JP3090328B2 - Image forming device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus capable of using a color toner in addition to a black toner.

[Conventional technology]

There is an image forming apparatus for forming an image on plain paper by an electrostatic latent image technique, for example, a copying machine or an optical printer using a laser, an LED (light emitting diode), or an LCDA (liquid crystal array).

As is well known, the image formation by the electrostatic latent image technique is charged,
It consists of the steps of exposure, development, transfer, and fixing, but before the toner image formed by development is transferred onto the paper by applying a high voltage of the opposite polarity to the toner from the back of the adhered paper, In order to transfer the toner to the photoconductor, pre-transfer static elimination is performed to irradiate the photoconductor with light from above the toner to weaken the charging of the photoconductor.

If the effect of the pre-transfer static elimination is small, a considerable amount of toner remains on the photoreceptor after the transfer, causing insufficient transfer. If the effect is too large, the toner drops off before the transfer and the toner image on the paper is removed. A large number of spot-like white spots occur in the high density portion of

For this reason, for example, in the case of a copying machine, as shown in JP-A-61-213875, the density of a toner image developed by copying a target having a reference density before scanning an original is detected, and irradiation is performed in accordance with the density. There was a proposal to control the amount of light.

On the other hand, recently, in addition to an expensive full-color image forming apparatus such as a color copying machine in which black toner is added to three primary color toners,
Relatively inexpensive image forming apparatuses capable of forming a monocolor image or a two-color image of black and monocolor using not only a black toner but also a color toner are commercially available.

In general, such an image forming apparatus is provided with one replaceable developing unit (hereinafter, also simply referred to as "unit") and a replaceable color unit in order to reduce costs. Some do not have black units.

In each case, a plurality of colors can be selectively used by exchanging the unit. However, in practice, black is the mainstream, and the former can be a unit exchange, and the latter can be a black copy by designation from an operation panel.

However, although slightly different depending on the type of color, the effect of pre-transfer static elimination is largely different between black toner and color toner. As a result, white spots may occur not only in the high density area but also in the medium density area.

For this reason, as shown in, for example, Japanese Utility Model Application Laid-Open No. Sho 62-109168, the amount of light from the light source for pre-transfer static elimination is controlled in accordance with the development color information of the developing device. It has been proposed to reduce the amount of light.

[Problems to be solved by the invention]

However, in an image forming apparatus in which the developing device is replaceable, in order to be able to automatically control the light amount of the light source of the pre-transfer static elimination according to the developing color information of the mounted developing device, the developing device is incorporated in the developing device. It is necessary to provide a means for transmitting the color information of the toner, and on the apparatus main body side, a means for detecting the color information by the transmission means, and a means for controlling the light amount of the light source of the pre-transfer static elimination based on the detection result, There is a problem that the cost is increased due to the complicated configuration.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has an image forming apparatus capable of replacing developing means containing toners of different colors. It is an object of the present invention to automatically perform an optimal pre-transfer static elimination process in accordance with the color of the toner used in the above-described method, and to always form an image having excellent image quality.

[Means for solving the problem]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an electrostatic latent image formed by exposing a charged photoreceptor to toner by a developing unit to convert the electrostatic latent image into a visible toner image. In the image forming apparatus, the developing unit is replaceable, and the developing unit to be mounted is replaced with a developing unit. An irradiation amount control member for controlling the light irradiation amount of the pre-transfer static elimination means in accordance with the color of the toner contained therein; the irradiation amount control member is provided integrally with the developing means to be mounted; This is a light-shielding edge that shields a part of the irradiation light on the surface of the photoconductor by the pre-transfer charge removing means according to the color of the toner to be transferred.

Then, the light-shielding edge may be provided in the developing means incorporating the color toner, and the light-shielding edge may not be provided in the developing means incorporating the black toner.

(Operation)

With the above-described configuration, when the developing unit is attached to the image forming apparatus, the developing unit issues a signal indicating color information of the built-in toner, or the main body detects the signal and responds to the detected information. There is no need to provide a special circuit for controlling the light irradiation amount of the pre-transfer static elimination means, and the pre-transfer static elimination according to the color of the built-in toner directly by the irradiation light quantity control member by the light shielding edge provided in the developing means. The light irradiation amount of the means can be controlled to an optimum state.

Therefore, the image forming apparatus can form an image of excellent quality at all times with a very simple configuration and little cost increase and without any trouble of the operator.

〔Example〕

Hereinafter, an embodiment of the present invention will be specifically described with reference to the drawings. Before that, the light irradiation amount of the pre-transfer static elimination means is controlled according to the color of the toner used, which is the underlying technology. The technology will be described.

FIG. 3 shows an example of a mechanism of a two-color copying machine, which is an image forming apparatus having a fixed black (developing) unit as a developing means and a replaceable color (developing) unit. It is an outline sectional view.

The copying machine 100 includes a copying optical system for copying an original, an image forming system for developing an electrostatic latent image formed by exposure and transferring the image onto a sheet (plain paper) as a transfer target, And a sheet conveying system for fixing the image transferred thereon and discharging the image.

An image forming system is an OP in which an electrostatic latent image is formed by exposure to light by being covered with an OPC (organic semiconductor), which is a photosensitive member that charges the surface.
C drum 1, charging charger 2, replaceable color unit 3, fixed black unit 4, and PT, which is a pre-transfer static elimination means, disposed in a clockwise direction around the OCP drum 1.
(Pre-transformer) A lamp 5, a transfer separation charger 6, a photosensor 7, a cleaning device 8, and a neutralization lamp 9.

The color unit 3 and the black unit 4 are slightly slidable in the horizontal (left and right directions in FIG. 3) direction, respectively, and are set to black, monocolor, and two-color modes specified by an operator via an operation panel (not shown). Based on a command output from a control device (not shown), one of the
It is in contact with the C drum 1 and the other is separated.

The copying optical system includes a scanning illumination system 12 in which a lamp 11a for illuminating the original 10 and a first mirror 11b are integrally formed, and a second mirror 13a and a third mirror 13b whose optical axes are orthogonal to each other. The scanning optical system 14 configured, the lens 15 fixed to the main body of the copying machine 100, the fourth mirror 16a and the fifth mirror 1 respectively.
It comprises a fixed optical system 16 composed of 6b and a sixth mirror 16c.

The paper transport system consists of upper and lower 2
Tier paper trays 19, 19a, paper feed rollers 20, 20a, 20b, registration roller pair 21, transport drum 22, paper discharge roller 23, re-transport path 2
4, 24a, switching mechanisms 25, 25a provided at the entrances thereof, and a transport mechanism comprising transport rollers provided in the middle of each transport path, a fixing device 26 for fixing an image on paper, And a paper discharge tray 27 from which the collected paper is discharged.

First, the most common case of a black copy will be described. Contrary to the state shown in FIG.
In contact with the drum 1, the color unit 3 is separated.

When the copying operation starts, the OPC drum 1 rotates clockwise, the charging charger 2 starts discharging, and the lamp 11a
Lights up.

When the charged portion of the surface of the OPC drum 1 reaches the exposure position, the scanning illumination system 12 moves to the right at the same speed as the peripheral speed of the OPC drum 1, and the scanning optical system 14 moves to the right at half the speed. After scanning the surface of the original 10 with the lens 15 and exposing the image of the original 10 illuminated by the lamp 11a on the OPC drum 1 with the lens 15, an electrostatic latent image is formed. As a result, black toner is adhered and converted to a visible toner image.

Next, the electrostatic latent image is irradiated with light transmitted from the PT lamp 5 through the black toner adhered thereon, and a part of the charge is lost, so that the adhesion of the toner is weakened. Transfer will be performed. On the other hand, for example, only one sheet of paper 18 on the upper paper feed tray 19 is taken out by the paper feed roller 20, passes through the conveyance path, comes into contact with the registration roller pair 21, temporarily stops, and then is moved by the registration roller pair 21. It is sent out in synchronization with the toner image.

When the paper 18 overlaps the toner image on the OPC drum 1, the toner image is transferred onto the paper 18 by the transfer separation charger 6, and the paper 18 separated from the OPC drum 1 is transferred onto the transport drum 22 with the toner image placed thereon. To the fixing device 26.

The sheet 18 on which the toner image has been fixed by the fixing device 26 is discharged onto a discharge tray 27 by a discharge roller 23.

The toner slightly remaining on the OPC drum 1 after the transfer is collected by the cleaning device 8, and the charge disappears by the irradiation of the charge removing lamp 9 to enter a cycle in which the next charging starts.

In the case of a mono-color copy, the color unit 3 and the black unit 4 return to the states shown in FIG. 3, respectively, and the electrostatic latent image on the OPC drum 1 is replaced with the color toner contained in the mounted color unit 3. Are different from those of the black copy, except for the point that the image is visualized.

In the case of two-color copying, for example, originals for a portion to be blackened and a portion to be colored on a copy (hereinafter referred to as a “black original” and a “color original”, respectively) are separately prepared, and each unit is exchanged by the operator while exchanging the originals. Specify
What is necessary is just to overlap and copy on the same paper.

That is, first, the color unit 3 of a desired color is set, and then the mode of two-color copying is designated.
25 is in the state shown by the broken line.

Next, if the color mode is designated and the color unit is activated (as shown in FIG. 3), the color document is set and the copying operation is started, the copying, development and transfer are continuously performed until the designated number of sheets is reached. After the fixing, the paper of the monocolor image after the fixing is guided by the switching claw 25 and stacked face down on the re-conveying path 24. When the specified number of color copies are completed, the switching claw 25 becomes a solid line. Returning to the state shown by, when the black unit is activated, the copier 10
0 stops once.

Next, when the black original is set and the copying operation is restarted, the feed roller 20b feeds the sheets stacked on the re-conveying path 24 one by one to the pair of registration rollers 21 to form a face-up mono-color image. The black toner image is transferred onto the image. The sheet on which the black image has been fixed is discharged onto the discharge tray 27 by the discharge rollers 23 as it is because the switching claw 25 has returned.

FIG. 4 is a perspective view showing an example of a PT lamp 5 which is a light source of the pre-transfer charge removing means.

As is apparent from FIG.
In order to illuminate the entire width of the LED uniformly, a number of LEDs (light emitting diodes) are arranged in a row, and these LEDs are DC
They are connected in series or in series / parallel according to the power supply voltage, emit light with the amount of light emission according to the current, and perform charge removal before transfer.

FIG. 1 and FIG. 2 are circuit diagrams each showing an example of a light emission amount control device which is an irradiation amount control means, and a plurality of LEDs.
Are connected in series to drive an LED line 32 with a 24 V DC power supply.

The light emission amount control device 30 shown in FIG.
A single-pole, three-contact switching switch 31 connected to 24V, and resistors R1 to R3 provided between the respective contacts 31a, 31b, 31c and the other end of the grounded LED line 32. value is
R1 <R2 <R3.

The contact of the switching switch 31 is switched according to a toner color signal from a toner color detecting unit described later. For example, for black toner, the LED line 32 is connected to the contact 31a and emits light at the maximum light amount. The color toner is classified into two groups according to its color, and connected to the contact point 31b or 31c, the LED line 32 emits light with an intermediate light amount or a minimum light amount.

As a result, as shown in FIG. 5, during the pre-transfer static elimination operation time, the PT lamp 5 emits light at each level of (a), (b), and (c) in response to a separately designated timing signal. OPC
The drum 1 is irradiated.

The switching switch 31 may be a semiconductor switch,
When there are a plurality of D lines 32, a light emission amount control device 30 having the same configuration may be provided for each LED line, and these may be driven in parallel.

The light emission amount control device 33 shown in FIG.
And the transistor 35, and the LED line 32 is the same as that shown in FIG.

The pulse oscillator 34 outputs a PWM signal pulse-width modulated according to the toner color signal to the base of the transistor 35.

The transistor 35 whose collector is connected to DC24V and whose emitter is connected to the LED line 32 is a PWM input to the base.
Since the LED line 32 is turned on / off in response to the signal, the PT lamp 5 emits an OPC light with an amount of light proportional to the duty ratio of the PWM signal.
The drum 1 is irradiated.

Unlike the light emission amount control device 30 shown in FIG. 1, the light emission amount control device 33 can control one parallel circuit of these even if the number of LED lines increases.

 Hereinafter, the toner color detecting unit will be described.

In general, in detecting toner colors for pre-transfer charge removal, it is not necessary to be strict enough to individually identify the color of each toner, and it is not necessary to discriminate between black and color, or between black, dark and light colors. I hope you can.

Accordingly, an example of the simplest toner color detecting means for distinguishing between black and color is the image forming apparatus 10 shown in FIG.
At 0, which unit of the color unit 3 or the black unit 4 is used is determined by software using a sequence controller (not shown) composed of, for example, a microcomputer.

Next, an example of a simple toner color detecting means uses the photo sensor 7 shown in FIG.

When the initial setting at the time of power-on immediately after the operator replaces the color unit 3 is performed, the OPC drum 1 is rotated to turn on the charging charger 2, and the charged or charged chart having a predetermined density is copied. An electrostatic latent image is formed, developed by the color unit 3 and color toner is adhered thereto, and the color of the toner is detected by detecting the reflectance of the color toner by the photo sensor 7 having a built-in irradiation light source.

The photo sensor 7 originally detects the density of the black toner and adjusts the bias voltage and the like applied to the developing unit. Since there is a difference in the rates, it can be used also as the toner color detecting means.

6 and 7 are perspective views showing another example of the toner color detecting means, and show a state where the same thing is viewed from opposite directions.

When the replaceable color unit 3 is mounted on the copying machine body in the direction of the arrow, a color detection comprising a screw socket 40 fixed on the side of the color unit 3 abutting on each other and a double push switch fixed on the body side. And a discriminating screw attached to the screw socket 40 according to the color of the toner contained
The head of 42 is set so that the projections 41a and 41b of the switches SW1 and SW2 (not shown) incorporated in the color detector 41 are turned on by pressing them, and are set to be off if there is no discrimination screw 42. I have.

For example, if the built-in toner is black, switches SW1 and SW2
Is (off / off), if it is red (on / off), if it is green (off / on), if it is blue (on / on), the color detector 41 is located at the corresponding position of the screw socket 40. The toner color can be detected by detecting the combination of the presence or absence of the determination screw 42.

 Next, an embodiment of the present invention will be described.

FIG. 8 is a schematic sectional view of a copying machine showing an embodiment of the present invention, in which one of exchangeable developing units each containing a black toner or various color toners is mounted. Machine. The same or equivalent parts as those of the copying machine 100 shown in FIG.

The main difference between the copying machine 200 and the copying machine 100 is that the copying machine 100 includes a fixed black unit and a replaceable color unit, while the replaceable developing unit 50 including black includes a replaceable color unit. That is, only one can be attached.

Therefore, in principle, this is a copying machine that performs black copy or monocolor copy, and switching between black copy and monocolor copy is performed by replacing the developing unit 50, which requires much operator's labor, but is cost-effective. Is cheap.

Otherwise, the fixed reflection system is constituted only by the fourth mirror 16a, the conveyance belt 22a is used instead of the conveyance drum 22, and the re-conveyance paths 24, 24a and the switching claws 25, There is no 25a.

9 and 10 show a black unit incorporating a black toner.
FIG. 9 is a partial cross-sectional view showing an example in which a color unit 51 and a color unit 52 containing color toner are mounted, and the same parts as those in FIG. 8 are denoted by the same reference numerals.

The black unit 51 shown in FIG. 9 almost irradiates the surface of the OPC drum 1 with the amount of light emitted from the PT lamp 5 similarly to the conventional developing unit.

On the other hand, the PT lamp 5 of the color unit 52 shown in FIG.
A light-shielding edge 52a, which is an irradiation amount control member according to the present invention, is provided in a portion adjacent to the light source, so that a part of the light irradiation amount of the PT lamp 5 is shielded and dimmed.

The amount of light reduction by the light-shielding edge 52a differs depending on the properties of the color toners to be used. However, when the same amount of light reduction is required for all the color toners, only one type of color unit 52 is required, and the color unit 52 is large for light color and dark color. If they are separated, a color unit having two types of light-shielding edges and dark-color shielding edges having different light reduction amounts may be prepared.

By using the color unit 52 having the light-shielding edge 52a and the black unit 51 without the light-shielding edge as described above and adjusting the light emission amount of the PT lamp 5 in accordance with the black toner, the developing unit 50
It is not necessary to make any changes to the body of the copying machine 200 even if the printer is replaced, and the pre-transfer static elimination suitable for the black toner and the color toner can be performed.

〔The invention's effect〕

As described above, according to the present invention, it is possible to attach a developing unit having a built-in toner of any color to the image forming apparatus main body with a very simple configuration and little cost increase.
Appropriate pre-transfer static elimination can be performed automatically according to the color of the toner to be used without using any special circuit or the like, and an image with excellent image quality can always be formed.

[Brief description of the drawings]

1 and 2 are circuit diagrams each showing an example of a light emission amount control device. FIG. 3 is a schematic sectional view showing an example of a copying machine capable of two-color copying. FIG. 4 is a perspective view showing an example of the PT lamp, and FIG.
The figure is a diagram showing an example of the light emission characteristics of the PT lamp. 6 and 7 are perspective views showing an example of the toner color detecting means when viewed from opposite directions. FIG. 8 is a schematic sectional view showing an example of a copying machine showing one embodiment of the present invention. 9 and 10 are partial cross-sectional views each showing an example of the replaceable developing unit. 1 OPC drum (photoreceptor drum) 3,52 Color unit (developing unit) 4,51 Black unit (developing unit) 5 PT lamp (pre-transfer charge eliminating unit) 7 Photo sensor (toner color) Detecting means) 30,33 ... Light emission amount control device (irradiation amount controlling means) 41 ... Color detector (toner color detecting means) 50 ... Developing unit (developing means)

Claims (2)

(57) [Claims] An electrostatic latent image formed by exposing a charged photoreceptor to a visible toner image by attaching toner to the electrostatic latent image by a developing means; In an image forming apparatus for weakening the body charge and transferring the toner image onto a transfer target body by a transfer unit to form an image, the developing unit is replaceable, and the developing unit to be mounted has a built-in toner. An irradiation amount control member for controlling the light irradiation amount of the pre-transfer static elimination means in accordance with the color of the toner. An image forming apparatus, comprising: a light-shielding edge for shielding a part of light irradiated on the surface of the photoconductor by the pre-transfer charge removing unit according to a color. 2. An image forming apparatus according to claim 1, wherein said light-shielding edge is provided in a developing means incorporating a color toner, and said light-shielding edge is not provided in a developing means incorporating a black toner.