JPH03202878A - Toner concentration sensor - Google Patents

Abstract

PURPOSE:To maintain appropriate level of toner concn. by controlling a travel means based on judgement for the time of exchange of a protective sheet by a judging means. CONSTITUTION:The detecting surface 11 of a toner concn. sensor 10 is covered with the protective sheet 12a. The sheet 12a is formed in film shape, and is suspended between a rewind roller 16 and a delivery roller 17, and is sent out sequentially, and is exchanged with a new sheet 12a. The time of exchange of the sheet 12a is decided by counting the number of times of copying with the judging means 13 and send a signal to a control means 14. Then, a motor 15 that is the travel means is rotated with the command of the control means 14. Thereby, rollers 17, 18 are rotated, and the sheet is exchanged with the new sheet 12a, therefore, the toner concn. can be accurately detected, and the appropriate level of toner concn. can be maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a toner concentration sensor that detects the toner concentration of a developer.

[Prior Art] Generally, in an image forming apparatus such as a copying machine, a latent image is formed on the surface of a photoreceptor, this latent image is developed with toner in a developing device, and then transferred to paper. It is fixed on the paper. Among these, in the developing step, as the number of times of development increases, the toner concentration in the developer decreases. If development is performed while this toner density has decreased, the image density will decrease.

Therefore, the toner concentration is detected and toner is replenished to maintain an appropriate toner concentration. A means for detecting this toner concentration is a toner concentration sensor.

This toner concentration sensor usually uses a photosensor or detects the toner concentration as a change in the inductance of a detection coil. In either of these two types, there is a problem that as the number of times of development increases, the detection surface of the toner density sensor becomes scratched or has toner attached to it, making accurate detection impossible. Therefore, JP-A No. 6
Japanese Patent No. 1-67065 discloses a technique of coating the detection surface of a toner concentration sensor with an antistatic agent.

[Problems to be Solved by the Invention] However, even if this sensing surface is coated with an antistatic agent, it may become scratched due to the increased number of times of development.
There was a problem in that it was not possible to completely prevent toner from adhering, and as a result, accurate toner concentration could not be detected, making it difficult to maintain an appropriate toner concentration.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a toner concentration sensor that can maintain an appropriate toner concentration.

[Means for Solving 5M] The present invention provides a toner concentration sensor that detects the toner concentration of a developer, and includes a determining means for determining the replacement time of a protective sheet provided on a toner concentration detection surface, and The present invention is characterized by comprising: a moving means for moving the vehicle; and a control means for controlling the moving means based on the determination result of the determining means.

[Function] In the present invention, the determining means determines when to replace the protective sheet provided on the toner concentration detection surface, and the controlling means controls and moves the moving means for moving the protective sheet based on the result of this determination. Even if the protective sheet on the density sensing surface is scratched or toner adheres to it, a new protective sheet will cover the toner density sensing surface and accurate toner density can be obtained.

[Examples] The present invention will be described below with reference to drawings showing examples thereof.

FIG. 1 is a schematic sectional view of a developing device using a toner concentration sensor according to an embodiment of the present invention.

In FIG. 1, a toner replenishing roller 2 for replenishing toner is provided obliquely above the developing device l. An agitating roller 4 is provided below the toner replenishing roller 2 to agitate the developer X sent back from the partition plate 3 and the toner from the toner replenishing roller 2 . A supply roller 5 that supplies the developer X stirred by the stirring roller 4 to the developing roller 6 is provided closer to the photoreceptor 7 than the stirring roller 4, and the developing roller 6 is disposed close to the photoreceptor 7. I'm being kicked. At the upper part of the developing device l, there is a spike plate stay 8.
, a developing slit plate 9, and a toner concentration sensor 1O.

The detection surface If of this toner concentration sensor IO is protected by a protective sheet).
12a. This protective sheet 12a is in the form of a film, and includes a winding roller 16 and a winding roller 1.
The protective sheet 12a is installed between the protective sheets 12a and 12a, and is changed into a new protective sheet 12a by being sent out one after another. In addition, in FIG. 1, the protective sheet 12a is fed in the vertical direction (direction toward the photoconductor), but as shown in FIG. A structure including a protective sheet 12b may also be used.

The protection sheet 12 has a shape of ζ, and is not only a band-shaped sheet 12a as shown in FIG. 1, but also a disk-shaped sheet 12c as shown in FIG. 12d.

When a photosensor is used as the toner concentration sensor IO, a light-transmitting material is preferable, and a non-light-transmitting material may be used for a toner concentration sensor that measures changes in the inductance of a detection coil. As a specific material, a polyester film can be considered.

The determining means 13 is a means for determining when the protective sheet 12 provided on the toner concentration detection surface 11 should be replaced. Specifically, the determining means 13 is a counter that counts the number of copies. For example, when the number of copies has reached 1000, a signal is sent to the control means 14. Alternatively, for example, by pressing a copy start switch on an operation section (not shown), it may be determined that it is time for replacement, and a signal may be sent to the control means 14.

The moving means 15 is a means for moving the protection sheet 12, and is specifically a motor 15. For example, when the protective sheet 12 is a band-shaped protective sheet 12a as shown in FIG. 1, the motor 15 is rotated in response to a command from the control means 14 so as to wind up the protective sheet 12a by a predetermined length.

Further, for example, if the protective sheet 12 is disk-shaped, the motor 15 may be rotated by a predetermined angle.

The control means 14 controls the moving means based on the judgment result of the judgment means 13, and is specifically a microcomputer built into an image forming apparatus or the like that uses a developing device. In addition, without using a microcomputer,
You may respond by turning off a predetermined electrical circuit.

Next, while referring to the schematic sectional view of the developing device shown in FIG.
The operation of the toner concentration sensor according to the present invention will be explained.

First, when the counter 13 serving as the determining means 13 counts a predetermined number of copies, for example 1000 copies, the counter 13 sends a signal to the microcomputer 14. The microcomputer 14 thereby rotates the motor 15 serving as the moving means 15, and moves the protective sheet 12a by a predetermined length. Due to this movement, the detection surface 11 of the toner concentration sensor 10 becomes a clean detection surface 11 without any scratches or toner. The toner density sensor 10 causes the toner replenishment roller 2 to replenish toner when the detected density is low, and does not replenish toner when the density is appropriate.

Further, as another embodiment, when the protective sheet 12b is fed in the axial direction of the developing roller 6 shown in FIG. 2, the operation is the same as that in FIG. 1. That is, the winding roller 16 winds up the protective sheet 12b as the motor 15 rotates, and the driven roller 17 rotates in accordance with this winding.

Subsequently, as another example, the protection sheet) 12 is
The operation when the disk is shaped as shown in FIG. 2 will be explained.

In this case as well, when the counter 13 counts the number of copies and reaches a certain value, for example 1000 copies, it sends a signal to the computer 14, which in turn controls the motor 15.
The same is true for rotating. However, the motor 15 does not rotate once, but rotates at a predetermined angle, for example, at an angle A as shown in FIG.
Rotate only.

As a result, the detection surface 11 of the toner concentration sensor 10 is covered with a new protective sheet 12c.

Next, as another example, a case where the protective sheet 12 is formed into a card shape as shown in FIG. 4 will be described.

In FIG. 4, the structure is such that insertion fittings 18 and 19 are provided at both ends of the detection surface 110 of the toner concentration sensor 10 for inserting a card-shaped protective sheet 12d. In this case, in response to a single word from the counter 13, the microcomputer 14 lights up a lamp (for example, provided on the operating section of the image forming apparatus) to inform the operator that it is time to replace the protective sheet 12d. Then, the operator notices that the lamp is on and replaces the card-shaped protective sheet (12d). As a result, the detection surface 11 of the toner concentration sensor 10
is covered with a new protective sheet) 12d.

[Effects of the Invention] In the present invention, even if the protective sheet provided on the toner concentration detection surface is scratched or has toner attached to it, it is replaced with a new protective sheet at a predetermined time, so that accurate toner concentration can be obtained. This can be detected and an appropriate toner density can be maintained.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of a developing device using a toner concentration sensor according to an embodiment of the present invention, and FIG. FIG. 3 is a plan view of a disk-shaped protective sheet as another embodiment of the present invention, and FIG. 4 is a schematic cross-sectional view of a card as another embodiment of the present invention. FIG. 3 is a simplified perspective view of a case where a protective sheet of the same type is used. 12.12a, 12b, 12c, 12d...Protective sheet, 13...Counter (determination means) 14...Microcomputer (control means) 15...
・Motor (transportation means) X...Developer

Claims (2)

[Claims] (1) A toner concentration sensor that detects the toner concentration of a developer, comprising: a determining means for determining when to replace a protective sheet provided on a toner concentration sensing surface; a moving means for moving the protective sheet; A toner concentration sensor comprising: a control means for controlling the moving means based on a determination result. (2) The toner density sensor according to claim 1, wherein the determining means is a counter that counts the number of copies and issues a signal when a certain number of copies is reached.