JP2856427B2 - Development control method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a development control method for supplying toner to an electrostatic latent image formed on a latent image carrier to perform development.

2. Description of the Related Art In general, in various image forming apparatuses such as a copying machine, a printer, and a facsimile, an electrostatic latent image corresponding to an image is formed on a latent image carrier such as a photoconductor, and the electrostatic latent image is formed. For example, a one-component developer is supplied from a toner carrier provided in the developing device to perform development, whereby a visible image is obtained.

Such a one-component developer (hereinafter simply referred to as toner)
Is formed in a roller shape or the like, and is cyclically conveyed at a predetermined cycle while holding the toner on the surface, and executes a predetermined development process in a development area. That is, for the toner carrier, a toner replenishing member also formed in a roller shape or the like is provided in contact with the developer replenishment area, and a developing member formed on the downstream side of the developer replenishment area. A toner thinning regulating means formed in a blade shape or a roller shape or the like in the developer thinning region is provided in contact with the toner thinning region. The toner is replenished to the toner carrier by the action of the replenishing member, whereby the toner adheres to the surface of the toner carrier. Further, the toner attached on the surface of the toner carrier is uniformly thinned in the developer thinning region by the leveling action of the toner thinning regulating means. The uniformly thinned toner thin layer is sent to a developing area formed downstream of the developer thinning area, where toner is selectively supplied to the electrostatic latent image to perform a developing operation. It is supposed to be.

On the other hand, when the toner carrier is formed from a conductive member, toner tends to be excessively attached to a solid image as compared with a line image, and a good image tends not to be obtained. In order to solve the problem, the conductive member of the toner carrier is covered with a dielectric layer, a resistor layer or an insulating layer to thereby weaken a developing electric field in the solid image area (an electric field acting on the toner in the developing area). Attempted.

[Problems to be Solved by the Invention] However, when a dielectric layer, a resistor layer, or an insulating layer is provided on the toner carrier as described above, accumulation of electric charge on the surface of the toner carrier or variation in the charge amount of toner particles may occur. As a result, the surface potential of the toner carrier varies, which changes the developing characteristics.

As means corresponding to a change in development characteristics, there are means described in, for example, JP-A-54-112635 or JP-A-54-115250. These conventional means are:
The potential of the toner layer on the toner carrier and the potential of the background portion of the photoreceptor are measured, and control is performed so as to keep the relationship between the two constant. However, when a dielectric layer, a resistor layer, or an insulating layer is provided on the toner carrier as described above, it cannot be employed because the toner layer potential itself cannot be directly measured.

In order to solve this problem, the inventor of the present application measures the change in the surface potential of the toner carrier for one period of conveyance one by one, and controls the bias voltage value applied to the toner carrier based on the measurement result. It has already been proposed that the surface potential of the toner carrier in the development area is kept constant by this.

However, according to such a proposed means, the development characteristics can be kept constant even when a dielectric layer, a resistor layer or an insulating layer is provided on the toner carrier. When minute potential unevenness of the carrier surface potential occurs or minute potential variation due to noise is included in the measurement potential, the minute potential variation causes unnecessary variation in the bias applied to the toner carrier. And inconvenience in control is caused. Here, the charge unevenness of the toner layer is such that the toner layer formed on the surface of the toner carrier does not have a uniform thickness because the toner particle diameter has a predetermined distribution and the arrangement is random. It is believed that it occurs because it does not have a uniform charge.

Therefore, the present invention prevents the above-described fluctuation of the development characteristics from occurring even when the surface potential of the toner carrier is slightly fluctuated in a cycle shorter than the transport cycle of the core toner carrier, thereby achieving good development. It is an object of the present invention to provide a development control method capable of maintaining characteristics.

Means for Solving the Problems In order to achieve the above object, the present invention provides a method in which a toner carrier holding toner on its surface is cycle-conveyed at a predetermined cycle, and the toner on the surface of the toner carrier is regulated in a toner layer. Means for performing a predetermined development step in a development area where the latent image carrier and the toner carrier are opposed to each other. A potential measuring unit arranged at a potential measuring position facing the toner carrier upstream of the latent image carrier in the rotation direction of the toner carrier is used to satisfy the transfer cycle of the toner carrier. The surface potential of the toner carrier that fluctuates in a non-periodic cycle is measured, the measured value is sampled, and the sampled surface potential measurement is smoothed. A bias voltage value to be newly applied is obtained based on a deviation between the smoothed surface potential measurement value and the bias voltage value currently applied to the toner carrier, and based on the obtained bias voltage value, The bias voltage applied to the toner carrier is delayed from the current time by the movement time from the potential measurement position to the development region so that the surface potential in the development region of the toner carrier is maintained constant. It has a configuration for adjusting and controlling.

[Operation] In the means having such a configuration, even if a minute potential fluctuation is included in the measured potential, it is smoothed and compared, so that the fluctuation of the applied bias voltage can be suppressed. ing.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

First, an example of a developing device for carrying out the present invention will be described with reference to FIG. A developing roller 3 as a toner carrier is pivotally supported in the developing unit 2 of the developing device 1. The developing roller 3 is arranged so as to elastically contact the surface of the photosensitive drum 4 in a developing area. ing. The photoreceptor drum 4 and the developing roller 3 are driven to rotate in opposite directions indicated by arrows A and B, that is, in the same direction at a contact portion between the two, and a developing region where a developing operation is performed is formed at the concave contact portion Are formed as described above.

In the developing roller 3, as shown in FIG. 2 in particular, a conductive rubber having a thickness of about 6 mm made of silicone rubber mixed with carbon around a support 3 a formed of a conductive cored bar. The conductive elastic layer 3b is mounted, and furthermore, about 200 μm of a silicone resin obtained by mixing a small amount of carbon on the conductive elastic layer 3b
A thick high-resistance conductive particle-dispersed resin layer 3c is applied.
The provision of the conductive elastic layer 3b makes uniform contact with the photosensitive drum 4, and the provision of the high-resistance conductive particle dispersed resin layer 3c appropriately controls the electric field intensity in the development region. It has become.
A predetermined developing bias voltage is applied to such a support 3a of the developing roller 3 from a bias power supply circuit described later.

The developing unit 2 is provided with a toner hopper as a toner storage unit, and a toner as a toner replenishing means for replenishing new toner (negatively charged toner) stored in the toner hopper to the surface of the developing roller 3. The replenishing roller 5 is rotatably driven in a direction indicated by an arrow C and is supported in the developing unit 2. The toner replenishing roller 5 is formed of a roller member made of urethane foam, is disposed so as to be in contact with the surface of the developing roller 3, and a developer replenishing area is formed at the contact portion. A predetermined toner supply bias is also applied to the toner supply roller 5 from a bias power supply circuit described later.

Further, a toner layer regulating blade 6 as a toner thinning means for forming a layer of the toner supplied to the surface of the developing roller 3 is disposed in a downstream region of the toner replenishing roller 5 in the rotation direction of the developing roller 3. I have. The leading edge of the toner layer regulating blade 6 is
Are arranged so as to be uniformly contacted in the axial direction with respect to the surface thereof, and a developer thinning region is formed at the contact portion.

Further, a probe 7a of a surface voltmeter 7 is provided on the downstream side of the toner layer regulating blade 6 in the rotation direction of the developing roller 3 so as to measure the surface potential of the developing roller 3 after the thin layer of toner is formed. Is provided. The probe 7a of the surface voltmeter 7 is arranged so as to be close to the surface of the developing roller 3, and a detection output from the surface voltmeter 7 is output to a first difference circuit 9 via an arithmetic circuit 8. The voltage value of the developing bias applied to the developing roller 3 at the developing point is input to the first difference circuit 9, and the measured value of the measured surface potential of the developing roller 3 is actually applied. The deviation from the voltage value of the developing bias is calculated by the first difference circuit 9.

The arithmetic circuit 8 is provided with an integrating circuit so that a measured value of the surface potential of the developing roller 3 measured during a certain period of time is sampled and smoothed. The smoothed value is output to the first difference circuit 9 as a measured value of the surface potential of the developing roller 3.

Further, the deviation signal output from the first difference circuit 9 is applied to a delay circuit 11 formed by a delay element such as a CCD. The delay circuit 11 has a function of delaying the output from the first difference circuit 9 by the movement time t from the potential measurement position to the development area and issuing the output to the second difference circuit 12. In the second difference circuit 12, the deviation which is the output of the first difference circuit 9 is subtracted from the output value from the reference bias power supply 13, and this is applied to the developing roller 3 as the final bias voltage. A bias voltage for toner replenishment, which is obtained by further adding a voltage from the power supply 14 to the final bias voltage applied to the developing roller 3, is applied to the toner replenishing roller 5.

In the developing device 1 in such an embodiment, first, exposure writing is performed on the uniformly charged surface of the photosensitive drum 4 to form an electrostatic latent image corresponding to an image. The developing roller 3 of the developing device 1 selectively supplies toner to the electrostatic latent image in a developing area, whereby the electrostatic latent image is developed to obtain a visible image. The developing roller 3 is replenished with new toner in the toner hopper by the toner replenishing roller 5 in the developer replenishing area, and the toner attached on the surface of the developing roller 3 is removed from the developer thinning area. In this case, the toner layer regulating blade 6 uniformly reduces the thickness of the toner and sends it to the developing area.

At this time, the surface potential of the developing roller 3 including the toner layer fed into the developing area is measured by the probe 7a of the surface voltmeter 7, and an appropriate developing bias corresponding thereto is applied to the developing roller 3 as follows. You.

For example, the toner supply roller 5 or the photosensitive drum 4
The surface layer of the developing roller 3 is charged by the contact between the developing roller 3 and the developing roller 3, and the surface potential of the developing roller 3 including the toner layer is changed as shown in FIG.
It may be changed in a time longer than the time required for one rotation of. In this case, the difference between the surface potential of the developing roller 3 output from the first difference circuit 9 and the voltage value of the developing bias is transmitted to the second difference circuit 12 through the delay circuit 11, and the second difference circuit 12 The deviation, which is the output of the first difference circuit 9, is subtracted from the output value from the reference bias power supply 13, and this is applied to the developing roller 3 as a final bias. As a result, the developing bias is properly corrected so that the surface potential in the developing region of the developing roller 3 is kept constant.

Further, when the surface potential of the developing roller 3 including the toner layer is changed according to the rotation cycle of the developing roller 3 as shown in FIG. 4 based on the potential change due to uneven thickness of the surface portion of the developing roller 3 or the like. The surface potential measurement value of the developing roller 3 within a predetermined rotation time set at least at least one rotation of the developing roller 3 is sampled, and the surface potential measurement value of the developing roller 3 including the sampled toner layer is measured. , Is smoothed by an integrating circuit provided in the arithmetic circuit 8. The smoothed value is output to the first difference circuit 9 as a measured value of the surface potential of the developing roller 3. Thus, similarly, the correction of the developing bias is appropriately performed so that the surface potential in the developing area of the developing roller 3 is maintained constant.

Furthermore, as shown in FIG. 5, the measured potential includes minute potential unevenness or minute potential variation in the surface potential of the developing roller 3 due to the unevenness of the toner layer due to the above-described toner particle size distribution or noise. There is. In this case, the developing roller 3 within a predetermined minute time is
Is measured, and the measured surface potential value of the developing roller 3 including the sampled toner layer is smoothed by the integration circuit provided in the arithmetic circuit 8. The smoothed value is used as a measured value of the surface potential of the developing roller 3 by the first difference circuit 9.
, Whereby the correction of the developing bias is appropriately performed similarly.

As described above, in the present embodiment, even if a minute potential variation is included in the measured potential, it is smoothed and subjected to the comparison processing. Thus, unnecessary variation in the applied bias voltage can be suppressed, and the bias voltage can be suppressed. The voltage control operation is performed smoothly.

When the potential fluctuations shown in FIGS. 3, 4, and 5 are combined, the above-described control operations are executed in combination, whereby the appropriate developing characteristics are constantly maintained. You can get it.

Further, the developing roller 23 in the embodiment shown in FIG. 6 in which the same components as those in the embodiment shown in FIG. 1 are denoted by the same reference numerals, as shown in FIG. A medium-resistance elastic layer 23b is mounted around a support 23a formed of a cored bar, and a surface coating layer is further applied on the medium-resistance elastic layer 23b. Then, two surface voltmeters 7 are used to measure the surface potential of the developing roller 23 after the thin layer of toner is formed.
And 17 are provided. These two surface electrometers 7
The probes 7a and 17a are arranged at a predetermined interval from each other and are close to the surface of the developing roller 23. Distance between the probe 7a provided on the probe 17a and the downstream side is provided on the upstream side, with is set to a distance that requires t ₁ at a moving speed of the developing roller 23, the downstream side of the probe 7a development the distance between the areas is set to a distance required to t ₂ at a movement speed of the developing roller 23.

In such an embodiment, the decay rate is obtained from the two surface voltmeters 7 and 17 for the developing roller 23 having a medium resistance type time constant, and the distance between the developing area and the measurement point is taken into consideration. The bias control is performed while being performed. As a result, the control operation is performed smoothly as in the above embodiment.

When copying the transfer paper continuously, it is possible to stably control the bias applied to the developing roller over time by measuring the surface potential between the transfer papers.

[Effects of the Invention] As described above, according to the present invention, even if a minute potential fluctuation is included in the detected surface potential of the toner carrier, the control of the applied bias voltage is performed without being affected by the minute potential fluctuation. Sampling and smoothing the detected value of the surface potential of the toner carrier measured within a predetermined time before the developing process, and calculating the deviation between the smoothed measured surface potential value and the bias voltage value at the present time. A bias voltage value to be newly applied is calculated based on the calculated bias voltage value. From the obtained bias voltage value, the potential from the potential measurement position to the development region is adjusted so that the surface potential in the development region of the toner carrier is kept constant. The bias voltage applied to the toner carrier is adjusted and controlled by delaying from the time when the voltage value is obtained by the moving time until the bias voltage is applied. Unnecessary fluctuation control can be suppressed, and even when the surface potential of the toner carrier is fluctuated in a minute cycle, development characteristics can be stabilized while suppressing unnecessary bias fluctuation, and toner It is also possible to keep the surface potential in the development area of the body constant.

[Brief description of the drawings]

1 is an explanatory longitudinal sectional view showing an example of a developing device for carrying out the present invention, and FIG. 2 is a partially enlarged longitudinal sectional view showing a structure of a toner carrier provided in the developing device in FIG. FIG. 3, FIG. 4, FIG. 5 and FIG. 5 are diagrams showing the fluctuation state of the toner carrier surface potential, and FIG. 6 shows another example of a developing device for carrying out the present invention. FIG. 7 is a partially enlarged longitudinal sectional view showing the structure of a toner carrier provided in the developing device in FIG. Reference Signs List 1 developing device 3,23 developing roller 4, photosensitive drum 7,27 surface voltmeter 7a, 27a probe 8,
…… Operation circuit, 9,12 …… Difference circuit, 11 …… Delay circuit.

Continuation of front page (56) References JP-A-60-79370 (JP, A) JP-A-61-228468 (JP, A) JP-A-1-109365 (JP, A) JP-A-54-112635 (JP, A) JP-A-54-115250 (JP, A) JP-A-58-121050 (JP, A) JP-A-58-121051 (JP, A) JP-A-58-121052 (JP, A) 58-68056 (JP, A) JP-A-2-230270 (JP, A) JP-A-58-172654 (JP, A) JP-A-59-2062 (JP, A) JP-A-59-133571 (JP, A) A) JP-A-59-157663 (JP, A) JP-A-59-133572 (JP, A) JP-A-1-276169 (JP, A) JP-A-55-43563 (JP, A) JP-A Sho-63 -23171 (JP, A) JP-A-62-118267 (JP, A) JP-A-63-200168 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 15/06- 15/095 G03G 15/00 303

Claims (1)

(57) [Claims] A toner carrier holding toner on its surface is cycle-conveyed at a predetermined cycle, and the toner on the surface of the toner carrier is thinned by a toner layer regulating means to form a latent image carrier and a toner carrier. And a development control method in which a predetermined development process is performed in a development region opposed to the developing region, wherein between the development region and the toner layer regulating unit,
Using a potential measuring means disposed at a potential measuring position facing the toner carrier upstream of the latent image carrier in the rotation direction of the toner carrier, at a cycle shorter than a transport cycle of the toner carrier. The fluctuating surface potential of the toner carrier is measured, the measured value is sampled, the sampled surface potential measurement is smoothed, and the smoothed surface potential measurement and the current toner carrier A bias voltage value to be newly applied is calculated based on a deviation from the bias voltage value applied to the toner carrier. Based on the obtained bias voltage value, the surface potential in the developing region of the toner carrier is kept constant. As described above, the toner is applied to the toner carrier with a delay from the current time by the moving time from the potential measurement position to the development area. Development control method characterized by a bias voltage so as to adjust and control that.