JPH02186369A - Image forming device - Google Patents

Abstract

PURPOSE:To avoid problems of ground fogging or low density even when environment changes so as to obtain an appropriate image by providing a control means, which controls the size of a developing bias electric field impressed between a developer supporting body and an image carrier based on signal from an environment detecting means. CONSTITUTION:The environment detecting means 19, constituted of a humidity sensor and a temperature sensor, is provided at the position in the environment where the higroscopic condition of toner is well reflected, in the vicinity of a developing device or a toner replenishing device, and information signal from this environment detecting means 19 is fed to a control means 18. The control means 18 controls an effective value for AC of a developing bias electric source 1', corresponding to the information signal from the environment detecting means 18. Thus, even when the environment changes, problems such as ground fogging or low density do not generate and a stable image can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION -1 The present invention generally relates to an image forming apparatus using an electrophotographic method or a static recording method, and particularly relates to a two-component developing method in which development is performed using magnetic carrier particles and toner particles. The invention relates to the above-mentioned image forming TFI, and can be suitably implemented in image forming apparatuses such as monochrome, two-color, multi-color or full-color electrophotographic copying machines, and color recording devices of computer output units. It is something.

ILIL Standing In this type of image forming apparatus, the developer used to visualize a latent image formed on an image bearing member such as a photoreceptor contains two components: magnetic carrier particles and non-magnetic toner particles. Mixed, place! There is a $'f two-component developer. When developing with this two-component developer, place a magnet inside 1'[
The two-component developer is supplied onto a developer support such as a developer sleeve, and a magnetic field is exchanged between the photoreceptor and the developer sleeve. 11 field is applied to form a magnetic brush made of developer, and the L magnetic brush is brought into sliding contact with or close to the surface of the photoreceptor to form a toner image on the photoreceptor -1- (Japanese Patent Application Laid-open No. Publication No. 55-32060, Japanese Unexamined Patent Publication No. 1973
9-185082), thereby.

We are trying to efficiently increase image density, remove ground blur, and remove image defects such as clumping.

In addition, a non-contact two-component alternating electric field development method for the purpose of two simple color development and multiple development is also disclosed in Japanese Patent Application Laid-open No. 14265/1983.
JP-A-58-68051, JP-A-56-144452
No., JP-A-58-181362, JP-A-80-176
Many proposals have been made to distribute liquids, such as in Publication No. 069.

Furthermore, recently, various image forming apparatuses have been required to be multicolored or full-color for graphic output, and the images have also been improved in terms of density, halftone reproducibility, color balance, etc. Technology to maintain high quality has become necessary, and for this reason, toner particles have become smaller,
latent image contrast of each color) it/I N, fog prevention +
Control of hTlt level has been carried out.

However, although conventional control methods compensate for the effects of environmental fluctuations to a certain degree in Nl image potential control, they are difficult to compensate for due to subtle density changes in full-color image formation using toner of multiple colors. The image quality could be significantly degraded due to changes in the quality of the image, blurring of the soil, etc. Furthermore, no matter how much correction is made using the latent image potential, if the performance of the developer itself fluctuates due to changes in the surrounding environment, it cannot be compensated for, and therefore color balance is easily lost. Ta.

Therefore, an object of the present invention is to detect environmental changes related to mixing and to control the magnitude of the alternating electric field applied to rJJl between the developer support and the image carrier, thereby eliminating excess or deficiency of toner. , even if the environment changes, 11! ! It is an object of the present invention to provide an image forming apparatus which solves problems such as fogging and low density, and which can produce proper images.

- Part 1 - Item 1 is completely coupled by the image forming apparatus according to the present invention. In summary, the present invention carries a developer,
1. A developing means having a developer support body that is conveyed to a development area opposite to the carrier body is provided, and the developer support body is provided with ? A component developer is applied, and a magnetic field and a developing bias electric field having an alternating electric field are applied between the image carrier and the developer support to develop the PPI image on the image carrier and form a visible image. , and further transfer the visible image to a transfer material to form an image? t
fi, an environment detection means for detecting the humidity in the environment near the first stage of development, and a development bias electric field applied between the developer support and the image carrier based on the signal from the mtx detection means. The image forming apparatus is characterized in that it has a control means for controlling the size. Preferably said control means is operated externally to the image forming apparatus.

Support 1 Hereinafter, the image forming apparatus according to the present invention will be specifically explained based on the illustrated embodiment.

In the embodiment shown in FIG. 2, an image forming apparatus according to the present invention is embodied in an electrophotographic color printer equipped with a rotary developing device 2tl.

In this embodiment, a photoreceptor drum 3, which is a 3gj carrier, is provided rotatably in the direction of the arrow, and is adjacent to the photoreceptor drum 3 for rotational development. e111 is placed.

The rotary developing device AT has a yellow developing device IY and a magenta ring IM on the outer peripheral surface of the rotating body, respectively.

There are two cyan developers IC and one black developer IBK. Although not shown, a developer (toner) replenishing device is provided for the developing device 11, and a developer (toner) replenishing device is provided for each developing device.

It is equipped with a magenta hopper, a cyan hopper, and a black hopper.

To explain further, in this embodiment, the photosensitive drum 3 is uniformly charged by a charger 4, and imagewise exposed by a laser beam E modulated by a yellow image signal of an original (not shown).

Photoreceptor drum 3 Quiet to the north! A latent image is formed. The layer image is
Development is performed by a developing device of a rotary developing device 211 disposed phantom to the photosensitive drum 3, in this case a yellow developing device IY positioned at a developing position facing the photosensitive drum 3.

On the other hand, paper feed guide 5a, paper feed roller 6, paper feed guide 5b
The transfer material that has advanced through the gripper 7 is rotated at a predetermined timing and held by the gripper 7, and is electrostatically wound around the transfer drum 9 by the contact roller 8 and its opposing pole.

The transfer drum 9 rotates in the direction of the arrow in synchronization with the photosensitive drum 3, and the developed image developed by the yellow developer IY is transferred onto the transfer material in the transfer section by the action of the transfer charger IO. The transfer drum 9 continues to rotate once and prepares for primary color transfer (for example, magenta transfer in this embodiment).

After the yellow developing image is transferred to the transfer material at the transfer section, the photosensitive drum 3 is neutralized by the charger 11, cleaned by the cleaning member 12, charged again by the charger 4, and then charged by the next magenta image signal. Similarly exposed. During this time, the developing device 1 rotates, and the magenta developer 11M is positioned at a predetermined development position in place of the yellow developer lY, and the latent image formed on the photoreceptor drum 3 is developed with magenta. do.

Subsequently, the same process is performed for cyan and black to complete the transfer of four colors.

In this way, the four-color toner images are transferred to the transfer material of the transfer drum 90, and then the charges are removed by the charger 13414. Then, the gripper 7 is released and the transfer material is separated from the transfer drum 9 by the separating claw 15, and the transfer material is sent to the fixing device 17 by the conveyor belt 16.
It will be established.

As a result, a series of color printing operations is completed, and a full color print image is formed on the transfer material.

According to the present invention, in this embodiment, as shown in FIGS. 1 and 2, a humidity sensor is installed near the developing device or toner replenishment device at a position in the environment that reflects the moisture absorption state of the toner. An environment detection means 19 consisting of a temperature sensor and a temperature sensor is provided, and information signals from the environment detection means 19 are supplied to the first control stage 18 as shown in FIG.

The stage 18 controls the effective AC component of the developing bias 1111X1' in response to the information signal from the environment detection means 19. A developing bias power source 1' applies an alternating electric field between the photosensitive drum 3 and a developer support that supports the developer in the developing device and conveys it to the photosensitive drum 3. The developer support is shown as a developing sleeve 2 in FIG. 1, and is shown as a developing sleeve 2 in FIG.
Developing sleeve 2 (2Y, 2M) installed in c and IBK
, 2C and 2BK).

The properties of the toner stored in each developing device of the developing device 2Il are as follows.
As can be understood from the m3 diagram, if we take the humidity on the horizontal axis and the toner tripo on the vertical axis, the toner tripo fluctuates greatly depending on the humidity, and at low humidity, the toner charge increases too much and the toner and carrier The bonding force becomes strong, and a large electric field is required to transfer the toner from the developing sleeve 2 to the photosensitive drum 3. On the other hand, under high humidity conditions, the tripod is too droopy and too much toner is applied, causing one image to collapse and toner to adhere to non-image areas. Therefore, under the development conditions of 4 times as shown in Figure 4,
The humidity dependence of the concentration is large. Furthermore,
Even for toner of the same particle size, each color has different band characteristics, so there is variation in density with respect to humidity, as shown in Figure 4.

Therefore, in the present invention, in order to reduce this density difference, humidity is detected and the alternating electric field applied to the developing sleeve 2 is controlled as shown in FIG.

That is, one flJI 01 method determines whether the detection signal from the environment detection stage 19 corresponds to humidity, M, or H, as shown in FIG. 5(a).

Depending on the state, the magnitude of the alternating electric field, directly the bias' and the output voltage of the ti source 1', are switched in three stages. Also, there are other ways! ￥15 As shown in figure (b),
Depending on the detection signal from the environment detection means 19, that is, the humidity, and also each color band? The output voltage of the bias {eftl' is continuously changed by iir 1j1# according to lt5+-.

As described above, the control described in (1)-- is performed by the control means 18 based on the judgment result based on the information signal from the environment detection stage 19. In other words, when the humidity is low, a large electric field is applied to prevent the carrier and toner from bonding! In this case, the -L limit of the magnitude of the alternating electric field is determined by the withstand pressure between the photosensitive drum 3 and the developing sleeve 2. In addition, when the humidity is high, the magnitude of the alternating electric field is lowered to the extent that the maximum density is (1#) to prevent excessive toner adhesion.

Also, considering the i'IjlfR timing in the control means 1B, the environment detection means 19 is always operating and detects the environment (humidity, temperature, etc.), but for the output f4 of the detection means 19, If the magnitude of the alternating electric field in the developing bias power supply 1' is controlled in real time, the above control may occur during one image formation, causing density changes in the same image or during continuous copying. At L.
Therefore, considering this point, the above control is effective when the potential control is performed during warm-up after turning on the power, or during post-rotation after image formation. It is best to perform this after image formation is completed, such as when the image is inserted.

The effect of controlling the voltage applied to the developing sleeve according to the present invention as described above will be explained with reference to FIG.

Image (copy) density decreases when humidity is low.

By increasing the VPP, the copy characteristics as shown by the dotted line are raised as shown by the solid line, and conversely, when the humidity is high, the copy density decreases as shown by the dashed line, so it is corrected by lowering the VPP as shown by the solid line. Further, as described above, when the control means 18 performs control according to each color and each humidity state based on its characteristic curve, stable color balance and density can be obtained.

In other words, according to such a configuration according to the present invention, even if the toner is affected by humidity, the magnitude of the alternating electric field is controlled accordingly.

The extent of the magnetic brush formed by the toner between the image carrier and the developer support can be adjusted, ensuring sufficient density even under low humidity conditions, and suppressing ground blur and scattering under high humidity conditions. Good images that are not affected by environmental changes can be obtained.

The relationship between the developing device and the photosensitive drum according to the twenty-first embodiment will be explained with reference to FIG.

In this embodiment, the developing sleeve 2 of the developing device is made of a non-magnetic material 1 such as aluminum or 5US318.

The developing sleeve 2 faces a horizontally elongated opening formed in the long direction f of the container 36 on the lower left wall of the container 36 of the developing device, with its right half circumference facing inside the container 36 and its left half circumference exposed outside the container. It is arranged so that it is rotated in the direction of the arrow, and is pivotally supported at both ends. At this time, the photosensitive drum 3 is rotationally driven in the direction of arrow a.

In addition, a permanent magnet (magnet) 23 is inserted and fixed in the developing sleeve 2, and the permanent magnet 23 does not move even when the developing sleeve 2 rotates. 23 are N pole 23a, S pole 23b, N pole 2
It has a configuration in which 4fa poles of 3c and S pole 23d are installed in the arrangement shown in the figure. Note that an electromagnet may be used instead of a permanent magnet as the magnetic field generating means.

Also, the above configuration with the developing sleeve 2 installed! A non-magnetic blade 24 as a developer ML regulating member is disposed at the upper edge of the opening, with a base fixed to the side wall of the developer sleeve 136, and regulates the toner thickness on the surface of the developing sleeve 2. Further, inside the non-magnetic blade 24, a magnetic particle limiting member 26 is provided in the container 36, and a magnetic particle limiting member 26 is provided on the lower surface of the container 36.
A t-agent guide surface 261 is formed.

As the carrier for the two-component developer used here, magnetic particles (carrier) having a particle size of 30 to 100 μLm, preferably 40 to 80 μLm are used. This magnetic particle 27
has a resistance value of 107Ωcm or more, preferably 101Ωa
Ferrite particles (maximum magnetization 60em
u/g) coated with resin.

Note that the resistance value of the magnetic particles 27 is measured at the measurement electrode surface @
Using a sand char type cell with 4 c tr+' and an inter-electrode gap of 0.4 cm, 1 kg of V was applied to one electrode, and an applied voltage E (V/cin) was applied to both ffi poles. 1 It was done by ittm flowing into the circuit.

Further, in this embodiment, a seal member 40 is provided at the bottom of the container 36 to seal off toner that accumulates in this portion. The sealing member 40 has a certain elasticity and is in elastic contact with the surface of the developing sleeve 2. Further, the sealing member 40 has a free end located on the upstream side in the rotational direction of the sleeve in the contact area with the developing sleeve 2 so as to allow the developer to flow back into the container. Further, at the lower end of the opening of the container 36, there is a scattering prevention electrode plate 30 that applies a voltage of the same polarity to the floating developer generated in the developing process to cause it to adhere to the developing sleeve side and prevent it from scattering. It is located.

Furthermore, a toner replenishment roller 60 is disposed within the container 36 and is responsive to an output obtained by a toner concentration detection sensor (not shown). The above sensor includes a method for detecting the volume of developer, a piezoelectric element, an inductance change detection element,
An antenna method using alternating bias, a method that detects optical density, etc. can be used.

Further, the toner replenishing roller 60 replenishes the non-magnetic toner 37 when it stops rotating.

The fresh developer replenished with the toner 37 is mixed and stirred while being conveyed by the screw 61. Therefore, triboelectricity is applied to the toner replenished during this conveyance. The fresh developer conveyed by the screw 61 is transferred to the screw 62 through notches formed at both ends of the partition plate 63.

The S pole 23d in the developing sleeve 2 serves as a transporter for keeping the collected developer after development on the sleeve surface and collecting it into the container 2!36. Further, in the vicinity of this S pole 23d, positional exchange is performed between the fresh developer conveyed by the screw 62 provided close to the developing sleeve 2 and the recovered developer after development. Further, the two conveyance screws 64 evenly divide iJ of the developer in the axial direction of the developing sleeve 2. The developer conveyed on the sleeve as the developing sleeve 2 rotates is conveyed in the axial direction by the screw 64.

In this process, the layer of developer that forms a convexity in the axial direction on the sleeve is partially reversed through the space M and returned in the opposite direction to the conveyance direction.
The screw 64 is configured to transport the current GL agent in the opposite direction to the screw 62.

Here, the distance dZ between the end of the non-magnetic blade 24 and the surface of the developing sleeve 2 is 50 to 900 m, preferably 150 to 900 m.
800 pm. If this distance is smaller than 50 grn, the magnetic particles 27 will clog, making it easy to cause unevenness in the developer layer and making it difficult to remove good #il. Therefore, dz is the current fI! ! Unwanted particles mixed in the agent! ! ! In order to prevent cloth from clogging the so-called blade, 400#Lrn or higher is preferable, and conversely, 90#Lrn is preferable.
If it is larger than 0 iLm, the gate of the developer applied onto the developing sleeve 2 increases, the adhesion of magnetic particles to the photoreceptor drum increases, the circulation of the developer decreases, and the developer mM by the developer limiting member 26 increases. This weakens the toner, causing a toner tripod shortage, resulting in easy fogging. This point must also be taken into consideration.

In this embodiment, the distance ciz between the end of the non-magnetic blade 24 and the surface of the developing sleeve 2 is set to 1, for example, 75.
0 gm, and the surface of the developing sleeve 2 and the photosensitive drum 3
+1[ of 450 pm. Further, the photosensitive drum 3 uses an OPC drum.

The Wl image potential was -700V. Furthermore, the developing bias is a DC voltage of -590V and an AC voltage of 3 frequencies 2KHz.
ut pressure, under low humidity VPP is 2, OKV, under high humidity VPP is 1, OKV,! : to be exchanged, t'it
By controlling the pressure using the control unit yt18 to superimpose the pressure, it was possible to obtain a good image with little variation in density.

FIG. 7 shows another embodiment of the image type l& device according to the present invention.

In this embodiment, dedicated photoconductor drums 3Y, 3M,
3C and 3BK are prepared, and around them are dedicated laser beam scanners 80Y, 80M, 80C, and 80BK.
, developer IY, LM, IC, IBK, transfer charger 10
Y, 10M, LOG, l0BK, cleaner 12Y, 12
M, 12C1128K is placed.

The transfer material passes through a paper feed guide 5a, is sequentially conveyed to a paper feed roller 6, and then a paper feed guide 5b, receives a corona current from an attraction charger, and is reliably attracted to a conveyor belt 9'. After that, the image formed on each photoreceptor drum is transferred by the transfer charger described above, and the transfer material, which has been neutralized by the V# and charger 82, is separated from the conveyor belt (. The image is fixed. In this way, a full color image is obtained.

The image forming apparatus of this embodiment also includes a developing device 777 as shown in FIG.
Based on data from
This allows stable images to be obtained without being affected by environmental changes.

Note that the image forming process, configuration, and a value shown in the above embodiments do not equally restrict the present invention.

Image formation according to the present invention configured as above in "U Example" L-ri? c′m
detects environmental information regarding humidity in the vicinity of the developing device, and uses this information to adjust the AC effective fm of the developing bias electric field.
By controlling V p p , even if the environment changes, stable images can be obtained without causing problems such as blurring or poor density. In particular, according to the present invention, a stable image can be obtained even when the particle size of toner is reduced in response to recent improvements in image quality. Since an appropriate developing bias electric field is applied according to the tripo, the minimum amount of toner required can be efficiently moved to the image area, the color balance of each color can be equalized, and copies that are extremely faithful to the original can be obtained. .

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing a control system of an embodiment of an image forming apparatus according to the present invention. FIG. 2 shows a full-color image according to an embodiment of the present invention.
- a schematic sectional view of a photocopying machine; FIG. 3 is a graph showing the relationship between humidity and toner tribo. No. 41.4 is a graph showing the relationship between humidity and density for each color. FIGS. 5(a) and (b) show the humidity in each color toner and the corresponding effective development bias to be controlled ((N V
It is a graph showing the relationship between p and p. FIG. 6 is an enlarged sectional view of the developing unit. FIG. 7 is a schematic sectional view of another embodiment according to the present invention. The tJSB diagram is a graph showing the combination of copy density adjustment to original density. :Developing device':Developing bias power source:Developing sleeve (developer support):Photosensitive drum (image carrier) 8:Control means 9:Round detection means Fig. 2, Fig. 6, Fig. 7, Fig. 6 Humidity Figure 4 Humidity Figure 8 Original concentration

Claims (1)

[Claims] 1) A developing means having a developer support supporting a developer and transporting it to a development area facing the image carrier is provided, the developer support is coated with a two-component developer, and the image carrier is coated with a two-component developer. A magnetic field and a developing bias electric field having an alternating electric field are applied between the image carrier and the developer support to develop the latent image on the image carrier into a visible image, and further transfer the visible image onto a transfer material. In the image forming apparatus for obtaining an image, an environment detecting means for detecting humidity in the environment near the developing means, and a voltage applied between the developer support and the image carrier based on a signal from the environment detecting means. An image forming apparatus comprising: a control means for controlling the magnitude of a developing bias electric field.