JP2012118160A - Image forming apparatus and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that suppresses the occurrence of toner scattering at a line image portion included in an output image.SOLUTION: An image forming apparatus includes: a photoreceptor 41 on which an electrostatic latent image is formed; a developing part 44 that allows toner to be attached to the photoreceptor 41; a primary transfer part 51; and a moisture supply part 60. The primary transfer part 51 transfers the toner attached to the photoreceptor to an intermediate transfer belt 50. The moisture supply part 60 supplies moisture to the toner attached to the photoreceptor 41 by the developing part 44 before the transfer of the toner to the intermediate transfer belt 50 by the primary transfer part 51.

Description

  The present invention relates to an image forming apparatus and an image forming method for transferring toner adhering to a photoreceptor to a transfer material.

  In general, in an image forming apparatus and an image forming method, first, a photosensitive member is charged and the charge is erased in accordance with an original image, so-called exposure is performed to form an electrostatic latent image. Toner is attached to the electrostatic latent image on the photoreceptor using a developing unit. The toner attached to the photoconductor is transferred to a transfer material such as an intermediate transfer belt or paper to form an image.

  Here, when the charge amount of the toner is higher than an appropriate value, toners having the same polarity repel each other, and transfer dust may occur when transferring from the photosensitive member to the transfer material. A technique for suppressing the generation of the transfer dust is described in Patent Document 1, for example. In the image forming apparatus described in Patent Document 1, the charge amount of the toner formed on the photosensitive member and the intermediate transfer belt is reduced to an appropriate value using a static eliminator, thereby preventing the toners from repelling each other. is doing.

  In addition, a technique has been proposed in which an air conditioner is arranged in the apparatus, and the humidity and temperature in the apparatus are managed by the air conditioner, so that the charge amount of toner at the time of transfer is set to an appropriate value.

JP 2006-138891 A

  In general, in a line image, the charge is likely to concentrate, and the height of the toner (toner image) that collects toner and adheres to the photoconductor becomes higher than that of the surface image. Transfer dust may occur.

  When the image forming apparatus described in Patent Document 1 is used, when the charge amount of the line image is lowered to an appropriate value, the charge amount of the surface image is lower than the appropriate value. Therefore, there is a problem that the charge amount of the line image cannot be lowered to an appropriate value, and toner scattering occurs when the line image is transferred. Further, if the developability is lowered and the height of the toner image of the line image on the photosensitive member is lowered, there is a problem that the density of the surface image becomes insufficient and the image quality is lowered.

  In an image forming apparatus provided with an air conditioner for controlling humidity and temperature in the apparatus, not only the toner image before being transferred from the developed photosensitive member to the transfer material, but also when charging or exposing the photosensitive member. In addition, it affects the humidity and temperature during development that causes toner to adhere to the photoreceptor. For this reason, even when the charge amount of the toner before transfer is an appropriate value, the charge amount at the time of development is reduced, and the toner is difficult to adhere to the photoreceptor.

  In view of the above problems, an object of the present invention is to provide an image forming apparatus and an image forming method capable of preventing toner scattering in a line image portion even when an image having a line image is output. is there.

  In order to solve the above problems and achieve the object of the present invention, an image forming apparatus of the present invention includes a photosensitive member on which an electrostatic latent image is formed, and a developing unit that attaches toner to the electrostatic latent image of the photosensitive member. And a transfer portion that transfers the toner adhered to the photosensitive member to a transfer material. A water supply unit is provided for supplying water to the toner adhered to the photoconductor by the developing unit before transferring the toner onto the transfer material.

In addition, the image forming method of the present invention includes the following steps (1) to (3).
(1) A step of forming an electrostatic latent image on the photosensitive member.
(2) A step of attaching toner to the electrostatic latent image formed on the photosensitive member.
(3) A step of supplying moisture from the moisture supply unit before the step of transferring the toner to the transfer material with respect to the toner adhered to the photosensitive member.

  According to the image forming apparatus and the image forming method configured as described above, the liquid crosslinking force between the toners can be increased by supplying moisture to the toner before being developed and transferred to the photoconductor. Thereby, even when the height of the toner image is high, it is possible to prevent the occurrence of toner scattering when transferring to the transfer material.

1 is an overall configuration diagram showing an embodiment of an image forming apparatus of the present invention. 1 is a schematic configuration diagram illustrating a main part according to an image forming apparatus of the present invention. It is a schematic block diagram which shows the water vapor | steam generation means concerning the image forming apparatus of this invention. FIG. 6 is a schematic diagram illustrating a state where moisture is supplied to toner. 2 is a block diagram showing a control system of an embodiment of the image forming apparatus of the present invention. FIG. It is a graph which shows the moisture content and power consumption which generate | occur | produce in 1 second by a water vapor | steam generating means. 3 is a flowchart showing processing of a water supply unit according to the image forming apparatus of the present invention.

Embodiments of the image forming apparatus and the image forming method of the present invention (hereinafter referred to as “this example”) will be described below with reference to FIGS. In addition, the same code | symbol is attached | subjected to the common member in each figure. The present invention is not limited to the following form.
The description will be given in the following order.
1. 1. Configuration example of image forming apparatus 2. Operation of image forming apparatus Comparison of image forming apparatus of this example and conventional example

1. Configuration Example of Image Forming Apparatus First, a configuration example of an image forming apparatus will be described with reference to FIG.
FIG. 1 is an overall configuration diagram showing the image forming apparatus of this example.

  As shown in FIG. 1, the image forming apparatus 1 forms an image on a sheet by an electrophotographic method, and has four colors of yellow (Y), magenta (M), cyan (C), and black (Bk). This is a tandem color image forming apparatus that superimposes toner. The image forming apparatus 1 includes a document transport unit 10, a paper storage unit 20, an image reading unit 30, an image forming unit 40, an intermediate transfer belt 50, a secondary transfer unit 70, and a fixing unit 80.

  The document transport unit 10 includes a document feeder 11 on which a document is set and a plurality of rollers 12. The documents G set on the document feeder 11 of the document transport unit 10 are transported one by one to the reading position of the image reading unit 30 by the plurality of rollers 12. The image reading unit 30 reads an image of the document G transported by the document transport unit 10 or the document placed on the document table 13 and generates an image signal.

  The paper storage unit 20 is disposed in the lower part of the apparatus main body, and a plurality of paper storage units 20 are provided according to the size of the paper S. The sheet S is fed by the sheet feeding unit 21 and sent to the transport unit 23, and is transported by the transport unit 23 to the secondary transfer unit 70 that is a transfer position. Further, a manual feed portion 22 is provided in the vicinity of the paper storage portion 20. From the manual feed section 22, paper of a size not stored in the paper storage section 20, tag paper having a tag, special paper such as an OHP sheet is sent to the transfer position.

  An image forming unit 40 and an intermediate transfer belt 50 are disposed between the image reading unit 30 and the paper storage unit 20. The image forming unit 40 includes four image forming units 40Y, 40M, 40C, and 40K in order to form toner images of respective colors of yellow (Y), magenta (M), cyan (C), and black (Bk). .

  The first image forming unit 40Y forms a yellow toner image, and the second image forming unit 40M forms a magenta toner image. The third image forming unit 40C forms a cyan toner image, and the fourth image forming unit 40K forms a black toner image. Since these four image forming units 40Y, 40M, 40C, and 40K have the same configuration, only the first image forming unit 40Y will be described here.

  The first image forming unit 40Y includes a drum-shaped photoconductor 41, a charging unit 42 arranged around the photoconductor 41, an exposure unit 43, a developing unit 44, and a cleaning unit 45. The photoreceptor 41 is rotated counterclockwise by a drive motor (not shown). The charging unit 42 applies a charge to the photoconductor 41 and uniformly charges the surface of the photoconductor 41. The exposure unit 43 forms an electrostatic latent image on the photoconductor 41 by performing an exposure operation on the surface of the photoconductor 41 based on image data read from the document G.

  The developing unit 44 attaches yellow toner to the electrostatic latent image formed on the photoconductor 41. As a result, a yellow toner image is formed on the surface of the photoreceptor 41. The developing unit 44 of the second image forming unit 40M attaches magenta toner to the photoconductor 41, and the developing unit 44 of the third image forming unit 40C attaches cyan toner to the photoconductor 41. Then, the developing unit 44 of the fourth image forming unit 40K adheres black toner to the photoconductor 41.

  The toner adhered on the photoconductor 41 is transferred to an intermediate transfer belt 50 showing an example of a transfer material. The cleaning unit 45 removes the developer remaining on the surface of the photoreceptor 41. Further, as shown in FIG. 2, the image forming unit 40 is provided with a moisture supply unit 60. Details of the moisture supply unit 60 will be described later.

  The intermediate transfer belt 50 is formed in an endless shape, and is rotated clockwise by a drive motor (not shown) in a direction opposite to the rotation direction of the photoconductor 41. A primary transfer portion 51 is provided at a position on the intermediate transfer belt 50 that faces the photoreceptor 41 of each of the image forming units 40Y, 40M, 40C, and 40K. The primary transfer unit 51 transfers the toner image formed on the photoreceptor 41 to the intermediate transfer belt 50 by applying the opposite polarity to the toner to the intermediate transfer belt 50.

  As the intermediate transfer belt 50 rotates, the toner images formed by the four image forming units 40Y, 40M, 40C, and 40K are sequentially transferred onto the surface of the intermediate transfer belt 50. As a result, yellow, magenta, cyan, and black toner images are superimposed on the intermediate transfer belt 50 to form a color image.

  A secondary transfer unit 70 is disposed near the intermediate transfer belt 50 and downstream of the conveyance unit 23. The secondary transfer unit 70 is formed in a roller shape and presses the sheet S sent by the transport unit 23 toward the intermediate transfer belt 50. The secondary transfer unit 70 transfers the color image formed on the intermediate transfer belt 50 onto the paper S sent by the transport unit 23. A fixing unit 80 is provided on the paper transfer side of the secondary transfer unit 70. The fixing unit 80 pressurizes and heat-fixes the toner image transferred to the paper S.

  A switching gate 24 is disposed downstream of the fixing unit 80. The switching gate 24 switches the transport path of the paper S that has passed through the fixing unit 80. That is, the switching gate 24 moves the paper S straight when performing face-up paper discharge in single-sided image formation. As a result, the paper S is discharged by the pair of paper discharge rollers 25. The switching gate 24 guides the paper S downward when face-down paper discharge and double-sided image formation in single-sided image formation.

When face-down paper discharge is performed, the paper S is guided downward by the switching gate 24, and then the front and back sides are reversed by the paper reverse conveyance unit 26 and conveyed upward. As a result, the paper S is discharged by the pair of paper discharge rollers 25.
When double-sided image formation is performed, the sheet S is guided downward by the switching gate 24, the front and back sides are reversed by the sheet reversing conveyance unit 26, and sent again to the transfer position by the refeed path 27.

  Further, a post-processing device that folds the paper S or performs stapling processing or the like on the paper S may be disposed downstream of the pair of paper discharge rollers 25.

[Moisture supply unit]
Next, the water supply unit 60 will be described with reference to FIGS.
FIG. 2 is a schematic configuration diagram showing a main part of the image forming apparatus of this example.
As shown in FIG. 2, the image forming unit 40 is provided with a moisture supply unit 60. The water supply unit 60 includes a water vapor generating unit 61, a duct 62 through which water vapor generated by the water vapor generating unit 61 passes, and a blower unit 63 that sends water vapor and wind to the duct 62.

FIG. 3 is a schematic configuration diagram showing the water vapor generating means 61.
As shown in FIG. 3, the water vapor generating means 61 includes a tank 65 for storing water, and an ultrasonic transducer 66 provided in the tank 65. The ultrasonic vibrator 66 is connected to a drive circuit 67 and generates ultrasonic vibration when a voltage is applied. When the ultrasonic vibrator 66 vibrates ultrasonically, a fine water column stands on the surface of the water W stored in the tank 65, and water evaporates from the water to generate water vapor.

  In this example, although the example using the ultrasonic transducer | vibrator 66 as the water vapor | steam generation means 61 was demonstrated, it is not limited to this. As the water vapor generation means 61, for example, water vapor may be generated by heating the water W stored in the tank 65 using a heater.

  However, the steam generating means using a heater not only has a high temperature around the steam generating means, but also consumes more power than the ultrasonic vibrator 66. Therefore, it is preferable that the water vapor generating means 61 uses an ultrasonic vibrator 66 that consumes less power and does not easily reach a high temperature.

  As shown in FIG. 2, the tank 65 is open above the tank 65 and is provided with a blowing means 63. In this example, a fan is used as the air blowing means 63. When the air blowing means 63 is driven, water vapor and wind generated from the water vapor generating means 61 are fed into the duct 62.

  The duct 62 is branched in four directions from the blower 63 toward the respective photoreceptors 41 of the four image forming units 40Y, 40M, 40C, and 40K. At the end of the duct 62 opposite to the air blowing means 63, four discharge ports 62a for discharging water vapor are formed.

  The discharge port 62 a is disposed so as to face the outer peripheral surface of the photoconductor 41 between the developing unit 44 and the primary transfer unit 51. Further, the length of the discharge port 62a in the width direction is set to be substantially equal to the length of the photoconductor 41 in the axial direction (width direction). Therefore, moisture is sprayed uniformly on the photoconductor 41 in the width direction. That is, moisture can be supplied from the moisture supply unit 60 before being transferred by the primary transfer unit 51 to the toner adhering to the photoreceptor 41.

FIG. 4 is a schematic diagram illustrating a state in which moisture is supplied to the toner.
As shown in FIG. 4, when water is supplied to the toner from the water supply unit 60, the water W adheres between the toners T, and the liquid crosslinking force between the toners T can be increased. Thereby, even when the height of the toner image is high, it is possible to prevent the toner image from collapsing due to contact with the intermediate transfer belt 50 or repelling of toners having the same polarity.

  Further, according to the image forming apparatus 1 of this example, moisture is supplied only to the toner before being developed on the photoconductor 41 and transferred to the intermediate transfer belt 50. The moisture remaining on the photoconductor 41 is removed by the cleaning unit 45. For this reason, the moisture discharged from the moisture supply unit 60 does not affect the photoreceptor 41 immediately before exposure, the toner before development, or the like. As a result, the charging / exposure process and the development process can be reliably performed, and deterioration in image quality can be prevented.

  In addition, a thermometer 108 and a hygrometer 109, which are examples of detection means described later, are provided in the vicinity of the discharge port 62a of the duct 62 (see FIG. 5). Specifically, it is disposed at a location where moisture is supplied in the duct 62 or on the surface of the photoreceptor 41. Accordingly, it is possible to detect a location (temperature and humidity) in the duct 62 and / or in the photosensitive member 41 where moisture is supplied, that is, in the vicinity of the outlet 62a of the duct 62.

[Hardware Configuration of Each Part of Image Forming Apparatus]
Next, a hardware configuration of each unit of the image forming apparatus 1 of this example will be described with reference to FIG.
FIG. 5 is a block diagram showing a control system of the image forming apparatus 1 of this example.

  As shown in FIG. 5, the image forming apparatus 1 is used as, for example, a CPU (Central Processing Unit) 101, a ROM (Read Only Memory) 102 for storing a program executed by the CPU 101, and a work area of the CPU 101. RAM (Random Access Memory) 103. Further, it has a hard disk drive (HDD) 104 as a mass storage device and an operation display unit 105. As the ROM 102, an electrically erasable programmable ROM is usually used.

  The CPU 101 is an example of a control unit, and is connected to the ROM 102, the RAM 103, the HDD 104, and the operation display unit 105 via the system bus 107, and controls the entire apparatus. The CPU 101 is connected to the image reading unit 30, the image processing unit 110, the image forming unit 40, the paper feeding unit 21, and the water supply unit 60 via the system bus 107. Further, a thermometer 108 and a hygrometer 109 for setting the operation of the moisture supply unit 60 are connected to the CPU 101.

  The HDD 104 stores image data of an original image obtained by reading by the image reading unit 30, or stores output image data and the like. The operation display unit 105 is a touch panel including a display such as a liquid crystal display (LCD) or an organic ELD (Electro Luminescence Display). The operation display unit 105 displays an instruction menu for the user, information about the acquired image data, and the like. Further, the operation display unit 105 includes a plurality of keys, and receives input of various instructions, data such as characters and numbers by a user's key operation, and outputs an input signal.

  The image reading unit 30 optically reads a document image and converts it into an electrical signal. For example, when reading a color original, image data having luminance information of 10 bits for each of RGB per pixel is generated. Image data generated by the image reading unit 30 and image data transmitted from a PC (personal computer) 120 showing an example of an external device connected to the image forming apparatus 1 are sent to the image processing unit 110 for image processing. Is done. The image processing unit 110 performs processes such as analog processing, A / D conversion, shading correction, and image compression on the received image data.

  In this example, a personal computer is used as an external device. However, the present invention is not limited to this, and various other devices such as a facsimile device can be used as the external device.

  For example, when color printing is executed by the image forming apparatus 1, R, G, B image data generated by the image reading unit 30 or the like is input to the color conversion LUT in the image processing unit 110. Then, the image processing unit 110 performs color conversion on the R, G, and B data to Y, M, C, and Bk image data. Then, correction of gradation reproduction characteristics, screen processing such as halftone dots with reference to the density correction LUT, or edge processing for emphasizing thin lines is performed on the color-converted image data.

  The image forming unit 40 receives the image data processed by the image processing unit 110 and forms an image on the paper S.

  Further, a thermometer 108 and a hygrometer 109 serving as detection means detect temperature data and humidity data in the vicinity of the outlet 62 a of the duct 62. The detected temperature data and humidity data are transmitted to the CPU 101. Then, the CPU 101 controls the outputs of the water vapor generating means 61 and the air blowing means 63 in the water supply unit 60 based on the temperature and humidity data obtained by the thermometer 108 and the hygrometer 109 and the process speed v. Note that the process speed in this example corresponds to the rotational speed v of the photoconductor 41.

[How to set the moisture supply unit]
Next, with reference to FIG. 6, the setting method of the output of the water vapor | steam generation means 61 of the moisture supply part 60 and the ventilation means 63 is demonstrated.

  First, the required amount of moisture K is assumed as follows. For example, when toner with a diameter of 6 μm adheres to the photoconductor 41 in a single layer, that is, close-packed with a flat surface, for example, water having a diameter of 2 (μm) and a thickness of 1 (μm) adheres to the contact portion between the toners. The amount of water K to be used is 0.011 (g) per area (297 mm × 210 mm) of one A4 size paper S. The moisture amount K is variously set according to the size of the paper S and the required image quality.

The length in the axial direction (width direction) of the photoconductor 41 is set to 297 mm, which is equal to the length in the longitudinal direction of the A4 size paper S. Here, as described above, the length in the width direction of the discharge port 62 a of the duct 62 in the moisture supply unit 60 is set to be substantially equal to the length in the axial direction (width direction) of the photoconductor 41. ing. That is, moisture is uniformly supplied to the entire width of the photoconductor 41. Therefore, the amount of water k (g / sec) required per second is the amount of water K (g) per sheet S, the process speed v (mm / sec) at which the photoconductor 41 performs processing, and the sheet S. From the length H (mm) in the short direction, the following formula 1 is used.
[Formula 1] K × (v / H) = k

  Therefore, when the process speed v is 300 mm / sec, the amount of water necessary for one second per one color of the photoreceptor 41 of the image forming units 40Y, 40M, 40C, and 40K, that is, the water supply speed k is 0.011 g × ( 300/210) = 0.157 g / sec. Further, when the process speed v is 150 mm / sec in the thick paper mode or the like, 0.011 g × (150/210) = 0.00786 g / sec.

  In the case of full-color printing, a water amount of 4 × k for four colors is required. Therefore, when the process speed v is 300 (mm / sec), a water supply speed of 0.0628 (g / sec) is required. Thus, when the process speed v is 150 (mm / sec), a moisture supply speed of 0.0314 (g / sec) is required.

  Note that when the size of the paper S is A3 size, the width in the width direction of the photoconductor 41 is equal to the length in the short direction of the paper. It is determined by the length in the longitudinal direction.

FIG. 6 is a graph showing the power consumption (W) in the water vapor generating means 61 and the amount of water generated per second, the so-called water supply rate (g / sec).
As shown in FIG. 6, when the process speed is 300 (mm / sec), if the ultrasonic transducer 66 is driven with power consumption of about 25 W, 0.0628 (g / sec) can be generated. it can.

  Further, if the amount of water in the duct 62 is too large, the duct 62 and the photoreceptor 41 may be condensed. Therefore, it is necessary to set the air volume of the air blowing means 63 so that the inside of the duct 62 is not condensed. Next, a method for setting the air volume of the blower 63 will be described.

  First, the temperature (state) of the photoconductor 41 near the discharge port 62a of the duct 62, that is, inside the duct 62 and to which moisture is supplied is detected by the thermometer 108, and the saturated water vapor amount M with respect to the detected temperature is calculated. Further, the current water vapor amount N near the outlet 62 a of the duct 62 is calculated by the thermometer 108 and the hygrometer 109. The amount of water vapor L generated per unit volume is the difference between the saturated water vapor amount M and the current water vapor amount N. When the amount of water vapor exceeding this difference is generated, the duct 62 is condensed.

For example, when the temperature detected by the thermometer 108 is 25 ° C. and the humidity detected by the hygrometer 109 is 50%, the saturated water vapor amount M is 23.0 (g / m ³ ), and the current water vapor amount N is 23.0 × 0.50 = 11.5 (g / m ³ ). Therefore, the water vapor amount L generated per unit volume is the difference between the saturated water vapor amount M and the current water vapor amount N, 23.0-11.5 = 11.5 (g / m ³ ), that is, the unit volume (1 Per liter) is 0.0115 (g / l).

Further, when the temperature detected by the thermometer 108 is 15 ° C. and the humidity detected by the hygrometer 109 is 75%, the saturated water vapor amount M is 12.8 (g / m ³ ), and the current water vapor amount N is 12.8 × 0.70 = 8.96 (g / m ³ ). Therefore, the amount L of water vapor generated per unit volume is 3.84 (g / m ³ ), that is, 0.00384 (g / l).

For this reason, the air volume R sent into the duct 62 by the air blowing means 63 is determined from the amount of water 4k (showing the case of four-color full color printing) generated by the water vapor generating means 61 per second and the amount of water vapor L generated per unit volume. Calculated by Equation 2.
[Formula 2] R = 4 k / L

  Here, when the process speed v is 300 (mm / sec), the temperature is 25 ° C., and the humidity is 50%, as described above, the amount of water 4k generated by the water vapor generating means 61 per second is 0.0628 (g / sec), and the required water vapor amount L per unit volume is 0.0115 (g / l). Therefore, the air volume R (l / sec) sent into the duct 62 by the air blowing means 63 is 0.0628 / 0.0115 = 5.46 (l / sec) from Equation 2.

  This is a setting in which the relative humidity in the duct 62 is 100%. Actually, it is preferable to set the duct 62 slightly lower than the relative humidity so as not to condense, so that the air volume R is slightly increased so that 6.0 (l / sec) air is sent into the duct 62. Is set to the output of the air blowing means 63.

  As described above, according to the image forming apparatus 1 of this example, the outputs of the water vapor generating means 61 and the air blowing means 63 are set according to the process speed v, the size of the paper S, the temperature data near the duct 62 and the humidity data. ing. As a result, an optimal amount of water can be supplied to the toner without causing condensation in the duct 62.

2. Operation of Image Forming Apparatus Next, the operation of the image forming apparatus 1 of this example will be described with reference to FIG. This operation can be viewed as an image forming method performed by the image forming apparatus and a series of programs for causing the computer to realize the image forming method.
FIG. 7 is a flowchart showing an image forming operation in the image forming apparatus 1 of this example.

  As shown in FIG. 7, the operation display unit 105 or a PC as an external device is operated to instruct the CPU 101 to start printing (step S1). Next, the CPU 101 acquires process speed data input to the operation display unit 105 or the PC 120 which is an external device, and temperature / humidity data from the thermometer 108 and the hygrometer 109 (step S2).

  The CPU 101 calculates the amount of water k required per second based on the process speed data acquired in step 2 and the size of the paper S using Equation 1, and based on this water amount k, the ultrasonic vibration of the water vapor generating means 61 is calculated. The output of the child 66 is changed (step S3). In addition, it is preferable that the water vapor | steam generation means 61 always drives the ultrasonic transducer | vibrator 66, in order to generate water vapor | steam rapidly.

  Further, the CPU 101 drives the air blowing means 63 and calculates the air volume R at which the duct 62 does not condense based on the temperature / humidity data acquired in step S2 and the moisture amount k required for 1 second calculated in step 3 using the formula 2. Based on the calculated air volume R, the rotational speed of the air blowing means 63 is set (step S4). As a result, the water vapor is conveyed to the photoreceptor 41 through the duct 62, and moisture is supplied to the toner before being transferred to the intermediate transfer belt 50.

  Next, the CPU 101 determines whether or not the printing operation has been completed (step S5). If the printing operation is not completed in the determination process in step S5, the air blowing means 63 is driven to continue the printing operation. When the printing operation is finished, the CPU 101 stops the blowing unit 63 and stops spraying moisture on the photoconductor 41 (step S6). After this process is completed, a series of print processes are completed.

3. Comparative Experiment between Image Forming Apparatus of This Example and Conventional Example Next, a comparative experiment between the image forming apparatus 1 of this example and the conventional image forming apparatus will be described with reference to Table 1.

  In this comparative experiment, in the image forming apparatus 1 of this example having the water supply unit 60 and the conventional image forming apparatus 200 without the water supply unit 60, the average height of the toner images of the line image having a line width of 500 (μm). The dust state of the toner was compared by changing the size. The average height of the toner image formed on the photoreceptor 41 was 15 (μm), 20 (μm), and 25 (μm). The process speed v is set to 300 (mm / sec) for both the present example and the conventional example. The experimental environment was a temperature of 20 ° C. and a relative humidity of 50%. Further, a toner having a charge Q per unit weight of 50 (μ / Cg) is used. In the evaluation of the experiment, the line image printed on the paper was magnified with a microscope and visually evaluated.

  The temperature of the apparatus detected by the thermometer 108 and the hygrometer 109 of the image forming apparatus 1 of this example is 25 ° C., and the relative humidity is 50%. Therefore, the water supply speed k generated by the water vapor generating means 61 according to the image forming apparatus 1 of this example is 0.0628 (g / sec), and the air volume R of the air blowing means 63 is 6.0 (l / sec). )

  The comparison results are shown in Table 1.

  Table 1 shows an evaluation of toner scattering during transfer by the image forming apparatus 1 of this example and the image forming apparatus 200 of the conventional example. As shown in Table 1, in the conventional image forming apparatus 200 that does not supply water to the toner, when the height of the toner image is low (15 μm), it was desired to see the toner scattered next to the transfer. When the thickness was 20 (μm), toner scattering became conspicuous. Further, it has been found that when the height of the toner image is 25 (μm), toner scattering during transfer cannot be suppressed.

  On the other hand, according to the image forming apparatus 1 of the present example, it has been found that even when the height of the toner image is as high as 25 (μm), toner scattering during transfer can be suppressed. This is because by supplying moisture to the toner image before transfer, the liquid bridging force between the toners increases, and toners having the same polarity can be prevented from repelling, and even if they contact the intermediate transfer belt 50, the toners It can be inferred that the image could be prevented from collapsing.

  The embodiment of the image forming apparatus and the image forming method has been described above including the effects thereof. However, the image forming apparatus and the image forming method of the present invention are not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention described in the claims. It is.

  For example, in the above-described embodiment, the example in which the image forming unit 40 is provided with four image forming units 40Y, 40M, 40C, and 40K to form a color image has been described. However, only one image forming unit is provided. You may apply to the image forming apparatus which forms a monochromatic image.

  Further, an example has been described in which an intermediate transfer belt is provided as a transfer material for transferring a toner image formed on a photosensitive member, and an image is secondarily transferred from the intermediate transfer belt to a sheet. The object of the present invention can be achieved even if the is transferred.

  Further, the duct 62 is further branched to extend the discharge port 62a on the upstream side of the secondary transfer unit 70 in the intermediate transfer belt 50, and on the intermediate transfer belt 50 before being transferred to the paper S by the secondary transfer unit 70. Water may be supplied to the formed toner image.

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 10 ... Document conveyance part, 11 ... Document feeding stand, 12 ... Roller, 13 ... Document stand, 20 ... Paper storage part, 21 ... Paper feeding part, 23 ... Conveyance part, 30 ... Image reading part 40 ... Image forming unit, 40Y, 40M, 40C, 40K ... Image forming unit, 41 ... Photoconductor, 42 ... Charging unit, 43 ... Exposure unit, 44 ... Developing unit, 45 ... Cleaning unit, 50 ... Intermediate transfer belt ( (Transfer material), 51 ... primary transfer unit, 60 ... moisture supply unit, 61 ... water vapor generating means, 62 ... duct, 62a ... discharge port, 63 ... air blowing means, 65 ... tank, 66 ... ultrasonic transducer, 67 ... Drive circuit 70 secondary transfer unit 80 fixing unit 101 CPU (control unit) 108 thermometer (detection unit) 109 hygrometer (detection unit) 120 PC (external device) G …original Paper, S ... paper, W ... water

Claims (11)

A photoreceptor on which an electrostatic latent image is formed;
A developing unit for attaching toner to the electrostatic latent image of the photoreceptor;
A transfer portion for transferring the toner adhered to the photosensitive member to a transfer material;
A moisture supply unit that supplies moisture to the toner adhered to the photoconductor by the developing unit before being transferred to the transfer material;
An image forming apparatus comprising: The moisture supply unit
Water vapor generating means for generating water vapor;
A duct through which the water vapor passes;
A blowing means for sending the steam and wind into the duct,
The image forming apparatus according to claim 1, wherein a discharge port for discharging the water vapor in the duct is provided between the developing unit and the transfer unit and facing the outer peripheral surface of the photoconductor. The image forming apparatus according to claim 2, further comprising a control unit configured to control an output of the water vapor generating unit according to a process speed for forming an image. A detecting means for detecting the state of the photoreceptor in the duct and / or the water vapor is provided;
The image forming apparatus according to claim 3, wherein the control unit controls an output of the blowing unit based on the process speed and a detection result detected by the detection unit. 5. The image according to claim 4, wherein the control unit controls the output of the water vapor generation unit based on the process speed, the state of the photoconductor detected by the detection unit, and the size of a sheet on which an image is formed. Forming equipment. The image forming apparatus according to claim 4, wherein the detection unit is a thermometer and a hygrometer. The image according to any one of claims 4 to 5, wherein the control unit estimates a saturated water vapor amount in the duct and the photoconductor to which the water vapor is supplied from the detection result, and controls an output of the air blowing unit. Forming equipment. The water vapor generating means includes
A tank for storing water;
The image forming apparatus according to claim 2, further comprising an ultrasonic vibrator provided in the tank that vibrates ultrasonically. Forming an electrostatic latent image on the photoreceptor;
Attaching toner to the electrostatic latent image formed on the photoreceptor;
Supplying water from a water supply unit to the toner attached to the photoconductor before transferring the toner to a transfer material;
An image forming method comprising: The step of supplying moisture includes
Capturing process speed data from an operation display unit of the image forming apparatus or an external device;
Capturing temperature data and humidity data from a thermometer and a hygrometer provided at a location where moisture is supplied to the surface of the photoreceptor;
Controlling the output of the moisture supply unit based on the process speed, the temperature data, the humidity data and the size of the paper on which the image is formed;
Supplying moisture to the toner before it is transferred to the transfer material by sending moisture to the photoconductor based on the output of the moisture supply unit;
The image forming method according to claim 9. The step of controlling the output of the moisture supply comprises
Calculating the amount of water required for one second to be supplied to the photoconductor based on the process speed data and the size of the paper;
Changing the output of the ultrasonic vibrator of the water vapor generating means in the water supply unit based on the calculated amount of water required for 1 second;
Calculating the amount of water required for the calculated one second, the amount of air that the photoconductor does not condense based on the temperature data and the humidity data;
Setting the rotational speed of the blowing means in the moisture supply unit based on the calculated air volume;
The image forming method according to claim 10.

Images