Patent Description:
Conventionally, an image forming apparatus is provided with a fixing section which is configured to fix a toner image to a print medium. The fixing section sprays a fixing solution onto the print medium in which the toner image is formed so as to fix the toner image to the print medium (see Patent Literature <NUM> below). <CIT> discloses a fixing temperature control device having a control section having a warm-up control mode and a normal control mode. In the warm-up control mode, energization to a heater is started in response to the start of copying, while being stopped at the time point where a temperature detected by a heat roller temperature detecting sensor reaches a first off temperature. In the normal control mode, on-off control of the energization to the heater is carried out utilizing a predetermined control temperature as a target subsequently to the termination of the warm-up control mode. The predetermined control temperature is corrected by adding a prescribed correction amount to a reference control temperature. It is preferable that the required correction amount includes i) an initial correction amount added in the early stages of processing in the normal control mode, ii) a correction amount at the time of passing paper sheets added when paper sheets pass between a heat roller and a pressure roller in a fixing device, and iii) an environmental correction amount added depending on an environmental temperature. <CIT> discloses an image forming apparatus including a toner image forming section, an intermediate transferring section, a transferring section, a fixing solution applying section, a transporting section, a fixing section, and a recording medium feeding section. In the image forming apparatus, the fixing solution applying section includes a droplet supplying section, a recording medium detecting section, and a control unit, wherein the recording medium is heated before or at the same time when the fixing solution is applied to the recording medium by the fixing solution applying section, and a size of droplets of the fixing solution supplied to the recording medium is controlled based on the type of the recording medium.

[Patent Literature]
Patent Literature <NUM>: Japanese Patent Application Laid-Open No. <CIT>.

In the image forming apparatus as described in Patent Literature <NUM>, the fixing property of the toner image with respect to the print medium is lowered, in some cases, by a temperature of the environment in which the image forming apparatus is installed.

In view of this situation, an object of the present disclosure is to provide an image forming apparatus capable of suppressing any lowering in the fixing property of the toner image with respect to the print medium due to the temperature of environments in which the image forming apparatus is installed.

Further developments of the invention are specified by the dependent claims.

With the image forming apparatus of the invention, by slowing down the conveying velocity of the print medium by the image carrier and the transferring section, it is possible to lengthen a period of time during which the print medium having the fixing solution applied thereto passes (passes through) the heater.

With this, it is possible to secure a long period of time for fixing the toner image to the print medium in a case that the temperature is lower than the threshold value.

As a result, it is possible to suppress any lowering in the fixing property of the toner image with respect to the print medium due to the temperature of the environment in which the image forming apparatus is installed.

According to the image forming apparatus of the present disclosure, it is possible to suppress the lowering in the fixing property of the toner image with respect to the print medium due to the temperature of the environment in which the image forming apparatus is installed.

The overall schematic of an image forming apparatus <NUM> will be explained, with reference to <FIG>.

The image forming apparatus <NUM> includes a body casing (main body casing) <NUM>, a sheet feeding section <NUM>, a toner image forming section <NUM>, and a fixing section <NUM>.

The body casing <NUM> constructs the exterior of the image forming apparatus <NUM>. The body casing <NUM> accommodates the sheet feeding section <NUM>, the toner image forming section <NUM>, and the fixing section <NUM>.

The sheet feeding section <NUM> is configured to supply or feed a print medium S to the toner image forming section <NUM>. Specifically, the sheet feeding section <NUM> is configured to convey the print medium S toward an image carrier <NUM> of the toner image forming section <NUM>. The toner image forming section <NUM> will be explained later on. The sheet feeding section <NUM> includes a paper feed tray <NUM>, a pick-up roller <NUM>, and a paper feed roller <NUM>. The paper feed tray <NUM> is configured to accommodate the print medium S. The print medium S is, for example, printing paper (printing paper sheet, printing sheet). The pick-up roller <NUM> is configured to convey the print medium S in the inside of the paper feed tray <NUM> toward the paper feed roller <NUM>. The paper feed roller <NUM> is configured to convey the print medium S from the pick-up roller <NUM> toward the image carrier <NUM>.

The toner image forming section <NUM> is configured to use a toner to thereby form a toner image in the print medium S. The toner image forming section <NUM> includes an image carrier <NUM>, a charger <NUM>, an exposure device <NUM>, a developing device <NUM>, and a transferring section <NUM>.

The image carrier <NUM> is configured to carry the toner image. Specifically, the image carrier <NUM> is a photosensitive drum.

The charger <NUM> is configured to charge a surface of the image carrier <NUM>. The charger <NUM> is specifically a charging roller. Note that the charger <NUM> may be a scorotron type charging device. In a case that the charger <NUM> is the charging roller, the charger <NUM> makes contact with the surface of the image carrier <NUM>. In a case that the charger <NUM> is the scorotron type charging device, the charger <NUM> is positioned to be separated away from the surface of the image carrier <NUM> at a spacing distance.

The exposure device <NUM> is configured to expose the surface of the image carrier <NUM>. More specifically, the exposure device <NUM> is configured to expose the surface of the image carrier <NUM> charged by the charger <NUM>. As a result, an electrostatic latent image is formed on the surface of the image carrier <NUM>. The exposure device <NUM> is specifically a laser scan unit. Note that the exposure device <NUM> may be an LED array.

The developing device <NUM> is configured to supply or feed the toner onto the surface of the image carrier <NUM>. As a result, the electrostatic latent image is developed, and a toner image is formed on the surface of the image carrier <NUM>. The developing device <NUM> includes a toner accommodating section <NUM> and a developing roller <NUM>.

The toner accommodating section <NUM> accommodates the toner. The toner contains toner particles, and as necessary or optionally, an external additive. The toner particles contain: a binder resin, and as necessary, a colorant, a pigment dispersant, a mold releasing agent, a magnetic body, and an electrostatic charge controlling agent. The binder resin is the base of the toner particles. The binder resin binds components contained in the toner particles. The binder resin is softened by the application of the fixing solution thereto, and then is cured so that the binder is firmly fixed to the print medium S. The colorant imparts a desired color to the toner particles. The colorant is dispersed in the binder resin. The pigment dispersant improves the dispersibility of the colorant. The electrostatic charge controlling agent imparts the electrostatic property to the toner particles. The electrostatic property may be either of the positive electrostatic charge or of the negative electrostatic charge. The external additive adjusts the electrostatic property, the fluidity, the storage stability of the toner particles.

The developing roller <NUM> is configured to supply the toner inside the toner accommodating section <NUM> to the surface of the image carrier <NUM>. The developing roller <NUM> makes contact with the image carrier <NUM>. Note that it is allowable that the developing roller <NUM> makes no contact with the image carrier <NUM>.

The developing device <NUM> may be configured as a single process unit, together with the image carrier <NUM> and the charger <NUM>. The process unit may be installable with respect to the body casing <NUM>.

Further, the developing device <NUM> may be a developing cartridge which is installable with respect to a drum unit having the image carrier <NUM> and the charger <NUM>. The drum unit may be installable with respect to the body casing <NUM>.

Further, the developing device <NUM> may include a developer which includes the developing roller <NUM>, and a toner cartridge which is installable with respect to the developer. In such a case, the toner cartridge is provided with the toner accommodating section <NUM>. Further, the developer may be provided on the drum unit. The developer may be installable with respect to the drum unit.

The transferring section <NUM> is configured to transfer the toner image formed on the surface of the image carrier <NUM> to the print medium S. Further, the transferring section <NUM> is configured to convey, together with the image carrier <NUM>, the print medium S. Specifically, the transferring section <NUM> is a transfer roller. The transferring section <NUM> makes contact with the image carrier <NUM>. Note that it is allowable that the transferring section <NUM> makes no contact with image carrier <NUM>. Further note that the transferring section <NUM> may be, for example, a transfer belt.

The fixing section <NUM> applies the fixing solution to the print medium S, conveyed by the image carrier <NUM> and the transferring section <NUM>, so as to fix the toner image to the print medium S. In other words, the fixing solution is applied to the print medium S, in which the toner image is formed by the toner image forming section <NUM>, so as to fix the toner image to the print medium S. Specifically, the fixing section <NUM> is a fixing device which sprays the fixing solution by electrostatic spraying. Note that the fixing section <NUM> may be a fixing device having a fixing roller configured to apply the fixing solution, or a fixing device having a piezoelectric device configured to apply the fixing solution. The print medium S which has passed the fixing section <NUM> is discharged, by the conveying section <NUM>, to the upper surface of the body casing <NUM>. The conveying section <NUM> will be explained later.

As depicted in <FIG> and <FIG>, the image forming apparatus <NUM> further includes a conveying section <NUM>, a temperature sensor <NUM>, a heater <NUM>, a driving source <NUM> (see <FIG>), and a controller <NUM> (see <FIG>).

As depicted in <FIG>, the conveying section <NUM> conveys the print medium S which has passed the fixing section <NUM>. Specifically, the conveying section <NUM> includes a plurality of conveying rollers 26A, 26B, and a plurality of discharge rollers 27A, 27B.

The conveying roller 26A conveys, together with the conveying roller 26B, the print medium S which has passed the fixing section <NUM> toward the discharge roller 27A. The conveying roller 26A makes contact with the conveying roller 26B. The print medium S passes between the conveying roller 26A and the conveying roller 26B.

The discharge roller 27A discharges, together with the discharge roller 27B, the print medium S that has passed between the conveying roller 26A and the conveying roller 26B to the outside of the body casing <NUM>. The discharge roller 27A makes contact with the discharge roller 27B. The print medium S passes between the discharge roller 27A and the discharge roller 27B.

The temperature sensor <NUM> measures a temperature in (inside, in the inside of) the body casing <NUM>. Specifically, the temperature sensor <NUM> measures a temperature in the vicinity of the fixing section <NUM>. More specifically, the temperature sensor <NUM> measures a temperature in a space between the transferring section <NUM> and the fixing section <NUM>.

The heater <NUM> heats the print medium S which has passed the fixing section <NUM>. The heater <NUM> is positioned between the fixing section <NUM> and the conveying section <NUM>. The heater <NUM> does not have any contact with the print medium S in a case that the heater heats the print medium S. Specifically, the heater <NUM> is a halogen lamp. Note that the heater <NUM> may be a roller which makes contact with the print medium S.

As depicted in <FIG>, the driving source <NUM> drives the conveying section <NUM>, the image carrier <NUM> and the transferring section <NUM>. Specifically, the driving source <NUM> is a motor. In a case that the driving source <NUM> is a motor, the driving source <NUM> is connected to the plurality of conveying rollers 26A, 26B and the plurality of the discharge rollers 27A, 27B of the conveying section <NUM>, the image carrier <NUM>, and the transferring section <NUM> via a power transmission mechanism (not depicted in the drawings). The power transmission mechanism (not depicted in the drawings) may include a gear train and/or a clutch. Thus, the motive power from the driving source <NUM> is transmitted to the plurality of the conveying roller 26A and 26B and the plurality of the discharge rollers 27A and 27B of the conveying section <NUM>, the image carrier <NUM>, and the transferring section <NUM> via the gear train (not depicted in the drawings).

As depicted in <FIG>, the controller <NUM> controls the temperature sensor <NUM>, the fixing section <NUM>, the heater <NUM>, the driving source <NUM>, and the power transmitting mechanism (which is not depicted in the drawings). Further, the controller <NUM> controls the driving source <NUM> or the power transmitting mechanism (not depicted in the drawings) to thereby control the conveying section <NUM>, the image carrier <NUM>, and the transferring section <NUM>. The controller <NUM> is electrically connected to the temperature sensor <NUM>, the fixing section <NUM>, the heater <NUM>, the driving source <NUM>, and the power transmitting mechanism (which is not depicted in the drawings), via a signal trace (which is not depicted in the drawings). The controller <NUM> may be, for example, a control circuit board provided with a memory and an ASIC. Alternatively, the controller <NUM> may be a control circuit board provided with a memory and a CPU.

Next, the fixing control of the image forming apparatus <NUM> will be explained, with reference to <FIG>.

As depicted in <FIG>, the controller <NUM> controls a conveying velocity (S4) of the print medium S by the conveying section <NUM>, a conveying velocity (S5) of the print medium S by the image carrier <NUM> and the transferring section <NUM>, and a heating temperature (S6) of the heater <NUM>, based on a printing condition (S1) and a temperature (S2) in the body casing <NUM> so as to optimize a fixing condition.

The above-described control performed by the controller <NUM> will be explained in detail as below.

In a case that a print job is inputted to the image forming apparatus, the controller <NUM> obtains a printing condition of the print job (step S1). The printing condition is exemplified, for example, by: the kind of the print medium S, the image quality of the toner image, the number of sheets (paper sheets) on which the printing is to be performed, etc..

Note that the controller <NUM> may control an application amount of the fixing solution to be applied by the fixing section <NUM> and a heating temperature of the heater <NUM>, based on the printing condition. Specifically, the controller <NUM> has data of coefficients corresponding to the respective kinds of the printing condition which are the kind of the print medium S, the image quality of the toner image, the number of sheets to which the printing is to be performed, etc. More specifically, a memory of the controller <NUM> has the data of coefficients corresponding to the respective kinds of the printing condition which are the kind of the print medium S, the image quality of the toner image, the number of sheets to which the printing is to be performed, etc. The controller <NUM> controls the application amount of the fixing solution, in accordance with the printing condition, by multiplying a reference value of the application amount of the fixing solution by a coefficient based on the printing condition. Further, the controller <NUM> controls the heating temperature of the heater <NUM>, in accordance with the printing condition, by multiplying a reference value of the heating temperature of the heater <NUM> by a coefficient based on the printing condition. Specifically, the ASIC or the CPU of the controller <NUM> controls the application amount of the fixing solution in accordance with the printing condition by multiplying the reference value of the application amount of the fixing solution stored in the memory of the controller <NUM> by the coefficient based on the printing condition stored in the memory of the controller <NUM>. Furthermore, the ASIC or the CPU of the controller <NUM> controls the heating temperature of the heater <NUM> in accordance with the printing condition by multiplying the reference value of the heating temperature of the heater <NUM> stored in the memory of the controller <NUM> by the coefficient based on the printing condition stored in the memory of the controller <NUM>.

More specifically, the controller <NUM> controls the application amount of the fixing solution to be applied by the fixing section <NUM> in accordance with the image quality of the toner image. Further, the controller <NUM> controls the heating temperature of the heater <NUM> in accordance with the application amount of the fixing solution to be applied by the fixing section <NUM>. Specifically, in a case that the image quality of the toner image is a high image quality, the controller <NUM> controls the fixing section <NUM> so that the application amount of the fixing solution to be applied by the fixing section <NUM> is increased. Further, in a case that the controller <NUM> increases the application amount of the fixing solution to be applied by the fixing section <NUM>, the controller <NUM> controls the heater <NUM> so that the heating temperature of the heater <NUM> is raised to be high. Furthermore, in a case that the image quality of the toner image is a low image quality, the controller <NUM> controls the fixing section <NUM> so that the application amount of the fixing solution to be applied by the fixing section <NUM> is reduced to be small. Moreover, in a case that the controller <NUM> reduces the application amount of the fixing solution to be applied by the fixing section <NUM>, the controller <NUM> controls the heater <NUM> so that the heating temperature of the heater <NUM> is lowered.

Further, the controller <NUM> obtains a temperature T measured by the temperature sensor <NUM> (step S2).

Next, the controller <NUM> determines whether or not the temperature T is higher than a threshold value T1 (step S3).

The threshold value T <NUM> is, for example, in a range of not less than <NUM> to not more than <NUM>. Specifically, the threshold value T1 is <NUM>.

In a case that the temperature T is higher than the threshold value T (step S3 : YES), the controller <NUM> controls the image carrier <NUM> and the transferring section <NUM> so as to make the conveying velocity of the print medium S by the image carrier <NUM> and the transferring section <NUM> to be a first conveying velocity (step S4).

Further, in the case that the temperature T is higher than the threshold value T1 (step S3 : YES), the controller <NUM> controls the conveying section <NUM> so as to make the conveying velocity of the print medium S by the conveying section <NUM> to be a first velocity (step S5).

It is preferred that the first velocity is a velocity same as the first conveying velocity. Specifically, the controller <NUM> controls the rotation rate (number of rotations) of the driving source <NUM> to thereby make the conveying velocity of the print medium S by the image carrier <NUM> and the transferring section <NUM> to be the first conveying velocity and to thereby make the conveying velocity of the print medium S by the conveying section <NUM> to be the first velocity.

Further, the controller <NUM> controls the heating temperature of the heater <NUM>, in accordance with the temperature T. Specifically, in the case that the temperature T is higher than the threshold value T1 (step S3 : YES), the controller <NUM> controls the heater <NUM> so as to make the heating temperature of the heater <NUM> to be a first heating temperature (step S6).

The first heating temperature is, for example, in a range of not less than <NUM> to not more than <NUM>. It is preferred that the first heating temperature is in a range of not less than <NUM> to not more than <NUM>.

Afterwards, the controller <NUM> executes the printing at the first conveying velocity, the first velocity, and the first heating temperature.

On the other hand, in a case that the temperature T is lower than the threshold value T1 (step S3:NO), the controller <NUM> controls the image carrier <NUM> and the transferring section <NUM> so as to make the conveying velocity of the print medium S by the image carrier <NUM> and the transferring section <NUM> to be a second conveying velocity which is slower than the first conveying velocity (step S7).

By slowing down the conveying velocity of the print medium S by the image carrier <NUM> and the transferring section <NUM>, a period of time during which the print medium S, having the fixing solution applied thereto, passes the heater <NUM> can be made longer.

Therefore, in the case that the temperature T is lower than the threshold value T1, it is possible to secure a long period of time for fixing the toner image to the print medium S.

As a result, it is possible to suppress the lowering in the fixing property of the toner image with respect to the print medium S due to the temperature of the environment in which the image forming apparatus <NUM> is installed.

Note that the second conveying velocity is preferably in a range of not less than <NUM>/<NUM> times to not more than <NUM>/<NUM> times the first conveying velocity.

Further, in the case that the temperature T is lower than the threshold value T1 (step S3: NO), the controller <NUM> controls the conveying section <NUM> so as to make the conveying velocity of the print medium S by the conveying section <NUM> to be a second velocity which is slower than the first velocity (step S8). It is preferred that the second velocity is a velocity which is same as the second conveying velocity.

By slowing down the conveying velocity of the print medium S by the conveying section <NUM>, it is possible to make a period of time, since the fixing solution has been applied to the print medium and until the print medium S is discharged to the outside of the body casing <NUM>, to be long.

With this, in the case that the temperature T is lower than the threshold value T1, it is possible to secure a long period of time for fixing the toner image to the print medium S.

Further, by slowing both the conveying velocity of the print medium S by the conveying section <NUM> and the conveying velocity of the print medium S by the image carrier <NUM> and the transferring section <NUM>, it is possible to increase the period of time during which the print medium S having the fixing solution applied thereto passes the heater <NUM>, while conveying the print medium S at a stable conveying velocity; and it is possible to increase the period of time, since the fixing solution has been applied to the print medium S and until the print medium S is discharged to the outside the body casing <NUM>, to be long.

Further, in the case that the temperature T is lower than the threshold value T1 (step S3: NO), the controller <NUM> may control the heater <NUM> so as to make the heating temperature of the heater <NUM> to be a second heating temperature which is higher than the first heating temperature.

By making the heating temperature of the heater <NUM> to be high, it is possible to fix, in a more ensured manner, the toner image to the print medium S.

The second heating temperature is, for example, in a range of not less than <NUM> to not more than <NUM>. The second heating temperature is preferably in a range of not less than <NUM> to not more than <NUM>.

According to the image forming apparatus <NUM>, in the case that the temperature T is lower than the threshold value T1 (step S3: NO) as depicted <FIG>, the controller <NUM> controls the image carrier <NUM> and the transferring section <NUM> so as to make the conveying velocity of the print medium S by the image carrier <NUM> and the transferring section <NUM> to be the second conveying velocity which is slower than the first conveying velocity (step S7).

With this, it is possible to make the period of time during which the print medium S having the fixing solution applied thereto passes the heater <NUM>.

Further, according to the image forming apparatus <NUM>, as depicted in <FIG>, in the case that the temperature T is lower than the threshold value T1 (step S3: NO), the controller <NUM> controls the conveying section <NUM> so as to make the conveying velocity of the print medium S by the conveying section <NUM> to be the second velocity which is slower than the first velocity (step S7).

With this, it is possible to make the period of time, since the fixing solution has been applied to the print medium S and until the print medium S is discharged to the outside of the body casing <NUM>, to be long.

Further, according to the image forming apparatus <NUM>, the controller <NUM> controls the heating temperature of the heater <NUM> in accordance with the application amount of the fixing solution to be applied by the fixing section <NUM>. Specifically, in a case that the image quality of the toner image is a high image quality, the controller <NUM> controls the fixing section <NUM> so as to increase the application amount of the fixing solution, and the controller <NUM> controls the heater <NUM> so as to make the heating temperature of the heater <NUM> to be high. On the other hand, in a case that the image quality of the toner image is a low image quality, the controller <NUM> controls the fixing section <NUM> so as to reduce the application amount of the fixing solution, and the controller <NUM> controls the heater <NUM> so as to make the heating temperature of the heater <NUM> to be low.

Therefore, in the case that the image quality of the toner image is the high image quality, it is possible to secure a long period of time for fixing the toner image to the print medium S. On the other hand, in the case that the image quality of the toner image is the low image quality, it is possible to suppress the consumption of the fixing solution, and to suppress the consumption of electric power for heating the heater <NUM>.

As a result, it is possible to suppress the lowering in the fixing property of the toner image with respect to the print medium S due to the temperature of the environment in which the image forming apparatus <NUM> is installed, and it is also possible to suppress the consumption amount of the fixing solution and to suppress the consumption amount of the electric power for heating the heater <NUM>.

Further, according to the image forming apparatus <NUM>, as depicted in <FIG>, the temperature sensor <NUM> measures the temperature in the vicinity of the fixing section <NUM>, more specifically, the temperature in the space between the transferring section <NUM> and the fixing section <NUM>.

Therefore, it is possible to control the conveying velocity of the print medium S and the heating temperature of the heater <NUM>, while monitoring the temperature in the vicinity of the fixing section <NUM>.

Claim 1:
An image forming apparatus comprising:
a body casing;
a toner image forming section configured to form a toner image onto a print medium, the toner image forming section including:
an image carrier; and
a transferring section configured to transfer the toner image formed on a surface of the image carrier to the print medium, and convey the print medium together with the image carrier;
a fixing section configured to apply a fixing solution to the print medium conveyed by the image carrier and the transferring section such that the toner image is fixed onto the print medium;
a heater configured to heat the print medium having passed the fixing section;
a temperature sensor configured to measure a temperature in the body casing; and
a controller configured to control the image carrier and the transferring section,
wherein in a case that the temperature measured by the temperature sensor is higher than a predetermined threshold value, the controller is configured to control the image carrier and the transferring section such that a conveying velocity of the print medium by the image carrier and the transferring section becomes a first conveying velocity, and
in a case that the temperature measured by the temperature sensor is lower than the predetermined threshold value, the controller is configured to control the image carrier and the transferring section such that the conveying velocity of the print medium by the image carrier and the transferring section becomes a second conveying velocity slower than the first conveying velocity,
characterized in that the controller is configured to control an application amount of the fixing solution to be applied by the fixing section, in accordance with an image quality of the toner image, and
the controller is configured to control the heating temperature of the heater in accordance with the application amount of the fixing solution to be applied by the fixing section.