JPH07108703A - Image forming device - Google Patents

Abstract

(57) [Summary] [Object] To provide an image forming apparatus having a toner carrier whose magnetic force is controllable and capable of obtaining sufficient density contrast even at a practical driving voltage. [Structure] The image forming apparatus includes a toner carrying sleeve 14
A magnet 15 whose vertical position can be adjusted is arranged inside the toner, and the strength of the magnetic force at the outermost peripheral portion of the toner carrying sleeve 14 can be changed. Therefore, it is possible to adjust the image density characteristic with respect to the control voltage and thereby prevent image fog from occurring.

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 the charged toner particles so that the flow of the toner particles passing through the aperture is modulated by the electric potential, and a means for relatively moving the support and the aperture electrode body to position the support in the particle flow path. 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. No. 5,967,967, the voltage applied to the control electrode when the aperture electrode body is off is disclosed by disposing the aperture electrode body with the reference electrode on the support side and the control electrode on the toner supply side. 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, if the drive voltage is the voltage difference between the control voltage at the time of ON and the control voltage at the time of OFF, this drive voltage is It is preferable that the voltage is as small as possible in view of the constraints of the integrated circuit that drives the device, and the practical driving voltage must be set within 50V. However, since the relationship between the control voltage applied to the control electrode and the image density formed on the support has the characteristics shown by the solid line in FIG. 4, when the drive voltage is 50 V, the control voltage is Even if it was set, it was impossible to obtain a sufficient density of 1.5 or more when turned on and to print without fog of 0.07 or less when turned off.

More specifically, for example, in the solid line in FIG. 4, when the control voltage at the time of ON is set to 50V and the control voltage at the time of OFF is set to 0V, the image density at the time of ON is 1.5 or more. However, when it is off, image fogging occurs and the image density does not drop sufficiently, resulting in an unsightly image. However, in order to suppress the image fog, FIG.
In the solid line, if the control voltage at the time of on is set to 30V and the control voltage at the time of off is set to -20V, the image density is sufficiently reduced to 0.07 which is the density at which image fog is suppressed, but the image at the time of on is Since the density is insufficient, the image is difficult to see.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an image forming apparatus capable of obtaining a sufficient density contrast even with a practically low driving voltage.

[0010]

To achieve this object, an image forming apparatus according to the present invention comprises a toner flow control means for controlling the flow of charged toner, and a toner supply for supplying toner to the toner flow control means. And a means for supplying the toner to the toner flow control means, wherein the supply means is constituted by a toner carrier having magnetic means provided so that the strength of the magnetic force at the portion for supplying the toner to the toner flow control means can be adjusted. To do.

[0011]

According to the image forming apparatus of the present invention having the above-mentioned structure, image formation is achieved in which sufficient density contrast can be obtained even with a practical driving voltage.

[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 rear electrode plate 22 has a gap of 1 mm above an aperture electrode body 1 as a toner flow control means. Are arranged on a chassis (not shown). A pair of conveyance rollers 119 are arranged on the right side of the back electrode plate 22, and the support body 20 conveyed by the pair of conveyance rollers 119 is arranged.
Are configured to be inserted into the 1 mm gap. 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 plate 22. 20 is the fixing device 2
6 are provided.

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 hollow toner carrying sleeve 14 and a toner layer regulating blade 18. Here, the toner carrying sleeve 14 carries the toner 16 and conveys it toward the aperture electrode body 1.
2 supplies the toner 16 to the toner carrying sleeve 14.

The supply roller 12 and the toner carrying sleeve 14 are rotatably supported by the toner case 11 in the direction of the arrow shown in FIG. Further, the toner layer regulating blade 1
8 is a toner 16 carried by the toner carrying sleeve 14.
Is adjusted so that the amount of
For uniformly charging the toner 16,
It is pressed against the toner carrying sleeve 14.

Further, inside the toner carrying sleeve 14, a magnet 15 is disposed as a magnetic means which is supported by a chassis (not shown) so that its vertical position can be adjusted. As shown in FIG. 5, both ends of the magnet 15 are pressed downward by the leaf springs 40 and supported by the eccentric cam 41. Therefore, the vertical position of the magnet 15 can be arbitrarily adjusted according to the rotation angle of the eccentric cam 41, whereby the toner carrying sleeve 14 can be adjusted.
Of the toner supply portion to the aperture electrode body 1, that is, the strength of the magnetic force at the outermost peripheral portion of the toner carrying sleeve 14 can be changed. Therefore, the concentration curve shown by the solid line in FIG. It is possible to move it in parallel to the minus side of.

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. The aperture electrode body 1 is pressed against the toner carrying sleeve 14 at the aperture position of the insulating sheet 2 with the control electrode 4 facing the support body 20 as shown in FIG.

The positional relationship between the aperture 6 of the aperture electrode body 1 and the toner carrying sleeve 14 will now be described in detail. As shown in FIG. 3, each aperture 6 has a center line 30 in the toner carrying sleeve 14. Is arranged so as to pass through the uppermost part of the peripheral surface of the toner carrying sleeve 14 and the central axis 32 of the toner carrying sleeve 14. According to this, each aperture 6
Are evenly arranged on the left and right with respect to the uppermost part of the peripheral surface of the toner carrying sleeve 14, so that the distribution of the toner 16 passing through each aperture 6 can be made uniform throughout the entire aperture. Further, since the wall surface of the aperture 6 and the flying direction of the toner 16 are parallel to each other, it is possible to stably fly the toner.

Further, as shown in FIG. 3, the aperture electrode body 1 itself is pressed against the toner carrying sleeve 14 so as to bend leftward and rightward about the aperture 6 at the same angle. As a result, the contact area between the aperture electrode body 1 and the toner carrying sleeve 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 applying circuit 8 is connected between the control electrode 4 and the toner carrying sleeve 14. The control voltage application circuit 8 is configured to apply a voltage of 0 V or +50 V 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 sleeve 14, and this DC power source can apply a voltage of +1 kV to the back electrode roller 22. It has become.

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

First, by rotating the toner carrying sleeve 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 sleeve 14 to be negatively charged. The toner is carried on the toner carrying sleeve 14. The carried toner 16 is thinned and charged by the layer regulation blade 18, and then is conveyed toward the aperture electrode body 1 by the rotation of the toner carrying sleeve 14. Then, the toner on the toner carrying sleeve 14 is rubbed by the insulating sheet 2 of the aperture electrode body 1 and supplied below the aperture 6.

Here, in accordance with the image signal, the control voltage applying circuit 8 adds + to the control electrode 4 corresponding to the image portion.
A voltage of 50V is applied. As a result, an electric force line from the control electrode 4 toward the toner carrying sleeve 14 is formed near the aperture 6 corresponding to the image portion due to the potential difference between the control electrode 4 and the toner carrying sleeve 14. As a result, the negatively charged toner receives an electrostatic force in the direction of higher electric potential, passes through the aperture 6 from the toner carrying sleeve 14, and is drawn out to the control electrode 4 side. The extracted toner 16 further flies toward the support body 20 due to the electric field formed between the support body 20 and the aperture electrode body 1 by the voltage applied to the back electrode plate 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 sleeve 14 and the control electrode 4, the toner carrying sleeve 14
The upper toner 16 does not receive an electrostatic force, and further, the fixing position of the magnet 15 is adjusted to adjust the toner holding sleeve 14.
By changing the strength of the magnetic force at the uppermost portion of the outer periphery of the toner, it is possible to prevent the toner from passing through the aperture 6 and causing image fogging as shown by the wavy line in FIG.

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.

If an insulating toner is used in the image forming apparatus constructed as described above, the toner carrying sleeve 1
The insulating property between the control electrode 4 and the control electrode 4 is maintained, and the aperture 6 is not broken down.

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 sleeve 14 which faces the aperture 6, so that the carrying is carried. Since the control electric field can be directly applied to the toner 16 thus generated, the control efficiency is good.

Further, even if a part of the toner 16 supplied receives mechanical force due to sliding with the aperture electrode body 1 and enters the aperture 6 corresponding to the non-image portion, the inside of 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 sleeve 14 and the aperture electrode body 1 are opposed to each other with the toner layer interposed therebetween, they can be arranged at a relatively short distance, so that the control voltage can be lowered and an inexpensive driving element can be provided. Can be used.

In addition, the insulating sheet 2 of the aperture electrode body 1
Is directed toward the toner carrying sleeve 14, so that even if the toner 16 does not exist on the toner carrying sleeve 14 due to a defect in the toner supply system, the control electrode 4 and the toner carrying sleeve 14 come into contact with each other and electrically short-circuit. , Do not break the drive element.

Further, since the aperture electrode body 1 and the toner 16 on the toner carrying sleeve 14 are in contact with each other at the entrance portion of the aperture 6, the toner 16 deposited at the entrance portion of the aperture 6 is not supported. Is washed away by the toner sequentially supplied by
Do not deposit 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, it 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 is used as the toner flow control means, but it is also possible to use, for example, a knitted electrode body as described in the specification of US Pat. No. 5,036,341.

Although the mounting position of the magnet 15 can be adjusted in the vertical direction, the magnet 15 may be rotated to adjust the magnetic force on the surface of the toner carrying sleeve 14.

[0036]

As is apparent from the above description, the image forming apparatus of the present invention uses the toner carrier whose magnetic force is controllable so that sufficient density contrast can be obtained even at a practical driving voltage. The resulting image formation is achieved.

[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 sleeve used in the image forming apparatus of the present invention.

FIG. 4 is a diagram showing a relationship between control voltage and image density.

FIG. 5 is a view showing a vertical position adjusting mechanism of a magnet.

[Explanation of symbols]

 1 Aperture electrode body 2 Insulating sheet 4 Control electrode 6 Aperture 8 Control voltage application circuit 14 Toner carrying sleeve 15 Magnet 22 Rear electrode plate 24 DC power supply

Claims (2)

[Claims] 1. A toner flow control means for controlling the flow of charged toner, and a toner supply means for supplying toner to the toner flow control means, wherein the supply means supplies toner to the toner flow control means. An image forming apparatus comprising a toner carrier having a magnetic unit provided so that the strength of the magnetic force in the portion to be adjusted can be adjusted. 2. The toner carrier is composed of a hollow toner carrying sleeve, and the magnetic means is arranged in the toner carrying sleeve so that the distance between the toner carrying body and the toner flow control means can be adjusted. The image forming apparatus according to claim 1, wherein: