JP4339281B2 - Development device - Google Patents

Description

  The present invention relates to a developing device mounted on an image forming apparatus such as a printer or a copying machine that forms an image on recording paper by an electrophotographic process.

  2. Description of the Related Art Conventionally, image forming apparatuses such as copying machines, printers, and facsimiles uniformly charge the surface of a photosensitive drum with a charger, and an electrostatic latent image corresponding to the read document image is exposed with the photosensitive drum. In addition, the developer is developed by attaching a charged developer to the portion of the electrostatic latent image by the developing device, and the image is transferred to the recording paper by the transfer device, thereby forming the original image on the recording paper. The so-called electrophotographic system is employed.

In an image forming apparatus that employs this electrophotographic system, Japanese Patent Application Laid-Open No. 2004-228561 includes a plurality of developer chambers that contain a developer in series, and one of the developer chambers includes a stirring mechanism that stirs the developer. A vessel is disclosed.
JP-A-63-83760

  In order to ensure the fluidity of the developer and to smoothly supply the developer from the storage chamber for storing the developer, the developer is agitated. However, this stirring operation has a problem that the charging ability of the developer is lowered. Therefore, in order to ensure the charging ability of the developer, it is desirable to avoid the stirring operation as much as possible.

  In Patent Document 1, since the developer stirring mechanism is not provided in each developer chamber, the fluidity of the developer in the developer chamber not provided with the stirring mechanism is reduced. As a result, the developer supply amount to the developing unit is insufficient even though the developer remains in the developer chamber, or the developer in the developer chamber is likely to be adversely affected by heat. Is done.

  The present invention has been made in view of the above circumstances, and is capable of achieving both the securing of the developer fluidity and the suppression of the decrease in charging capability, and the development capable of preventing or suppressing the decrease in image quality as much as possible. An object is to provide an apparatus.

  The invention according to claim 1 is a developing device comprising developing means for developing an electrostatic latent image formed on an image carrier with a developer, the developing device having a plurality of developer storage chambers, The developer accommodating means configured to be able to supply the developer to the developing means alternatively from the developer accommodating chambers, and installed in each developer accommodating chamber, and each of them is independently stirred. A plurality of possible developer agitating means and a setting means for setting the developer agitating means corresponding to the developer storage chamber selected as a developer supply source to the developing means as a target to perform the agitating operation And a time detecting means for detecting a stirring operation time of the developer stirring means, and when a predetermined time is detected by the detecting means, the developer supply source to the developing means is switched to another developer storage chamber. Switching means, and the setting means includes the switching means. The developer stirring means corresponding to the other developer storage chamber switched as a developer supply source to the developing means by the means is set as an object to perform the stirring operation. .

  According to this invention, when the stirring operation time of the developer stirring means or the time related to the stirring operation time reaches a predetermined time, the developer supply source to the developing means is switched to another developer storage chamber, Since the developer stirring means corresponding to the other developer storage chamber is set as an object for performing the stirring operation, the developer stirring time can be minimized.

  According to a second aspect of the present invention, in the developing device according to the first aspect, the developer storage means is configured to be rotatable about a predetermined rotation axis by a driving means, and a plurality of the developer storage means are arranged in the rotation direction. The developer storage chamber is formed by dividing the developer supply chamber into the other developer storage using the rotation operation of the developer storage means. It is characterized by switching to a room.

  According to this invention, the structure which switches the supply source of the developer to a developing means to another developer storage chamber is realizable with a comparatively simple structure.

A third aspect of the present invention is the development apparatus according to the first or second aspect, further comprising temperature detection means for detecting an environmental temperature of the development apparatus, wherein the switching means is a temperature detected by the temperature detection means. The higher the value is, the shorter the predetermined time is set.

According to the present invention, the predetermined time is set to be shorter as the temperature detected by the temperature detecting means is higher . Therefore, even if the environmental temperature of the developing device, that is, the temperature of the developer changes, the development is continued. The required fluidity of the agent can be ensured.

According to a fourth aspect of the present invention, in the developing device according to any one of the first to third aspects, the apparatus includes a developer amount detecting unit that detects a developer amount in the developer storage chamber, and the switching unit includes the switching unit, The predetermined time is set shorter as the developer amount detected by the developer amount detecting means is larger .

According to the present invention, the predetermined time is set shorter as the developer amount detected by the developer amount detecting means is larger . Therefore, regardless of the amount of developer in the developer storage chamber, the developer The necessary fluidity can be secured.

According to a fifth aspect of the present invention, in the developing device according to any one of the first to fourth aspects, the developer agitating unit has a developer storage chamber corresponding to the developer agitating unit. When the intermittent stirring operation is performed when the developer supply source is selected, the switching unit sets the predetermined time longer as the developer stirring unit stops longer. is there.

  According to the present invention, when the developer is overcharged, if the developer is left without being stirred, the developer returns from the overcharged state to the normal charged state. In the case where the intermittent stirring operation is performed, especially when the stop period of the developer stirring unit is short, the time until the developer supply source to the developing unit is switched to another developer storage chamber (the predetermined time). ) Is relatively shorter than when the stop period is long, so that a decrease in charging ability can be suppressed.

  According to a sixth aspect of the present invention, in the developing device according to any one of the first to fifth aspects, the time detecting unit detects a continuous stirring operation time of the developer stirring unit. To do.

  According to the present invention, the time detection means detects the continuous stirring operation time of the developer stirring means. Therefore, when the developer stirring means performs an intermittent stirring operation, By setting the time until the developer supply source is switched to another developer storage chamber (predetermined time) according to the length of the continuous stirring operation time, it is possible to suppress a decrease in the charging ability of the developer. Can do.

  According to a seventh aspect of the present invention, in the developing device according to any one of the first to sixth aspects, the developing device further includes a developing roller for transferring a developer to the image carrier, and the time detection unit is configured to perform the development. The driving time for driving the roller is detected as the stirring operation time of the developer stirring means.

  According to the present invention, since the driving time for driving the developing roller is detected as the stirring operation time of the developer stirring unit, the configuration for detecting the stirring operation time of the developer stirring unit is relatively simple. Can be realized.

  According to an eighth aspect of the present invention, in the developing device according to any one of the first to seventh aspects, the time detection unit determines a drive time for driving the image carrier, and a stirring operation time of the developer stirring unit. It is characterized by detecting as.

  According to the present invention, since the drive time for driving the image carrier is detected as the stirring operation time of the developer stirring means, the configuration for detecting the stirring operation time of the developer stirring means is relatively simple. It can be realized with a configuration.

  According to the present invention, the developer agitation time can be suppressed to a necessary minimum, so that both the ensuring of the developer fluidity and the suppression of the decrease in charging ability can be achieved.

  An embodiment of a developing device according to the present invention will be described. FIG. 1 is a diagram illustrating a configuration of the first embodiment of the developing device.

  As shown in FIG. 1, the developing device 1 includes a container 2, a first driving unit 3, a second driving unit 4, a developing device 5, a third driving unit 6, a fourth driving unit 7, and a control. The electrostatic latent image formed on the surface of the photosensitive drum D is developed with toner.

  The container 2 is a member formed in a circular cross section, and is configured to be rotatable about the cross sectional center O as a rotation center. The inside of the container 2 is divided into a plurality in the circumferential direction, and toner is stored in each toner storage chamber 2a formed by the division. This toner is an example of the developer in the claims. An opening 9a is formed at an appropriate position of a hopper 9 to be described later of the developing device 5, and the container 2 is configured such that the toner storage chamber 2a selectively opposes the opening 9a. The toner can be supplied to the hopper 9 only through the section 9a. The container 2 is an example of the developer storage means in the claims, and the toner storage chamber 2a corresponds to the developer storage chamber in the claims.

  Each toner storage chamber 2a is provided with a stirring member 15 for stirring the toner in the storage chamber 2a, and each stirring member 15 is configured to be independently rotatable. The stirring member 15 constitutes the developer stirring means in the claims.

  The 1st drive part 3 rotates the said container 2 centering | focusing on the said rotation center O, and is provided with the motor. The driving operation by the first driving unit 3 is controlled by the control unit 8 described later. The second drive unit 4 drives the stirring member 15 installed in each toner storage chamber 2a to rotate about the rotation centers a to d.

  The developing device 5 includes a hopper 9, a mixer 10, a developing roller 11, and a developing blade 12. The hopper 9 temporarily stores the toner supplied from the container 2 so as to be supplied to the developing roller 11. The mixer 10 is installed at an appropriate position in the hopper 9 and agitates the toner in the hopper 9.

  The developing roller 11 has a magnet inside, forms a magnetic brush on the surface, and slides the magnetic brush on the surface of the photosensitive drum D to attach toner to the electrostatic latent image portion of the photosensitive drum D. Is. The developing blade 12 removes excess toner adhering to the surface of the developing roller 11 when the toner layer formed on the developing roller 11 passes through the installation position of the developing blade 12.

  The third drive unit 6 rotates the developing roller 11, and the fourth drive unit 7 rotates the mixer 10.

  The control unit 8 includes a storage unit (not shown) that stores a control program for controlling the operation of the developing device 1, a microcomputer that reads the control program and the like from the storage unit, and executes the program. Further, in the present embodiment, as shown in FIG. 1, the control unit 8 functionally includes the first drive control unit 13 and the agitation operation in consideration of the fluidity and charging ability of the toner. And a second drive control unit 14.

  The first drive control unit 13 controls the drive operation of the second drive unit 4 that rotationally drives each stirring member 15. In the present embodiment, the toner storage chamber 2 a that faces the opening 9 a of the hopper 9. The inner stirring member 15 is always operated until the container 2 is driven to rotate next time, and the stirring operation by the other stirring members 15 in the toner storage chamber 2a is stopped. The 1st drive control part 13 is an example of the setting means in a claim.

  The second drive control unit 14 controls the drive operation of the first drive unit 3 that rotationally drives the container 2. The second drive control unit 14 measures the drive time of the second drive unit 4 with respect to the stirring member 15 in the toner storage chamber 2a facing the opening 9a of the hopper 9 by using a timer (not shown). When the measurement time reaches a predetermined time, the toner storage chamber 2a that is opposed to the opening 9a of the hopper 9 with respect to the first drive unit 3 is changed to the toner storage chamber 2a that is currently opposed to the opening 9a of the hopper 9. To the adjacent toner storage chamber 2a. Hereinafter, the predetermined time is referred to as a stirring limit time.

  The agitation limit time for determining the switching timing of the toner storage chamber 2a is set as follows, for example.

  The characteristics of an example of toner used in the developing device 1 will be described. FIG. 2 is a diagram illustrating a relationship between an AD value (a numerical value indicating the fluidity of toner) and a ΔID value for an example of toner used in the developing device 1, and FIG. It is a figure which shows the relationship with a value.

  As shown in FIG. 2, the ΔID value of the toner is a difference from a necessary toner density, and when the AD value is “0.50” or more, the ΔID value provides a necessary toner density. It takes a value of 0.0 and decreases relatively rapidly as the AD value decreases from “0.50”. Therefore, it can be seen that the AD value for obtaining the necessary toner concentration is 0.5 or more.

  Further, as shown in FIG. 3, the AD value of the toner has a characteristic of decreasing substantially linearly as the stirring time of the toner becomes longer. Therefore, as described above, it is understood that the stirring time must be set within 2 hours in order to make the AD value 0.5 or more. Hereinafter, this stirring limit time is referred to.

  Therefore, in this example, the stirring limit time is set to 2 hours. When the toner storage chamber 2a is switched, the timer is reset. The second drive control unit 14 and the timer are an example of a switching unit and a detection unit in the claims.

  FIG. 4 is a flowchart showing the stirring operation in the developing device 1.

  As shown in FIG. 4, when the control unit 8 switches the toner storage chamber 2a facing the opening 9a of the hopper 9 from the current toner storage chamber 2a to the adjacent toner storage chamber 2a (step # 1), Only the stirring member 15 in the toner storage chamber 2a newly facing the opening 9a is actuated (step # 2), and time is measured by the timer (step # 3).

  Then, the control unit 8 determines whether or not the power to the developing device 1 is turned off (step # 4). If the power is not turned off (NO in step # 4), the timer measurement time is determined. It is determined whether or not the stirring limit time has been reached (step # 5). As a result, if the measured time has not reached the stirring limit time (NO in step # 5), the process returns to step # 2, while if the measured time has reached the stirring limit time (step Returning to the processing of step # 1, the toner storage chamber 2a facing the opening 9a of the hopper 9 is switched from the current toner storage chamber 2a to the toner storage chamber 2a adjacent thereto. Then, when the power to the developing device 1 is turned off (YES in step # 4), the control unit 8 ends the series of processes.

  As described above, only the stirring member 15 in the toner storage chamber 2a facing the opening 9a of the hopper 9 is operated, and the stirring operation of the other stirring members 15 in the toner storage chamber 2a is stopped. As compared with the case where the stirring member 15 in each toner storage chamber 2a is always operated during the period when the power is supplied to the developing device 1, it is possible to suppress a decrease in toner charging ability. In addition, a decrease in fluidity can be significantly suppressed as compared with the case where no stirring operation is performed.

  As a result, it is possible to achieve both of ensuring the fluidity of the toner and suppressing the decrease in charging ability, and preventing or suppressing the decrease in image quality.

  In addition, the container 2 is configured to be rotatable, the interior thereof is divided into a plurality of circumferentially circumferential portions to form a plurality of toner storage chambers 2 a, and the toner storage chamber that supplies toner to the hopper 9 by the rotation operation of the container 2. Since 2a is alternatively selected, a configuration for alternatively selecting the toner storage chamber 2a for supplying toner to the hopper 9 can be configured relatively easily.

  In addition to the said embodiment, it can replace with the said embodiment, and the deformation | transformation form demonstrated to following form [1]-[5] is also employable for this invention.

  [1] It is known that the AD value (“0.50” in the example shown in FIG. 3) at which the fluidity of the toner starts to change varies depending on the temperature of the toner. When the AD value changes, the stirring limit time of the stirring member 15 that can ensure the required fluidity also changes, so that the hopper 9 can be selected according to the environmental temperature of the developing device 1 that affects the toner temperature. The timing of the switching operation of the toner storage chamber 2a facing the opening 9a may be set.

  For example, a sensor for detecting the environmental temperature of the developing device 1 is installed at an appropriate place, and the stirring limit time corresponding to the environmental temperature is set in advance as a table, for example. When the environmental temperature is detected by the sensor, A mode in which the stirring limit time corresponding to the ambient temperature is derived with reference to the table, and the switching operation of the toner storage chamber 2a facing the opening 9a of the hopper 9 is set to the elapsed timing of the derived stirring limit time. Is assumed. For example, the higher the ambient temperature, the shorter the stirring limit time.

  [2] When the agitation operation is performed with a constant agitation time, it is considered that the greater the amount of toner stored in the toner storage chamber 2a, the lower the toner fluidity. The timing of the switching operation of the toner storage chamber 2a facing the opening 9a of the hopper 9 may be set according to the amount of stored toner.

  For example, when a sensor for detecting the amount of toner in the toner storage chamber 2a is installed at an appropriate place, the stirring limit time corresponding to the amount of toner is set in advance as a table, for example, and the amount of toner is detected by the sensor. Referring to the table, the stirring limit time corresponding to the toner amount is derived, and the switching operation of the toner storage chamber 2a facing the opening 9a of the hopper 9 is set to the elapsed timing of the derived stirring limit time. The form to do is assumed. For example, the stirring limit time may be shortened as the amount of toner in the toner storage chamber 2a increases.

  [3] In the first embodiment, the toner storage chamber 2a facing the opening 9a of the hopper 9 is changed from the toner storage chamber 2a facing the opening 9a of the hopper 9 to the adjacent toner storage chamber 2a. The switching timing is set to a timing at which the driving time of the second driving unit 4 with respect to the stirring member 15 in the toner storage chamber 2a facing the opening 9a of the hopper 9 reaches the stirring limit time, but is not limited thereto. Instead of the driving time of the second driving unit 4, the driving time of the third driving unit 6 that drives the developing roller 11 may be a timing at which the stirring limit time is reached, or the photosensitive drum D is driven. The driving time of the driving unit (not shown) may be the timing when the stirring limit time is reached.

  [4] In the first embodiment, the stirring member 15 in the toner storage chamber 2a facing the opening 9a of the hopper 9 is always operated until the container 2 is rotated. Alternatively, the stirring member 15 may be operated only during a period when the toner is transferred from the photosensitive drum D to the photosensitive drum D, or the stirring member 15 may be intermittently operated.

  Further, when the toner is overcharged, if the toner is left without being stirred, the toner returns from the overcharged state to the normal charged state, so that the toner is transferred from the developing roller 11 to the photosensitive drum D. In the configuration in which the stirring member 15 is operated only during the transition period or the stirring member 15 is operated intermittently, the stirring operation is performed on the toner in the toner storage chamber 2a facing the opening 9a of the hopper 9. Even when the toner storage chamber 2a facing the opening 9a of the hopper 9 is switched in accordance with the length of the leaving period during the period left without being performed (hereinafter referred to as the leaving period), Good.

  For example, while detecting the non-driving time of a driving unit (not shown) of the photosensitive drum D, a time (referred to as a threshold) that the toner is expected to return from the overcharged state to the normal charged state is set in advance. In addition, when the detected non-driving time exceeds the threshold value, it is assumed that the timing of the switching operation of the toner storage chamber 2a is extended by a predetermined time.

  [5] The developer in the present invention is not limited to a one-component developer composed only of toner, but also includes a two-component developer composed of toner and carrier.

1 is a diagram illustrating a configuration of a first embodiment of a developing device according to the present invention. FIG. 6 is a diagram illustrating a relationship between an AD value (a numerical value indicating toner fluidity) and a ΔID value for an example of toner employed in the developing device. It is a figure which shows an example of the relationship between stirring time and AD value. It is a flowchart which shows the stirring operation in a developing device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Developing apparatus 2 Container 2a Toner storage chamber 3 1st drive part 4 2nd drive part 5 Developer 8 Control part 13 1st drive control part 14 2nd drive control part 15 Stirring member

Claims (8)

A developing device comprising developing means for developing an electrostatic latent image formed on an image carrier with a developer,
A developer storage means having a plurality of developer storage chambers, and configured to be capable of supplying the developer to the developing means selectively from the plurality of developer storage chambers;
A plurality of developer stirring means installed in each developer storage chamber and capable of independently stirring operations;
Setting means for setting a developer stirring means corresponding to a developer storage chamber selected as a developer supply source to the developing means as a target to perform the stirring operation;
Time detection means for detecting the stirring operation time of the developer stirring means;
A switching means for switching a developer supply source to the developing means to another developer storage chamber when a predetermined time is detected by the detecting means;
The setting means sets the developer stirring means corresponding to the other developer storage chamber switched as the developer supply source to the developing means by the switching means as a target to perform the stirring operation. A developing device. The developer storage means is configured to be rotatable around a predetermined rotation axis by a driving means, and the developer storage chamber is formed by being divided into a plurality of parts in the rotation direction,
2. The developing device according to claim 1, wherein the switching unit switches a supply source of the developer to the developing unit to another developer storage chamber using a rotation operation of the developer storage unit. Temperature detecting means for detecting the environmental temperature of the developing device,
The developing device according to claim 1, wherein the switching unit sets the predetermined time to be shorter as the temperature detected by the temperature detection unit is higher . A developer amount detecting means for detecting the developer amount in the developer storage chamber;
4. The developing device according to claim 1, wherein the switching unit sets the predetermined time to be shorter as the developer amount detected by the developer amount detecting unit is larger . When the developer agitating means performs an intermittent agitation operation when the developer storage chamber corresponding to the developer agitating means is selected as a developer supply source to the developing means, the switching means the developing device according to any one of claims 1 to 4, characterized in that the stop period of the developer agitating means is set longer longer the predetermined time.   The developing device according to claim 1, wherein the time detection unit detects a continuous stirring operation time of the developer stirring unit. A developing roller for transferring the developer to the image carrier;
The developing device according to claim 1, wherein the time detection unit detects a driving time for driving the developing roller as a stirring operation time of the developer stirring unit.   The developing device according to claim 1, wherein the time detection unit detects a driving time for driving the image carrier as a stirring operation time of the developer stirring unit.

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