JP5049559B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a printer, a facsimile machine, and a copying machine.

  In recent color image forming apparatuses, in order to increase the printing speed, a so-called tandem configuration is increasingly employed. In the tandem system, a plurality of combinations of a latent image carrier such as a photoconductor and a developing device as a developing unit for developing the latent image carried on the surface of the photoconductor are arranged and different colors developed on the photoconductor. Are transferred onto the intermediate transfer belt or paper in a superimposed manner. Then, a multicolor image such as a full-color image is formed by this superposition transfer. In a tandem image forming apparatus in which a combination of a latent image carrier and a developing device is arranged in the horizontal direction, if the developing device as a developing unit is long in the horizontal direction, a considerable space must be secured in the horizontal direction. . And thereby, an apparatus will enlarge in a horizontal direction.

  As a developing device, a chamber in which a storage chamber for storing a developer is elongated vertically from a position where a supply roller as a developer supply member for supplying the developer to a development roller as a development carrier is vertically extended is known. (For example, Patent Document 1). In the developing device having such a configuration, the developer is supplied to the supply roller by the weight of the developer in the accommodation chamber. In such a configuration, since the entire developing device has a vertically long shape that takes a space in the vertical direction rather than the horizontal direction on the cross section in the developing roller axial direction, the expansion of the space in the horizontal direction in the above-described image forming apparatus can be suppressed. .

Some recent image forming apparatuses have a normal image forming mode in which an image is formed at a normal image forming speed and a low speed image forming mode in which an image is formed with a reduced image forming speed. Under the following conditions, the control unit of the apparatus main body sets the low-speed image forming mode. For example, in an image forming apparatus provided with a fixing device as a fixing means for applying pressure and heating to fix an image formed on a latent image carrier, it is necessary to fix a toner image such as a cardboard or an OHP sheet. The low-speed image forming mode is set when the recording material has a larger amount of heat than plain paper. As a result, the amount of heat given from the fixing device to the recording material per unit area increases, and an image can be fixed well even on a thick paper sheet or an OHP sheet.
Further, when it is desired to obtain a high-quality image by reducing the pixel density by the laser optical device, the low-speed image forming mode is set and executed.

  In such an image forming apparatus, the latent image carrier and the developing roller and the supply roller of the developing device are driven by a driving motor as a common driving source.

JP-A-8-87167

  In a developing device that extends vertically in the vertical direction from the position where the supply roller is disposed, a large amount of developer accumulates on the supply roller. Then, when the rotation of the supply roller or the like is stopped when the developer in the storage chamber stops, the toner on the supply roller is tightened by the pressure due to the weight of the toner. Further, the pressure due to the weight of the toner hinders the circulation of the toner on the supply roller, and the toner is liable to stay.

In the normal image forming mode, the toner on the supply roller can be overcome and circulated and stirred in the storage chamber by the rotation of the supply roller by the rotation of the supply roller. In addition, toner retention can be suppressed.
On the other hand, in the low-speed image forming mode, the supply roller uses the same drive motor as the photoconductor and the developing roller, so the rotation speed of the supply roller is also slow. As a result, the effect of circulating and stirring the toner on the supply roller due to the rotation of the supply roller is reduced, and the effect of releasing the toner that has been tightened by its own weight when the apparatus is stopped is reduced. Further, since the effect of circulating the toner on the supply roller due to the rotation of the supply roller is reduced, the toner stays in a certain area in the storage chamber. Then, the developer conveyed by the rotation of the supply roller successively flows into the area where the stay has occurred, and the staying toner is pushed in. As a result, the staying toner aggregates. In this way, there is a problem that the toner aggregated during image formation at low speed presses against the supply roller to increase the torque and drive noise is generated. There are also problems that cause uneven image density and that the supply roller is significantly worn and damaged.

  These problems are likely to occur in recent years when toners are often used which contain wax in the particles for the purpose of realizing oilless fixing and low-temperature fixing. This is because such a toner is relatively soft and has a relatively large adhesion force between particles, and therefore easily forms an aggregate.

  In order to solve such a problem, it is conceivable to provide a separate drive motor for driving the supply roller so that the rotation speed of the supply roller is not lowered even when the low-speed image mode is executed. However, in this case, a drive motor dedicated to the supply roller is provided, leading to an increase in the cost of the apparatus.

  The present invention has been made in view of the above problems, and an object of the present invention is to suppress an increase in the cost of the apparatus and to suppress toner aggregation during image formation at the second image formation speed. An image forming apparatus is provided.

In order to achieve the above object, the invention of claim 1 includes a latent image carrier, and a developer carrier that develops the latent image carried on the latent image carrier by the developer carried on the surface of the latent image carrier. A first storage chamber for storing a developer to be supplied to the developer carrying member, and a developer carried on its peripheral surface in the first containing chamber is supplied to the developer carrying member with rotation. A developer supply member, a second storage chamber disposed above the first storage chamber and storing a developer for replenishing the first storage chamber, and a developer in the second storage chamber. Transferring the toner image formed on the latent image carrier onto the recording material, and developing means having a supply port provided between the chambers for dropping into the developer supply member in one storage chamber, or A transfer means for transferring the toner image on the intermediate transfer member to a recording material after transferring the toner image to the intermediate transfer member; A first image forming mode for forming an image at a first image forming speed, or a first image forming speed in an image forming apparatus comprising: a fixing unit that fixes the toner image transferred onto the recording material by heat; The image forming mode setting means for setting the second image forming mode for forming an image at a slower second image forming speed, and the latent image carrier, the developer carrier, and the developer supply member are driven in common. A driving means for rotationally driving the light source, and a control means for controlling the driving of the driving source. The control means performs the setting after the second image forming mode is set by the image forming mode setting means. at a predetermined timing until it is released, a predetermined time fast comb than the driving speed at which an image is formed at a driving speed of the driving source and the second image forming mode, and the solution to drive the driving source control The Was started, construed after the control end, it returns the driving speed of the driving source to the driving speed at which the image formed by the second image forming mode, is characterized in that an image is formed.
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the control unit starts the disassembling control at a timing when the continuous driving time of the second image forming speed exceeds a predetermined time. It is what.
According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the control unit starts the cracking control at a timing immediately after the second image forming mode is set. is there.
According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect, immediately after the second image forming mode is set when the first image forming mode is the second image forming mode after the apparatus is turned on. in timing, the amount of time the solution was controlled is started at the timing immediately after the normal second image forming mode setting when, is characterized in that longer than during the time of the solution to control the start .
According to a fifth aspect of the present invention, in the image forming apparatus according to the third or fourth aspect of the present invention, the image forming apparatus further comprises a pause time detecting means for detecting the pause time of the apparatus, and the control means exceeds the pause time of the apparatus. and then, between the second image forming mode set when the solution is controlled is started at the timing immediately after the time the second image forming mode is set, is started at the timing immediately after the second image forming mode set at the time of normal it is characterized in that longer than during the time of the solution to control that.
According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the third to fifth aspects, a temperature / humidity detecting unit that detects a temperature / humidity of the developing unit is provided, and the control unit sets a second image forming mode. wherein at a timing immediately after the second image forming mode set at the time temperature and humidity values detected by the temperature and humidity detecting means is below a predetermined value, the amount of time the solution was controlled is started, the second image forming mode in normal time is characterized in that longer than during the time of the the solution was controlled started at timing immediately after setting.
According to a seventh aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects, the image forming apparatus further comprises a temperature / humidity detecting means for detecting the temperature / humidity of the developing means, and the image forming mode setting means When the temperature / humidity value is equal to or lower than a predetermined value, the first image forming mode is set.
According to an eighth aspect of the present invention, in the image forming apparatus according to any one of the first to seventh aspects, the control means starts the tear-off control at a timing immediately before the second image forming mode is released. It is a feature.
According to a ninth aspect of the present invention, in the image forming apparatus according to any one of the first to eighth aspects of the present invention, the image forming apparatus further comprises torque detecting means for detecting the torque of the developer supply member, and the control means is detected by the torque detecting means. The control is started at a timing when the torque value exceeds a predetermined value.
According to a tenth aspect of the present invention, in the image forming apparatus according to any one of the first to ninth aspects, the developing means is configured to be detachable from the apparatus main body, and whether or not the developing means is new. A new article detecting means for detecting is provided, and the control means performs the control when the new article detecting means detects that the developing means attached to the apparatus is new.
According to an eleventh aspect of the present invention, in the image forming apparatus according to any one of the first to tenth aspects, the image forming mode setting means switches to the second image forming mode when the heat capacity of the recording material for forming the image is equal to or greater than a predetermined value. It is characterized by setting.
According to a twelfth aspect of the present invention, in the image forming apparatus according to any one of the first to eleventh aspects, the image forming apparatus further includes a temperature detecting unit that detects a temperature of the fixing unit, and the image forming mode setting unit has a temperature of the fixing unit. When the value is equal to or smaller than the predetermined value, the second image forming mode is set.
The invention according to claim 13 is the image forming apparatus according to any one of claims 1 to 12, wherein when the image is formed in the second image forming mode, the developer supply member is moved from the developer carrier to the developer. It is characterized by applying a bias in the direction of recovering.
The invention according to claim 14 is characterized in that, in the image forming apparatus according to any one of claims 1 to 13, non-magnetic one-component toner containing a wax component is used as the developer.

According to the first to twelfth aspects of the present invention, the latent image carrier, the developer carrier and the developer supply member are driven by a common drive source, so that each member is driven by a separate drive source. Thus, the cost increase of the apparatus can be suppressed.
Also, at a predetermined timing during the setting of the second image forming mode, the disengagement control for driving the driving source for a predetermined time at a driving speed higher than the driving speed when performing image formation in the second image forming mode is started. Thus, the following effects can be obtained. That is, by performing the release control, during the release control, the rotation speed of the developer supply member driven by the drive source is faster than the rotation speed when image formation is performed at the second image formation speed. Thus, by increasing the rotation of the developer supply member, the force for circulating and stirring the developer on the developer supply member increases. As a result, the toner in the first storage chamber can be removed, and the toner can be prevented from aggregating during image formation at the second image formation speed. As a result, it is possible to suppress the torque increase of the developer supply member, density unevenness, and breakage of the developer supply member.

Hereinafter, as an image forming apparatus to which the present invention is applied, an embodiment of an electrophotographic printer (hereinafter simply referred to as a printer) will be described.
First, the basic configuration of the printer will be described. FIG. 1 is a schematic configuration diagram showing the printer. In this figure, the printer includes four process units 1Y, M, C, and K for forming toner images of yellow, magenta, cyan, and black (hereinafter referred to as Y, M, C, and K). Yes. These use different colors of Y, M, C, and K toners as the developer, but otherwise have the same configuration and are replaced when the lifetime is reached. Taking a process unit 1K for forming a K toner image as an example, as shown in FIG. 2, a drum-shaped photosensitive member 2K as a latent image carrier, a drum cleaning device 3K, a charge eliminating device (not shown), and a charging roller 4K. And a developing device 5K. The process unit 1K is detachable from the printer main body, so that consumable parts can be replaced at a time.

  The photosensitive member 2K is rotationally driven at a linear speed of 150 [mm / sec] in the clockwise direction in the drawing by a driving means described later. A high voltage is applied to the charging roller 4K by a high voltage power supply circuit (not shown). At the facing portion between the rotating photoconductor 2K and the charging roller 4K, discharge is performed from the charging roller 4K toward the photoconductor 2K. By this discharge, the surface of the photoreceptor 2K is uniformly charged to −500 [V]. Then, it is exposed and scanned by the light beam L to carry an electrostatic latent image for K.

  The electrostatic latent image for K is developed into a Y toner image by a developing device 5K using K toner (not shown). Then, intermediate transfer is performed on an intermediate transfer belt 16 described later. The drum cleaning device 3K removes transfer residual toner adhering to the surface of the photoreceptor 2K after the intermediate transfer process by sliding the cleaning brush and the cleaning blade on the surface of the photoreceptor 2K.

  The static eliminator neutralizes residual charges on the photoreceptor 2K after cleaning. By this charge removal, the surface of the photoreceptor 2K is initialized and prepared for the next image formation. Similarly, in the process units (1Y, M, C) of other colors, (Y, M, C) toner images are formed on the photoconductors (2Y, M, C), and on the intermediate transfer belt 16 described later. Intermediate transfer.

  The developing device 5K includes a vertically long hopper 6K that stores K toner (not shown), and a supply unit 7K disposed below the hopper 6K. The hopper portion 6K as the second storage chamber contains toner for replenishment in the agitator 8K that is rotationally driven by a driving means (not shown) and the supply portion 7K as the first storage chamber.

  The hopper portion 6K and the supply portion 7K disposed below the hopper portion 6K communicate with each other through the communication port 9K. The toner stirred by the agitator 8K in the hopper unit 6 is dropped into the supply unit 7K through the communication port 9K while being mixed with air to improve fluidity. As a result, the toner is replenished from the hopper 6K into the supply unit 7K.

  The supply unit 7K includes a supply roller 10K as a developer supply body, a developer guide member 14K, and toner. The toner dropped into the supply unit 7K from the hopper unit 6K is agitated (mixed) with the toner in the hopper unit 6K by the developer guide member 14K and is deposited on the supply roller 10K. The supply roller 10K is rotationally driven in a counterclockwise direction in the figure by a driving unit (not shown). The shortest distance between the developer guide member 14K and the supply roller 10K is preferably greater than 0 mm and less than 5 mm.

  Below the supply roller 10K, a developing roller 11K as a developer carrying member is disposed. The developing roller 11K is rotationally driven in a counterclockwise direction in the figure by a driving unit (not shown) while being in contact with the supply roller 10K and the photoreceptor 2K.

  A developing bias described later is applied to the developing roller 11K by a power supply circuit (not shown). On the other hand, a supply bias is applied to the supply roller 10K by a power supply circuit (not shown). The relationship between the development bias and the supply bias is a relationship that forms an electric field that can electrostatically move the negatively charged toner from the supply roller 10K side toward the development roller 11K side. However, the direction of the electric field is not limited to this, and may be reversed depending on the type of toner, or may be the zero direction in which the toner is not electrostatically moved between the rollers.

  The toner deposited on the supply roller 10K is carried on the surface of the supply roller 10K. Then, as the supply roller 10K rotates, it is conveyed to the contact portion between the supply roller 10K and the development roller 11K, and is transferred to the surface of the development roller 11K due to the influence of the electric field and the pressure at the contact portion. . The toner carried on the surface of the developing roller 11K by this shift moves as the developing roller 11K rotates, and passes through the contact portion between the developing roller 11K and the thinning blade 12K.

  A charging facilitating bias is applied to the thinning blade 12K by a power supply circuit (not shown). The relationship between the charging facilitating bias and the developing bias described above is a relationship that forms an electric field capable of electrostatically moving the negatively charged toner from the blade side toward the developing roller 11K side. The toner that has entered the contact portion between the developing roller 11K and the thinning blade 12K is rubbed against the thinning blade 12K as the roller rotates while being pressed against the developing roller 11K by this electric field. , Frictional charging is promoted. At the same time, the layer thickness on the developing roller 11K is regulated.

  The toner that has passed through the contact portion between the developing roller 11K and the thinning blade 12K is conveyed to the developing nip where the developing roller 11K and the photoreceptor 2K are in contact with the rotation of the developing roller 11K. The potential of the electrostatic latent image of the photosensitive member 2K, the potential of the background portion of the photosensitive member 2K (uniform charging potential), and the developing bias have the following relationship. That is, the toner existing between the electrostatic latent image and the developing roller 11K in the developing nip is electrostatically moved from the developing roller 11K toward the electrostatic latent image, while the background portion and the developing roller 11K are moved. This is a relationship for forming an electric field capable of electrostatically moving the toner existing between the background portion side and the developing roller 11K side. Due to such a relationship, the toner on the surface of the developing roller 11K is preferentially transferred to the electrostatic latent image on the photoreceptor 2K in the developing nip. By this dislocation, the electrostatic latent image is developed into a K toner image.

The surface of the supply roller 10K has a hole (cell) structure and is made of a foam material whose electric resistance value is adjusted to 10 ³ to 10 ¹⁴ [Ω]. By taking the toner into the hole, Increase toner transfer efficiency. Further, the holes also exhibit a function of suppressing toner deterioration due to pressure concentration at the contact portion with the developing roller 11K.

  On the surface of the developing roller 11K, a surface layer made of an elastic rubber that exhibits frictional charging characteristics having a polarity opposite to that of the toner is formed. This surface layer has a JIS-A hardness adjusted to 50 [°] or less and a surface roughness Ra adjusted to 0.2 to 2.0 [μm]. Due to the surface layer having such characteristics, a toner image having a uniform thickness is formed on the surface of the developing roller 11K.

  The thinning blade 12K is a thin blade made of a metal such as SUS304CSP, SUS301CSP, or phosphor bronze, and is pressed toward the developing roller 11K with a pressing force of 10 to 100 [N / m].

The casing of the supply unit 7K cantilever-supports the sealing film 13K, and the free end side of the sealing film 13K is in contact with the developing roller 11K. The sealing film 13K and the above-described thinning blade 12K partition the space in which the developing roller 11K is accommodated from the supply unit 7K, thereby preventing toner leakage from the supply unit 7K.
Further, a temperature / humidity sensor 110 serving as a temperature / humidity detecting means for detecting the temperature / humidity in the developing device is provided inside the developing device 5K.

  The toner in the developing device 5K is a non-magnetic toner containing wax and has a volume average particle diameter of 6 to 10 μm. A toner having a maximum tensile force of less than 0.55 N was used. The maximum tensile force was measured with an Akbot manufactured by Hosokawa Micron Corporation. A toner having a maximum tensile force of 0.55 N or more is not desirable because the toner is particularly likely to aggregate and toner clogging is likely to occur below the supply roller 11K.

  An ID chip 111 is attached to the process unit 1K. The ID chip 111 stores identification information for identifying the process unit 1K, information necessary for controlling the components of the process unit 1K, and the like. . A communication unit 112 is provided on the apparatus main body side, and communicates with the ID chip 111 to write information to the ID chip 111 and read information from the ID chip 111. When the process unit 1K is attached to the apparatus main body, the control unit 200 of the apparatus main body communicates with the ID chip 111 using the communication unit 112, and the identification information stored in the ID chip 111 is previously communicated. It is checked whether or not it matches the identification information obtained. If they do not match, the control unit 200 determines that a new process unit 1K has been attached, and performs processing to be performed when the process unit 1K is replaced, which will be described later. That is, in the present embodiment, the communication unit 112, the ID chip 111, and the control unit 200 function as a new article detection unit.

  Although the process unit for K has been described with reference to FIG. 2, the process units 1Y, M, and C for Y, M, and C also perform Y, M, and C on the surfaces of the photoreceptors 2Y, M, and C by a similar process. A C toner image is formed.

  In FIG. 1 described above, an optical writing unit 70 is disposed above the process units 1Y, M, C, and K in the vertical direction. The optical writing unit 70, which is a latent image writing means, uses a light beam L emitted from a laser diode or LED diode on the basis of image information, and photoreceptors 2Y, M, C, K in the process units 1Y, M, C, K. Is optically scanned. By this optical scanning, electrostatic latent images for Y, M, C, and K are formed on the photoreceptors 2Y, M, C, and K. The optical writing unit 70 is a photosensitive member that passes through a plurality of optical lenses and mirrors while polarizing a light beam (L) emitted from a light source in a main scanning direction by a polygon mirror that is rotationally driven by a polygon motor (not shown). Is irradiated.

  Below the process units 1Y, M, C, and K in the vertical direction, a transfer unit 15 serving as transfer means is disposed. The transfer unit 15 serving as transfer means includes an intermediate transfer belt 16, a driving roller 17, a driven roller 18, four primary transfer rollers 19Y, 19M, 19C, 19K, a secondary transfer roller 20, a belt cleaning device 21, and a cleaning backup roller 22. Etc.

  The intermediate transfer belt 16 is stretched by a driving roller 17, a driven roller 18, a cleaning backup roller 22 and four primary transfer rollers 19Y, 19M, 19C, and 19K disposed inside the loop. Then, it is moved endlessly in the same direction by the rotational force of the driving roller 17 that is driven to rotate counterclockwise in the figure by a driving means (not shown).

  The four primary transfer rollers 19Y, 19M, 19C, and 19K sandwich the intermediate transfer belt 16 that is moved endlessly in this manner between the photoreceptors 2Y, 2M, 2C, and 2K. By this sandwiching, primary transfer nips for Y, M, C, and K where the front surface of the intermediate transfer belt 16 and the photoreceptors 2Y, M, C, and K abut are formed.

  A primary transfer bias is applied to each of the primary transfer rollers 19Y, 19M, 19C, and 19K by a transfer bias power source (not shown), whereby the electrostatic latent images on the photoreceptors 2Y, 2M, 2C, and 2K, A transfer electric field is formed between the primary transfer rollers 19Y, 19M, 19C, and 19K. Instead of the primary transfer rollers 19Y, 19M, 19C, and 19K, a transfer charger, a transfer brush, or the like may be employed.

  When Y toner formed on the surface of the photoreceptor 2Y of the Y process unit 1Y enters the above-described primary transfer nip for Y as the photoreceptor 2Y rotates, the photosensitive member 2Y is exposed to light by the action of the transfer electric field and nip pressure. Primary transfer is performed on the intermediate transfer belt 16 from the body 2Y. The intermediate transfer belt 16 on which the Y toner image is primarily transferred in this way passes through the primary transfer nips for M, C, and K along with the endless movement thereof, and the photoreceptors 2M, C, and K. The upper M, C, and K toner images are sequentially superimposed on the Y toner image and primarily transferred. A four-color toner image is formed on the intermediate transfer belt 16 by the primary transfer of superposition.

  While the secondary transfer roller 20 of the transfer unit 15 is disposed outside the loop of the intermediate transfer belt 16, the intermediate transfer belt 16 is sandwiched between the secondary transfer roller 20 and the driven roller 18 inside the loop. By this sandwiching, a secondary transfer nip where the front surface of the intermediate transfer belt 16 and the secondary transfer roller 20 abut is formed. A secondary transfer bias is applied to the secondary transfer roller 20 by a transfer bias power source (not shown). By this application, a secondary transfer electric field is formed between the secondary transfer roller 20 and the driven roller connected to the ground.

  Below the transfer unit 15, a paper feed cassette 30 that stores a plurality of recording sheets P in a bundle of sheets is slidably attached to the printer housing. In the paper feed cassette 30, a paper feed roller 30a is brought into contact with the top recording paper P of the paper bundle, and the recording paper is rotated by rotating it in a counterclockwise direction in the drawing at a predetermined timing. P is sent out toward the paper feed path 31.

  A registration roller pair 32 is disposed near the end of the paper feed path 31. The registration roller pair 32 stops the rotation of both rollers as soon as the recording paper P delivered from the paper feed cassette 30 is sandwiched between the rollers. Then, rotation driving is resumed at a timing at which the sandwiched recording paper P can be synchronized with the four-color toner image on the intermediate transfer belt 16 in the above-described secondary transfer nip, and the recording paper P is directed to the secondary transfer nip. Send it out.

  The four-color toner image on the intermediate transfer belt 16 brought into close contact with the recording paper P at the secondary transfer nip is secondarily transferred onto the recording paper P under the influence of the secondary transfer electric field and the nip pressure. Combined with the white color of P, a full color toner image is obtained. The recording paper P having the full-color toner image formed on the surface in this manner is separated from the secondary transfer roller 20 and the intermediate transfer belt 16 by the curvature when passing through the secondary transfer nip. Then, the toner is fed into a fixing device 34 described later via a post-transfer conveyance path 33.

  The transfer residual toner that has not been transferred to the recording paper P adheres to the intermediate transfer belt 16 after passing through the secondary transfer nip. This is cleaned from the belt surface by a belt cleaning device 21 in contact with the front surface of the intermediate transfer belt 16. The cleaning backup roller 22 disposed inside the loop of the intermediate transfer belt 16 backs up the cleaning of the belt by the belt cleaning device 21 from the inside of the loop.

The fixing device 34 serving as fixing means forms a fixing nip with a fixing roller 34a including a heat source such as a halogen lamp (not shown) and a pressure roller 34b that rotates while contacting the fixing roller 34a with a predetermined pressure. The recording paper P fed into the fixing device 34 is sandwiched between the fixing nips such that the unfixed toner image carrying surface is brought into close contact with the fixing roller 34a. Then, the toner in the toner image is softened by the influence of heating and pressurization, and the full color image is fixed.
Further, a thermistor 34c serving as temperature detecting means is disposed at a position facing the fixing roller 34a to detect the surface temperature of the fixing roller 34a.

  The recording paper P discharged from the fixing device 34 passes through the post-fixing conveyance path 35 and then reaches the branch point between the paper discharge path 36 and the pre-reversal conveyance path 41. On the side of the post-fixing conveyance path 35, a switching claw 42 that is rotationally driven around a rotation shaft 42a is disposed. By the rotation, the vicinity of the end of the post-fixing conveyance path 35 is closed. Or open it. At the timing when the recording paper P is sent out from the fixing device 34, the switching claw 42 stops at the rotational position indicated by the solid line in the drawing, and the vicinity of the end of the post-fixing conveyance path 35 is opened. Therefore, the recording paper P enters the paper discharge path 36 from the conveyance path 35 after fixing, and is sandwiched between the rollers of the paper discharge roller pair 37.

  When the single-sided print mode is set by an input operation to an operation unit including a numeric keypad (not shown) or a control signal sent from a personal computer (not shown), the recording sandwiched between the paper discharge roller pair 37 is performed. The paper P is discharged out of the machine as it is. Then, it is stacked on the stack portion that is the upper surface of the upper cover 50 of the housing.

  On the other hand, when the duplex printing mode is set, the trailing edge of the recording paper P conveyed through the paper discharge path 36 while the front end is sandwiched between the paper discharge roller pair 37 passes through the post-fixing conveyance path 35. The switching claw 42 is rotated to the position of the one-dot chain line in the drawing, and the vicinity of the end of the post-fixing conveyance path 35 is closed. At substantially the same time, the paper discharge roller pair 37 starts to rotate in the reverse direction. Then, the recording paper P is conveyed while the rear end side is directed to the top, and enters the pre-reversal conveyance path 41.

  FIG. 1 shows the printer from the front side. The front side in the direction orthogonal to the illustrated surface is the front surface of the printer, and the back side is the rear surface. In the drawing, the right side of the printer is the right side and the left side is the left side. The right end portion of the printer is a reversing unit 40 that can be opened and closed with respect to the housing body by rotating about a rotating shaft 40a. When the paper discharge roller pair 37 rotates in the reverse direction, the recording paper P enters the pre-reversal conveyance path 41 of the reversing unit 40 and is conveyed from the upper side to the lower side in the vertical direction. Then, after passing between the rollers of the pair of reverse conveying rollers 43, it enters the reverse conveying path 44 that is curved in a semicircular shape. Furthermore, while the upper and lower surfaces are reversed as the sheet is conveyed along the curved shape, the traveling direction from the upper side in the vertical direction to the lower side is also reversed, and conveyed from the lower side in the vertical direction toward the upper side. Is done. Thereafter, the toner enters the secondary transfer nip again through the above-described paper feed path 31. Then, after the full color image is collectively transferred to the other surface, the post-transfer conveyance path 33, the fixing device 34, the post-fixation conveyance path 35, the paper discharge path 36, and the paper discharge roller pair 37 are sequentially passed. And discharged outside the machine.

  The reversing unit 40 described above has an external cover 45 and a rocking body 46. Specifically, the external cover 45 of the reversing unit 40 is supported so as to rotate about a rotation shaft 40a provided in the housing of the printer main body. By this rotation, the outer cover 45 opens and closes with respect to the housing together with the swinging body 46 held therein. As shown by the dotted line in the figure, when the outer cover 45 is opened together with the swinging body 46 therein, the paper feed path 31 formed between the reversing unit 40 and the printer body side, the secondary transfer nip, and after the transfer. The conveyance path 33, the fixing nip, the post-fixing conveyance path 35, and the paper discharge path 36 are vertically divided into two and exposed to the outside. Thereby, jammed paper in the paper feed path 31, the secondary transfer nip, the post-transfer conveyance path 33, the fixing nip, the post-fixation conveyance path 35, and the paper discharge path 36 can be easily removed.

  The swing body 46 is supported by the external cover 45 so as to rotate about a swing shaft (not shown) provided in the external cover 45 in a state where the external cover 45 is opened. When the swinging body 46 is opened with respect to the external cover 45 by this rotation, the pre-reversal transport path 41 and the reverse transport path 44 are vertically divided into two and exposed to the outside. As a result, the jammed paper in the pre-reversal conveyance path 41 and the reversal conveyance path 44 can be easily removed.

  The upper cover 50 of the printer housing is supported so as to be rotatable about a rotation shaft 51 as indicated by an arrow in the drawing, and is rotated counterclockwise in the drawing to Opened. Then, the upper opening of the housing is greatly exposed to the outside. Thereby, the optical writing unit 71 is exposed.

FIG. 3 is a schematic configuration diagram showing a drive unit that is a drive unit of the process units 1K, Y, M, and C. Since the drive unit of each process unit has the same configuration, description will be given here without adding K, Y, M, and C color codes.
As shown in the figure, the drive gear 101a fixed to the shaft of the drive source motor 101, which is a drive source, meshes with the photoconductor gear 104 fixed to the photosensitive shaft. The photoconductor gear 104 meshes with a driven gear 102 attached to the shaft of the developing roller 11. A first gear 103 is fixed to the shaft of the developing roller 11 and meshes with a second gear 105 fixed to the shaft of the supply roller 10. When the drive motor 101 is driven, the driving force of the drive motor 101 is transmitted from the drive gear 101a through the photoconductor gear 104, and the photoconductor 2 rotates at a predetermined speed. The driving force of the driving motor 101 is transmitted from the photoconductor gear 104 to the driven gear 102, and the developing roller 11 rotates at a predetermined speed. Further, the driving force of the driving motor 101 transmitted to the driven gear 102 is transmitted from the first gear 103 to the second gear 105, and the supply roller 10 rotates at a predetermined speed. As described above, in this embodiment, the photosensitive member 2, the developing roller 11, and the supply roller 10 are rotationally driven by the single drive motor 101. In the drive motor 101, the drive speed and drive time of the drive motor 101 are controlled by a control signal from the control unit 200.
Further, the current value flowing through the drive motor 101 is measured by the ammeter 106, and the control unit 200 detects the torque of the supply roller 10 based on the value measured by the ammeter 106. That is, the control unit 200 and the ammeter 106 have a function as torque detection means.

FIG. 4 is a block diagram showing a part of the electric circuit of the printer. In the figure, the control unit 200 controls the entire apparatus, and various devices and sensors are connected. In the figure, only the devices and sensors related to the feature points of the printer are shown. Yes. The control unit 200 includes a CPU, a ROM, a RAM, and the like, and realizes the functions of each unit by executing a predetermined program on hardware.
The control unit 200 has a function as a control unit that controls driving of the drive motor 101. Further, the control unit 200 has a clock unit (not shown), and functions as a pause time detection unit that detects a pause time of the developing device by measuring the time after the drive motor 101 stops. have.
The operation display unit 107 includes a numeric keypad, a display, and the like (not shown). The operation display unit 107 inputs information about a recording sheet on which an image is formed, displays apparatus settings, and the like.

The printer also includes a first image forming mode for forming an image at a normal image forming speed (hereinafter referred to as a first image forming speed) and an image forming speed (hereinafter referred to as a second image forming speed) that is slower than the first image forming speed. A second image forming mode in which image formation is performed at a speed). The control unit 200 sets the first image forming mode in which image formation is performed at the first image forming speed or the second image forming mode in which image formation is performed at an image forming speed slower than the first image forming speed. It also has a function as setting means.
For example, when the recording paper on which the image is to be formed forms an image on a recording material having a large heat capacity, such as OHP, thick paper having a basis weight of 70 g or more, or a postcard, the control unit 200 sets the second image forming mode and sets the second image forming mode. Image formation is started at the image formation speed. Then, when the image formation is completed on the recording sheet having a large heat capacity for the requested number of sheets, the control unit 200 cancels the setting of the second image formation mode. The determination as to whether or not the recording paper on which the image is to be formed is a recording material having a large heat capacity is performed as follows, for example. In other words, the control unit 200 can detect the type of recording paper on which an image is formed by setting the type of recording paper on which the user forms an image on the operation display unit 107.

  Further, when the temperature detection result of the thermistor 34c, which is a temperature detecting means for detecting the temperature of the fixing device 34, is 170 ° C. or less, the control unit 200 sets the second image forming mode and performs image processing at the second image forming speed. Form. For example, when images are continuously formed on plain paper in the first image forming mode, the heat amount of the fixing roller 34a is gradually taken away by the plain paper, and the surface temperature of the fixing roller 34a falls below 170 ° C. In this case, the setting of the first image forming mode is canceled and the second image forming mode is set. Then, with respect to the remaining number of sheets, an image is formed on plain paper at a second image forming speed at which the image forming speed is slow. Thus, continuous printing can be continued without causing a fixing failure.

  Further, when the temperature in the optical writing unit 70 rises, the light emission amount of the LED decreases, resulting in image density reduction and density unevenness. Therefore, when the temperature of the optical writing unit 70 is detected and the temperature exceeds a predetermined value, the second image forming mode is set and image formation is performed at the second image forming speed. As a result, image density reduction and density unevenness can be suppressed.

  Further, when the apparatus main body is provided with a high quality mode and a normal quality mode, and the user sets the high quality mode, the control unit 200 forms an image in the second image forming mode.

  Further, when the second image forming mode is set, a recovery bias is applied to the supply roller 11 by a power supply circuit (not shown). The relationship between the developing bias and the supply bias is a relationship that forms an electric field capable of electrostatically moving the negatively charged toner from the developing roller 11 side toward the supply roller 10 side. In this way, the toner adhering to the developing roller is forcibly recovered to suppress the torque increase of the supply roller 11.

Next, features of the present embodiment will be described.
As shown in FIG. 1, the method of forming and superposing toner images by a plurality of process units 1Y, C, M, and K arranged on a straight line is called a tandem method. In a tandem printer, the overall size of the apparatus tends to increase in the process unit arrangement direction. Therefore, in this printer, a hopper portion that takes a particularly large space among the process units has a shape that extends long in a direction orthogonal to the unit arrangement direction, thereby suppressing the space expansion in the unit arrangement direction. However, in this case, it is necessary to adopt a configuration in which the toner in the hopper is dropped into the supply unit by its own weight. In such a configuration, the toner on the supply roller 10 tends to aggregate. When toner aggregates on the supply roller in this way, the torque of the supply roller increases, image density unevenness is deteriorated, and wear of the supply roller is caused. In particular, when a toner containing a wax that is relatively soft and has a relatively large adhesion between particles is used, aggregation is likely to occur, and these problems are likely to occur.

  In this embodiment, in the normal first image forming mode, the supply roller 10 is set to rotate at a rotation speed of 300 to 400 rpm, and the supply roller 10 is rotated by rotating at this rotation speed. The surrounding toner is circulated by the rotation of the supply roller 10. However, as shown in FIG. 3, since the common driving motor 101 is used for the photosensitive member 2, the developing roller 11, and the supply roller 10, the driving motor is used in the second image forming mode in which the image forming speed is reduced. The driving speed of 101 is reduced by about (1/2) to (2/3). For this reason, the rotation speed of the supply roller 10 is reduced to 150 to 250 rpm. Thus, when the supply roller 10 rotates at a low speed, the toner circulation effect due to the rotation of the supply roller 10 is reduced, and for example, the toner stays in the area A and the area B in FIG.

When the supply roller 10 rotates at 300 to 400 rpm, the toner around the supply roller is conveyed counterclockwise in the drawing of the supply roller 10 and is conveyed to the area A in FIG. It moves upward, is agitated by the developer guide member 14, and accumulates again on the supply roller 10. The toner in the supply unit is conveyed through such a circulation path. However, when the rotation of the supply roller 10 decreases, the force for conveying the toner around the supply roller by the rotation of the supply roller 10 is weakened. The toner transported to the area cannot move upward in the figure due to the pressure of the toner in the storage chamber and stays in the area A in the figure. Since the supply roller 10 continues to rotate, toner is successively conveyed to the portion A. As a result, the toner staying in the area A in the figure aggregates, and the pressure in the area A in the figure increases. As a result, the developing roller 11 and the supply roller 10 which are parts around the area A in the figure are significantly worn and eventually damaged. Further, the torque of the supply roller 10 is increased, and driving noise is generated. Further, the progress of toner deterioration in the supply unit 7 is accelerated.
Further, as a result of the rotation speed of the supply roller 10 being reduced and the force for conveying the toner of the supply roller 10 being weakened, the toner accumulated in the region B in the figure stays without being stirred by the rotation of the supply roller 10. As a result, the toner in the region B aggregates due to the weight of the toner, and the aggregated toner comes into pressure contact with the supply roller 10 to increase the torque of the supply roller 10.

FIG. 5 is a diagram showing the change over time in the torque of the supply roller 10 when the supply roller 10 is rotated at the number of rotations in the second image forming mode (low speed mode).
As shown in the figure, when the supply roller 10 was rotated for 10 minutes or more, the torque of the supply roller 10 suddenly increased and the supply roller 10 was damaged. This is because the toner aggregates in the region A in FIG. 2 and the like, and the aggregated toner grows gradually and presses the supply roller. The aggregated toner further grows by the rotation of the supply roller 10 and further increases the pressure of the supply roller 10. It is considered that the torque of the supply roller 10 has rapidly increased due to such a phenomenon.
FIG. 6 is a diagram showing the maximum torque of the supply roller 10 at each rotation speed when the supply roller 10 is continuously rotated at each rotation speed for 20 minutes. As shown in the figure, when the rotation speed of the supply roller 10 is 150 to 250 rpm in the second image forming mode (low speed mode), the maximum torque of the supply roller 10 is 0.02 [N · m] or more, but at 300 to 400 rpm, which is the rotation speed of the supply roller 10 in the normal first image forming mode, the maximum torque of the supply roller 10 is about 0.01 [N · m]. there were.

  5 and 6, the rotation ratio of the supply roller 10 in the second image forming mode is adjusted to 300 to 300 by adjusting the gear ratio between the second gear 105 and the first gear 103 of the drive unit shown in FIG. It is also conceivable to set the speed to 400 rpm. However, in this case, the number of rotations of the supply roller 10 in the normal first image forming mode increases too much, and the progress of toner deterioration is accelerated.

  Therefore, in this embodiment, at a predetermined timing during the setting of the second image forming mode, the driving motor 101 is rotated for a predetermined time at a first driving speed that is faster than when an image is formed in the second image forming mode. Control is started and the rotation speed of the supply roller 10 is increased by a predetermined time. Thereby, the toner around the supply roller 10 is released, and aggregation of the toner when the second image forming mode is executed can be suppressed. Below, it demonstrates concretely based on Examples 1-6.

[Example 1]
FIG. 7 is a sequence diagram of the first embodiment. As shown in the drawing, in the first embodiment, when the driving time at the image forming speed (second image forming speed) in the second image forming mode exceeds a predetermined time, the driving at the first driving speed for a predetermined time is performed. Then, control is started. As shown in FIG. 7, when the time during which driving is performed at the second image forming speed has elapsed for 300 seconds, the control unit 200 starts disassembly control for driving the driving motor 101 for 10 seconds at the first driving speed. In the first embodiment, the first drive speed is the drive speed of the drive motor 101 in the first image forming mode. Thus, the supply roller 10 is driven by driving the drive motor 101 at the drive speed in the first image forming mode for 10 seconds (the drive motor 101 is driven so that the rotation speed of the supply roller 10 is 300 to 400 rpm). The toner conveying force can be increased. Therefore, the toner staying in the area A and the area B in FIG. 2 can be circulated and stirred, and toner aggregation can be suppressed from occurring in the areas A and B in the figure. As a result, it is possible to suppress damage to components in the developing device and increase in the torque of the supply roller 10 in the second image forming mode.
In the first embodiment, if the driving time at the second image forming speed continues for 300 seconds, the driving motor 101 is driven at the first driving speed, but the present invention is not limited to this. As shown in FIG. 5 above, if the second image forming speed exceeds 10 minutes, the supply roller may be damaged. Therefore, the timing for starting the unlocking control is from the start of driving at the second image forming speed. It can be set as appropriate within a range of 10 minutes or less. In addition, the time for driving the drive motor 101 at the first drive speed may be appropriately set according to the timing at which the control is started. In the first embodiment, the first driving speed is set to the driving speed in the first image forming mode. However, the first driving speed is not limited to this, and the driving motor 101 is driven at the first driving speed at the timing when the control is started. What is necessary is just to set suitably according to time. Note that the control unit 200 determines the continuous driving time of the second image forming speed based on the number of printed sheets. That is, the time required to form an image on the recording paper P at the second image forming speed is stored in the storage means in advance, and the second image forming speed is continuously driven by multiplying the required number of prints by the required time. Time can be calculated.

[Example 2]
FIG. 8 is a sequence diagram of the second embodiment. In the second embodiment, immediately after the second image forming mode is set, the disengagement control for driving for a predetermined time at the first driving speed is performed. When the printing operation is completed, the drive motor 101 is stopped and the supply roller 10 in the developing device is stopped. Therefore, the toner in the supply unit 7 is in a tight state due to its own weight, and aggregation is likely to occur. . For this reason, immediately after the second image forming mode is set, the toner around the supply roller 10 can be released by performing the release control so that the toner around the supply roller 10 is circulated and stirred. As described above, since the toner in the supply unit is sufficiently solved, even if the toner conveying force due to the rotation of the supply roller is reduced, it can be circulated without staying, and image formation can be performed at the second image formation speed. It is possible to suppress toner retention in the toner. In addition, even when stagnation occurs, the generation time can be delayed, and aggregation of the retained toner during image formation at the second image formation speed can be suppressed.
In the second exemplary embodiment, the driving roller 101 is driven for 2 seconds at the first driving speed. However, the degree of tightening of the toner in the supply unit varies depending on the apparatus downtime. That is, when the pause time is short, the toner around the supply roller 10 can be released by driving the drive roller 101 at the first drive speed for 2 seconds. However, if the pause time is long, the first drive speed is 2 seconds. In some cases, the toner around the supply roller 10 cannot be sufficiently solved only by driving the drive roller 101.

FIG. 9 shows the maximum torque of the supply roller 10 when driven for 10 minutes at the driving speed of the second image forming speed after each pause time.
As shown in the figure, it can be seen that the maximum torque of the supply roller 10 increases from the point when the rest time exceeds 50 hours. From this result, for example, after 100 hours of rest, the toner around the supply roller 10 cannot be sufficiently unwound only by driving at the first drive speed for 2 seconds immediately after setting the second image forming mode. For this reason, the toner staying during image formation at the second image forming speed may be aggregated to cause problems such as torque increase of the supply roller.
Therefore, the control unit 200 measures the pause time of the apparatus and, when the second image forming mode is set, checks the measured time and checks whether the pause time exceeds 10 hours. If the pause time exceeds 10 hours, the control unit 200 sets the drive time of the first drive speed in the disassembly control that starts immediately after setting the second image forming mode to 10 seconds, and drives the drive more than usual. Try to increase. As a result, toner aggregation due to toner retention can be suppressed even if image formation is performed at the second image formation speed immediately after a state of rest for a long period of time.
In the above description, for the sake of safety, when the pause time exceeds 10 hours, the driving time of the first driving speed in the unlocking control that starts immediately after setting the second image forming mode is increased from the normal time. It is not limited to this. As shown in FIG. 9, the torque of the supply roller 10 is substantially the same up to 50 hours of resting time, so it may be set as appropriate within this range. The drive motor 101 is driven at the first drive speed for 10 seconds, but may be set as appropriate depending on the specifications of the apparatus and developer. However, by driving the drive motor 101 at the first drive speed for at least 10 seconds, the supply roller 10 can reliably remove the toner tightened by its own weight around the supply roller 10.

  In addition, since the pause time is not measured when the power is turned off, it is not known how long the device has been paused when the power is turned on. Therefore, even when the second image forming mode is set immediately after the power is turned on, the driving time at the first driving speed is set to 10 seconds, and the driving time is increased from the normal time. Accordingly, toner aggregation due to toner retention can be suppressed even if image formation is performed in the second image formation mode immediately after the power is turned on.

Further, the fluidity of the toner in the supply unit varies depending on the environment in the developing device. In a low-temperature and low-humidity environment, the fluidity of toner in the supply unit is significantly reduced. Therefore, even when the pause time is short, toner retention tends to occur when image formation is performed in the second image formation mode. In some cases, the staying toner aggregates and a sudden torque increase of the supply roller occurs.
FIG. 10 shows the maximum torque of the supply roller 10 when it is driven for 10 minutes at the driving speed in the second image forming mode under each environment. As shown in the figure, it can be seen that the maximum torque of the supply roller 10 is high in a low temperature and low humidity environment of 10 degrees / 15%.
Therefore, when the second image forming mode is executed, the control unit 200 acquires the detection result of the temperature / humidity sensor 110 provided in the developing device 5 as shown in FIG. If the detection result is 10 ° C./15% or less, the driving time at the first driving speed is set to 10 seconds, the toner around the supply roller 10 is sufficiently dissolved, and the second image formation is performed. Start. As a result, toner retention can be suppressed even when image formation is performed in the second image formation mode in a low temperature and low humidity environment. Further, even when toner stagnation occurs, the generation time can be delayed, and toner can be aggregated to suppress a rapid increase in torque of the supply roller 10.

[Example 3]
FIG. 10 is a sequence diagram of the third embodiment.
As shown in the figure, the third embodiment releases the setting of the second image forming mode after performing the disengagement control for driving the driving roller 101 for a predetermined time at the first driving speed. After the setting of the second image forming mode is canceled, the toner stays in the area A and the area B in FIG. 2, and the toner is clogged more than the other areas. Therefore, the toner in the area A and the area B is more likely to aggregate during the rest of the apparatus than in other areas.
Therefore, by driving the driving roller 101 for a predetermined time at the first driving speed and then canceling the setting of the second image forming mode, the toner staying in the area A and the area B in FIG. 2 can be released. Therefore, it is possible to suppress the presence of a toner-clogged area in the supply unit after the second image forming mode setting is canceled. In this printer, the toner staying in the areas A and B in FIG. 2 can be removed by driving at the first drive speed for 4 seconds. Of course, the driving time at the first driving speed is not limited to 4 seconds, but is appropriately set according to the specifications of the apparatus, the material of the toner, and the like.

[Example 4]
Next, Example 4 will be described.
In the fourth embodiment, the torque of the supply roller 10 is detected, and when the torque value exceeds a predetermined value, the disengagement control for driving the drive motor 101 for a predetermined time at the first drive speed is performed.
While the second image forming mode is set, the control unit 200 monitors the measured value of the ammeter of the drive motor 101 as shown in FIG. When the torque of the supply roller 10 increases, the value of the current flowing through the drive motor 101 increases. That is, the value of the current flowing through the drive motor 101 and the torque of the supply roller 10 are in a proportional relationship. Therefore, the torque of the supply roller 10 is predicted from the current value, and when the current value exceeds a predetermined value, the control unit 200 performs a disengagement control for driving for a predetermined time at the first drive speed, and performs a predetermined control in the supply unit 7. The toner staying in the area is circulated and stirred. Thereby, it is possible to suppress toner aggregation from occurring in a predetermined region of the supply unit 7. Therefore, it is possible to suppress damage to components in the developing device and increase in the torque of the supply roller 10 during image formation at the second image formation speed. As shown in FIG. 5 above, the torque threshold of the supply roller 10 exceeds 0.02 [n · m]. Set as appropriate. Further, the driving time at the first driving speed may be appropriately set according to the set threshold value, the specification of the apparatus, or the like.

[Example 5]
Next, Example 5 will be described.
In the fifth embodiment, when a new process unit 1 is mounted on the apparatus, the disengagement control for driving at the first drive speed for a predetermined time is performed.
The toner in the developing device contained in the new process unit 1 may be aggregated due to vibration or the like when the process unit is transported. For this reason, when the new process unit 1 is replaced, the toner in the developing device aggregated during transportation can be released by performing the release control that is driven at the first drive speed for a predetermined time.
As shown in FIG. 2, the control unit 200 communicates with the ID chip 111 when the process unit 1 is attached to the apparatus main body, and the identification information stored in the ID chip 111 is It is checked whether or not it matches the identification information used for communication. If they do not match, the control unit 200 determines that a new process unit 1 is mounted, and drives the drive motor 101 at the first drive speed for a predetermined time. As a result, the supply roller rotates at a rotational speed of 300 to 400 rpm for a predetermined time, and the aggregated toner in the developing device can be released.
The developing device may be configured to be detachable from the apparatus main body. In this case, the control is performed when the developing device is replaced with a new one.

  Further, as described above, since the fluidity of the toner in the supply unit is remarkably reduced in a low temperature and low humidity environment, stagnation is likely to occur in a predetermined region in the supply unit during image formation at the second image forming speed. Immediately, toner aggregation occurs, and the torque of the supply roller is increased. Therefore, when the temperature and humidity environment in the developing device is in a low temperature and low humidity environment, image formation may not be performed in the second image forming mode. That is, when forming an image on cardboard, OHP, or the like, the control unit 200 sets and sets the second image forming mode. However, before the second image forming mode is set, development is performed by the environment detection sensor. Detect the environment inside the device. As a result of the detection by the environment detection sensor, when the environment in the developing device is a low temperature / low humidity environment, the control unit 200 sets the first image forming mode, and uses the thick paper or the OHP at the first image forming speed. An image is formed on a recording sheet. At this time, the temperature of the fixing device is set to be higher than the temperature at the time of image formation on plain paper, so that the toner can be used at the first image formation speed even for recording paper having a large heat capacity such as thick paper and OHP. The image can be fixed satisfactorily.

  As described above, according to the image forming apparatus of the present embodiment, it is possible to suppress toner aggregation during image formation at the second image forming speed, increase in the torque of the supply roller, significant wear of the supply roller, and density unevenness. Can be suppressed.

  Further, when the continuous driving time of the second image forming speed exceeds a predetermined time, the toner staying in a predetermined area in the supply unit is circulated by performing a releasing control for driving the driving roller for the predetermined time at the first driving speed. -Can be stirred. Therefore, the toner can be prevented from aggregating during image formation at the second image formation speed, and damage to the components and an increase in the torque of the supply roller can be suppressed.

  Further, immediately after the second image forming mode is set, the second image forming is performed after releasing the toner in the supply unit that has been tightened by its own weight during the stop of the apparatus by performing the releasing control for driving for a predetermined time at the first driving speed. An image can be formed at a speed. Thereby, toner aggregation in the supply unit during image formation at the second image formation speed can be suppressed, and an increase in the torque of the supply roller can be suppressed.

  When the apparatus power is turned off and the apparatus is turned on for a long period of time, the toner in the supply unit is tightened. When the second image forming mode is set immediately after the apparatus is turned on, the time for driving at the first driving speed in the disassembling control performed immediately after setting the second image forming mode is set longer than normal. As a result, it is possible to form an image at the second image forming speed after sufficiently releasing the toner in the supply unit. As a result, even when image formation is performed at the second image formation speed immediately after the power is turned on, aggregation of toner in the supply unit during image formation can be suppressed, and an increase in torque of the supply roller can be suppressed.

  Further, when the second image forming mode is set when the pause time exceeds the predetermined time, the time for driving at the first driving speed in the disassembling control performed immediately after setting the second image forming mode is set to the normal time. Longer than. As a result, it is possible to form an image at the second image forming speed after sufficiently solving the toner in a state where the toner in the supply unit is clogged in a resting state for a long time. Therefore, even when image formation is performed at the second image formation speed after a long pause, aggregation of toner in the supply unit during image formation can be suppressed, and an increase in torque of the supply roller can be suppressed. .

  Further, when the temperature and humidity in the developing device is less than a predetermined value, the fluidity of the toner is remarkably reduced. Therefore, the time for driving at the first driving speed in the disassembly control performed immediately after setting the second image forming mode is Make it longer than normal. As a result, an image can be formed in a state where the toner in the supply unit is sufficiently removed. Therefore, even when the toner fluidity is remarkably lowered or even at the second image forming speed, aggregation of the toner in the supply unit during image formation can be suppressed, and the torque of the supply roller can be increased. Can be suppressed.

  Further, when the temperature and humidity in the developing device is less than a predetermined value, the fluidity of the toner is remarkably lowered, and when an image is formed in the second image forming mode, the toner is discharged in a predetermined area in the supply unit during image formation. There is a possibility that the torque of the supply roller rapidly increases due to aggregation. For this reason, when the temperature and humidity in the developing device is less than a predetermined value, the image is formed in the first image forming mode, so that the toner fluidity can be reduced during image formation even when the toner fluidity is significantly reduced. It is possible to suppress toner aggregation in a predetermined region in the supply unit.

  Further, by performing the disengagement control for driving the driving roller at the first driving speed for a predetermined time immediately before the setting of the second image forming mode is canceled, a predetermined value in the supply unit formed during image formation at the second image forming speed is obtained. The toner staying in the region and clogging can be removed. Accordingly, it is possible to suppress the presence of a toner-clogged area in the supply unit after the second image forming mode is completed.

  Further, when the torque of the supply roller exceeds a predetermined value, the control of releasing the drive roller for a predetermined time at the first drive speed is performed, so that the toner staying in the predetermined part in the supply unit and aggregating the toner can be released. It is possible to suppress breakage of parts and increase in torque of the supply roller.

  Further, when a new developing device is mounted on the apparatus main body, the disengagement control for driving the drive motor for a predetermined time at the first drive speed is performed. As a result, the toner aggregated due to vibration or the like during conveyance of the developing device can be removed.

  When the heat capacity of the recording material on which the image is formed is equal to or greater than a predetermined value, the second image forming mode is set and image formation is performed at the second image forming speed. Accordingly, the toner on the recording material can be melted and fixed on the recording material without increasing the temperature of the fixing device, and energy saving of the apparatus can be realized.

  In addition, when the temperature of the fixing device is equal to or lower than a predetermined value, the second image forming mode is set and image formation is performed at the second image forming speed, so that even when the temperature of the fixing device is low, the recording material is satisfactorily The toner can be melted and fixed on the recording material.

  Further, when image formation is performed in the second image formation mode, a recovery bias in the direction of recovering the developer from the developing roller is applied to the supply roller, so that the toner that has not adhered to the photosensitive member attached to the developing roller is electrically discharged. To recover. Thereby, the increase in torque of the supply roller can be suppressed as compared with the case where the toner that has not adhered to the photosensitive member attached to the developing roller is mechanically collected at the nip between the supply roller and the developing roller. Further, by separating the toner from the developing roller, the toner releasing effect is improved as compared with the mechanically separating from the developing roller.

  In addition, oilless fixing and low-temperature fixing can be realized by using a non-magnetic one-component toner containing a wax component as a developer.

1 is a schematic configuration diagram illustrating a printer according to an embodiment. FIG. 3 is an enlarged configuration diagram illustrating a process unit for K in the printer. FIG. 2 is an enlarged configuration diagram illustrating a process unit drive unit in the printer. FIG. 2 is a block diagram showing a part of an electric circuit in the printer. The figure which investigated the temporal change of the torque of a supply roller when rotating a supply roller by the rotation speed in 2nd image formation mode (low speed mode). The figure which showed the maximum torque of the supply roller in each rotation speed when a supply roller was continuously rotated for 20 minutes at each rotation speed. FIG. 3 is a sequence diagram of the first embodiment. FIG. 9 is a sequence diagram of the second embodiment. The figure which investigated the maximum torque of the supply roller when making it drive for 10 minutes at the drive speed in a 2nd image formation mode after each rest time. The figure which investigated the maximum torque of the supply roller when making it drive for 10 minutes at the drive speed in 2nd image formation mode under each environment. FIG. 10 is a sequence diagram of the third embodiment.

Explanation of symbols

1Y, C, M, K: Process unit 2Y, C, M, K: Photoconductor (latent image carrier)
5K: Developing device 6K: Hopper section (second storage chamber)
7K: Supply unit (first storage room)
9K: Communication port 10K: Supply roller (developer supply body)
11K: Development roller (developer carrier)

Claims (14)

A latent image carrier;
A developer carrying member for developing a latent image carried on the latent image carrying member by a developer carried on its own surface; a first storage chamber containing a developer for supplying the developer carrying member to the developer carrying member; A developer supply member for supplying the developer carried on its peripheral surface in the first storage chamber to the developer carrier as it rotates, and disposed above the first storage chamber and the first storage chamber. A second storage chamber for storing a developer to be replenished in the storage chamber, and a supply provided between the two chambers for dropping the developer in the second storage chamber into the developer supply member in the first storage chamber A developing means having a mouth;
Transfer means for transferring the toner image formed on the latent image carrier to the recording material, or transferring the toner image on the intermediate transfer member to the recording material after transferring the toner image to the intermediate transfer member;
Fixing means for fixing the toner image transferred to the recording material to the recording material by heat;
In an image forming apparatus comprising:
An image forming mode setting means for setting a first image forming mode for forming an image at a first image forming speed or a second image forming mode for forming an image at a second image forming speed slower than the first image forming speed; ,
Drive means for rotating the latent image carrier, the developer carrier, and the developer supply member with a common drive source;
Control means for controlling the drive of the drive source,
The control means sets the second image forming speed of the driving source at a predetermined timing from when the second image forming mode is set by the image forming mode setting means to when the setting is canceled. predetermined time fast comb than the driving speed at which the image formation mode, the drive source and the solution is driven to start the control, after construed control end, the driving speed of the driving source in the second image forming mode An image forming apparatus that performs image formation by returning to a driving speed at the time of image formation. The image forming apparatus according to claim 1.
The image forming apparatus according to claim 1, wherein the control unit starts the cracking control at a timing at which a continuous driving time of the second image forming speed exceeds a predetermined time. The image forming apparatus according to claim 1 or 2,
The image forming apparatus according to claim 1, wherein the control unit starts the cracking control at a timing immediately after the second image forming mode is set. The image forming apparatus according to claim 3.
After power ON of the apparatus, an image forming mode is first set at the timing just after the second image forming mode set at the time a second image forming mode, the amount of time the solution was controlled is started, the normal time at timing immediately after the second image forming mode setting, the image forming apparatus characterized by longer than during the time of the solution to control is started. The image forming apparatus according to claim 3 or 4,
Having downtime detection means for detecting downtime of the device;
Wherein, after a downtime of the apparatus exceeds a predetermined value, the amount of time the solution was controlled is started at the timing immediately after the second image forming mode set at the time when the second image forming mode is set, image forming apparatus characterized by longer than during the time of the second image forming mode set solution is started at the timing immediately after the control normal. The image forming apparatus according to any one of claims 3 to 5,
Equipped with temperature and humidity detection means for detecting the temperature and humidity of the developing means,
The control means is a starting control that is started immediately after the second image forming mode is set when the temperature and humidity value detected by the temperature and humidity detecting means when setting the second image forming mode is not more than a predetermined value. image forming apparatus characterized by a longer than during the time of the solution to control is started at the timing immediately after the second image forming mode set at the time of normal during the time of. The image forming apparatus according to claim 1,
Equipped with temperature and humidity detection means for detecting the temperature and humidity of the developing means,
The image forming mode setting unit sets the first image forming mode when the temperature / humidity value of the temperature / humidity detecting unit is not more than a predetermined value. The image forming apparatus according to claim 1,
The image forming apparatus according to claim 1, wherein the control unit starts the tear-off control immediately before the second image forming mode is released. The image forming apparatus according to claim 1,
A torque detecting means for detecting the torque of the developer supply member;
The image forming apparatus according to claim 1, wherein the control means starts the control when the torque value detected by the torque detection means exceeds a predetermined value. The image forming apparatus according to claim 1,
The developing means is configured to be detachable from the apparatus main body,
New article detecting means for detecting whether or not the developing means is new,
The image forming apparatus according to claim 1, wherein the control unit performs disassembly control when the new product detecting unit detects that the developing unit mounted on the apparatus is new. The image forming apparatus according to claim 1,
The image forming mode setting unit sets the second image forming mode when the heat capacity of a recording material for forming an image is equal to or greater than a predetermined value. 12. The image forming apparatus according to claim 1, wherein
A temperature detecting means for detecting the temperature of the fixing means;
The image forming mode setting unit sets the second image forming mode when the temperature of the fixing unit is equal to or lower than a predetermined value. The image forming apparatus according to claim 1.
An image forming apparatus, wherein when performing image formation in the second image forming mode, a bias in a direction in which the developer is collected from the developer carrier is applied to the developer supply member. The image forming apparatus according to claim 1,
An image forming apparatus using a non-magnetic one-component toner containing a wax component as the developer.

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