JP2721366B2 - Toner density control device for image forming apparatus - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner density control device for an image forming apparatus, and more particularly, to a photoconductor on which a latent image is formed, and a developing unit for developing the photoconductor with toner. The present invention relates to a toner density control device of an image forming apparatus having the same.

[Conventional technology]

In a conventional image forming apparatus, such as a copying machine, which includes a photoconductor on which a latent image is formed and a developing unit that develops the latent image on the photoconductor with toner, a two-component developer generally including a toner and a carrier is used. Used. The developing unit has a toner density control device. As a toner concentration control device, a toner supply unit for supplying toner to the development unit, a toner sensor for detecting a toner concentration in the development unit,
2. Description of the Related Art There is known a sensor having a temperature sensor installed near a photoreceptor for detecting a temperature and a toner empty display for notifying that a replenishing toner is empty.
As the toner sensor, a sensor that detects the toner concentration in the developing unit by a change in inductance and outputs the result as a change in voltage is used. This toner sensor has a property that the output value increases as the toner concentration decreases.

In the toner concentration control device, when the output value from the toner sensor reaches a value at which toner replenishment is to be performed, the toner replenishing unit is operated, and when the output value reaches a value at which it is determined that all the replenishing toner has been consumed, the toner Perform an empty display. Thus, if the toner in the developing unit runs short, the toner is replenished, and if the toner for replenishment runs out, a warning to that effect is issued. In this case, due to the nature of the toner sensor used, when the temperature rises as shown by the broken line in FIG. 2, the output inductance from the toner sensor increases. Therefore, the temperature region is divided into, for example, a low-temperature region, a medium-temperature region, and a high-temperature region in accordance with the change in the output inductance of the toner sensor, and the control level is set to three levels in order to perform appropriate control for each temperature region. In FIG. 2, V _CL is the toner supply level in the low temperature region,
_EL toner empty level in the low temperature range, V _CM is the toner supply levels in the intermediate temperature range, V _EM toner empty level in the intermediate temperature range, V _CH toner replenishment level in the high temperature region, the V _EH is toner empty level in the high temperature region .

Incidentally, in the toner density control apparatus, for example, slightly lower than the output value V _CH of the toner sensor when the temperature was in the high temperature region (e.g., point A of FIG. 2)
Suppose it was From this state, if the temperature decreases and enters the medium temperature region (for example, point B in FIG. 2), the output value of the toner sensor will not change even if the toner concentration in the developing device does not change.
The toner empty indication is turned on even though the voltage exceeds _VEM and the toner can be replenished by the toner replenishing operation.

Therefore, such a toner concentration control device ignores the detection of the toner empty level and ignores the toner empty level for a certain period immediately after the transition from the high temperature region to the medium temperature region and for a certain period immediately after the transition from the middle temperature region to the low temperature region. The display is controlled not to light. On the other hand, since the toner replenishing operation is performed during the certain period, the output value of the toner sensor eventually becomes lower than the toner empty level, and the toner empty display does not light up after the certain period elapses. The calculation for the certain period is performed using a timer that is reset and started when the temperature shifts from the high temperature region to the medium temperature region or when the temperature shifts from the middle temperature region to the low temperature region.

[Problems to be solved by the invention]

In the conventional toner concentration control device, when the temperature shifts to the high-temperature region again before the measurement of the fixed period by the timer ends, and the temperature shifts to the low-temperature region again, the timer is reset again. It is started. Therefore, in such a configuration, when the temperature changes delicately many times between the high-temperature side region and the low-temperature side region, or just in the middle between the high-temperature side region and the low-temperature side region, so-called chattering occurs. In such a case, the timer is repeatedly reset and started, and the toner empty display is not performed forever. That is, in the conventional toner density control device, even when the toner is actually in the empty state, there is a case where the display to that effect is not performed. At this time, without displaying the toner empty,
The image density is significantly reduced. In some cases, the photosensitive drum may be damaged due to carrier pulling or the like.

An object of the present invention is to provide a toner empty state even when the detection of the toner empty level is ignored for a certain period so that the toner empty display is not turned on, and the image density is significantly reduced. It is an object of the present invention to provide a toner density control device capable of reliably preventing a photoconductor drum from being damaged by carrier pulling or the like.

[Means for solving the problem]

A toner density control device of an image forming apparatus according to the present invention is a toner density control device of an image forming device including a photoconductor on which a latent image is formed and a developing unit that develops the photoconductor with toner. As shown in FIG. 1, the toner concentration control device includes a toner sensor, a temperature sensor, a toner replenishment unit, a toner empty display unit, a first toner control unit, a second toner control unit, and a toner empty unit. A display restriction unit and a toner empty absolute display unit are provided.

The toner sensor is a sensor that detects the toner concentration of the developer in the developing unit based on a change in inductance and outputs the result as a change in voltage. The temperature sensor is a sensor installed near the developing unit to detect a temperature. The toner supply section is a supply section for supplying toner to the developing section. The toner empty display means is for notifying that the toner density in the developing section in the developing section has decreased and that all the replenishing toner has been consumed.

The first toner control unit is enabled when the temperature based on the temperature sensor is on the low temperature side, and activates the toner replenishing unit when the output value from the toner sensor reaches a first toner control value at which toner replenishment is to be performed. When the output value reaches a first toner empty value at which it is determined that all the toner for replenishment has been consumed, the toner empty display means is activated. The second toner control unit is enabled when the temperature based on the temperature sensor is on the high temperature side, and operates the toner replenishing unit when an output value from the toner sensor reaches a second toner control value at which toner replenishment is to be performed. When the output value reaches a second toner empty value at which it is determined that all the replenishment toner has been consumed, the toner empty display means is activated. The toner empty expression control means includes:
It operates for a fixed time when the temperature based on the temperature sensor shifts from the high temperature side to the low temperature side, so that the toner empty display means is not operated even if the output value from the toner sensor has reached the first toner empty value. This is a means for limiting the toner control means. When the output value based on the toner sensor reaches a value at which it is determined that all the replenishing toner has been consumed irrespective of the temperature based on the temperature sensor, the toner empty absolute display means restricts the toner empty display restriction means. Regardless, it is a means for operating the toner empty display means.

[Action]

In the toner density control device of the image forming apparatus according to the present invention, the toner sensor detects the toner density in the developing unit by a change in inductance, and outputs this as a change in voltage. Further, a temperature sensor detects a temperature near the developing unit.

Here, when the temperature based on the temperature sensor is on the high temperature side, when the output value from the toner sensor reaches the second toner control value at which toner replenishment is to be performed, the second toner control means operates the toner replenishment unit, and Is supplied with toner.
Further, when the output value from the toner sensor reaches the second toner empty value at which it is determined that all the replenishing toner has been consumed, the second toner control means activates the toner empty display means, and informs the operator of the developer in the developing section. To inform that the toner concentration has decreased and the supply toner has been completely consumed.

On the other hand, when the temperature based on the temperature sensor is on the low temperature side,
The output value from the toner sensor is the first to supply toner.
When the toner control value is reached, the first toner control unit activates the toner replenishing unit, and toner is replenished to the developing unit. Further, when the output value from the toner sensor reaches the first toner empty value at which it is determined that all the replenishing toner has been consumed, the first toner control means activates the toner empty display means to notify the operator of the developer in the developing section. To inform that the toner concentration has decreased and the supply toner has been completely consumed.

However, even when the temperature based on the temperature sensor is on the low temperature side, the toner empty expression restricting means sets the output value from the toner sensor to the first toner within a certain time when the temperature shifts from the high temperature side to the low temperature side. Even if the empty value has been reached, the toner empty display means will not be activated,
The first toner control means is restricted. This prevents the operator from being notified of the fact that the toner is not empty even though it is not.

Further, according to the present invention, when the output value based on the toner sensor decreases to the extent that it is determined that all the replenishment toner has been consumed regardless of the temperature based on the temperature sensor,
Regardless of the restriction by the toner empty expression restricting means, the toner empty absolute display means activates the toner empty displaying means. That is, even if the toner empty expression restricting means restricts the first toner control means so as not to operate the toner empty display means, if the toner density is extremely reduced, it is determined that the toner is empty. Will be surely informed. As a result, it is possible to reliably prevent the photosensitive drum from being damaged due to a remarkable decrease in image density and carrier pulling.

〔Example〕

FIG. 3 shows an example in which the present invention is applied to a copying machine.

In FIG. 3, a document table 12 is fixed on an upper surface of a copying machine main body 11, and a document holder 13 is mounted on the document table 12 so as to be openable and closable. Paper feed cassettes 14 and 15 are detachably mounted on the right side of the copying machine body 11 in the figure. On the left side of the copying machine body 11 in the figure, a paper discharge tray 18 for discharging the copied paper is mounted.

Inside the copying machine main body 11, an exposure device 19 for reading a document is provided on the upper side thereof. This exposure device
Reference numeral 19 includes a light source, a mirror, and the like. A photosensitive drum 20 on which an electrostatic latent image is formed is disposed in the center of the copying machine main body 11. Around the photosensitive drum 20,
A charging device 21 for charging the photosensitive drum 20 to a predetermined charge;
A developing device 22 for developing an electrostatic latent image, a transfer device 23 for transferring a toner image to a sheet, a sheet separating device 24 for separating a sheet from the photosensitive drum 20, and a residual toner on the photosensitive drum 20. A cleaning device 25 to be removed is provided. Between the paper feed cassettes 14 and 15 and the image forming unit constituted by the photosensitive drum 20 and the like, and downstream of the image forming unit, a paper feeder 27 and a paper discharge path 28 for transporting the paper, respectively. Is provided. Paper discharge transport path 28 and paper discharge tray
A fixing device 30 for fixing a transferred image on a conveyed sheet is arranged between the fixing device 30 and the fixing device 18.

As shown in FIG. 4, the developing device 22 includes a casing 31.
And a toner hopper 32 disposed above the casing 31. In the casing 31, a stirring roller 33 and a developing roller 34 are arranged. Further, a toner sensor 35 for detecting the toner density in the casing 31 is attached to an upper portion of the casing 31. The toner sensor 35 is a sensor that detects the toner concentration of the developer in the casing 31 by a change in inductance and outputs the result as a change in voltage. A toner for replenishment is stored in the toner hopper 32, and the toner is replenished into the lower casing 31 by rotating a toner replenishing roller 36 provided at a lower portion of the toner hopper 32. Has become. Further, a temperature sensor 37 is disposed adjacent to the photosensitive drum 20. The temperature sensor 37 is used for measuring the temperature change of the photosensitive drum 20 and also used for correcting the temperature of the toner sensor 35.

In addition, as shown in FIG.
It has. Other input units such as a toner sensor 35, a temperature sensor 37, and input keys are connected to the control unit 40.
Further, the control unit 40 includes a display unit 41 such as a lamp disposed on the upper end surface of the copying machine main body 11, a toner replenishing unit 42 including a motor for driving the toner replenishing roller 36, and the photosensitive drum 20. It is connected from a copy operation unit 43 composed of a motor and the like for driving. The control unit 40 includes a CPU, ROM, RA
M and the like, and controls the copying machine as described later.

Next, the operation of this embodiment will be described according to the control flow shown in FIGS. 6A to 6C.

When the main switch (not shown) is turned on, first step
In S1, initial settings such as setting the copy paper supply side to the paper feed cassette 14 are performed. Then, in step S2, a key input by the operator is waited.

If there is a key input, the process proceeds to step S3. Steps
In S3, it is determined whether the input key is a copy key. If the input key is not the copy key, the process proceeds to step S4, and performs another process according to the input key.

If it is determined in step S3 that the input key is a copy key, the process proceeds to step S5 in FIG. 6B. In step S5,
The copy operation unit 43 starts the copy operation. Next, in step S6, based on the input from the temperature sensor 37, it is determined whether or not the atmosphere near the photosensitive drum 20 is, for example, lower than 10 ° C. (low temperature). If it is 10 ° C. or higher, the process proceeds to step S7. In step S7, based on the input from the temperature sensor 37, it is determined whether or not the atmosphere near the photosensitive drum 20 is, for example, 30 ° C. or higher (high temperature). If it is 30 ° C. or higher, the process proceeds to step S8.

In step S8, it is determined based on the input from the toner sensor 35 whether or not the developing device 22 should be replenished with toner. That is, the output from the toner sensor 35 is V _{CH in} FIG.
(The toner replenishment level in the high temperature area) is determined. If V _CH has not been reached, casing 3
Since there is enough toner in 1, the processing in FIG.
The process moves to step S23 in FIG. In step S8, if the output of the toner sensor 35 has reached V _CH, the process proceeds to step S9. In step S9, the toner is replenished from the toner hopper 32 to the casing 31 by driving the toner replenishing unit 42 for a certain period. Next, in step S10, it is determined whether or not the toner is empty. That is, it is determined whether or not the output from the toner sensor 35 has reached V _EH (toner empty level in a high temperature region) in FIG. If V _EH has not been reached, it is not yet considered that the toner in the toner hopper 32 has run out, so the flow shifts to step S23 in FIG. 6C. If the output of the toner sensor 35 has reached _VEH in step S10, the process proceeds to step S21 in FIG. 6C.

Next, if it is determined in step S7 that the atmosphere in the vicinity of the photosensitive drum 20, that is, in the vicinity of the developing device 22, is lower than 30 ° C., the process proceeds to step S11. In step S11, it is determined whether or not the atmosphere near the developing device 22 has just transitioned from the high temperature region to the medium temperature region. If it has shifted from the high temperature region to the medium temperature region, the process proceeds to step S12, and the timer is reset and started. This timer ignores the detection of toner empty and does not display the toner empty during a certain period t immediately after the transition from the high temperature region to the middle temperature region and a certain period t immediately after the transition from the middle temperature region to the low temperature region. It is for control. If it is determined in step S11 that the atmosphere in the vicinity of the developing device 22 has not just shifted from the high-temperature region to the medium-temperature region, the process proceeds to step S13 without performing the process of step S12.

In step S13, it is determined based on the input from the toner sensor 35 whether or not the developing device 22 should be replenished with toner. That is, the output from the toner sensor 35 is V
It is determined whether or not _CM (toner supply level in the medium temperature area) has been reached. If not reached V _CM, the casing 31 because the toner is sufficiently, the process proceeds to step S23 in FIG. 6C finishing the step Figure 6B. In step S13, if the output of the toner sensor 35 has reached V _CM, the process proceeds to step S14. In step S14, the toner replenishing unit 42 is driven to replenish toner from the toner hopper 32 to the casing 31. Next, step S15
, It is determined whether or not the toner is empty.
That is, the output from the toner sensor 35, determines whether the reached (toner empty level in the intermediate temperature region) V _EM of FIG. 2. If not reached V _EM, since not yet considered to have disappeared toner hopper 32, control proceeds to step 23 of FIG. 6C. Steps
In S16, if the output of the toner sensor 35 has reached V _EM, the process proceeds to step S21 in FIG. 6C.

Next, in step S6, the atmosphere near the photosensitive drum 20 is changed.
If it is lower than 10 ° C., the process proceeds to step S16.
In step S16, it is determined whether or not the atmosphere near the developing device 22 has just transitioned from the medium temperature range to the low temperature range. If it has shifted from the medium temperature range to the low temperature range, step S17
Then, the timer is reset and started.
If it is determined in step S16 that the atmosphere near the developing device 22 has not just shifted from the middle temperature range to the low temperature range, the process in step S17 is not performed, and the process directly shifts to step S18.

In step S18, it is determined based on the input from the toner sensor 35 whether or not the toner of the developing device 22 should be replenished. That is, the output from the toner sensor 35 is V
It is determined whether or not _CL (toner supply level in a low-temperature region) has been reached. If the _VCL has not been reached, there is sufficient toner in the casing 31, so that the processing in FIG. 6B is completed and the routine goes to step 23 in FIG. 6C. If it is determined in step S18 that the output of the toner sensor 35 has reached _VCL , the process proceeds to step S19. In step S19, the toner is replenished from the toner hopper 32 to the casing 31 by driving the toner replenishing unit. Next, step S20
, It is determined whether or not the toner is empty.
That is, the output from the toner sensor 35, determines whether the reached (toner empty level in the low temperature region) V _EL of Figure 2. If not reached V _EL, because not yet considered to have disappeared toner hopper 32, the process proceeds to step S23 in FIG. 6C. In step S20, if the output of the toner sensor 35 has reached the V _EL, the process proceeds to step S21 in FIG. 6C.

In step S21 of FIG. 6C, it is determined whether or not the timer that has been reset and started in step S12 or S17 is being started. If the timer has timed out and stopped starting, the determination here is No. That is, when a certain period of time t has elapsed from the transition from the higher temperature region to the lower temperature region, the process proceeds to step S22.
In step S22, the display section 41 is caused to display the toner empty. Thus, the operator knows that the toner in the toner hopper 32 of the developing device 22 has run out. On the other hand, while the timer is running, the determination in step S21 is Yes, and the process proceeds to step S24.

In step S24, it is determined whether or not the output from the toner sensor 35 has reached _VEA in FIG. Where V _EA
Is an output value at which it is determined that all the replenishing toner has been consumed irrespective of the temperature based on the temperature sensor 37. In addition,
In the case of this embodiment, V _EA is generally set to the same value as V _EH . In step S24, if the output from the toner sensor 35 does not reach the V _EA is considered not yet led to up to damage of the photosensitive drum due to significant reduction and carrier pull of the image density occurs So
The process proceeds to step S23 without displaying the toner empty.

If the output from the toner sensor 35 has reached V _EA in step S24, there is a possibility that the photoconductor drum may be damaged due to a remarkable decrease in image density or carrier pulling, so the process proceeds to step S22. After the toner empty display is performed again, the process proceeds to step S23. in this way,
Even when the timer is running, if there is a possibility that the photosensitive drum may be damaged due to a significant decrease in image density or carrier pull, etc., the toner empty display is performed.
The operator is reliably notified that the toner is empty. As a result, it is possible to reliably prevent the photosensitive drum from being damaged due to a remarkable decrease in image density and carrier pulling.

In step S23, it is determined whether the copy operation has ended. Upon completion of the copy operation, the process returns from the step S23 to the step S2 in FIG. 6A.

If the copy operation has not been completed, step S6 in FIG. 6B
And the toner density control is repeated thereafter.

In the above-described embodiment, the temperature control is performed in three stages, but the present invention is not limited thereto, and the present invention can be similarly implemented in two or four or more stages. Further, in the above-described embodiment, in the case of toner empty, the display is merely displayed to that effect. However, the present invention is not limited to this, and in the case of toner empty, a configuration in which the operation of the copying machine is stopped may be adopted. it can.

〔The invention's effect〕

According to the toner concentration control device of the present invention, when the output value based on the toner sensor decreases to such an extent that it is determined that all the replenishing toner has been consumed regardless of the temperature based on the temperature sensor, the toner empty expression restriction Regardless of the restriction by the means, the toner empty absolute display means activates the toner empty display means. Therefore, according to the present invention, even if the detection of the toner empty level is ignored for a certain period of time and the toner empty display is controlled so as not to be turned on, the photosensitive drum due to a remarkable decrease in image density and carrier pulling etc. Can reliably be prevented from being damaged.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of the present invention, FIG. 2 is a graph showing the relationship between the temperature and the output of a toner sensor, FIG. 3 is a schematic longitudinal sectional view showing an example of a copying machine adopting the present invention, FIG. 4 is a schematic longitudinal sectional view of the developing unit, FIG. 5 is a block diagram of the control unit, and FIGS. 6A to 6C are control flowcharts. 20 photoconductor drum, 22 developing device, 32 toner hopper,
35: toner sensor, 37: temperature sensor, 41: display unit.

Claims (1)

(57) [Claims] An image forming apparatus comprising: a photoconductor on which a latent image is formed; and a developing unit for developing the photoconductor with toner, wherein a toner density of a developer in the developing unit is provided. A toner sensor that detects a change in inductance and outputs the change as a voltage; a temperature sensor installed near the developing unit to detect a temperature; a toner replenishing unit for replenishing toner to the developing unit; A toner empty display unit for notifying that the toner concentration of the developer has decreased and the replenishment toner has been completely consumed; and an output value from the toner sensor is effective when the temperature based on the temperature sensor is on the low temperature side. When the toner reaches the first toner control value at which toner replenishment is to be performed, the toner replenishment unit is operated, and the output value is determined to be that all the replenishment toner has been consumed. A first toner control unit that activates the toner empty display unit when the first toner empty value is reached, and is effective when the temperature based on the temperature sensor is on the high temperature side, and the output value from the toner sensor performs toner supply. When the output value reaches a second toner control value to be operated, the toner supply section is operated, and when the output value reaches a second toner empty value at which it is determined that all the toner for replenishment has been consumed, the toner empty display means is operated. A toner control unit that operates for a predetermined time when a temperature based on the temperature sensor shifts from a high temperature side to a low temperature side, and displays the toner empty even if the output value from the toner sensor has reached a first toner empty value. A toner empty display restricting means for restricting the first toner control means so as not to operate the toner means; If the output value based on the sensor reaches an absolute empty value at which it is determined that all the replenishing toner has been consumed irrespective of the temperature based on the temperature sensor, the toner empty display is performed regardless of the restriction by the toner empty display restricting means. And a toner empty absolute display means for operating the means.