JPH06348135A - Toner supply control method - Google Patents

Abstract

PURPOSE:To provide an accurate reference value for toner density control and accurately control toner supply based on it. CONSTITUTION:The toner mixing ratio of a developer stored in a developing device 4 is measured, and toner is supplied to the developing device 4 from a toner supply device 7 when the toner mixing ratio is the prescribed threshold value or below in this toner supply control method. The developer adjusted to this threshold value (starter) is loaded in the developing device 4, the mixing ratio of the developer is measured by a toner density measuring means 48, and toner supply is controlled based on this measured value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method for supplying toner to a developing device using a two-component developer composed of toner and carrier.

[0002]

2. Description of the Related Art Generally, in an image forming apparatus such as a copying machine or a printer using an electrophotographic method, a developing device using a two-component developer consisting of toner and carrier, a developing device newly placed in an empty developing device. The toner charge amount of the agent shows a higher value or a lower value than the original charge amount (saturated triboelectric charge amount). This is due to insufficient triboelectrification of the toner and the carrier due to rotation of the developer stirring means arranged in the developing device. Then, for example, when the toner charge amount is higher than the original charge amount, the electrostatic attraction force between the toner and the carrier is strong, and if the development is performed in this state, the image density is lowered.

Therefore, when a new developing device is used or the developer in the developing device is replaced, in order to stabilize the image density, the toner density of the initial developer (toner weight / toner weight /
The developer weight) is forcibly increased to a predetermined high density value, thereby weakening the electrostatic attraction force of the toner and the carrier to optimize the image density, and the developer adjusted to the above high density value is The toner concentration detection sensor detects the toner concentration, and the subsequent toner concentration control is performed based on the relationship between the sensor output and the toner concentration at this time.

Explaining with a specific example, for example, if the original charge amount is, the toner concentration is 5 wt% (toner: 5 w
In a developing device designed to obtain an optimum image density at t%, carrier: 95 wt%, first, a developer having a toner concentration of 5 wt% (hereinafter, this developer is referred to as "starter").
Say. ) Is loaded in the developing device, and then the toner replenishing device is driven for a predetermined period of time to replenish toner to the developing device to adjust the toner concentration of the developer to 8 wt%. Then, the toner concentration detection sensor detects a toner concentration of 8w.
Toner concentration is controlled so that the toner concentration is 5 wt% by detecting t% of the developer and using the output at that time as a reference value.

[0005]

However, in the above toner concentration control method, since the toner replenishing amount per unit time of the toner replenishing device is not necessarily accurate, the toner concentration of the developer adjusted to a high concentration is true. It is not always 8% by weight. Further, the output-toner concentration characteristics are slightly different depending on the sensor, and even if the output value is 8 wt% and a proper output value, the output value at 5 wt% may vary.
Therefore, there is a problem that the toner density of the developer varies.

[0006]

The present invention has been made to solve the above problems, and measures the toner mixing ratio of the developer accommodated in the developing device, and the toner mixing ratio is set to a predetermined threshold value. In the following case, in the toner replenishment control method of replenishing toner to the developing device from the toner replenishing device, the developer adjusted to the above threshold value is loaded into the developing device, and the mixing ratio of the developer is measured by the toner concentration measuring means. The toner replenishment is controlled based on the measured value.

[0007]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In FIG. 1, reference numeral 1 denotes an image forming unit. The image forming unit 1 integrally includes a frame 2 with a photoconductor 3, a developing device 4, a cooling device 5, and a recycling device 6, and is used for a copying machine, a printer, or the like (not shown). It is detachable from the image forming apparatus.

The developing device 4 is provided with a housing 40, and an upper cover 41 is openable and closable. A housing portion 42 that opens toward the photoconductor 2 is formed on the photoconductor 2 side of the honing 40, and a developing roller 43 is housed in the housing portion 42. The rear portion of the housing portion 42 (see FIG.
On the left side), a first transport path 44 and a second transport path 45 are sequentially formed, and developer transport members 46 and 47 are housed in the respective transport paths. At the bottom of the first transport path 44, a toner concentration detecting sensor 48 for measuring the ratio of toner to carrier from the magnetic permeability of the developer is provided.
The output of 8 is output to the control device 8.
One end of the second transport path 45 is connected to the toner replenishing device 7, and the toner is replenished from the toner replenishing device 7 to the second transport path 45. Also,
The second transport path 45 is connected to the cleaning device 5 via the recycling device 6, and the toner collected by the cleaning device 5 is sent to the second transport path 45.

When the image forming unit 1 having the above-mentioned structure is mounted on the image forming apparatus, first, the upper cover 41 of the developing device 4 is opened, and the starters are loaded in the conveying paths 44 and 45 (S1). This starter has a certain ratio of toner and carrier, such as 5 wt% toner and 95 wt% carrier.
It is mixed in the ratio of. In addition, this loading work is
When using the developing device 1 shipped from the factory for the first time,
Alternatively, it is performed when the dealer collects the developing device 1 used for a certain period of time, discards the deteriorated developer and replaces it with a new developer.

Next, the developing device 1 is mounted on the main body of the image forming device, and the photoconductor 2, the developing device 4, the recycling device 6 and the like are drivingly connected to the drive system of the image forming device. Further, the toner supply device 7 is connected to the second transport path 45. Then, the toner density (T / C) threshold setting mode input device 81 provided in the image forming apparatus is started to select the toner density threshold setting mode (S2), and the print switch 82 provided in the image forming apparatus main body is turned on. (S3). In the normal state, when the print switch 82 is turned on, the image forming apparatus starts the image forming operation. However, when the print switch 82 is turned on for the first time after the toner density threshold setting mode is selected, the paper feeding of the image forming apparatus is performed. The system, the optical system (not shown), etc. do not operate, and only the developing device 1 and the photoconductor 2 are driven (S4).

Subsequently, the timer T1 is started to drive the developer transport members 46 and 47 to uniformly mix the starters contained in the first transport path 44 and the second transport path 45.
The starter of the transport path 44 is supplied to the developing roller 43, and the starter is transported to the facing portion of the photoconductor 2 based on the rotation of the developing roller 43, but an electrostatic latent image is formed on the outer periphery of the photoconductor 2. It is not formed and the toner is not consumed.

Next, when it is determined that the timer T1 has expired (S6), the toner concentration detection sensor 48 detects the toner concentration of the starter, and the detected value is stored in a storage device of the control device 8, such as a RAM (not shown). It is stored (S7). At this stage, the toner is not consumed and the toner concentration detection sensor 48
The output of 1 corresponds to the toner density of the starter. For example, if the toner concentration of the starter is 5 wt%, this value and the output of the toner concentration detection sensor 48 that has detected it correspond one-to-one.

Then, when the toner concentration detection processing of the starter is completed, the toner replenishing device 7 is driven to start the second replenishment.
Toner is supplied to the transport path 45 (S8). At the same time, the photoconductor 1 and the developing device 4 are driven. Further, the timer T2 is started to uniformly mix the toner supplied to the developing device 4 with the starter (S9). At this time, the paper feeding system and the optical system are maintained in a non-operating state.

The setting time of the timer T2 is set to a time capable of compensating for the decrease in the initial image density which occurs when the image formation is started only by the starter due to the toner amount replenished during this setting time. Specifically, when it is necessary to increase the toner concentration of the starter (toner concentration: 5 wt%) to 8 wt% in order to compensate for the decrease in the initial image density and obtain an image of appropriate density, Toner density 3
It is set to the drive time of the toner replenishing device 7 required for increasing the wt%. That is, the amount of toner replenished by one rotation of the toner replenishment motor 71 is measured in advance, and the absolute amount of toner required to increase the toner concentration in the developing device 4 by 3 wt% is replenished by the above-mentioned one replenishment. The number of revolutions divided by the amount is calculated, and the time required for the revolution is calculated by the timer T2.
Set the time.

When it is determined that the timer T2 has ended (S10), the toner replenishing device 7, the photoconductor 2 and the developing device 4 are
Is stopped and the initialization of the control device 8 is completed.

After that, when a normal image forming process is started, the developing device 4 starts development with the developer whose toner concentration is adjusted to 8 wt%. Therefore, the decrease in image density due to unstable charging at the initial stage of development is eliminated, and an image with an appropriate density can be obtained. However, the unstable charging state of the developer is gradually eliminated as the developer is consumed, and the toner concentration of the developer settles down to 5 wt% when a certain amount of toner is consumed.

The control device 8 also calculates the toner concentration based on the output of the toner concentration detection sensor 48, and controls the drive of the toner replenishment motor 71 so as to maintain the toner concentration at 5 wt%. That is, a toner concentration of 5 wt% is used as a replenishment threshold for whether or not to replenish toner, and when the toner concentration falls below the replenishment threshold, the toner replenishing device 7 is driven for a predetermined time to replenish toner to the developing device 4. Here, the value of the reference toner concentration to be controlled: 5 wt% is stored with reference to the output of the toner concentration detection sensor 48 for the starter that is properly adjusted, so that the toner concentration is controlled extremely accurately, and the toner charge amount Image formation is performed even in the stable period under optimum toner concentration conditions.

It is not necessary to replenish the toner with a toner concentration of 5 wt% immediately after the processing of (S11) is completed, and for example, the rotation time of the photoconductor 2 or the developing roller 61 may be changed after the completion of (S11). It is also possible to start a counting counter and prohibit the driving of the toner replenishing device 7 unless the counter detects that development has been performed for a certain period of time. Here, the fixed time counted by the counter is assigned based on the result measured in advance as the time during which the unstable period of the toner charge amount is eliminated by the stirring of the developer transport members 46, 47 and the like. It is configured that the control device 8 issues a toner replenishment signal at the output of the toner concentration detection sensor 48 corresponding to the toner concentration of 5 wt% from the time when the time has elapsed.

[0019]

As is apparent from the above description, in the present invention, the developer adjusted to the control threshold of the toner mixing ratio is loaded into the developing device, and the mixing ratio is measured by the toner mixing ratio measuring means, Since the subsequent toner density control is performed with the measured value as a reference, the reference value of the toner density control is accurate, and the toner replenishment control based on that is accurate.

[Brief description of drawings]

FIG. 1 is a sectional view of an image forming unit.

FIG. 2 is a flowchart showing an adjustment procedure of a toner density detection sensor.

[Explanation of symbols]

1 ... Image forming unit, 4 ... Developing device, 7 ... Toner supply device, 48 ... Toner density detection sensor.

Claims (1)

[Claims] 1. A toner replenishment control method for measuring a toner mixing ratio of a developer housed in a developing device, and replenishing the developing device with toner from the toner replenishing device when the toner mixing ratio is equal to or less than a predetermined threshold value. A toner replenishment characterized in that a developer adjusted to the above threshold value is loaded into a developing device, a mixing ratio of the developer is measured by a toner concentration measuring means, and toner replenishment is controlled based on the measured value. Control method.