JP2893857B2 - Developer concentration measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) In the present invention, in an image forming apparatus using a powder developer composed of a toner and a carrier, the developer concentration of the developer is measured by an optical method. The present invention relates to a developer concentration measuring device.

(Prior Art) In an image forming apparatus using a powder developer comprising a toner and a carrier, in order to optimize the image density, the developer density, that is, the weight mixing ratio of the toner to the carrier (hereinafter, referred to as “toner”) Density) is measured, and toner must be replenished based on the result.

Therefore, as a method for measuring the toner concentration, an optical concentration measurement method has been proposed in which the developer in the developer stirring section is illuminated through a transparent detection window and the toner concentration of the developer is measured from the reflected light. I have.

(Problems to be Solved by the Invention) However, this optical density measurement method has a problem that when the developer is attached to the transparent detection window, the true toner density of the developer cannot be measured.

Also, if the amount or bulk density of the developer in contact with the transparent detection window fluctuates, the measurement result will fluctuate. In other words, even if the developer concentration is appropriate, the amount and bulk density of the developer fluctuate, There has been a problem that a result that the developer concentration is inappropriate may be obtained.

(Means for Solving the Problems) The present invention has been made in order to solve the above-mentioned problems, and a developer concentration measuring device is provided with a housing portion for housing a developer including a toner and a carrier, which is rotated. A rotating member that stirs the developer in the storage section while facing the storage section, a transparent detection window having a conductive film on a surface facing the developer, and a developer in the storage section through the detection window. A measuring unit that illuminates and measures the developer concentration from the reflected light; and is supported by the rotating member and rotates while maintaining a substantially constant distance from the detection window with the rotation of the rotating member. An electrode having a portion formed of a conductive member, at least one magnet supported by the electrode, holding the developer, and bringing the developer into contact with the detection window based on rotation of the rotating member; and the detection window and the electrode. Applied between A bias for electrically repelling the detection window and the toner, and a developer downstream of the detection window with respect to a rotation direction of the rotating member, the developer being held by the magnet being regulated. And a weir portion that forms a developer pool at the opposite portion of the developing device.

In another aspect of the developer concentration detecting device according to the present invention, the center of the detection window is shifted upstream with respect to the rotation center of the rotating member in the rotation direction of the rotating member.

(Operation) According to the above configuration, when the rotating member rotates, the developer holding the magnet periodically slides and cleans the transparent detection window.

In addition, since the distance between the detection window and the electrode is kept constant, the electric field effect based on the bias is stabilized, and toner adhesion to the detection window is effectively prevented.

Therefore, the reflected light of the light illuminated on the developer through the detection window reflects the true developer concentration, and high-accuracy density detection is performed. Further, a downstream side of the detection window with respect to the rotation direction of the rotating member is provided with a dam portion that regulates the developer held by the magnet and forms a developer pool at a portion facing the detection window. The developer retained in the detection window stays at the position of the detection window (developer concentration detection device) for a relatively long time, and as a result, the maximum peak portion of the image density signal detected by the detection section is stabilized, and with high reliability The toner density can be measured.

Still further, in another aspect of the present invention, the center of the detection window is shifted to the upstream side in the rotation direction of the rotation member with respect to the rotation center of the rotation member. The developer is gradually compressed until reaching the closest position between the rotating member and the detection window. Therefore, in a region where the developer is compressed, the contact force of the developer with the detection window is strong, and in a region including the center of the detection window, the developer attached to the detection window is efficiently removed.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows a full-color copying machine 1 by electrophotography. In this copying machine 1, a print switch (not shown) is used.
Is pressed, the photoconductor 2 rotates in the direction of the arrow, and the outer peripheral photoconductor layer is uniformly charged by the charging device 3.

The image reading device 5 illuminates a document (not shown) placed on the document table 4, and the reflected light is exposed to the reading optical unit 6, and three color signals of red, blue, and green are provided for each pixel. Is read as The red, blue, and green color signals are converted into ternary or quaternary signals by adding yellow, magenta, cyan, or black thereto by an image processing circuit, and sent to the laser generator 7.

The laser generator 7 irradiates a charged area of the photoconductor 2 with a laser beam modulated based on the signal, and forms an electrostatic latent image according to image information of each color.

The developing unit 8 includes a plurality of developing devices 8Y, 8M, 8C, and 8B each containing a two-component developer composed of a toner and a carrier. One developing device faces the photoconductor 2, and the electrostatic latent image is visualized with a toner of a corresponding color. The developing device 8
Y, 8M, 8C, and 8B contain yellow (Y), magenta (M), cyan (C), and black (B) toners, respectively.

The toner images are sequentially transferred to the transfer paper conveyed from the paper feeding device 9 and wound around the outer periphery of the transfer drum 10 based on the discharge of the transfer device 11, thereby forming a full-color toner image.

The transfer paper on which the full-color toner image is formed is the transfer drum
Separated from 10, and transported to the fixing device 13 by the transport device 12,
Here, the toner image is heated and fixed on the transfer paper, and the discharged toner 14 is discharged.
Is discharged.

2 and 3 show developing devices 8Y, to 8B (hereinafter referred to as "developing device 8Y").
Abbreviated. ) Is shown.

The developing device 8Y generally includes a developing unit 20, a developer stirring unit 30 (hereinafter, referred to as a "stirring unit 30"), and a toner replenishing unit 60.

The developing unit 20 contains a developing roller 21 facing the photoconductor 2. The developing roller 21 includes a magnet 22 fixed to a non-rotating state, consists sleeve 23 for rotating the periphery, the sleeve 23 is drivingly connected to the developing motor M _1, arrows a
It is designed to rotate in the direction. Also, sleeve 23
It is connected to the high voltage power supply 25, a predetermined developing bias V _B are adapted to be applied. Further, a spike height restricting plate 25 faces the upper outer peripheral surface of the sleeve 23.

The stirring section 30 includes a first stirring path 31 adjacent to the developing section 20,
A second stirring path 32 located behind the second stirring path 32 is provided. The first stirring path 31 is parallel to the developing unit 20, and the second stirring path 32 is lower on the near side (right side in FIG. 2) than the first stirring path 31 and is lower on the far side (left side in FIG. 2). It is provided with an inclination so as to be higher than one stirring path 31. Although the stirring paths 31, 32 are separated by a wall 33, passages 34, 35 formed by cutting the back side and the near side of the wall 33, and a bypass passage 33a formed by cutting the back side of the near side passage 35. And are connected by

The bucket roller 36 and the conveying screw 37 are connected to the first stirring path.
31 and the second stirring path 32, respectively, and both stirring motors
Is drivingly connected to the M ₂ arrows b, it is so as to rotate respectively in the c direction.

The light shielding plate 39 is attached to the shaft 38 of the transport screw 37 outside the developing tank, rotates together with the transport screw 37, and is detected by the photo interrupter 40. With this photo interrupter 40, the rotational positions of the magnets 45 and 46 described later can be detected.

The electrode 41 is a non-magnetic conductive material (eg, copper or aluminum)
Frustoconical cylindrical member consisting of
And is fixed to a region between the passage 35 and the bypass passage 33a, and is grounded via a shaft 38. Magnets 42 and 43 are embedded in the outer periphery of the electrode 41 at 180 ° symmetrical positions. The angle θ between the outer peripheral surface of the electrode 41 and the shaft 38 (see FIGS. 2 and 4) is an angle at which the upper end surface of the electrode 41 becomes horizontal when the electrode 41 is mounted on the shaft 38.

As shown in FIG. 4, the toner concentration detection sensor 50 includes a housing 51 and a light emitting element 52 fixed to the housing 51.
, A light receiving element 53, and a transparent detection window 54 covering the detection positions of these elements 52, 53, and a blocking wall 56 is formed along one side of the transparent detection window 54. The detection window 54 is formed of a transparent member (for example, Nesa glass) having a conductive film formed on the outer surface facing the second stirring path 32.

As shown in FIG. 2, the toner concentration detection sensor 50 is disposed above the electrode 41, and has a transparent detection window 54 fixed to face the electrode 41. As shown in FIGS. 5 and 6, the detection position X of the sensor 50 is perpendicular to the center thereof.
However, it is set so as to be located on the upstream side in the rotation direction of the transport screw 37 with respect to a perpendicular m passing through the center of the shaft 38. The blocking wall 56 is located on the downstream side in the rotation direction of the transport screw 37 with respect to the perpendicular m. Further, the detection window 54 is connected to the window bias power source 58, the window bias V _W charging polarity identical to the polarity of the toner is adapted to be applied.

The toner supply section 60 is adjacent to the rear of the second stirring path 32 and has a supply port 61 provided at the back of the toner density detection sensor 50.
Is connected to the second stirring path 32 via the. Further, the toner replenishing section 60 is connected to a toner hopper (not shown) so that the toner of the corresponding color is supplied from the toner hopper. Replenishing screw 62 is disposed in the toner supply unit is drivably coupled to the toner supply motor M _3.

 The operation of the developing device will be described.

In the developing device, a developer composed of a toner and a carrier is accommodated in a first stirring path 31 and a second stirring path 32.

The developer is supplied to a bucket roller 36 and a conveying screw 37.
2, the toner and the carrier are transported while being mixed and agitated according to the path shown in FIG. 2, and the toner and the carrier are charged to opposite polarities (here, the toner has a negative polarity and the carrier has a positive polarity). Develops the electrostatic latent image.

That is, the developer in the first stirring path 31 is
It is transported from the back side to the front side by the rotation of 36. Further, the developer is scooped by the bucket roller 36 and supplied to the sleeve 23. The developer is regulated by the facing portion of the spike height regulating plate 25, and then the toner is supplied to the electrostatic latent image by the facing portion of the photosensitive member 2. Are visualized.

The developer conveyed to the near side through the first stirring path 31 passes through the path 35
And, it is conveyed to the second stirring path 32 via the bypass passage 33a. Here, the amount of the developer transported through the passage 35 is substantially constant regardless of the amount of the entire developer, and the remaining developer is transported to the second stirring path 32 through the bypass passage 33a. . This is because, in the second stirring path 32, the electrode 41 serves as a resistance of the developer, and the amount of the developer passing outside the electrode 41 is regulated to a substantially constant amount. Therefore, the developer is uniformly dispersed as a whole without causing a bias on the back side or the front side of the stirring paths 31 and 32. Further, no excessive pressure is applied to the detection window 54.

The developer in the second stirring path 32 is conveyed from the near side to the back side while being mixed and stirred by the rotation of the conveying screw 37, and is conveyed to the first stirring path 31 through the back side passage 34.

The developer passing around the electrode 41 is transported by the screw 37
It is held by the magnets 42 and 43 that rotate together with it.

As shown in FIG. 5, the developer held by the magnets 42 and 43 alternately rubs the detection window 54 of the toner density detection sensor 50 as the transport screw 37 rotates. Further, the developer is scraped off by the blocking wall 56, and the scraped developer forms a pool in front of the blocking wall 56, and the developer is substantially constant until the magnets 42 and 43 pass. The detection window 54 is stably contacted with the pressure of. Since the electrode 41 is made of a non-magnetic material, the developer pool is formed only when the magnets 42 and 43 face the detection window 54, and the pool is not formed at other times. .

The developer conveyed through the second stirring path 32 is replenished to the magnets 42 and 43 that have passed through the portion facing the dam wall 56. That is, the developer held by the magnets 42 and 43 is replaced by a fixed amount every one rotation, and new developer is conveyed to the opposite portion of the detection window 54. Therefore, the same developer does not stay in front of the blocking wall 56 repeatedly.

Incidentally, the residual amount of the developer is closely related to the projection length l ₃ of Sekitomekabe 56, replacement is deteriorated developer in the lower region of the projecting length l ₃ is too long and the detection window 54, the opposite If the length is too short, stable contact of the developer with the detection window 54 cannot be obtained, so that the optimum length needs to be determined by experiments.

A vertical line n passing through the center of the toner density detection area X is
The conveying screw 37 is located on the upstream side in the conveying screw rotation direction with respect to a vertical line m passing through the rotation center of the conveying screw 37. Therefore, the developer conveyed while being in contact with the detection window 54 is perpendicular m
Is gradually compressed to the position. Therefore, in the region up to the perpendicular m, the contact force of the developer with the detection window 54 is strong, and in the region Y in FIG. 6, the developer attached to the detection window 54 is efficiently removed.

However, since the contact force of the developer is weak in the area Y ′ from the perpendicular m to the dam wall 56, the toner adheres to the detection window 54. However, since this area Y 'is out of the toner density detection position X, there is no problem in detecting the toner density.

Detection In between the window 54 and the electrode 41, the window bias V _W is applied an electric field of the same polarity as the toner to the detection window 54 from the power source 58 (here negative) is formed. This field also rotates the conveying screw 37, are stable because substantially constant distance l ₂ is maintained between the detection window 54 and the electrode 41.

Due to the electric field, the detection window 54 electrically repels the toner charged to the same polarity as the toner, and prevents the toner from adhering to the detection window 54. However, the carrier since it is a window bias V _W opposite polarity, the carrier is attached to the detection window 54 field effect is too strong relative to the carrier. Therefore, the value of the bias V _W, it is necessary to consider the relationship between the distance l ₂ between the detection window 54 and the electrode 41 experimentally determined.

In the toner concentration detection sensor 50, the light emitting element 52 is
The reflected light is detected by the light receiving element 53.

The light receiving element 53 outputs a signal having a waveform shown in FIG.

In the output waveform shown in FIG. 8, the maximum peak portion P ₁ is,
A signal when the developer held by the magnets 42 and 43 is in contact with the detection window 54. The signal in this area is sampled to measure the toner density. Note that the minimum peak part P ₂ is a magnet
Reference numerals 42 and 43 are signals when the evacuation from the detection window 54 is performed.

For comparison, FIG. 9 shows the sensor output when there is no dam wall 56. In the figure, the maximum peak P ₁ ′ is
_{2 and} 43 are signals when the detection window 54 is opposed, and the minimum peak portion P ₂ ′ is a signal when the magnets 42 and 43 are retracted from the opposed portion of the detection window 54.

As shown in FIGS. 8 and 9, by providing the blocking wall 56 as in this embodiment, the developer held by the magnets 42 and 43 stays at the detection position X of the detection window 54 for a relatively long time, signal of the peak portion P ₁ is can be seen that stable.

The controller 70 determines the toner density based on the output from the sensor 50 as follows.

That is, based on the timing of detecting the detection plate 39 attached to the transport screw 37 photointerrupter 40, samples the data of the maximum peak portion P _1, the toner density is measured based on the sampled data. As described previously, the output of the maximum peak portion P ₁ is stable, there is no variation in the Sapling data, the reliability of the measured toner density is high.

As a result of the measurement, when it is determined that the toner density is lower than the predetermined reference density, the toner is supplied to the toner supply unit 60 from the toner hopper having the toner of the corresponding color. Replenished toner by the rotation of the toner supply motor M _3, is fed to the second stirring passage 32 through the toner supply port 61.

Experiments described below was performed with respect to the optimized bias V _W applied to the detection window 54. The distance l ₁ between the perpendiculars m and n is 4 m
m and the magnetic force of the magnets 42 and 43 were 2,000 gauss.

As a result of the experiment, as shown in FIG.
When the interval l2 between the _two was constant, carrier adhesion occurred in the detection window 54 when the window bias _VW was too high, and toner adhered to the detection window 54 when the window bias _VW was too low.

Moreover, when narrowing the interval l _2, developer clogging between the detection window 54 and the electrode 41, or replacement of the developer deteriorates, increasing the bias V _W widely apart l ₂ Conversely, each unit It became necessary to secure the insulation of the battery.

Therefore, the value of the bias V _W, it is necessary to determine the most appropriate value to the developing device in consideration of the above items experimentally.

In the above description, the entirety of the cylindrical electrode 41 is formed of a conductive material. However, the cylindrical member may be formed of an insulating member and the periphery thereof may be covered with a conductive material.

(Effects of the Invention) As is clear from the above description, in the developer concentration measuring device according to the present invention, the rotating member of the developer accommodating portion is provided with an electrode so as to keep a constant distance from the transparent detection window, A bias is applied between the detection window and the electrode to electrically repel the detection window and the toner, and a magnet is provided on the electrode, and the detection window is cleaned with the developer held by the magnet. ing.

Therefore, toner adhesion is prevented by the electric field generated by the bias. In addition, since the distance between the detection window and the electrode is kept constant, the electric field effect thereof is also stably performed. Further, the developer attached to the detection window is removed by the developer held by the magnet. That is, the detection window is kept in a state where the developer is not attached by the electric field effect of the bias and the cleaning effect of the developer held by the magnet.

As a result, the reflected light of the light illuminated on the developer through the detection window reflects the true developer concentration, and the density can be detected with high accuracy.

Further, since a blocking portion is provided on the downstream side of the detection window with respect to the rotation direction of the rotating member to regulate the developer held by the magnet and form a developer pool at a portion opposite to the detection window, the magnet is provided. The developer retained in the detection window stays at the position of the detection window (developer concentration detection device) for a relatively long time, and as a result, the maximum peak portion of the image density signal detected by the detection section is stabilized, and with high reliability The toner density can be measured.

Further, in another embodiment of the present invention, the center of the detection window,
The developer conveyed while being in contact with the detection window reaches the closest position between the rotation member and the detection window because the developer is shifted upstream with respect to the rotation center of the rotation member in the rotation direction of the rotation member. Until it is gradually compressed. Therefore, in a region where the developer is compressed, the contact force of the developer with the detection window is strong, and in a region including the center of the detection window, the developer attached to the detection window is efficiently removed.

[Brief description of the drawings]

1 is a cross-sectional view of a copying machine, FIG. 2 is a cross-sectional view of a developing device, FIG. 3 is a cross-sectional view of the developing device shown in FIG.
4 is a partially cutaway side view showing a toner concentration detection sensor and electrodes, FIG. 5 is a sectional view taken along line IV-IV of FIG. 4, FIG. 6 is a bottom view of a detection window, and FIG. FIG. 8 shows the relationship between the distance between the electrodes and the distance between the electrodes and the optimum bias, FIG. 8 shows the output of the toner concentration detection sensor, and FIG. 9 shows the output of the toner concentration detection sensor of the developing device having no blocking wall. It is. 30: developer stirring section (stirring section), 31: first stirring path, 32: second stirring path, 41: electrode, 42, 43 ... magnet, 50: toner concentration detection sensor, 54: transparent detection window, 56 ... Dam wall, 58 ... Power supply, V _W
... window bias.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-60-60665 (JP, A) JP-A-61-212868 (JP, A) JP-A-60-80879 (JP, A) 105948 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) G03G 15/08

Claims (2)

(57) [Claims] An accommodating portion accommodating a developer comprising a toner and a carrier; a rotating member for stirring the developer in the accommodating portion while rotating; a conductive member provided on a surface facing the accommodating portion and facing the developer; A transparent detection window having a film, a measurement unit that illuminates the developer in the storage unit through the detection window, and measures the developer concentration from the reflected light; and a rotation of the rotation member that is supported by the rotation member. An electrode that rotates while maintaining a substantially constant interval with the detection window, at least a portion facing the detection window is formed of a conductive member, and is supported by the electrode, holds the developer, and rotates the developer. At least one magnet that is brought into contact with the detection window based on the rotation of a bias applied between the detection window and the electrode, so that the detection window and the toner are electrically repelled; Rotation direction And a damping portion downstream of the detection window for regulating the developer held by the magnet to form a developer pool at a portion opposite to the detection window. apparatus. 2. The developer concentration detecting device according to claim 1, wherein a center of said detection window is shifted upstream with respect to a rotation center of said rotary member in a rotation direction of said rotary member.