JPH04281483A - Image forming device - Google Patents

Abstract

PURPOSE:To offer an image forming device which can execute a proper action at the time of generating such a state that toner does not exist on a carrying means between a toner container and a developing mechanism even when the toner exists in the toner container. CONSTITUTION:In the image forming device that the toner is sent to the developing mechanism 4 from the toner container 32 through the toner carrying means 40, a toner residual quantity detector 101 for detecting that the toner in the container 32 becomes prescribed quantity or under, a toner concentration detector 102 for detecting the concentration of the toner in the mechanism 4 and a means which interrupts an image forming action and sends the toner to the mechanism 4 from the container 32 through the carrying means 40 when the toner in the container 32 is more than the prescribed quantity and the concentration detected by the detector 102 is lower than control reference concentration (alpha) are provided.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to image forming apparatuses such as copying machines and printers.

0002

2. Description of the Related Art In recent years, as the demand for color images has increased, many electrostatic type color image forming apparatuses have been proposed.
It has been put into practical use. In a typical example of such a color image forming apparatus, an electrostatic charger provided on a rotating drum is used for each of the four colors yellow, magenta, cyan, and black. An electrostatic latent image is developed on the photographic photoreceptor by a developing device and transferred to copy paper, thereby producing a color image on the copy paper.

The developing device in the above color image forming apparatus must be a multicolor developing device capable of selectively developing an electrostatic latent image using, for example, the four colors described above.

As a conventional multicolor developing device, for example, one disclosed in Japanese Patent Laid-Open No. 2-148055 is known. This multicolor developing device includes a plurality of developing mechanisms mounted on a movable frame body that is reciprocated in the vertical direction by a moving means. When the movable frame is moved in the vertical direction by the moving means, each of the developing mechanisms is selectively positioned at the developing position of the rotating drum, and the developing mechanisms are selectively positioned at the developing position of the rotating drum, and the developing mechanisms are selectively positioned at the developing positions of the rotating drum, and the developing mechanisms are selectively positioned at the developing positions of the rotary drum, and the developing mechanisms are selectively positioned at the developing positions of the rotating drum. It will be done. Each of the developing mechanisms includes a developing housing and a toner storage container for storing toners of mutually different colors. The toner in the toner storage container is replenished into the developing housing by the toner conveying means during the developing operation of the developing mechanism.

The conventional multicolor developing device has the following problems.

(1) Since a toner storage container is provided in each developing mechanism mounted on the movable frame, a space is required for the toner storage container to move upward;
Therefore, the capacity of the toner storage container is restricted, the number of times the toner storage container must be replenished with toner increases, and the color image forming apparatus becomes larger.

(2) Since the weight of the entire movable frame including each developing mechanism increases, the inertial force due to movement increases, and the load applied to the moving means increases. Therefore, it becomes extremely difficult to cope with higher speeds, and it takes time to switch between each developing mechanism. Furthermore, a large capacity motor is required for the movable frame.

(3) Since the capacity of the toner remaining in the toner storage container changes, the load on the moving means when driving and stopping the movable frame changes, and the positioning and operation/stop timing of each developing mechanism changes. It is difficult to ensure sufficient accuracy.

On the other hand, a multicolor developing device is known in which a toner storage container is located above the developing mechanism and toner is supplied into the developing mechanism via a flexible tube containing a spiral. However, in this apparatus, a space is required for arranging the toner storage container further upward from the position where the developing mechanism has moved to the uppermost position, which increases the size of the entire color image forming apparatus. Moreover, a considerable amount of wasted space is created below the toner storage container.

0010

[Problem to be solved by the invention] Therefore, the applicant
The multi-color developing device shown in Figs. 1 and 2 is capable of ensuring sufficient capacity of the toner storage container, increasing the switching speed of each developing mechanism, and ensuring sufficient precision in positioning of each developing mechanism. We have developed an image forming device with

Details of the multicolor developing device shown in FIGS. 1 and 2 will be explained in Examples. Figures 1 and 2
The multicolor developing device shown in FIG. The toner conveying means 40 includes a cylindrical member 44 that extends vertically upward from the lower end of the container body 33 of the toner storage container 32, and a cylindrical member 44 that is disposed within the cylindrical member 44 and extends along it. A spiral roller 46 is configured to send the toner that has flowed into the cylindrical member 44 to the upper end thereof, and a spiral roller 46 is configured to connect the upper end of the cylindrical member 44 and the developing mechanism 6 and to send the toner that has flowed into the upper end of the cylindrical member 44. and a toner falling passage means 48 for replenishing the developing mechanism 6.

[0012] In such a multicolor developing device, depending on the method of toner replenishment, a state may occur in which toner is not present in the intermediate portion of the cylindrical member 44 even if toner is supplied to the toner storage container 32. .

An object of the present invention is to provide an image forming apparatus that can take appropriate measures when such a situation occurs.

[0014]

[Means for Solving the Problems] A first image forming apparatus according to the present invention is an image forming apparatus in which toner is sent from a toner storage container to a developing mechanism via a toner conveying means, and in which the toner in the toner storage container is A toner remaining amount detector detects when the toner concentration is below a predetermined amount, a toner concentration detector detects the toner concentration in the developing mechanism, and a toner concentration detector that detects when the toner concentration in the toner storage container exceeds a predetermined amount and the toner concentration and means for interrupting the image forming operation and sending the toner from the toner storage container to the developing mechanism via the toner conveying means when the detected density of the detector is lower than the control reference density. .

[0015] When the toner is sent from the toner storage container to the developing mechanism via the toner conveying means, it is preferable to drive the toner stirring means of the developing mechanism. Also,
It is preferable to notify that toner is being replenished while the toner is being sent from the toner storage container to the developing mechanism via the toner transport means.

Furthermore, if the amount of toner in the toner storage container falls below a predetermined amount before a predetermined period of time elapses after the toner starts being sent from the toner storage container to the developing mechanism via the toner transport means, the image forming operation is stopped. It is preferable to notify the user that the toner should be replenished.

A second image forming apparatus according to the present invention is an image forming apparatus in which toner is sent from a toner storage container to a developing mechanism via a toner conveying means, and when the amount of toner in the toner storage container becomes less than a predetermined amount. and a toner concentration detector to detect the toner concentration in the developing mechanism. means for interrupting the image forming operation when the density is lower than the control reference density and transporting the toner from the toner storage container to the developing mechanism via the toner transport means; and means for transporting the toner from the toner storage container through the toner transport means to the developing mechanism. The invention is characterized by comprising means for stopping the image forming operation when the detected density of the toner density detector is lower than the control reference density even after a predetermined period of time has elapsed since the toner was sent to the toner.

The image forming operation is stopped when the detected density of the toner density detector is lower than the control reference density even after a predetermined period of time has elapsed since the toner was started to be sent from the toner storage container to the developing mechanism via the toner transport means. It is also preferable to notify that an abnormality has occurred.

[0019]

[Operation] In the first image forming apparatus according to the present invention, when the amount of toner in the toner storage container is more than a predetermined amount and the detected density of the toner density detector is lower than the control reference density,
The image forming operation is interrupted, and toner is sent from the toner storage container to the developing mechanism via the toner transport means.

[0020] In the second image forming apparatus according to the present invention,
When the amount of toner in the toner storage container is more than a predetermined amount and the density detected by the toner density detector is lower than the control reference density, the image forming operation is interrupted and the toner is transferred from the toner storage container to the toner transport means for development. sent to the organization.

[0021] If the detected density of the toner density detector is lower than the control reference density even after a predetermined period of time has elapsed since the toner began to be sent from the toner storage container to the developing mechanism via the toner transport means, the image forming operation is started. will be stopped.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a copying machine having a multicolor developing device will be described below with reference to the accompanying drawings.

In FIGS. 1 and 2, a multicolor developing device 2
The apparatus includes a stationary frame and a movable frame attached to the stationary frame so that it can be moved back and forth in the vertical direction by a moving means (none of which are shown).

The stationary frame body is entirely composed of a rectangular parallelepiped housing, and the multicolor developing device 2 is disposed inside the housing. The movable frame body is entirely composed of a substantially rectangular parallelepiped housing. The movable frame is oriented so that it can reciprocate in the vertical direction along a guide rail (not shown) provided on the stationary frame.

In this example, four developing mechanisms 4, 6, 8, and 10 are mounted on the movable frame in order from the top at predetermined intervals in the vertical direction. The developing mechanism 4 stores cyan, the developing mechanism 6 stores yellow, the developing mechanism 8 stores magenta, and the developing mechanism 10 stores black developers. This developer consists of, for example, toner and carrier. The basic configuration of each developing mechanism is substantially the same except for some parts described below, so here,
The developing mechanism 6 will be described as a representative of them.

The developing mechanism 6 includes a developing housing 12. The developer housing 12 is divided into two chambers 1 by a partition wall 14 provided along the front-rear direction (longitudinal direction).
6 and 18 are formed. Chambers 16 and 18 are
Both ends of the partition wall 14 are communicated with each other by a communication path (not shown). A spiral roller 22 for stirring and circulating the sleeve 20 and the developer is arranged in the chamber 16, and a spiral roller 24 for stirring and circulating the developer is arranged in the chamber 18.

The sleeve 20 is rotatably supported by the developer housing 12, and a portion of its circumferential surface protrudes from an opening provided along the left end of the developer housing 12. When the developing mechanism 6 is positioned at a predetermined developing position, the protruding peripheral surface of the sleeve 20 approaches the developing position of the rotating drum (see the two-dot chain line in FIG. 2) provided on the stationary frame. Toner is applied to the surface of a rotating drum to perform the developing action.

The spiral rollers 22 and 24 are rotatably supported so as to extend parallel to each other along the longitudinal direction of the chambers 16 and 18 of the developer housing 12. The sleeve 20 and the spiral rollers 22 and 24 are each connected to a drive motor 83 via a gear train (not shown).
(see FIG. 3), and is configured to be rotationally driven at the same time. As the spiral rollers 22 and 24 rotate, the developer in each chamber 16 and 18 is sent in opposite directions along the length. As a result, the developer within the developer housing 12 is circulated while being stirred.

A toner receiving opening 26 is formed above the chamber 18 of the developing housing 12 for receiving toner supplied from a toner conveying means to be described later. The toner receiving opening 26 is arranged at a position closer to the upstream side of the spiral roller 24.

By moving the movable frame body by the moving means, each of the developing mechanisms 4, 6, 8, and 10 is selectively positioned at a predetermined developing position and performs mutually different color developing operations. It is configured like this.

The stationary frame on the right end side of the movable frame includes:
The same number of toner storage containers 28, 30, 32, and 34 as the developing mechanisms 4, 6, 8, and 10 are fixedly arranged in parallel in the horizontal direction. These toner storage containers are mounted on a support frame (not shown) provided on the stationary frame. Furthermore, between each of the toner storage containers 28, 30, 32, and 34 and each of the developing mechanisms 4, 6, 8, and 10 corresponding to each of the toner storage containers, the toner in each toner storage container is Toner conveying means 36, 38, 40 and 42 are provided for replenishing the respective developing mechanisms with toner. Black toner is in the toner storage container 28, cyan toner is in the toner storage container 30,
Yellow toner is stored in the toner storage container 32, and magenta toner is stored in the toner storage container 34.

Each of these toner storage containers 28, 30, 3
2 and 34 and each toner transport means 36, 38, 4
0 and 42 are substantially the same except for the layout, so here, the toner storage container 32 and the toner conveying means 40 provided in connection therewith will be described as a representative example.

[0033] The toner conveying means 40 is connected to the toner storage container 3.
A cylindrical member 44 extends vertically upward from the lower end of the container body 33 of No. 2; a spiral roller 46 for feeding the toner to the upper end; and a toner fall passage means 48 for connecting the upper end of the cylindrical member 44 and the developing mechanism 6 and replenishing the developing mechanism 6 with the toner sent to the upper end of the cylindrical member 44; Contains.

A cylindrical support portion 50 is formed on the side (left side in FIG. 2) of the container body 33.
The lower end portion of the cylindrical member 44 is inserted and supported within the cylindrical member 44. The spiral roller 46 includes a shaft 52 rotatably supported by bearings provided at the upper and lower ends of the cylindrical member 44, and a spiral member 54 provided on the shaft 52. The shaft 52 protrudes downward from the lower end of the cylindrical member 44 and is connected to a motor 82 that is a drive source. This motor 82
is controlled to operate in response to a toner replenishment signal.

A toner inlet opening 56 is formed at the lower end of the cylindrical member 44 . An opening 58 is also formed in a portion of the support portion 50 of the container body 33 that corresponds to the toner inflow opening 56 . Inside the lower end (bottom) of the container body 33,
A rotating blade 60 is provided for forcibly sending the toner stored in the container body 33 into the lower end of the cylindrical member 44.

The rotating blade 60 is composed of a rotating shaft 62 extending through the container body 33 and a plurality of blades 64 provided on the rotating shaft 62. The rotating blade 60 is connected to a motor 81 that is a driving source. This motor 81 is controlled to operate in response to a signal such as a toner replenishment signal, a main switch ON signal of a copying machine, or a rotation signal of a sleeve of a developing mechanism.

As the rotary blade 60 rotates, the toner at the bottom of the container body 33 is forced into the lower end of the cylindrical member 44 through the opening 58 and the toner inflow opening 56. A toner outflow opening 65 is formed at the upper end of the cylindrical member 44 for allowing the toner sent by the spiral roller 46 to flow out into a connection housing 68, which will be described later.

The toner falling passage means 48 includes a bellows 66 that is an extensible means arranged to extend substantially along the moving direction (vertical direction) of the developing mechanism 6. The toner fall passage means 48 is also disposed between the upper end of the cylindrical member 44 and the upper end of the bellows 66 .
A connecting housing 68 connects the lower end of the bellows 66 to the developing mechanism 6 and allows the toner that has fallen into the bellows 66 to fall into the developing mechanism 6. It also includes a connecting pipe 70 for replenishment.

The connection housing 68 has a cylindrical portion 72 connected to the upper end of the cylindrical member 44 formed below one end, and another cylindrical portion 74 connected to the upper end of the bellows 66 at the other end. is formed. Connection housing 6
A ventilation opening is formed at the upper end of the housing 8 . A filter 76 is attached to this ventilation opening to prevent toner from being discharged from the ventilation opening.

[0040] In the above configuration, the movable frame body is
The moving means reciprocates in the vertical direction according to the copying operation. Each of the developing mechanisms 4, 6, 8, and 10 is selectively positioned at a predetermined developing position and controlled so as to perform mutually different developing actions.

When the movable frame is moved by the moving means and the developing mechanism 6 is positioned at a predetermined developing position, the sleeve 20 and spiral rollers 22 and 24 of the developing mechanism 6 are rotated by the drive source and rotated relative to the rotating drum. A developing action is performed. On the other hand, due to the toner replenishment signal from the developing mechanism 6,
The motors 82 and 81 are driven, and the spiral roller 4
6 and rotating blade 60 rotate.

[0042] As a result, the toner in the container body 33 is
The rotating blade 60 feeds into the lower end of the cylindrical member 44 and the spiral roller 46 feeds into the connection housing 68 . The toner sent to the connection housing 68 falls through the bellows 66 and the connection pipe 70, and then
It is fed into a chamber 18 within developer housing 12 . When the predetermined developing action of the developing mechanism 6 is completed, the movable frame starts moving, and one of the other developing mechanisms 4, 8, or 10 is selected and positioned at a predetermined developing position. Then, the same operation as described above is performed.

The toner replenishment control of this developing device will be explained below. Here, the toner storage container 32, the toner conveying means 40 provided in connection therewith, and the developing mechanism 6 provided in connection therewith will be described.

The container body 33 of the toner storage container 32 includes:
A remaining toner amount detector 101 is provided to detect when the amount of toner in the toner storage container 32 has become less than a predetermined value. Furthermore, a toner concentration detector 102 for detecting toner concentration is provided within the developer housing 12.

FIG. 3 shows the output characteristics of the toner concentration detector 102. The output of the toner concentration detector 102 becomes smaller as the toner concentration increases. In Figure 3, VO
is the output voltage of the toner concentration detector 102 with respect to the concentration α at the center of the preferred toner concentration range (hereinafter referred to as control reference concentration). Further, VM is the output voltage of the toner concentration detector 102 with respect to the copy prohibition determination density β.

FIG. 4 shows a toner replenishment control circuit. The CPU 110 performs toner replenishment control processing. The CPU 110 stores the program, etc.
OM111 and RAM112 that stores necessary data
It is equipped with

The CPU 110 includes a remaining toner amount detector 10.
1 and a detection signal from the toner concentration detector 102 are sent. From the CPU 110, a drive control circuit 121 for the motor 81 that drives the rotary blade 60, a drive control circuit 122 for the motor 82 that drives the spiral roller 46, a drive control circuit 123 for the motor 83 that drives the spiral rollers 22 and 24, and a display device. A control signal is sent to 124.

FIGS. 5 and 6 show the toner replenishment control processing procedure performed by the CPU 110.

After the copying machine is powered on, the number of copies is set (step S1), and when the print key is turned on (
In step S2), it is determined whether an abnormality flag, which will be described later, is set (step S3). If set, the process returns to step S2. In other words, copying is prohibited.

If the abnormality flag is not set, it is determined whether the toner density A detected by the toner density detector 102 is lower than the copy prohibition determination density β (step S4). If the detected toner density A is lower than the copy prohibition determination density β (A<β), step S2
Return to In other words, copying is prohibited.

If the detected toner density A is equal to or higher than the copy prohibition determination density β, a copying operation for one sheet is performed (step S5). Then, based on the detection signal of the remaining toner amount detector 101, it is determined whether the amount of toner in the toner storage container 32 is less than or equal to a predetermined value (step S6).
. If the amount of toner in the toner storage container 32 is below the predetermined value, a message indicating that toner should be replenished is displayed on the display device 124 (step S7), and the process returns to step S2. In this case, continuous copying is prohibited even if the set number of copies is multiple. However, it is possible to copy one sheet at a time by operating the print key.

In step S6, the toner storage container 3
If the amount of toner in 2 is greater than a predetermined value, the display device 124
It is determined whether or not a display indicating that toner should be replenished is displayed (step S8). If this display is displayed, after this display is erased (step S9), the toner concentration detector 102 Whether the toner concentration A detected by
≦α) or higher than the control reference concentration α (A>α) (step S10).

In step S8, if the display indicating that toner should be replenished is not displayed, the process moves to step S10, and it is determined whether the toner concentration A detected by the toner concentration detector 102 is lower than the copy prohibition determination concentration β. (A<β
), the concentration for copy prohibition determination is equal to or higher than the control reference concentration α
Is it less than (β≦A≦α), or is it more than control reference concentration α (A>α)?
) is determined.

In step S10, if the toner density A detected by the toner density detector 102 is lower than the copy prohibition determination density β (A<β), a toner replenishment operation is started (step S11). In such a situation, after the amount of toner in the toner storage container 32 falls below a predetermined value, copies continue to be made without replenishing the toner into the toner storage container 32, and no toner is present in the hollow member 44. This occurs when the toner is replenished into the toner storage container 32 after the toner storage container 32 has reached the point where the toner storage container 32 is filled with toner.

The toner replenishment operation is carried out by motors 81, 82, 8.
3, the rotating blade 60 and the spiral roller 4
6 and spiral rollers 22 and 24.

During this toner replenishment operation, the display device 12
4, a message indicating that toner is being replenished is displayed (step S12), and the copying operation is interrupted (step S13). Further, it is determined whether a predetermined time, for example, 2 minutes has elapsed after the start of toner replenishment (step S14).
, if the predetermined time has not passed, the remaining toner amount detector 10
Based on the detection signal No. 1, it is determined whether the amount of toner in the toner storage container 32 is less than or equal to a predetermined value (step S15). If the amount of toner in the toner storage container 32 is not less than a predetermined value, it is determined whether the toner concentration A detected by the toner concentration detector 102 has become equal to or higher than the control reference concentration α (step S16). If the detected toner density A is lower than the control reference density α (A<α), the process returns to step S14 and the processes of steps S14 to S16 are repeated.

When the processes in steps S14 to S16 are being performed, when the detected toner concentration A becomes equal to or higher than the control reference concentration α in step S16, (A
≧α), the display indicating that toner is being replenished is erased (step S17), and the copying operation is restarted (step S1
8). In this case, if copying for the set number of sheets has not been completed (step S19), the process returns to step S5 and a copying operation for one sheet is performed. If the set number of copies have been completed (step S19), the process returns to step S1.

[0058] While steps S14 to S16 are being performed, if the amount of toner in the toner storage container 32 falls below a predetermined value in step S15, the display indicating that toner is being replenished is erased. (Step S20), and a message to the effect that toner should be replenished is displayed on the display device 124 (Step S21). Further, the copying machine is stopped (step S22), and this process ends. In this case, the user replenishes the toner storage container 32 with toner, and the copying machine becomes ready for copying.

When steps S14 to S16 are being performed, if a predetermined period of time has elapsed after the start of toner replenishment in step S14, the display indicating that toner is being replenished is erased (step S23). , a message indicating that an abnormality has occurred is displayed on the display device 124 (step S
24), an abnormality flag is set (step S25)
. Furthermore, the copying machine is stopped (step S26), and this process ends. In this case, failure recovery processing is performed by a service person. After the failure is recovered, the abnormality flag is reset.

In step S10, if the toner concentration A detected by the toner concentration detector 102 is equal to or higher than the copy prohibition determination concentration β and equal to or lower than the control reference concentration α (β≦A≦α), the toner A replenishment operation is started (step S27). This toner replenishment operation is performed by motor 8.
1, 82, and 83 to drive the rotary blade 60, spiral roller 46, and spiral rollers 22 and 2.
This is done by driving 4.

In this case, the copying operation is carried out as usual, and if copying for the set number of sheets has not been completed (step S28), the process returns to step S5 and the copying operation for one sheet is performed. If the set number of copies have been completed (step S28), the process returns to step S1.

In step S10, if the toner concentration A detected by the toner concentration detector 102 is greater than the control reference concentration α (A>α), it is determined whether or not a toner replenishment operation is being performed. (Step S2
9). If toner replenishment operation is being performed (step S
29), the toner replenishment operation is stopped (step S30).
). If copying for the set number of sheets has not been completed (step S28), the process returns to step S5 and a copying operation for one sheet is performed. If the set number of copies have been completed (step S28), the process returns to step S1.

[0063] In step S29, if the toner replenishment operation is not performed, the process advances to step S28, and it is determined whether or not copying for the set number of sheets has been completed. If the set number of copies have not been completed, step S5
The process returns to , and the copying operation for one sheet is performed. If the set number of copies have been completed, the process returns to step S1.

[0064]

According to the present invention, when a situation occurs in which there is no toner in the conveyance means between the toner storage container and the developing mechanism even if there is toner in the toner storage container, it is possible to Treatment can be performed.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a multicolor developing device.

FIG. 2 is a sectional view taken along line II-II in FIG. 1;

FIG. 3 is a graph showing output characteristics of a toner concentration detector.

FIG. 4 is an electrical block diagram showing a toner replenishment control circuit.

FIG. 5 is a flowchart showing a toner replenishment control processing procedure by a CPU.

FIG. 6 is a flowchart showing a toner replenishment control processing procedure by the CPU.

[Explanation of symbols]

4 Developing mechanism 6 Developing mechanism 8 Developing mechanism 10 Developing mechanism 22 Spiral roller 24 Spiral roller 28 Toner storage container 30 Toner storage container 32 Toner storage container 34 Toner storage container 36 Toner conveyance means 38 Toner transport means 40 Toner transport means 42 Toner transport means 46 Spiral roller 60 Rotating blade 81 Motor 82 Motor 83 Motor 124 Display device 102 Toner concentration detector 110 CPU110 111 ROM111 112 RAM112

Claims (6)

[Claims] 1. In an image forming apparatus in which toner is sent from a toner storage container to a developing mechanism via a toner conveyance means, a remaining amount of toner is detected for detecting that the amount of toner in the toner storage container has fallen below a predetermined amount. a toner concentration detector for detecting the toner concentration within the developing mechanism; and when the amount of toner in the toner storage container is greater than a predetermined amount and the detected concentration of the toner concentration detector is lower than a control reference concentration;
An image forming apparatus comprising means for interrupting an image forming operation and transporting toner from a toner storage container to a developing mechanism via a toner transport means. 2. The image forming apparatus according to claim 1, wherein a toner stirring means of the developing mechanism is driven when the toner is sent from the toner storage container to the developing mechanism via the toner conveying means. 3. The image forming apparatus according to claim 1, further comprising a notification means for notifying that toner is being replenished while the toner is being sent from the toner storage container to the developing mechanism via the toner transport means. Device. 4. If the amount of toner in the toner storage container falls below a predetermined amount before a predetermined period of time elapses after the toner starts being sent from the toner storage container to the developing mechanism via the toner transport means, the image forming operation is started. The image forming apparatus according to claim 1, further comprising means for notifying that the image forming apparatus should be stopped and toner should be replenished. 5. In an image forming apparatus in which toner is sent from a toner storage container to a developing mechanism via a toner transport means, remaining toner amount detection for detecting that the amount of toner in the toner storage container has fallen below a predetermined amount. a toner concentration detector for detecting the toner concentration within the developing mechanism; and when the amount of toner in the toner storage container is greater than a predetermined amount and the detected concentration of the toner concentration detector is lower than a control reference concentration;
A means for interrupting the image forming operation and transporting the toner from the toner storage container to the developing mechanism via the toner transport means; 1. An image forming apparatus comprising: means for stopping an image forming operation when a detected density of a toner density detector is lower than a control reference density. [Claim 6] An abnormality occurs when the detected density of the toner density detector is lower than the control reference density even after a predetermined period of time has elapsed since the toner began to be sent from the toner storage container to the developing mechanism via the toner transport means. 6. The image forming apparatus according to claim 5, further comprising a notification means for notifying the user.