JP2004012652A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of attaining high quality printing by optimally stirring developer in accordance with the operating situation of the image forming apparatus and/or the amount of toner replenished into a developing unit during a printing operation. <P>SOLUTION: The image forming apparatus is provided with a stirring means for stirring the developer, a driving source for driving the stirring means, and a developer stirring speed control means for controlling the stirring speed of the stirring means in accordance with the state of the developing operation in the developing unit, the developer stirring speed is made high when the developing unit is in a non-developing state. Besides, when little amounts of toner are supplied, the developer is not stirred at a high speed, then, excessive stirring can be prevented. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electrophotographic or electrostatic recording type image forming apparatus. More specifically, the present invention relates to stirring of a developer in a developing device mounted on an image forming apparatus.
[0002]
[Prior art]
In a developing device of an image forming apparatus using an electrophotographic system or an electrostatic recording system, a two-component developer mainly containing toner particles and carrier particles is generally used. In the two-component developer, only toner particles are consumed at the time of development. Therefore, as the printing process proceeds, the toner concentration (mixing ratio of toner and carrier) in the developing device changes. To stabilize the quality of an image, it is necessary to constantly control the toner concentration.However, as a method for this, a toner / carrier mixing ratio is measured by a magnetic permeability sensor or the like provided in a developing device, and the toner is measured. There is provided a means for replenishing the toner in accordance with the amount of toner consumed.
[0003]
In order to make the charge amount of the toner in the two-component developer uniform to a predetermined value, it is necessary to agitate and mix the newly replenished toner and the developer already existing in the developing device. At this time, if the stirring is not performed sufficiently, the charge amounts of the individual toners vary, causing poor image quality. Therefore, in a developing device using a two-component developer, means for stirring the toner in the developing device is provided.
[0004]
[Problems to be solved by the invention]
In order to quickly and sufficiently mix the two-component developer, it is required to stir the developer at a higher speed in the developing device. However, the conventional developer stirring means has a constant developer stirring speed during the printing process operation. Therefore, immediately after replenishing the toner, the toner and the carrier cannot be sufficiently stirred in a short time, which may affect the image quality.
[0005]
On the other hand, when the amount of toner to be newly replenished is small, stirring at high speed causes excessive stirring, which may affect the life of toner and carrier.
[0006]
The present invention provides an image capable of high quality printing by agitating the developer optimally according to the operation state of the image forming apparatus and / or the amount of toner supplied into the developing unit during the printing process. It is intended to provide a forming apparatus.
[0007]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides an exposure unit for exposing a photoreceptor, a developing device for developing a latent image formed by the exposure unit with a developer housed therein, and a developing device for developing the latent image. An image forming apparatus including a transfer unit that transfers a formed image to a recording medium, the image forming apparatus including: a stirring unit that stirs a developer in a developing unit; and a driving source that drives the stirring unit. The apparatus further includes a developer stirring speed control unit that controls a stirring speed of the stirring unit according to an operation state, and the developer stirring speed control unit selectively switches at least two types of developer stirring speeds. It is assumed that.
[0008]
Further, the image forming apparatus has a toner replenishing unit for replenishing toner to the developing device and a toner replenishing amount estimating unit for estimating a toner replenishing amount replenished by the toner replenishing unit. It has a developer stirring speed control means for controlling the developer stirring speed based on this.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
(Embodiment 1)
FIG. 1 is a configuration diagram of an image forming apparatus according to the present embodiment. Hereinafter, the configuration and operation of the image forming apparatus will be described with reference to FIG. In FIG. 1, the image forming apparatus 40 has a developing unit for four colors, that is, a yellow developing unit 41Y, a magenta developing unit 41M, a cyan developing unit 41C, and a black developing unit 41K, which are vertically arranged in the apparatus. A paper feed cassette 43 for accommodating the recording paper 42 is provided, and a recording paper transport path 44 (a transport path for the recording paper from the paper feed cassette 43) is provided at a location corresponding to each of the developing units (41Y to 41K). Hereinafter, the upstream portion of the recording paper conveyance may be distinguished from 44a and the downstream portion may be distinguished from 44b) in the vertical direction.
[0010]
The developing devices (41Y to 41K) form yellow, magenta, cyan, and black toner images in order from the upstream side of the recording paper transport path 44, and include a photoconductor (50Y to 50K) and a developing sleeve (51Y to 51K). 51K), a charging unit (not shown), and other members that realize a series of electrophotographic development processes.
[0011]
Transfer rollers (52Y to 52K) corresponding to the developing units (41Y to 41K) are disposed at positions facing the photoconductors (50Y to 50K) of the developing units (41Y to 41K) with the recording paper conveyance path 44 interposed therebetween. I have.
[0012]
A paper feed roller 53 that sends out the recording paper 42 at a predetermined timing is provided near the paper feed cassette 43. By rotating the paper feed roller 53, the recording paper 42 is transported in the direction d0.
[0013]
A pair of registration rollers 55 and a pair of pinch rollers 56 are provided as nip conveyance means on the entrance side of the recording paper conveyance path 44a located between the paper supply roller 53 and the transfer portion of the most upstream developing device (yellow: 41Y). I have. The pair of the registration roller 55 and the pinch roller 56 temporarily stops the recording paper 42 conveyed by the paper feed roller 53 and conveys the recording paper 42 toward the developing device at a predetermined timing.
[0014]
Reference numeral 60 denotes a recording paper passage sensor. The recording paper passage sensor 60 has ultrasonic transmission and reception transducers arranged at positions facing each other across the recording paper conveyance path 44a, and detects the leading end of the recording paper to determine the rotation start timing of the registration roller 55. And the function of detecting the thickness of the recording paper 42 when the conveyed recording paper 42 stops momentarily at the position of the registration roller 55, and the function of detecting the presence or absence of double feeding of the recording paper. I have. In the image forming apparatus of the present embodiment, the set value of the transfer bias applied to the transfer rollers (52Y to 52K) is controlled based on the information on the thickness of the recording paper and the presence / absence of double feed.
[0015]
The recording paper 42 is conveyed in the direction of the developing device 41Y along the recording paper conveyance path 44a by the start of rotation of the registration roller 55, and each of the developing devices (41Y to 41K) starts from the rotation start timing of the registration roller 55. 2) are independently controlled.
[0016]
A fixing unit 62 is provided as a nip conveying unit on the exit side in the recording paper conveying path 44b located downstream of the most downstream developing unit (black: 41K). The fixing device 62 includes a heating roller 63 and a pressure roller 64. Further, a transport path switching unit 65 is disposed downstream of the fixing device 62. The conveyance path switching means 65 is urged in the direction d1 when recording an image. At this time, the recording paper 42 is guided to the discharge roller 66.
[0017]
Reference numeral 67 denotes a recording paper trailing edge detection sensor for monitoring the discharge state of the recording paper 42. Although the image forming apparatus according to the present embodiment has a configuration capable of performing double-sided printing, if the user has designated a double-sided printing mode via an interface unit (not shown), image formation on the first side is completed. Then, when the trailing edge of the recording paper 42 is detected by the recording paper trailing edge detection sensor 67, the transport of the recording paper 42 is stopped, and the transport path switching means is urged in the direction d2. Thereafter, the discharge roller 66 is rotated in a direction opposite to the discharge direction. By this control, the recording paper 42 is sent out in the direction d3, and is conveyed again along the recording paper conveyance path 70 for double-sided printing to the position of the recording paper conveyance path 44a. At this time, the recording surface of the recording paper 42 is reversed, and an image can be formed on the second surface.
[0018]
A controller 72 receives image data from a computer (not shown) or the like via an external network and generates printable image data.
[0019]
73 is an engine control unit. The engine control unit 73 controls the hardware and mechanism of the image forming apparatus, forms an image on the recording paper 42 based on the image data transferred from the controller 72, and performs overall control of the image forming apparatus.
[0020]
FIG. 2 is a schematic view of the developing device 41 and its peripheral portion. The developing device 41 is disposed so as to face the photoreceptor 50, and the inside of the developing device is divided into a first chamber 13 and a second chamber 14 by a partition 12. The first chamber 13 and the second chamber 14 are respectively provided with toner stirring screws 15a and 15b as stirring means, and the two-component developer in the developing device is rotated by the rotation of the stirring screws 15a and 15b. Convey while stirring. A passage (not shown) connecting the first chamber 13 and the second chamber 14 is provided at an end in the developing device, and the two-component developer circulates through the first chamber 13 and the second chamber 14. Has become. Further, when the toner in the two-component developer is consumed by the development, the toner stored in the toner replenishing tank 16 is conveyed into the developing device 41 by the hopper motor 17, and newly stirred by the stirring screws 15 a and 15 b in the developing device 41. The replenished toner and developer are agitated.
[0021]
FIG. 3 is a side view of the developing device of FIG. The developer stirring screw 15 is driven by a drive motor 20 as a drive source.
[0022]
The drive motor 20 employs a stepping motor, and controls the frequency of the excitation signal input to the stepping motor to change the rotation speed of the developer stirring screw 15. In the present embodiment, the rotation speed V of the stirring screw 15 is rotated at a first stirring speed V0 (hereinafter referred to as V0) during development by the developer stirring speed control means, and is set to V0 during non-development. It is rotated at a relatively high second stirring speed V1 (hereinafter, described as V1). In this embodiment, V0 is a rotation speed corresponding to the same rotation angular speed as that of the developing sleeve 51, and V1 is set to be 2 × V0.
[0023]
FIG. 4 is a timing chart showing a printing sequence of the image forming apparatus according to the present embodiment. Hereinafter, the rotation speed control of the developer stirring screw 15 will be described in detail with reference to FIGS.
[0024]
First, when image data is transferred from a host computer or the like (not shown) to the controller 72 of the image forming apparatus 40, the engine control unit 73 controls each unit of the image forming apparatus and starts preparation for printing. Specifically, first, the temperature control of the fixing device 62 is started. When the temperature of the heating roller 63 of the fixing device 62 reaches a predetermined value, a plurality of driving sources (not shown) are activated to start the rotation of the heating roller 63 and the pressure roller 61 and to start the rotation of the heating roller 63. Control is performed so that the surface temperature becomes a predetermined constant value.
[0025]
Next, the rotation of the polygon mirror 46 is started. When the polygon mirror 46 reaches a predetermined number of rotations, the rotation of the photoconductor 50 and the rotation of the developing sleeve 51 start as shown in FIG. At this time, at the same timing, the drive motor 20, which is the drive source of the stirring device in each of the developing devices (41Y to 41K), is rotated at a speed setting of V1 to start stirring the developer (the driving motor 20 Are provided one by one).
[0026]
When the printing preparation of the image forming apparatus is completed in this way, the first recording paper 42 is first picked up by rotating the paper feed roller 53 and sent out to the paper transport path 44a. The leading end of the recording paper 42 conveyed by the rotation of the paper feed roller 53 enters the registration roller 55, and the skew of the leading end is mechanically corrected by the registration roller 55 (section PR).
[0027]
The leading end of the conveyed recording paper 42 is detected by the paper passing sensor 60, and the rotation of the registration roller 55 is started after a lapse of a predetermined time from the detection point (the registration roller 55 is moved before the recording paper 42 enters the registration roller 55). The rotation start timing of the registration roller 55 is set starting from the timing at which the leading edge of the recording paper 42 is detected by the paper passing sensor 55 so that the rotation of the registration roller 55 is not started.)
[0028]
At the timing when the recording paper 42 reaches the nip position between the photoconductor 50Y and the transfer roller 52Y, the rotation speed of the developer stirring screw 15 in the developing device 41Y is reduced from V1 to V0 (at the end of the section R-Dy). Although the drive source 20 of the developer agitating screw 15 has already been described as adopting a stepping motor, it is almost practical to adopt a motor that includes both V0 and V1 in a frequency range where slow-up / slow-down is unnecessary. The driving speed can be changed with time.
[0029]
In the case where the configuration of the image forming apparatus (so-called tandem type) as in the present embodiment is employed, as shown in FIG. 4, a period in which development is performed by the developing device 41Y (yellow) and a period in which There is a time lag in the execution period (section Dy-Dm). The developing device 41M reduces the developer stirring speed from V1 to V0 at the timing when the recording paper 42 reaches the nip position between the photosensitive member 50M and the transfer roller 52M, as in the case of the developing device 41Y.
[0030]
In this way, the developing by the developing device 41Y is started, the developing by the developing device 41M is started after the leading end of the recording paper 42 passes through the section Dy-Dm, and the leading end of the recording paper 42 passes through the section Dm-Dc. After that, development by the developing device 41C is started, and finally, after the leading end of the recording paper 42 passes through the section Dc-Dk, development by the developing device 41K is started. The developer stirring speed in each developing device is reduced from V1 to V0 based on the development start timing. By providing the developer stirring means (drive motor 20) independently for each developing device 41, more optimal control can be performed in accordance with the developing state of each developing device.
[0031]
When the printing speed (continuous printing) of an image forming apparatus having a tandem configuration is to be increased, the shorter the interval between recording paper to be fed (hereinafter simply referred to as “paper interval”), the higher the speed. Printing is possible. However, as described above, it is necessary to stop the registration roller 55 to mechanically correct the skew at the position of the registration roller 55, so that the sheet interval cannot be reduced to zero.
[0032]
Therefore, as shown in FIG. 4, immediately after the second sheet is fed, the rotation of the registration roller 55 is temporarily stopped (of course, the trailing end of the first sheet is The sheet is conveyed completely), and mechanical skew correction is performed by the registration roller 55. However, the recording paper 42 is located at the nip position between the photoconductor 50 and the transfer roller 52 for a period corresponding to the sheet interval for the developing device. A non-development state is caused because there is no such section (a section in the non-development state is uniquely determined by the rotation start timing of the registration roller 55, and therefore, a CPU (central processing unit: not shown) mounted on the engine control board 73) The developing state and the non-developing state of the developing device can be grasped based on the timing setting of the registration roller 55).
[0033]
In this non-developing state, the rotation speed of the developer stirring screw 15 of the developing device 41 is accelerated from V0 in the developing state to V1. When an image is formed on the second sheet of recording paper following the first sheet, the recording sheet 42 is placed at the nip position between the photosensitive member 50 of each developing unit 41 and the transfer roller 52 in the same manner as in the printing process of the first sheet. At this time, the rotation speed of the developer stirring screw 15 is reduced from V1 in the non-development state to V0 in the development state to perform the development. When the rear end of the recording paper 42 is out of the nip position, the developer stirring screw 15 is rotated. The rotation speed 15 is accelerated from V0 in the developing state to V1 in the non-developing state. When the number of prints increases, this process is repeated according to the number of prints.
[0034]
As described above, in the present embodiment, the developer agitation speed is controlled at a high speed in the state between the sheets (non-development state generated by this) in the image forming apparatus having the tandem configuration. Thereby, high-speed stirring of the developer can be performed, and the image quality can be improved.
[0035]
Next, another example of increasing the toner stirring speed in the non-development state will be described. When performing double-sided printing in the image forming apparatus having the same configuration as described above, first, the recording paper 42 is fed by the recording paper roller 53 and printing is performed on the first surface (the printing procedure is the same as described above). Omitted.) At the time of development, each developing device rotates the stirring screw 15 at a rotation speed V0 by the drive motor 20. During the process of inverting the recording paper 42 for printing on the second surface after printing on the first surface, that is, while the transport path switching unit 65 is operating, and the recording paper is moved through the recording paper transport path 70 for double-sided printing. During the passage, the developing device does not perform development, and a non-developed state occurs. When the developing device is in the non-developing state, the rotation speed of the drive motor 20 of the developing device is increased, and the rotation speed of the developer stirring screw 15 is increased to V1. Then, when the printing process of the second surface starts and the developing state is reached, the rotation speed of the developer stirring screw 15 is returned to V0 again, and the development on the second surface is started.
[0036]
(Embodiment 2)
In the first embodiment, means for increasing the speed of stirring of the developer during non-development has been described. However, an embodiment in which the amount of toner supplied into the developing device is further considered as a condition for stirring at high speed will be described.
[0037]
For the toner supply amount, for example, the printing rate is measured by a printing rate measuring unit such as counting of the number of recording pixels to estimate the toner consumption amount, and the toner supply amount is determined according to the predicted toner consumption amount. In the case where printing with a low printing rate continues and the toner supply amount is small, stirring at high speed may affect the life of the toner and the carrier due to excessive stirring. The present invention is intended to prevent the developer from being excessively stirred in such a case.
[0038]
Hereinafter, a means for controlling the stirring speed in consideration of the toner replenishing amount when toner is replenished into the developing device with toner consumption in Embodiment 2 will be described with reference to FIGS. 1 to 5. 1 to 4 are the same as those in the first embodiment, and a description thereof will be omitted. FIG. 5 is a flowchart illustrating a flow of a process according to the second embodiment.
[0039]
When printing is performed in the image forming apparatus having the same configuration as that of the first embodiment (the printing procedure is omitted because it is the same as that of the first embodiment), the toner in the two-component developer is consumed by performing the development. Then, the hopper motor 17 is driven according to the consumed toner amount, and new toner is supplied from the hopper 16 into the developing device. The amount of toner to be replenished is calculated by counting the number of recording pixels to be printed, thereby predicting the amount of toner consumed by printing, and determining the driving time of the hopper motor in accordance with the predicted amount of toner consumption, thereby determining the actual amount of toner. Can be estimated.
[0040]
Hereinafter, a process of controlling the developer stirring speed according to the toner supply amount will be described with reference to the flowchart of FIG. For simplicity, a single developing device will be described below.
[0041]
(S1) In each developing device, the amount of toner M replenished since the previous high-speed stirring was performed is stored in a memory (not shown). When the value of M is equal to or more than the predetermined amount M1, the process proceeds to the next step S2.
[0042]
(S2) At this time, if the developing device is in the non-developing state, the process proceeds to the next step S3. If the development is being performed, the development is continued, and the process proceeds to the next step S3 when the non-development state is reached.
[0043]
(S3) At this point, since the amount of newly replenished toner is equal to or more than the fixed amount M1 and the developing device is in the non-developing state, the rotation speed V of the developer stirring screw 15 is increased to V1. Then, high-speed stirring of the developer is performed.
[0044]
(S4) In the non-development state, the rotation speed of the developer stirring screw 15 is maintained at V1, and high-speed stirring is continued. When entering the developing state again, the process proceeds to the next step S5.
[0045]
(S5) When the developing device enters the developing state, the value M of the replenished toner amount is initialized to zero.
[0046]
(S6) The rotation speed V of the developer stirring screw 15 is returned to V0. Then, the process returns to step S1 again.
[0047]
By performing the above steps, the stirring speed is increased only when the toner supply amount exceeds a predetermined amount, so that it is possible to prevent the developer from being excessively stirred when the toner is not sufficiently supplied. it can. As a result, it is possible to sufficiently agitate the two-component developer and reduce the effect of excessive agitation on the life of the toner and the carrier.
[0048]
【The invention's effect】
As described above, according to the image forming apparatus of the present invention, during the printing process operation, the developer is agitated in accordance with the operation state of the image forming apparatus and / or the amount of toner supplied to the developing device. Therefore, high-quality printing can be performed.
[0049]
As a specific example, the two-component developer can be sufficiently and quickly mixed by performing the stirring of the developer at a higher speed in the non-developing state during the printing process operation, and as a result, a more stable High quality images can be obtained. In addition, by determining whether or not to perform high-speed stirring according to the toner supply amount, when the toner supply amount is small, stirring is not performed more than necessary, and the effect on the life of the toner and the carrier can be reduced.
[Brief description of the drawings]
FIG. 1 is a diagram of the overall configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a diagram of a developing device. FIG. 3 is a side view of the developing device of FIG. FIG. 5 is a flowchart showing the flow of processing when the developer stirring speed is increased in accordance with the toner supply amount.
15a, 15b Stirring screw 20 Drive motor 40 Image forming device 41Y-K Developing device 50Y-K Photoconductor

Claims (8)

Exposure means for exposing the photoreceptor, a developing device for developing the latent image formed by the exposure means with a developer housed therein, and a transfer means for transferring an image visualized by the developing device to a recording medium In the image forming apparatus provided with
Stirring means for stirring the developer in the developing device, a drive source for driving the stirring means,
An image forming apparatus comprising: a developer stirring speed control unit that controls a stirring speed of the stirring unit according to a state of a developing operation of a developing unit. 2. The image forming apparatus according to claim 1, wherein the developer stirring speed control unit selectively switches at least two types of developer stirring speeds. The method according to claim 1, wherein the developer stirring speed selectively takes at least a first stirring speed (V0) and a second stirring speed (V1) higher than the first stirring speed. 3. The image forming apparatus according to 2. 4. The image according to claim 3, wherein the developer stirring speed control unit switches the developer stirring speed from the first stirring speed to the second stirring speed during a non-developing operation during continuous image formation. Forming equipment. 4. The developer stirring speed control unit according to claim 3, wherein the developer stirring speed control unit switches the developer stirring speed from the first stirring speed to the second stirring speed during a recording medium reversal process during the formation of a two-sided image. Image forming device. 6. The image forming apparatus according to claim 4, wherein the developer stirring speed control unit controls the developer stirring speed to take a first stirring speed during a developing operation during image formation. 7. The image forming apparatus according to claim 1, further comprising: a toner supply unit that supplies toner to the developing device; and a toner supply amount estimation unit that estimates a toner supply amount supplied by the toner supply unit. . The developer stirring speed controller controls the developer stirring speed based on at least one of a state of a developing operation of a developing device and a toner supply amount estimated by the toner supply amount estimator. Item 8. The image forming apparatus according to Item 7.

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