JPH10337896A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus having a simple structure capable of forming an image having high density and no density variation. SOLUTION: A vibrator device 30 is connected to one end of a support plate 17 in an arrangement direction of apertures. An electric magnet 35 is so constituted that a coil 34 is wound around a U-shaped iron core 33. In the vibrator device 30, the electric magnet 35 is disposed such that it excites an iron piece 32 fixed to the support plate 17 via a rubber plate 31. The rubber plate 31 satisfying the formula of 2πf=(k/m)<1/2> with the proviso that an elastic modulus is designated by (k), a mass of a print head and the support plate is by (m) and a resonance frequency is by (f), is used therefor.

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 applied to a copying machine, a printer, a facsimile, a plotter, and the like.

[0002]

2. Description of the Related Art Conventionally, an image forming apparatus for controlling the passage of toner particles by applying an image signal to an electrode having a toner flow path to obtain an image on a recording medium is disclosed in Japanese Patent Laid-Open No. 6-25 / 1994.
Japanese Patent Application Laid-Open No. 5163/1993 discloses an apparatus using an aperture (hereinafter referred to as an aperture) as a toner flow path.
No. 98, US Pat. No. 3,689,935 and the like.

In the former image forming apparatus, toner flow paths are arranged in a row, and a print head made of an insulating sheet provided with a control electrode corresponding to each toner flow path and carries toner as a charged body. And a toner carrying roller. The print head is arranged so that one side surface thereof is in contact with the peripheral surface of the toner carrying roller in the vicinity of the toner channel row, and a voltage corresponding to image data is applied to a control electrode (hereinafter, a control voltage). By controlling the passage of the charged toner through the toner flow path to form a toner image on a recording medium disposed on the side opposite to the toner carrying roller with the print head interposed therebetween. I have.

According to this image forming apparatus, since the toner on the toner carrying roller and the print head are in contact near the toner flow path, they adhere to the vicinity of the toner flow path and hinder the flow of the toner. Rubbing the toner with the toner that is transported later does not hinder the flow of the toner.

Normally, the toner supplied toward the toner flow path while being carried on the surface of the toner carrying roller exerts a van der Waals force on the surface of the toner carrying roller in addition to a mirror image force due to toner charging. Since the toner is attached by other physical force, the toner is applied to an electric field formed in the toner channel by a control voltage (hereinafter, referred to as a control electric field)
By itself, a very large control voltage is required to separate from the surface.

However, according to the above-described image forming apparatus, the toner carried on the toner carrying roller slides on the print head in the vicinity of the toner flow path to receive a mechanical force, thereby causing the toner carrying roller to contact the toner carrying roller. Freed from adhesion. Therefore, the passage of the toner through the toner flow path can be controlled with a small voltage. In addition, by arranging the print head and the toner on the toner carrying roller to be in contact with each other, the control electrode on the print head and the toner carrying roller are extremely close to each other, and a strong electric field can be obtained with a small voltage. This leads to high contrast being obtained with a small voltage.

Further, the image forming apparatus proposed in US Pat. No. 3,689,935 has a reference electrode continuous on one side with a plurality of insulating layers interposed on the other side with an insulator layer interposed therebetween. A control electrode, and further comprising a print head formed by forming at least one row of apertures through the three layers for each of the plurality of insulated control electrodes, wherein the control electrode and Means for selectively applying a potential to a reference electrode, and directing the charged toner particles toward the aperture such that the flow of the toner particles through the aperture is modulated by the potential applied to the control electrode. It comprises means for projecting, and means for positioning the recording medium in the particle flow path while relatively moving the recording medium and the print head.

In order to increase the density of pixel formation in this type of image forming apparatus, Japanese Patent Application Laid-Open No. 2-74359 discloses that at least two rows of apertures are arranged at equal column intervals and at equal aperture intervals. Propose a print head.

Japanese Patent Application Laid-Open No. 4-244865 proposes an image forming apparatus having means for moving a print head in the direction of an aperture row.

[0010]

However, in the image forming apparatus proposed in Japanese Patent Application Laid-Open No. 2-74359 for increasing the density of pixels to be formed, the aperture column width is increased. It is difficult to supply toner to the aperture simultaneously and evenly over
Since it is difficult to keep the distance between the print head and the recording medium constant, there is a drawback that uneven density occurs in the formed pixels.

Further, in the image forming apparatus proposed in Japanese Patent Application Laid-Open No. 4-244865, a lead screw is used to move a print head, so that the structure is complicated and the speed of sliding is limited. However, high-speed printing cannot be performed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has as its object to provide an image forming apparatus which can form a high-density image without density unevenness and has a simple structure. I have.

[0013]

In order to achieve this object, an image forming apparatus according to a first aspect of the present invention comprises a charged material flow control means having a charged material flow path and a control electrode; The present invention is directed to a device having a charged material carrying means for supplying to the charged material flow control means, and in particular, is provided with a resonance means for vibrating the charged material flow control means at a resonance frequency in a control electrode arrangement direction. . That is, the image forming apparatus having the above configuration controls the passage of the charged body supplied by the charged body holding unit by the charged body flow control unit excited at the resonance frequency by the resonance unit, and An image is formed by causing the charged body to fly on a recording medium located on the opposite side of the charged body flow control means with respect to the carrying means.

The image forming apparatus according to a second aspect of the present invention provides
The resonance means includes an elastic body provided on one end side of the charged body flow control means in the control electrode arrangement direction, and a vibrating means for applying vibration to the charged body flow control means via the elastic body. It is characterized by doing. That is,
The charged body flow control means vibrates at its unique resonance frequency when excited by the vibrating means via the elastic body.

Further, in the image forming apparatus according to the present invention, the elastic body has an elastic coefficient k corresponding to a vibration load m of the charged body flow control means and a resonance frequency f thereof.
Next formula

[0016]

(Equation 1)

It is characterized in that a material satisfying the condition is used. Therefore, the resonance vibration system of the charged body flow control means can be configured reliably and simply.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram showing the overall configuration of an image forming apparatus according to the present embodiment.
Is provided, and at the top of the toner supply device 10,
A print head 1 is provided as charged body flow control means for controlling toner flow. This print head 1
A back electrode roller 22 is rotatably disposed above the, with an interval of about 1 mm.

In the gap between the print head 1 and the back electrode roller 22, the rotation of the back electrode roller 22 in the direction of arrow D shown in FIG.
The recording medium 20 is moved by an arrow C shown in FIG.
A heat fixing device 26 including a pair of a pressure roller and a heating roller is disposed at the destination. The heat fixing device 26 can be replaced with any one of a heat fixing method and a pressure fixing method.

Next, the details of each component will be described. First, as shown in FIG. 1, the toner supply device 10 includes a toner case 11 serving as a housing of the entire device.
Is provided in the toner case 11, and preferably an insulating toner 16 as a charged body is accommodated.
Cylindrical toner carrying roller 1 for conveying toward
4 are provided. Incidentally, the toner carrying roller 14 constitutes the charged body carrying means of the present invention.

A diagonally lower left side of the toner carrying roller 14 in FIG. 1 is provided with a cylindrical supply roller 12 for feeding the toner 16 contained in the toner case 11 to the toner carrying roller 14. It is provided so as to be rotatable in the direction indicated by arrow A. The supply roller 12 and the toner carrying roller 14 are arranged in parallel with each other so that their cylindrical surfaces are pressed against each other.

In the toner case 11, above the supply roller 12, the amount of toner 16 carried by the toner carrying roller 14 is adjusted so as to be uniform on the roller surface of the toner carrying roller 14. A layer regulating blade 18 for uniformly charging the toner 16 is provided, and one end of the layer regulating blade 18 is pressed against the toner carrying roller 14.

The print head 1 has, for example, a thickness 2
It is composed of an insulating base 2 made of polyimide of about 5 μm, and the base 2 is provided with an aperture 6 as a charged body flow path of about 60 μm in diameter in the longitudinal direction of the print head 1 as shown in FIG. They are formed in a line. Around the aperture 6, a control electrode 4 made of a conductive metal pattern such as copper or gold having a thickness of about 5 μm is formed so as to surround the edge of each aperture 6.

The print head 1 is stuck on a support plate 17 provided with a slit, and is bent in a U-shape such that a row of the apertures 6 (hereinafter, simply referred to as aperture rows) becomes a bottom. , The U-shaped portion of which is passed through the slit. The base 2 is disposed at the bottom of the U-shape so that the base 2 contacts the toner 16 on the toner carrying roller 14.

The control electrode 4 of the print head 1
Each is connected to a drive element 8 such as C. The drive element 8 applies +30 V / 0 to the control electrode 4 based on an image signal sent from an image signal receiving unit (not shown).
It is configured to apply an ON / OFF voltage of V or + 30V / -30V. The image signal receiving means (not shown) is connected to an external computer, image reading device, image communication device, or the like.

Further, a DC power supply (not shown) is connected to the back electrode roller 22.
A voltage of +1 kV can be applied to each of the back electrode rollers 22.

Further, as shown in FIG.
The one end 7 is connected to a vibrating device 30 provided on a housing (not shown), and is held movably along a guide 37.

The vibrating device 30 includes a U-shaped iron core 33.
An electromagnet 35 as a vibrating means formed by winding a coil 34, a rubber plate 31 as an elastic body, and an iron piece 32, and the iron piece 32 is provided at one end of the support plate 17 in the aperture row direction. The iron core 33 is connected to the rubber plate 3
1 to excite the iron piece 32 and the support plate 17. The coil 34 is connected to an AC power supply (not shown).

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

First, when the supply roller 12 rotates in the direction of arrow A shown in FIG. 1, the toner 16 accommodated in the toner case 11 is
Conveyed toward. Then, the toner 16 supplied to the toner carrying roller 14 by the supply roller 12 is leveled by the layer regulating blade 18 to be carried as a thin and uniform toner layer and rubbed against the layer regulating blade 18. While being charged, it is charged to a predetermined polarity, here negative polarity (minus). Further, while the toner 16 thinned on the toner carrying roller 14 is carried on the toner carrying roller 14, the toner carrying roller 14
As it rotates in the direction, it is conveyed toward the print head 1.

The toner 16 having passed through the layer regulating blade 18 is guided between the toner carrying roller 14 and the print head 1 as the toner carrying roller 14 rotates. Then, the toner 16 on the toner carrying roller 14 is
Rolled by being sandwiched between the toner carrying roller 14 and the base 2 of the print head 1 and receiving sliding at this portion,
With the adhesive force with the toner carrying roller 14 reduced,
The print head 1 is supplied near the aperture row.

The control voltage is given as follows.

For example, in response to an image signal, the control drive element 8 applies +30 to the control electrode 4 corresponding to the image portion.
When a positive voltage of V is applied, an electric force directed from the control electrode 4 to the toner carrying roller 14 is generated near the aperture 6 corresponding to the control electrode 4 due to a potential difference between the control electrode 4 and the toner carrying roller 14. A line is formed. Thereby,
The negatively charged toner 16 receives electrostatic force in the direction of higher potential, and the toner 6 is
And is drawn out to the control electrode 4 side. The extracted toner 16 further flies toward the recording medium 20 by an electric field formed between the recording medium 20 and the aperture electrode body 1 by the high voltage of +1 kV applied to the back electrode roller 22. Then, they are deposited on the medium 20 to form dot-shaped pixels.

A negative voltage of 0 V or -30 V is applied from the driving element 8 to the control electrode 4 corresponding to the non-image portion. As a result, between the toner carrying roller 14 and the control electrode 4, the toner carrying roller 14
Is not formed, and the toner 16 cannot pass through the aperture 6. In addition, at this time, when a negative voltage of -30 V is applied, a voltage lower than that of the toner carrying roller 14 is applied to the control electrode 4, so that an electric field corresponding to the image portion is applied between them. , A reverse electric field is formed, and the passage of the toner 16 through the aperture 6 is effectively suppressed. Therefore, an image with less fog is formed.

During this time, the support plate 17 on which the print head 1 is mounted is vibrated by the vibrating device 30 at a constant period in the direction of the aperture row at an amplitude of half the aperture interval. Therefore, the predetermined control voltage is applied to the control electrode 4 in synchronization with the position of the aperture and the input image signal every half cycle of the vibration. As a result, pixels are formed at a half interval between adjacent apertures.

On the other hand, the recording medium 20 conveyed through the gap between the print head 1 and the back electrode roller 22 has a row of open apertures 6 while a row of pixels is formed by the toner 16 on its surface. Are sent for one pixel in the direction orthogonal to Then, by repeating the above process, a toner image is formed on the entire surface of the recording medium 20. After that, the toner image formed on the recording medium 20 is fixed on the recording medium 20 by the heat fixing device 26.

Here, the rubber plate 32 in the vibrating device 30 has the following equation, where the elastic constant k is the vibration frequency f, and the mass of the print head and the support plate is m.

[0039]

(Equation 1)

It is set so as to satisfy the following. With this configuration, the vibration resonates and a desired amplitude can be obtained at high speed.

The present invention is not limited to the embodiment described in detail above, and various changes can be made without departing from the gist of the present invention.

For example, in the above embodiment, an electromagnet is used as the vibration means, but a piezoelectric body may be used. Further, in the above embodiment, rubber is used as the elastic body, but this may be a spring.

Further, in the above-described embodiment, the print head having a circular aperture is shown. However, instead, the print head may be a rectangular aperture such as a triangle or a quadrangle. Hei 1-503
It is also possible to use a mesh-shaped electrode body as described in JP-A-221. Also, Japanese Patent Application Laid-Open No. 6-25516
The invention can be applied to an edge-shaped print head having no aperture, as described in Japanese Patent Application Laid-Open No. 3 (1993) -316.

[0044]

As is clear from the above description,
According to the image forming apparatus of the first aspect of the present invention, the charged body flow control means can be vibrated at a high speed, so that a formed image can be formed without density unevenness and high density.

Further, according to the image forming apparatus of the second aspect, a configuration in which the charged body flow control means is caused to resonate and vibrate at a high speed can be obtained with a simple apparatus configuration.

Further, according to the image forming apparatus of the third aspect, the resonance vibration system of the charged material flow control means can be reliably and simply configured, and even when fine adjustment of the vibration frequency is performed, the elasticity can be improved. Since the vibration system can be easily and quickly tuned by appropriately replacing the body with one having a different elastic modulus, even if the natural frequency changes due to the design change of the charged body flow control means, the resonance vibration system can be easily constructed. Can be formed.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a main part of a print head mounted on the image forming apparatus.

FIG. 3 is a perspective view illustrating a configuration of a main part of the image forming apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Print head 4 Control electrode 6 Aperture 14 Toner carrying roller 30 Vibration device 31 Rubber plate 35 Electromagnet

Claims (3)

[Claims] 1. A charged material flow control means having a charged material flow path through which a charged material passes, and a plurality of control electrodes arranged to control passage of the charged material, and the charged material flow control means. Charging means for supplying a charged substance to the charged substance flow means, wherein the passage of the charged substance supplied by the charged substance supporting means is controlled by the charged substance flow control means. An image forming apparatus for forming an image by flying a charged body on a recording medium located on the opposite side of a control unit, wherein the charged body flow control unit is vibrated at a resonance frequency in the control electrode arrangement direction. An image forming apparatus comprising: 2. The method according to claim 1, wherein the resonance means includes an elastic body provided at one end of the charged body flow control means in the control electrode arrangement direction, and a vibration applying means for applying vibration to the charged body flow control means via the elastic body. The image forming apparatus according to claim 1, further comprising: a vibration unit. 3. The elastic body has an elastic coefficient k:
Vibration load m of charged body flow control means and its resonance frequency f
For the following equation: The image forming apparatus according to claim 2, wherein the image forming apparatus satisfies the following.