JP2845281B2 - Image formation control method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an image forming control method applicable to an electrophotographic image forming apparatus.

[Related Art] Conventionally, various image forming control methods have been proposed and implemented.

For example, in the xerographic apparatus disclosed in Japanese Patent Publication No. 43-16199, a photoconductor is provided with a portion having a predetermined potential to perform development, the developed amount is optically detected, and toner supply control is performed. ing.

In the recording density control method disclosed in JP-A-59-87465, a reference density plate (e.g., provided on the back of the front end of a platen) is exposed and developed in the same manner as in a normal copy process.
It shows that the amount of development is optically detected and toner supply control is performed.

[Problems to be solved by the invention]

In the prior art described above, in the invention of Japanese Patent Publication No. 43-16199, although the developing ability is kept constant, it is necessary to provide a special portion having the reference potential of the photoreceptor. In the invention disclosed in Japanese Patent Application Laid-Open Publication No. H11-207, there is a problem that it is difficult to stabilize the developing ability when the potential of the photoconductor greatly changes.

Still another conventional technique also has a problem that the control is affected by the fluctuation of the potential of the photoconductor.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming control method capable of reducing a variation in control due to a variation in potential of an image carrier.

[Means for solving the problem]

The object is to create a reference latent image pattern on an image carrier,
An image forming control method of developing the reference latent image pattern with a developing device including a multi-stage developing roller to obtain a reference visual pattern, detecting the amount of toner adhered to the reference visual pattern, and controlling image forming conditions based on the detected value. In the above, the developing bias on the downstream side of the multi-stage developing roller is different from the developing bias on the upstream side during the development of the reference latent image pattern, and the amount of toner development on the downstream side is set to be larger than the amount of toner development on the upstream side. Achieved by means.

[Action]

When a reference latent image pattern is developed by a developing device including a multi-stage developing roller having several developing rollers, the developing bias on the downstream side of the multi-stage developing roller is different from the developing bias on the upstream side, and the amount of toner development on the downstream side is reduced. Since the developing amount is set to be larger than the toner development amount on the upstream side, the developing capability of the entire apparatus is temporarily reduced, so that control fluctuations due to potential fluctuations of the image carrier during detection of control data are reduced. In addition, since the developing amount of the toner of the downstream developing roller is larger than the developing amount of the toner of the upstream developing roller, the carrier around the reference visual pattern can be collected by the downstream developing roller.

〔Example〕

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

FIG. 1 is a configuration diagram of an embodiment of an image forming apparatus to which an image forming control method of the present invention is applied, wherein 1 is a photosensitive drum as an image carrier, 2 is a charging unit, 3 is an optical system, Is a developing unit including three developing rollers 4a, 4b, 4c, 5 is a toner replenishing unit, 6 is a sensor including a light receiving element 6a and a light emitting element 6b, 7 is a transfer unit, 8 is a charge removing unit, 9 is a cleaning unit, 10 Is a density detection circuit, 11 is a toner replenishment control circuit, 12 is a timing generation circuit, V _{B1 to} V _B3 are development bias portions of the development rollers 4a to 4c, and S ₁ and S ₂ are changeover switches.

In FIG. 1, a basic image forming method is known, in which light irradiating a document is incident on a photosensitive drum 1 via an optical system 3 to form an electrostatic latent image, and a developing roller of a developing unit 4 is formed. The toner images are sequentially visualized at 4a to 4c, and the image is transferred to the transfer paper by the transfer unit 7.

A reference latent image pattern for detection is formed in the non-effective image area of the photosensitive drum 1, and the reference latent image pattern is developed by the developing unit 4 to be a reference visible image pattern.
The light of 6b is irradiated. Then, the reflected light is received by the light receiving element 6a, and the amount of the received light is converted into an electric signal and input to the density detecting circuit 10. The signal output from the density detection circuit 10 enters the toner supply control circuit 11, and operates the toner supply unit 5 based on the control signal from the toner supply control circuit 11.

Upon detection by the sensor 6, the timing generating circuit 12, for changing the height of the developing bias voltage of the developing rollers 4 a to 4 c (potential), the changeover switch S _1, S ₂ of the developing bias unit V _B1 ~V _B3 Switch.

At the time of normal image formation, the changeover switches S ₁ and S ₂ enter the terminal a, and the voltage of the common developing bias portion _VB1 is applied to the developing rollers 4a to 4c.

When developing the reference latent image pattern, the selector switch
S ₁ and S ₂ enter the terminal b, and the developing rollers 4a and 4b are connected to the high-voltage developing bias portion _VB2 , and the downstream developing roller 4c
Is connected to a low-voltage developing bias section _VB3 .

FIG. 2 is an explanatory diagram showing the relationship between the voltage V _S of the conventional photosensitive drum and the amount of toner adhered on the photosensitive drum.

In the figure, A ₁ represents a development characteristic of the normal image formation, the developing bias unit V _B1 at that time was about 200V, I ₀ is the development characteristics of the target, I _1, I ₂ and the potential is changed The time characteristic is shown.

B ₁ is a developing characteristic at the time of developing the reference latent image pattern,
The sensor 6 controls the amount of toner attached to the reference latent image pattern (that is, the amount of toner attached to the reference visible image pattern) to be 0.4 mg / cm ² . That is 0.4mg / cm ² at the time less than,
A toner replenishment signal is output from the sensor 6 to the toner replenishment control circuit 11 via the density detection circuit 10, so that the toner adhesion amount of 0.4 mg / cm ² is always maintained. Developing bias voltage at this time was 500V, the potential of the reference latent image pattern on the photosensitive drum 1 is, if 800 V, is controlled to be P ₀ of FIG. 2.

In this state, the developing bias voltage during normal image formation is set to 20.
At 0V, P ₀ is shifted in parallel with the same slope and I ₀
Is obtained. However, when the potential of the reference latent image pattern is shifted within a range of 800V ± 100V, P ₁ ~P ₂ when B ₁
In the range.

Therefore, when normal image formation is performed by the above control method, the variation in toner density detection appears as it is, and the development characteristics vary between I _{1 and} I ₂ , resulting in a light image or a dark image.

In Figure 3 is an explanatory view showing a toner adhesion amount of the relationship on the photosensitive drum and the potential V _S of the photosensitive drum according to the present embodiment, the potential of the reference latent image pattern in the present embodiment is about 800 V,
800V to the developing bias unit V _B2, the developing bias unit V _B3 20
It is assumed that 0 V is applied.

In the figure, when the potential of the reference latent image pattern is 800 V,
It is controlled to be P ₀ ′ and compared to the slope of I ₀ of A ₁ ′
The slope of P ₀ ′ of B ₁ ′ is set to be small.
By setting the developing bias V _B1 = approximately 200 V to the developing rollers 4a to 4c during normal image formation, I ₀ ′ of the target characteristic can be obtained.

If the potential of the reference latent image pattern at the time of development is shifted by 800 V ± 100 V, the potential varies within the range of P ₁ ′ to P ₂ ′ of B ₁ ′. If this is the condition for normal image formation, compared to the slope of I ₀ of A ₁ ′
Since the slope of P ₀ ′ of B ₁ ′ is set to be small, the variation is in the range of I ₁ ′ to I ₂ ′ of A ₁ ′ as shown in FIG. a narrower range than ₁ ~I _2.

Next, the reason why the variation is partially overlapped with the above but the variation is reduced will be described in more detail with reference to FIGS. 2 and 3. FIG. Assuming that the photoconductor potential shifts by ± 100 V at B ₁ and goes from 700 V to 900 V around 800 V, the difference between the photoconductor potential and the developing bias potential (500 V) becomes 200 to 400 V, and the developing capacity is 0.4 mg / cm. ^{2 /400V~0.4mg/cm 2 /200V=1.0~2.0 -3} mg / c
Variations in the range of m ² / V, which correspond to P ₁ and P ₂ in FIG. Also, P ₁ and P ₂ correspond to I ₁ and I ₂ . Here, the photosensitive member potential is ± 100 V at B ₁ ′ with the developing bias potential at about 200 V.
Displacement, assuming that varies from 700V to 900V, the difference between the developing bias potential (200V) and the photosensitive member potential 500~700V, and the developability 0.4mg / cm ² /700V~0.4mg/cm ² /500V=0.57
A variation of about 0.80 × 10 ⁻³ mg / cm ² / V, which corresponds to P ₁ ′ and P ₂ ′ in FIG. When this is set to normal image forming conditions, the variations are I ₁ ′ and I ₂ ′, and the variation is P ₁ ′,
Although it is larger than P ₂ ′, it is smaller than conventional P ₁ and P ₂ .

Also, if the developing bias of the upstream developing rollers 4a and 4b is increased, the carrier may adhere to the low voltage portion around the reference latent image pattern, but the developing bias voltage of the downstream developing roller 4c is increased by the upstream. By lowering the developing bias voltage of the developing rollers 4a and 4b on the side and making the amount of toner adhered on the downstream side larger than the amount of toner adhered on the upstream side, the carrier once adhered can be collected.

In the above-described embodiment, several developing biases of the multi-stage developing rollers 4a to 4c are set to be substantially the same as the potential of the reference latent image pattern. The potential may be lower or higher than the potential of the reference latent image pattern within a range that is smaller than the toner development amount on the side.

In the above embodiment, the process using the positive photosensitive drum and the negative toner has been described. However, when the negative photosensitive drum and the positive toner are used, or the negative photosensitive drum and the negative toner are used. When used, a negative / positive process using a positive photosensitive drum and a positive toner can also be applied.

In order to reduce the variation in the control of the image forming conditions caused by the fluctuation of the potential of the photosensitive drum, which is the effect of the present embodiment, and to collect the carrier around the reference visible image pattern,
Although the developing bias of the downstream developing roller is set lower than the developing bias of the upstream developing roller so that the toner developing amount is larger than that of the upstream developing roller, in the positive / positive process, the developing bias of the downstream developing roller is reduced. And the developing bias on the downstream side is increased in the negative-positive process.

〔The invention's effect〕

As described above, according to the present invention, when developing the reference latent image pattern, the developing bias on the downstream side of the multi-stage developing roller is different from the developing bias on the upstream side, and the amount of toner development on the downstream side is Since the setting is made to be larger than the amount, the image forming conditions are not affected by the fluctuation of the potential of the image carrier, unnecessary carriers can be collected, and the image forming conditions can be accurately detected. A control method can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an image forming apparatus to which the image forming method according to the present invention is applied, and FIGS. 2 and 3 show the relationship between the potential of the photosensitive drum and the amount of toner adhering on the photosensitive drum. FIG. 1 image carrier (photosensitive drum), 4a, 4b, 4c developing roller, 6 sensor, 10 density detection circuit, 11 toner supply control circuit, _VB1 , _VB2 , _VB3 ... Developing bias section.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G03G 15/00 303 G03G 13/08 G03G 15/08-15/08 507 G03G 13/09 G03G 15/09 G03G 13/06 G03G 15/06-15/06 102

Claims (1)

(57) [Claims] 1. A reference latent image pattern is formed on an image carrier, and the reference latent image pattern is developed by a developing device including a multi-stage developing roller to form a reference visual pattern, and a toner adhesion amount of the reference visual pattern is detected. In the image forming control method of controlling the image forming condition from the detected value, the developing bias on the downstream side of the multi-stage developing roller is different from the developing bias on the upstream side during the development of the reference latent image pattern, and the toner on the downstream side is developed. An image forming control method, wherein a development amount is set to be larger than an upstream toner development amount.