JPH08272232A - Image forming device - Google Patents

Abstract

PURPOSE: To provide an image forming device capable of satisfactorily transferring an image even to the transfer side of paper having a recess, as of an envelope whose thickness is uneven. CONSTITUTION: The image forming device comprising a transfer electrifier 5 for transferring a toner image to a transfer material P and a peeling electrifier 6 for peeling the transfer material is equipped with a means for detecting the transfer material P having the same transfer side and an uneven thickness, a mode selection means, such as envelope mode, used for the material P whose thickness is uneven an on-off switching means for the peeling electrifier 6, and a means for turning off the on-off switching means in response to a detection signal or a mode selection signal and for increasing an amount of charges which are applied to the transfer material P by the transfer electrifier 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for transferring a toner image onto a transfer material and fixing it to form an image.

[0002]

2. Description of the Related Art As a prior art for obtaining a stable transferred image with respect to transfer of thick paper, Japanese Patent Application Laid-Open No. Sho 64-64
In JP-A-35583, the paper thickness of a specified paper is checked, a transfer current value corresponding to the paper thickness of the paper is read from a memory, and the transfer current of a transfer transformer is switched to the transfer current value to display an image. An image forming apparatus for transferring is disclosed.

Further, in Japanese Patent Laid-Open No. 59-40674, in order to ensure good transfer regardless of the thickness of the paper, the thickness of the paper to be transferred is detected and the thickness is detected according to the detected thickness. An image forming apparatus has been disclosed in which the current value of a corona discharger for transfer or peeling is changed in order to change the transfer current.

Further, in Japanese Utility Model Laid-Open No. 58-126469, in order to prevent transfer failure due to insufficient electrostatic attraction force that occurs when transferring thick paper, when a thick paper is detected, a separation charger is detected. There is disclosed an image forming apparatus in which the electrostatic attraction force is increased by turning off the switch to increase the amount of charge on the sheet by the transfer charger.

[0005]

The techniques disclosed in the above-mentioned respective publications are to control the transfer current value of the transfer charger at the time of transfer to thick paper, turn off the peeling charger, or transfer current. Although it controls both the value and the peeling charger, however, with regard to the transfer of envelopes and the like, unevenness is likely to occur even if only the transfer current is controlled, and there is unevenness due to the mixture of envelope-like overlapping parts. There is a drawback that a stable transfer image cannot be obtained on such a transfer surface.

This is not so effective even if the amount of electric charge acting on the transfer is simply increased, because the effect of the peeling charger cancels the effect of the transfer and does not act effectively on the transfer.
As a result, there is a drawback that transfer is defective in a concave portion that is originally difficult to transfer, and that it is not effective simply by turning off the peeling charger because a required charge amount for an envelope or thick paper cannot be obtained.

Therefore, an object of the present invention is to provide an image forming apparatus capable of excellent transfer even to a transfer surface having a different thickness and having a recess like an envelope.

[0008]

According to the present invention, an image forming apparatus having a transfer charger for transferring a toner image to a transfer material and a peeling charger for peeling the transfer material has different thicknesses on the same transfer surface. A transfer material detection means or a mode selection means for transfer materials having different thicknesses such as an envelope mode is provided, and the ON / OFF switching means of the peeling charger and the detection signal or mode selection signal are turned on. -OFF
It is characterized in that means for switching the switching means to OFF and means for increasing the amount of charge applied to the transfer material by the transfer charger are provided.

[0009]

In the image forming apparatus of the present invention, the peeling charger is OF
By performing F, it is possible to substantially increase the transfer charge amount applied to the paper in the transfer area, so that transfer is improved to some extent, and at the same time, a bias voltage is applied to the shield of the transfer charger to transfer the transfer material. By switching so that the amount of charge applied to the sheet can be increased, the amount of charge to the sheet side can be further increased, and the amount of charge required for thick paper transfer and thin paper recess transfer can be secured without switching the transfer output current.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described based on an embodiment shown in the drawings.

FIG. 1 shows a main part of an image forming apparatus according to the present invention. The electrostatic latent image formed on the photoreceptor surface 1 becomes a toner visible image by the developing means 2. on the other hand,
The sheet p is sent toward the photoreceptor surface 1 by the sheet conveying means 3 so as to be synchronized with the toner visible image. Then, in the transfer portion 4, the visible toner image is transferred as a transferred image onto the paper p by the action of the electric field having a polarity opposite to that of the toner of the visible toner image by the transfer charger 5. Further, after peeling the sheet p by the action of the electric field having a polarity opposite to that of the transfer electric field in the peeling charger 6, the transfer image is fixed through a fixing device (not shown) to obtain a print image.

According to the present invention, the shield 7 of the transfer charger 5 in the above image forming apparatus is in the grounded state during normal plain paper transfer, but the shield 7 is detected depending on the result of paper size detection during paper transport. When it is judged as "envelope" or when the operator selects the "envelope mode" by pressing the button, the output current supplied from the transfer high-voltage power supply 8a to the transfer charger 5 is switched so as to be increased. Alternatively, by applying a bias voltage to the shield 7 with the output current kept the same, it is possible to switch so that a larger transfer electric field is applied than when transferring the plain paper. For this reason,
Since the transfer charge amount applied to the transfer paper can be increased, transfer can be performed well even on paper having a recess.

For example, in the transfer charger 5 of the type in which transfer is performed by an electric field in which alternating current and direct current are superimposed, in the case of transfer on plain paper, output controlled to a constant voltage of 3.0 kv AC and a constant current of +210 μA DC. Electric discharge is performed, and in this case, the shield 7 of the transfer charger 5 is grounded. On the other hand, when the "envelope" is determined based on the detection result of the paper size as described above, or when the operator selects the "envelope mode", the output current is not changed and the high voltage power source 8a for transfer is used. -300v for shield 7
Switch to apply a bias voltage of -500 V.
At the same time, the peeling high-voltage power supply 8b is switched so as to stop the operation of the peeling charger 6. As a result, it is possible to obtain the amount of electric charge required when transferring to the envelope, and it is possible to transfer without any problem even if there are some recesses in the transfer surface of the envelope.

After the transfer, the operation of the peeling charger 6 is stopped by switching the peeling high-voltage power source 8b, and even if the peeling charger 6 does not function, the peeling action can be achieved by the sufficient rigidity of the envelope. It does not cause any trouble.

The means for detecting the envelope is not limited to the size detection described above, but may be based on image information.

Further, the shield 7 of the transfer charger 5 may be of a type which enables switching between a state via a constant voltage element having a predetermined voltage value and a grounded state. Even in this case, if the transfer charger 5 starts discharging, a self-bias voltage is applied to the shield 7, and the same effect can be obtained.

Next, Table 1 shows the results of confirming the effects obtained by using the image forming apparatus according to the present invention.

[0018]

[Table 1] As is apparent from Table 1, when there is a peeling action in the state where the peeling charger is turned on as in Conventional Example 1, the transfer failure occurrence level is "if the transfer charge amount is switched or not. G3 "is a transfer failure. When the peeling charger of Conventional Example 2 is in the OFF state and there is no peeling action and the transfer charge amount is not switched, the transfer failure occurrence level is “G1.5 to
G2 "is slightly improved as compared with the case where the peeling charger of Conventional Example 1 is turned on, but the transfer is still defective, but the peeling charger is turned off and the transfer charge amount is switched to be applied to the transfer material. The invention of the present application in which the amount of charge is increased is “G0 to
It was confirmed that the transfer rate was improved to the level of "G0.5" and the occurrence of transfer defects was small.

[0019]

The present invention has the following excellent effects.

1) While the peeling charger is turned off,
By switching so that the amount of charge applied to the material to be transferred can be increased, the charge on the transfer paper is increased, so transfer to paper with recesses can be performed well, and the recesses and four corners created by the overlapped portion of the envelope are created. It is possible to obtain a stable transfer image that causes almost no transfer failure even with respect to the bent portion of (1) or waviness in the transfer surface in the packed state.

2) After the transfer, since it is not necessary to receive the action of the peeling charger while being in contact with the photosensitive drum, the image can be transferred without causing a defect. Even in this case, since the DC output voltage of the transfer power supply is low, the high voltage transformer of the transfer power supply is small and the cost of parts can be reduced. Further, since the amount of ozone generated can be suppressed and the distance between the shield and the wire can be reduced, the transfer charger can be downsized.

[Brief description of drawings]

FIG. 1 is a side view of a main part of an image forming apparatus according to an embodiment of the present invention.

[Explanation of symbols]

1: Surface of photoconductor 2: Developing means 3: Paper transport device
4: Transfer unit 5: Transfer charger 6: Peeling charger 7: Shield 8a: High voltage power source for transfer 8b: High voltage power source for peeling band p: Paper

Claims (1)

[Claims] 1. An image forming apparatus having a transfer charging device for transferring a toner image to a transfer material and a peeling charging device for peeling the transfer material, and detecting means for the transfer material having different thicknesses on the same transfer surface, or A mode selecting unit is provided for transfer materials having different thicknesses such as an envelope mode, and the peeling charger is turned on.
An image forming method comprising: an OFF switching unit, and a unit for switching the ON-OFF switching unit to OFF in response to the detection signal or the mode selection signal and increasing the amount of charge applied to the transfer material by the transfer charger. apparatus.