JP2520512B2 - Image forming device - Google Patents

Description

The present invention relates to an image forming apparatus using powder toner.

(Prior Art) For word processors, facsimile machines, computers and the like, an image forming method using an ink jet printer is known.

Ink jet printers are typical of so-called non-impact printers.
By applying pressure while applying ultrasonic vibration by a piezoelectric element or the like, the liquid ink is ejected from an ink nozzle within a predetermined electric field, and the ink particles are controlled by the electric field to adhere to recording paper, thereby forming a recorded image. Is formed on the recording paper. In such an ink jet printer system,
There is an advantage that no noise is generated when forming an image and a clear image can be formed. On the other hand, in order to control the speed at which ink permeates the recording paper, it is necessary to use special paper that has undergone surface treatment, etc., and since ink is supplied from the nozzle, the nozzle has foreign matter inside the ink. There is a problem that it is easily clogged due to factors such as.

In order to solve the problem of such an ink jet printer, an image forming apparatus using powder toner as an image recording medium is disclosed in, for example, Japanese Patent Laid-Open No. 62-263962. This image forming apparatus is provided with toner control means for controlling powder toner particles to pass through a pinhole-shaped toner passage hole by electrostatic attraction generated in response to an image output signal. By the toner control means,
Toner particles are selectively fed onto the conveyed recording paper,
A predetermined recording image is formed on the recording paper. In such an apparatus, plain paper which has not been subjected to surface treatment or the like can be used as recording paper, and since fine particle powder toner is used, clogging of toner in each toner passage hole is suppressed. .

The toner control means for controlling the powder toner is provided with an insulating substrate provided with a large number of pinhole-shaped toner passage holes, and the insulation substrate interposed so as to form an electric field in each toner passage hole. And a pair of electrodes provided. Each pair of electrodes is provided with a through hole similar to each toner passage hole, and is attached to one surface of the insulating substrate with each through hole aligned with each toner passage hole. ing.

Then, by applying a predetermined voltage between both electrodes to form an electric field in a predetermined direction in the toner passage hole, the toner particles pass through the toner passage hole. To prevent the toner particles from passing through the toner passage holes, a predetermined voltage is applied between the electrodes so that an electric field in the opposite direction to that when toner particles are passed is formed in the toner passage holes. To be done.

(Problems to be Solved by the Invention) By the way, in an image forming apparatus using this type of powder toner, if an efficient image recording operation is performed by increasing the conveying speed of recording paper (paper), It is necessary to increase the toner supply amount by an amount commensurate with the increase in the recording paper conveyance speed. That is, otherwise, the amount of toner supplied per unit area of the recording paper will decrease, and the image density will decrease.

There is

However, in the above-mentioned conventional example, due consideration has not been given to this point, and it has not been enough to overcome the decrease in image density.

The present invention solves the above-mentioned problems of the prior art, and an image capable of increasing the toner supply amount with a simple configuration, resulting in efficient image recording without impairing the image quality. An object is to provide a forming device.

(Means for Solving the Problem) The image forming apparatus of the present invention includes a toner control unit having a pair of electrodes for forming an electric field in the toner passage hole on both surfaces of a substrate having the toner passage hole, and the toner control unit. A toner holding hole for communicating with the passage hole for retaining the toner during non-toner supply, and an insulator arranged outside the toner supply side electrode of the toner control means. The above object is achieved by the above.

Preferably, an electrode is provided outside the insulator, and AC and / or between the electrode and the toner supply side electrode.
Apply DC bias voltage.

(Function) As described above, the insulator having the hole for holding the toner, which communicates with the toner passage hole and retains the toner when the toner is not supplied, is provided outside the electrode on the toner supply side, and the insulator is provided between the pair of electrodes. When a voltage is applied to the toner to form an electric field in the direction opposite to the toner passage direction, the toner returns to the toner supply side in the toner passage hole, and due to the electric field at this time, stays in the insulator hole. Retained. Therefore, when the polarity of the voltage applied between the pair of electrodes is reversed from this state to form an electric field in the toner passage direction, the toner in the staying state is supplied, so that the toner supply amount can be increased.

The toner supply period is 5% to 30% of the total period.
Since it is only about a certain amount, it is possible to secure a necessary and sufficient amount of staying toner in the holes of the insulator.

In addition, AC in the toner passing direction and / or between the electrode provided outside the insulator and the electrode on the toner supply side
Applying a DC bias voltage accelerates the toner passing operation.

(Example) Hereinafter, the Example of this invention is described.

As shown in FIG. 1, the image forming apparatus of the present invention has a toner container 10 in which toner is sequentially replenished from a toner hopper or the like. An opening 11 is provided at the bottom of the toner container 10.
Is provided, and the upper portion of the toner supply roller 12, which is toner supply means, is fitted into the opening 11. As the toner supply roller 12, a sponge roller is used in which a sponge layer 14, which is an elastic insulator, is attached to the outer peripheral surface of the roller portion 13. Below the toner supply roller 12, a toner control means 20 is arranged in a horizontal state in the vicinity of the toner supply roller 12. An image signal is given to the toner control means 20 from the image information generation means 40.

The image information generating means 40 operates in response to a signal from a device body such as a word processor, a facsimile, a computer or the like, and generates a pulse voltage signal corresponding to the image information. According to this voltage signal, the powder toner charged from the toner supply roller 12 to a predetermined polarity is transferred by the toner control means 20 to the recording paper 60 arranged below the toner control means 20. Supply and non-supply are controlled. As a result, a predetermined toner image T is formed on the recording paper 60.
Is formed. The toner control means 20 may be in pressure contact with the toner supply roller 12. A base electrode 50 is provided below the toner control means 20 so as to face the toner control means 20.

The recording paper 60 on which the toner image T is formed on the base electrode 50
Is placed. The base electrode 50 may be moved together with the recording paper 60 to be placed in the direction indicated by the arrow A, or the base electrode 50 may be fixed and only the recording paper 60 may be moved by a predetermined recording paper conveying means. You may allow it.
A predetermined toner image T is recorded on the recording paper 60 by the toner control means 20.
When formed on the recording paper 60, the recording paper 60 is conveyed to a predetermined fixing device (not shown), and the toner image T is fixed on the recording paper 60 by the fixing device.

In addition, the toner control means 20 has an ultrasonic vibration generating means 30
Is provided. The ultrasonic vibration generating means 30 applies ultrasonic vibrations to the toner control means 20, whereby the toner control means 20
The toner supplied to the pinhole-shaped toner passage hole 22 (see FIG. 2) formed in the above is crushed, and the toner is decomposed into particle units and allowed to pass. As the ultrasonic vibration generating means 30, a piezoelectric element such as PZT is used.

Next, details of the toner control unit 20 will be described with reference to FIG. The toner control means 20 to which, for example, the negatively charged toner T ′ is supplied from the toner supply roller 12, is a horizontal insulating substrate 21 having a pinhole-shaped toner passage hole 22.
And control electrodes 23 and 24 provided on both upper and lower surfaces of the insulating substrate 21. The control electrode 23 on the upper surface side is a common electrode, and the control electrode 24 on the lower surface side is provided for each toner passage hole 22.

In addition, an insulator 25 having a hole 26 communicating with the toner passing hole 22 is provided on the upper surface side of the control electrode 23.
The insulator 25 is close to the toner supply roller 12 or is in pressure contact therewith.

The above-mentioned pulsed voltage signal is applied from the image information generating means 40 to the pair of upper and lower control electrodes 23, 24. The image information generating means 40 generates the voltage signal based on the image information, and applies, for example, a voltage of +100 V to the control electrode 24 for a predetermined time corresponding to the pulse width as an image forming signal for forming an image, and both electrodes 23 Set the potential between 24 and 100 to 100V. Therefore, at this time, an electric field from the control electrode 24 to the control electrode 23 is formed in the toner passage hole 22, and the toner T ′ in a negatively charged state falls in the toner passage hole 22 due to the electric field and is directed toward the recording paper 60. Fly and adhere.

It should be noted that applying a positive bias voltage to the base electrode 50 with respect to the common electrode 23 is preferable for implementation. That is, in this way, the toner T ′ that has passed through the toner passage hole 22 is attracted to the base electrode 50 and its fall is promoted.

On the other hand, during non-image formation, the control electrode 24 has a -10
A voltage of 0 V is applied, whereby an electric field in the opposite direction to the above is formed in the toner passage hole 22, and the toner T'returns to the control electrode 23 side. The returned toner T ′ is retained and retained in the hole 26 of the insulator 25. This retention is maintained at this time by the lines of electric force 41, 41 generated in the toner passage hole 22. As described above, the supply period of the toner T'is about 5% to 30% of the entire period. So it needs to be in hole 26 of insulator 25,
In addition, a sufficient amount of toner T'is secured. Therefore, if a voltage of +100 V is applied to the control electrode 24 from this state and the toner supply is restarted, the amount of toner T'attached, that is, the image density can be improved. Therefore, it is possible to cope with an increase in the conveyance speed of the recording paper 60.

FIG. 3 shows another embodiment of the present invention. In this embodiment, an insulator 25 and a control electrode 27 are attached in this order on the upper surface side of the control electrode 23, and the control electrode 27 and the control electrode are attached. An AC bias voltage is applied between the AC bias power supply 70 and the AC line 23. According to this structure, the dropping speed of the toner T ′ staying in the hole 26 of the insulator 25 can be improved when the toner is supplied, so that more efficient image recording can be performed. Further, clogging of the toner T'can be prevented, and stable image recording can be performed.

In the embodiment shown in FIG. 4, instead of the AC bias power source 70, a DC bias power source 71 is connected between the control electrodes 23 and 27, and a DC bias voltage is applied between the control electrodes 23 and 27 to apply toner to the toner. It is configured to promote the fall of the toner T ′ during the supply.

According to this embodiment, there is an advantage that the falling speed of the toner T'can be further improved as compared with the case of the other embodiments.

Furthermore, it is possible to adopt a configuration in which an AC bias power source 70 and a DC bias power source 71 are connected between the control electrodes 23 and 27 to apply an AC bias and a DC bias at the same time.

In the present invention described above, it is desirable to use a toner having a relatively small average particle diameter of 5 to 20 μm, and an image having excellent resolution can be formed by the toner having a small diameter.

The distance between the toner control means 20 and the recording paper 60 varies depending on the magnitude of the applied voltage applied from the image information generating means 40, but is usually in the range of 0.3 to 2.5 mm.

In this embodiment, a sponge roller is used as the toner supply roller 12. The sponge roller effectively crushes the aggregated toner in the toner container 10 as the sponge roller rotates,
Since the toner is held in the joints on the surface in a substantially uniform state, the toner control unit 20 is always supplied with a constant amount of toner.

(Effects of the Invention) According to the present invention described above, when toner is not supplied, the toner is retained by being retained in the toner passage hole, and when toner is supplied, necessary and sufficient toner including the accumulated toner is supplied. Therefore, the toner supply amount can be increased.
Therefore, it is possible to cope with the speeding up of the sheet conveying speed, it is possible to perform efficient image recording, and it is possible to improve the image density.

Further, particularly according to the image forming apparatus of the second aspect, by applying the bias voltage in the toner passing direction, the toner supply speed at the time of toner supply can be improved, the toner is not clogged, and a stable image is obtained. There is an advantage that it can be recorded.

[Brief description of drawings]

FIG. 1 is a drawing showing an embodiment of an image forming apparatus of the present invention, FIG. 2 is an enlarged view of the essential parts thereof, FIG. 3 and FIG.
The drawings are drawings showing another embodiment of the present invention. 20 ... Toner control means, 21 ... Insulating substrate, 22 ... Toner passage hole, 23, 24, 27 ... Control electrode, 25 ... Insulator, 26 ... Hole, 40 ... Image information generating means, 70 …… AC bias power supply, 71 …… DC bias power supply.

Claims (2)

(57) [Claims] 1. A substrate having toner passage holes formed on both sides thereof,
Toner control means having a pair of electrodes forming an electric field in the toner passage hole, and a toner holding hole communicating with the toner passage hole for retaining toner when non-toner is supplied, the toner of the toner control means An image forming apparatus comprising: an insulator provided outside an electrode on the supply side. 2. An electrode is provided outside the insulator, and AC and / or DC is provided between the electrode and the toner supply side electrode.
The image forming apparatus according to claim 1, wherein the bias voltage is applied.