JP2017032920A - Image forming apparatus - Google Patents

Abstract

An image forming apparatus capable of humidifying an atmosphere around a charging roller without causing condensation on the charging roller. An image forming apparatus includes a photosensitive drum, a charging roller, a transfer device, a fixing unit, a duct, and a dehumidifying unit. The charging roller 31 a charges the photosensitive drum 30 in order to form a toner image on the photosensitive drum 30. The transfer device 34 transfers the toner image formed on the photosensitive drum 30 onto the paper P. The fixing unit 13 heats the paper P to fix the toner image on the paper P. The duct 18a guides at least one of heat generated from the fixing unit 13 and water vapor to the charging roller 31a. The dehumidifying unit 18c removes at least one of the moisture in the duct 18a and the vicinity of the charging roller 31a. [Selection] Figure 2

Description

  The present invention relates to an image forming apparatus.

  In the image forming apparatus, a charging roller charges the surface of the photosensitive drum. Then, exposure and development are performed on the surface of the photosensitive drum after charging, so that a toner image is formed on the surface of the photosensitive drum. Then, the toner image is transferred and fixed on the paper, thereby forming an image on the paper.

  In such an image forming apparatus, when the humidity of the atmosphere around the charging roller decreases, the resistance value of the charging roller increases and the voltage applied to the charging roller increases. As a result, the voltage applied from the charging roller to the photosensitive drum increases, and discharge occurs on the photosensitive drum.

  As a technique for solving such a problem, an image forming apparatus described in Patent Document 1 is known. The image forming apparatus includes a humidifier that humidifies the atmosphere around the charging roller. The humidifier humidifies the atmosphere around the charging roller, thereby suppressing the humidity of the atmosphere around the charging roller from decreasing.

Japanese Patent Laid-Open No. 5-72871

  However, in the image forming apparatus described in Patent Document 1, it is necessary to newly provide a humidifier and a space for arranging the humidifier is necessary.

  In addition, when the atmosphere around the charging roller is humid when the temperature is low and the humidity is low, condensation occurs on the charging roller. As a result, the generated dew condensation adheres to the photosensitive drum, and a pinhole is generated in the photosensitive belt drum.

  The present invention has been made in view of the above problems, and provides an image forming apparatus capable of humidifying the atmosphere around a charging roller without causing condensation on the charging roller.

  An image forming apparatus according to the present invention is an image forming apparatus that forms an image on a recording medium, and includes an image carrier, a charging unit, a transfer unit, a fixing unit, a duct, and a dehumidifying unit. The charging unit charges the image carrier in order to form a toner image on the image carrier. The transfer unit transfers the toner image formed on the image carrier to the recording medium. The fixing unit heats the recording medium to fix the toner image on the recording medium. The duct guides at least one of heat and water vapor generated from the fixing unit to the charging unit. The dehumidifying unit removes moisture in at least one of the inside of the duct and the vicinity of the charging unit.

  According to the present invention, it is possible to heat and humidify the atmosphere around the charging roller without causing condensation on the charging roller.

1 is a diagram illustrating a configuration of an image forming apparatus according to an exemplary embodiment. It is a figure which shows the structure of a fixing part, a charging device, and a humidifier. It is the figure which showed the relationship between temperature (degreeC), humidity (%), and voltage correction amount (V). It is a figure which shows the relationship between the moisture absorption rate (%) of a dehumidification part, and humidity (%). 5 is a flowchart showing an operation of the image forming apparatus according to the present embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof is not repeated.

  With reference to FIG. 1, an image forming apparatus according to the present embodiment will be described. FIG. 1 is a diagram illustrating a configuration of an image forming apparatus according to the present embodiment.

  The image forming apparatus 1 according to the present embodiment forms an image on a paper P (recording medium) using toner. The image forming apparatus 1 includes a paper feed cassette 5, a paper feed roller 7, a transport roller 9, an image forming unit 11, a fixing unit 13, a paper discharge roller 15, a paper discharge tray 17, and a humidifier 18. And a control unit 19. The image forming apparatus 1 includes a conveyance path 10 and a conveyance path 14.

  The paper feed cassette 5 supplies the paper P to the image forming unit 11. A plurality of sheets P are stacked and stored in the sheet feeding cassette 5. The paper feed roller 7 feeds a plurality of sheets P stored in the paper feed cassette 5 one by one. The transport roller 9 transports the paper P fed by the paper feed roller 7 to the image forming unit 11 along the transport path 10.

  The image forming unit 11 forms an image on the paper P supplied from the paper feed cassette 5. The image forming unit 11 includes a photosensitive drum 30 (image carrier), a charging device 31, an exposure device 32, a developing device 33, a transfer device 34 (transfer unit), a cleaning device 35, and a charge eliminating device 36. Is provided.

  The photosensitive drum 30 has a photosensitive layer on its surface. The charging device 31 uniformly charges the surface of the photosensitive drum 30 to a predetermined potential. The configuration of the charging device 31 will be described later with reference to FIG. The exposure device 32 irradiates the surface of the charged photosensitive drum 30 with laser light, and forms an electrostatic latent image corresponding to the image data on the surface. The developing device 33 develops the electrostatic latent image on the surface of the photosensitive drum 30 as a toner image using toner (for example, black toner).

  The transfer device 34 transfers the toner image on the surface of the photosensitive drum 30 onto the paper P. The transfer device 34 forms a transfer nip region N <b> 2 with the photosensitive drum 30. A transfer voltage is applied to the transfer device 34. As a result, when the toner image on the surface of the photosensitive drum 30 passes through the transfer nip region together with the paper P, the toner image is transferred to the paper P by the electrostatic attraction of the transfer device 34. The sheet P on which the toner image is transferred is sent to the fixing unit 13.

  The cleaning device 35 removes residual toner on the surface of the photosensitive drum 30 after transfer. The neutralization device 36 neutralizes the electric charge charged on the surface of the photosensitive drum 30 after the transfer.

  The fixing unit 13 fixes the toner image transferred to the paper P. The fixing unit 13 fixes the toner image on the paper P by heating and pressurizing the paper P. The configuration of the fixing unit 13 will be described later with reference to FIG. The paper discharge roller 15 discharges the paper P on which the toner image is fixed to the paper discharge tray 17 along the conveyance path 14.

  The humidifying device 18 humidifies the charging device 31 with at least one of heat generated from the fixing unit 13 and water vapor. The configuration of the humidifier 18 will be described later with reference to FIG.

  The control unit 19 controls each unit of the image forming apparatus 1 (the paper feed roller 7, the transport roller 9, the image forming unit 11, the fixing unit 13, the paper discharge roller 15, and the humidifier 18).

  Next, the configuration of the fixing unit 13, the charging device 31, and the humidifying device 18 will be described with reference to FIG. FIG. 2 is a diagram illustrating the configuration of each of the fixing unit 13, the charging device 31, and the humidifying device 18.

  The fixing unit 13 includes a fixing roller 13a, a pressure roller 13b, a heater 13c, and a housing 13d.

  The fixing roller 13a heats the paper P. The fixing roller 13a is rotatably disposed in the housing 13d. The fixing roller 13a is, for example, cylindrical. The heater 13c heats the fixing roller 13a. The heater 13c is disposed, for example, inside the fixing roller 13a. The pressure roller 13b presses the paper P. The pressure roller 13b is rotatably disposed in the housing 13d. The pressure roller 13b is, for example, cylindrical. The pressure roller 13b forms a fixing nip region N1 with the fixing roller 13a.

  The housing 13d accommodates the fixing roller 13a and the pressure roller 13b. The housing 13d has, for example, a rectangular parallelepiped box shape. The housing 13d has a carry-in port 13e, a carry-out port 13f, and an outflow port 13g. The carry-in port 13e is an opening for carrying the paper P into the housing 13d. The carry-out port 13f is an opening through which the paper P is carried out of the housing 13d. The outflow port 13g is an opening through which heat and water vapor generated in the housing 13d flow out of the housing 13d.

  In the fixing unit 13, the paper P that has passed through the transfer nip region N2 is carried into the housing 13d from the carry-in port 13e. The carried paper P passes through the fixing nip area N1. The paper P is heated and pressed by the fixing roller 13a and the pressure roller 13b. As a result, the toner image on the paper P is fixed on the paper P. Then, the paper P that has passed through the fixing nip region N1 is carried out of the housing 13d through the carry-out port 13f. Further, heat generated from the fixing roller 13a and heat and water vapor generated from the paper P when the fixing roller 13a heats the paper P flow out of the housing 13d from the outlet 13g.

  The charging device 31 includes a charging roller 31a (charging unit), an urging spring 31b, a housing 31c, a power source 31d, and a temperature / humidity sensor 31e.

  The charging roller 31a uniformly charges the surface of the photosensitive drum 30 to a predetermined potential. The charging roller 31 a is disposed so as to face the photosensitive drum 30. The charging roller 31a is rotatably disposed in the housing 31c. The charging roller 31a is movable in a direction in which the charging roller 31a approaches or separates from the photosensitive drum 30 within the housing 31c. The charging roller 31a includes a cored bar 31h and a conductive elastic member layer 31i. The cored bar 31h has, for example, a cylindrical shape. The conductive elastic member layer 31i covers the outer peripheral surface of the core bar 31h.

  The urging spring 31b urges the charging roller 31a toward the photosensitive drum 30. As a result, the charging roller 31a forms a voltage application nip region N3 with the photosensitive drum 30.

  The housing 31c houses the charging roller 31a and the urging spring 31b. The housing 31c has, for example, a rectangular parallelepiped box shape. The housing 31c has an opening 31j and an inflow port 31k. The opening 31j exposes the voltage application nip region N3. The inflow port 31k is an opening for allowing heat and water vapor to flow into the housing 31c. The inflow port 31k is provided, for example, on the side surface 31m of the housing 31c. The side surface 31m is one of the outer surfaces of the housing 31c.

  The temperature / humidity sensor 31e detects the temperature and humidity of the atmosphere around the charging roller 31a. The temperature / humidity sensor 31e is disposed, for example, in the vicinity of the charging roller 31a in the housing 31c.

  The power supply 31d outputs a voltage and applies the output voltage to the charging roller 31a. Specifically, the power supply 31d outputs a voltage obtained by superimposing an AC voltage and a DC voltage, for example. The power supply 31 d changes the output voltage according to the control of the control unit 19.

  In the charging device 31, the charging roller 31a is charged by applying the output voltage of the power source 31d. The charging roller 31a uniformly charges the surface of the photosensitive drum 2 via the voltage application nip region N3 while being driven to rotate in accordance with the rotation of the photosensitive drum 30.

  The humidifier 18 includes a duct 18a, a blower 18b, and a dehumidifying unit 18c.

  The duct 18a guides at least one of heat and water vapor generated from the fixing unit 13 to the charging roller 31a. The duct 18 a includes a duct body 18 f and a side surface 31 m of the charging device 31. The duct body 18f is tubular. The duct body 18f has an open end 18d and an open end 18e. One opening end 18 d of the duct body 18 f is connected to the outlet 13 g of the fixing unit 13. The other opening end 18 e of the duct body 18 f is connected to the inlet 31 k of the charging device 31. The inflow port 31k is provided on the side surface 31m of the charging device 31. The heat and water vapor generated from the fixing unit 13 flows inside the duct body 18f and flows into the charging device 31 from the inlet 31k. The heat and water vapor flowing into the charging device 31 are guided to the charging roller 31 a along the side surface 31 m of the charging device 31.

  The blower 18b sends heat and water vapor generated in the fixing unit 13 to the charging roller 31a through the duct 18a by blowing. The blower 18b is disposed in the duct 18a.

  Specifically, when there is no paper P in the fixing unit 13, the blower 18 b sends heat generated from the fixing roller 13 a to the charging device 31 through the duct 18 a. Further, when the paper P passes through the fixing nip region N1, the blower 18b sends heat and water vapor generated from the paper P to the charging device 31 through the duct 18a together with heat generated from the fixing roller 13a. The heat and water vapor sent to the charging device 31 flows into the casing 31c of the charging device 31 and flows near the charging roller 31a.

  The dehumidifying unit 18c removes excess moisture contained in the atmosphere around the charging roller 31a. Excess humidity is humidity above a predetermined humidity. The predetermined humidity is humidity that can cause condensation on the charging roller 31a. The dehumidifying unit 18c suppresses a rapid increase in the humidity of the atmosphere around the charging roller 31a and suppresses the occurrence of condensation on the charging roller 31a.

  The dehumidification part 18c is arrange | positioned in the duct 18a, for example. In this case, the dehumidifying unit 18c removes excess moisture contained in the atmosphere around the charging roller 31a by removing excess moisture in the duct 18a. Note that the dehumidifying unit 18 c may be disposed in the vicinity of the charging roller 31 a in the housing 31 c of the charging device 31. In this case, the dehumidifying unit 18c removes moisture near the charging roller 31a, thereby removing excess moisture contained in the atmosphere around the charging roller 31a. The dehumidifying part 18c is preferably B-type silica gel, for example. The moisture absorption characteristics of the dehumidifying part 18c will be described later with reference to FIG.

  The humidifier 18 heats and humidifies the atmosphere around the charging roller 31a with at least one of heat generated from the fixing unit 13 and water vapor. Therefore, since the existing humidification heating source (that is, the fixing unit 13) is used, it is not necessary to secure a new space for arranging the humidifier 18. When the atmosphere around the charging roller 31a is humidified by heat, the atmosphere around the charging roller 31a may be heated by heat. If the temperature of the atmosphere increases, the humidity of the atmosphere also increases.

  The control unit 19 controls the output voltage of the power supply 31d so that the charging voltage charged on the charging roller 31a becomes a desired voltage.

  By the way, the constituent material of the charging roller 31a is affected by the temperature and humidity of the atmosphere around the charging roller 31a. As a result, the resistance value of the charging roller 31a increases when the atmosphere is at low temperature and low humidity, and decreases when the atmosphere is at high temperature and high humidity. Further, the charging capability of the photosensitive drum 30 and the charging characteristics of the charging roller 31a vary depending on the temperature and humidity of those atmospheres.

  Therefore, the control unit 19 corrects the output voltage of the power supply 31d based on the detection value of the temperature / humidity sensor 31e so that the charging voltage of the charging roller 31a becomes a desired voltage. The detection value of the temperature / humidity sensor 31e indicates the temperature and humidity of the atmosphere around the charging roller 31a. That is, the control unit 19 outputs a voltage given by the sum of the desired voltage and the voltage correction amount from the power supply 31d. Further, the control unit 19 controls the voltage correction amount based on the detection value of the temperature / humidity sensor 31e. A specific example of the correction amount will be described later with reference to FIG.

  In particular, when the atmosphere around the charging roller 31a is low temperature and low humidity, the voltage correction amount becomes large. When the voltage correction amount increases, the surface potential of the photosensitive drum 30 tends to vary.

  For this reason, the controller 19 prevents the humidifier 18 so that the temperature of the atmosphere around the charging roller 31a does not become a predetermined temperature (for example, 18 ° C.) or less and the humidity of the atmosphere does not become the predetermined humidity (for example, 30%) or less. To control. That is, the control unit 19 operates the blower 18b when the temperature detected by the temperature / humidity sensor 31e is equal to or lower than the predetermined temperature and the humidity detected by the temperature / humidity sensor 31e is equal to or lower than the predetermined humidity. Therefore, the heat and water vapor generated from the fixing unit 13 by the blower 18b is sent to the charging device 31 through the duct 18a. The atmosphere around the charging roller 31a is heated and humidified by the sent heat and water vapor. As a result, an increase in the voltage correction amount is suppressed.

  Moreover, the control part 19 stops the air blower 18b, when the detection temperature of the temperature / humidity sensor 31e is not below predetermined temperature, or when the detection humidity of the temperature / humidity sensor 31e is not below predetermined humidity. This is because the voltage correction amount does not increase to such an extent that the surface potential of the photosensitive drum 30 varies.

  Further, when the image forming apparatus 1 is turned on, the control unit 19 determines whether or not the temperature detected by the temperature / humidity sensor 31e is equal to or lower than a predetermined temperature and the humidity detected by the temperature / humidity sensor 31e is equal to or lower than a predetermined humidity. . This determination is also referred to as temperature / humidity determination. And the control part 19 controls the air blower 18b based on a determination result. That is, when it is determined that the temperature detected by the temperature / humidity sensor 31e is equal to or lower than the predetermined temperature and the temperature detected by the temperature / humidity sensor 31e is equal to or lower than the predetermined humidity, the control unit 19 operates the blower 18b. On the other hand, when the control unit 19 determines that the temperature detected by the temperature / humidity sensor 31e is not equal to or lower than the predetermined temperature or the temperature detected by the temperature / humidity sensor 31e is not equal to or lower than the predetermined humidity, the control unit 19 does not operate (that is, stops) the blower 18b.

  A specific example of the voltage correction amount will be described with reference to FIG. FIG. 3 is a diagram showing the relationship between temperature (° C.), humidity (%), and voltage correction amount (V). The temperature and humidity shown in FIG. 3 are the temperature and humidity of the atmosphere around the charging roller 31a, respectively.

  As shown in FIG. 3, the voltage correction amount increases as the temperature decreases and decreases as the temperature increases. Further, the voltage correction amount increases as the humidity decreases and decreases as the humidity increases. Specifically, the voltage correction amount is zero at the reference temperature and humidity (temperature 22 ° C. and humidity 60%). If the temperature or humidity rises from the reference temperature and humidity, the voltage correction amount becomes an addition amount with respect to a desired voltage, and the absolute value thereof increases. On the other hand, if the temperature or humidity decreases from the reference temperature and humidity, the voltage correction amount becomes a subtraction amount with respect to the desired voltage, and its absolute value increases. In particular, as the temperature and humidity both decrease, the absolute value of the voltage correction amount increases.

  Specifically, when the detected value of the temperature / humidity sensor 31e is 0 ° C. and 10%, the voltage correction amount is 400V. At this time, when the control unit 19 controls the charging voltage of the charging roller 31a to 1500 V (desired voltage), the output voltage of the power supply 31d is the sum of 1500 V (desired voltage) and 400 V (voltage correction amount). To 1900V. As a result, a voltage of 1900 V is applied to the charging roller 31a. The charging voltage of the charging roller 31a is 1500V depending on the charging characteristics of the charging roller 31a.

  With reference to FIG. 4, the moisture absorption characteristic of the dehumidification part 18c is demonstrated. FIG. 4 is a diagram illustrating the relationship between the moisture absorption rate (%) and the humidity (%) of the dehumidifying unit 18c. The humidity shown in FIG. 4 is the humidity of the atmosphere around the dehumidifying part 18c. In FIG. 4, the vertical axis indicates the moisture absorption rate, and the horizontal axis indicates the humidity.

  As shown in FIG. 4, the moisture absorption rate of the dehumidifying part 18c changes according to the humidity of the atmosphere around the dehumidifying part 18c. In particular, the higher the humidity, the higher the humidity, the dehumidifying part 18c has a higher moisture absorption rate and absorbs more water. On the other hand, the dehumidifying unit 18c has a lower moisture absorption rate as the humidity is lower, and releases the absorbed moisture. Therefore, the dehumidifying unit 18c can maintain the humidity of the atmosphere around the charging roller 31a within a certain range.

  The operation of the image forming apparatus 1 will be described with reference to FIG. FIG. 5 is a flowchart showing the operation of the image forming apparatus 1.

  In step S1, the image forming apparatus 1 is powered on. In step S2, the control unit 19 determines whether the temperature detected by the temperature / humidity sensor 31e is equal to or lower than a predetermined temperature and whether the temperature detected by the temperature / humidity sensor 31e is equal to or lower than the predetermined humidity. If the determination result is affirmative (YES), the process proceeds to step S3. If the determination result is negative (NO), the process proceeds to step S4.

  In step S3, the control part 19 operates the air blower 18b. Accordingly, heat and water vapor generated from the fixing unit 13 are sent to the charging device 31 through the duct 18a. Then, the atmosphere around the charging roller 31a is heated and humidified. As a result, the temperature of the atmosphere around the charging roller 31a is reduced to a predetermined temperature or lower, and the humidity of the atmosphere is suppressed to a predetermined humidity or lower. Further, the moisture absorption by the dehumidifying unit 18c suppresses a rapid increase in the humidity of the atmosphere around the charging roller 31a, thereby suppressing the occurrence of condensation on the charging roller 31a. Then, the process returns to step S2.

  In step S4, the control unit 19 does not operate (that is, stops) the blower 18b. Then, the process returns to step S2.

  The embodiment of the present invention has been described above with reference to the drawings (FIGS. 1 to 5). However, the present invention is not limited to the above-described embodiment, and can be implemented in various modes without departing from the gist thereof (for example, (1) to (3) shown below). In order to facilitate understanding, the drawings schematically show each component as a main component, and the thickness, length, number, and the like of each component shown in the drawings are different from the actual for convenience of drawing. . In addition, the material, shape, dimensions, and the like of each component shown in the above embodiment are merely examples, and are not particularly limited, and various changes can be made without departing from the effects of the present invention. is there.

  (1) In the above embodiment, the temperature / humidity determination is performed when the image forming apparatus 1 is turned on. However, the timing at which the temperature / humidity determination is performed is not limited to when the image forming apparatus 1 is turned on. For example, the temperature and humidity determination may be performed before the image forming unit 11 forms an image on the sheet P, that is, before the charging device 31 charges the photosensitive drum 30.

  (2) In the above embodiment, the opening end 18d of the duct 18a is connected to the outlet 13g of the fixing unit 13, but the opening end 18d is arranged to be connected to the outlet 13g of the fixing unit 13. It is not limited. For example, the opening end 18 d may be disposed near the carry-out port 13 f of the fixing unit 13. In this case, at least one of heat and water vapor generated from the paper P carried out from the carry-out port 13f is taken into the opening end 18d and guided to the charging device 31 through the duct 18a. In this case, the outlet 13g of the fixing unit 13 is omitted.

  (3) In the above embodiment, the image forming apparatus 1 includes the blower 18b, but the image forming apparatus 1 may not include the blower 18b. When the image forming apparatus 1 does not include the blower 18b, the heat and water vapor generated from the fixing unit 13 are naturally diffused and guided to the charging device 31 through the duct 18a.

DESCRIPTION OF SYMBOLS 13 Fixing part 18a Duct 18b Air blower 18c Dehumidifying part 19 Control part 30 Photosensitive drum 31a Charging roller 31e Temperature / humidity sensor 34 Transfer apparatus

Claims (7)

An image forming apparatus for forming an image on a recording medium,
An image carrier;
A charging unit for charging the image carrier to form a toner image on the image carrier;
A transfer unit that transfers the toner image formed on the image carrier to the recording medium;
A fixing unit that heats the recording medium and fixes the toner image to the recording medium;
A duct for guiding at least one of heat and water vapor generated from the fixing unit to the charging unit;
An image forming apparatus comprising: a dehumidifying unit that removes moisture in at least one of the inside of the duct and the vicinity of the charging unit. Further comprising a blower disposed in the duct;
The image forming apparatus according to claim 1, wherein the blower sends the heat and the water vapor to the charging unit by blowing air.   The dehumidifying part releases moisture that has been absorbed by increasing the moisture absorption rate as the humidity around the dehumidifying unit is higher and decreasing the moisture absorption rate as the humidity around the dehumidifying unit is lower. The image forming apparatus according to claim 2. A temperature and humidity sensor for detecting the temperature and humidity around the charging unit;
A control unit for controlling the blower;
Further comprising
The controller determines whether the temperature detected by the temperature / humidity sensor is equal to or lower than a predetermined temperature and whether the humidity detected by the temperature / humidity sensor is equal to or lower than a predetermined humidity. The image forming apparatus according to claim 1, wherein the image forming apparatus is operated.   The image forming apparatus according to claim 4, wherein the control unit performs the determination when the image forming apparatus is powered on. A housing that houses the charging unit;
The housing has an inlet on one of its outer surfaces,
The duct includes a cylindrical duct body and the one surface,
The image forming apparatus according to claim 1, wherein one opening end of the duct main body is connected to the inflow port of the one surface.   The image forming apparatus according to claim 6, wherein the one surface is a side surface of the housing.

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