JPH0740576A - Image forming device - Google Patents

Abstract

PURPOSE:To provide an image forming device with a toner feed means which is free from image density fouls and can provide sufficient image contrast. CONSTITUTION:A carrying roller driver 38 of a stepping motor 36 for driving a toner carrying roller 14, a control voltage application circuit 8 and a direct current power source 24 of an image forming device are controlled by a printing control circuit 40. The relation of the toner feed speed to the control voltage of a control electrode 4 is stored in the form of a table in a memory section of the printing control circuit 40. The control voltage when power is ON is interlocked with a density control switch operated and set by an operator, and changed by the printing control circuit 40, following which the toner feed speed of the toner carrying roller 14 is changed to prevent the overfeed of toner.

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 which can be used in copying machines, printers, plotters, facsimiles and the like.

[0002]

2. Description of the Related Art Conventionally, as one of image forming apparatuses, an electrode having a plurality of openings (hereinafter referred to as apertures) is used, and a voltage is applied to the electrode based on image data. U.S. Pat. No. 3,689,935 discloses controlling toner particles so that they can pass through the aperture and forming an image on a support by the toner particles that have passed.

This image forming apparatus comprises a flat plate made of an insulating material, a continuous reference electrode formed on one surface of the flat plate, and a plurality of control electrodes insulated from each other formed on the other surface. , An aperture electrode body having at least one row of apertures formed through each of the control electrodes, and a means for selectively applying a potential between the reference electrode and the control electrode. A means for supplying charged toner particles so that the flow of toner particles passing through the aperture is modulated by an electric potential, and a means for positioning the support in the particle flow path so that the support and the aperture electrode body can move relative to each other. It consists of and.

Also, for example, US Pat. No. 4,743,926.
Nos. 4,755,837, 4,780,733, and 4,847,796 disclose an image forming apparatus in which an aperture electrode body is arranged with a control electrode on the support side and a reference electrode on the toner supply side. There is.

In contrast, US Pat. No. 4,912,489
In the specification of the above U.S. Pat. It is described that it can be suppressed to about 1/4 as compared with the image forming apparatus.

Here, the "off" means a time when the toner particles are not attached to the support, that is, a time when a blank portion of an image is formed, and conversely, "on" means that the support is on the support. It means a time point when a toner image is formed on.

[0007]

However, in the conventional image forming apparatus as described above, when the supply speed of the toner to the aperture is high, the toner is deposited so as to blow out to the exit of the aperture, which stains the recording paper. There was a problem. When the supply speed is decreased, this blowing is improved, and the blowing becomes unnoticeable at a certain feeding speed, but the feeding speed at this time is the magnitude of the control voltage applied to the aperture electrode, that is, the control electric field. It changed according to the size of.

This phenomenon can be explained as follows. When a control electric field having a sufficient strength is applied, all of the supplied toner can pass through the aperture in a region where the toner supply speed is low, but when the toner supply speed increases, a small aperture with a diameter of about 100 μm is formed. In addition to flooding with a large amount of toner, the flying speed of the toner becomes constant near the aperture exit due to the viscous resistance of air, so even if an excessive amount of toner is supplied, the amount of toner that can pass through the aperture will be saturated. , An excessive amount of toner stays near the aperture exit.

The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to provide an image forming apparatus provided with a toner supply means capable of obtaining a sufficient image contrast without image stains. I am trying.

[0010]

In order to achieve this object, an image forming apparatus of the present invention comprises a toner flow control means for controlling the flow of charged toner, the toner carrying the toner, and the toner carrying the toner flow. An image forming apparatus, comprising: a toner supply unit that supplies the toner to the control unit; It is characterized by being provided.

[0011]

In the image forming apparatus of the present invention having the above-mentioned structure, the toner supply amount of the toner supply device is controlled in accordance with the driving condition of the toner flow control means. Toner retention can be prevented, and the formed image is not disturbed by the retained toner, and good image output can be performed.

[0012]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing an outline of an image forming apparatus embodying the present invention. A cylindrical rear surface having a gap of 1 mm on the upper side of an aperture electrode body 1 as a toner flow control means. An electrode roller 22 is rotatably arranged on a chassis (not shown), and the support body 20 is inserted into the gap.
Are configured to be transported. Further, a toner supply device 10 is arranged below the aperture electrode body 1 along the longitudinal direction of the aperture electrode body 1, and further, a support body conveyed by the back electrode roller 22. A fixing device 26 is disposed at the destination of the movement of 20.

Next, the respective components will be described in detail. In the toner supply device 10, the toner case 11 also serving as a housing of the entire device, the toner 16 housed in the toner case 11, and the supply roller 12 are provided. And a toner carrying roller 14 and a toner layer regulating blade 18. Here, the toner carrying roller 1
Reference numeral 4 is for carrying the toner 16 and carrying it toward the aperture electrode body 1, and the supply roller 12 is for supplying the toner 16 to the toner carrying roller 14.

The supply roller 12 and the toner carrying roller 14 are rotatably supported by the toner case 11 in the direction of the arrow shown in FIG. Further, the toner carrying roller 14 is connected to a stepping motor 36, the supply roller 12 is also connected to a motor (not shown), and each roller is driven by the motor.

The toner layer regulating blade 18 adjusts the amount of the toner 16 carried by the toner carrying roller 14 so that it is uniform on the roller surface.
Is uniformly charged and is pressed against the toner carrying roller 14.

As shown in FIG. 2, the aperture electrode body 1 includes a 25 μm thick insulating sheet 2 made of polyimide and having a diameter of 1 μm.
A plurality of apertures 6 having a size of 00 μm are formed in one row, and a control electrode 4 having a thickness of 1 μm is formed on each of the apertures 6 on the upper surface. As shown in FIG. 1, the aperture electrode body 1 is pressed against the toner carrying roller 14 at the aperture position of the insulating sheet 2 with the control electrode 4 facing the support body 20 side.

Here, the positional relationship between the aperture 6 of the aperture electrode body 1 and the toner carrying roller 14 will be described in detail. As shown in FIG. 3, each center line 30 of each aperture 6 has a toner carrying roller 14. It is arranged so as to pass through the uppermost portion of the peripheral surface of and the central shaft 32 of the toner carrying roller 14. According to this, each aperture 6
Based on the uppermost part of the peripheral surface of the toner carrying roller 14,
By arranging them evenly on the left and right, the distribution of the toner 16 passing through each aperture 6 can be made uniform over the entire area of the aperture. In addition, the wall surface of the aperture 6 and the toner 16
Since the flying direction of the toner is parallel to the flying direction of the toner, it is possible to stably fly the toner.

Further, the aperture electrode body 1 itself has an aperture 6 with respect to the toner carrying roller 14 as shown in FIG.
It is pressed so that it bends to the left and right about the same angle. As a result, the contact area between the aperture electrode body 1 and the toner carrying roller 14 can be increased, and the lower periphery of the aperture 6 can be pressed uniformly to the left and right, so that uneven toner concentration is minimized. Can be suppressed.

A control voltage application circuit 8 is connected between the control electrode 4 and the toner carrying roller 14.
The control voltage application circuit 8 is configured to apply 0V or an arbitrary + voltage to the control electrode 4 based on the image signal.

Further, a DC power source 24 is connected between the back electrode roller 22 and the toner carrying roller 14, and this DC power source is + with respect to the back electrode roller 22.
A voltage of 1 kV can be applied.

Next, the structure of the main part of this embodiment will be described with reference to FIGS. 1, 4 and 5.

At least the carrier roller driver 38 for driving the stepping motor 36, the control voltage application circuit 8, and the DC power supply 24 are controlled by the print control unit 40.

The print control unit 40 is composed of a well-known CPU, and stores the relationship between the control voltage of the control electrode and the toner supply speed as a table in the storage unit as shown in FIG.

The graph of FIG. 5 is used to create the above graph, and there are five types of relationships between the peripheral speed of the carrier roller corresponding to the toner supply speed and the formed image (solid black). It shows the control voltage of.

Here, in the plots shown by the solid line, the dotted line, and the broken line, the control voltage when the printing is turned on is +150 to + 60V.
The change in visible light absorptance of the formed image (solid black) with respect to the toner supply speed when each control voltage is adopted is shown in FIG. It is a plot. Also, a black circle (●)
Shows the saturated toner supply speed at each control voltage. A plot of this is the graph in FIG.

For example, referring to the graph of FIG. 4, when the control voltage at the time of ON is + 120V, the saturated toner supply speed is 10
0 mm / s, which is faster than the toner carrying roller 14
When is rotated, the toner is over-supplied, and the excess toner is accumulated near the exit of the aperture 6 and disturbs the image on the support 20.

Therefore, the control voltage and the toner supply speed must be controlled so as to maintain the relationship shown by the shaded portion in FIG. 4, and the control voltage at the time of turning on is set by the user. It is changed by the print control circuit 40 in conjunction with a density adjustment switch (not shown).

For example, when the toner is supplied at +120 V when turned on and the toner supply speed is 90 mm / s in the initial state, the density adjustment switch is operated to lower the density, and the control voltage when turned on is changed. It is assumed that the voltage is set to + 75V. In this case, the toner supply speed is 90 mm / s
As it is seen from FIG. 4, the toner is excessively supplied, so that the toner supply speed is 70 mm / s.
A signal is sent from the print control circuit 40 to the carrying roller driver 38 so as to drop it.

Next, the operation of the image forming apparatus configured as described above will be described.

First, by rotating the toner carrying roller 14 and the supply roller 12 in the direction of the arrow shown in FIG. 1, the toner 16 sent from the supply roller 12 is rubbed against the toner carrying roller 14 to be negatively charged. The toner is carried on the toner carrying roller 14. Toner 1 carried
The layer 6 is thinned by the layer regulation blade 18 and charged, and then is conveyed toward the aperture electrode body 1 by the rotation of the toner carrying roller 14. Then, the toner on the toner carrying roller 14 is supplied under the aperture 6 while being rubbed by the insulating sheet 2 of the aperture electrode body 1.

Here, in accordance with an image signal, the control voltage applying circuit 8 applies to the control electrode 4 corresponding to the image portion.
A control voltage when printing is turned on, which is controlled by the printing control circuit 40, is applied. As a result, a line of electric force directed from the control electrode 4 to the toner carrying roller 14 is formed in the vicinity of the aperture 6 corresponding to the image portion due to the potential difference between the control electrode 4 and the toner carrying roller 14. Thereby,
The negatively charged toner receives an electrostatic force in the direction of higher potential, passes through the aperture 6 from the toner carrying roller 14 and is drawn out to the control electrode 4 side. The extracted toner 16 further flies toward the support body 20 due to an electric field formed between the support body 20 and the aperture electrode body 1 due to the voltage applied to the back electrode 22 and the support body 20.
Deposit on top to form pixels.

A voltage of 0V is applied from the control voltage applying circuit 8 to the control electrode 4 corresponding to the non-image portion.
As a result, since no electric field is formed between the toner carrying roller 14 and the control electrode 4, the toner carrying roller 1
The toner 16 on 4 does not pass through the aperture 6 because it is not subjected to electrostatic force.

Further, the support 20 is fed by one pixel in the direction perpendicular to the aperture row while the toner 16 forms one row of pixels on the surface thereof. Then, the toner image is formed on the entire surface of the support 20 by repeating the above process. Then, the formed toner image is fixed on the support 20 by the fixing device 26.

In the image forming apparatus constructed as described above, if the insulating toner is used, the toner carrying roller 14 is used.
The insulation between the control electrode 4 and the control electrode 4 is maintained, and the aperture 6 does not cause dielectric breakdown.

In the above process, the control electric field generated by the control electrode 4 is formed between the control electrode 4 and the inside of the aperture 6, and between the aperture 6 and the toner carrying surface of the toner carrying roller 14 which faces the aperture 6, so that the carrying is carried. Toner 1
Since the control electric field can be directly applied to 6, the control efficiency is good.

Further, even if a part of the supplied toner 16 receives a mechanical force or the like by sliding with the aperture electrode body 1 and enters the aperture 6 corresponding to the non-image portion, inside the aperture 6 Since it can be controlled so as not to pass through the aperture 6 by the electric field, the toner controllability is good.

Further, since the toner carrying roller 14 and the aperture electrode body 1 are opposed to each other with the toner layer in between, the control voltage can be lowered and the inexpensive drive element can be provided because they can be arranged at a relatively short distance. Can be used.

In addition, the insulating sheet 2 of the aperture electrode body 1
Is directed toward the toner carrying roller 14 side, so that the toner
Even if 6 is not present, the control electrode 4 and the toner carrying roller 14 do not come into contact with each other and electrically short-circuit, and the drive element is not destroyed.

Further, since the aperture electrode body 1 and the toner 16 on the toner carrying roller 14 are in contact with each other at the entrance portion of the aperture 6, the toner 16 accumulated at the entrance portion of the aperture 6 is not supported. Since the toner 16 is pushed away by the toner sequentially supplied, the toner 16 does not accumulate and bridge to block the aperture 6.

The present invention is not limited to the embodiments described in detail above, and various modifications can be made without departing from the spirit of the invention.

For example, although the control voltage of the aperture corresponding to the non-image portion is set to 0V in the above embodiment, this may be a negative voltage. In this case, an image with less fogging can be obtained. Further, in the above embodiment, the aperture electrode body was used as the toner flow control means, but it is also possible to use, for example, a knitted electrode body as described in JP-A-1-503221. .

Further, in the above embodiment, the rotation speed of the toner carrying roller is controlled in accordance with the control voltage of the control electrode 4 when the printing is turned on, but the rotation speed of the toner carrying roller is kept constant. It is also possible to change the pressure contact force of the toner layer regulating blade against the toner carrying roller 14 to control the carrying thickness of the toner on the toner carrying roller.

[0044]

As is apparent from the above description, in the image forming apparatus of the present invention, the toner supply amount of the toner supply device is controlled according to the driving condition of the toner flow control means. It is possible to suppress toner accumulation in the vicinity of the aperture due to excessive supply of, and the formed image is not contaminated, and an image with good contrast can be output.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment embodying the configuration of an image forming apparatus of the present invention.

FIG. 2 is a perspective view showing a configuration of an aperture electrode body used in the image forming apparatus of the present invention.

FIG. 3 is a diagram schematically showing a configuration of an aperture electrode body and a toner carrying roller used in the image forming apparatus of the present invention.

FIG. 4 is a diagram showing a graph for explaining an operating procedure of a print control circuit.

FIG. 5 is a diagram showing a graph for explaining a procedure for creating the graph shown in FIG.

[Explanation of symbols]

 1 Aperture Electrode 2 Insulating Sheet 4 Control Electrode 6 Aperture 8 Control Voltage Applying Circuit 14 Toner Carrying Roller 22 Back Electrode Roller 24 DC Power Supply 36 Stepping Motor 40 Print Control Circuit

Claims (4)

[Claims] 1. An image forming apparatus comprising: a toner flow control unit that controls a flow of charged toner; and a toner supply unit that carries the toner and supplies the toner to the toner flow control unit. An image forming apparatus, comprising: a toner supply control unit for controlling a toner supply amount of the toner supply unit according to a driving condition of the toner flow control unit. 2. The toner supply amount of the toner supply device,
The image forming apparatus according to claim 1, wherein the image forming apparatus is controlled by a driving speed of the toner supply device. 3. The toner supply amount of the toner supply device,
The image forming apparatus according to claim 1, wherein the toner supply device is controlled by a toner carrying amount. 4. The toner supply amount of the toner supply device,
7. Under a certain toner flow control condition of the toner flow control means, the supply amount is set to a point below the point where the increase in the image contrast is saturated even though the toner supply amount is increased. The image forming apparatus according to any one of 1 to 3.