As a result, the size of the separation charger 1 can be made smaller than that of the conventional separation charger.

In the present embodiment, a bias drum that causes less peeling discharge when peeling the transfer material 5 is used. The reason why the bias drum causes less peeling discharge than the notch drum is described below with reference to FIGS. It will be described with reference to FIG.

FIG. 3 is a schematic diagram modeling the charges on the cutout drum, and FIG. 4 is a schematic diagram modeling the charges on the bias drum. 3 and 4,
Rps and Rpv are the surface resistance and the volume resistance of the transfer material 5, respectively. Further, Cp, Cair, and Cpvdf are electrostatic capacities of the transfer material 5, the air gap, and PVdF as the flexible sheet 42, respectively, and Rpvdf in FIG. 3 is P.
It is the surface resistance of the VdF sheet. 3 and 4 are charge models during adsorption, which are charge densities Q accumulated during transfer or adsorption.
The electric charge of ₀ is evenly distributed on the surface of the transfer material and the back surface of PVdF. At this time, the potential difference between AB and CD in FIG. 3 and the potential difference between EF and GH in FIG. 4 are both 0V.

Schematic diagrams of the case where the transfer material 5 is separated from such a state are shown in FIGS. 5 and 6, respectively. In FIGS. 5 and 6, the capacitance of one air gap changes from Cair to Cair1 due to the separation. It is considered that when the air gap changes in this way, the movement of the charge differs between the notch drum and the bias drum, and the difference appears as a difference in the peeling discharge.

First, the movement of electric charges in the cutout drum will be described with reference to FIG. 5. The capacitance of the air gap is Cai.
As a result of reduction from r to Cair1, the above AB, C
The potential difference between D spreads. This potential difference is
This can be solved by moving the charges on the back surface of the dF, but since the surface resistance of PVdF is as high as 10 ¹³ to 10 ¹⁶ Ω / □, the movement of each of the charges is restricted, and a current that eliminates the above potential difference does not occur. That is, since the resistance of Rpvdf is too large, it is considered that AB and CD are actually almost independent. Therefore, when changing from Cair to Cair1, the potential difference increases from Vair0 to Vair1. The potential difference Vair1 of the air gap exhibits almost the same behavior as when the interelectrode distance of the capacitor having the charge density Q0 stored on its surface changes to the distance d1. The potential difference Vair1 of the air gap when the air gap becomes D1 becomes Vair1 = Q0 × d1 / ε0 (1), and when this voltage exceeds the discharge start voltage, peeling discharge occurs. Here, ε0 is the dielectric constant of vacuum.

Since the discharge start voltage follows Paschen's law and depends only on the distance between the electrodes under this condition, the relationship between the potential difference Vair1 and the air gap distance d1 obtained from the above equation (1) is Paschen's law. When the above condition is satisfied, peeling discharge occurs. The graph of FIG. 7 shows the potential difference Vair1 with respect to the change in the air gap d1 and the discharge start voltage according to the Paschen's law at the air gap d1 in the equation (1).

In the graph of FIG. 7, the transfer member 5 up to the air gap at the intersection (a) between the Paschen's law and the equation (1).
When is peeled off, peeling discharge occurs between the front surface of the transfer body 4 and the back surface of the transfer material 5.

By the way, in the equation (1), the inclination of the increase is changed according to the magnitude of the charge density Q0 stored before the peeling. For example, process speed 106 mm / sec,
When a current of about 5 μA flows into the above system when the transfer body 4 having a length of 210 mm is used, as a charge density Q0, a charge of about 2.25E-4C / m ² is stored. The discharge start distance is about 17 μm. However, when the charge density Q0 decreases to Q1, Q2, Q3, and Q4, the inclination becomes small as shown by the dotted line in the figure, and the intersection with the Paschen's curve also moves.

When the charge density Q0 stored in the air gap at the intersection point a is reduced to Q1 by the peeling discharge, the system state transits from the straight line of Q0 to the straight line of Q1, and the transfer material 5 is peeled off. Will discharge at the next intersection b. When such a transition is repeated and the surface charge is reduced to Q4, peeling discharge does not occur in the air gap. The above is the mechanism of peeling discharge in the notch drum.

Next, the movement of charges on the bias drum will be described with reference to FIG. Even with the bias drum, the capacitance Cair of the air gap decreases to Cair2 with the peeling, and the potential difference between EF and GH also increases. However,
Unlike cutout drums, bias drums have PVd
Since the electric charge on the back surface of F can freely move in the conductive elastic member 43 in contact with the back surface of PVdF, a surface current i ₁ that tries to cancel the potential difference between EF and GH is generated in the transfer material and is stored in the air gap. The amount of charge Q0 is reduced. That is, in the bias drum, the charge accumulated in the air gap decreases due to the generation of the surface current i ₁ .
It is considered that the surface charge at the time of peeling is reduced to the value of Q3 or Q4, for example. Therefore, in the bias drum, the number of discharges at the time of peeling is extremely smaller than that in the notch drum, and it is considered that there is a difference in image scattering due to peeling discharge.

As can be inferred from the above description, the peeling discharge of the notch drum is caused by the surface resistance Rpvdf of the back surface of PVdF.
The surface resistance Rps of the transfer material is controlled by that of the bias drum. Therefore, the resistance value of PVdF hardly changes even when the environment changes.
The peeling discharge in the notch drum occurs even in a high humidity state as compared with the bias drum, and, for example, the volume resistance Rpv of the transfer material decreases to about 10 ⁵ to 10 ⁶ Ω, and the decay current i in the transfer material i. _The peeling discharge occurs until ₂ becomes extremely large. On the other hand, in the bias drum, since it is governed by the resistance value Rps of the transfer material 5, the volume resistance 10 ¹⁰ to 10 ¹⁵ Ω stored for a long time in a low temperature and low humidity state.
Only for a transfer material of a certain degree, it is difficult for the charge to decrease due to the surface current i _{1 and the} image is scattered due to the peeling discharge.

Therefore, in the notch drum, peeling discharge cannot be prevented unless the charges on the back surface of the flexible sheet and the surface of the transfer material are both erased before separation except in a high humidity environment or below. The peeling discharge can be prevented by applying the electric charge corresponding to the above current i ₁ only to the high-resistance transfer material below.

In the present embodiment, the bias of the separation charger is positive, but any polarity may be used as long as it prevents peeling discharge. For example, when positive toner is used, it has a negative polarity. However, when the corona discharge of the negative electrode is used as the separation bias, the amount of ozone generated at the same voltage is larger than that when the positive electrode is used. Therefore, in this case, it is desirable to set the bias value to be small.

In the color image forming apparatus of the present embodiment, the separation and the transfer material and the wire were set to about 5 mm with a separation bias of 3.75 KV and 7 μA, and UL4 was used.
When ozone was measured according to the 78-5th standard,
It was confirmed that the concentration was 0.1 ppm / 8 hours or less, which was a low concentration with little influence on the human body.

The separating charger may be operated at least during the time when the transfer material is separated. Further, a means for measuring the length of the transfer material is installed in the main body of the apparatus, and the means is interlocked with the means. By changing the operating time of the separation charger, the ozone generation amount can be reduced and it is more effective.

As described above, the transfer member provided with the bias drum with less peeling discharge is adopted, and the gripper as the transfer material holding means also serves as the first transfer material peeling means, whereby the transfer material is first transferred. The transfer material is forcibly peeled from the body, and the transfer material is separated from the transfer body by the separation claw serving as the second transfer material peeling means. At the same time, in order to prevent image disturbance due to peeling discharge caused by peeling at this time, a minute DC bias is applied by the separation charger.

As described above, in this embodiment, since only a minute DC bias is applied, a huge shield against the applied bias is not required as in the conventional case, and the amount of ozone generated is reduced to the extent that it does not affect the human body. Therefore, it is possible to eliminate the need for an ozone filter and a large fan for discharging ozone, and it is possible to reduce the cost. Further, even when the corona charger is used as the charge applying means, the discharge is performed in the vicinity of the corona discharge starting voltage (about 3.5 KV), so that the bias power source and the corona charger can be made smaller than when the AC corona is used. It is possible to reduce the cost and downsize the device.

Second Embodiment Next, a second embodiment of the color image forming apparatus according to the present invention will be described with reference to FIG. The present embodiment is characterized in that a charge eliminating needle 1'is applied as the charge applying means.

The charge elimination needle 1'is arranged at the same position as the separation charger 1 (FIG. 2) of the first embodiment. Static elimination needle 1 '
The needle end of is directed to the surface of the transfer material 5 which is separated at the transfer material separation point.

By using this structure, there is an advantage that the structure becomes simpler and the cost of the main body can be reduced as compared with the case of using the corona charger as in the first embodiment.

In the first and second embodiments, the corona charger and the discharging needle are used as the charge applying means, but it goes without saying that other known non-contact charging means may be used.

Third Embodiment Next, a third embodiment will be described with reference to the block diagram of FIG. In this embodiment, a temperature / humidity sensor is provided in the main body of the apparatus, and the temperature / humidity obtained by the temperature / humidity sensor is judged by the main body CPU. For example, the separation charger is not operated in a high temperature and high humidity environment where peeling discharge is unlikely to occur. It is characterized by using a sequence.

In the block diagram of FIG. 9, first, the power of the apparatus main body is turned on, and the temperature and humidity are detected by the temperature and humidity sensor installed in the apparatus main body. Next, the main body CPU calculates the absolute water content based on the detection result of the temperature and humidity.
According to the calculation result, it is determined whether or not the amount of water causes peeling discharge. Then, when it is determined that the amount of water that causes peeling discharge, an image forming sequence for operating the DC corona charger is performed. On the other hand, when it is determined that the amount of water that causes peeling discharge is not, an image forming sequence in which the DC corona charger is not operated is performed.

As described above, in the present embodiment, the separation charger does not need to be used under the environment where the separation charger is unnecessary.
There is an advantage that unnecessary ozone is not generated. In addition, it is possible to prevent a problem in which separation charging is transmitted to the transfer material whose resistance value has decreased under high temperature and high humidity, and the action of the transfer bias is hindered.

[0056]

As is apparent from the above description, in the color image forming apparatus according to the present invention, the transfer material holding means also has a function as a transfer material peeling means for peeling the transfer material from the transfer body. Separation of the DC charge imparting means by having a configuration in which the material holding means is provided with a DC charge imparting means for preventing a peeling discharge that occurs when the transfer material is peeled from the transfer body, at a position upstream of the position where the material holding means enters the peeling operation. The bias can be a low voltage and a small current, and the amount of ozone generated can be extremely suppressed. As a result, the ozone filter and the large-sized fan, which have been conventionally required, can be dispensed with, and it is possible to contribute to a large cost reduction and downsizing of the apparatus. Further, the charge applying means and the bias power source can be made small, so that cost reduction and device miniaturization can be achieved.

Further, by adopting the charge elimination needle as the charge applying means, the apparatus can be further simplified and the cost of the main body can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a first embodiment of a color image forming apparatus according to the present invention.

FIG. 2 is an explanatory view showing a peeling operation of the gripper shown in FIG.

FIG. 3 is a schematic diagram modeling a charge in a notch drum.

FIG. 4 is a schematic diagram modeling a charge on a bias drum.

FIG. 5 is a schematic diagram modeling a charge in a cutout drum when a transfer material is separated.

FIG. 6 is a schematic diagram modeling the charge on the bias drum when the transfer material is separated.

FIG. 7 is a graph showing the relationship between air gap and voltage in relation to Paschen's law.

FIG. 8 is an explanatory view of a second embodiment showing a charge eliminating needle as a charge giving means.

FIG. 9 is a block diagram showing control of a DC corona in the third embodiment.

FIG. 10 is an overall configuration diagram showing a conventional color image forming apparatus provided with a cutout drum.

FIG. 11 is a perspective view showing a cutout drum.

FIG. 12 is a perspective view showing a bias drum.

FIG. 13 is an overall configuration diagram showing a conventional color image forming apparatus including a bias drum.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Separation charger (charge giving means) 1'Electrification removing needle (charge giving means) 2 Gripper (transfer material holding means / first transfer material peeling means) 3 Separation claw (second transfer material peeling means) 4'Transfer body 5 Transfer material

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical display location H01T 19/04 7522-5G H05F 3/04 D 9470-5G (72) Inventor Nobuaki Kaburaya Ota, Tokyo 3-30-30, Shimomaruko, Tokyo Canon Inc. (72) Takao Kume 3-30-2, Shimomaruko, Ota-ku, Tokyo Metropolitan area (72) Incorporator, Canon Takehiko Suzuki 3-chome, Shimomaruko, Ota-ku, Tokyo No. 30-2 Canon Inc. (72) Inventor Moto Kato 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (6)

[Claims] 1. A transfer body having a structure in which a conductive elastic layer is provided on a conductive base and the surface of the conductive elastic layer is covered with a flexible sheet, and a transfer material holding means for holding a transfer material on the transfer body. In the color image forming apparatus having the above, the transfer material holding means also has a function as a transfer material peeling means for peeling the transfer material from the transfer body, and the position upstream of the position where the transfer material holding means enters the peeling operation. 2. A color image forming apparatus, further comprising direct current charge applying means for preventing peeling discharge that occurs when peeling the transfer material from the transfer body. 2. The color image forming apparatus according to claim 1, wherein the separation bias of the DC charge imparting means is controlled to a constant current of 5 to 20 μA. 3. A means for measuring the length of the transfer material is provided,
3. The color image forming apparatus according to claim 1, wherein the DC charge applying means operates only for a time substantially equal to a time for which the transfer material on which the final image is transferred passes through the transfer material separating point. 4. A temperature / humidity sensor for detecting temperature / humidity in the main body of the apparatus, and controlling the operation of the DC electric charge applying means according to the detected temperature / humidity.
1 to 3, a color image forming apparatus. 5. The color image forming apparatus as claimed in claim 1, wherein the DC charge applying means is a corona charger. 6. The color image forming apparatus as claimed in claim 1, wherein the DC charge applying means is a charge eliminating needle.