JPS5872967A - Developing device - Google Patents

Abstract

PURPOSE:To keep the charge quantity of a developer constant to stabilize the image density, by providing a sensor, which detects the humidity of the ambient atmosphere, in a developing device and controlling the operation time of a means for charging the dry developer by the output of this sensor. CONSTITUTION:A toner density detector 52 which detects the toner density in a developer and a humidity sensor 52 which detects the humidity of the ambient atmosphere are provided in a developing device 12 where a magnetic roller 42 and a developer 47 are provided to form an electrostatic latent image on a photosensitive drum 9. A roller 57 is controlled by the toner density detector 52 to make the mixture ratio of the toner to the carrier constant, and the count time of a timer 62 is controlled in accordance with the change of the resistance value of the humidity sensor 53 to control rotation time of the magnetic roller 42 and an agitating member 50. Consequently, the charge quantity of the developer is kept constant independently of variance of humidity, and the photographic fog or the like of the background is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a developing device using a dry type developer applied to, for example, a copying machine. In a copying device designed to do this, if the toner concentration in the developer is too low, the image density will be low.
If it is too high, the image density will be high, but background fog and toner scattering will increase.1 Generally speaking, the toner density in the developer is detected and toner is replenished so that it always stays within a certain range. Ii! I am trying to stabilize my quality.

However, although this method keeps the toner density constant, if the toner is used in areas or at different times with different environmental conditions, especially humidity, the toner charge amount may change from the optimum condition, resulting in poor image quality. There is a problem that makes it unstable. In other words, even if the toner concentration is the same, if the toner charge amount is low, background capri and toner scattering will occur as well.On the other hand, if the toner charge amount is high, the highly charged toner will be strongly captured by the carrier and replenished. Since charging of the toner is inhibited and weakly charged toner is produced, background fog may occur. Therefore, if the toner charge amount is too high or too low, it will adversely affect image quality.

As mentioned above, simply controlling the toner concentration does not necessarily result in good and stable image quality; it is necessary to control both the toner concentration and the amount of charge to the optimum values. For the first time, good and stable image quality can be obtained.
Conventionally, such a method has not been discovered.

Figure 1 shows the conditions under low humidity conditions (X)"C,
30%) and under high humidity conditions (, lj”c, 13
%), the horizontal axis represents the time during which the developing device was operated and the developer was triboelectrically charged, and the vertical axis represents the toner charging cap. As is clear from Figure 1, under low-humidity conditions, the toner charge amount tends to increase and stabilize within a few minutes, whereas under high-humidity conditions, the toner charge amount decreases once and then gradually decreases. rose to 9
After ~30 minutes, it tends to saturate at approximately the same value as under low humidity conditions. However, during actual copy operation,
Continuous copying for several 70 minutes is rare,
Also, since the process of toner consumption and replenishment is added,
It is thought that the toner charge amount exhibits a behavior different from that shown in FIG. 1 in its time change.

8112811) Changes in toner charge amount when copying is performed while replenishing toner to keep the toner concentration constant P Observed under high humidity and low humidity conditions, the horizontal axis represents the number of copies made, and the vertical axis indicates the toner charge amount. As can be seen by comparing Figure J2 with Figure 1, the amount of toner charge during actual copying operations stabilizes at approximately the same value under low humidity conditions as when the magnetic roll is continuously rotated, whereas under high humidity conditions The reason for this is that under high humidity conditions, as shown in Figure 1, the rise of the charge is slow, and the copying operation ends before the charge rises completely. it is conceivable that.

As is clear from Figure 2, even if the toner concentration is the same, if the rotation time of the magnetic roll is the same in high humidity and low humidity, the toner charge amount will be the optimum value in low humidity.
/9. However, even in low humidity conditions, if you take measures such as stopping the rotation of the magnetic roll after development, the copying operation will end before the charge increases.
It is possible to keep the toner charge amount close to the optimum value. ◎The purpose of the present invention is to focus on the above points, and to control the operating time of the developer charging means such as a magnetic roll, to control the developer charge amount. It is an object of the present invention to provide a developing device that is appropriately configured so that it can be controlled to a desired value.

The present invention provides a developing device that develops an electrostatic latent image by causing a charged dry developer to act on a charge holding member that holds the electrostatic latent image. The invention is characterized in that it is provided with a means for controlling the humidity in accordance with the humidity of the surrounding air.

The present invention will be described in detail below with reference to the drawings.

FIG. 3 is an Is diagram showing the configuration of an example of a copying apparatus using a developing device according to the present invention. The copying apparatus shown in FIG.
The electrostatic charge once formed on the charge holding memberffjsIll! The structure is such that the same copy image can be formed on several sheets of image-receiving paper by repeatedly performing development and transfer on the image-receiving paper. When a sheet-shaped original l is placed on an inclined original platen and inserted into the original feeding device f13 from the direction of arrow a, it is transported by the transport rollers t and j- of the original feeding device 3 to the first Tachibana tray. It is discharged to Party B. During this time, the original l is illuminated by the illumination lamp 7, and the original image is projected onto the rotating photosensitive drum 9 by the optical system t. The photosensitive drum 9 is constructed by applying a photoconductive layer made of, for example, 8e as a charge retaining member to the surface of a drum-shaped conductor at ground potential. This photosensitive drum 9 rotates in the direction of the arrow, and after being neutralized by the static eliminating lamp lθ, the photosensitive drum 9 is charged by the corona charger/
The photoconductive layer is uniformly charged by the photoconductive layer and then irradiated with the optical image to form an electrostatic latent image on the photoconductive layer. After the electrostatic latent image on the photosensitive drum 9 is developed with toner by the developing device/2 according to the present invention using a dry two-component developer, the electrostatic latent image is transferred to the toner image transfer section 13 as the photosensitive drum 9 rotates.

On the other hand, the image-receiving paper II in the image-receiving paper cassette 1 is fed out one by one by the swinging and rotating pickup roller 16, passes through the image-receiving paper conveyance path member 17 comprising 17 rollers and a guide/7B, and then is delivered at a predetermined timing. The toner image is then sent to the toner image transfer section 13. In the toner image transfer section /3, the image receiving paper is transferred to the photosensitive drum 9 so as to overlap with the toner image.
The toner image is transferred there by the action of the transfer device/I.The transfer device/I can also be configured using a DC corona charger, but here, the toner image is transferred by the action of the transfer device/I. In order to effectively maintain the electrostatic latent image on the photosensitive drum 9, a transfer bias power source l? is placed in contact with the photosensitive drum 9. A bias roller transfer device is used, which is equipped with a conductive transfer roller connected to the toner image transfer unit 13.The image receiving paper that has passed through the toner image transfer section 13 is conveyed in close contact with the photosensitive drum t, so it is separated by a peeling claw. The toner image is peeled off by the image receiving paper conveyance path member 17 and is conveyed along a guide 70 constituting the image receiving paper conveyance path member 17, and sent by a conveyance roller n into a heat fixing device 241 having a heater, where the toner image is After the image is fixed, it is ejected to the copy trace by the ejection roller Δ.

The toner image on the photosensitive drum is not completely transferred to the image receiving paper, but a portion remains. This residual toner is removed by the rotating cleaner brush L, and the removed toner is sucked by the air flow generated by the rotation of the 7-inch motor and collected by the filter Z.◎Cleaner brush L and fan I
is covered with a housing 30 in order to obtain effective toner suction power and also to prevent toner from scattering within the device. 7) The exhaust of the J is guided by the toner image transfer section/J, and is discharged from the discharge port that looks into the toner image transfer section/J.
It is used to effectively peel the image-receiving paper from the photosensitive drum 9 in cooperation with the photosensitive drum 9. Cleaner brush l has support shaft 3λ
The electrostatic latent image formed once on the photosensitive drum is repeatedly developed and transferred to a plurality of sheets. When copying multiple sheets in which toner images are sequentially transferred to image-receiving paper, it is configured to be separated from the photosensitive drum!In addition, near the periphery of one photosensitive dot t, between the light image irradiation position and the development position. A trimming lamp 3f- is arranged to erase charges on a portion 1, that is, a blind area, which does not correspond to the image receiving paper /j used on the photosensitive drum 9.The above-mentioned parts constituting this electrophotographic apparatus are The operation is controlled based on the detection of the document position by the switches 3S and 34, and the switch 3S is activated to rotate the main motor that rotates the photosensitive drum 9 and the like.

Reference figure is a sectional view showing the detailed structure of an example of the developing device 12 according to the present invention shown in FIG. 3.Developing device 1 of this example
2 is equipped with a magnetic roller q, which is removably attached to the main body of the copying machine; When developing the electrostatic latent image, the non-magnetic sleeve is connected to the main motor by the operation of a solenoid (not shown) and rotated in the direction of arrow 0, and stored in the bottom of the Kutani device Q. A developer coat consisting of carrier and toner is caused to stick to the surface of the non-magnetic sleeve in the form of spikes by the magnetic force of the magnet bar 11, and is conveyed by the rotation of the non-magnetic sleeve in the direction of arrow 0 to the photosensitive drum. 9 to develop the electrostatic latent image formed on the photosensitive drum 9. On the lower edge of the opening of the container Q facing the photosensitive drum 9, there is a developing image conveyed by the magnetic roller 2. Amount of agent〃1mint) Chia1 % Fu5 Doctor blade a, which regulates the height of the panicle, is fixed by the screw culm.It is still adjacent to the magnetic reeler duck at the bottom of $＠＄3. At the position, a stirring member y provided with stirring blades for stirring the developer rod is rotatably provided. This stirring member is rotated in synchronization with the magnetic roller q, and the developer q that has completed its developing action is conveyed by the magnetic roller q.
is scraped off to the bottom of the container IIQ by the developer scraping plate S/. This scraping plate xi is pivotally attached to the container q so that it can freely swing, and due to its own weight, its swinging tip comes into contact with or approaches the surface of the non-magnetic sleeve stop. Container Q
Scrape it onto the bottom of the sleeve and stir again to make the developer q adhere to the surface of the non-magnetic sleeve again. Further, a toner concentration sensor 1152 for detecting the toner concentration in the developer is arranged at a position close to the flow path of the developer p due to the magnetic roller attack, and a toner concentration detector 1152 for detecting the toner concentration in the developer is placed at an arbitrary position in the container Q. A stone on which a humidity sensor Ω is placed to detect the humidity of the surrounding atmosphere.

On the other hand, in the upper part of the container Q, there is a hopper 5# that stores toner for replenishment, the toner receiver made of the container Q and a leaf spring is formed by a plate, and the entrance of the hopper y can be opened and closed with a lid U. Configure. Further, at the outlet of the hopper y, there is provided an F toner supply roller I that rotates based on the output of the toner concentration detector jλ described above. This supply tube lug is provided with a notch JAIL for storing the toner in the hopper s and supplying it to the bottom of the container, and during rotation, the end of the plate lamp of the toner receiver engages with the notch 37 & Place it like this◎
In this example, in order to prevent undesired toner from being replenished from the hopper to the bottom of the container (I3), especially when the toner tray is
In order to prevent replenishment from the gap between the ribs, the toner receiver is provided with a lip 4t3a projecting from the container #a3 that constitutes the hopper j4I above the plate S3 by a length of about jNb, and on the bottom surface of this rib. Attach sponge jS.

In this way, by rotating the supply roller gtt based on the output of the toner waste level detector S2, the toner contained in the notch j7a is supplied to the bottom of the container Q, and the toner and carrier in one developer c are mixed. Always maintain the ratio at the desired value.

Furthermore, Yong ii! An opening for accommodating developer of a predetermined mixing ratio including new carrier is formed in the central part of ##l, and this is configured to be openable and closable by a developer replenishment lid n. As shown in FIG. 5, the resistive element is constructed with a resistance element that exhibits low resistance when the environmental humidity is high and exhibits a high resistance when the environmental humidity is low. In this example, the rotation of the magnetic roller p, that is, the non-magnetic sleeve stirring member 50, is controlled in accordance with the resistance value of the humidity sensor S3.

Figure 7 shows the configuration of an example of a circuit that controls the rotation time of the non-magnetic sleeve according to the resistance value of the humidity sensor Ω, and Figure 7-G show signal waveforms to explain its operation. In the figure, based on the electrostatic latent image once formed on the photosensitive drum 9,
A timing chart when copying sheets is shown. In this example, the counting time of the timer Q is controlled based on the resistance value of the humidity sensor, thereby controlling the rotation time of the magnetic roller and the stirring member j0. The input terminals t and y-t are supplied with the main motor drive signal shown in FIG. A necessary signal synchronized with the falling edge of the last frame of the signal is supplied, a drive signal for the illumination lamp shown in FIG. When you turn on the power switch! The output terminals -1 and 0 which supply the master reseller F signal which rises and falls when turned off are connected to a solenoid for coupling the magnetic roller Q, that is, the non-magnetic sleeve stirring member y, to the main motor.

In this embodiment, the main motor rotates when the original detection switch 35 is activated by inserting the original l, but until the illumination lamp 7 lights up, the output terminals 6←l and I
Since no voltage is generated between the magnetic roller II2 and the stirring member j0, the solenoid for connecting the magnetic roller II2 and the stirring member j0 to the main motor is off, and the magnetic roller and stirring member 5θ do not rotate. When the drive signal for the illumination lamp 7 rises at a predetermined timing as shown in Figure B, and the illumination lamp 7 lights up, a voltage is generated between the output 1 1ll-/ and the cylindrical wire in synchronization with this lighting. Then, the solenoid is energized, the magnetic roller agitation member j0 rotates, and the electrostatic latent image formed on the photosensitive drum 9 is developed. The timer Q starts counting when the development of the last sheet (in this case, the third sheet) of the electrostatic latent image formed on the photosensitive drum 9 is completed, and the time determined by the resistance value of the humidity sensor j3 has elapsed. At this point, the potential difference between the output terminals U-/ and α-1 becomes zero, the solenoid is turned off, and the rotation of the first magnetic roller Q and the stirring member end is stopped. The count time of the timer Ω determined by the resistance value of the humidity sensor S3 is short as shown in Figure 7 when the resistance value is high in low humidity, and as shown in Figure 7 1 when the resistance value is low in high humidity. becomes longer. Therefore, when the humidity is low, the magnetic port, tube (and stirring member 30)
) rotation time is shown in Figure 7! It becomes shorter as shown in FIG. 7, and becomes longer as shown in FIG. 7G when the humidity is high, so that a constant toner charge amount can always be obtained regardless of the environmental humidity.

FIG. 1 shows that a copying machine using a developing device according to the present invention can be used at high temperatures (2 K'Ce II %) and at low humidity (
This is a diagram showing the transition of the toner charge amount when copying is performed on the J"CI! 1 Rotation time of the main motor in these cases 1 Magnetic roller (at high humidity and low humidity)
As is clear from FIG. 1, the developing device according to the present invention optimizes the amount of toner charge even in high humidity and low humidity. can be kept at a value. Also, as is clear from Figure 1, the rotation time of the magnetic roller (and stirring member) is 10
00 copies per copy at high humidity and JIt outer low outer humidity is 241 minutes, which is almost the same as at high humidity.

Note that the present invention is not limited to the above-mentioned example, and can be modified in many ways. For example, in the above-mentioned example, the magnetic roller 2 is composed of a non-magnetic sleeve and a magnetic nail, and a non-magnetic Although the sleeve member is rotated, the magnet rod aS may be rotated while the non-magnetic sleeve is fixed, or the magnet rod IS may be rotated without using the non-magnetic sleeve member. Further, the dry developer is not limited to a two-component developer, and the present invention can be effectively applied to a magnetic-component developer. Furthermore, the present invention can be effectively applied not only to magnetic brush development but also to cascade development. Furthermore, in the example described above, the humidity of the surrounding atmosphere was detected by the humidity sensor and the rotation time of the magnetic roller was automatically controlled, but in FIG. 4, a manually adjustable variable resistor is connected in place of the humidity sensor 53. It is also possible to manually control the rotation time of the magnetic roller.

In this case, by setting the resistance value of the variable resistor in a semi-fixed manner depending on the humidity conditions of the environment in which the developing device is used,
The amount of charge of the developer can always be maintained at a desired value.

As described above, in the present invention, since the operating time of the means for charging the dry developer is controlled according to the humidity of the surrounding atmosphere, the amount of charge on the developer can be kept almost constant at all times. Therefore, an electrostatic latent image can be developed with stable image density and without generating back-ground capri.

[Brief explanation of the drawing]

Figure 1 is a diagram comparing the toner charge amount at low humidity and high humidity. Figure 1 shows the toner charge amount at low humidity and high temperature when continuous copying is performed with the toner concentration constant. Fig. g shows a comparison of the above, No. JWJ is a line diagram showing the structure of an example of a copying device using the developing device according to the present invention, and Fig. 3 shows a cross section showing the detailed structure of an example of the developing device shown in Fig. 3. Figure, No. J [
is a diagram showing the characteristics of the humidity sensor shown in Figure 4, Figure 6 is a diagram showing the configuration of an example of the rotation time control circuit of the magnetic roller shown in Figure 41, and Figures 7-G are diagrams showing its operation. A signal waveform diagram for explanation; FIG. 1 is a graph showing a comparison of the toner charge amount at low humidity and high humidity in the present invention; and FIGS. FIG. 4 is a signal waveform diagram for explaining the operation of the copying device and the developing device when the image is obtained. 9...Photosensitive drum, /2...Developing device, a2...
Magnetic roller, G3...Developer container, Item...Non-magnetic sleeve, 4IS...Magnetic bar, C...Developer, S2...
・Toner concentration detector, S3...humidity sensor, y...
Toner hopper, G...Toner supply ・Feed roller, U
...Timer, u-i Nu-s...Input terminal, u-
/, M! -Ko...output 熾子. Fig. 4 Fig. 5 RH (%) Fig. 6 Fig. 7 Figure 51: Fig. 8 Copy hole missing (nucleus) Fig. 9

Claims (1)

[Scope of Claims] L In a developing device configured to develop an electrostatic latent image by causing a charged dry developer to act on a charge holding member that holds the electrostatic latent image, 1. means for charging the dry developer; Developing device 0 characterized in that it is provided with a means for controlling the operating time according to the humidity of the surrounding atmosphere. A humidity sensor is provided to detect the humidity of the surrounding atmosphere, and the rotation time of the magnetic brush is automatically controlled based on the output of the humidity sensor so that the amount of charge on the dry developer is always approximately constant. A developing device according to claim #I1, characterized in that it is configured as follows. & The charged dry developer is made to act on the charge holding member as a rotating magnetic brush, and the control means is provided with a time setting device for manually setting the rotation time of the magnetic brush. Claim No. 1
Development Vi! Place 0