JP5880261B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus in which an electrostatic latent image is formed on a photoreceptor by electrophotography and the electrostatic latent image is developed with toner.

  In general, in an electrophotographic image forming apparatus, a toner replenishing container containing toner is attached to the apparatus main body, and the toner is replenished to the developer tank directly from the toner replenishing container or via a hopper. It was. In the developer tank, the toner concentration in the developer is detected by a magnetic sensor, and the toner consumed in association with the developing operation is appropriately replenished to maintain a predetermined toner concentration.

  Conventionally, a toner detection sensor is also installed in the toner supply container or the hopper, and when the sensor no longer detects the presence of toner, the toner supply container is determined to be empty, and the user is prompted to replace the toner supply container. It was. In order to reduce the cost, a method for omitting the toner detection sensor in the toner supply container or the hopper is studied. In Patent Document 1, the toner hopper (toner supply) is used in a state where toner is not consumed by interrupting or prohibiting the image forming operation. The toner remaining in the toner hopper is reduced when the toner supply is forcibly supplied from the container) to the developer container and the change in the detected value of the toner sensor installed in the developer container is small. Judgment is made to notify the user of “near end”.

  However, in the technology described in Patent Document 1, the time from “near end (near empty)” to “empty” where the toner remaining amount actually becomes 0 is short, and the user can set a new toner hopper by informing “near end”. There was not much time to prepare. That is, the number of images that can be formed is limited from the notification of “near end”, and a situation in which the apparatus cannot be used until a new toner hopper is prepared. Such a problem appears remarkably when the capacity of the developer container is small.

JP 2005-309322 A

  An object of the present invention is to provide an image forming apparatus capable of determining a state in which the remaining amount of toner has decreased relatively early without installing a toner detection sensor in the toner bottle.

An image forming apparatus according to an aspect of the present invention is
The toner is transported from the toner bottle to the developer tank of the developing device via the toner supply path, and the toner density in the developer is detected by a toner density sensor installed in the developer tank, and the toner density reaches a predetermined value. In an image forming apparatus that replenishes toner from the toner replenishment path when less than
A toner replenishment path from the toner bottle to the developer tank, and a first path and a second path having different toner replenishment amounts to the developer tank;
When the toner density including the toner replenished from the first path and the second path is continuously detected by the toner density sensor , the change amount of the toner density recovery rate in the developer tank per time A control means for determining that the remaining amount of toner has decreased at a first change point at which a certain toner density gradient indicates a decrease in the recovery rate and has changed in a direction in which the toner density gradient increases .
It is provided with.

  In the image forming apparatus, when the toner density detected by the toner density sensor installed in the developer tank falls below a predetermined value, the toner corresponding to the consumption is supplied. At this time, the toner is supplied to the developer tank through the first path and the second path. Normally, a fixed amount of toner is supplied from the first path and the second path. When the toner replenishment progresses and the toner in the toner bottle runs out, first, the toner in the route with a large replenishment amount disappears, and the toner is replenished only from the route with a small replenishment amount. When the toner density sensor continues to detect the toner density installed in the developer tank, the toner density gradient is changed when the toner is replenished only from the path where the amount of replenishment is small (the remaining amount of toner is low). Appears as a reduced first change point. The control unit determines that the remaining amount of toner has decreased at the first change point, and prompts the user to replace the toner bottle as necessary. At the time when the first change point occurs, a small amount of toner remains in the path with a small supply amount, and thus image formation is continued until the remaining amount of toner runs out using this residual toner.

  According to the present invention, it is possible to determine a state in which the remaining amount of toner has decreased relatively early without installing a toner detection sensor in the toner bottle, and as a result, there is a margin for continuing image formation until the replacement of the toner bottle. Can be obtained.

1 is a schematic block diagram illustrating a control system of an image forming apparatus according to an embodiment. 4A and 4B are explanatory diagrams illustrating a first example of a toner replenishing mechanism, where FIG. 5A illustrates a normal state, FIG. 5B illustrates a state where the amount of remaining toner is low, and FIG. Show. 6 is a graph showing characteristics of a toner density sensor. 6 is a graph showing a toner density recovery rate (toner density gradient) in a developer tank. FIG. 6 is a flowchart illustrating a procedure of toner density control. FIG. 10 is an explanatory diagram illustrating a second example of a toner supply mechanism.

  Embodiments of an image forming apparatus according to the present invention will be described below with reference to the accompanying drawings. In addition, the same code | symbol is attached | subjected to the same member and part in each figure, and the overlapping description is abbreviate | omitted.

  As shown in FIG. 1, the image forming apparatus includes a control system including an image control unit 10 that processes image data and an engine control unit 11 that generally processes image formation. The engine control unit 11 controls the high-voltage power supply unit 12 based on image information sent from the image control unit 10, and an image is formed by the process unit 13 including a photoconductor. The engine control unit 11 controls the drive unit 14 to replenish toner. Note that a specific configuration and an image forming process of an electrophotographic image forming apparatus are conventionally known, and a description thereof will be omitted.

  FIG. 2 shows a toner supply mechanism 20A as a first example. The toner supply mechanism 20A includes a toner bottle 21 that can be attached to and detached from the image forming apparatus main body, and toner (which may include a small amount of carrier) from the toner bottle 21 via the first path P1 and the second path P2. Then, toner is supplied to the developer tank 30. The developer tank 30 constitutes a developing device main body, and a developer composed of a carrier and toner is supplied to the outer peripheral surface of a developing roller (not shown) while circulating through the developer tank 30, and from the developing roller to the outer peripheral surface of the photoreceptor. Supplied. The configuration of this type of developing device main body is well known, and detailed description thereof is omitted.

  The developer tank 30 is provided with a toner concentration sensor SE for detecting the toner concentration including the replenished toner (the mixing ratio of the toner with respect to the total amount of carrier and toner). In the toner concentration sensor SE, for example, the cycle of pulses to be output changes according to the magnetic permeability of the carrier and toner mixture, and the number of pulses output is input to the engine control unit 11 and is based on the number of pulses. The toner density is detected.

  FIG. 3 shows the relationship between the number of output pulses of the sensor SE and the toner density. When the toner density is low, the number of pulses output from the sensor SE is small, and the number of pulses increases as the toner density increases. When the number of pulses from the sensor SE is maintained at a predetermined value, that is, when the toner concentration of the developer in the developer tank 30 is lower than the predetermined value, the first and second paths P1, P2 described in detail below. Then, the toner is supplied to the developer tank 30. In addition, a predetermined amount of toner is supplied from the toner bottle 21 so that the toner does not run out in the first and second paths P1 and P2.

  The toner bottle 21 has a cylindrical shape, and has two toner supply ports 22a and 22b at the bottom of one end thereof. A toner hopper portion 25 is disposed between the toner bottle 21 and the developer tank 30. The toner hopper 25 is divided into two chambers 27a and 27b by a partition wall 26, and toner supply ports 28a and 28b facing the developer tank 30 are provided at the bottom of each chamber 27a and 27b. Replenishing rollers 29a and 29b are respectively installed in the toner replenishing ports 28a and 28b so as to be rotatable in the direction of the arrow.

  The first path P1 includes a toner supply port 22a, a chamber 27a, and a toner supply port 28a. The second path P2 includes a toner supply port 22b, a chamber 27b, and a toner supply port 28b. An equal amount of toner per unit time is supplied to the chambers 27a and 27b from the toner supply ports 22a and 22b. When the replenishing rollers 29a and 29b have different diameters and are driven at the same rotational speed, the amount of toner replenished from the toner replenishing port 28b to the developer tank 30 by the rotation of the roller 29b depends on the rotation of the roller 29a. The amount of toner supplied from 28a to the developer tank 30 is larger.

  In the toner replenishing mechanism 20A configured as described above, when toner remains in the toner bottle 21, as shown in FIG. 2A, the same amount of toner is stored in the chamber from the toner supply ports 22a and 22b. 27a and 27b. On the other hand, more toner is supplied to the developer tank 30 from the toner supply ports 28a and 28b than the supply amount from the supply port 28a per unit time. The toner density recovery rate at this time is substantially constant as shown by a line segment B1 in FIG.

  When the toner in the toner bottle 21 runs out, as shown in FIG. 2B, the toner supply from the toner bottle 21 to the chambers 27a and 27b disappears, and the chamber 27b with a large replenishment amount is earlier than the chamber 27a with a small replenishment amount. Toner runs out. As a result, the amount of toner replenished to the developer tank 30 decreases, and the toner density recovery rate in the developer tank 30 slightly decreases. That is, the toner density gradient is lowered (see the line segment B2), and it is determined that the remaining amount of toner in the toner hopper portion 25 is reduced by detecting the change point C1 at this time.

  Thus, even if the remaining amount of toner decreases, the toner is replenished from the first path P1 (chamber 27a). Therefore, while the toner remains in the chamber 27a, the toner concentration is lowered but constant. (See line segment B3). As shown in FIG. 2C, when the toner in the chamber 27a runs out, the toner supply is completely stopped, and the toner concentration in the developer tank 30 rapidly decreases (see line segment B4). By detecting the change point C2 at this time, it is determined that the toner has disappeared in the toner hopper 25.

  According to the toner replenishing mechanism 20A, when the first change point C1 is detected, a near-empty warning is issued and the user is prompted to replace the toner bottle 21, thereby replenishing the toner still remaining in the chamber 27a. However, the image formation is continued.

  A control procedure by the engine control unit 11 will be described with reference to a flowchart of FIG. While the printing operation is continuing (step S1), if the toner concentration sensor SE detects a decrease in toner concentration (YES in step S2), the toner replenishing operation from the first and second paths P1 and P2 is performed. (Step S3). If the recovery rate of the toner density at that time is a normal value (YES in step S4), it is determined that there is toner for replenishment (step S5), and the printing operation is continued. If the recovery rate of the toner density is not a normal value (NO in step S4) and the first change point C1 is detected (YES in step S6), it is determined that the remaining amount of toner is low (step S7), and a near empty warning is issued. (Step S8) and the printing operation is continued.

  When the recovery rate of the toner density is not a normal value and the second change point C2 is detected (YES in step S9), it is determined that there is no toner (step S10), and a warning indicating no toner is given and the printing operation is prohibited. (Step S11). Note that the warning of near empty or no toner is given, for example, by displaying that fact on an operation panel (not shown).

  FIG. 6 shows a toner supply mechanism 20B as a second example. The toner replenishing mechanism 20B is configured such that the supply amount of the toner bottle 21 from the supply port 22a is larger than the supply amount from the supply port 22b, and the replenishment amounts of the supply ports 28a and 28b to the developer tank 30 are equal to each other. It is. Accordingly, the toner supply rollers 29a and 29b are driven at the same diameter and the same rotation speed.

  In the toner replenishing mechanism 20B, the amount of toner supplied from the toner bottle 21 to the toner hopper 25 is larger in the chamber 27a than in the chamber 27b. Therefore, after the toner in the toner bottle 21 runs out, Similar to the toner supply mechanism 20A as an example, the toner in the chamber 27b runs out quickly. Accordingly, the toner supply mode and control procedure through the first and second paths P1 and P2 are the same as those of the toner supply mechanism 20A.

  The image forming apparatus according to the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the gist thereof.

  In particular, the configuration of the toner bottle and the toner hopper, the form of the toner path from the toner bottle to the developer tank, and the like are arbitrary. Further, various forms can be adopted for the developing device.

  As described above, the present invention is useful for an image forming apparatus, and is particularly excellent in that a state in which the amount of remaining toner is low can be determined relatively early without installing a toner detection sensor in the toner bottle. Yes.

DESCRIPTION OF SYMBOLS 11 ... Engine control part 13 ... Process part 14 ... Drive part 20A, 20B ... Toner supply mechanism 21 ... Toner bottle 22a, 22b ... Toner supply port 25 ... Toner hopper part 28a, 28b ... Toner supply port 30 ... Developer tank SE ... Toner density sensor P1... First path P2.

Claims (4)

The toner is transported from the toner bottle to the developer tank of the developing device via the toner supply path, and the toner density in the developer is detected by a toner density sensor installed in the developer tank, and the toner density reaches a predetermined value. In an image forming apparatus that replenishes toner from the toner replenishment path when less than
A toner replenishment path from the toner bottle to the developer tank, and a first path and a second path having different toner replenishment amounts to the developer tank;
When the toner density including the toner replenished from the first path and the second path is continuously detected by the toner density sensor , the change amount of the toner density recovery rate in the developer tank per time A control means for determining that the remaining amount of toner has decreased at a first change point at which a certain toner density gradient indicates a decrease in the recovery rate and has changed in a direction in which the toner density gradient increases .
An image forming apparatus comprising: When the toner density sensor including the toner replenished from the first path and the second path continues to be detected by the toner density sensor, the control means, after the first change point, the toner density 2. The image forming apparatus according to claim 1, wherein the image forming apparatus determines that the toner has run out at a second change point at which the gradient is decreased and the toner density gradient is further increased . 3. A toner hopper is disposed in the toner supply path,
Each of the first path and the second path leads from the toner bottle to the developer tank through the toner hopper.
The same amount of toner is supplied from the toner bottle to the first path and the second path, and the toner replenishment amounts by the first path and the second path are mutually supplied from the toner hopper to the developer tank. Different,
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. A toner hopper is disposed in the toner supply path,
Each of the first path and the second path leads from the toner bottle to the developer tank through the toner hopper.
Different amounts of toner are supplied from the toner bottle to the first path and the second path, and the same amount of toner is supplied from the toner hopper to the developer tank by the first path and the second path. Being replenished,
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.

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