JPH02127675A - Toner concentration controller for image forming device - Google Patents

Abstract

PURPOSE:To surely prevent a photosensitive drum from being damaged by allowing a toner exhaustion absolute display means to operate a toner exhaustion display means in spite of limits by a toner exhaustion message control means in the case an output value lowers. CONSTITUTION:A toner sensor detects the concentration of toner in a developing part owing to a change in inductance, and outputs the concentration as a change in a voltage. A temperature sensor detects temperature near the developing part. When a value outputted from the toner sensor lowers to the extent which such judgement is made that the entire toner for replenishment is consumed regardless of the temperature detected by the temperature sensor, the toner exhaustion absolute display means operates the toner exhaustion display means in spite of limits by a toner exhaustion message limiting means. Consequently, the photosensitive drum can be surely prevented from being damaged by a considerable decrease in picture density, carrier attraction, etc.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a toner density control device for an image forming apparatus, and in particular, to a toner density control device for an image forming apparatus, and particularly to a photoconductor on which a latent image is formed, and a developing section that develops the photoconductor with toner. The present invention relates to a toner density control device for an image forming apparatus.

[Conventional technology]

Conventional image forming apparatuses, such as copying machines, equipped with a photoreceptor on which a latent image is formed and a developing section that develops the latent image on the photoreceptor with toner, generally use a two-component developer consisting of toner and carrier. used.

The developing section has a toner density control device.

The toner concentration control device includes a toner replenishment section for replenishing toner to the developing section, a toner sensor for detecting the toner concentration in the developing section, a temperature sensor installed near the photoreceptor for detecting the temperature, and Some devices are known that are equipped with a toner empty display to notify that the toner is empty. As the toner sensor, a sensor is used that detects the toner concentration in the developing section by a change in inductance and outputs this as a change in voltage. This toner sensor has a property that the lower the toner concentration, the higher the output value.

In this toner concentration control device, when the output value from the toner sensor reaches a value that requires toner replenishment, the toner replenishment unit is activated, and when the output value reaches a value at which it is determined that all the toner for replenishment has been consumed, the toner replenishment unit is activated. Display empty display.
As a result, when there is a shortage of toner in the developing section, the toner is replenished, and when the toner for replenishment also runs out, a warning is issued to that effect. In this case, due to the nature of the toner sensor used, as the temperature rises, the output inductance from the toner sensor increases as shown by the broken line in FIG. Therefore, the temperature gradient is divided into, for example, a low temperature region, a medium temperature region, and a high temperature region according to the change in the output inductance of the toner sensor, and the control level is set in three stages to perform appropriate control for each temperature region. In addition, in FIG. 2, V and L are the toner replenishment level in the low temperature region, and ■
, is the toner empty level in the low temperature region, VCM
is the toner replenishment level in the medium temperature region, ①o8 is the toner empty level in the medium temperature region, van is the toner replenishment level in the high temperature region, and ①E)I is the toner empty level in the high temperature region.

By the way, in the toner concentration control device, for example, when the temperature is within the high temperature range, the output value of the toner sensor is ■. 2 (for example, point A in FIG. 2). If the temperature drops from this state and enters the medium temperature range (for example, point B in Figure 2), the output value of the toner sensor will be V even if there is no change in the toner concentration in the developing device.
V+< is exceeded, and the toner empty display lights up even though toner can be replenished by toner replenishment operation.

Therefore, in such a toner concentration control device, the detection of the toner empty level is ignored and the toner empty level is ignored for a certain period immediately after the transition from the high temperature area to the medium temperature area and for a certain period immediately after the transition from the medium temperature area to the low temperature area. The display is controlled so that it does not light up. On the other hand, since the toner replenishment operation is performed even within the certain period, the output value of the toner sensor will eventually become lower than the toner empty level, and the toner empty display will not light up after the certain period has elapsed. Note that the calculation of the fixed period is performed using a timer that is reset and started at the time of transition from the high temperature region to the medium temperature region or the time of transition from the medium temperature region to the low temperature region.

[Problems to be Solved by the Invention] In the conventional toner concentration control device, the temperature shifts to the high temperature region again and then shifts to the low temperature region before the timer finishes measuring for a certain period of time. If this happens, the timer will be reset and started again. Therefore, with this configuration, if the temperature slightly changes many times between the high temperature side area and the low temperature side area, or when the temperature is exactly in the middle between the high temperature side area and the low temperature side area, a so-called chattering state may occur. In such a case, the timer will be reset and started repeatedly, and the toner empty display will not be displayed forever. That is, in the conventional toner density control device, even if the toner is actually in an empty state, there are cases in which the toner empty state is not displayed. At this time, the image density is significantly lowered without displaying the toner empty message, and in some cases, carriers may be drawn and damage the photoreceptor drum.

An object of the present invention is that even if the toner empty level detection is ignored for a certain period of time and the toner empty display is controlled not to light up, the toner empty state actually occurs and the image density decreases significantly. It is an object of the present invention to provide a toner density control device that can reliably prevent a photosensitive drum from being damaged due to storage, carrier pulling, etc.

[Means to solve the problem]

A toner density control device for an image forming apparatus according to the present invention includes:
This is a toner density control device for an image forming apparatus that includes a photoreceptor on which a latent image is formed and a developing section that develops the photoreceptor with toner. As shown in FIG. 1, this toner concentration control device includes a toner sensor, a temperature sensor, a toner replenishment section, a toner empty display means, a first toner control means, a second toner control means, and a toner empty display means. The toner empty display device includes display limiting means and toner empty absolute display means.

The toner sensor is a sensor that detects the toner concentration of the developer in the developing section by a change in inductance and outputs it as a change in voltage. The temperature sensor is a sensor installed near the developing section to detect temperature. The toner replenishing section is a replenishing section for replenishing toner to the developing section. The toner empty display means is for informing that the toner concentration in the developing section has decreased and all the replenishment toner has been consumed.

The first toner control means is based on a temperature sensor (is enabled when the temperature is on the low temperature side, and operates the toner replenishing section when the output value from the toner sensor reaches a first toner control value at which toner replenishment should be performed). and when the output value reaches a first toner empty value at which it is determined that all the replenishing toner has been consumed, the toner empty display means is actuated.

The second toner control means is enabled when the temperature based on the temperature sensor is on the high temperature side, and operates the toner replenishment section when the output value from the toner sensor reaches a second toner control value at which toner replenishment should be performed; When the output value reaches a second toner empty value at which it is determined that all the replenishing toner has been consumed, the toner empty display means is actuated. The toner empty expression limiting means operates for a certain period of time based on a temperature sensor (when the temperature shifts from a high temperature side to a low temperature side, and even if the output value from the toner sensor reaches the first toner empty value) The toner empty absolute display means is a means for restricting the first toner control means so as not to operate the empty display means. This means operates the toner empty display means regardless of the restriction by the toner empty display restriction means when the toner empty display reaches a value determined to have been reached.

[Effect]

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

Here, when the temperature based on the temperature sensor is on the high temperature side,
The output value from the toner sensor indicates the second point at which toner replenishment should be performed.
When the toner control value is reached, the second toner control means operates the toner replenishing section, and the developing section is replenished with toner. Further, when the output value from the toner sensor reaches a second toner empty value at which it is determined that all of the replenishing toner has been consumed, the second toner control means operates the toner empty display means to notify the operator that the developer in the developing section The toner concentration has decreased and the replenishment toner has been completely consumed.

On the other hand, when the temperature based on the temperature sensor is on the low-temperature side, when the output value from the toner sensor reaches the first toner control value at which toner replenishment should be performed, the first toner control means operates the toner replenishment section and supplies the toner to the developing section. Toner is replenished. Also,
When the output value from the toner sensor reaches the first toner empty value at which it is determined that all the replenishment toner has been consumed,
The first toner control means activates the toner empty display means to inform the operator that the toner concentration of the developer in the developing section has decreased and all of the replenishment toner has been consumed.

However, even if the temperature based on the temperature sensor is on the low temperature side, within a certain period of time when the temperature changes from the high temperature side to the low temperature side, the toner empty expression limiting means causes the output value from the toner sensor to change to the first toner. The first toner control means is restricted so as not to operate the toner empty display means even if the empty value has been reached. This prevents the operator from being informed that the toner is empty even though the toner is not empty.

Furthermore, in this invention, based on the toner sensor (the output value is
Regardless of the temperature based on the temperature sensor, when the replenishment toner has decreased to such a level that it is determined that all of it has been consumed, the toner empty absolute display means operates the toner empty display means, regardless of the restriction by the toner empty expression restriction means. let

In other words, even if the toner empty expression limiting means restricts the first toner control means so as not to operate the toner empty display means, if the toner concentration is extremely reduced, the operator will be able to tell that the toner is empty. be sure to be informed.

This makes it possible to reliably prevent a significant decrease in image density and damage to the photosensitive drum due to carrier pull.

〔Example〕

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

In FIG. 3, a document table 12 is provided on the top surface of the copying machine main body 11.
is fixed, and a document holder 1 is mounted on the top of the document table 12.
3 is attached so that it can be opened and closed freely.

Paper feed cassettes 14 and 15 are removably attached to the rejuvenation side of the copying machine main body 11. On the prisoner side of the copying machine main body 11, a paper discharge tray 18 from which copies of paper are discharged is installed.

Inside the copying machine main body 11, an exposure device 19 for reading a document is provided on the upper side. This exposure device 19 is composed of a light source, a mirror, and the like. Also,
A photosensitive drum 20 on which an electrostatic latent image is formed is arranged in the center of the copying machine main body 11. Around the photoreceptor drum 20, there are a charging device 21 that charges the photoreceptor drum 20 to a predetermined charge, a developing device 22 that develops an electrostatic latent image, a transfer device 23 that transfers the toner image onto paper, and a photoreceptor. A paper separation device 24 for separating paper from the drum 20 and a cleaning device 25 for removing residual toner on the photosensitive drum 20 are arranged. paper feed cassette 14',
15 and an image forming section constituted by the photoreceptor drum 20 and the like, and on the downstream side of the image forming section, respectively.
A paper feed conveyance path 27 and a paper discharge conveyance path 28 for conveying paper are provided. A fixing device 30 is arranged between the paper discharge conveyance path 28 and the paper discharge tray 18 to fix the transferred image on the conveyed paper.

As shown in FIG. 4, the developing device 22 includes a casing 31
and a toner hopper 3 disposed at the top of the casing 31.
An agitating roller 33 and a developing roller 34 are disposed within the casing 31 having a casing 2. Further, a toner sensor 35 for detecting the toner concentration within the casing 31 is attached to the upper part of the casing 31. This toner sensor 35 detects the toner concentration of the developer in the casing 31 by a change in inductance,
This is a sensor that outputs voltage changes.

Toner for replenishment is stored in the toner hopper 32, and as a toner replenishment roller 36 provided at the bottom of the toner hopper 32 rotates, toner is replenished into the gauging 31 below. It has become. Further, a temperature sensor 3 is provided adjacent to the photoreceptor drum 20.
7 is placed. This temperature sensor 37 is used to measure the temperature change of the photosensitive drum 20 and is also used to correct the temperature of the toner sensor 35.

Further, as shown in FIG. 5, this copying machine has a control section 40.
It is equipped with The control unit 40 is connected to a toner sensor 35, a temperature sensor 37, and other input units such as input keys. Furthermore, the control section 40 includes a display section 41 consisting of a lamp etc. disposed on the upper end surface of the copying machine main body 11, and a toner replenishment section 4 consisting of a motor etc. that drives the toner replenishment roller 36.
2, and a copy operation unit 43 including a motor for driving the photoreceptor drum 20 and the like. This control section 40 is composed of a CPU, ROM, RAM, etc., and controls the copying machine as will be described later.

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

When a main switch (not shown) is turned on, first, in step 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 awaited.

If there is key human power, the process moves to step S3.

In step S3, it is determined whether the input key is a copy key. If the input key is not a copy key, step S4
, and performs other processing depending on the input key.

In step S3, if the input key is a copy key, the process moves to step S5 in FIG. 6B.

In step S5, the copy operation unit 43 is caused to start a copy operation. Next, in step S6, based on the input from the temperature sensor 37, it is determined whether the atmosphere near the photosensitive drum 20 is, for example, less than 10° C. (low temperature). If the temperature is 10°C or higher, the process moves to step S7. In step S7, based on the input from the temperature sensor 37, the atmosphere near the photosensitive drum 20 is, for example, 30°C.
Determine whether the temperature is higher than that (high temperature). If it is 301C or more, the process moves 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, it is determined whether the output from the toner sensor 35 has reached the VCM (toner replenishment level in a high temperature region) shown in FIG. If VCH has not been reached,
Since there is enough toner in the casing 31, the process in FIG. 6B is completed and the process moves to step S23 in FIG. 6C. In step S8, the output of the toner sensor 35 is set to VCI.
If it has reached I, the process moves to step S9.

In step S9, by driving the toner replenishing section 42 for a certain period of time, the casing 31 is removed from the toner hopper 32.
Refill toner. Next, in step S10,
Determine whether or not the toner is empty. That is, it is determined whether the output from the toner sensor 35 has reached the VEH (toner empty level in a high temperature region) shown in FIG.

(2) If the time has not reached 18 and has not reached 7, it is not considered that the toner in the toner hopper 32 has run out, so the process moves to step S23 in FIG. 6C. In step SIO, if the output of the toner sensor 35 has reached vo, the process moves to step S21 in FIG. 6C.

Next, if it is determined in step S7 that the atmosphere near the photosensitive drum 20, that is, near the developing device 22, is less than 30°C, the process moves to step S11.

In step 311, it is determined whether the atmosphere near the developing device 22 has transitioned from a high temperature region to a medium temperature region.

If the temperature has shifted from the high temperature range to the medium temperature range, the process moves to step S12, where the timer is reset and started. This timer ignores the detection of toner empty and prevents the toner empty display from occurring during a certain period immediately after the transition from the high temperature area to the medium temperature area and during a certain period t immediately after the transition from the medium temperature area to the low temperature area. It is for control. In step S311, if the atmosphere near the developing device 22 has not transitioned from a high temperature range to a medium temperature range, the process directly proceeds to step S13 without performing the process of step S12.

In step 313, based on the input from the toner sensor 35, it is determined whether the developing device 22 should be replenished with toner. That is, the output from the toner sensor 35 is
It is determined whether v, 8 (toner replenishment level in the medium temperature range) in the figure has been reached. If VCH has not been reached, there is enough toner in the casing 31, so the 6th B
After completing the process shown in the figure, the process moves to step 323 in FIG. 6C.

In step S13, the output of the toner sensor 35 is set to V
If the CH has been reached, the process moves to step S14. In step 314, toner is replenished from the toner hopper 32 into the casing 31 by driving the toner replenishing section 42. Next, in step S15),
Determine whether or not the toner is empty. That is, it is determined whether the output from the toner sensor 35 has reached the toner empty level (in the VtnC medium temperature range shown in FIG. 2). (2) If 1.4 has not been reached, it is not considered that the toner in the toner hopper 32 has run out, so the process directly proceeds to step 23 in FIG. 6C.

In step 516, the output of the toner sensor 35 is
2, 4, step S2 in FIG. 6C
Move to 1.

Next, if it is determined in step S6 that the atmosphere near the photosensitive drum 20 is less than 10° C., the process moves to step S316. In step S16, it is determined whether the atmosphere near the developing device 22 has transitioned from a medium temperature range to a low temperature range. If the temperature has moved from the medium temperature region to the low temperature region,
Proceeding to step S17, the timer is reset and started. In step 316, the developing device 22
If the nearby atmosphere has not transitioned from the medium temperature range to the low temperature range, the processing in step S17 is not performed and the process directly proceeds to step S18.

In step 318, 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
It is determined whether the VCL (toner replenishment level in a low temperature region) shown in the figure has been reached. If V, . . . has not been reached, there is enough toner in the casing 31, so
After completing the process in Figure B, the process moves to step 23 in Figure 6C.

In step 318, the output of the toner sensor 35 is
If it has reached , the process moves to step S19.

In step 319, the toner replenishing section 42 is driven to replenish toner from the toner hopper 32 into the casing 31. Next, in step S20, it is determined whether the toner is empty. That is, it is determined whether the output from the toner sensor 35 has reached VEL (toner empty level in a low temperature region) shown in FIG.

■. If this has not been reached, it is still not considered that the toner in the toner hopper 32 has run out, so the process moves to step 323 in FIG. 6C. In step S20, if the output of the toner sensor 35 has reached VEL,
The process moves to step S21 in FIG. 6C.

In step S21 of FIG. 6C, it is determined whether the timer that was reset and started in step S12 or step 317 is running. If the timer times up and the activation is stopped, the determination here is No.

That is, if a certain period of time t has passed since the transition from the higher temperature region to the lower temperature region, step 322
to move to. In step S22, the display section 41 is caused to display toner empty. As a result, the operator knows that the toner in the toner hopper 32 of the developing bag W, 22 has run out. On the other hand, while the timer is running, the determination in step S21 is Yes, and the process moves to step S324.

In step S24, the output from the toner sensor 35 is
It is determined whether V□ in FIG. 2 has been reached. here,
■□ is an output value at which it is determined that all of the replenishment toner has been consumed regardless of the temperature based on the temperature sensor 37.

In addition, in the case of this embodiment, as an example, VIA is V
It is set to the same value as X and l. At step 324,
The output from the toner sensor 35 is ■. If the toner empty state has not been reached, it is considered that the image density has not significantly decreased or damage to the photoreceptor drum has occurred due to carrier pull, etc., so the process moves to step S23 without displaying the toner empty display. .

In step S24, the output from the toner sensor 35 is set to Vt.
If A has been reached, there is a possibility that the image density will significantly decrease or the photoreceptor drum will be damaged due to carrier pull, so the process moves to step S22, displays the toner empty display again, and then moves to step S23. Transition. In this way, even if the timer is running, if there is a possibility that the image density is significantly reduced or the photoconductor drum is damaged due to carrier pulling, etc., the toner empty display will be displayed, so the toner empty state will be displayed. The operator is reliably informed that this is the case. This makes it possible to reliably prevent a significant decrease in image density and damage to the photosensitive drum due to carrier pull.

In step S23, it is determined whether the copy operation is finished. When the copying operation is completed, the process returns from step S23 to step S2 in FIG. 6A.

If the copy operation is not completed, step S in FIG. 6B
6 and repeat the toner density control.

In the above embodiment, the temperature control was performed in three stages, but the invention is not limited thereto, and the present invention can be implemented in the same manner even in the case of two stages, four stages or more. Further, in the above embodiment, when the toner is empty, a message to that effect is simply displayed, but the present invention is not limited to this.
It is also possible to adopt a configuration that stops the operation of the copying machine when the toner is empty.

〔Effect of the invention〕

According to the toner concentration control device 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 is consumed regardless of the temperature based on the temperature sensor, the toner empty expression restriction is applied. The toner empty absolute indicating means operates the toner empty indicating means regardless of the limitations imposed by the 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 not to light up, the image density may be significantly reduced and the photoconductor drum may be damaged due to carrier pull, etc. damage can be reliably prevented.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of the present invention, FIG. 2 is a graph showing the relationship between temperature and the output of a toner sensor, and FIG. 3 is a schematic vertical cross-sectional view showing an example of a copying machine adopting the present invention. FIG. 4 is a schematic longitudinal sectional view of the developing device, FIG. 5 is a block diagram of its control section, and FIGS. 68 to 6C are its control flowcharts. 20... Photosensitive drum, 22... Developing device, 32...
... Toner hopper, 35 ... Toner sensor, 37...
・Temperature sensor, 4 parts...display part.

Claims (1)

[Scope of Claims] A toner concentration control device for an image forming apparatus, comprising a photoconductor on which a latent image is formed, and a developing section that develops the photoconductor with toner, the toner concentration control device for an image forming apparatus comprising: a photoconductor on which a latent image is formed; a toner sensor that detects density by a change in inductance and outputs it as a change in voltage; a temperature sensor that is installed near the developing section and detects temperature; a toner replenishment section that supplies toner to the developing section; and the developing section. a toner empty display means for notifying that the toner concentration of the developer in the unit has decreased and all the replenishment toner has been consumed; When the value reaches a first toner control value at which toner replenishment should be performed, the toner replenishing section is activated, and 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 is displayed. a first toner control means for operating the toner control means; the toner control means is activated when the temperature based on the temperature sensor is on the high temperature side; and when the output value from the toner sensor reaches a second toner control value at which toner replenishment is to be performed, the toner replenishment is performed. a second toner control means for activating the toner empty display means when the output value reaches a second toner empty value at which it is determined that all the replenishing toner has been consumed; The first toner control means operates for a certain period of time when the temperature changes from the high temperature side to the low temperature side, and the first toner control means is configured to not operate the toner empty display means even if the output value from the toner sensor reaches a first toner empty value. and a toner empty display limiting means for limiting the toner empty display when the output value based on the toner sensor reaches an absolute empty value at which it is determined that all the replenishment toner is consumed regardless of the temperature based on the temperature sensor. A toner density control device for an image forming apparatus, comprising: toner empty absolute display means for operating the toner empty display means regardless of the restriction by the display restriction means.