JPH01312568A - Developing device for image forming device - Google Patents

Abstract

PURPOSE:To prevent toner from partially and excessively sticking to a developing roller and to prevent a partial change in pressure between the developing roller and a photosensitive drum by reversing the partial deformation of the developing roller within an allowance range and after that, starting developing action. CONSTITUTION:When a copying machine is not operated, the developing roller 22 is stopped, and its contact position with the photosensitive drum 4 and its abutting position on a regulation blade 24 are not changed. Thus, pressure is concentrated on the same place and the periphery of the developing roller 22 is deformed. Therefore, after a power source is turned on and an atmospheric temperature becomes one that is set beforehand, the rotation of the developing roller 22 is started. The developing roller 22 is rotated after it is made into a state where it is easy to be reversed so that a time until it is reversed is reduced. Moreover, the developing roller 22 is made into a state where printing can be started after it is rotated for a specified time after rotation is started. Thus, printing and developing are started after the deformation of the developing roller 22 is eliminated. Therefore, the toner does not partially and excessively stick to the developing roller and normal image formation is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a developing device for an image forming apparatus such as an electrophotographic copying machine, a printer, or the like.

[Prior art]

In an image forming apparatus, such as a one-component developing device of an electrophotographic copying machine, a developing roller made of an elastic material such as rubber transports a developer to develop a latent image on a latent image carrier, such as a photosensitive drum. Form a visible image.

On the developing roller, the toner layer is thinned into a uniform layer by a regulating blade, and the toner on the developing roller is adhered to the latent image while the developing roller is in pressure contact with the photosensitive drum.

In such a conventional developing device, when the copying machine is not operating, the developing roller stops and the contact position of the developing roller with the photosensitive drum and the regulating blade does not change, so pressure is concentrated in the same place. As a result, the outer peripheral surface of the developing roller is deformed.

When the developing roller is rotated, pressure is concentrated and it takes time for the deformed area to return to its original state. Particularly at low temperatures, the ability to recover from deformation decreases, and recovery takes additional time.

When printing is started with the developing roller still deformed and a developing action is performed on the photosensitive drum, the amount of toner adhering to the deformed portion of the developing roller increases extremely, and horizontal streaks occur in the image after development.

[Problem to be solved by the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a developing device that solves the above problems and performs development without causing abnormalities on images even after the image forming device has stopped for a long time.

[Means to solve problems]

The present invention solves the above problem by making it possible to start the rotation of the developing roller after the ambient temperature of the developing roller reaches a predetermined temperature after power is turned on, and to start the developing action after the rotation continues for a predetermined period of time. The problem has been solved by a developing device of an image forming apparatus characterized by the following.

[Effect]

According to the present invention, since the developing roller starts rotating after reaching a predetermined temperature, the developing roller is rotated after it is in a state where it can easily be restored, thereby shortening the time until it is restored. Further, the developing action is not performed until the developing roller continues to rotate for a certain period of time from the start of rotation, that is, at least the time required for recovery, that is, after the developing roller has rotated for a certain period of time, it is ready to start printing. This means that printing and development will only begin after the deformation of the developing roller has been resolved and it has returned to its pre-deformed state, so there will be no areas where the amount of toner adhesion has increased abnormally, and it will be normal. image formation is performed.

〔Example〕

The details of the present invention will be explained based on the embodiments shown in the figures.

Prior to the description of the present invention, an overall description will be given of an example of an image forming apparatus to which the present invention is applied.

FIG. 1 shows a laser printer as an example of an image forming apparatus, in which recording paper 2 is fed from a paper feeder 1 in the direction of arrow A, and is timed by a pair of registration rollers 3 to form a drum-shaped photoreceptor 4. The latent image carrier is transported to the latent image carrier.

The photoreceptor 4 is rotated clockwise as shown by the arrow,
At this time, the surface is charged by the charger 5 and irradiated with laser light from the laser optical system 6 to form an electrostatic latent image on the photoreceptor 4, for example, a photoreceptor drum. This latent image is made visible by toner when it comes into contact with the developing roller 22 of the developing device 17, and this visible image is formed on the photosensitive drum 4.
The visible image is transferred to the recording paper 2 conveyed to the recording paper 2 under the action of the transfer charger 8 , and the transferred visible image on the recording paper is fixed by the fixing device 9 . The recording paper leaving the fixing device 9 is discharged to a paper discharge section 11 formed by the upper wall surface of the printer main body 10 as shown by arrow B.

On the other hand, residual toner is removed from the photosensitive drum 4 after the visible image has been transferred by a cleaning device having a cleaning blade 12 , and a charge removing action is performed by a charge removing device 13 . The toner removed from the photosensitive drum 4 is collected by the impeller 14 into the toner collection chamber 15 and stored there.

In the illustrated laser printer, a latent image carrier including a photosensitive drum 4 and related parts are configured as one latent image carrier unit 16, and an image forming unit including this latent image carrier unit 16 and a developing device 17. are separately and detachably supported by the image forming unit case 18.

The developing device 17 includes a case 21 containing toner T, the developing roller 22 opposed to the photosensitive drum 4, a regulating blade 24 that is a regulating means for regulating the layer thickness of the toner on the developing roller to an even thin layer, It has a supply roller 23 that supplies toner to the developing roller 22, and an agitator 25 that stirs the toner T in the case 2I.

Further, a regulating blade 24 is also assembled to the case 21. Furthermore, a toner cartridge 25 is removably attached to the case 21, and when the remaining amount of toner in the case 21 becomes low, the toner cartridge 25 that was installed
The case 21 can be replenished with toner by replacing the cartridge with a new cartridge containing toner.

In the developing operation, as is well known per se, the toner T in the case 21 is transferred to the developing roller 2 by the rotating supply roller 23.
The toner supplied to the developing roller 22, which rotates counterclockwise, is made into a thin layer by the regulating blade 24, and is transported to an area where the photosensitive drum 4 and the developing roller 22 face each other.
It is electrostatically transferred to the latent image on the photosensitive drum 4.

The developing roller 22 is made of an elastic material such as urethane rubber with a hardness of about 30 degrees, for example, JIS hardness type, and has a film layer of conductive particles formed on its surface layer, forming the photosensitive drum 4 as shown in FIG. Welded together at a pressure of P+. In this case, the developing roller 22 is uniformly pressed against the photosensitive drum 4 over its entire length in the longitudinal direction. Due to this pressure contact, the developing roller 22 is deformed by the amount of pressure contact dI. It is advantageous in terms of the development effect that the developing roller 22 can be pressed against the photosensitive drum 4 and the contact area with the photosensitive drum 4 can be maintained at an appropriate area required for development. Even if the photosensitive drum 4 or the developing roller 22 vibrates to some extent during operation of the printer, since the two are elastically pressed against each other, the contact area will not vary greatly due to the vibration.

A regulating blade 24 serving as a regulating means for making the toner layer adhering to the developing roller 22 into an even thin layer is slidably guided at both ends by guide grooves (not shown), and is pressed against the developing roller 22 by a spring 26 .

The edge of the regulating blade 24 is brought into contact with the developing roller 22 in parallel so that the excess toner on the developing roller 22 is scraped off by the regulating blade 24.

As the material for the regulating blade 24, silicone rubber, such as methyl vinyl polysiloxane, or other resin material is used.

The developing toner contains toner that is harder than the material of the blade 24a or an abrasive material such as SiC, 5t (h
, TiOx and other substances are mixed. If necessary, both a hard toner and an abrasive can be mixed. As a result, even if toner adheres to the blade 24a or dust or the like enters and adheres to the blade 24a, the blade 24a will wear out due to friction with the toner, making it possible to provide self-cleaning properties.

Example, t JIS C2123 Terror 5” ~ 95’
(D hardness (D silicone rubber blade and SiCKv3
In combination with a toner containing 000, the self-cleaning properties are good.

The elastic layer of the developing roller 22 is formed of a material that is softer than the blade 24a and the toner and has a JIS hardness of about 309, type A, and the toner is adhered to the developing roller 22 by the supply roller 23, and the toner layer is regulated by the blade 24a. Then, the blade 24a is polished by the hard toner or abrasive material in the toner, and the amount of toner adhering to the developing roller 22 can be regulated to a uniform layer thickness in a stable state over a long period of time.

The toner supplied by the supply roller 23 is transferred to the developing roller 2.
When the toner layer is one layer in a thin layer state, which is the state after adhering to the toner 2 and being scraped off by the regulating blade 24, the amount of toner adhesion is measured to be 0.4 to 0.5 B/c+s"
When the toner layer is less than one layer, the amount of charge of the toner is maximum (approximately 12 microcoulombs/g).

The thinning state caused by the regulating blade 24 is the same as that of the regulating blade 24.
When the pressure Pt of the regulating blade 24 is sufficiently large, the toner T passes through in one layer, and when the pressure P2 of the regulating blade 24 is small, a multilayer toner is generated due to the powder pressure.

When the toner layer is lower than - layer, the amount of toner adhesion is small, and the amount of toner charge is large, sometimes reaching the maximum, so there is no toner scattering when developed on the photosensitive drum 4, and a sharp image is formed. be able to. However, there is a drawback that the density etc. decreases and the amount of replenishment is insufficient for solid black images. A toner layer of - layer or higher has a large amount of toner adhesion, and a high-density image can be obtained under various environments.However, there is a problem that characters become thicker over time, causing collapse of one-dot images.

In actual results, the amount of toner adhesion that achieves a well-balanced state of image sharpness and density is 0.4 to 0.5.
IIg/c
A musical accompaniment is convenient.

Since the regulating blade 24 is pressed against the developing roller 22 by a pressing force P as shown in FIG. 3, the developing roller 22 is deformed by an amount d2.

The developing roller 22 is deformed at the portion in pressure contact with the photosensitive drum 4 and the portion in pressure contact with the regulating blade 24, but since the developing roller 22 is rotating during the image forming operation, this amount of deformation does not affect the deformation.

When the image forming apparatus is left in a stopped state for a long time, the developing roller 22 is deformed by the photosensitive drum 4 and the regulating blade 2
The deformation caused by No. 4 continues for a long time. In this state, even if the image forming apparatus is operated, the deformation of the developing roller remains and does not recover immediately.

If the developing action is started immediately, the developing roller 22 having the deformed portion will transfer the toner to the photosensitive drum 4, and the amount of thin layer of toner in the deformed portion of the developing roller 22 will be different from that in other portions. Become. If the photosensitive drum 4 is developed in such a state, the amount of the thin layer of the developing roller 22 will be partially non-uniform on the image, and horizontal stripes and other image density unevenness will occur with the circumferential length of the developing roller 24 as a pitch. Occur.

The above-mentioned deformation amounts d+ and dz of the developing roller 22 can be restored if left for a certain period of time. In an actual device, the developing roller is always in contact with the photoreceptor and the regulating blade and is under pressure, so if the developing roller 22 is rotated for a certain amount of time, it will be restored to its original state.

Restorability of this deformation is affected by temperature, and particularly in low-temperature environments, the restorability is significantly reduced.

In current image forming apparatuses, the amount of deformation of the developing roller is approximately 4
It is known that when the thickness is 0 μm or less, no significant unevenness occurs on the image. In other words, the amount of deformation of the developing roller is 40μ.
If it is not less than m, image unevenness will occur and the developing action cannot be performed.

In Fig. 4, if the amount of deformation, that is, the amount of strain is 0, and for example 40 μm is set as do, then the change in the amount of deformation with the passage of time after the pressing force is removed from the state of the deformed lid is shown as follows: At room temperature, the results shown by curve A are obtained, and at low temperatures of 10°C (the limit of the operating temperature of the machine), for example, the results shown by curve B are obtained. indicates the roller strain ld.

From the 4th time, after being left at room temperature, time is Ll, and at low temperature, time is t2.
As the process progresses, the deformation is restored to a state where it does not affect the image.

In an image forming apparatus, there is first a warm-up time before printing starts, such as heating of a fixing device. Therefore, the temperature of the atmosphere around the developing roller changes between when the power of the apparatus is turned on and after the worm amplifier.

Therefore, the temperature change during warm-up after the electric fXON and before the start of printing is detected by, for example, detecting the fixing temperature using a thermistor, etc., and the restorability is not good until the temperature reaches a predetermined temperature. Leave it as is;
After reaching a predetermined temperature, the developing roller is rotated. In FIG. 5, when the temperature is room temperature T, the ambient temperature changes as shown by straight line A after the power is turned on. In the case of low temperature T4, the ambient temperature changes as shown by straight line B.

In consideration of restorability, when the ambient temperature rises to a preset temperature T2, that is, point M of straight line A and straight line B
When the N point is reached, the developing roller is rotated.

In the figure, the horizontal axis represents time t, and the vertical axis represents temperature T.

The rotation of the developing roller has a deformation amount of at least d. During this time, no developing action is performed, that is, the state is maintained in such a state that printing cannot be started.

The rotation of the developing roller is set for a predetermined time in consideration of restoring the amount of deformation, and the developing roller continues to rotate during the fixed time t0, and printing cannot be started. At that time,
Once the time to has elapsed, the development operation, i.e. printing, can begin.

Even if the ambient temperature when the power is turned on is different, as long as the temperature at which the developing roller starts rotating is set to a predetermined temperature, the resiliency under that predetermined temperature will be the same, so If a certain period of time t0 is maintained as the developing roller rotation time, it is possible to avoid any influence on the image after that. That is, at the start of printing, the deformation of the developing roller is restored and the developing action can be performed in an optimal state.

If the time it takes to rotate the developing roller from temperature T2 is sufficient to restore the deformation of the developing roller until the standby temperature T3 set for the image forming apparatus is reached,
It is also possible to rotate the developing roller up to the standby temperature Tx without particularly setting the rotation time of the developing roller.

As shown in FIG. 5, the time when the developing roller starts rotating after the power is turned on is determined by temperature, but the ambient temperature at low temperature is set to the temperature T2, which is based on a low temperature which is an unfavorable condition.
Measure the time it takes for the temperature to reach T2 from when the power is turned on, and set a sufficient time tc from when the power is turned on until the temperature reaches T2.After the rotation is continued for a time 1c from the time when the power is turned on, the developing action, that is, printing can be started. It can be so. If the ambient temperature when the power is turned on is room temperature, the developing roller can sufficiently restore its deformation under this condition. However, since the developing roller will be rotated more than necessary, a time tc' that is sufficient to reach the temperature T2 in the case of normal temperature is set in advance, and in the case of normal temperature, the time t and l have elapsed since the power was turned on. The developing roller starts rotating after 1. It is also possible to start printing after the time rotation. Instead of to, the rotation time of the developing roller can be changed to until the standby temperature T is reached as described above.

〔effect〕

According to the present invention, the developing action is started after the partial deformation of the developing roller is restored to an allowable range, so there is no possibility that an excessive amount of toner will be deposited on the developing roller or a partial pressure change between the developing roller and the photosensitive drum will occur. It was possible to solve this problem and prevent the occurrence of image unevenness.

It is particularly effective in eliminating low-temperature background stains caused by partial toner adhesion at low temperatures.

[Brief explanation of the drawing]

FIG. 1 is an overall schematic diagram of an example of an image forming apparatus using the present invention, FIG. 2 is a diagram showing deformation caused by pressure contact of the developing roller against the photoreceptor, and FIG. 3 is a diagram showing deformation caused by pressure contact of the regulating blade. , FIG. 4 is a diagram showing the relationship between the standing time after pressure contact is released and the amount of deformation, FIG. 5 is a diagram showing the rotation control of the developing roller, and FIG. 6 is a diagram showing another embodiment of the rotation control of the developing roller. be. 4... Photoreceptor 22... Developing roller (and 1 other
Name) Figure 4 Figure 5 J Sail Sword Roller

Claims (1)

[Claims] (1) In a developing device of an image forming apparatus having a developing roller made of an elastic material for developing a latent image carrier, rotation of the developing roller is started after the ambient temperature of the developing roller reaches a predetermined temperature after power is turned on. A developing device for an image forming apparatus, characterized in that a developing action can be started after rotation has continued for a predetermined period of time.