JP2015025841A - Image forming apparatus - Google Patents

Abstract

An image forming apparatus capable of operating at a higher speed than conventional ones is realized. The printing speed is changed based on a detection result (toner remaining amount) of a toner remaining amount detecting unit 33 and a detection result (surface temperature of a transfer belt) of an internal temperature sensor. Specifically, based on the phenomenon that as the remaining amount of toner increases, the melting does not easily occur even if the temperature of the toner rises, when T / H (toner weight is 50 g or more), T / L ( The belt temperature threshold, which is the condition for shifting to the deceleration printing, is set higher than when the toner weight is 40 g or more and less than 50 g. As a result, it is possible to avoid a situation where the printing speed is lowered in a situation where the toner does not melt, and thus, the operation can be performed at a higher speed than the conventional one. [Selection] Figure 9

Description

  The present invention relates to an image forming apparatus, and is suitable for application to an image forming apparatus such as a copying machine, a printer, a facsimile machine, and a multifunction machine.

  Conventionally, an image forming apparatus using an electrophotographic system includes a photosensitive drum, a charging device, a developing device, a transfer device, a fixing device, and a cleaning device. In this type of image forming apparatus, the surface of the photosensitive drum uniformly charged by the charging device is exposed by the exposure device to form an electrostatic latent image, and the electrostatic latent image is developed by the developing device to develop the photosensitive drum. After the toner image is formed on the surface, the toner image is transferred to a sheet by a transfer device, and the toner image is fixed to the sheet by a fixing device. An electrophotographic image forming apparatus performs printing by such an operation.

  On the other hand, in recent years, image forming apparatuses such as printers are required to further increase the operation speed. Actually, in an image forming apparatus, the fixing temperature can be increased, the printing interval can be shortened, and the driving speed can be increased, but on the other hand, the fixing temperature is increased and the printing interval is increased. The temperature inside the apparatus is likely to rise due to shortening and increasing the driving speed. Such an increase in temperature may cause melting of the toner, and further, melting of the toner may cause a situation such as a decrease in print quality or a toner clogging.

  Therefore, in the conventional image forming apparatus, the environmental temperature outside the apparatus and the temperature inside the apparatus are measured, and when the measured temperature exceeds a preset threshold, the fixing temperature, the printing interval, the driving speed, etc. are changed. By reducing the printing speed, the temperature rise is suppressed and toner melting is prevented (see, for example, Patent Document 1).

JP 2007-237682 A

  By the way, the melting of the toner is less likely to occur as the remaining amount of toner is larger. Actually, the temperature at which the melting of the toner occurs is higher when the remaining amount of toner in the developing device of the image forming apparatus is small or large. Becomes higher. Therefore, as in the conventional image forming apparatus, regardless of the remaining amount of toner, if the printing speed is changed depending on whether the measured temperature exceeds the threshold or not, the toner does not actually melt. Despite this, the printing speed may be reduced.

  The present invention has been made in consideration of the above points, and an object of the present invention is to propose an image forming apparatus capable of operating at a higher speed than conventional ones.

  In order to solve such problems, in the present invention, an image carrier that carries a latent image, a developer carrier that carries a developer for developing the latent image, and a latent image of the image carrier are developed. A transfer unit that transfers the developer image obtained in this way to a recording medium, a developer that contains a developer to be supplied to the developer carrier, and a developer amount detector that detects the amount of developer in the developer. A drive unit that operates at least one of the image carrier, the development carrier, and the transfer unit, a temperature detection unit that detects a temperature of the apparatus, a detection result of the developer amount detection unit, and the temperature detection The image forming apparatus is provided with a control unit that performs drive setting of the drive unit based on the detection result of the unit. As described above, in the present invention, the drive setting of the drive unit is performed based on the temperature of the image forming apparatus and the amount of developer in the developing device. As a result, the larger the amount of developer in the developing unit, the higher the temperature threshold, which is the condition for lowering the drive speed of the drive unit, to avoid the situation where the drive speed is lowered in a situation where the developer does not melt. it can.

  In the present invention, an image carrier that carries a latent image, a developer carrier that carries a developer for developing the latent image, and a development obtained by developing the latent image of the image carrier. A transfer unit that transfers a developer image to a recording medium, a developing unit that stores a developer to be supplied to the developer carrying member, a developer amount detecting unit that detects the amount of developer in the developing unit, and the image carrying unit A drive unit that operates at least one of the image forming unit, the developing carrier, and the transfer unit, and when the developer amount is determined to be less than a predetermined amount in the detection result of the developer amount detection unit, the drive unit The image forming apparatus is provided with a control unit that controls the driving speed to be lower than the driving speed when the developer amount is a predetermined amount or more. As described above, in the present invention, when the amount of developer in the developing device becomes less than a predetermined amount, the drive speed of the drive unit is reduced. As a result, it is possible to avoid a situation in which the driving speed is lowered when the developer amount is equal to or greater than a predetermined amount, that is, when the developer does not melt.

  According to the present invention, it is possible to avoid a situation in which the driving speed is lowered in a situation where the developer does not melt, and thus it is possible to realize an image forming apparatus capable of operating at a higher speed than in the past.

1 is a cross-sectional view illustrating an internal configuration of an image forming apparatus according to a first embodiment. It is sectional drawing which shows the structure of a developing unit. FIG. 6 is a perspective view illustrating a configuration of a toner remaining amount detection unit. FIG. 6 is a cross-sectional view for explaining a rotation operation of a toner remaining amount detection unit. It is a perspective view which shows the detection plate attached to one side of a developing device. FIG. 6 is a cross-sectional view for explaining the movement of a toner remaining amount detection unit according to the toner remaining amount. 2 is a block diagram illustrating functional blocks of the image forming apparatus according to the first embodiment. FIG. 6 is a table showing the relationship between toner weight and belt temperature when melting toner. It is a table | surface which shows the conditions when shifting to the deceleration printing in 1st Embodiment, and releasing the deceleration printing. 6 is a table showing the relationship between the linear velocity of the photosensitive drum and the maximum value of the belt temperature. 6 is a flowchart illustrating a printing speed setting process procedure according to the first embodiment. It is a flowchart which shows a printing processing procedure. FIG. 6 is a cross-sectional view illustrating an internal configuration of an image forming apparatus according to a second embodiment. FIG. 10 is a block diagram illustrating functional blocks of an image forming apparatus according to a second embodiment. 6 is a table showing a relationship among an apparatus external temperature, a toner weight, and a belt temperature when the toner is melted. It is a table | surface which shows the conditions when shifting to the deceleration printing in 2nd Embodiment, and releasing a deceleration printing. It is a flowchart which shows the printing speed setting process sequence (1) in 2nd Embodiment. It is a flowchart which shows the printing speed setting process sequence (2) in 2nd Embodiment. It is sectional drawing which shows the position (1) of the internal temperature sensor in other embodiment. It is sectional drawing which shows the position (2) of the internal temperature sensor in other embodiment.

  Hereinafter, modes for carrying out the invention (hereinafter referred to as embodiments) will be described in detail with reference to the drawings.

[1. First Embodiment]
[1-1. Internal configuration of image forming apparatus]
A first embodiment will be described. FIG. 1 shows an internal configuration of an image forming apparatus 1 having an electrophotographic color printer configuration. As shown in FIG. 1, the image forming apparatus 1 has a substantially box-shaped housing 2. In the following description, the left side when viewed from the front of the housing 2 is the left side of the housing 2, and the right side when viewed from the front of the housing 2 is the right side of the housing 2. Further, the direction from the left side to the right side of the housing 2 is the right direction, the direction from the right side to the left side of the housing 2 is the left direction, the direction from the lower side to the upper side of the housing 2 is the upward direction, and the upper side of the housing 2 The direction from the lower side to the lower side is the downward direction, the direction from the back side to the front side of the housing 2 is the front direction, and the direction from the front side to the back side of the housing 2 is the back direction.

  Inside the housing 2, there are four developing units 3 </ b> A to 3 </ b> D corresponding to each of toners as developers of four colors (black, yellow, magenta, and cyan) handled by the image forming apparatus 1. They are arranged side by side in the front-rear direction. Further, below the four developing units 3A to 3D (in the central portion of the housing 2), the transfer belt 4 extending in the front-rear direction, the drive roller 5 that drives the transfer belt 4, and the drive of the transfer belt 4 are stabilized. There are provided an idle roller 6 and a belt cleaning device 7 for cleaning the toner adhering to the transfer belt 4. The transfer belt 4 is for transferring the toner image developed by each of the developing units 3A to 3D onto the recording medium P while conveying the recording medium P such as paper.

  Further, in the vicinity of the drive roller 5, an internal temperature sensor 8 that is in contact with the transfer belt 4 is provided below the transfer belt 4. The internal temperature sensor 8 measures the surface temperature of the transfer belt 4 (hereinafter also referred to as belt temperature). Further, below the transfer belt 4 (at the bottom of the housing 2), a tray 9 for storing the recording medium P and a hopping roller 10 for picking up the recording medium P stored in the tray 9 from the tray 9 are provided. Yes. Further, a registration roller 11 is provided in front of the transfer belt 4 for conveying the recording medium P picked up by the hopping roller 10 to the transfer belt 4 without being skewed. Further, a fixing device 12 for fixing the toner image transferred onto the recording medium P onto the recording medium P by heating and pressing is provided behind the transfer belt 4. Further, a discharge roller 13 for discharging the recording medium P to the outside of the image forming apparatus 1 is provided above the fixing device 12.

  The four developing units 3A to 3D have the same configuration, and as shown in FIG. 2, a photosensitive drum 20, a charging roller 21 disposed around the photosensitive drum 20, an LED (Light Emitting Diode) head 22, A developing unit 23, a transfer roller 24, and a drum cleaning device 25 are included. As the photosensitive drum 20, for example, a photosensitive drum 20 having a 0.5 μm-thick charge generation layer and a 20 μm-thick charge transport layer on an aluminum base tube having a thickness of 0.75 mm and an outer diameter of 30 mm is used. .

  The charging roller 21 is a device for uniformly charging the surface of the photosensitive drum 20. For example, a conductive elastic body such as epichlorohydrin is provided on a conductor shaft made of a SUS (stainless steel) material. The surface is coated and arranged so as to contact the photosensitive drum 20. The LED head 22 is an exposure device for selectively exposing the uniformly charged surface of the photosensitive drum 20 to form a latent image pattern. For example, an LED element, an LED drive element, and a lens array (not shown) ), And is disposed at a position where the light emitted from the LED element is imaged on the surface of the photosensitive drum 20.

  The developing device 23 is a device for developing a toner image into a latent image pattern formed on the photosensitive drum 20. The developing device 23 includes a developing roller 30, a supply roller 31 disposed so as to be in contact with the developing roller 30, a regulation blade 32 disposed so as to press the tip portion against the developing roller 30, and the inside of the developing device 23. The toner remaining amount detection unit 33 detects the remaining amount of toner, and is disposed at a position where the developing roller 30 is brought into contact with the photosensitive drum 20. Further, the developing device 23 is provided with an opening 23A communicating with a toner cartridge 34 mounted on the upper portion of the developing device 23 at the upper end thereof, so that toner is replenished from the toner cartridge 34 through the opening 23A. It has become.

  The developing roller 30 has, for example, an elastic layer formed in a roll shape on a conductive shaft (core metal) made of a SUS material, and has a surface layer that covers the elastic layer. For example, urethane rubber or silicone rubber is used for the elastic layer, and for example, a surface layer treated with a urethane solution, or one coated with acrylic resin or acrylic-fluorine copolymer resin is used for the surface layer. Carbon black is blended in the surface layer of the developing roller 30 made of acrylic resin or acrylic-fluorine copolymer resin in order to impart conductivity.

  The supply roller 31 is formed of a conductive shaft (core metal) made of SUS material and an elastic layer. The elastic layer is, for example, a conductive silicon rubber foam layer or a conductive urethane rubber foam layer. In order to give the elastic layer semi-conductivity, for example, acetylene black or carbon black may be added. The regulating blade 32 is a member for regulating the layer thickness of the toner carried on the surface of the developing roller 30. The regulating blade 32 is made of, for example, SUS having a plate thickness of 0.08 mm, and the contact portion with the developing roller 30 is bent. The bending radius R of the bent portion subjected to the bending process is, for example, 0.2 mm, and the linear pressure against the developing roller 30 is, for example, 30 gf / cm. Note that the radius of curvature R and the linear pressure of the regulating blade 32 are not limited to the above-described numerical values, and are appropriately set based on the toner amount on the developing roller 30 and the toner charge amount.

  The transfer roller 24 is for transferring the toner image formed on the photosensitive drum 20 to the recording medium P or the transfer belt 4 and is made of, for example, a conductive foaming elastic body. The drum cleaning device 25 is a device for scraping off residual toner that has not been transferred on the photosensitive drum 20 and waste toner after transfer, and then discarding the toner. The drum cleaning device 25 includes, for example, a cleaning blade 25A using rubber, and is disposed at a position where the tip of the cleaning blade 25A comes into contact with the surface of the photosensitive drum 20. The image forming apparatus 1 has such an internal configuration. The toner remaining amount detection unit 33 will be described in detail below.

[1-2. Configuration of toner remaining amount detection unit]
As shown in FIG. 3, the toner remaining amount detection unit 33 includes, for example, a detection plate 40 made of SUS, a stirring bar 41 made of resin, and a stirring gear 42 made of SUS. 40 is fixed, and the stirring gear 42 is connected to the other end. The detection plate 40 has a shape in which a part of a disk is cut out in the radial direction. The cut-out portion 40A of the detection plate 40 is hereinafter referred to as a cut-out portion 40A.

  Further, the stirring bar 41 is bent so that the central axis of the stirring part 41C between the one end part 41A and the other end part 41B is shifted outward from the central axis of the one end part 41A and the other end part 41B. Yes. Furthermore, the end of the other end portion 41B of the stirring bar 41 is bent in a direction orthogonal to the central axis of the other end portion 41B. The stirring gear 42 is provided with a rib 42 </ b> A that contacts the end of the other end portion 41 </ b> B of the stirring bar 41.

  As shown in FIG. 2, the toner remaining amount detecting unit 33 is disposed between the opening 23A of the developing unit 23 and the developing roller 30 and above the nip between the developing roller 30 and the supply roller 31, and has a stirring bar. The detection plate 40 and the agitation gear 42 are rotatably supported on both side surfaces of the developing unit 23 so that 41 is positioned in the developing unit 23 with its longitudinal direction parallel to the axial direction of the photosensitive drum 20.

  As shown in FIG. 4, when the stirring gear 42 is rotated counterclockwise in the drawing by the driving means (not shown), the remaining toner amount detection unit 33 causes the rib 42A of the stirring gear 42 to The stir bar 41 is rotated counterclockwise in the figure by engaging with the engaging part 41Ba of the end 41B and pressing it counterclockwise in the figure. At this time, although not shown in FIG. 4, the detection plate 40 also rotates counterclockwise in the drawing.

  As shown in FIGS. 4A to 4C, when the stirring bar 41 is pressed by the stirring gear 42 and rotated from the bottom dead center to the top dead center, the engagement between the other end 41B and the rib 42A. Then, as shown in FIGS. 4 (D) and 4 (E), until the bottom dead center is reached, the stirring bar 41 rotates faster than the stirring gear 42 due to its own weight and rotates counterclockwise in the figure. It is supposed to be. Although not shown in FIG. 4, when the stirring bar 41 is at the top dead center, the stirring portion 41C of the stirring bar 41 and the cutout portion 40A of the detection plate 40 are at the highest position, and the stirring bar 41 is at the bottom dead center. The stirring portion 41C of the stirring bar 41 and the cutout portion 40A of the detection plate 40 are at the lowest position.

  On the other hand, as shown in FIG. 5, a detection plate 40 is rotatably supported on one side of the developing unit 23, and a light emitting portion 43 is provided below the center of the detection plate 40. Yes. The light emitted from the light emitting portion 43 is detected only when at least a part of the cutout portion 40A of the detection plate 40 comes to a position facing the light emitting portion 43 (that is, below the center of the detection plate 40). 40 is guided to a light incident part 45 provided below the light emitting part 43 through a plate cover 44 covering the detection plate 40, and is otherwise blocked by the detection plate 40. It has become. The toner remaining amount detection unit 33 has such a configuration.

  Here, the detection operation of the remaining toner amount detection unit 33 when the remaining toner amount is detected will be described with reference to FIG. As described above, the toner remaining amount detection unit 33 is rotated until the stirring bar 41 reaches the top dead center from the bottom dead center by pressing the stirring bar 41 as the stirring gear 42 rotates. . Thereafter, the toner remaining amount detection unit 33 is rotated by its own weight of the stirring bar 41. At this time, as shown in FIG. 6A, the developing device is located more than the upper end of the stirring unit 41C of the stirring bar 41. Only when the upper surface of the toner Tn contained in the toner cartridge 23 is positioned upward, the toner does not rotate by its own weight, and the stirring portion 41C of the stirring bar 41 reaches the bottom dead center as the stirring gear 42 rotates. Rotated until.

  On the other hand, as shown in FIGS. 6B to 6E, when the upper surface of the toner accommodated in the developing device 23 is located below the upper end of the stirring portion 41C of the stirring bar 41, stirring is performed. After the stirring portion 41C of the bar 41 reaches the top dead center, the stirring bar 41 rotates faster than the stirring gear 42 by its own weight. At this time, the agitation part 41C of the agitation bar 41 comes into contact with the upper surface of the toner accommodated in the developing device 23, so that the rotation is temporarily stopped. At this time, the rotation position of the cutout portion 40A of the detection plate 40 is a rotation position corresponding to the upper surface position of the toner in the developing unit 23, and therefore is a rotation position corresponding to the remaining amount of toner in the developing unit 23. I can say that. Therefore, the remaining amount of toner in the developing device 23 can be detected by detecting the rotational position of the cutout portion 40A of the detection plate 40 at this time.

  Further, after the toner remaining amount detection unit 33 once stops rotating, when the rib 42A of the stirring gear 42 and the engaging portion 41Ba of the stirring bar 41 are engaged again, the rib 42A presses the engaging portion 41Ba. As a result, the stirring portion 41C of the stirring bar 41 rotates while sinking into the toner. By measuring the rotation period of the remaining toner amount detection unit 33 at this time, the remaining toner amount in the developing unit 23 can be detected. Note that the light emitted from the light emitting portion 43 passes through the detection plate 40 and enters the light incident portion 45 only when the stirring bar 41 is located at the bottom dead center. Therefore, the period in which the light emitted from the light emitting part 43 is incident on the light incident part 45 is equal to the rotation period of the remaining toner amount detecting part 33. Therefore, the period in which the light emitted from the light emitting part 43 enters the light incident part 45 may be measured as the rotation period of the remaining toner amount detecting part 33. In addition, the rotation period of the toner remaining amount detection unit 33 may be measured by another method without being limited thereto.

  As described above, in the toner remaining amount detection unit 33, the rotation position of the notch 40 </ b> A of the detection plate 40 when the stirring bar 41 stops after rotating to the top dead center or the rotation cycle of the toner remaining amount detection unit 33 is determined. The toner remaining amount can be detected. In the image forming apparatus 1 according to the present embodiment, the remaining amount of toner is detected based on the rotation period. Further, the remaining toner detection unit 33 not only detects the remaining amount of toner but also has a role of stirring the toner in the developing device 23 by rotating the stirring bar 41 as described above.

[1-3. Functional block of image forming apparatus]
Next, functional blocks of the image forming apparatus 1 will be described. As shown in FIG. 7, the functional blocks of the image forming apparatus 1 include a control unit 50, a drive control unit 51, an exposure control unit 52, a voltage control unit 53, a drum motor 54, a belt motor 55, an internal temperature sensor 8, and a charging roller. 21, an LED head 22, a transfer roller 24, a developing roller 30, a supply roller 31, a regulation blade 32, and a toner remaining amount detection unit 33. Note that the control unit 50, the drive control unit 51, the exposure control unit 52, the voltage control unit 53, the drum motor 54, and the belt motor 55 are omitted in FIG. 1, but are provided at predetermined locations in the image forming apparatus 1. ing.

  For example, when receiving a print support from a host device (not shown), the control unit 50 is based on the detection result of the toner remaining amount detection unit 33 (that is, the remaining amount of toner) and the detection result of the internal temperature sensor 8 (that is, the belt temperature). Thus, the printing speed is determined, and a printing operation is instructed to the drive control unit 51, the exposure control unit 52, and the voltage control unit 53.

  When receiving an instruction from the control unit 50, the drive control unit 51 drives the drum motor 54 that rotates the photosensitive drum 20 and the developing roller 30, and the belt motor 55 that rotates the drive roller 5 to drive the transfer belt 4. Control. In the image forming apparatus 1, the drum motor 54 rotates the photosensitive drum 20 and the developing roller 30 in reverse via a gear. However, the motor that rotates the photosensitive drum 20 and the developing roller 30 rotate. You may make it provide the motor to make separate. Upon receiving an instruction from the control unit 50, the exposure control unit 52 controls the light emission of the LED head 22. When receiving an instruction from the control unit 50, the voltage control unit 53 controls the voltage applied to the charging roller 21, the developing roller 30, the supply roller 31, the regulating blade 32, and the transfer roller 24.

  The image forming apparatus 1 includes such functional blocks. In the printing process, the surface of the photosensitive drum 20 is uniformly charged by applying a charging voltage to the charging roller 21 under the control of the voltage control unit 53, and then exposed. The LED head 22 emits light under the control of the control unit 52 to form an electrostatic latent image pattern on the surface of the photosensitive drum 20. Then, the image forming apparatus 1 applies a developing voltage to the developing roller 30 on which the toner thin layer is formed on the surface under the control of the voltage control unit 53 and presses the developing roller 30 on the photosensitive drum 20. The electrostatic latent image pattern is developed. Here, in order to uniformly form a toner thin layer on the developing roller 30 on the supply roller 31 and the regulating blade 32 and to set the toner charge amount in the toner thin layer to a predetermined value, the control of the voltage control unit 53 is performed. Thus, a supply voltage and a regulation blade voltage are applied, respectively.

  Next, the image forming apparatus 1 applies a transfer voltage to the transfer roller 24 under the control of the voltage control unit 53. Further, the image forming apparatus 1 drives the drive roller 5 by the belt motor 55 driven by the control of the drive control unit 51 to transfer the developed toner image on the photosensitive drum 20 onto the recording medium P, and then the recording medium P The upper toner image is fixed on the recording medium P by the fixing device 12. Then, the image forming apparatus 1 discharges the recording medium P on which the toner image is fixed to the outside of the image forming apparatus 1 by the discharge roller 13 and ends the printing process. Residual toner remaining on the photosensitive drum 20 without being transferred is removed by the drum cleaning device 25. The image forming apparatus 1 prints a color image on the recording medium P through such a printing process.

[1-4. Applied voltage setting in image forming apparatus]
By the way, when the image forming apparatus 1 is operated in a room temperature and humidity environment using negatively chargeable toner, the applied voltage settings are, for example, a charging voltage of −1050 V, a developing voltage of −200 V, a supply voltage of −300 V, and a regulating blade The voltage is -300V. Here, the surface of the photosensitive drum 20 is charged when a charging voltage equal to or higher than a predetermined value is applied to the charging roller 21, and the surface potential changes in proportion to the charging voltage applied to the charging roller 21.

  Actually, in the image forming apparatus 1, when a charging voltage of −1050V is applied, the surface potential of the photosensitive drum 20 becomes −500V. In the image forming apparatus 1, the latent image potential of the latent image pattern formed on the photosensitive drum 20 by the light emission of the LED head 22 becomes −50 V. From the developing roller 30 to the latent image pattern having such a latent image potential. The toner is reversely developed. Note that when a positive voltage is used instead of a negatively chargeable toner, the charging voltage, developing voltage, supply voltage, and regulation blade voltage are opposite in sign to those when a negatively chargeable toner is used.

[1-5. Toner weight in developer unit]
Next, the toner weight in the developing device 23 will be described. In the image forming apparatus 1 of the present embodiment, if the toner weight in the developing unit 23 is less than 40 g, the risk of fading printing during high duty printing increases, so the toner weight in the developing unit 23 is 40 g. At that time, for example, a display to warn the user to replace the toner cartridge 34 is displayed on a display unit (not shown).

  Further, in the image forming apparatus 1, when the toner weight reaches 50 g, for example, a message indicating that preparation for replacement of the toner cartridge 34 is made is displayed on a display unit (not shown). Here, in the case of the image forming apparatus 1, 500% of 5% duty printing is performed after a message indicating that the toner cartridge 34 is prepared for replacement until a warning is given to replace the toner cartridge 34. Be able to.

  Further, in the image forming apparatus 1, when the toner weight in the developing unit 23 is less than 50 g, the upper surface of the toner in the developing unit 23 is higher than the upper end of the stirring unit 41C of the stirring bar 41 located at the top dead center. Designed to be located below. That is, the stirring bar 41 of the toner remaining amount detection unit 33 is designed to rotate by its own weight when the toner weight in the developing unit 23 is less than 50 g. Hereinafter, the state where the toner weight in the developing unit 23 is 50 g or more is referred to as T / H (Toner / High), the state of 40 g or more and less than 50 g is T / L (Toner / Low), and the state of less than 40 g is T / E. (Toner / Empty).

[1-6. Relationship between toner weight in developing unit and belt temperature when toner melts]
Here, the relationship between the toner weight in the developing device 23 and the surface temperature (belt temperature) of the transfer belt 4 detected by the internal temperature sensor 8 at the time of melting the toner is shown in the table of FIG. This relationship was obtained as a result of an experiment, and the temperature outside the image forming apparatus 1 at the time of the experiment was set to 32 ° C., the upper limit temperature of the apparatus specification. As shown in FIG. 8, in the image forming apparatus 1, it can be seen that the lower the toner weight in the developing unit 23 and the smaller the remaining amount of toner, the lower the belt temperature when melting the toner.

  The heat generated in the developing unit 23 that causes toner melting is mainly due to friction between the developing roller 30 and the regulating blade 32. That is, the heat generated by the regulating blade 32 due to the friction between the developing roller 30 and the regulating blade 32 is transmitted to the toner in the developing unit 23 and causes the toner to melt. The heat generated by the regulating blade 32 is transmitted from the developing roller 30 to the transfer belt 4 via the photosensitive drum 20 and increases the belt temperature.

  Here, if the remaining amount of toner in the developing unit 23 is small, the temperature of the entire toner in the developing unit 23 is likely to rise, so that the temperature of the toner is faster than the heat generated by the regulating blade 32 is transmitted to the transfer belt 4. This increases the difference between the belt temperature and the toner temperature. As a result, as shown in FIG. 8, when the remaining amount of toner is small (that is, when the toner weight is light), the belt temperature at which toner melting occurs is lower than when the amount of toner is heavy (when heavy). In consideration of this point, in the image forming apparatus 1, the printing speed is changed based on the belt temperature and the remaining amount of toner so that toner melting does not occur.

  In the image forming apparatus 1, the belt temperature obtained from the internal temperature sensor 8 and the remaining toner amount obtained from each of the four remaining toner amount detection units 33 provided in each of the developing units 3A to 3D are used. The printing speed is changed so that toner melting does not occur in all of the developing units 3A to 3D.

[1-7. Changing the printing speed based on the belt temperature and the remaining amount of toner]
Actually, in the image forming apparatus 1, as shown in the table of FIG. 9, when T / L (that is, the toner weight is 40 g or more and less than 50 g) and when T / H (that is, the toner weight is 50 g or more), The belt temperature condition (referred to as the deceleration printing transition condition) when shifting to the deceleration printing is changed. Note that the term “decelerated printing” as used herein refers to printing at a lower speed than normal printing (normal printing).

  As shown in FIG. 9, in the image forming apparatus 1, when the toner weight corresponding to the lower limit of T / L is 40 g, toner melting occurs at a belt temperature of 46 ° C. Therefore, deceleration at T / L The print transition condition is set to 45 ° C. or higher. The threshold value (45 ° C.) as the first threshold value at this time is preferably lower than the belt temperature (46 ° C.) at which toner melting occurs and as close as possible. In addition, when the toner weight corresponding to the lower limit of T / H is 50 g, toner melting occurs at a belt temperature of 48 ° C. Therefore, the deceleration printing transition condition at T / H is set to 47 ° C. or higher. Yes. It is desirable that the threshold value (47 ° C.) as the first threshold value at this time is also lower than the belt temperature (48 ° C.) at which toner melting occurs and as close as possible. As described above, in the image forming apparatus 1, when the belt temperature becomes 45 ° C. or higher at T / L, and when the belt temperature becomes 47 ° C. or higher at T / H, the mode shifts to decelerating printing. .

  Also, the belt temperature condition when canceling the deceleration printing (this is called the deceleration printing cancellation condition) is set to less than 43 ° C. with a deceleration printing transition condition and a hysteresis (that is, providing a temperature difference). Has been. This is for canceling the decelerated printing and returning the printing speed after the temperature of the toner in the developing unit 23 is surely lowered. Also, if the threshold value for the decelerating printing transition condition (first threshold value) and the threshold value for the decelerating printing release condition (second threshold value) are set to the same temperature, when the belt temperature fluctuates in the vicinity of this threshold value, the decelerating condition Printing and normal printing are alternately switched many times in a short time, and the printing speed is rather slow. The temperature difference between the threshold value of the deceleration printing transition condition and the threshold value of the deceleration printing cancellation condition is also to prevent such a situation. As described above, in the image forming apparatus 1, in both cases of T / L and T / H, when the belt temperature becomes less than 43 ° C., the normal printing is resumed from the deceleration printing.

  Furthermore, in the image forming apparatus 1 according to the present embodiment, the linear speed of the photosensitive drum 20 is changed to shift from normal printing to decelerating printing or vice versa. In the image forming apparatus 1, the control unit 50 changes the linear speed of the photosensitive drum 20 by instructing the drive control unit 51 to change the setting of the rotational speed that is the drive setting of the drum motor 54. It is like that. Here, the relationship between the linear velocity of the photosensitive drum 20 and the belt temperature is shown in the table of FIG. This relationship was also obtained as a result of the experiment. The temperature outside the image forming apparatus 1 at the time of the experiment was 32 ° C., the upper limit temperature of the apparatus specification, and the toner weight in the developing unit 23 was 70 g.

  As shown in FIG. 10, in the image forming apparatus 1, when the linear velocity of the photosensitive drum 20 is 310 mm / sec, the maximum value of the belt temperature is 53 ° C., and when the linear velocity is 210 mm / sec, the belt temperature The maximum value is 44 ° C. It is assumed that the maximum belt temperature does not become higher than 44 ° C. even if the toner weight is reduced. Therefore, in the image forming apparatus 1, when printing is performed with the linear speed of the photosensitive drum 20 being 210 mm / sec, the belt temperature does not exceed the threshold value (45 ° C. or 47 ° C.) of the deceleration printing transition condition. That is, if the linear printing speed of the photosensitive drum 20 is set to 210 mm / sec and the decelerated printing is performed, the printing can be continued without melting the toner.

  Therefore, in the image forming apparatus 1 of the present embodiment, during normal printing, the rotational speed of the drum motor 54 is increased so that the linear speed of the photosensitive drum 20 is, for example, 310 mm / sec. The rotational speed of 54 is lowered so that the linear speed of the photosensitive drum 20 is 210 mm / sec.

  As described above, during normal printing, the image forming apparatus 1 performs printing as fast as possible until the belt temperature becomes equal to or higher than the threshold value of the deceleration printing transition condition. If the threshold value is exceeded, the process shifts to decelerated printing, and the printing speed is lowered to lower the belt temperature (that is, lower the toner temperature). Note that the linear speed during normal printing and the linear speed during decelerated printing of the photosensitive drum 20 are not limited to the above-described numerical values, and are appropriately set based on heat generation and heat dissipation of the image forming apparatus 1 and the developing unit 23. Is.

[1-8. Printing speed setting process and printing process]
Here, a process of setting the printing speed by changing the setting of the linear speed of the photosensitive drum 20 (this is called a printing speed setting process), and a process of printing at the set printing speed (this is called a printing process). The procedure of will be described in detail. First, the procedure of the printing speed setting process will be described with reference to the flowchart shown in FIG. This printing speed setting process is a process performed under the control of the control unit 50.

  For example, when the power of the image forming apparatus 1 is turned on or when the control unit 50 returns from the sleep mode to the operation mode, the control unit 50 of the image forming apparatus 1 starts the printing speed setting process and proceeds to step SP1. At this time, it is assumed that the setting of the linear velocity of the photosensitive drum 20 is an initial value (for example, 310 mm / sec). In step SP1, the control unit 50 detects the remaining amount of toner by the toner remaining amount detecting unit 33 at a predetermined timing, and proceeds to the next step SP2. In step SP2, the control unit 50 determines which of T / H, T / L, and T / E is the state obtained as the detection result of the toner remaining amount detection unit 33. The control unit 50 determines the state based on the detection result of the least remaining toner amount among the detection results of the remaining toner amount detection units 33 of the developing units 3A to 3D. This is because the toner is more likely to melt as the remaining amount of toner decreases.

  Here, when the detection result of the toner remaining amount detecting unit 33 is T / E (the remaining amount of toner is less than 40 g), the control unit 50 moves to step SP3 and warns to replace the toner cartridge 34. Is displayed and the printing speed setting process is terminated. On the other hand, when the detection result of the toner remaining amount detection unit 33 is T / H (the remaining amount of toner is 50 g or more), the control unit 50 moves to step SP4 and the internal temperature sensor 8 at this time. It is determined whether or not the detection result (belt temperature) is 47 ° C. or higher. If a negative result is obtained in this step SP4 because the belt temperature is not 47 ° C. or higher, this means that the toner does not melt at this time. At this time, the control unit 50 returns to step SP1 without changing the setting of the linear velocity of the photosensitive drum 20 from the initial value. As a result, the image forming apparatus 1 performs normal printing with a printing speed higher than that during decelerating printing.

  On the other hand, if the belt temperature is 47 ° C. or higher and an affirmative result is obtained in this step SP4, this may cause toner melting, and it is necessary to reduce the printing speed and lower the toner temperature. It means that there is. At this time, the control unit 50 moves to step SP5, sets the drive of the drum motor 54 so as to change the setting of the linear speed of the photosensitive drum 20 to 210 mm / sec corresponding to the deceleration printing, and moves to step SP7. . As a result, the image forming apparatus 1 performs decelerated printing at a lower printing speed than during normal printing.

  If the detection result of the toner remaining amount detection unit 33 is T / L (the toner remaining amount is 40 g or more and less than 50 g), the control unit 50 proceeds to step SP6 and the detection of the internal temperature sensor 8 at this time. It is determined whether the result (belt temperature) is 45 ° C. or higher. Here, if a negative result is obtained in step SP6 because the belt temperature is not 45 ° C. or higher, this means that the toner does not melt at this time. At this time, the control unit 50 returns to step SP1 without changing the setting of the linear velocity of the photosensitive drum 20 from the initial value.

  On the other hand, if the belt temperature is 47 ° C. or higher and an affirmative result is obtained in this step SP4, this may cause toner melting, and it is necessary to reduce the printing speed and lower the toner temperature. It means that there is. At this time, the control unit 50 moves to step SP5, sets the drive of the drum motor 54 so as to change the setting of the linear speed of the photosensitive drum 20 to 210 mm / sec corresponding to the deceleration printing, and moves to step SP7. .

  In step SP7, the control unit 50 detects the remaining amount of toner with the toner remaining amount detecting unit 33 again at a predetermined timing, and proceeds to the next step SP8. In step SP8, the control unit 50 determines whether the state obtained as a detection result of the toner remaining amount detection unit 33 is T / E. Here, if the detection result of the toner remaining amount detection unit 33 is T / E (the remaining amount of toner is less than 40 g), and if an affirmative result is obtained in step SP8, the control unit 50 proceeds to step SP9, and the toner A warning to replace the cartridge 34 is displayed, and the printing speed setting process is terminated.

  On the other hand, if the result of detection by the toner remaining amount detection unit 33 is not T / E (the remaining amount of toner is less than 40 g) and a negative result is obtained in step SP8, the control unit 50 proceeds to step SP10. In step SP10, the control unit 50 determines whether or not the detection result (belt temperature) of the internal temperature sensor 8 at this time is less than 43 ° C. Here, if a negative result is obtained in this step SP10 because the belt temperature is not less than 43 ° C., this means that the belt temperature has not dropped to a temperature sufficient for normal printing (that is, the toner temperature is low). Is not lowered enough). At this time, the control unit 50 returns to step SP7 without changing the setting of the linear velocity of the photosensitive drum 20 from 210 mm / sec.

  On the other hand, if an affirmative result is obtained in this step SP10 because the belt temperature is less than 43 ° C., this means that the belt temperature has dropped to a temperature sufficient for normal printing (ie, the toner temperature is sufficient). It means) At this time, the control unit 50 moves to step SP11, sets the drive of the drum motor 54 so as to return the linear velocity setting of the photosensitive drum 20 to the initial value corresponding to normal printing, and returns to step SP1. Based on such printing speed setting processing, the image forming apparatus 1 sets the printing speed by changing the linear speed setting of the photosensitive drum 20.

  Next, the print processing procedure will be described with reference to the flowchart shown in FIG. This printing process is a process performed under the control of the control unit 50, and a process performed in parallel with the printing speed setting process. In step SP20, the control unit 50 of the image forming apparatus 1 waits for reception of print data from the host device. When the print data is received, the control unit 50 proceeds to step SP21.

  In step SP21, the control unit 50 starts printing based on the print data. At this time, the control unit 50 rotates the photosensitive drum 20 at the set linear speed by driving the drum motor 54 based on the drive setting at this time. Thus, if the linear velocity of the photosensitive drum 20 set at this time is an initial value, normal printing is started, and the linear velocity of the photosensitive drum 20 set at this time is 210 mm / sec, which is slower than the initial value. If so, decelerated printing is started.

  After starting printing in this manner, the control unit 50 proceeds to step SP22. In step SP22, the control unit 50 determines whether printing of all pages based on the print data has been completed. If a negative result is obtained in step SP22 because printing of all pages has not been completed, the control unit 50 proceeds to step SP23.

  In step SP23, the control unit 50 determines whether it is necessary to change the linear velocity of the photosensitive drum 20. Specifically, every time printing for a predetermined number of pages is completed, the control unit 50 checks whether or not the setting of the linear speed of the photosensitive drum 20 has been changed by the above-described printing speed setting process. . Then, the control unit 50 determines that it is not necessary to change the linear speed if the setting of the linear speed is not changed, while it is necessary to change the linear speed if the setting of the linear speed is changed. It is determined that there is. If it is determined that the linear velocity of the photosensitive drum 20 needs to be changed, the control unit 50 obtains an affirmative result at step SP23 and proceeds to step SP24. In step SP24, after changing the linear speed of the photosensitive drum 20 (that is, after changing the printing speed), the control unit 50 continues printing the remaining pages and returns to step SP22.

  On the other hand, if it is determined that there is no need to change the linear velocity of the photosensitive drum 20, the control unit 50 continues to print the remaining pages without changing the linear velocity of the photosensitive drum 20, and proceeds to step SP22. Return. If the control unit 50 obtains a positive result in step SP22 by completing the printing of all pages, the control unit 50 returns to step SP20 and waits for the next print data. Based on such a printing process, the image forming apparatus 1 performs printing while appropriately changing the printing speed.

[1-9. Effects according to the first embodiment]
As described above, in the image forming apparatus 1, the temperature of the belt that shifts to decelerating printing between T / L (toner weight is 40 g or more and less than 50 g) and T / H (toner weight is 50 g or more). The condition (deceleration printing transition condition) was changed. That is, in the image forming apparatus 1, based on the phenomenon that the more the remaining amount of toner is, the more difficult the melting occurs even if the toner temperature rises, the T / H time is more than the T / L time. The belt temperature threshold, which is the condition for shifting to the deceleration printing, was set high.

  Specifically, the control unit 50 of the image forming apparatus 1 determines that the remaining toner amount is 50 g or more (T / H) when the detection result of the remaining toner amount detection unit 33 is 40 g or more and less than 50 g (T / L). If the detection result of the remaining toner amount detection unit 33 is 50 g or more (T / H), the belt temperature threshold value, which is a condition for shifting to reduced printing, is set to be lower from 47 ° C. to 45 ° C. The belt temperature threshold, which is a condition for shifting to the deceleration printing, is set higher from 45 ° C. to 47 ° C. than when the amount is 40 g or more and less than 50 g (T / L).

  By doing so, in the image forming apparatus 1, for example, as compared with the conventional case in which the belt temperature threshold as the deceleration printing transition condition is set to one fixed value, the toner melting is similarly prevented while the deceleration printing is performed. It is possible to increase the opportunities to perform normal printing at a speed higher than that of decelerating printing by reducing the opportunity to perform printing. Thus, the image forming apparatus 1 can perform printing at a higher speed than conventional.

  In the image forming apparatus 1, the toner remaining amount detection unit 33 that detects the remaining amount of toner by rotating the stirring bar 41 includes an opening 23 </ b> A at the upper end of the developing device 23 and the developing roller 30 at the center of the developing device 23. It is arranged between. In this case, as shown by a dotted line in FIG. 2, the stirring range of the stirring bar 41 is limited. Therefore, as the remaining amount of toner is smaller as in the case of T / L, the toner is not stirred and the developing roller 30 is not stirred. Between the toner and the supply roller 31 and the toner is easily melted.

  Therefore, for example, if the printing speed is changed only by the deceleration printing transition condition when the remaining amount of toner is small as in T / L, the remaining amount of toner is large as in T / H. In addition, the chance of normal printing can be significantly reduced. In other words, in the image forming apparatus 1, by appropriately changing the belt temperature threshold that is the deceleration printing transition condition according to the remaining amount of toner, as described above, when the remaining amount of toner is large, It is possible to prevent a situation in which the opportunities for normal printing are reduced.

  In other words, the present invention can be said to be particularly effective for an image forming apparatus that detects the remaining amount of toner by a mechanism such as the remaining toner detection unit 33. In the present embodiment, in order to obtain the effect more reliably, whether or not to perform the deceleration printing is determined based on the detection result of the internal temperature sensor 8 and the remaining amount of toner. Based on this, it may be determined whether or not to perform decelerated printing. In this case, the control unit 50 does not perform decelerating printing when the remaining amount of toner is equal to or greater than a predetermined amount (for example, T / H), and when the remaining amount of toner becomes less than the predetermined amount (for example, becomes T / L). Once you do it, do slow printing. Even in this case, a certain effect can be obtained.

[2. Second Embodiment]
[2-1. Internal configuration of image forming apparatus]
Next, a second embodiment will be described. As shown in FIG. 13, the second embodiment differs from the first embodiment in that an external temperature sensor 101 is provided in addition to the internal temperature sensor 8 in the image forming apparatus 100. ing. Therefore, since the internal configuration of the image forming apparatus 100 other than the external temperature sensor 101 is the same as that of the image forming apparatus 1 of the first embodiment, the description thereof is omitted.

  The external temperature sensor 101 is for measuring an external temperature around the image forming apparatus 100 and is arranged at a predetermined location in the image forming apparatus 100. The predetermined portion is a portion that is not affected by heat generation in the image forming apparatus 100. By arranging in such a place, the temperature measured by the external temperature sensor 101 can be regarded as the external temperature around the image forming apparatus 100. Actually, in the image forming apparatus 100, since the main heat source is the fixing device 12, the external temperature sensor 101 is arranged at the center of the front end in the image forming apparatus 100, away from the fixing device 12. .

[2-2. Functional block of image forming apparatus]
Next, functional blocks of the image forming apparatus 100 will be described. As shown in FIG. 14, the functional block of the image forming apparatus 100 has a configuration in which an external temperature sensor 101 is added to the functional block of the image forming apparatus 1. Therefore, description of functional blocks other than the external temperature sensor 101 is omitted.

  When the control unit 50 of the image forming apparatus 100 receives print support from a host device (not shown), for example, the detection result of the toner remaining amount detection unit 33 (that is, the remaining amount of toner) and the detection result of the internal temperature sensor 8 (that is, the detection result) The printing speed is determined based on the belt temperature) and the detection result (that is, the external temperature) of the external temperature sensor 101, and the printing operation is instructed to the drive control unit 51, the exposure control unit 52, and the voltage control unit 53. Note that the printing process, applied voltage setting, and toner weight in the developing unit 23 in the image forming apparatus 100 are the same as those in the image forming apparatus 1 of the first embodiment, and thus the description thereof is omitted.

[2-3. Relationship between belt temperature when melting toner and external temperature when melting toner]
Here, the table of FIG. 15 shows the relationship between the belt temperature at the time of melting the toner and the external temperature detected by the external temperature sensor 101 at the time of melting the toner. This relationship was obtained as a result of an experiment. The experiment was performed when the toner weight in the developing device 23 was 40 g corresponding to the lower limit of T / L and 50 g corresponding to the lower limit of T / H. This is what I did at the time.

  As shown in FIG. 15, in the image forming apparatus 100, it can be seen that the lower the external temperature, the higher the belt temperature at the time of melting the toner. Actually, when the external temperature decreases, the efficiency of heat dissipation in the image forming apparatus 100 is improved, so that the temperature of the developing unit 23 is difficult to increase. On the other hand, the transfer belt 4 in the vicinity of the internal temperature sensor 8 is adjacent to the fixing device 12 and is affected by heat generated by the fixing device 12 that fixes at a constant temperature regardless of the external temperature. A heat dissipation effect cannot be obtained. Therefore, as the external temperature decreases, the toner temperature in the developing device 23 is transmitted to the transfer belt 4 while slowly rising. For this reason, the temperature difference between the toner temperature in the developing unit 23 and the belt temperature becomes small, and as a result, the belt temperature at the time of melting the toner increases as the external temperature decreases. In consideration of this point, in the image forming apparatus 100, the printing speed is changed based on the belt temperature, the external temperature, and the remaining amount of toner so as not to melt the toner.

  In the image forming apparatus 100, the belt temperature obtained from the internal temperature sensor 8, the external temperature obtained from the external temperature sensor 101, and the four toner remaining amount detection units 33 provided in each of the developing units 3 </ b> A to 3 </ b> D. Based on the remaining amount of toner obtained from each, the printing speed is changed so that toner melting does not occur in all of the developing units 3A to 3D.

[2-4. Change in printing speed based on belt temperature, external temperature, and remaining toner]
Actually, in the image forming apparatus 100, as shown in the table of FIG. 16, the belt temperature condition (decelerated printing transition condition) at the time of shifting to the decelerating printing at T / L and T / H is shown. It is supposed to change.

  Further, in the image forming apparatus 100, the deceleration printing transition condition and the deceleration printing release are further determined depending on whether the external temperature is less than 25 ° C. or 25 ° C. or more at each of T / L and T / H. The conditions are to be changed. Note that, here, the threshold value as the third threshold value of the external temperature that becomes the deceleration printing transition condition is set to an average temperature of 25 ° C. as the environment temperature in which the image forming apparatus 1 is used. Instead, a value other than 25 ° C. may be set as the threshold value, or a plurality of threshold values such as 22 ° C. and 25 ° C. may be set. When a plurality of settings are made, for example, when the external temperature is less than 22 ° C., when the temperature is 22 ° C. or more and less than 25 ° C., or when the temperature is 25 ° C. or more, the deceleration printing transition condition and the deceleration printing release condition may be changed.

  Further, in the image forming apparatus 100, when the belt temperature is equal to or higher than the temperature of the deceleration printing transition condition, the deceleration printing is performed. After that, when the belt temperature becomes lower than the temperature of the deceleration printing cancellation condition, the normal printing is returned from the deceleration printing. However, since the deceleration printing and the normal printing are the same as those of the image forming apparatus 1 of the first embodiment, the description thereof is omitted.

[2-5. Printing speed setting process]
Here, the procedure of the process of setting the printing speed by changing the setting of the linear speed of the photosensitive drum 20 (printing speed setting process) will be described in detail with reference to the flowcharts shown in FIGS. Note that the print processing procedure for printing at the set print speed is the same as that in the first embodiment, and a description thereof will be omitted.

  For example, when the power of the image forming apparatus 100 is turned on or when the image forming apparatus 100 is returned from the sleep mode to the operation mode, the control unit 50 of the image forming apparatus 100 starts the printing speed setting process and proceeds to step SP100. At this time, it is assumed that the setting of the linear velocity of the photosensitive drum 20 is an initial value (for example, 310 mm / sec).

  In step SP100, the control unit 50 detects the remaining amount of toner with the toner remaining amount detecting unit 33 at a predetermined timing, and proceeds to the next step SP101. In step SP101, the control unit 50 determines which of T / H, T / L, and T / E is the state obtained as a detection result of the remaining toner amount detection unit 33. The control unit 50 determines the state based on the detection result of the least remaining toner amount among the detection results of the remaining toner amount detection units 33 of the developing units 3A to 3D.

  Here, when the detection result of the toner remaining amount detecting unit 33 is T / E (the remaining amount of toner is less than 40 g), the control unit 50 moves to step SP102 and warns to replace the toner cartridge 34. Is displayed and the printing speed setting process is terminated. On the other hand, when the detection result of the toner remaining amount detection unit 33 is T / H (the remaining amount of toner is 50 g or more), the control unit 50 moves to step SP103 and the external temperature sensor 101 at this time It is determined whether or not the detection result (external temperature) is 25 ° C. or higher. Here, when the external temperature is not 25 ° C. or higher and a negative result is obtained in step SP103, the control unit 50 proceeds to step SP104.

  In step SP104, the control unit 50 determines whether or not the detection result (belt temperature) of the internal temperature sensor 8 is 49 ° C. or higher. Here, if a negative result is obtained in step SP104 because the belt temperature is not 49 ° C. or higher, this means that the toner does not melt at this time. At this time, the control unit 50 returns to step SP100 without changing the setting of the linear velocity of the photosensitive drum 20 from the initial value. As a result, the image forming apparatus 100 performs normal printing with a printing speed higher than that during decelerating printing.

  On the other hand, if the belt temperature is 49 ° C. or higher and an affirmative result is obtained in this step SP104, this may cause toner melting, and it is necessary to lower the printing speed and lower the toner temperature. It means that there is. At this time, the control unit 50 moves to step SP105, sets the drive of the drum motor 54 so as to change the linear speed setting of the photosensitive drum 20 to 210 mm / sec corresponding to the deceleration printing, and performs step SP109 (FIG. Move to 18). As a result, the image forming apparatus 100 performs decelerated printing at a lower printing speed than during normal printing.

  On the other hand, if the external temperature is 25 ° C. or higher and an affirmative result is obtained in step SP103, the control unit 50 proceeds to step SP106. In step SP106, the control unit 50 determines whether or not the detection result (belt temperature) of the internal temperature sensor 8 is 47 ° C. or higher. Here, if a negative result is obtained in step SP106 because the belt temperature is not 47 ° C. or higher, this means that the toner does not melt at this time. At this time, the control unit 50 returns to step SP100 without changing the setting of the linear velocity of the photosensitive drum 20 from the initial value.

  On the other hand, if the belt temperature is 47 ° C. or higher and an affirmative result is obtained in this step SP106, this may cause toner melting, and it is necessary to reduce the printing speed and lower the toner temperature. It means that there is. At this time, the control unit 50 moves to step SP105, sets the drive of the drum motor 54 so as to change the linear speed setting of the photosensitive drum 20 to 210 mm / sec corresponding to the deceleration printing, and performs step SP109 (FIG. Move to 18).

  If the detection result of the remaining toner amount detection unit 33 is T / L (the remaining toner amount is 40 g or more and less than 50 g), the control unit 50 moves from step SP101 to step SP107, and the external temperature sensor at this time It is determined whether or not the detection result (external temperature) 101 is 25 ° C. or higher. Here, if the external temperature is not 25 ° C. or higher, and if a negative result is obtained in step SP107, the control unit 50 proceeds to step SP106. The processing after step SP106 is as described above.

  Further, when the external temperature is 25 ° C. or higher and the control unit 50 obtains a positive result in step SP107, the control unit 50 proceeds to step SP108. In step SP108, the control unit 50 determines whether or not the detection result (belt temperature) of the internal temperature sensor 8 is 45 ° C. or higher. Here, if a negative result is obtained in this step SP108 because the belt temperature is not 45 ° C. or higher, this means that the toner does not melt at this time. At this time, the control unit 50 returns to step SP100 without changing the setting of the linear velocity of the photosensitive drum 20 from the initial value.

  On the other hand, if the belt temperature is 45 ° C. or higher and an affirmative result is obtained in this step SP108, this may cause toner melting, and it is necessary to reduce the printing speed and lower the toner temperature. It means that there is. At this time, the control unit 50 moves to step SP105, sets the drive of the drum motor 54 so as to change the linear speed setting of the photosensitive drum 20 to 210 mm / sec corresponding to the deceleration printing, and performs step SP109 (FIG. Move to 18).

  In step SP109 shown in FIG. 18, the control unit 50 detects the remaining amount of toner by the toner remaining amount detecting unit 33 again at a predetermined timing, and proceeds to the next step SP110. In step SP110, the control unit 50 determines whether or not the state obtained as a detection result of the toner remaining amount detection unit 33 is T / E. Here, if the detection result of the toner remaining amount detecting unit 33 is T / E (the remaining amount of toner is less than 40 g) and an affirmative result is obtained in step SP110, the control unit 50 proceeds to step SP111, and the toner A warning to replace the cartridge 34 is displayed, and the printing speed setting process is terminated.

  On the other hand, if the result of detection by the toner remaining amount detecting unit 33 is not T / E (the remaining amount of toner is less than 40 g) and a negative result is obtained in step SP110, the control unit 50 proceeds to step SP112. In step SP112, the control unit 50 determines whether or not the detection result (external temperature) of the external temperature sensor 101 at this time is 25 ° C. or higher. Here, if the external temperature is not 25 ° C. or higher, and if a negative result is obtained in step SP112, the control unit 50 proceeds to step SP113.

  In step SP113, the control unit 50 determines whether or not the detection result (belt temperature) of the internal temperature sensor 8 is less than 45 ° C. Here, if a negative result is obtained in step SP113 because the belt temperature is not lower than 45 ° C., this means that the belt temperature has not dropped to a temperature sufficient for normal printing (that is, the temperature of the toner is low). Is not lowered enough). At this time, the control unit 50 returns to step SP109 without changing the setting of the linear velocity of the photosensitive drum 20 from 210 mm / sec.

  On the other hand, if an affirmative result is obtained in step SP113 because the belt temperature is less than 45 ° C., this means that the belt temperature has dropped to a temperature sufficient for normal printing (ie, the toner temperature is sufficient). It means) At this time, the control unit 50 proceeds to step SP114, performs drive setting of the drum motor 54 so as to return the linear velocity setting of the photosensitive drum 20 to the initial value corresponding to normal printing, and proceeds to step SP100 (FIG. 17). Return.

  Further, when the external temperature is 25 ° C. or higher and the control unit 50 obtains a positive result in step SP112, the control unit 50 proceeds to step SP115. In step SP115, the control unit 50 determines whether or not the detection result (belt temperature) of the internal temperature sensor 8 at this time is less than 43 ° C. Here, if a negative result is obtained in step SP115 because the belt temperature is not less than 43 ° C., this means that the belt temperature has not dropped to a temperature sufficient for normal printing (that is, the temperature of the toner is low). Is not lowered enough). At this time, the control unit 50 returns to step SP109 without changing the setting of the linear velocity of the photosensitive drum 20 from 210 mm / sec.

  On the other hand, if an affirmative result is obtained in this step SP115 because the belt temperature is less than 43 ° C., this means that the belt temperature has dropped to a temperature sufficient for normal printing (ie, the toner temperature is sufficient). It means) At this time, the control unit 50 proceeds to step SP114, performs drive setting of the drum motor 54 so as to return the linear velocity setting of the photosensitive drum 20 to the initial value corresponding to normal printing, and proceeds to step SP100 (FIG. 17). Return. Based on such a printing speed setting process, the image forming apparatus 100 changes the setting of the linear speed of the photosensitive drum 20 to set the printing speed.

[2-6. Effects of the second embodiment]
As described above, in the image forming apparatus 100, in addition to changing the belt temperature condition (decelerated printing transition condition) for shifting to the deceleration printing between T / L and T / H, T The deceleration printing transition condition and the deceleration printing release condition are changed according to the external temperature at each of / L and T / H. That is, in the image forming apparatus 100, based on the phenomenon that as the toner remaining amount increases, the melting does not easily occur even if the toner temperature rises, the speed printing at T / H is slower than the time at T / L. Based on the phenomenon that the belt temperature is set to a high threshold value as a transition condition, and the toner temperature is more difficult to melt as the external temperature is lower at T / L and T / H. The belt temperature threshold value that is the decelerating printing transition condition and the belt temperature threshold value that is the decelerating printing release condition are set higher when the temperature is higher than or equal to ℃ than when it is lower than 25 ° C.

  By doing so, in the image forming apparatus 100, for example, compared with the image forming apparatus 1, it is possible to further reduce the opportunities for performing the decelerated printing and increase the opportunities for performing the high-speed normal printing. Thus, the image forming apparatus 100 can perform printing at a higher speed.

[3. Other Embodiments]
[3-1. Other Embodiment 1]
In the first embodiment described above, the remaining toner amount in the developing unit 23 is detected at the rotation period of the remaining toner amount detection unit 33, and the deceleration printing transition condition is changed according to the remaining toner amount. did. For example, the remaining amount of toner is estimated based on information related to the remaining amount of toner, such as the total number of printed sheets, the total number of rotations of the photosensitive drum 20, the amount of toner consumption, and the total number of light emission of the LED head 22. Then, the deceleration printing transition condition may be changed according to the estimated remaining toner amount.

  Further, instead of the remaining amount of toner, information such as the total number of printed sheets, the total number of rotations of the photosensitive drum 20, the amount of toner consumption, and the total number of light emission of the LED head 22 may be used to change the conditions after the deceleration printing. . The same applies to the second embodiment.

[3-2. Other Embodiment 2]
In the first and second embodiments described above, the internal temperature sensor 8 is provided on the lower side of the transfer belt 4 in the vicinity of the fixing device 12, and the surface temperature of the transfer belt 4 (belt) is detected by the internal temperature sensor 8. Temperature) was measured as the internal temperature. For example, as shown in FIG. 19, an internal temperature sensor 8 is provided in the photosensitive drum 20 closer to the developing unit 23 that generates heat that causes melting of the toner than the transfer belt 4. The internal temperature sensor 8 may measure the surface temperature of the photosensitive drum 20 (referred to as drum temperature) and use this instead of the belt temperature.

  In this case, the relationship between the toner weight in the developing device 23 and the drum temperature at the time of melting the toner is obtained through an experiment, and the drum temperature condition when shifting to the deceleration printing according to the toner weight based on this relationship. You can change it. Although not shown, an internal temperature sensor 8 that is not in contact with the photosensitive drum 20 is provided in the vicinity of the photosensitive drum 20, the ambient temperature around the photosensitive drum 20 is measured by the internal temperature sensor 8, and this is detected as the belt temperature. It may be used instead of. Further, although not shown, an internal temperature sensor 8 is provided so as to come into contact with the end of the photosensitive drum 20 (a portion not used for forming the latent image pattern), and the surface temperature of the photosensitive drum 20 (drum temperature) is provided by the internal temperature sensor 8. ) May be measured and used in place of the belt temperature.

  Further, although not limited to this, although not shown, the internal temperature sensor 8 is provided in the vicinity of the developing roller 30, in the vicinity of the regulating blade 32, in the vicinity of the transfer roller 24, and the surface of the developing roller 30 by the internal temperature sensor 8. The temperature, the surface temperature of the regulating blade 32, the surface temperature of the transfer roller 24, and the like may be measured and used instead of the belt temperature. That is, the location where the temperature is measured by the internal temperature sensor 8 may be a location where the temperature changes due to heat generated by the developing device 23 that causes melting of the toner. In the image forming apparatuses 1 and 100, the transfer belt 4, the drive roller 5, the idle roller 6, the transfer roller 24, and the like are detachable from the image forming apparatuses 1 and 100 as one belt unit. Therefore, in the image forming apparatus 1, the cost of the belt unit itself is reduced by providing the internal temperature sensor 8 outside the belt unit.

  In the image forming apparatuses 1 and 100, the developing units 3 </ b> A to 3 </ b> D are also detachable from the image forming apparatus 1 by being separated from the transfer roller 24 that is a part of the belt unit. Therefore, in consideration of the costs of the developing units 3A to 3D, it is desirable to provide the internal temperature sensor 8 outside the developing units 3A to 3D as in the image forming apparatus 1.

  On the other hand, the present invention can also be applied to a monochrome image forming apparatus having only one developing unit. For example, as shown in FIG. 20, the monochrome image forming apparatus does not include the transfer belt 4, and conveys the recording medium P (not shown) using only the photosensitive drum 20 and the transfer roller 24. In such a monochrome image forming apparatus, the internal temperature sensor 8 may be provided outside the detachable developing unit 3. For example, as shown in FIG. 20, the transfer roller 24 is located near the transfer roller 24. A non-contact internal temperature sensor 8 may be provided, and the internal temperature sensor 8 may be used to measure the ambient temperature around the transfer roller 24 and use this instead of the belt temperature.

  The same applies to the external temperature sensor 101 of the image forming apparatus 100, and it is desirable to provide the external temperature sensor 101 outside the developing units 3 </ b> A to 3 </ b> D and the belt unit. It is like that.

[3-3. Other Embodiment 3]
Furthermore, in the first and second embodiments described above, normal printing and decelerated printing are switched by changing the rotational speed of the drum motor 54 and changing the linear speed of the photosensitive drum 20. However, the present invention is not limited to this, and normal printing and deceleration printing may be switched by changing the linear speed of the developing roller 30 related to the printing speed, the traveling speed of the transfer belt 4, and the like.

  In this case, similarly to the photosensitive drum 20, the linear speed at the time of decelerating printing is set from the relationship between the linear speed of the developing roller 30 and the maximum value of the belt temperature, or the running speed of the transfer belt 4 and the maximum of the belt temperature are set. From the relationship with the value, the traveling speed at the time of decelerating printing may be set. In order to change the setting of the linear speed of the developing roller 30, it is only necessary to change the setting of the rotational speed of the drum motor 54 as in the case of the photosensitive drum 20, and to change the setting of the running speed of the transfer belt 4. The rotation speed of the drive roller 5 that causes the transfer belt 4 to travel may be changed.

[3-4. Other Embodiment 4]
Further, in the first and second embodiments described above, the present invention is applied to the image forming apparatuses 1 and 100 having a configuration of an electrophotographic color printer. Any device having a function of detecting (for example, belt temperature) can be applied to an image forming apparatus such as a facsimile, an MFP (Multi Function Product), and a copier.

[3-5. Other Embodiment 5]
Furthermore, in the first and second embodiments described above, the photosensitive drum 20 is used as a specific example of the image carrier that carries the latent image. However, the present invention is not limited to this, and a part that is different from the photosensitive drum 20 such as a belt-like image carrier may be used as long as it functions as an image carrier. Furthermore, in the first and second embodiments described above, the developing roller 30 is used as a specific example of the developer carrying member that carries the developer for developing the latent image. However, the present invention is not limited to this, and a part different from the developing roller 30 may be used as long as it functions as a developer carrier.

  Furthermore, in the first and second embodiments described above, the transfer belt 4, the drive roller 5, the idle roller 6, and the transfer roller 24 are used as specific examples of the transfer unit that transfers the developer image to the recording medium. did. Not limited to this, as long as it functions as a transfer portion, a component different from these may be used. Furthermore, in the first and second embodiments described above, the toner remaining amount detection unit 33 is used as a specific example of the developer amount detection unit that detects the developer amount in the developing device. The present invention is not limited to this, and a component different from the toner remaining amount detection unit 33 may be used as long as the toner remaining amount in the developing device can be detected directly or indirectly.

  Furthermore, in the first and second embodiments described above, the drum motor 54 and the belt motor 55 are used as specific examples of the drive unit that operates at least one of the image carrier, the developer carrier, and the transfer unit. I made it. Not limited to this, as long as it functions as a drive unit, a component different from these may be used. Furthermore, in the first and second embodiments described above, the internal temperature sensor 8 is used as a specific example of the temperature detection unit that detects the temperature of the device and the internal temperature detection unit that detects the temperature inside the device. I made it. Not limited to this, as long as it functions as a temperature detection unit and an internal temperature detection unit, components different from the internal temperature sensor 8 may be used.

  Furthermore, in the above-described second embodiment, the external temperature sensor 101 is used as a specific example of the external temperature detection unit that detects the temperature around the apparatus. Not limited to this, as long as it functions as an external temperature detector, a component different from the external temperature sensor 101 may be used. Further, in the first and second embodiments described above, the regulating blade 32 is used as a specific example of the regulating member that regulates the layer thickness of the developer carried on the developer carrying body. Not limited to this, as long as it functions as a regulating member, a part different from the regulating blade 32 may be used.

[3-6. Other Embodiment 6]
Furthermore, the present invention is not limited to the first and second embodiments described above and the other embodiments described above. That is, the present invention is also applicable to an embodiment in which a part or all of the first and second embodiments described above and the other embodiments described above are arbitrarily combined, or an embodiment in which a part is extracted. The scope of application extends.

  The present invention can be widely used in laser or LED color printers.

  DESCRIPTION OF SYMBOLS 1,100 ... Image forming apparatus, 2 ... Housing | casing 3, 3A, 3B, 3C, 3D ... Developing unit, 4 ... Transfer belt, 5 ... Drive roller, 8 ... Internal temperature sensor, 20 ... ... Photosensitive drum, 23... Developer, 23 A .. Opening, 24 .. Transfer roller, 30... Development roller, 32 .. Restricting blade, 33. ... drum motor, 55 ... belt motor, 101 ... external temperature sensor, P ... recording medium.

Claims (15)

An image carrier for carrying a latent image;
A developer carrying member carrying a developer for developing the latent image;
A transfer section for transferring a developer image obtained by developing a latent image of the image carrier to a recording medium;
A developer containing a developer to be supplied to the developer carrier;
A developer amount detector for detecting the amount of developer in the developing unit;
A drive unit that operates at least one of the image carrier, the development carrier, and the transfer unit;
A temperature detector for detecting the temperature of the device;
An image forming apparatus comprising: a control unit configured to perform drive setting of the drive unit based on a detection result of the developer amount detection unit and a detection result of the temperature detection unit. The temperature detector is
The image forming apparatus according to claim 1, wherein a temperature inside the apparatus is detected. The controller is
When the temperature detected by the temperature detection unit is equal to or higher than a first threshold, drive setting of the driving unit is performed so that the driving unit is driven at a low driving speed slower than a normal driving speed,
Further, when the developer amount detected by the developer amount detection unit is less than a predetermined amount, the first amount is higher than when the developer amount detected by the developer amount detection unit is not less than the predetermined amount. The image forming apparatus according to claim 2, wherein a threshold value of the image forming apparatus is lowered. The controller is
When the temperature detected by the temperature detection unit becomes less than a second threshold value that is lower than the first threshold value, the driving unit is configured to drive the driving unit at the normal speed that is higher than the low driving speed. The image forming apparatus according to claim 3, wherein drive setting is performed. The controller is
When the temperature detected by the temperature detection unit is equal to or higher than a first threshold, drive setting of the driving unit is performed so that the driving unit is driven at a low driving speed slower than a normal driving speed,
Further, when the developer amount detected by the developer amount detection unit is greater than or equal to a predetermined amount, the predetermined amount is greater than when the developer amount detected by the developer amount detection unit is less than the predetermined amount. The image forming apparatus according to claim 2, wherein the threshold value is increased. The temperature detector is
An internal temperature detector for detecting the internal temperature of the device;
It consists of an external temperature detector that detects the temperature around the device,
The controller is
5. The image forming apparatus according to claim 4, wherein the driving unit is set based on a detection result of the developer amount detection unit, a detection result of the internal temperature detection unit, and a detection result of the external temperature detection unit. . The controller is
When the temperature detected by the external temperature detection unit is equal to or higher than a third threshold value, the first threshold value is set lower than when the temperature detected by the external temperature detection unit is lower than the third threshold value. The image forming apparatus according to claim 5. The controller is
When the temperature detected by the external temperature detector is less than a third threshold, the first threshold is set higher than when the temperature detected by the external temperature detector is equal to or higher than the third threshold. The image forming apparatus according to claim 5. The temperature detector is
The image forming apparatus according to claim 2, wherein the temperature of the transfer unit is detected. The temperature detector is
The image forming apparatus according to claim 2, wherein a surface temperature of the transfer unit is detected. The temperature detector is
The image forming apparatus according to claim 2, wherein an ambient temperature around the transfer unit is detected. The temperature detector is
The image forming apparatus according to claim 2, wherein the temperature of the image carrier is detected. The developer carrier is
Provided in the developing unit,
The developer is
An opening is provided at the top, and the developer is replenished from the outside through the opening,
The developer amount detector
The image forming apparatus according to claim 1, wherein the image forming apparatus is provided between the opening in the developing unit and the developer carrier. The image forming apparatus according to claim 1, further comprising a regulating member that abuts on the developer carrying member and regulates a layer thickness of the developer carried on the developer carrying member. An image carrier for carrying a latent image;
A developer carrying member carrying a developer for developing the latent image;
A transfer section for transferring a developer image obtained by developing a latent image of the image carrier to a recording medium;
A developer containing a developer to be supplied to the developer carrier;
A developer amount detector for detecting the amount of developer in the developing unit;
A drive unit that operates at least one of the image carrier, the development carrier, and the transfer unit;
When it is determined in the detection result of the developer amount detection unit that the developer amount is less than the predetermined amount, the drive speed of the drive unit is reduced more than the drive speed when the developer amount is equal to or greater than the predetermined amount. An image forming apparatus comprising: a control unit that performs control.

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