Patent Description:
In the related art, a fixing device is provided to fix a toner image on a sheet. The fixing device includes a nozzle unit and an opposite electrode. The nozzle unit sprays a fixing solution onto a sheet on which the toner image is formed. The opposite electrode is located at an interval from the nozzle unit. A voltage is applied to the opposite electrode (refer to Patent Literature <NUM>). <CIT> discloses a fixing device. Patent Literature <NUM>: <CIT>.

However, according to the fixing device disclosed in Patent Literature <NUM>, mists of the fixing solution sprayed from nozzles are electrically charged. For this reason, the mists of the fixing solution are provided to the sheet, so that the sheet is electrically charged. When the fixing solution is additionally sprayed to the electrically charged sheet, an electrostatic repulsive force is generated between the mists of the fixing solution and the sheet, so that the mists of the fixing solution are difficult to be attracted to the sheet.

Therefore, it is difficult to stably provide the fixing solution to the sheet.

An outline of an image forming apparatus <NUM> is described with reference to <FIG>.

An image forming apparatus <NUM> includes a main body housing <NUM>, a sheet feeding unit <NUM>, a photosensitive drum <NUM>, a charging device <NUM>, an exposure device <NUM>, a developing device <NUM>, a transfer device <NUM>, and a fixing device <NUM>.

The main body housing <NUM> accommodates the sheet feeding unit <NUM>, the photosensitive drum <NUM>, the charging device <NUM>, the exposure device <NUM>, the developing device <NUM>, the transfer device <NUM>, and the fixing device <NUM>.

The sheet feeding unit <NUM> feeds a sheet S to the photosensitive drum <NUM>. The sheet feeding unit <NUM> includes a sheet cassette <NUM>, a pickup roller <NUM>, and a conveying roller <NUM>. The sheet cassette <NUM> accommodates sheets S. The sheet S is, for example, a printing sheet. The pickup roller <NUM> conveys the sheet S in the sheet cassette <NUM> toward the conveying roller <NUM>. The conveying roller <NUM> conveys the sheet S from the pickup roller <NUM> toward the photosensitive drum <NUM>.

The photosensitive drum <NUM> can rotate about an axis A. The axis A extends in a first direction. The photosensitive drum <NUM> has a cylindrical shape. The photosensitive drum <NUM> extends along axis A.

The charging device <NUM> electrically charges a surface of the photosensitive drum <NUM>. The charging device <NUM> is, specifically, a charging roller. Note that, the charging device <NUM> may also be a scorotron-type charger. In a case where the charging device <NUM> is a charging roller, the charging device <NUM> is in contact with the surface of the photosensitive drum <NUM>. In a case where the charging device <NUM> is a scorotron-type charging device, the charging device <NUM> is located at an interval from the surface of the photosensitive drum <NUM>.

The exposure device <NUM> exposes the surface of the photosensitive drum <NUM>. Specifically, the exposure device <NUM> exposes the surface of the photosensitive drum <NUM> electrically charged by the charging device <NUM>. Thereby, an electrostatic latent image is formed on the surface of the photosensitive drum <NUM>. The exposure device <NUM> is, specifically, a laser scan unit. Note that, the exposure device <NUM> may also be an LED array.

The developing device <NUM> supplies toner to the surface of the photosensitive drum <NUM>. Thereby, the electrostatic latent image is developed, so that a toner image is formed on the surface of the photosensitive drum <NUM>. The developing device <NUM> includes a toner accommodation unit <NUM> and a developing roller <NUM>.

The toner accommodation unit <NUM> accommodates toner. Toner contains toner particles, and as required, an external additive. The toner particles contain a binding resin, and as required, a colorant, a pigment dispersant, a mold release agent, a magnetic material and a charge control agent. The binding resin is a base of the toner particles. The binding resin binds the components contained in the toner particles. The colorant imparts a desired color to the toner particles. The colorant is dispersed in the binding resin. The pigment dispersant improves dispersibility of the colorant. The charge control agent gives chargeability to the toner particles. The chargeability may be any of positive chargeability and negative chargeability. The external additive regulates chargeability, flowability and storage stability of the toner particles.

The developing roller <NUM> supplies toner in the toner accommodation unit <NUM> to the surface of the photosensitive drum <NUM>. The developing roller <NUM> is in contact with the photosensitive drum <NUM>. Note that, the developing roller <NUM> may not be in contact with the photosensitive drum <NUM>.

The developing device <NUM> may be constituted as one process unit, together with the photosensitive drum <NUM> and the charging device <NUM>. The process unit can be mounted to the main body housing <NUM>.

In addition, the developing device <NUM> may be a developing cartridge that can be mounted to a drum unit having the photosensitive drum <NUM> and the charging device <NUM>. The drum unit can be mounted to the main body housing <NUM>.

The developing device <NUM> may also have a developing unit having the developing roller <NUM>, and a toner cartridge that can be mounted to the developing unit. In this case, the toner cartridge has the toner accommodation unit <NUM>. In addition, the developing unit may be provided to the drum unit. The developing unit can be mounted to the drum unit.

The transfer device <NUM> transfers the toner image from the photosensitive drum <NUM> to the sheet S. Thereby, the toner image is formed on the sheet S. The transfer device <NUM> is in contact with the photosensitive drum <NUM>. Note that, the transfer device <NUM> may not be in contact with the photosensitive drum <NUM>. The transfer device <NUM> is, specifically, a transfer roller. Note that, the transfer device <NUM> may also be a transfer belt.

The fixing device <NUM> provides a fixing solution to the toner image to fix the toner image on the sheet S. Specifically, the fixing device <NUM> sprays the fixing solution toward the toner image on the sheet S by electrostatic spraying, thereby providing the fixing solution to the toner image. Then, the binding resin of the toner is softened by the fixing solution. Thereafter, the softened binding resin is cured, so that the toner is fixed on the sheet S. Thereby, the toner image is fixed on the sheet S. The sheet S on which the toner image is fixed is discharged outside the main body housing <NUM>.

Subsequently, details of the fixing device <NUM> are described with reference to <FIG>.

As shown in <FIG>, the fixing device <NUM> includes a nozzle unit 9A and an opposite electrode 9B.

The nozzle unit 9A sprays the fixing solution to a sheet S on which a toner image is formed. As shown in <FIG>, the nozzle unit 9A includes a housing <NUM>, and a plurality of nozzles <NUM>.

The housing <NUM> can accommodate the fixing solution. The housing <NUM> extends in the first direction. The first direction is a direction in which the axis A of the photosensitive drum <NUM> extends. The first direction is also a width direction of the sheet S. The housing <NUM> has an outer surface S1 and an outer surface S2 in a second direction. The second direction is a direction facing from the opposite electrode 9B (refer to <FIG>) toward the nozzle unit 9A. The second direction intersects with the first direction. Specifically, the second direction is orthogonal to the first direction. The outer surface S2 is located distant from the outer surface S1 in the second direction. The outer surface S2 is located closer to the opposite electrode 9B than the outer surface S1 in the second direction. The housing <NUM> has a nozzle electrode 21A.

The nozzle electrode 21A is electrically connected to a power supply P1 (refer to <FIG>) of the image forming apparatus <NUM>. Thereby, the nozzle electrode 21A is applied with a voltage. The fixing solution in the housing <NUM> is electrically charged by the nozzle electrode 21A.

The plurality of nozzle <NUM> is located on the outer surface S2 of the housing <NUM>. The plurality of nozzles <NUM> is located between the nozzle electrode 21A the opposite electrode 9B (refer to <FIG>) in the second direction. Each of the plurality of nozzles <NUM> extends from the outer surface S2 of the housing <NUM> toward the opposite electrode 9B. Each of the plurality of nozzles <NUM> extends in the second direction. The plurality of nozzles <NUM> discharge the fixing solution in the housing <NUM>. Specifically, in a state where a voltage is applied to the nozzle electrode 21A and the opposite electrode 9B, the fixing solution passing through the tip ends of the nozzles <NUM> is misted by an electrostatic force between the nozzle electrode 21A and the opposite electrode 9B. The misted fixing solution is provided to the sheet S (refer to <FIG>) passing between the nozzle unit 9A and the opposite electrode 9B.

As shown in <FIG>, the opposite electrode 9B is located at an interval from the nozzle unit 9A in the second direction. The opposite electrode 9B is made of metal. As shown in <FIG>, the opposite electrode 9B has a first flat plate <NUM>, a plurality of first projections <NUM>, a second flat plate <NUM>, a plurality of second projections <NUM>, a plurality of connection plates <NUM> and a connection terminal <NUM>.

The first flat plate <NUM> extends in the first direction and in the second direction. The first flat plate <NUM> has an edge E1 and an edge E2 in the second direction. The edge E2 is located distant from the edge E1 in the second direction. The edge E2 is located closer to the nozzle unit 9A (refer to <FIG>) than the edge E1 in the second direction. Also, the first flat plate <NUM> has an edge E3 and an edge E4 in the first direction. The edge E4 is located distant from the edge E3 in the first direction.

As shown in <FIG>, each of the plurality of first projections <NUM> extends from the edge E2 of the first flat plate <NUM> in the second direction. Thereby, in a state where a voltage is applied to the opposite electrode 9B, an electrostatic force is concentrated on a tip end <NUM> of each of the plurality of first projections <NUM>. For this reason, it is possible to form a strong electric field at the tip end <NUM> of each of the plurality of first projections <NUM> without increasing the voltage that is applied to the opposite electrode 9B. Specifically, each of the plurality of first projections <NUM> is tapered from the first flat plate <NUM> toward the nozzle unit 9A in the second direction. Thereby, the electrostatic force is more concentrated on the tip end <NUM> of each of the plurality of first projections <NUM>. Specifically, each of the plurality of first projections <NUM> is an isosceles triangle flat plate. Note that, each of the plurality of first projections <NUM> may also have a conical shape. The tip end <NUM> of each of the plurality of first projections <NUM> has an arc shape.

A length of each of the plurality of first projections <NUM> in the second direction is, for example, <NUM> or greater, preferably <NUM> or greater. The length of each of the plurality of first projections <NUM> in the second direction is, for example, <NUM> or less.

As shown in <FIG>, the tip end <NUM> of each of the plurality of first projections <NUM> is located between the nozzle unit 9A (refer to <FIG>) and the connection terminal <NUM> in the second direction. For this reason, in the state where the voltage is applied to the opposite electrode 9B, the fixing solution sprayed from each of the plurality of nozzles <NUM> (refer to <FIG>) is more attracted to the tip end <NUM> of each of the plurality of first projections <NUM> than the connection terminal <NUM>.

As shown in <FIG>, the plurality of first projections <NUM> are aligned at intervals in the first direction. Thereby, in the state where the voltage is applied to the opposite electrode 9B, the strong electric field is formed in the first direction. Note that, an interval in the first direction between the two adjacent first projections <NUM> is preferably smaller than an interval in the first direction between the two adjacent nozzles <NUM>. The interval in the first direction between the two adjacent first projections <NUM> is, for example, <NUM> or less, preferably <NUM> or less. The interval in the first direction between the two adjacent first projections <NUM> is, for example, <NUM> or greater. The number of the plurality of first projections <NUM> is larger than the number of the plurality of nozzles <NUM>. Thereby, the fixing solution sprayed from the plurality of nozzles <NUM> can be securely attracted toward the opposite electrode 9B. The plurality of first projections <NUM> includes opposite projections 32A that face the nozzles <NUM> in the second direction, and non-opposite projections 32B that do not face the nozzles <NUM> in the second direction. As shown in <FIG>, the tip end <NUM> of the opposite projection 32A is within a projection plane P when projecting the nozzle <NUM> in the second direction. Preferably, the tip end <NUM> of the opposite projection 32A is matched with a tip end <NUM> of the nozzle <NUM> when projecting the nozzle <NUM> in the second direction. On the other hand, the tip end <NUM> of the non-opposite projection 32B is not within the projection plane P when projecting the nozzle <NUM> in the second direction. The tip end <NUM> of the non-opposite projection 32B is within a range R in which the fixing solution is sprayed from the nozzle <NUM>.

As shown in <FIG>, the second flat plate <NUM> is located distant from the first flat plate <NUM> in a third direction. The third direction is a direction in which the sheet S (refer to <FIG>) is conveyed from the photosensitive drum <NUM> (refer to <FIG>) of the image forming apparatus <NUM> toward the fixing device <NUM> (refer to <FIG>). The third direction intersects with both the first direction and the second direction.

The second flat plate <NUM> extends in the first direction and in the second direction. The second flat plate <NUM> has an edge E11 and an edge E12 in the second direction. The edge E12 is located distant from the edge E11 in the second direction. The edge E12 is located closer to the nozzle unit 9A (refer to <FIG>) than the edge E11 in the second direction.

Each of the plurality of second projections <NUM> extends from the edge E12 of the second flat plate <NUM> toward the nozzle unit 9A in the second direction. Each of the plurality of second projections <NUM> has the same shape as each of the plurality of first projections <NUM>. Thereby, each of the plurality of second projections <NUM> has the same function as each of the plurality of first projections <NUM>. The plurality of second projections <NUM> are aligned at intervals in the first direction.

Each of the plurality of connection plates <NUM> extends in the first direction and in the third direction. One end portion of each of the plurality of connection plates <NUM> in the third direction is connected to the edge E1 of the first flat plate <NUM>. In addition, the other end portion of each of the plurality of connection plates <NUM> in the third direction is connected to the edge E11 of the second flat plate <NUM>. Each of the plurality of connection plates <NUM> is provided to electrically connect the first flat plate <NUM> and the second flat plate <NUM> each other. Thereby, in the state where the voltage is applied to the opposite electrode 9B, a voltage of the first flat plate and a voltage of the second flat plate are the same. The plurality connection plates <NUM> are aligned at intervals in the first direction.

The connection terminal <NUM> is located at one end portion of the opposite electrode 9B in the first direction. Specifically, the connection terminal <NUM> extends from the edge E3 of the first flat plate <NUM>. The connection terminal <NUM> is electrically connected to a power supply P2 (refer to <FIG>) of the image forming apparatus <NUM>.

Specifically, as shown in <FIG>, the fixing device <NUM> includes a frame 9C and an electrode 9D.

The frame 9C has an accommodation unit <NUM>. The accommodation unit <NUM> can accommodate the fixing solution sprayed from the nozzle unit 9A. The accommodation unit <NUM> has a bottom wall <NUM> and a sidewall <NUM>. The bottom wall <NUM> is located on an opposite side to the nozzle unit 9A with respect to the opposite electrode 9B in the second direction. The sidewall <NUM> extends from the bottom wall <NUM> in the second direction. The opposite electrode 9B is attached to the bottom wall <NUM>.

The electrode 9D is attached to the sidewall <NUM>. The electrode 9D is electrically connected to the power supply P2 (refer to <FIG>) of the image forming apparatus <NUM>. The connection terminal <NUM> is in contact with the electrode 9D. Thereby, the connection terminal <NUM> is electrically connected to the power supply P2 of the image forming apparatus <NUM> via the electrode 9D. Thereby, the voltage is applied to the opposite electrode 9B by the electrode 9D.

According to the fixing device <NUM>, as shown in <FIG>, the opposite electrode 9B has the plurality of first projections <NUM>. The plurality of first projections <NUM> extends from the opposite electrode 9B toward the nozzle unit 9A (refer to <FIG>).

In the state where the voltage is applied to the opposite electrode 9B, the electrostatic force is concentrated on the tip end <NUM> of each of the plurality of first projections <NUM>.

For this reason, it is possible to form the strong electric field at the tip end <NUM> of each of the plurality of first projections <NUM> without increasing the voltage that is applied to the opposite electrode 9B.

The plurality of first projections <NUM> are aligned in the first direction.

For this reason, it is possible to stably attract the fixing solution sprayed from each of the plurality of nozzles <NUM> toward the opposite electrode 9B by the strong electric field formed in the first direction.

As a result, even in a case where the sheet S is electrically charged, it is possible to stably provide the fixing solution sprayed from each of the plurality of nozzles <NUM> to the sheet S.

In addition, according to the fixing device <NUM>, as shown in <FIG>, each of the plurality of first projections <NUM> is tapered from the first flat plate <NUM> toward the nozzle unit 9A in the second direction.

Thereby, the electrostatic force can be further concentrated on the tip end <NUM> of each of the plurality of first projections <NUM>.

Further, according to the fixing device <NUM>, as shown in <FIG>, each of the plurality of connection plates <NUM> is provided to electrically connect the first flat plate <NUM> and the second flat plate <NUM> each other.

Thereby, in the state where the voltage is applied to the opposite electrode 9B, the voltage of the first flat plate <NUM> and the voltage of the second flat plate <NUM> are the same.

As a result, it is possible to form the electric field of the uniform intensity by the plurality of first projections <NUM> and the plurality of second projections <NUM>.

In addition, according to the fixing device <NUM>, as shown in <FIG>, the tip end <NUM> of each of the plurality of first projections <NUM> is located between the nozzle unit 9A (refer to <FIG>) and the connection terminal <NUM> in the second direction.

For this reason, in the state where the voltage is applied to the opposite electrode 9B, the fixing solution sprayed from each of the plurality of nozzles <NUM> is more attracted to the tip end <NUM> of each of the plurality of first projections <NUM> than the connection terminal <NUM>.

In addition, according to the fixing device <NUM>, as shown in <FIG>, the number of the plurality of first projections <NUM> is larger than the number of the plurality of nozzles <NUM>.

Thereby, the fixing solution sprayed from the plurality of nozzles <NUM> can be securely attracted toward the opposite electrode 9B.

Modified examples are described with reference to <FIG>. Note that, in the modified examples, the same members as the above embodiment are denoted with the same reference signs, and the descriptions thereof are omitted. <FIG> describe modified examples that do not fall within the scope of the claims.

Specifically, the electrode 9D extends in the third direction. The third direction is a direction in which the sheet S passes between the nozzle unit 9A and the opposite electrode 9B. The third direction intersects with both the first direction and the second direction. The third direction is preferably orthogonal to both the first direction and the second direction. The electrode 9D has a first terminal T1 and a second terminal T2.

The first terminal T1 is located inside the accommodation unit <NUM>. The first terminal T1 is electrically connected to the opposite electrode 9B inside the accommodation unit <NUM>. The first terminal T1 is in contact with a central portion of the opposite electrode 9B in the first direction. The first terminal T1 is in contact with the connection plate <NUM> of the opposite electrode 9B. In a state where the first terminal T1 is in contact with the connection plate <NUM> of the opposite electrode 9B, the first terminal T1 is located more distant from the nozzle unit 9A than the tip end <NUM> of each of the plurality of first projections <NUM> in the second direction. In other words, in the state where the first terminal T1 is in contact with the connection plate <NUM> of the opposite electrode 9B, the tip end <NUM> of each of the plurality of first projections <NUM> is located between the nozzle unit 9A and the first terminal T1 in the second direction. Note that, in this modified example, as shown in <FIG>, the opposite electrode 9B is not provided with the connection terminal <NUM>.

The second terminal T2 is located outside the accommodation unit <NUM>. The second terminal T2 is located distant from the first terminal T1. The second terminal T2 is electrically connected to the power supply P2 of the image forming apparatus <NUM> outside the accommodation unit <NUM>.

In this modified example, as shown in <FIG>, since the electrode 9D is spaced from the sidewall <NUM>, it is possible to suppress the sidewall <NUM> from being electrically charged due to the voltage applied to the opposite electrode 9B.

For this reason, it is possible to suppress the mists of the fixing solution sprayed from the nozzle unit 9A from being attracted to the sidewall <NUM>.

Claim 1:
A fixing device (<NUM>) provided to fix a toner image on a sheet (S), and comprising a nozzle unit (9A) that sprays a fixing solution to the sheet on which the toner image is formed and an opposite electrode (9B) located at an interval from the nozzle unit, a voltage being applied to the opposite electrode,
wherein the opposite electrode comprises:
a first flat plate (<NUM>) extending in a first direction; and
a plurality of first projections (<NUM>) aligned in the first direction and extending from the first flat plate in a second direction that is a direction facing from the opposite electrode toward the nozzle unit;
characterised in that, the opposite electrode further comprises a connection terminal (<NUM>) electrically connected to a power supply of an image forming apparatus and located at one end portion of the opposite electrode in the first direction, wherein a tip end (<NUM>) of each of the plurality of first projections is located between the nozzle unit and the connection terminal in the second direction.