JPH08314242A - Image forming device - Google Patents

Abstract

(57) [Summary] An image forming apparatus is provided so as to face a toner carrier 10 carrying a charged toner 12 and the toner carrier 10, and a predetermined voltage is applied between the toner carrier 10. Counter electrode 11 to which is applied, and the toner carrier 10 described above.
And a counter electrode 11, which are provided between the counter electrode 11 and the counter electrode 11 and selectively control the flying of the charged toner 12 to the recording medium in the toner flying area based on the applied voltage, and the recording medium in the toner flying area. Provided on the upstream side in the transport direction,
And a static eliminator 4 for removing the charged electric charge on the recording medium. [Effect] Since the charged charges on the recording medium are removed before the recording medium is conveyed to the toner flying area, it is possible to prevent the recording medium from rising from a predetermined position. As a result, the recording medium receives the flying of the charged toner at the original predetermined position on the counter electrode, so that the dots of the prescribed size are formed without the flying toner diffusing, and a high-quality image can be formed. .

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 for selectively flying charged toner to form an image on a recording medium.

[0002]

2. Description of the Related Art In a conventional image forming apparatus such as a copying machine (referred to as "first prior art"), a developer is charged by a charger, and then a document is irradiated with light from an optical system. The light reflected by the document is guided to the image developer, and the image developer is exposed. At this time, the electrostatic charges in the light-irradiated portion are removed and an image is formed on the image developer, whereby an electrostatic latent image corresponding to the original image is formed on the image developer. The charged toner in the developing device is attracted toward the electrostatic latent image, and the electrostatic latent image is developed. As a result, the electrostatic latent image is visualized as a toner image on the developer. When the image developer is charged by the transfer device (the recording medium (copy material) is charged), the toner image on the image developer is transferred onto the recording medium. Then, this recording medium is separated from the image developer, conveyed to the fixing section, and the toner image is fixed on the recording medium, and the image formation is completed. By the way, the residual toner on the image developer which has not been transferred onto the recording medium is removed. In addition, the above electrostatic latent image is
It is erased by being irradiated with light from the static eliminator.

In the configuration of the first prior art described above, it is necessary that the image developer itself has a special structure for forming an electrostatic latent image, and the electrostatic latent image is formed on the image developer. It is necessary to separately provide means for this. Therefore, the image forming apparatus has problems in terms of downsizing and stability. In addition, when the developer is repeatedly used, in addition to the electrostatic latent image forming means, it is necessary to separately provide means for erasing the electrostatic latent image previously formed, and the above transfer processing is also required. Met.

In order to solve the above problem, a control electrode controlled according to an image signal is used, and when the recording medium passes through a toner flying region, charged toner particles (visualizing particles) are recorded. An apparatus (referred to as a second related art) that forms a toner image on a recording medium by directly and selectively flying the toner onto the recording medium has been proposed (for example, Japanese Patent Laid-Open No. 1-5).
No. 03221). According to this, since the image developer is not used, the configuration and the process are simplified, and the size and stability of the apparatus are significantly improved.

[0005]

According to the second prior art described above, the charged toner particles are directly and selectively ejected onto the recording medium via the control electrode in the toner ejection area.
The charged toner particles fly from the toner carrier to the counter electrode along the lines of electric force based on the electric field in the toner flying region. At this time, the control electrode is controlled in accordance with the image signal so that the charged toner particles reach the recording medium at a predetermined position between the toner carrier and the counter electrode, and the electric force lines are recorded on the recording medium. Converge. As a result, dots of a predetermined size are formed on the recording medium, and an image is formed.

However, the recording medium is generally charged by friction with other members during transportation. Therefore, in the toner flying area, the charged recording medium is subjected to the Coulomb force due to the electric field in the area, and thus the charged recording medium is lifted from the predetermined position. As described above, in the second conventional technique, when the recording medium floats in the toner flying area, the lines of electric force reach the recording medium before they converge and do not converge at the original convergence point (on the recording medium). . For this reason, when the toner reaches the recording medium, the toner is diffused, and dots larger than the dots of the predetermined size are formed on the recording medium, so that it is impossible to form a high-quality image. There is.

According to the first prior art described above, since the charged toner is attracted to the electrostatic latent image by the strong electric field to be developed, even if the recording medium is charged,
This electrostatic charge does not affect the image formation.

[0008]

An image forming apparatus according to the invention of claim 1 is characterized in that the following means are provided to solve the above-mentioned problems.

That is, the image forming apparatus includes a toner carrier that carries charged toner, and a counter electrode that is provided so as to face the toner carrier and to which a predetermined voltage is applied between the toner carrier and the toner carrier. A control electrode provided between the toner carrier and the counter electrode for selectively controlling the flight of the charged toner to the recording medium in the toner flying area based on the applied voltage, and the recording medium in the toner flying area. And a charge removing unit that is provided on the upstream side in the transport direction to remove the charged charges on the recording medium.

An image forming apparatus according to a second aspect of the present invention is characterized in that the following means are provided to solve the above problems.

That is, the image forming apparatus includes a toner carrier that carries a charged toner, and a counter electrode that is provided so as to face the toner carrier and that is applied with a predetermined voltage between the toner carrier and the counter electrode. A control electrode that is provided between the toner carrier and the counter electrode and that suppresses the flying of the charged toner to the recording medium that has been transported to the toner flying region according to the applied voltage, and the recording medium transport of the toner flying region. And a charge removing unit that is provided on the upstream side in the direction to remove the charged electric charge on the recording medium.

In order to solve the above-mentioned problems, an image forming apparatus according to a third aspect of the present invention is characterized in that, in the image forming apparatus according to the first or second aspect, the discharging means is a corona charger.

An image forming apparatus according to a fourth aspect of the present invention is characterized in that the following means are provided to solve the above problems.

That is, the image forming apparatus includes a toner carrier that carries charged toner, and a counter electrode that is provided so as to face the toner carrier and that is applied with a predetermined voltage between the toner carrier and the counter electrode. A control electrode provided between the toner carrier and the counter electrode for selectively controlling the flight of the charged toner to the recording medium in the toner flying area based on the applied voltage, and the recording medium in the toner flying area. A semi-conductive member provided on the upstream side in the transport direction and provided so as to come into contact with the transported recording medium, and a predetermined alternation with respect to the semi-conductive member so as to remove the electrostatic charge on the recording medium. And means for applying a voltage.

In order to solve the above-mentioned problems, an image forming apparatus according to a fifth aspect of the present invention is the image forming apparatus according to the fourth aspect, characterized in that the semiconductive member is a conductive elastic member.

In order to solve the above-mentioned problems, an image forming apparatus according to a sixth aspect of the present invention is the image forming apparatus according to the fourth aspect, characterized in that the semiconductive member is a brush-like member.

An image forming apparatus according to a seventh aspect of the present invention is characterized in that the following means are provided to solve the above problems.

That is, the image forming apparatus includes a toner carrier that carries a charged toner, and a counter electrode that is provided so as to face the toner carrier and that is applied with a predetermined voltage between the toner carrier and the counter electrode. A control electrode provided between the toner carrier and the counter electrode for selectively controlling the flight of the charged toner to the recording medium in the toner flying area based on the applied voltage, and the recording medium in the toner flying area. A first recording medium conveying means is provided on the upstream side in the conveying direction and conveys the recording medium, and a first recording medium conveying means is provided on the downstream side in the recording medium conveying direction of the toner flying area and the recording medium passing through the toner flying area. And a second recording medium conveying unit that conveys the recording medium further downstream at a higher speed.

In order to solve the above-mentioned problems, an image forming apparatus according to an eighth aspect of the present invention is the image forming apparatus according to the seventh aspect, characterized in that the second recording medium conveying means is a fixing roller.

[0020]

According to the structure of claim 1, an electric field corresponding to the applied predetermined voltage is generated between the toner carrier and the counter electrode, and the recording medium is conveyed to the toner flying area. Then, the flying of the charged toner from the toner carrier to the counter electrode is controlled based on the voltage applied to the control electrode. Since the recording medium is conveyed on the counter electrode, the flying charged toner reaches the recording medium and an image is formed.

As the recording medium is conveyed to the toner flying area, charged electric charges due to friction or the like are formed on the surface. This electrostatic charge is subjected to a force by the electric field between the toner carrier and the counter electrode. When the recording medium is not charged, the recording medium receives the flying of the charged toner at the original predetermined position on the counter electrode, so that the flying toner does not diffuse and a dot of a prescribed size is formed, and the desired image is formed. The formation takes place. However, when the recording medium receives a force from the electric field so as to be separated from the counter electrode, the recording medium floats above the counter electrode. In this state, the recording medium cannot receive the flying of the charged toner at the original predetermined position on the counter electrode, the flying toner diffuses, dots of a prescribed size are not formed, and a prescribed resolution cannot be obtained. .

However, according to the structure of claim 1,
Even if the recording medium is charged while being conveyed to the toner flying area, the charge on the recording medium reaches the toner flying area on the upstream side in the conveying direction and is removed by the static eliminating means. Never receive. In this way, the recording medium does not receive the flying of the toner in the floating state, and a high quality image is formed.

According to the structure of claim 2, an electric field corresponding to the applied predetermined voltage is generated between the toner carrier and the counter electrode, and the recording medium is conveyed to the toner flying area. And based on the voltage applied to the control electrode,
The flying of the charged toner from the toner carrier to the counter electrode is suppressed. That is, based on the voltage applied to the control electrode, the flying of the charged toner that does not contribute to the image formation is suppressed, while only the charged toner that contributes to the image formation flies toward the counter electrode. Then, when the recording medium is conveyed on the counter electrode, the charged toner that contributes to the image formation in which the flight is not suppressed reaches the recording medium, whereby
The desired image is formed.

At this time, even if the recording medium is charged while it is being conveyed to the toner flying area, the electrostatic charge on the recording medium is removed by the discharging means on the upstream side in the conveying direction and reaches the toner flying area. The recording medium does not receive any force from the electric field. In this way, the recording medium does not receive the flying of the toner in the floating state, and a high quality image is formed.

According to the third aspect of the present invention, since the static elimination is performed by the corona charger in a non-contact manner, the recording medium is conveyed to the toner flying area in the same manner as the operation according to the first or second aspect. Even if it is charged, the charge on the recording medium is removed by the corona charger on the upstream side in the transport direction and reaches the toner flying area, so that the recording medium is not subjected to a force from the electric field. In this way, the recording medium does not receive the flying of the toner in the floating state, and a high quality image is formed.

According to the structure of claim 4, an electric field corresponding to the applied predetermined voltage is generated between the toner carrier and the counter electrode, and the recording medium is conveyed to the toner flying area. And based on the voltage applied to the control electrode,
The flight of the charged toner is controlled from the toner carrier to the counter electrode.

At this time, even if the recording medium is charged while being transported to the toner flying area,
Since a predetermined alternating voltage is applied through the semi-conductive member that is in contact with the recording medium, the charge on the recording medium is removed. In this way, the recording medium is
The recording medium does not receive a force from the electric field because it reaches the toner flying area after the charge is removed. Therefore, the recording medium does not receive the flying of the toner in the floating state, and a high quality image is formed.

According to the fifth aspect of the invention, even if the recording medium is charged while being conveyed to the toner flying area, a predetermined amount is provided on the upstream side in the conveying direction via the conductive elastic member that is in contact with the recording medium. Since the alternating voltage is applied, the charge on the recording medium is removed. As described above, even if the recording medium is charged during the conveyance, the recording medium reaches the toner flying area after the charge is removed, and therefore the recording medium is not subjected to the force from the electric field. Therefore, the recording medium does not receive the flying of the toner in the floating state, and a high quality image is formed.

According to the sixth aspect of the present invention, even if the recording medium is charged while being conveyed to the toner flying area, a predetermined alternation is provided on the upstream side in the conveying direction via the brush-like member that is in contact with the recording medium. Since the voltage is applied, the charge on the recording medium is removed. As described above, even if the recording medium is charged during the conveyance, the recording medium reaches the toner flying area after the charge is removed, and thus the recording medium does not receive the force from the electric field. Therefore, the recording medium does not receive the flying of the toner in the floating state, and a high quality image is formed.

According to the structure of claim 7, an electric field corresponding to the applied predetermined voltage is generated between the toner carrier and the counter electrode, and the recording medium is conveyed to the toner flying area. And based on the voltage applied to the control electrode,
The flight of the charged toner from the toner carrier to the counter electrode is controlled. Since the recording medium is conveyed on the counter electrode,
The flying charged toner reaches the recording medium and an image is formed.

As the recording medium is conveyed to the toner flying area, charged electric charges due to friction or the like are formed on the surface thereof, and the recording medium is lifted by receiving a force by the electric field between the toner carrier and the counter electrode.

However, according to the above arrangement, the second recording medium conveying means conveys the recording medium to the downstream side of the toner flying area at a speed higher than that of the first recording medium conveying means, so that the mechanical tension on the recording medium is increased. Is given. Due to this tension, even if the recording medium is charged while being conveyed to the toner flying area, it is not affected by the force applied from the electric field. In this way, the recording medium does not receive the flying of the toner in the floating state, and a high quality image is formed.

According to the structure of claim 8, in addition to the operation according to claim 7, the fixing roller also serves as the second recording medium conveying means, so that it is possible to save space and reduce cost.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

As shown in FIGS. 1 and 2, the image forming apparatus according to the present embodiment can mainly store a recording medium 2 such as copy paper of various sizes and can be attached to and detached from the main body of the image forming apparatus. A paper feed tray 1, a supply roller 3 for supplying the recording medium in the paper feed tray 1 to a conveyance path in the image forming apparatus main body from the top, and a recording medium 2 supplied by the supply roller 3 in the image forming apparatus main body. A supply sensor 5 that detects that the recording medium 2 has been conveyed, a registration roller 7 that temporarily stops the conveyed recording medium 2, and a toner that is charged and charged (hereinafter, referred to as a charged toner). A developing device 20 having a toner carrier 10 carrying 12 on the surface thereof is provided so as to face the toner carrier 10, a predetermined voltage is applied between the toner carrier 10 and the print head 8. Charged toner 1 flies with near-field
Plate-like counter electrode 11 for stabilizing the direction 2
And a plurality of control electrodes 13 provided between the toner carrier 10 and the counter electrode 11 for selectively controlling the flight of the charged toner 12 to the recording medium 2 in the toner flight area based on the applied voltage. The print head 8 included therein, the fixing unit 9 that fixes the charged toner 12 flying on the recording medium 2 by pressing and / or heating, and the recording medium 2 that has been fixed are guided to the discharge tray 15 outside the main body of the image forming apparatus. Discharge roller 1
4, a discharge sensor 16 provided above the one end of the discharge tray 15 on the upstream side in the transport direction, for detecting whether or not the recording medium 2 is properly discharged to the discharge tray 15, and the image forming apparatus are comprehensively controlled. Control unit 6 for

In the present embodiment, the toner flying area is between the toner carrier 10 and the counter electrode 11,
It means an area in which the charged toner 12 flies toward the recording medium 2 via the print head 8.

In the image forming apparatus, the registration roller 7 is provided on the upstream side of the toner flying area in the conveying direction of the recording medium 2.
A static eliminator 4 that removes the electric charge on the recording medium 2 is further provided between the counter electrode 11 and the counter electrode 11.

The recording medium 2 is charged by friction or the like during its transportation. Specifically, when the recording medium 2 is supplied to the conveyance path by the supply roller 3, the recording media 2 rub against each other in the paper feed tray 1, and when the supply roller 3 supplies the recording medium 2 to the conveyance path. 3 by being contacted, contacting the registration roller 7 when the registration roller 7 is once stopped, and contacting with a resin or the like that constitutes a conveyance path leading to the registration roller 7 during conveyance, etc. To do. Of these, the above is the main cause of charging of the recording medium 2.

When the supply sensor 5 detects that the recording medium 2 is supplied into the main body of the image forming apparatus by the supply roller 3, it sends a signal to that effect to the control unit 6. Upon receiving this signal, the control unit 6 starts generating an image signal to be printed based on an instruction from a host computer (not shown). The control unit 6 converts the image data to be printed into an electric signal and supplies the electric signal to the print head 8 having the control electrode 13 built therein. After this conversion, the control unit 6 rotates a motor (not shown) that drives the registration roller 7 to start the conveyance of the recording medium 2 to the print head 8. Recording medium 2 before printing
, The static charge accumulated on both surfaces is removed by the static eliminator 4.

Here, a case will be described below as the structure of the static eliminator 4 in which a predetermined alternating voltage is applied to a member provided in contact with the conveyed recording medium 2.

First, a case where the above-mentioned static eliminator 4 is made of a conductive elastic member will be described with reference to FIGS. 1 and 3. The static eliminator 4 is composed of a pair of rollers 4a and 4b as shown in FIG.
As shown in FIG. 3, the roller member 18 (semi-conductive member / conductive elastic member) and the cored bar 19 that is longer than the roller member 18 in the axial direction and penetrates the roller member 18 are formed. The cored bar 19 is axially supported by a bearing (not shown) and is also supported by a spring (not shown).
Has been pressed. A predetermined alternating voltage (described later) is applied to the cored bar 19 by a voltage applying means (not shown). Since the roller 4b is basically the same as the roller 4a, detailed description thereof will be omitted.

The roller member 18 has a uniform resistance value, for example, by mixing carbon black into a rubber sponge whose base material is silicon. That is, the roller member 18 has a volume resistivity of 10 ⁷ Ω · cm to 10 ¹⁰ Ω ·
It consists of a cm conductive elastic member (also a semi-conductive member).

When the recording medium 2 is conveyed to the position of the static eliminator 4, the control unit 6 controls the voltage applying means,
An alternating voltage is applied to the cored bar 19 to start static elimination. As the voltage applying means, for example, in 1.5 kV _PP to 2 kV _PP, 200 Hz to 3
One that can output a sine wave voltage rated at 00 Hz is included. The reason why the alternating voltage is applied instead of the DC voltage at the time of static elimination is to set the charging potential of the static elimination target to 0 V (for uniformization and stabilization of static elimination). The output voltage and frequency of the voltage applying means are determined in consideration of the fact that the amount of charged electric charge varies depending on the type and size of the recording medium 2. The waveform is not limited to the sine waveform, and may be, for example, a rectangular waveform or a triangular waveform.

The timing for starting the charge removal may be determined based on, for example, the transport speed of the recording medium 2. That is, after the recording medium 2 is temporarily stopped by the registration roller 7,
The static elimination may be started after a predetermined time has elapsed.
The predetermined time period is determined by dividing the distance between the static eliminator 4 and the registration roller 7 by the conveyance speed of the recording medium 2 because the conveyance speed of the recording medium 2 is determined for each image forming apparatus.

In addition, the static eliminator 4 is provided in the conveyance path of the recording medium 2.
The static elimination may be started after detecting that the recording medium 2 has passed through the predetermined position by the detection means provided at the predetermined position before.

The case where the static eliminator 4 is composed of the roller member 18 which is a conductive elastic member has been described above, but the present invention is not limited to this, and instead of the roller member 18, The same action and effect can be obtained even if the recording medium 2 is constituted by a pair of semiconductive members provided so as to contact both sides of the recording medium 2.

The static eliminator 4 is composed of the roller member 18
Alternatively, as shown in FIG. 4, a pair of brush-like members may be used. The resistance value of the entire brush is 10 ³ Ω to 10 ⁵ Ω.

When the static eliminator 4 is composed of a semi-conductive member or a brush-like member, the voltage applied to the static eliminator 4 and the electrical ratings such as frequency, the voltage application timing, and the like are the same as the roller member 18 described above. Since it is the same as the case, detailed description will be omitted.

The static eliminator 4 may be constituted by a corona charger using corona discharge, as shown in FIG. In this case, the wire of the corona charger is, for example, 1.5k
Alternating voltage of V _PP to 2 kV _PP are applied. The application time varies depending on the length of the recording medium 2 in the transport direction, but is applied during the passage of the recording medium 2 through the charge removal position.

Here, the place where the static elimination processing is performed will be described. The charge removal process is performed before the recording medium 2 passes through the print head 8. However, in order to avoid recharging due to friction after charge removal, the voltage applied to the charge remover 4 is applied to the electric field existing in the toner flying area. It is preferable to carry out the static elimination processing at a position as close as possible to the print head 8 within a range that does not have an influence. Note that recharging due to friction or the like after static elimination can be avoided by configuring so that the conveyance path of the recording medium 2 does not cause friction (for example, even if the recording medium 2 comes into contact with the recording medium 2 during conveyance). This can be avoided by constructing the transport path with a conductive member that does not charge).

After the static elimination process is completed, the control unit 6 supplies the print head 8 with an electric signal corresponding to the image data to be printed. The print head 8 applies a voltage based on this electric signal (polarity, voltage value changes according to the electric signal) to the control electrode 13 inside the print head 8 to control the electric field near the print head 8. In this case, a configuration may be adopted in which a voltage is applied to the control electrode 13 to cause the charged toner to fly, or a voltage is applied to the control electrode 13 to suppress the fly of the charged toner.

According to the structure of this embodiment, the toner carrier 1
An electric field corresponding to the applied predetermined voltage is generated between 0 and the counter electrode 11, and when the recording medium 2 is conveyed to the toner flying area, the electric field based on the voltage applied to the control electrode 13 is generated. Thus, the flight of the charged toner 12 from the toner carrier 10 to the counter electrode 11 is controlled. Since the recording medium 2 is conveyed on the counter electrode 11, the flying charged toner 12 reaches the recording medium 2 and an image is formed.

While the recording medium 2 is being conveyed to the toner flying area, the charged electric charge due to friction or the like is formed on the surface thereof as described above. This electrostatic charge is due to the toner carrier 1.
A force is applied by the electric field between the 0-opposing electrode 11. If the recording medium 2 is not charged, the recording medium 2 is
Since the charged toner 12 flies at the original predetermined position, dots of a prescribed size are formed (see FIG. 6) and the desired image is formed without the flying toner diffusing.

However, when the recording medium 2 receives a force from the electric field so as to be separated from the counter electrode 11, the recording medium 2 is lifted from the counter electrode 11. In this state, the recording medium 2 cannot receive the flying of the charged toner 12 at the original predetermined position on the counter electrode 11, the flying toner is diffused, and dots of a prescribed size are not formed (see FIG. 7). , The specified resolution cannot be obtained.

However, according to the above configuration, even if the recording medium 2 is charged while being conveyed to the toner flying area, the charge eliminator 4 removes the charge on the recording medium 2 on the upstream side in the conveying direction. After reaching the toner flying area, the recording medium 2 does not receive any force from the electric field.
In this way, the recording medium 2 does not receive the flying of the toner in the floating state, and a high quality image is formed.

The recording medium 2 on which the image is formed by the charged toner 12 is conveyed as it is and reaches the fixing section 9, and the fixing section 9 applies pressure, heat, or both pressure and heat.
As a result, the toner melts and is fixed on the recording medium 2. The recording medium 2 thus fixed is conveyed and discharged to the discharge tray 15 via the discharge roller 14. At this time, the ejection sensor 16 detects whether or not the recording medium 2 is properly ejected to the ejection tray 15, and the detection result is sent to the control unit 6. Thereby, the control unit 6 determines whether or not the printing operation is properly completed, and when it is determined to be appropriate, the printing operation is completed.
If it is determined to be improper, the user is notified to that effect.

FIG. 8 shows another embodiment of the present invention.
9 and FIG. 9 will be described below. It should be noted that members having the same functions as those in the above-described embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

In the image forming apparatus of this embodiment, as shown in FIG. 8, the static eliminator 4 is not provided, and the recording medium transporter 28 (second recording medium transporting means) located downstream of the toner flying area. 1 and that the conveyance speed of the recording medium 2 in the recording medium conveyer 28 is faster than that in the registration roller 7 (first recording medium conveyer).

The recording medium transporter 28 and the registration roller 7 will be described below with reference to FIG.

Recording medium conveyer 28 and registration roller 7
Are both supported by bearings (not shown) and pressed against the recording medium 2 by springs (not shown). The recording medium transporter 28 is rotated by a motor 32 via a gear group 30 in the direction of the arrow in the figure. The registration roller 7 is rotated in the direction of the arrow in the figure by the motor 33 via the gear group 31. Note that FIG. 9 shows an example in which the recording medium transporter 28 and the registration roller 7 are rotated separately by the two motors 32 and 33 (two drive sources), but the present invention is not limited to this. Instead, the configuration may be such that only one drive source rotates both the recording medium transporter 28 and the registration roller 7 by appropriately setting the gear ratio.

If the roller diameter of the registration roller 7 is R1, the angular velocity of the registration roller 7 is θ1, the roller diameter of the recording medium carrier 28 is R2, and the angular velocity of the recording medium carrier 28 is θ2, then R1 × θ1 <R2 × θ2 The roller diameter and the angular velocity are determined so as to satisfy, and the gear ratios of the gear groups 30 and 31 are determined.

The transport speed of the low-end LBP is 25 mm / se
A c ~125mm / sec, the range of the image forming apparatus is wider, the conveying speed v ₂₈ of the recording medium conveying device 28, and the conveying speed v ₇ of the registration roller 7, v ₇ = (0.85
~ 0.95) × v ₂₈ It is preferable to satisfy the relationship,
The roller diameter, the angular velocity, and the gear ratio of the gear groups 30 and 31 are determined so as to satisfy this relationship. When this relationship is satisfied, the recording medium 2 slips on the contact surface between the registration roller 7 and the recording medium 2 due to the difference in the conveying speed, so that tension is applied to the recording medium 2 on the print head 8. This prevents the recording medium 2 from rising from a predetermined position.

If the conveying speed v ₇ is slower than (0.85 × v ₂₈ ), it may cause a conveying trouble, which is not preferable.
Further, if the transport speed v ₇ is higher than (0.95 × v ₂₈ ), sufficient tension cannot be obtained, which is not preferable.

According to the above construction, an electric field corresponding to the applied predetermined voltage is generated between the toner carrier 10 and the counter electrode 11, and the recording medium 2 is conveyed to the toner flying area. Then, based on the voltage applied to the control electrode 13, the flight of the charged toner 12 from the toner carrier 10 to the counter electrode 11 is controlled. Recording medium 2 is counter electrode 1
Since it is conveyed over 1, the flying charged toner 12 reaches the recording medium 2 and an image is formed.

As the recording medium 2 is conveyed to the toner flying region, charged electric charges due to friction or the like are formed on the surface thereof, and the recording medium 2 is lifted by receiving a force by the electric field between the toner carrier 10 and the counter electrode 11.

However, according to the configuration of this embodiment, the recording medium conveying device 28 conveys the recording medium 2 to the downstream side of the toner flying area at a speed faster than that of the registration roller 7. On the contact surface of the recording medium 2, the recording medium 2 slips due to the difference in the conveying speed, and mechanical tension is applied to the recording medium 2. Even if the recording medium 2 is charged while being conveyed to the toner flying area, the tension does not affect the force applied by the electric field. In this way, the recording medium 2 does not receive the flying of the toner in the floating state, and a high quality image is formed (see FIG. 6).

The recording medium 2 on which the image is formed by the charged toner 12 is conveyed as it is and reaches the fixing unit 9, and the fixing unit 9 applies pressure, heat, or both pressure and heat.
As a result, the toner melts and is fixed on the recording medium 2. The recording medium 2 thus fixed is conveyed as it is and is ejected to the ejection tray 15 via the ejection roller 14. At this time, by the discharge sensor 16 provided above one end of the discharge tray 15 on the upstream side in the transport direction,
It is detected whether the recording medium 2 is properly ejected, and the fact is sent to the control unit 6. As a result, the control unit 6 determines that the printing operation has been properly completed, and the printing operation is completed.

Although the example in which the recording medium carrier 28 is separately provided has been described above, the present invention is not limited to this, and the fixing roller in the fixing unit 9 has the original function of the fixing roller and the recording medium carrier. A configuration that also has the functions of 28 may be used. In this case, since it is not necessary to separately provide the recording medium transporter 28, it is possible to save space in the image forming apparatus main body and to reduce costs accordingly.

[0069]

As described above, the image forming apparatus according to the first aspect of the present invention is provided between the toner carrier carrying the charged toner and the toner carrier provided so as to face the toner carrier. Control for selectively controlling the flying of the charged toner to the recording medium in the toner flying area based on the voltage applied between the counter electrode to which a predetermined voltage is applied and the toner carrier and the counter electrode. It has a structure including an electrode and a charge removing unit provided on the upstream side of the toner flying area in the recording medium conveyance direction to remove a charge on the recording medium.

Therefore, since the charge on the recording medium is removed before the recording medium is conveyed to the toner flying area, it is possible to prevent the recording medium from floating from a predetermined position. As a result, the recording medium receives the flying of the charged toner at the original predetermined position on the counter electrode, so that the dots of a prescribed size are formed and the high-quality image is formed without the flying toner diffusing. It has the effect of being able to.

As described above, in the image forming apparatus of the present invention, a predetermined voltage is applied between the toner carrying member carrying the charged toner and the toner carrying member provided so as to face the toner carrying member. A counter electrode to which is applied, and a control electrode which is provided between the toner carrier and the counter electrode, and which suppresses the flying of the charged toner to the recording medium conveyed to the toner flying area in accordance with the applied voltage, And a charge removing unit that is provided on the upstream side of the toner flying region in the recording medium conveyance direction and that removes the charged charges on the recording medium.

Therefore, since the charge on the recording medium is removed before the recording medium is conveyed to the toner flying area, it is possible to prevent the recording medium from floating from the predetermined position. As a result, the recording medium receives the flying of the charged toner at the original predetermined position on the counter electrode, so that the dots of a prescribed size are formed and the high-quality image is formed without the flying toner diffusing. It has the effect of being able to.

As described above, the image forming apparatus according to the invention of claim 3 is the image forming apparatus according to claim 1 or 2.
The static elimination means is a corona charger.

Therefore, similar to the effect according to claim 1 or 2, the charged charge on the recording medium is removed before the recording medium is conveyed to the toner flying area, so that the recording medium floats from the predetermined position. Can be avoided. As a result, the recording medium receives the flying of the charged toner at the original predetermined position on the counter electrode, so that the dots of a prescribed size are formed and the high-quality image is formed without the flying toner diffusing. It has the effect of being able to.

As described above, in the image forming apparatus according to the present invention, a predetermined voltage is applied between the toner carrying member carrying the charged toner and the toner carrying member provided so as to face the toner carrying member. A control electrode for selectively controlling the flight of the charged toner to the recording medium in the toner flight area based on the voltage applied between the counter electrode to which is applied and the toner carrier and the counter electrode. A semi-conductive member provided on the upstream side of the toner flying area in the recording medium conveyance direction and provided so as to come into contact with the conveyed recording medium, and the semi-conductive member for removing the charge on the recording medium. And a means for applying a predetermined alternating voltage to the conductive member.

Therefore, since the charge on the recording medium is removed before the recording medium is conveyed to the toner flying area, it is possible to prevent the recording medium from floating from the predetermined position. As a result, the recording medium receives the flying of the charged toner at the original predetermined position on the counter electrode, so that the dots of a prescribed size are formed and the high-quality image is formed without the flying toner diffusing. It has the effect of being able to.

As described above, the image forming apparatus according to the fifth aspect of the present invention has the configuration according to the fourth aspect, characterized in that the semiconductive member is a conductive elastic member.

Therefore, similar to the effect according to claim 4,
Since the charged charges on the recording medium are removed before the recording medium is conveyed to the toner flying area, it is possible to prevent the recording medium from floating from a predetermined position. As a result, the recording medium receives the flying of the charged toner at the original predetermined position on the counter electrode, so that the dots of a prescribed size are formed and the high-quality image is formed without the flying toner diffusing. It has the effect of being able to.

As described above, the image forming apparatus of the sixth aspect of the present invention is the image forming apparatus of the fourth aspect, wherein the semiconductive member is a brush-like member.

Therefore, similar to the effect according to claim 4,
Since the charged charges on the recording medium are removed before the recording medium is conveyed to the toner flying area, it is possible to prevent the recording medium from floating from a predetermined position. As a result, the recording medium receives the flying of the charged toner at the original predetermined position on the counter electrode, so that the dots of a prescribed size are formed and the high-quality image is formed without the flying toner diffusing. It has the effect of being able to.

As described above, the image forming apparatus according to the present invention has a predetermined voltage between the toner carrying member carrying the charged toner and the toner carrying member provided so as to face the toner carrying member. A counter electrode to which is applied, and a control electrode which is provided between the toner carrier and the counter electrode and selectively controls the flying of the charged toner to the recording medium in the toner flying area based on the applied voltage. A first recording medium conveying means which is provided upstream of the toner flying area in the recording medium conveying direction and conveys the recording medium; and a recording which is provided downstream of the toner flying area in the recording medium conveying direction and which has passed through the toner flying area. And a second recording medium transporting unit that transports the medium further downstream than the first recording medium transporting unit.

Therefore, since mechanical tension is applied to the recording medium, even if the recording medium is charged while being conveyed to the toner flying area, it is possible to avoid being affected by the force applied by the electric field. As described above, the recording medium does not receive the flying of the toner in the floating state, and it is possible to form a high quality image.

As described above, the image forming apparatus of the invention of claim 8 is characterized in that, in the structure of claim 7, the second recording medium conveying means is a fixing roller.

Therefore, in addition to the effect of claim 7,
Since the fixing roller also serves as the second recording medium conveying unit, there is an effect that space saving and cost reduction can be achieved.

[Brief description of drawings]

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

FIG. 2 is an enlarged view of the vicinity of the print head of the image forming apparatus.

FIG. 3 is an explanatory diagram showing a configuration example of a static eliminator of the image forming apparatus.

FIG. 4 is an explanatory diagram showing another configuration example of the above static eliminator.

FIG. 5 is an explanatory diagram showing still another configuration example of the static eliminator.

FIG. 6 is an explanatory diagram showing dots formed when static elimination processing is performed.

FIG. 7 is an explanatory diagram showing dots that are formed when the charge removal processing is not performed.

FIG. 8 is an explanatory diagram showing a configuration example of another image forming apparatus of the present invention.

FIG. 9 is an explanatory diagram showing a main configuration of the image forming apparatus in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Paper feed tray 2 Recording medium 3 Supply roller 4 Static eliminator (static elimination means) 5 Supply sensor 6 Control unit 7 Registration roller (first recording medium conveying means) 9 Fixing section (second recording medium conveying means) 10 Toner carrier 11 Counter electrode 12 Charged toner 13 Control electrode 14 Discharge roller 15 Discharge tray

Claims (8)

[Claims] 1. A toner carrier for carrying a charged toner, a counter electrode provided so as to face the toner carrier, and a predetermined voltage is applied between the toner carrier and the toner carrier. And a counter electrode, which is provided between the control electrode and the counter electrode, and selectively controls the flying of the charged toner to the recording medium in the toner flying area based on the applied voltage, and the upstream side of the toner flying area in the recording medium conveying direction. An image forming apparatus, which is provided on a side of the recording medium and includes a charge removing unit that removes a charge on the recording medium. 2. A toner carrier for carrying a charged toner, a counter electrode provided so as to face the toner carrier, and a predetermined voltage is applied between the toner carrier and the toner carrier. And a counter electrode, which is provided between the control electrode and the counter electrode, and which suppresses the flying of the charged toner to the recording medium conveyed to the toner flying area according to the applied voltage, and the upstream side of the toner flying area in the recording medium carrying direction. An image forming apparatus, which is provided in the image forming apparatus and is provided with a charge removing unit that removes a charged charge on the recording medium. 3. The image forming apparatus according to claim 1, wherein the charge eliminating means is a corona charger. 4. A toner carrier for carrying a charged toner, a counter electrode which is provided so as to face the toner carrier and to which a predetermined voltage is applied between the toner carrier and the toner carrier. And a counter electrode, which is provided between the control electrode and the counter electrode, and selectively controls the flying of the charged toner to the recording medium in the toner flying area based on the applied voltage, and the upstream side of the toner flying area in the recording medium conveying direction. A semi-conductive member that is provided on the side of the recording medium and that is in contact with the conveyed recording medium, and a predetermined alternating voltage for the semi-conductive member so as to remove the charged charges on the recording medium. And an image forming apparatus including means for applying a voltage. 5. The image forming apparatus according to claim 4, wherein the semiconductive member is a conductive elastic member. 6. The image forming apparatus according to claim 4, wherein the semiconductive member is a brush-shaped member. 7. A toner carrier carrying a charged toner, a counter electrode provided so as to face the toner carrier, and a predetermined voltage is applied between the toner carrier and the toner carrier, and the toner carrier described above. And a counter electrode, which is provided between the control electrode and the counter electrode, and selectively controls the flying of the charged toner to the recording medium in the toner flying area based on the applied voltage, and the upstream side of the toner flying area in the recording medium conveying direction. And a first recording medium conveying means for conveying the recording medium, and a recording medium provided downstream of the toner flying area in the recording medium conveying direction for passing the toner flying area from the first recording medium conveying means. An image forming apparatus including a second recording medium conveying unit that conveys the recording medium further downstream at a higher speed. 8. The image forming apparatus according to claim 7, wherein the second recording medium conveying means is a fixing roller.