# US 2021/0240102 A1 · Image forming apparatus determining toner replacement timing

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 2021/0240102 A1
- Document ID: US20210240102A1
- Status: Published application
- Kind: A1
- Application number: 17/165,370
- Filed: 2021-02-02
- Published: 2021-08-05
- Earliest claimed: 2020-02-03
- Assignees: KYOCERA Document Solutions Inc.
- Applicants: KYOCERA Document Solutions Inc.
- Inventors: Kazunori TANAKA; Kanako MORIMOTO; Tamotsu SHIMIZU; Kenichi TAMAKI
- Web page: https://patentgrep.com/patent/US20210240102A1

## CPC

- G03G 15/0851: {the concentration being measured by electrical means}
- G03G 15/0848: {Arrangements for testing or measuring developer properties or quality, e.g. charge, size, flowability}
- G03G 15/169: {with means for preconditioning the toner image before the transfer (G03G15/095 and G03G15/11 take precedence)}
- G03G 15/5037: {the characteristics being an electrical parameter, e.g. voltage}
- G03G 15/5041: {Detecting a toner image, e.g. density, toner coverage, using a test patch (G03G15/553 takes precedence)}
- G03G 15/55: {Self-diagnostics; Malfunction or lifetime display}
- G03G: ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY

## Abstract

An image forming apparatus includes a toner charge amount predictor, a toner developing resistance calculator, and a determiner. The toner developing resistance calculator calculates a toner developing resistance on the basis of a bias voltage applied to a developing device and a measured developing current by dividing a value of the bias voltage by a value of the developing current when a developing device develops an electrostatic latent image formed on the surface of an image carrier to form a toner image. The toner charge amount predictor predicts a toner charge amount of a toner which is supplied to the image carrier by the developing device on the basis of a density of the toner image and the developing current. The determiner determines a state of the developing device on the basis of the toner charge amount and the toner developing resistance.

## Claims

### Claim 1

An image forming apparatus comprising:
an image carrier on a surface of which an electrostatic latent image is formed;
a developing device that supplies a toner to the image carrier and develops the electrostatic latent image formed on the image carrier to form a toner image;
a density detecting device that detects a density of the toner image developed by the developing device;
a current measuring device that measures a developing current flowing in the developing device; and
a control device including a processor, and configured to act, when the processor executes a control program, as:
a toner charge amount predictor configured to predict a toner charge amount which is an amount of electric charge of the toner supplied to the image carrier by the developing device;
a toner developing resistance calculator configured to calculate a toner developing resistance on the basis of a bias voltage applied to the developing device and the developing current measured by the current measuring device when the electrostatic latent image is developed by the developing device; and
a determiner configured to determine a state of the developing device on the basis of the toner charge amount predicted by the toner charge amount predictor and the toner developing resistance calculated by the toner developing resistance calculator,
wherein the toner charge amount predictor predicts the toner charge amount on the basis of the density detected by the density detecting device and the developing current, and
wherein the toner developing resistance calculator calculates the toner developing resistance by dividing a value of the bias voltage by a value of the developing current.

### Claim 2 (depends on 1)

The image forming apparatus according to claim 1, wherein the toner developing resistance calculator calculates a plurality of toner developing resistances on the basis of each of the developing currents corresponding to a plurality of bias voltages and calculates one toner developing resistance which is used for the determiner to determine a state of the developing device, on the basis of each of the calculated toner developing resistances.

### Claim 3 (depends on 2)

The image forming apparatus according to claim 2, wherein the toner developing resistance calculator calculates a linear function indicating a correspondence between the calculated toner developing resistances and determines a slope of the calculated linear function as the toner developing resistance which is used for the determiner to determine the state of the developing device.

### Claim 4 (depends on 1)

The image forming apparatus according to claim 1, wherein the determiner calculates an abnormality level indicating a degree of abnormality of the developing device on the basis of a function indicating a correspondence between the toner charge amount and the toner developing resistance, and
wherein the determiner determines a state of the developing device on the basis of the calculated abnormality level.

### Claim 5 (depends on 1)

The image forming apparatus according to claim 1, further comprising a storage device that stores an abnormality table indicating a correspondence between a combination of the toner charge amount and the toner developing resistance and the abnormality level,
wherein the determiner determines a state of the developing device on the basis of the abnormality table.

### Claim 6 (depends on 1)

The image forming apparatus according to claim 1, further comprising an intermediate transfer device that includes an intermediate transfer belt and a primary transfer roller primarily transferring a toner image formed on the image carrier to the intermediate transfer belt and applies a voltage to the primary transfer roller,
wherein the density detecting device detects the density of the toner image primarily transferred to the intermediate transfer belt of the intermediate transfer device.

### Claim 7 (depends on 6)

The image forming apparatus according to claim 6, wherein the determiner acquires a value of a voltage applied to the primary transfer roller by the intermediate transfer device and a value of a current flowing in the intermediate transfer device for application of the voltage and calculates the abnormality level on the basis of a transfer resistance value based on the acquired value of the voltage and the acquired value of the current, the toner charge amount, and the toner developing resistance.