KR100477689B1 - Liquid photo-electronic image forming apparatus and sencondary transfering method - Google Patents

Abstract

The present invention discloses a wet electrophotographic image forming apparatus and a secondary transfer method. The disclosed wet electrophotographic image forming apparatus includes: a separation means for separating and contacting the secondary transfer roller from the transfer belt; A first PWM unit which applies a bias voltage to the secondary transfer roller; A first enable unit for activating the first PWM unit; A second PWM unit applying a bias voltage to the secondary transfer backup roller; A second enable unit for activating the second PWM unit; A control unit controlling the first and second enable units; And a switching unit configured to connect the selected one of the control unit among the first PWM unit and the second PWM unit to a corresponding secondary transfer roller or a secondary transfer backup roller. According to this, the liquid toner on the transfer belt can be prevented from contaminating the surface of the secondary transfer roller and thus the print quality can be improved.

Description

Liquid photo-electronic image forming apparatus and sencondary transfering method

The present invention relates to a wet electrophotographic image forming apparatus and a secondary transfer method, and more particularly, when a toner image is transferred from a transfer belt to a secondary transfer roller, contamination of the secondary transfer roller by the wet carrier from the transfer belt. The present invention relates to a secondary transfer system and a secondary transfer method that prevent the paper from being contaminated.

1 is a diagram schematically illustrating a configuration of a general wet color image forming apparatus.

Referring to FIG. 1, a plurality of image forming units are arranged in series on a circulation path of a transfer belt 40 that circulates an endless track by a plurality of rollers 41, 42, 44. Each of the image developing units transfers the cyan (C), magenta (M), yellow (Y) and black (K) images to the transfer belt, respectively.

Each of the image forming units includes a photosensitive drum 30 for transferring a toner image of a predetermined color to the transfer belt 40, a charger 36 for charging the surface of the photosensitive drum 30 to a predetermined electric potential, and A laser scanning unit 38 for irradiating light to the surface of the photosensitive drum 30 to form an electrostatic latent image, a developing unit 10 for developing the electrostatic latent image to a predetermined toner image, and a developed toner And a cleaning blade 32 for transferring the image onto the transfer belt 40 and removing the toner image on the photosensitive drum 30 remaining. Reference numeral 34 denotes a static eliminator that erases the charge on the photosensitive drum 30.

The developing unit 10 is installed so as to be partially immersed in the developer stored in the developing container 14 to apply the developer on the surface thereof to develop the electrostatic latent image formed on the photosensitive drum 30 in a predetermined color.

The transfer belt 40 is supported by a plurality of primary transfer backup rollers 42 corresponding to the driving roller 41, the secondary transfer backup roller 44, and the photosensitive drum 30, and rotates in the respective colors. The image formed on the photosensitive drum 30 is transferred to be superimposed. A secondary transfer roller 43 is provided opposite the secondary transfer backup roller 44 with the transfer belt 40 interposed therebetween to transfer the image of the transfer belt 40 to the paper 60 again. .

The paper 60 to which the color image is transferred by the secondary transfer roller 43 is heated and pressed to a predetermined temperature by the fixing device 50 installed on the paper discharge path, and the toner image is fused to the paper 60. do.

Downstream of the secondary transfer roller 43, there is provided a cleaning blade 49 for removing the toner remaining after the secondary transfer.

FIG. 2 is a diagram illustrating a voltage application system for secondary transfer of the wet color image forming apparatus having the configuration of FIG. 1.

Referring to FIG. 2, the secondary transfer roller 43 has a toner image on the transfer belt 40 in the transfer process on the paper 60 drawn between the secondary transfer backup roller 44 and the secondary transfer roller 43. A pulse width modulation section (PWM section) 70 for applying a bias voltage opposite to the toner image is connected for transfer. The PWM unit 70 is connected in series with an Engage ON / OFF unit 80 for activating the PWM unit 70 and a controller 90 for controlling the Engage ON / OFF unit 80. When the Engage ON / OFF unit 80 is turned on by receiving the signal from the controller 90, when the PWM unit 70 is applied to the secondary transfer roller 43, a reverse bias voltage is applied to the secondary transfer roller. The secondary transfer roller 43 is cleaned. In addition, the Engage ON / OFF unit 80 is turned off by receiving a signal from the control unit 90, and when the PWM unit 70 is applied to the secondary transfer roller 43, the secondary transfer roller 43 is positive. A bias voltage is applied to transfer the toner image on the transfer belt 40 to the paper 60. For example, when the toner has a positive charge, the controller 90 turns off the PWM unit 70 to apply a negative voltage to the secondary transfer roller. When the secondary transfer roller 43 does not perform the transfer operation, that is, when idling, the control unit 90 to prevent the toner on the transfer belt 40 from adhering to the surface of the secondary transfer roller 43. ) Turns off the PWM unit 70 to apply the reverse bias voltage, that is, a positive voltage equal to the toner, to the secondary transfer roller 43.

However, in the conventional transfer method as described above, since the secondary transfer roller 43 is always in contact with the transfer belt 40, the liquid toner contaminates the secondary transfer roller 43 in the state where no paper is inserted, thereby printing the image. It does not fundamentally prevent contamination of paper edges and backs. As shown in FIG. 3, in the process of exchanging the positive bias voltage and the reverse bias voltage with one PWM unit 70, the applied voltage is lower than the desired voltage (solid line display). The constant voltage application control becomes unstable, and thus there is a problem that the image quality is poor.

In addition, since the secondary transfer roller 43 is always in contact with the transfer belt 40 and rotates, there is a problem that the load (load) is increased on the transfer belt 40 and the secondary transfer roller 43.

SUMMARY OF THE INVENTION The present invention has been made to improve the above-mentioned problems of the prior art, and provides a wet electrophotographic image forming apparatus and a secondary transfer method of improving print quality by preventing a secondary transfer roller from contamination from a liquid toner.

In order to achieve the above object, the wet electrophotographic image forming apparatus includes a photosensitive member, a developing roller for supplying toner to an electrostatic latent image formed on the photosensitive member, a transfer belt to which the toner image on the photosensitive member is transferred, and the transfer member. A wet image forming apparatus comprising a secondary transfer roller for transferring a toner image on a belt to paper,

A separation means for separating and contacting the secondary transfer roller from the transfer belt;

A first PWM unit which applies a bias voltage to the secondary transfer roller;

A first enable unit for activating the first PWM unit;

A second PWM unit applying a bias voltage to the secondary transfer backup roller;

A second enable unit for activating the second PWM unit;

A control unit controlling the first and second enable units; And

And a switching unit configured to connect the selected one of the control unit among the first PWM unit and the second PWM unit to the secondary transfer roller or the secondary transfer backup roller.

The separation means,

A connecting member connecting the shafts protruding from both ends of the secondary transfer roller in a direction opposite to the transfer belt; And

And a cam member for reciprocating the connecting member in the direction of the transfer belt.

 In addition, the detection means for detecting that the secondary transfer roller is spaced apart from the transfer belt, it is preferable to further include a proximity sensor for detecting the object to be wound on the shaft of the secondary transfer roller.

In order to achieve the above object, the secondary transfer method of the wet electrophotographic image forming apparatus includes a photosensitive member, a developing roller for supplying toner to an electrostatic latent image formed on the photosensitive member, and a transfer to which the toner image on the photosensitive member is transferred. A wet image forming apparatus comprising a belt and a secondary transfer roller for transferring a toner image on the transfer belt to a paper,

A separation means for separating and contacting the secondary transfer roller from the transfer belt;

A first PWM unit which applies a bias voltage to the secondary transfer roller;

A first enable unit for activating the first WPM unit;

A second PWM unit applying a bias voltage to the secondary transfer backup roller;

A second enable unit for activating the second PWM unit;

A control unit controlling the first and second enable units; And

In the secondary transfer method of the wet image forming apparatus comprising: a switching unit for connecting the selected from the first PWM unit and the second PWM unit to the secondary transfer roller or the secondary transfer backup roller;

(a) receiving a printing command from the control unit and bringing the secondary transfer roller into contact with the transfer belt;

(b) applying a bias voltage to the secondary transfer backup roller;

(c) detecting a sheet entering the secondary transfer roller and applying a bias voltage to the secondary transfer roller;

and (d) applying a bias voltage to the secondary transfer backup roller when the paper leaves the transfer nip of the secondary transfer roller.

The step (a) may include (a1) determining whether the secondary transfer roller is in contact with the transfer belt by a proximity sensor; And

(a2) if it is determined that the secondary transfer roller is spaced apart from the transfer belt, contacting the secondary transfer roller with the transfer belt by the separation means.

Hereinafter, a wet electrophotographic image forming apparatus and a second transfer method according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. In this process, the thicknesses of layers or regions illustrated in the drawings are exaggerated for clarity.

4 schematically shows the configuration of the secondary transfer system of the wet electrophotographic image forming apparatus according to the preferred embodiment of the present invention, and the same reference numerals are used for objects having the same structure as the conventional invention, and detailed description thereof will be omitted. .

Referring to FIG. 4, the secondary transfer control system includes a first PWM unit 121 for applying a positive bias voltage having a predetermined magnitude to the secondary transfer roller 43 and a predetermined size to the secondary transfer backup roller 44. A second PWM unit 122 for applying a bias voltage of the first enable unit 111 and a second enable unit 112 for activating the first PWM unit 121 and the second PWM unit 122, respectively. And a voltage from the control unit 100 controlling the first and second enable units 112 and the first PWM unit 121 or the second PWM unit 122 selected by the control unit 100. And a switching unit 130 connected to the vehicle transfer roller 43 or the secondary transfer backup roller 44.

For example, when the toner has a positive charge, the control unit 100 turns on the first enable unit 111 to select the first PWM unit 121 to switch to the secondary transfer roller 43 through the switching unit 130. A toner image of the transfer belt 40 is transferred to the paper 60 drawn between the transfer belt 40 and the secondary transfer roller 43 by applying a voltage, for example, a −2 kV voltage.

On the other hand, the controller 100 turns on the second enable unit 112 to select the second PWM unit 122 and through the switching unit 130 to the secondary transfer backup roller 44-voltage, for example -2 kV voltage Is applied to suppress the contamination of the surface of the secondary transfer roller 43 by the liquid toner of the transfer belt 40. This prevents the problem that the back surface of the paper 60 to be printed is contaminated due to contamination of the surface of the secondary transfer roller 43.

As such, the conventional PWM unit (70 in FIG. 2) is separately installed as the first 121 and the second PWM units 122, respectively, so that the secondary transfer rollers 43 and the secondary transfer backup rollers 44 are different from each other. Applying a voltage having a property has an effect of preventing attenuation of an applied voltage generated by switching a potential in one PWM unit 70. That is, since the desired applied voltage is applied to the secondary transfer roller 43 or the secondary transfer backup roller 44, the printing quality can be determined.

5 is a view schematically showing an example of the separation means for separating and contacting the secondary transfer roller 43 from the transfer belt 40.

Referring to the drawings, the connecting member 141 which extends in the opposite direction of the transfer belt 40 at both ends of the shaft 140 of the secondary transfer roller 43 and is connected, and both ends of the shaft 140 are image-formed. A spring 143 connected to the body of the device is arranged. The connecting member 141 includes a cam member 142 for converting the rotational movement of the driving unit by the driving unit (not shown) into the reciprocating linear motion of the connecting member 141 and the secondary transfer roller 43 to the transfer belt 40. It is installed. And the shaft 140 is installed around the circumference of one side, a predetermined member, for example a metal cylinder 145, and the secondary transfer roller 43 is in contact with the transfer belt 40 in the state in which the cylinder 145 The proximity sensor 146 which detects is installed.

When the long axis of the cam member 142 contacts the connecting member 141, the secondary transfer roller 43 is brought into contact with the transfer belt 40. When the cam member 142 is rotated, the cam member 142 is rotated. The long axis of the shaft 140 and the secondary transfer roller 43 is moved away from the transfer belt 40 by the restoring force of the spring 143 as the deviation from the connecting member 141. Through the proximity sensor 146, it is possible to detect whether the secondary transfer roller 43 is spaced apart from the transfer belt 40.

The secondary transfer process of the wet electrophotographic image forming apparatus having the above-described configuration will be described in detail with reference to the drawings.

6 is a timing diagram of the secondary transfer process of the wet electrophotographic image forming apparatus according to the preferred embodiment of the present invention.

First, when a print command is started from the control unit 100 (t1), the control unit 100 turns on the second enable unit 112 so that the second PWM unit 122 may switch the secondary transfer rollers through the switching unit 130. 43, a bias voltage is applied to the secondary transfer backup roller 44 so that the toner is rejected from the secondary transfer roller 43. Then, the cam member 142 is operated just before the paper 60 enters between the secondary transfer backup roller 44 and the secondary transfer roller 43 (t2) so that the long axis of the cam member 142 is connected to the connecting member ( 141 to contact the connecting member 141 and the secondary transfer roller 43 to the transfer belt 40. Subsequently, when the printing paper 60 enters between the secondary transfer nips (t3) or after the paper 60 has passed through the leading end (about 2-3 mm) (t4), the second enable part 112 is turned off and 1 The toner image on the transfer belt 40 is turned on by applying a bias voltage to the second transfer roller 43 from the first PWM unit 121 through the switching unit 130 by turning on the enable unit 111. To be transferred to the image.

Next, when the printing paper 60 leaves the secondary transfer nip (t6) or preferably immediately before the paper 60 exits the secondary transfer nip (t5), for example, the rear end portion of the paper 60 (paper ( 60) at the end of the transfer transfer nip, the bias transfer voltage is turned on to the secondary transfer backup roller 44 and the bias voltage to the secondary transfer roller 43 is turned off. 43) to prevent contamination.

Subsequently, when continuous printing is performed on another paper 60, when the paper 60 enters the secondary transfer nip (t7) or after the leading end of the paper 60 passes the transfer nip (t8) as described above. The secondary transfer is performed by turning off the bias voltage of the secondary transfer backup roller 44 and turning on the bias voltage of the secondary transfer roller 43.

When no further printing is performed when the paper 60 leaves the transfer nip (t9), a cam member which directly supports the connecting member 141 of the secondary transfer roller 43 in the direction of the transfer belt 40 ( The secondary transfer roller 43 is spaced apart from the transfer belt 40 by rotating 142 (t10).

On the other hand, the driving of the cam member 142 is preferably driven according to a signal for determining whether the secondary transfer roller 43 from the proximity sensor 146 is in contact with the transfer belt 40.

As described above, it is possible to prevent the liquid toner on the transfer belt from contaminating the surface of the secondary transfer roller by the image forming apparatus and the secondary transfer method according to the present invention, thereby improving print quality.

Although the present invention has been described with reference to the embodiments with reference to the drawings, this is merely exemplary, it will be understood by those skilled in the art that various modifications and equivalent embodiments are possible. Therefore, the true technical protection scope of the present invention will be defined only by the appended claims.

1 is a diagram schematically illustrating a configuration of a general wet color image forming apparatus.

FIG. 2 is a schematic diagram of a voltage application system for secondary transfer of the wet color image forming apparatus having the configuration of FIG. 1.

FIG. 3 is a diagram illustrating that an applied voltage is displayed as a dotted line lower than a desired voltage (solid line display) in the process of exchanging and applying a positive bias voltage and a reverse bias voltage to one PWM unit 70.

4 is a view schematically showing the configuration of the secondary transfer system of the wet electrophotographic image forming apparatus according to the preferred embodiment of the present invention.

5 is a view schematically showing an example of the separation means for separating and contacting the secondary transfer roller from the transfer belt.

6 is a timing diagram of the secondary transfer process of the wet electrophotographic image forming apparatus according to the preferred embodiment of the present invention.

* Description of Signs of Major Parts of Drawings *

40: transfer belt 43: secondary transfer roller

44: secondary transfer backup roller 60: paper

100: control unit 111: first enable unit

112: second enable part 121: first PWM part

122: second PWM unit 130: switching unit

140: shaft of the secondary transfer roller 141: connecting member

142: cam member 143: spring

145: cylinder 146: proximity sensor

Claims (7)

A wet image comprising a photosensitive member, a developing roller for supplying toner to an electrostatic latent image formed on the photosensitive member, a transfer belt for transferring the toner image on the photosensitive member, and a secondary transfer roller for transferring the toner image on the transfer belt to paper. In the forming apparatus, A separation means for separating and contacting the secondary transfer roller from the transfer belt; A first PWM unit which applies a bias voltage to the secondary transfer roller; A first enable unit for activating the first PWM unit; A second PWM unit applying a bias voltage to the secondary transfer backup roller; A second enable unit for activating the second PWM unit; A control unit controlling the first and second enable units; And And a switching unit configured to connect the selected one of the first PWM unit and the second PWM unit to the controller to the corresponding secondary transfer roller or the secondary transfer backup roller. The method of claim 1, The separation means, A connecting member connecting the shafts protruding from both ends of the secondary transfer roller in a direction opposite to the transfer belt; And And a cam member for reciprocating the connecting member in the direction of the transfer belt. The method of claim 1, And a detecting means for detecting that the secondary transfer roller is spaced apart from the transfer belt. The method of claim 3, wherein The detection means, And a proximity sensor for sensing the object to be wound on the shaft of the secondary transfer roller. A wet image comprising a photosensitive member, a developing roller for supplying toner to an electrostatic latent image formed on the photosensitive member, a transfer belt for transferring the toner image on the photosensitive member, and a secondary transfer roller for transferring the toner image on the transfer belt to paper. In the forming apparatus, A separation means for separating and contacting the secondary transfer roller from the transfer belt; A first PWM unit which applies a bias voltage to the secondary transfer roller; A first enable unit for activating the first PWM unit; A second PWM unit applying a bias voltage to the secondary transfer backup roller; A second enable unit for activating the second PWM unit; A control unit controlling the first and second enable units; In the secondary transfer method of the wet image forming apparatus comprising: a switching unit for connecting the selected from the first PWM unit and the second PWM unit to the corresponding secondary transfer roller or the secondary transfer backup roller; , (a) receiving a printing command from the control unit and bringing the secondary transfer roller into contact with the transfer belt; (b) applying a bias voltage to the secondary transfer backup roller; (c) detecting a sheet entering the secondary transfer roller and applying a bias voltage to the secondary transfer roller; And and (d) applying a bias voltage to the secondary transfer backup roller when the paper leaves the transfer nip of the secondary transfer roller. The method of claim 5, wherein In step (a), (a1) determining whether the secondary transfer roller is in contact with the transfer belt using a proximity sensor; And (a2) if it is determined that the secondary transfer roller is spaced apart from the transfer belt, contacting the secondary transfer roller with the transfer belt by the separation means; 2. Car Warrior Method. delete