Developing device

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Industrial application field]

The present invention relates to a developing device that stores a two-component developer composed of toner and a carrier and supplies toner to the surface of the photoconductor in order to visualize an electrostatic latent image on the surface of the photoconductor in an electrophotographic apparatus such as a copying machine. It is a thing.

【0002】

[Conventional technology]

For example, in dry copiers and the like, a developing device that visualizes (develops) an electrostatic latent image on the surface of a photoconductor with a two-component developer composed of a carrier and toner is often used. In such a developing apparatus, the toner is consumed by the developing operation, while the carrier is not consumed and remains in the developing apparatus. Therefore, as the frequency of stirring increases, the carrier that is agitated together with the toner in the developing apparatus deteriorates due to the peeling of the resin coat layer on the surface and the adhesion of the toner on the surface, and the charging performance of the developer gradually deteriorates. To do.

【0003】

Therefore, in addition to the replenishment of toner consumed by the developing operation, a device capable of suppressing a decrease in charging performance by replenishing carriers in the developing device little by little is disclosed in, for example, Japanese Patent Publication No. 2-21591. Has been done. In the apparatus, the developer in the developing tank, which is excessive due to the replenishment of the carrier, overflows from the developing tank overflow outlet provided on the wall surface of the developing tank, is discharged, and is collected in the developing agent recovery container. By repeating such replenishment and discharge sequentially, the deteriorated developer in the developing tank is replaced with the newly supplied toner and carrier, thereby maintaining the charging performance and suppressing the deterioration of the copying image quality. It has become like.

【0004】

[Problems to be Solved by the Invention]

However, in the developing apparatus that gradually replenishes and discharges carriers as described above, the amount of the developer in the developing tank tends to fluctuate, which may lead to inaccurate control of the toner concentration and the inability to maintain good image quality. There is.

【0005】

That is, in the developing apparatus, the toner is replenished based on the detection of the toner concentration in the developing tank by, for example, the toner concentration sensor including the magnetic permeability sensor. Further, in a developing apparatus in which carriers are not replenished and discharged, the fluctuation in the amount of the developer in the developing tank is small because it is only the change in the amount of toner. Therefore, if the toner concentration sensor is provided at a position where it simply comes into contact with the developer, the toner concentration can be appropriately controlled.

【0006】

On the other hand, in the developing device that gradually replenishes and discharges the carrier, the fluctuation in the amount of the developing agent in the developing tank is larger than that of the developing device that does not replenish and discharge the carrier immediately after replenishing the carrier and discharging the developer. Immediately after, it becomes large. In particular, when a copying machine equipped with this developing device is a small personal machine or the like that can be easily moved, a large amount of developing agent may be discharged from the developing agent overflow outlet at a time due to impact and inclination during movement. Therefore, the fluctuation in the amount of the developer becomes remarkable.

【0007】

Therefore, since the amount of the developer in the developing tank varies and is not always constant, there is a problem that the toner concentration cannot be controlled by the magnetic permeability sensor provided in the developing tank.

【0008】

An object of the present invention is to provide a developing apparatus capable of controlling the toner concentration by measuring the amount of the developing agent based on the relationship between the value of the magnetic permeability sensor and the amount of the developing agent.

【0009】

[Means for solving problems]

In order to solve the above problems, in the developing apparatus of the present invention, a stirring roller for stirring the developing agent and a developing roller for supplying the developing agent to the photoconductor are rotatable in a developing tank containing a developing agent composed of toner and a carrier. A developing agent collecting unit is provided in the developing tank to detect the toner concentration in the developing tank, and further communicates with the discharging unit formed in the developing tank to store the discharged developing agent. Is provided, and the carrier developer containing the carrier is sequentially replenished from the carrier replenishment unit to the developing tank, and the toner is replenished from the toner replenishing unit into the developing tank based on a predetermined toner concentration, while the discharge unit The following measures are taken in the developing apparatus in which the developing agent in the developing tank is discharged.

【0010】

That is, it was calculated as a developer amount detecting means for detecting the developer amount in the developing tank and a sensor value calculating means for calculating an appropriate toner concentration sensor value from the detected developer amount. It is provided with a control means for controlling the toner concentration in the developing tank based on the value of the toner concentration sensor and the value of the toner concentration sensor.

【0011】

The developer amount detecting means includes a magnetic permeability sensor, a developing unit developer amount detecting means for detecting the amount of the developing agent in the developing agent recovery unit from the value of the magnetic permeability sensor, and a developing tank from the developing agent amount in the developing agent collecting unit. It may include a developer amount calculation means for calculating the amount of the developer inside.

【0012】

Further, the developer amount detecting means may include a plurality of optical sensors continuously provided in the developing tank in the vertical direction.

【0013】

[Action]

With the above configuration, the amount of developer in the developing tank is first detected by the developer amount detecting means. Next, the sensor value calculation means calculates an appropriate toner concentration sensor value in the developing tank from the obtained amount of the developing agent in the developing tank. Then, toner is replenished from the toner replenishing unit into the developing tank according to the difference between the calculated sensor value and the actual toner concentration sensor value, and the toner concentration is controlled.

【0014】

When the developer amount detecting means includes a magnetic permeability sensor, a collecting unit developer amount detecting means, and a developing agent amount calculating means, the magnetic permeability sensor value and the developing agent amount are determined from the value of the magnetic permeability sensor. The amount of the developer in the developer recovery unit is determined by the relationship, and the amount of the developer in the developing tank is calculated using the amount of the developer in the developing unit.

【0015】

When the developer amount detecting means includes a plurality of optical sensors continuously provided in the developing tank in the vertical direction, the developer is provided at a position where the continuous ON or OFF of the plurality of optical sensors changes. By identifying the photosensor, the height of the developer, that is, the amount of the developer is detected.

【0016】

[Example]

[Example 1] An embodiment of the present invention will be described below with reference to FIGS. 1 to 9.

【0017】

As shown in FIG. 2, in a copying machine configured by applying the present invention, a document mounting table 1 is provided on an upper surface portion, and an exposure optical system 2 is arranged under the document mounting table 1. .. The exposure optical system 2 includes a light source lamp 3 that scans a document (not shown) placed on the document mounting table 1 while irradiating it with light, and a plurality of reflectors that guide the reflected light from the document to the photoconductor 4. It consists of 5 ... and a lens unit 6 arranged in the optical path of reflected light.

【0018】

On the outer periphery of the photoconductor 4, a charging charger 7 that charges the surface to a predetermined potential, an image-to-image eraser (not shown), a developing device 8 that develops an electrostatic latent image formed on the surface of the photoconductor 4, and photosensitivity. A transfer charger 9 for transferring the toner image on the surface of the body 4 onto paper, a cleaning device 10 for collecting the residual toner on the surface of the photoconductor 4, a static eliminator (not shown), and the like are provided. Further, a timing roller 11, a transport roller 12, a paper cassette 13 and a paper feed roller 14 for supplying paper at a predetermined timing are provided on the paper input side with respect to the photoconductor 4, while the paper output side with respect to the photoconductor 4 is provided. Is provided with a fixing device 15 for fixing the toner image transferred on the paper to the paper.

【0019】

As shown in FIG. 1, the developing apparatus 8 has a container-shaped developing tank 16, and inside the developing tank 16, a developing roller 17 made of a magnet roller and a stirring roller 18 are rotatably arranged. Has been done. The developer housed in the developing tank 16 is composed of a carrier and a toner, and the carrier made of a magnetic material has a resin coating layer on the surface which suppresses adhesion of the toner. When the carrier and the toner are agitated by the stirring roller 18, the toner is triboelectrically charged. The developing roller 17 attracts carriers by magnetic force to form a magnetic brush and conveys the toner, so that the toner attached to the carriers by Coulomb force is supplied to the photoconductor 4 and is adsorbed by the electrostatic latent image of the photoconductor 4. And development is performed. The height of the spikes of the above magnetic brush is regulated by Doctor 19.

【0020】

An opening for replenishing the developer is formed in the upper wall portion 16a of the developing tank 16, and the developing agent supply unit 20 is fitted into the opening for replenishing the developing agent from above. The inside of the developer supply unit 20 is divided into two chambers, a toner storage chamber 20a (toner replenishment unit) and a carrier developer storage chamber 20b (carrier replenishment unit). Toner is stored in one toner storage chamber 20a, and a developer consisting only of carriers in the other carrier developer storage chamber 20b, or a developer in which toner is mixed in a predetermined ratio in carriers (hereinafter, carrier development). (Called an agent) is stored.

【0021】

A toner replenishment roller 21 and a carrier developer replenishment roller 22 are provided at the bottom of each storage chamber 20a and 20b, respectively, and the toner in the toner storage chamber 20a is discharged by rotationally driving the toner replenishment roller 21. In addition, as the carrier developer replenishment roller 22 is rotationally driven, the carrier developer in the carrier developer storage chamber 20b flows down in the developing tank 16 by an amount corresponding to the driving time of each of the rollers 21 and 22. Is supplied to.

【0022】

On the other hand, a container-shaped recovery container 23 (developer recovery section) having an open side surface is detachably attached to the side wall portion 16b of the developing tank 16. A discharge opening 26 (discharge part) is formed in the side wall portion 16b so as to allow the inside of the developing tank 16 to communicate with the inside of the collection container 23 to the left and right. Further, a receiving portion 16c for supporting the recovery container 23 is formed on the discharge opening 26 side of the bottom wall portion 16d of the developing tank 16. The receiving portion 16c is provided with a magnetic permeability sensor 24 that senses the amount of the developer in the collection container 23.

【0023】

As shown in FIGS. 3 and 4, the recovery container 23 is provided with a recovery opening 27 on the side wall that communicates with the discharge opening 26 of the developing tank 16, and the developing agent to be discharged is provided below the opening 27. A protrusion 27a is provided to prevent spillage. Further, a recess 23a for fitting the recovery container 23 into the convex portion 16e formed on the bottom wall portion 16d of the developing tank is formed at the bottom of the recovery container 23. A hole 28 for mounting the magnetic permeability sensor 24 is formed in the bottom wall portion 16d of the developing tank. Since the magnetic permeability sensor 24 measures the magnetic permeability of the carrier, it does not need to be in contact with the developer, and may be configured to be in close contact with the recovery container 23 as described above.

【0024】

To attach the collection container 23 to the developing tank 16, align the concave portion 23a of the collecting container 23 with the convex portion 16e of the developing tank 16 and slide the collecting container 23 in the A direction. As a result, the protrusion 27a is mounted so as to be in contact with the lower part of the protrusion 26a formed around the discharge opening 26, and the recovery opening 27 of the recovery container 23 and the discharge opening 26 of the developing tank 16 are horizontally connected. ..

【0025】

Next, the copying operation in the copying machine having the above configuration will be described.

【0026】

When the power switch (not shown) is turned on, the warm-up process is performed first. When the copy start switch 31, which will be described later, is turned on after this is completed, the document placed on the document mounting table 1 is scanned by the light source lamp 3 of the exposure optical system 2. The reflected light from the document at this time is irradiated to the photoconductor 4 via the reflector 5 ... and the lens unit 6, and electrostatically latent on the surface of the photoconductor 4 charged to a predetermined potential by the charging charger 7. An image is formed. The electrostatic latent image is then developed by the toner supplied from the developing apparatus 8. The toner image on the surface of the photoconductor 4 is transferred to the paper supplied from the paper feed cassette 13 by the transfer charger 9, and is heat-fixed on the paper by the fixing device 15. As a result, a copy image corresponding to the original image is formed on the paper.

【0027】

In order to control such a series of copying operations, as shown in FIG. 5, a control device 32 composed of a microcomputer is provided in the copying machine, and the control device 32 is turned on by the copy start switch 31. The operation signal is input. Further, a copy counter 33 for counting the cumulative number of copying operations is further provided, and this count value (hereinafter referred to as a copy count value) n is also input to the control device 32.

【0028】

When the copying operation as described above is repeated, the toner in the developer stored in the developing tank 16 of the developing apparatus 8 is gradually consumed, and the ratio of the toner to the carrier, that is, the toner concentration is lowered. A toner concentration sensor 25 for detecting the change in the toner concentration is provided in the developing tank 16, and the toner is replenished using the value of the toner concentration sensor 25 by the toner concentration control method described later.

【0029】

The replenished toner is agitated with the developer in the developing tank 16, controlled to a constant charge amount, supplied to the photoconductor 4, and used for development. On the other hand, since the carriers in the developer are not reduced and are used repeatedly, they gradually deteriorate due to stirring by the developing roller 17 and the stirring roller 18 and contact with the photoconductor 4. When the carriers deteriorate in this way, it becomes impossible to impart a predetermined amount of charge to the toner, resulting in deterioration of image quality. Therefore, by newly replenishing the carriers in the developing tank 16 and replacing them with the deteriorated carriers in the developing tank 16, the above-mentioned decrease in charging performance can be suppressed. For this reason, the control device 32 also controls the supply of the carrier developer from the carrier developer storage chamber 20b.

【0030】

Hereinafter, the procedure for controlling the replenishment of the carrier developer by the control device 32 will be described with reference to FIG.

【0031】

Replenishment cycle Y_C, Replenishment time t_YCSince the set values such as etc. are changed according to the cumulative number of copies, first, the copy count value n of the copy counter 33 is compared with the set value switching count value n (i) each time copying is executed (S1). ). A plurality of values for n (1), n (2) ... are stored in the storage unit in the control device 32, and are sequentially read out by the processing of S1 according to the parameter i. Further, in the above storage unit, the replenishment cycle value Y corresponds to each set value switching count value n (i) (i = 1,2, ...)._C(i), replenishment time t_YC(i) is stored as a data table.

【0032】

When it is determined in S1 that the copy count value n has reached the set value switching count value n (i), each Y corresponding to n (i) at this time is determined._C(i), t_YC(i), replenishment cycle Y_C, Replenishment time t_YCThen, a process of newly setting is performed in place of the previous value (S2), and then 1 is added to the parameter i (S3).

【0033】

After performing the processes S1 to S3 for switching the set value as described above, the copy count value n described above is changed to the replenishment timing value M._YCompare with (S4). n is M_YWhen it has not reached, the process of returning to S1 is performed. On the other hand, n is M_YWhen it reaches, the carrier developer replenishment roller 22 is subsequently turned on (S5). As a result, replenishment of the carrier developer in the carrier developer storage chamber 20b to the developing tank 16 is started. At the same time, the time counting of the replenishment time monitoring timer is started (S6), and the time counting time with this timer is t._YHowever, the replenishment time t_YCBy turning off the carrier developer replenishment roller 22 (S7), the carrier developer replenishment is stopped.

【0034】

And the above replenishment timing value M_YIn addition, the replenishment cycle Y_CIs added (S8) and returns to S1. As a result, the replenishment timing value M_YIs updated to the cumulative number of copies to be replenished next.

【0035】

By repeating such control, the copy becomes Y_CEach time the processing is performed, the carrier developer replenishing roller 22 is driven for a predetermined time, and the carrier developer in an amount corresponding to the driving time is replenished to the developing tank 16.

【0036】

When the carrier developer is replenished, the developer in the developing tank 16 gradually increases. Since the discharge opening 26 is located on the side wall portion 16b of the developing tank 16, the increased developer overflows and accumulates in the collection container 23. By repeating the replenishment of the carrier developer and the discharge of the developer in the developing tank 16 in this way, the deteriorated developing agent in the developing tank 16 is sequentially replaced with a fresh developing agent.

【0037】

By the way, FIG. 7 shows the relationship between the amount of the developer and the magnetic permeability sensor output value at an arbitrary toner concentration. As can be seen from this, there is a one-to-one relationship between the amount of developer and the output value of the magnetic permeability sensor. That is, if the toner concentration is constant, the amount of the developer can be detected from the output value of the magnetic permeability sensor.

【0038】

Therefore, a method of calculating and controlling the amount of the developer in the developing tank 16 using the above relationship will be described with reference to the flowchart of FIG.

【0039】

First, the amount of developer M, which is the amount of developer filled in the initial developing tank 16._dIs memorized (T1). Next, it is determined whether the timing is such that the carrier developer can be replenished (T2). If not possible, continue copying (T9). If possible, rotate the carrier developer replenishment roller 22 for a predetermined time to a predetermined amount M._aReplenish (j) (T3). The value detected by the magnetic permeability sensor 24 attached to the bottom of the collection box 23 is input to the control device 32 (T4). The amount of developer M in the collection box 23 based on the value of the magnetic permeability sensor 24 input in the control device 32 which is the means for detecting the amount of developer in the recovery unit._{b b}Calculate (j) from the data table (T5). Amount of developer in collection box 23 when replenished last time M_{b b}The amount of developer M collected in the collection box 23 this time, taking the difference from (j-1)._cCalculate (j) (T6). The amount of developer M (j) in the developing tank 16 is calculated by the following equation (1) (T7).

【0040】

M (j) = M_a(j) -M_c(j) + M (j-1) (1) 1 is added to the parameter j (T8).

【0041】

By repeating such an operation, the amount of the developer in the developing tank 16 can be calculated. In addition, M_{b b}The data table for calculating (j) is a table showing a graph of the relationship between the value of the magnetic permeability sensor and the amount of the developer for each toner concentration. Further, the operations of T6 and T7 are performed by the control device 32 which is a developer amount calculation means. Further, the magnetic permeability sensor 24, the recovering unit developer amount detecting means, and the control device 32 which is a developing agent amount calculating means constitute the developing agent amount detecting means.

【0042】

Next, the toner concentration control procedure will be described with reference to FIG. The amount of developer in the developing tank 16 is calculated according to the flowchart shown in FIG. 8 (U1). In the control device 32, which is a sensor value calculation means, a target sensor value is set based on the calculated developer amount and the predetermined toner concentration. At this time, the relationship between the amount of the developer and the magnetic permeability sensor is used (U2). Compare the target sensor value with the value of the toner concentration sensor 25 (U3). When the value of the toner concentration sensor 25 is larger than the target sensor value, the toner replenishment roller 21 is rotated to replenish the toner (U5). If the target sensor value is larger than the value of the toner density sensor 25, the copying operation is performed (U4).

【0043】

By repeating the above operation, the toner concentration can be controlled. The operations of U3 and U5 are performed by the control device 32 which is a control means.

【0044】

With the above configuration, the magnetic permeability sensor 24 and the control device 32 detect the amount of the developer in the developing tank 16, and the detected amount of the developer is used to determine the appropriate value of the toner concentration sensor in the control device 32. It is calculated. Then, the calculated value of the toner concentration sensor is compared with the value of the toner concentration sensor 25 provided in the developing tank 16, and the toner concentration is controlled by replenishing the toner from the toner storage chamber 20a as needed. Will be done.

【0045】

Therefore, in the developing apparatus 8 having a configuration in which the toner and the carrier developer are replenished while the developer is sequentially discharged, the toner concentration is within a range in which there is no practical problem even if the amount of the developer in the developing tank 16 changes. Can be controlled with. Further, even if a large amount of developer is discharged from the developing tank 16 due to an impact or tilt when the copying machine equipped with the developing device 8 is moved, the amount of the developing agent in the developing tank 16 is detected and the amount of the developing agent is detected. Since the toner concentration is controlled according to the amount, a stable toner concentration is maintained without expanding the control range.

【0046】

[Example 2] Other examples of the present invention will be described below with reference to FIGS. 10 to 12. For convenience of explanation, members having the same functions as the members shown in the above-described embodiment are given the same member numbers, and the description thereof will be omitted.

【0047】

In this embodiment, as shown in FIG. 10, a plurality of optical sensors 29 ... (developer amount detecting means) are adjacent to each other on the side wall portion of the developing tank 16 in the upward direction from the vicinity of the bottom wall portion 16d. Is provided.

【0048】

As shown in FIG. 11, the optical sensor 29 has a light emitting element 35 that emits light and a light receiving element 36 that receives light from the light emitting element 35, and as shown in FIG. 12, the light from the light emitting element 35 is received. When the element 36 is reached, the light receiving element 36 is turned on, and a LOW level signal is input to the connected control device 34. On the other hand, when the light from the light emitting element 35 does not reach the light receiving element 36, the light receiving element 36 is turned off and a HIGH level signal is input to the control device 34.

【0049】

With the above configuration, if the developer is between the light emitting element 35 and the light receiving element 36 in the developing tank 16, the light receiving element 36 does not receive light, so that a HIGH level signal is input to the control device. That is, when the developer is at an arbitrary height, the developer enters between the light emitting element 35 and the light receiving element 36 of the optical sensor 29 below that height, so that the light of the light emitting element 35 reaches the light receiving element 36. do not. Further, since the developer does not enter between the light emitting element 35 and the light receiving element 36 in the optical sensor 29 located at a position equal to or higher than the height of the developing agent, the light of the light emitting element 35 reaches the light receiving element 36. Therefore, by providing a plurality of optical sensors 29 ... Adjacent to each other in the vertical direction in the developing tank 16, development in the developing tank 16 is performed from a position where the signal input to the control device 34 changes from the HIGH level to the LOW level. The height of the agent and the amount of the developer are detected.

【0050】

Using the amount of the developer in the obtained developing tank 16, the appropriate toner concentration sensor value is calculated in the control device 34 in the same manner as in the above embodiment. Then, the calculated value of the toner concentration sensor is compared with the value of the toner concentration sensor 25 provided in the developing tank 16, and the toner concentration is controlled by replenishing the toner from the toner storage chamber 20a as needed. Will be done.

【0051】

The height of the developer is set to the position where the signal input to the control device 34 changes from the HIGH level to the LOW level, but the position is not limited to this, and the position where the input signal changes from the LOW level to the HIGH level or It may be configured to be turned off when the light receiving element 35 receives light.

【0052】

With the above configuration, the amount of the developer in the developing tank 16 is detected by a plurality of optical sensors 29 ... Provided in the developing tank 16, so that the toner concentration is controlled based on the amount of the developing agent as in Example 1. Therefore, a stable toner concentration is maintained even if the amount of the developer in the developing tank 16 changes.

【0053】

[Effect of the invention]

As described above, the developing apparatus of the present invention is a means for detecting the amount of the developing agent in the developing tank and for calculating an appropriate value of the toner concentration sensor from the detected amount of the developing agent. It is configured to include a sensor value calculating means of the above, and a control means for controlling the toner concentration in the developing tank by the calculated value of the toner concentration sensor and the value of the toner concentration sensor.

【0054】

Therefore, even if the amount of the developer in the developing tank changes, an appropriate toner concentration sensor value is calculated based on the amount of the developing agent, and the toner concentration is easily controlled. As a result, it is possible to always set an appropriate toner concentration in the developing tank, and it is possible to maintain good image quality.

[Simple explanation of drawings]

[Figure 1]

An embodiment of the present invention is shown, and is a cross-sectional view showing an enlarged view of a developing device in a copying machine.

[Figure 2]

It is explanatory drawing which shows the whole structure of the copying machine which built-in the developing apparatus of FIG.

[Fig. 3]

It is a perspective view which shows the collection container.

[Fig. 4]

It is explanatory drawing which shows the attachment method of the collection container to a developing apparatus.

[Fig. 5]

It is a control block diagram of a copying machine.

[Fig. 6]

It is a flowchart which shows the processing procedure of the replenishment control of a carrier developer.

[Fig. 7]

It is a graph which shows the magnetic permeability sensor output value with respect to the amount of a developer.

[Fig. 8]

It is a flowchart which shows the method of calculating the amount of a developer in a developing tank.

[Fig. 9]

It is a flowchart which shows the toner density control procedure.

[Fig. 10]

It shows another embodiment of this invention, and is explanatory drawing which shows the optical sensor provided in the developing tank.

[Fig. 11]

It is a schematic perspective view which shows the optical sensor of FIG.

[Fig. 12]

It is a circuit diagram of the optical sensor of FIG.

[Explanation of symbols]

4 Photoreceptor 8 developing equipment 16 developing tank 16b side wall 17 Develop roller 18 Stirring roller 20a Toner storage room (toner supply section) 20b Carrier developer storage room (Carrier developer supply section) 23 Recovery container (developer recovery section) 24 Permeability sensor (developer amount detection means) 25 Toner concentration sensor 26 Discharge opening (discharge part) 29 Optical sensor (developer amount detection means) 32 Control device (developer amount detecting means, control means, sensor value calculating means, collecting unit developing agent amount detecting means, developing agent amount calculating means) 34 Control device (sensor value calculation means, control means)