JP2003050504A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device equipped with a developing device where next image formation is not affected adversely by the high consumption of developer by detecting the consumed developer immediately even when much developer is consumed by the image formation. SOLUTION: By providing a sensor (18) for detecting the quantity of the developer or the concentration of the developer near the 2nd aperture (13) of a partitioning member (11) by which the flow of the developer is turned back toward a 2nd carrying means (10) located at a position separate from a developing roller (2) or a supply roller (3) while putting the member (11) in between from a 1st carrying means (9) carried along from one end to the other end of the roller (2) or the roller (3), quantity of the consumed developer is detected in a short time and the next image forming operation is stopped based on the detection signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus having a developing device for supplying a developer to a member such as a developing roller while circulating the developer.

[0002]

2. Description of the Related Art An image forming apparatus having a developing device using a one-component developer or a two-component developer made of powder for forming a permanent image on a sheet material is known. The developing device forms an image while replenishing the developer consumed by the image formation. Then, by circulating the developer in the circulation path provided in the developing device, the developer is charged and the new developer and the developer stored in advance are sufficiently mixed to be a member of the developing roller or the supplying roller. We are supplying. The developer adhering to the developing roller is electrostatically adsorbed to the electrostatic latent image formed on the image carrier, and then undergoes the steps of transfer and fixing to form a permanent image on the sheet material. When the developer is supplied to the supply roller or the developing roller only by stirring without circulating the developer, the developer convects in the direction orthogonal to the developing roller, so that the stirring of the old and new developers becomes insufficient in the width direction. Will end up. Especially in an image forming apparatus equipped with a developing device using a large-sized sheet material, it is necessary to sufficiently mix the developer that has not contributed to the development with the stored developer, but the developer is charged in the width direction. There is a problem that the distribution and the concentration of the developer do not become constant.

As a method of circulating the developer, a pair of first and second screws as a conveying means and first and second openings provided at both ends are provided between the first and second screws. A circulation path is formed by the partition plate having the partition plate to circulate the developer, and the developer is directed toward the developing roller or the supplying roller which is provided close to the axial direction of the screw on one side (first) screw. Is being supplied.

It is desirable that the amount of circulating developer is regulated to a constant amount (roughness or concentration). For this reason, in the case of a developing device using a one-component developer, the area in contact with the developing roller or the supply roller is kept constant, and the dryness of the developer is kept constant at any place to stabilize the image formation. . That is, by keeping the amount of the circulating developer constant within a predetermined range, the developer can be stably supplied to the developing roller or the supply roller, and the image formation is also stabilized. For example, in the circulation path (on the side of the first screw) close to the developing roller or the supply roller, when the downstream portion and the upstream portion have different densities, there is a difference in the image density, and especially, the rustiness of the developer is When the amount is lower than the predetermined amount, the image density is lowered and it becomes impossible to obtain a good image. Further, if an excessive amount of developer is added, there is a problem such as leakage from a regulating roller or a partition plate in the developing device.

When a two-component developer consisting of a carrier and a toner is used, the toner is replenished so as to have a predetermined density with respect to a fixed amount of the carrier. It is desirable to regulate the concentration of the developer within a predetermined range.If a developer with a concentration outside this range is used, the image formation will be affected, and the density of the output image will be dark or light. To become. On the other hand, if the concentration of the developer is too high, the developer is not sufficiently charged, causing fog and affecting the image.

On the other hand, the developer consumed by the image formation is quantitatively replenished by the replenishing means at the predetermined position of the above-mentioned circulation path. This replenishment causes a difference in the amount (roughness or concentration) of the developer in the circulation path. In the case of a one-component developer, the height difference is made constant, and in the case of a two-component developer, the difference in height is made constant, and the concentration of the developer is made constant to prepare for image formation. By shortening the time of the developer circulation step, the start of image formation can be accelerated.

[0007]

When a sheet material of a small size is used, the time required for the circulation of the developer is short because the distance of the circulation path is relatively short. When using a sheet material, the distance of the circulation path becomes long, and it takes only a short time to keep the amount of the developer constant over the axial direction and to keep the concentration of the developer constant. It has a problem that it cannot. Especially during image formation
When the consumption amount of the developer is increased due to continuous solid black image formation, the replenishment amount of the developer cannot keep up with the development roller or the supply roller side with respect to the conveying direction of the first conveying unit. On the downstream side, the dryness of the developer becomes insufficient, or the concentration of the developer becomes low. For this reason, the sheet material on which the image is formed has a partial difference in density.

The replenishment sensor has a replenishment means for replenishing the developer by detecting the lowered dryness or density of the developer. Generally, the developer replenishment port is separated from the developing roller or the supply roller. It is preferable to position it on the downstream side in the carrying direction of the second carrying means located at the open position. That is, the developer can be supplied to the developing roller or the supplying roller sooner if it is located closer to the developing roller or the supplying roller. However, in the replenishment sensor provided at this position, the distance from the upstream to the downstream in the conveyance direction of the second conveyance means is long, and it takes time for the portion where the amount of the developer is small to reach the replenishment sensor. Will end up. Then, there is a problem that images formed by continuous image formation by the sensor for replenishment become thinner images.

The present invention has been made in view of the above-mentioned problems. Even when a large amount of developer is consumed by image formation, the consumed developer is immediately detected and the following An object is to provide an image forming apparatus including a developing device that does not affect image formation.

[0010]

In order to solve the above-mentioned problems, the present invention provides a developing device having means for circulating the developer stored in the container, which is provided on the member side for supplying the developer to the image carrier. In the image forming apparatus provided with the image forming apparatus, a sensor for detecting the amount of the developer is provided at a position where the developer is separated from the member, and when the sensor detects that the amount of the predetermined developer is small, the image forming operation is performed. It is characterized by stopping the operation.

Further, the sensor is a sensor for detecting the dryness of the developer, the member is a developing roller, and the member is a supply roller.

Further, there is provided a first transporting means which is provided on the side of the member for supplying the developer to the image carrier and transports the developer stored in the container in the axial direction of the image carrier, and the first transporting means. Between a second conveyance unit that is provided substantially parallel to the first conveyance unit and conveys the developer in a direction opposite to the conveyance direction of the first conveyance unit, and between the first conveyance unit and the second conveyance unit. A partition member provided in the first transporting means, and a first opening communicating with the first transporting means from the second transporting means, and a second opening from the first transporting means to the second transporting means. And an image forming apparatus having a developing device having a second opening communicating with the conveying means, the sensor for detecting the amount of the developer in the vicinity of the second opening and the sensor for determining a predetermined amount during image formation. When it is detected that the amount of developer is less than Allowed to continue circulating operation while, characterized in that a control means for stopping the operation of the next image formation.

Further, the control means further restarts the image forming operation when the sensor detects that a predetermined amount of developer has been reached, and the sensor is preferably provided. The sensor is provided on the upstream side with respect to the transport direction of the second transport means so as to detect the amount of the developer that has passed through the second opening, and the sensor has a predetermined amount of developer. When it is detected that the amount is smaller, the developer carrying speed of the first carrying means and the second carrying means is increased.

Further, the developing device has a replenishing means for replenishing a replenishing developer to a predetermined replenishing place of the second conveying means, and detects the amount of the developer on the downstream side of the replenishing place. A replenishment sensor that outputs a signal for operating the replenishment means is provided, and is controlled independently of the control means that stops the image forming operation based on the signal from the sensor. Is characterized by.

As described above, a sensor for detecting the density of the developer or the concentration of the developer is provided in the vicinity of the second opening provided in the partition member in which the flow of the developer is turned back toward the second conveying means. The amount of the developer consumed during image formation is detected, and if there is no developer based on this detection signal, the next image formation is stopped. During this period, the circulation operation by the first transporting means and the second transporting means continues, and the replenishment sensor provided on the downstream side of the second transporting means and downstream of the toner replenishing port has a small amount of developer. When it is detected, the replenishment toner is replenished. Further, the sensor detects that the dryness or the density of the developer has become equal to or less than a predetermined amount, and increases the transport speed of the first and second transport means, thereby preparing for image formation in a short time.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic sectional view of an image forming apparatus equipped with a developing device. FIG. 2 shows a schematic top view of the developing device as seen from the direction of arrow A in FIG. The developing device is provided close to or in contact with the image carrier, and has a non-magnetic property.
An example of a developing device using a component developer will be shown.

A developing device is provided in the image forming apparatus 40. The developing device 1 stores a developing roller 2, a supply roller 3, a developer stirring device 4, a toner replenishing means 5, and a developer. And a layer thickness regulating member 7. The developing roller 2 is rotated in the direction of the arrow, is made of an elastic roller and is arranged parallel to the image carrier 8, and presses the image carrier 8 with a predetermined pressing force to bring it into contact with a predetermined nip width. ing. The surface of the developing roller 2 has a predetermined thickness of non-magnetic material 1.
A blade or roller as the layer thickness regulating member 7 for forming the layer of the component developer is in contact therewith. A predetermined bias voltage is applied to the layer thickness regulating roller rotating in the arrow direction as the layer thickness regulating member 7, and the developing roller 2 is rubbed by this bias voltage and the developing roller 2 and the layer thickness regulating member 7. The layer thickness of the developer above is regulated and charged. The supply roller 3 is made of a foamed elastic material such as sponge that rotates in the direction of the arrow, and is pressed against the developing roller 2 with a predetermined pressing force, so that the developer is rubbed against the developing roller 2 and supplied. ing.

The developer stirring means 4 is provided in close proximity along the axial direction of the supply roller 3, and supplies the developer stored in the container 6 while conveying the developer in the axial direction of the supply roller 3. Means 9, first conveying means 9 and second conveying means 10 provided in parallel with the first conveying means 9 for conveying the developer in a direction opposite to the conveying direction of the first conveying means 9. And a partitioning member 11 provided between the second transporting means 10 and the developer for partitioning the developer. In the vicinity of both ends of the partition member 11, there is provided a first opening 12 which communicates with the first carrying means 9 from the second carrying means 10 and sends the developer to the first carrying means.
And a second opening 13 for communicating the developer from the first transporting means 9 to the second transporting means 10 and for sending the developer to the second transporting means. The first transfer means 9 and the second transfer means 10 are provided with a spiral stirring blade 1 on the outer peripheral surface of the rotary shaft 20.
A screw having 9 is preferably used. A shaft is rotatably supported at both ends of the developing device via bearings and the like, and is driven by a drive source (not shown) so that the stirring blade 19 is rotated in the arrow direction to convey the developer to the downstream side. There is.

As shown in FIG. 2, the first transfer means 9, the second opening 13, the second transfer means 10, and the first opening 1 are provided.
A circulation path that circulates the developer in the direction of the arrow is formed by the second path. The developer conveyed by the first conveying means 9 is supplied to the peripheral surface portion of the adjacent supply roller 3 in the axial direction. The peripheral surface portion of the supply roller 3 is conveyed while being circulated so as to have a uniform dryness so that a constant developer is always in contact.

The partition member 11 has a height such that the developer does not move between the first transporting means 9 and the second transporting means 10 except the first opening 12 and the second opening 13. And a metal plate or a synthetic resin plate is preferably used.
Further, it may be integrally formed with the container. First opening 1
The second and second openings 13 are formed by cutting out a part of both ends of the partition member. The first opening 12 and the second opening 13 may be located near the ends.

The replenishing means 5 has a hopper 14 for replenishing the replenishing developer therein, a replenishing port 15 for replenishing the developer agitating device 4 with the developer, and a replenishing port 15 for the developer stored in the hopper 14. A replenishment member 16 such as a stirring blade or a coil spring for quantitatively replenishing the developer agitator 4 from the above, and a replenishment sensor 17 for detecting that the amount of the developer in the developer agitator 4 has decreased. . Replenishment sensor 17
Is for detecting whether or not the bulk of the developer has reached a predetermined position, and a piezoelectric sensor is preferably used.
The replenishment sensor 17 detects that the dryness of the developer has become low, and the replenishment member 16 is operated for a predetermined time based on this detection signal to replenish the developer agitator 4 with the replenishment developer. . In the embodiment, it is located downstream of the second conveying means 10.

Since the developer consumed by the image formation is supplied from the supply roller 3, the developer carried from the upstream side in the carrying direction of the first carrying means 9 is carried while being gradually reduced in the first carrying direction. When it reaches the downstream side of the transport means 9 in the transport direction, it may be almost lost. Particularly when a black solid image is continuously copied, the developer is consumed so much that it adversely affects the next image formation. In order to solve this problem, based on the signals from the sensor 18 and the sensor 18 for detecting the amount of the developer in the vicinity of the second opening 13 where the developer is folded back from the first carrying means 9 to the second carrying means 10. And a control unit 30 for controlling the image forming operation. The sensor 18 is a piezoelectric sensor that detects the dryness of the developer, and when the sensor surface is no longer covered with the developer, a detection signal indicating no developer is issued. Then, when the sensor 18 detects that the developer has become lower than a predetermined amount (amount) of the developer, the control unit 30 continues the developer circulation operation based on the detection signal of the sensor 18 to start the next image formation. Stop the operation.
Next, when the sensor 18 detects that the predetermined amount of developer has been reached, the control unit 30 restarts the image forming operation.

The position of the sensor 18 is the position of the second conveying means 10 for detecting the amount of the developer which has passed through the second opening 13.
Is preferably provided on the upstream side of. The developer pushed out by the first transporting means 9 accumulates a certain amount when it is folded back at the second opening, so that the malfunction does not occur. The sensor 18 is provided on the wall surface of the developing container 6 so as to face the second transport unit 10.

The amount of the developer means the amount of the developer which is continuously moved by the conveyance and is detected each time the sensor is positioned on the sensor. In the case of the one-component developer, the amount of the developer is large. Is detected, and a signal indicating no developer is output when it becomes lower than a predetermined level. Further, in the case of a two-component developer, the toner concentration of the developer in which the toner and the carrier are mixed is detected, and a signal indicating no developer is output when the concentration becomes lower than a predetermined concentration.

When the sensor 18 detects that the amount of the developer is less than the predetermined amount, it is preferable to increase the developer transport speed of the first transport means 9 and the second transport means 10. When the sensor 18 detects that the amount of the developer is not a predetermined amount, the control means 30 transmits the drive to the first conveying means 9 and the second conveying means 10 based on the detection signal of the sensor 18. The speed of the developer is increased by increasing the number of rotations of the driving means, and the time until the developer reaches a predetermined amount is further shortened.

A known method is used for the image formation, and a toner image is carried and fixed on the sheet material to form a permanent image through the steps of charging, exposure, development, and transfer. Stopping the operation indicates a standby state in which image formation can be performed whenever the developer reaches a predetermined amount.

With such a structure, when continuous copying is performed, the developer is consumed as an image is formed on the sheet material. In particular, when an image with many solid black portions is formed in one image formation, the consumption amount of the developer increases, and the developer is conveyed toward the downstream while being consumed, so that the developer is conveyed while moving. The developer is consumed at a position at substantially the same position, so that there is a portion where there is no developer to the extent that it affects the next image formation. This part is first
The transport means moves to the downstream side, then turns back at the second opening 13 and moves to the downstream side by the second transport means 10. Then, the portion without the developer reaches the sensor 18 provided on the upstream side in the transport direction of the second transport means.
The sensor 18 detects the absence of the developer, and the control means stops the next image formation based on the detection signal. During this time, the developer agitator is circulating, and if the dryness of the developer is uniform and can hold a predetermined amount, the image formation is restarted. When the developer has a low dryness and passes the replenishment sensor 17 provided on the downstream side of the second conveying unit 10, the replenishment sensor 17 detects the absence of the developer and replenishes the developer for a predetermined time 15 From the replenishment member 16. The dryness of the developer becomes high and reaches the sensor 18 to detect that the developer is sufficient. Based on this detection signal, the control means restarts image formation or informs the operator that the preparation is completed.

In the embodiment, an example in which a one-component developer is used has been described, and the configuration in which the sensor detects the dryness of the developer has been described, but the configuration in which the concentration of the developer is detected by using the two-component developer is described. In this case, it is preferable to provide a magnetic permeability sensor for measuring the toner concentration of the developer.

[0029]

According to the present invention, a sensor for detecting the amount (roughness or concentration) of the developer near the second opening, and the circulation operation of the developer when the sensor detects that the amount is less than the predetermined amount of developer. The control means for stopping the next image forming operation while continuing the operation, and restarting the image forming operation when the sensor detects that the predetermined amount of the developer has been reached. Can be detected in the shortest time, and image formation can be performed without waste.

Further, since the sensor is provided on the upstream side of the second conveying means so as to detect the amount of the developer which has passed through the second opening, the developer once pushed by the first conveying means is removed. Since it accumulates and is then folded back at the second opening and returned by the first transport means, there is no malfunction of the sensor, and the amount of developer can be accurately determined. Further, when the sensor detects that the amount of the developer is less than the predetermined amount, the speed of the developer transport of the first transport unit and the second transport unit is increased to prepare for image formation in a shorter time. Done.

Further, since the control means for stopping the image forming operation on the basis of the signal of the sensor is controlled independently of the detection signal of the replenishing sensor, it is known that there is no developer by the sensor. At this time, the replenishing developer is supplied, and the developer is supplied to a place where the dryness or the concentration of the developer is still sufficient, and it is possible to prevent a state where stable control cannot be performed.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an example of an image forming apparatus including a developing device.

FIG. 2 is a schematic top view of the developing device viewed from the direction of the arrow in FIG.

[Explanation of symbols]

1 Development device 2 developing roller 3 supply rollers 4 Developer stirring device 5 Supplying means 9 First transport means 10 Second Transport Means 11 partition members 12 First opening 13 Second opening 17 Supply sensor 18 sensors 30 control means 40 image forming apparatus

Continued front page    F-term (reference) 2H027 DD02 DE07 DE10 EA06 EC06                       EC11 EF09                 2H077 AA15 AB02 AB15 AB18 AC02                       AD06 AD13 AD14 AD23 AE02                       AE08 DA15 DA44 DA74 DB02                       DB18 DB21 EA14 EA15 FA21

Claims (12)

[Claims] 1. An image forming apparatus including a developing device, which is provided on a member side for supplying a developer to an image carrier and has means for circulating a developer stored in a container, wherein the developer is separated from the member. An image forming apparatus, wherein a sensor for detecting the amount of the developer is provided at a position, and when the sensor detects that the amount of the predetermined developer is small, the image forming operation is stopped. 2. The image forming apparatus according to claim 1, wherein the sensor is a sensor that detects the dryness of the developer. 3. The image forming apparatus according to claim 1, wherein the member is a developing roller. 4. The image forming apparatus according to claim 1, wherein the member is a supply roller. 5. A first conveying unit which is provided on a member side for supplying the developer to the image carrier and conveys the developer stored in the container in the axial direction of the image carrier, and the first conveying unit. Between a second conveyance unit that is provided substantially parallel to the first conveyance unit and conveys the developer in a direction opposite to the conveyance direction of the first conveyance unit, and between the first conveyance unit and the second conveyance unit. A partition member provided in the first transporting means, and a first opening communicating with the first transporting means from the second transporting means, and a second opening from the first transporting means to the second transporting means. And an image forming apparatus having a developing device having a second opening communicating with the conveying means, the sensor for detecting the amount of the developer in the vicinity of the second opening and the sensor for determining a predetermined amount during image formation. When it is detected that the amount of developer is less than An image forming apparatus comprising: a control unit that stops the next image forming operation while continuing the ring operation. 6. The image according to claim 5, wherein the control unit further restarts the image forming operation when the sensor detects that a predetermined amount of developer has been reached. Forming equipment. 7. The sensor is preferably provided on the upstream side with respect to the transport direction of the second transport means so as to detect the amount of the developer that has passed through the second opening. The image forming apparatus according to claim 5 or 6. 8. The developer transport speed of the first transport means and the second transport means is increased when the sensor detects that the amount of developer is less than a predetermined amount. Item 7. An image forming apparatus according to items 5 to 7. 9. The image forming apparatus according to claim 5, wherein the sensor is a sensor that detects the dryness of the developer. 10. The developing device has a replenishing means for replenishing a replenishing developer to a predetermined replenishing place of the second conveying means, and detects the amount of the developer on the downstream side of the replenishing place. A replenishment sensor that outputs a signal for operating the replenishment unit is provided, and is controlled independently of the control unit that stops the image forming operation based on the signal of the sensor. The image forming apparatus according to claim 5, wherein the image forming apparatus is an image forming apparatus. 11. The image forming apparatus according to claim 5, wherein the member is a developing roller. 12. The image forming apparatus according to claim 5, wherein the member is a supply roller.