JP2003114549A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem that a situation is erroneously judged as a situation that toner density is considerably low when a photoreceptor is deteriorated because of the filming of wax or the like. SOLUTION: This image forming device is equipped with a means for storing the adjusted value (1) of first emitted light quantity by an image density detection means 15 to a new image carrier out of the adjusted values of the emitted light quantity by the detection means 15 obtained by calibration, performs the second and succeeding calibration, and stops the calibration when the adjusted value of the emitted light quantity by the detection means 15 exceeds the adjusted value of the first emitted light quantity by a specified value αor more, and then the adjusted value of the emitted light quantity by the detection means 15 is fixed to ((1)+α) so as to operate the detection means 15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a facsimile and a printer.

[0002]

2. Description of the Related Art In an image forming apparatus, the maximum factor that affects the image density (the density of the formed image) is the toner density in the developer in the developing unit. Therefore, in order to maintain a stable image density, the toner density It is desirable to keep constant. However, the toner concentration is greatly affected by changes in the physical properties of the developer itself over time, changes in the physical properties due to environmental conditions such as temperature and humidity, and development conditions.

Therefore, normally in an image forming apparatus,
A reference image (P pattern) for image density detection is formed on the photoconductor by a developing potential which is a difference between a surface potential of the photoconductor as a predetermined image carrier and a voltage applied to the developing device (developing bias). A toner density control method is generally used in which the density of this P pattern is detected by a P sensor as an image density detecting means and the toner replenishment from the toner replenishing device to the developing device is controlled according to the detection result. .

That is, in this toner density control system, P
Of the output values of the sensor, if the output value of the P sensor for the P pattern on the photoconductor is Vsp and the output value of the P sensor for the non-image area (background portion) on the photoconductor is Vsg, then Vsp / Vsg is normally The toner replenishment from the toner replenishing device to the developing device is controlled so as to be constant. Specifically, the correction value ΔVt of the toner replenishment amount is determined based on the value of Vsp / Vsg or the value of Vsp using a table as shown in FIG.

The operation of the P sensor in the non-image area (background portion) of the photoconductor is calibrated (calibration operation) so that the output value Vsg of the P sensor becomes a predetermined value, for example, 4.0 (V). Execute to adjust the amount of light emitted from the P sensor,
After that, a P pattern is formed on the photoconductor and the output value Vsp of the P sensor for the P pattern is obtained.

When the amount of toner adhering to the P pattern on the photosensitive member is reduced, the amount of reflected light at the P pattern portion on the photosensitive member is increased to increase Vsp / Vsg, and the toner concentration of the developer in the developing unit is low. When the toner replenishing device determines that the toner is replenished to the developing device, the toner concentration is kept constant. On the contrary, when Vsp / Vsg is low, it is determined that the toner concentration of the developer in the developing device is high, and the toner is not supplied from the toner replenishing device to the developing device. For reference, the relationship between the P pattern toner adhesion amount M / A per unit area on the photoconductor and the P sensor output value Vsp for the P pattern is generally as shown in FIG.

In addition to the method of controlling the toner replenishment based only on the output value of the P sensor, the output value of the T sensor as the toner concentration detecting means for detecting the toner concentration of the developer in the developing device and the P sensor. A method is also known in which toner output control (toner density control) is performed using output values together.

In the toner concentration control system using both the P sensor and the T sensor, the P pattern is formed on the photoconductor when the power switch of the machine body is turned on or every time a predetermined number of images are formed.
Vsp / Vsg is read, and the correction amount ΔVt of the toner concentration control reference value Vtref of the T sensor is read based on the output value.
To calculate. Then, the toner concentration control reference value Vtref is corrected by the correction amount ΔVt to obtain the new toner concentration control reference value Vtr.
ef '(= Vtref + ΔVt) is determined and set as a new T sensor toner density control reference value (Japanese Patent Laid-Open No. 8-110).
See Japanese Patent Publication No. 700).

From the difference between the corrected T-sensor toner density control reference value Vtref 'and the T-sensor output value Vt output during each image forming operation or at a certain timing, the toner replenishing amount from the toner replenishing device to the developing device is calculated. To decide. This toner replenishment amount can be replaced with the rotation time of the toner bottle (toner replenishment clutch ON time) if the toner replenishing device is of a type that replenishes toner by rotating the toner bottle, for example. The larger the value of (Vt-Vtref) is, the more the toner density is considered to be insufficient with respect to the target value, and therefore the control is generally performed to lengthen the toner bottle rotation time (toner supply clutch ON time).

Japanese Unexamined Patent Publication (Kokai) No. 5-134548 discloses an image forming apparatus that uses a T sensor and a P sensor together to control toner density, and detects the image density by the P sensor every time a certain number of images are formed. What is done is described. Japanese Patent Application Laid-Open No. 8-110700 discloses an image forming apparatus that uses a T sensor and a P sensor together to control toner density, and has upper and lower limits of a T sensor toner density control reference value correction amount based on an output value of the P sensor. Is set to control the toner density, thereby preventing the fluctuation of the toner density caused by the fluctuation of the charging potential or the like.

[0011]

In the image forming apparatus, the photosensitive member generally includes a charging roller, a transfer roller,
The developer, the developing entrance seal, the cleaning blade, the cleaning brush, etc. are in contact with each other, and the surface of the photoconductor gradually wears as the photoconductor rotates. Further, in the transfer step, various transfer papers come into contact with the photoconductor, so that various transfer paper additives such as calcium carbonate and silica may adhere to the photoconductor. Further, from the developing process to the transferring process to the photoconductor cleaning process, the toner adheres to the surface of the photoconductor, and the additive substances such as silica, titanium oxide and wax contained in the toner gradually adhere to the photoconductor.

The degree of adhesion of these foreign matters to the photosensitive member over time varies depending on the operating environment and operating conditions, and depending on the degree, the image quality is deteriorated. In particular, due to the diversification of transfer paper in the market these days, it is difficult to imagine the degree of deterioration of the surface of the photoconductor due to the type of transfer paper, and sometimes the degree of deterioration of the surface of the photoconductor exceeds expectations.

When the surface of the photoconductor is severely deteriorated, the P sensor is operated in the non-image area (background portion) on the photoconductor to perform the calibration so that the output value Vsg of the P sensor becomes a predetermined value. In addition, the light emission amount adjustment value of the P sensor (the PWM value of the pulse width modulation (PWM) signal for driving the light emitting element of the P sensor) obtained at that time becomes larger than the normally expected range. That is, by increasing the amount of light emitted from the P sensor to a considerable amount, it becomes possible to finally adjust Vsg to 4.0 (V). Fig. 4 shows a new photoconductor (OPC), a photoconductor obtained by performing a 30K run (image formation of 30 x 1000 sheets of transfer paper) in a 1to2 mode in which one original is copied onto two transfer papers. For each of the photoconductor that performed 60K run in mode and the photoconductor with wax filmed on the surface, the abscissa shows the P-sensor emission light intensity adjustment value (PWM
Value), and the vertical axis is the result of plotting the P sensor output value in the non-image area (background portion). From this, Vsg is 4.0 (V)
When adjusting to, the PWM value (256 gradation PWM value) is a new photoconductor (OPC), a photoconductor that has run 30K in 1to2 mode, a photoconductor that has run 60K in 1to2 mode, and a wax on the surface. 66, 80, for each of the photoreceptors filmed by
It is 100, 137, and the highest is the photoconductor with wax filming on the surface.

At this time, as shown in FIG. 5, the toner density of the developer is finely adjusted so that the image ID (image density) is approximately 1.25.
Despite being matched equally with the new photoreceptor, 1to2
The Vsp / Vsg of the photoconductor after 30K run in the mode and the photoconductor after 60K run in the 1to2 mode are 0.100 and 0.13, respectively.
Although it was 5, 0.170, Vsp / Vsg of the sensitizer filmed with wax was as large as 0.280, and it was mistakenly judged that the toner concentration was considerably low. As a result, the toner concentration of the developer is controlled to be considerably high,
There is a problem that toner is scattered on the image, toner is dropped, and the margin for the toner background image is reduced.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus capable of solving the above-mentioned problems at low cost and preventing excessive toner replenishment.

[0016]

In order to achieve the above object, the invention according to claim 1 is a developing means for supplying toner to a latent image formed on an image carrier to visualize the latent image. When,
On the image carrier, there are provided a toner replenishing device for replenishing the developing device with toner, and an image density detecting device for detecting an image density of a reference image for image density detection formed on the image carrier. Calibration is performed so that the output value of the image density detecting means for the non-image part becomes a predetermined value, and the amount of light emitted by the image density detecting means is adjusted, and the image with respect to at least the reference image on the image carrier is adjusted. In the image forming apparatus for controlling the toner replenishment from the toner replenishing means to the developing means based on the output value of the density detecting means, among the emission light amount adjustment values of the image density detecting means obtained by the calibration, A means for storing a first emission light amount adjustment value of the image density detecting means for the new image carrier, and performing the calibration after the second time, When the emission light amount adjustment value of the image density detecting means exceeds the emission light amount adjustment value of the first time by a predetermined value α or more, the calibration is stopped, and thereafter, the emission light amount adjustment value of the image density detecting means is (+ α). The image density detecting means is fixed to the above position.

According to a second aspect of the invention, in the image forming apparatus according to the first aspect, the calibration is executed and the emission light amount adjustment value of the image density detecting means is (+ α).
A warning is issued when the value exceeds.

According to a third aspect of the present invention, in the image forming apparatus according to the first aspect, the calibration is executed and the emission light amount adjustment value of the image density detecting means is (+ α).
If a warning is issued, the calibration is continued and the final emission light amount adjustment value of the image density detecting means is stored, and thereafter the emission light amount adjustment value of the image density detecting means is set to (+ α). The image density detecting means is fixedly operated.

According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect, when the numerical value of the emitted light amount adjustment value of the image density detecting means exceeds (+ α) is β, the degree of β is In some cases, the warning is not issued.

According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the second to fourth aspects, the warning is issued via the display section of the operation panel.

According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the second to fourth aspects, the warning is given by sound or voice.

According to a seventh aspect of the present invention, in the image forming apparatus according to any one of the first to sixth aspects, the toner replenishment control is performed by setting the emission light amount adjustment value of the image density detecting means to (+ α). It is performed based on only the output value of the image density detecting means with respect to the reference image for detecting the image density obtained by operating the image density detecting means after being fixed to.

According to an eighth aspect of the invention, in the image forming apparatus according to any one of the first to seventh aspects, there is provided a toner density detecting means for detecting a toner density of the developing means,
The toner density control reference value with respect to the output value of the toner density detecting means is corrected based on the output value of the image density detecting means, and the output value of the toner density detecting means is used according to the corrected toner density control reference value. It controls toner supply.

According to a ninth aspect of the present invention, in the image forming apparatus according to any one of the first to eighth aspects, among the emission light amount adjustment values of the image density detecting means obtained by the calibration, A means for storing the first light emission light amount adjustment value of the image density detecting means for the new image carrier to the nth light emission light amount adjustment value of the image density detecting means for the image carrier, is provided (n + 1) th time. When the emitted light amount adjustment value of the image density detection means obtained by the subsequent calibration exceeds the minimum value min of the first emitted light amount adjusted value to the nth emitted light amount adjusted value by a predetermined value α or more. The calibration is stopped, and thereafter, the emission light amount adjustment value of the image density detecting means is fixed to (min + α) and only the image density detecting means is operated.

According to a tenth aspect of the present invention, in the image forming apparatus according to any one of the first to ninth aspects, there is provided a means capable of arbitrarily changing the α.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION In the embodiment of the present invention, the above-mentioned problems can be solved at a low cost only by controlling by software, and the light emission amount adjustment value (PWM value) of the P sensor as the image density detecting means is set. The rising level of the P sensor is judged to be slight due to an error in the mounting position of the P sensor, or due to serious deterioration of the photoconductor as the image carrier. In the latter case, the light emission amount adjustment value (PWM value) of the P sensor is determined. It is intended to prevent the excessive toner replenishment by fixing the upper limit of the emission light amount adjustment (PWM value) of the P sensor without adopting the abnormal value of (4).

The first embodiment of the present invention will be described below. The first embodiment is a form of an electrophotographic copying machine which is an image forming apparatus. First, the schematic configuration of the copying machine according to the first embodiment will be described with reference to FIG. Around the drum-shaped photoconductor 1 serving as an image carrier, a charging roller 2 as a charging unit that is sequentially charged in the counterclockwise direction from a power source (not shown) to uniformly charge the surface of the photoconductor 1. An exposure unit (not shown) that irradiates the surface of the photoconductor 1 with the exposure light 3 to form an electrostatic latent image based on the image information of the document read by the image reading unit (not shown); A developing device 4 for visualizing the electrostatic latent image as a toner image, a transfer roller 5 as a transfer means for transferring the toner image on the photoconductor 1 onto a sheet P as a recording material,
A cleaning device 6 as a cleaning unit that removes the toner remaining on the photoconductor 1 after the transfer and a static eliminator such as a static elimination lamp (not shown) that initializes the surface potential of the photoconductor 1 after the transfer are provided.

The photosensitive member 1 is rotationally driven by a driving unit (not shown) and uniformly charged by a charging roller 2, and the exposure light 3 emits an exposure light 3 based on document image information from an image reading unit (not shown). It is irradiated and an electrostatic latent image is formed. The electrostatic latent image on the photoconductor 1 is visualized as a toner image by the developing device 4, and the toner image on the photoconductor 1 is transferred onto the sheet P by the transfer roller 5.
After the transfer, the cleaning device 6 removes residual toner from the photoconductor 1, and the surface potential of the photoconductor 1 is initialized by a charge eliminator (not shown).

The developing device 4 carries a developer and carries the photosensitive member 1.
Developing roller 7 as a developer bearing member for supplying toner to
And a developing device as developing means having conveying screws 8 and 9 as stirring and conveying means for stirring and conveying the developer, and the conveying screw 9 farther from the developing roller 7.
On the lower side, a T sensor (permeability sensor) 11 as a toner concentration detecting means for detecting the toner concentration of the two-component developer including the carrier and the negatively charged toner in the developing casing 10.
Is provided. Further, although not shown, a toner replenishing device as a toner replenishing means for replenishing the two-component developer in the developing casing 10 with toner is provided above the transport screen 9. A negative developing bias is applied to the developing roller 7 from a power source (not shown), and a predetermined developing potential is formed between the photoconductor 1 and the developing roller 7.

The sheets P stored in the sheet feeding cassette 12 are separated one by one from the uppermost one by a sheet feeding roller 13 and the like, and sent toward the registration roller pair 14. The sheet P is temporarily stopped by the registration roller pair 14, and after the skew displacement is corrected, it is sent to the transfer nip portion between the photoconductor 1 and the transfer roller 5 at a predetermined timing by the registration roller pair 14. In this transfer nip portion, a transfer bias is applied to the transfer roller 5 from a power source (not shown), and the toner image on the photoconductor 1 is transferred to the paper P. The sheet P to which the toner image is transferred is sent to a fixing device (not shown) located on the downstream side in the transport direction, and the toner image is fixed by the fixing device by heat and pressure.

Between the transfer roller 5 and the developing device 4, there is provided a P sensor (reflection type photo sensor) 15 as an image density detecting means having a light emitting element and a light receiving element. T
The output value Vt of the sensor 11 shows a lower value as the toner density TC in the developer is higher, and the output value Vsp of the P sensor 15 shows a lower value as the image density on the photoconductor 1 is higher.

FIG. 1 shows the control unit of the first embodiment. First
The overall operation of the copying machine of the embodiment is controlled by the control means 16. The control means 16 has an I / O interface 17, a CPU 18, a RAM 19, and a ROM 20. A main motor 23 and a toner replenishing clutch 24 are connected to the I / O interface 17 via drivers 21 and 22, respectively. An operation display unit (operation panel) 25 is connected to the I / O interface 17. The main motor 23 drives the photoconductor 1 to rotate.

Further, the I / O interface 17 includes
PWM controller 26 for supplying a predetermined voltage to T sensor 11 and P sensor 15, and T sensor 11 and P sensor
The A / D converters 27 and 28 that convert an analog signal output from the sensor 15 into a digital signal are connected. Note that resistors 29 to 3 are provided between the PWM controller 26 and the T sensor 11 and the P sensor 15, respectively.
1, 32-34, capacitors 35, 36, operational amplifier 3
A circuit composed of 7, 38 is connected.

Next, the toner replenishment control (toner density control) in the first embodiment will be described with reference to the flowcharts of FIGS. 7 and 8. First, the control means 16 stores the emission light amount adjustment value PWM1 of the P sensor 15 when the photoconductor 1 is new (step S100). The controller 16 turns on the main switch of the image forming apparatus (step S1).
01), calibration is started so that the output value of the P sensor 15 with respect to the non-image portion of the photoconductor 1 becomes a predetermined value, for example, 4.0 (V) (step S102), and the P sensor is passed through the PWM controller 26. The light emission amount of the P sensor 15 is adjusted by adjusting the PWM light amount of 15 with a PWM value of multiple gradations, for example, the PWM value of 256 gradations (by adjusting the PWM value of the PWM signal for driving the light emitting element of the P sensor 15, (Adjusted) The light emission amount adjustment value of the P sensor 15 (PWM value of 256 gradations: output value of the light receiving element of the P sensor 15) is detected from the A / D converter 28 (step S103). The emission light amount adjustment value of the P sensor 15 may be grasped by a voltage change or the like.

Next, the control means 16 checks whether the light emission amount adjustment value (PWM value) of the P sensor 15 exceeds (PWM1 + predetermined value α) (step S104). Control means 1
6 indicates that the light emission amount adjustment value (PWM value) of the P sensor 15 is (PWM
If it exceeds (1 + α), the calibration is stopped (step S105), and the final emission light amount adjustment value (PWM value) of the P sensor 15 is set to (PWM1 + α) (step S).
106).

Next, the control means 16 controls each part of this embodiment to form a reference image for image density detection on the photoconductor 1 (step S107), and the PWM controller 26.
The P sensor 15 is caused to emit light with the set light quantity of the PWM value (PWM1 + α) through
The output value (density) Vsp of the sensor 15 is taken in (step S108), and the P sensor 15 is caused to emit light at the set PWM value (PWM1 + α) via the PWM controller 26 to cause the non-existence on the photoconductor 1. P sensor 3 for the image part
The output value (density) Vsg of 0 is fetched (step S10
9).

Next, the control means 16 controls the V which has been taken in.
Vsp / Vsg is calculated from sp and Vsg (step S11)
0). The control means 16 takes in the output value Vt that differs depending on the toner concentration of the two-component developer in the developing casing 10 from the T sensor 11 almost at the same time (step S111).
Next, the control means 16 controls Vsp / Vsg and Vt (to be exact, Vt
ref-Vt), the correction amount Δ of the toner concentration control reference value Vtref of the T sensor 11 according to the correction table shown in FIG.
Vt is determined (step S112). Control means 16
When ΔVt is determined, a new control target value (new T sensor toner concentration control reference value) Vtref 'is set to Vtref' = V
Calculation is performed based on the expression of tref + ΔVt (step S11)
3). Here, the previous toner density control reference value Vtref is used.

The control means 16 controls the new control target value Vtre.
When f'is determined, this is set as the toner density control reference value and the copy operation is performed as described above (step S114). Next, the control means 16 determines the toner replenishment time τ of the toner replenishing device by the equation τ = f (Vt−Vtref ′) (step S115), and turns on the toner replenishment clutch 24 for τ seconds (S116). The toner replenishing device replenishes the two-component developer in the developing casing 10 with toner when the toner replenishing clutch 24 is on. After that, the control means 16 outputs the output value V from the T sensor 11.
t is fetched (step S117), and it is checked whether the job is completed (step S118). If the job is not completed, the control means 16 executes step S
Return to 114.

In step S104, the control means 16 determines that the emission light amount adjustment value (PWM value) of the P sensor 15 is (PWM1 +
If it is equal to or less than α), the calibration is continued (step S119), and the calibration is finished with the PWM value = predetermined value X (step S120). Control means 1
6 is the final light emission amount adjustment value (PWM value) of the P sensor 15
Is set to X (≤ (PWM1 + α)) (step S12)
1).

Next, the control means 16 controls each part of this embodiment to form a reference image for image density detection on the photoconductor 1 (step S122), and the PWM controller 26.
The P sensor 15 with respect to the reference image on the photoconductor 1 by causing the P sensor 15 to emit light with the set PWM value X
The output value (density) Vsp of 5 is fetched (step S12).
Along with 3), the P sensor 15 is caused to emit light with the set light emission amount of the PWM value X via the PWM controller 26, and the output value (density) Vsg of the P sensor 30 with respect to the non-image portion on the photoconductor 1 is fetched (step S124), step S
Proceed to 110.

The calibration of the P sensor 15 will be described in detail below. The P sensor 15 is calibrated automatically when the main body of the image forming apparatus is turned on, or when a predetermined number of images are formed, or at another predetermined timing. In the calibration of the P sensor 15, first, the control unit 16 controls the charging roller 2 and the developing roller 7 from the power source (not shown) in the same manner as in normal image formation while the main motor 23 rotates the photosensitive member 1.
To the charging voltage and the developing bias voltage,
A non-image area is formed on the surface of the photoconductor 1. The control means 16
In the non-image area, the light emitting element of the P sensor 15 is caused to emit light via the PWM controller 26, and the light receiving element of the P sensor 15 receives the amount of reflected light from the non-image area on the photoconductor 1. The P sensor 15 is controlled via the PWM controller 26 so that Vsg becomes 4.0 (V).
PWM control of the amount of emitted light, that is, the current value flowing through the light receiving element of the P sensor 15 is performed.

The PWM value is represented by 256 gradation data, and is normally set to 50 to 70 when the photoconductor 1 is new. If the mounting position of the P sensor 15 is not uniform or toner or paper powder adheres to the detection surface of the P sensor 15, the amount of light emitted from the P sensor 15 to the photoconductor 1 is reduced and the PWM value is It rises to about 50-90.

When the surface of the photoconductor 1 is scratched or a foreign substance is filmed, the reflectance of the surface of the photoconductor 1 is lowered and the amount of light reflected from the photoconductor 1 is lowered. For this reason, the PWM value becomes even higher, and may rise to about 100 to 200 (see FIG. 4).

Therefore, in the calibration of the P sensor 15 performed each time, the PWM value is the predetermined value (PWM1 +
If it exceeds α), it is determined that it is not due to the mounting position variation of the P sensor 15 or slight stains on the detection surface of the P sensor 15 due to toner or paper powder, but to the large extent due to deterioration of the surface of the photoconductor 1. Then, the subsequent calibration is stopped and the subsequent PWM value is fixed at (PWM1 + α).

In this embodiment, α is set to 30. The reason will be described below. As shown in Fig. 4, with the new photoconductor 1,
The PWM value is 66. Further, the PWM value in the calibration of the photoconductor 1 after the 60K run is 100, and Vsp / Vsg at this time is about 0.17 from FIG. This value is where the P sensor 15 does not make an erroneous determination that the toner concentration TC is considerably low in FIG. Therefore, (PWM1 + 30) is selected as the upper limit value of the emission light amount adjustment value (PWM value) of the P sensor 15 with a slight margin.
Of course, α may be set to a value smaller than 30 if the design has a margin such that TC does not become higher. Similarly, in the embodiments of the present invention described below, α may be arbitrarily set.

As described above, according to the first embodiment, the P sensor 15 obtained by the calibration of the P sensor 15 is performed.
Among the emission light amount adjustment values of P, the means for storing the emission light amount adjustment value PWM1 of the P sensor 15 for the new photoconductor 1 is provided, and the calibration for the second time and thereafter is executed.
The light emission amount adjustment value of the sensor 15 is the first emission light amount adjustment value.
When PWM1 exceeds the predetermined value α or more, the calibration is stopped, and thereafter the emission light amount adjustment value of the P sensor 15 is set to (PW
Since the P sensor 15 is operated by fixing it to (M1 + α), the toner density of the developer is erroneously judged to be considerably low when the photoreceptor is deteriorated due to wax filming and the like, and the toner density of the developer is controlled to be considerably high. Can be solved at low cost only by controlling on software, and it is possible to prevent excessive toner supply.

Next, the toner replenishment control in the second embodiment of the present invention will be explained based on the flow chart shown in FIG. In the second embodiment, the processing flow shown in FIG. 9 is executed instead of the processing flow shown in FIG. 7 in the first embodiment. Steps S200 to S20 shown in FIG.
Since step 4 is the same as steps S100 to S104 shown in FIG. 7, description thereof will be omitted.

The control means 16 adjusts the emission light amount adjustment value (PWM value) of the P sensor 15 to (PWM1 + α).
Even if it exceeds the value, the calibration is continued (step S205), and the emission light amount adjustment value (PW
The calibration ends when M value) = Y (> (PWM1 + α)) (step S206). The control means 16 stores the final PWM value = Y. When the calibration is completed, the control unit 16 displays a warning on the display unit of the operation panel 25 (step S207).

This warning is for notifying the operator that the surface of the photoconductor 1 is being deteriorated or that the surface of the photoconductor 1 is in a seriously deteriorated state. For example, the operation panel On the 25 liquid crystal display, the message "The photoconductor has deteriorated and needs to be replaced early." Is displayed. This warning may be given by voice, sound, blinking of light, or the like, and these characters may be used in combination. Further, this warning is issued by the control means 16 by the P sensor 1
It may be performed immediately after it is determined that the emission light amount adjustment value (PWM value) of 5 exceeds (PWM1 + α). Step S shown in FIG.
208 to S211 are steps S107 to S1 shown in FIG.
Since it is similar to 10, the description thereof will be omitted. After step S211, the control means 16 proceeds to step S111 shown in FIG. Further, from step S220 shown in FIG.
Since S225 is the same as steps S119 to S124 shown in FIG. 7, description thereof will be omitted.

Next, a third embodiment of the present invention will be described based on the flow chart shown in FIG. In the third embodiment, the processing flow shown in FIG. 10 is executed instead of the processing flow shown in FIG. 7 in the first embodiment. Figure 1
Since steps S300 to S304 shown in 0 are similar to steps S100 to S104 shown in FIG. 7, description thereof will be omitted.

In step S304, the control means 16 determines that the emission light amount adjustment value (PWM value) of the P sensor 15 is (PWM1 +
If it exceeds α), the calibration is continued (step S305), and the calibration ends when the PWM value = Y (> (PWM1 + α)) (step S306). The control means 16 controls the final emission light amount adjustment value (PW
Store M value) = Y. When the calibration is completed, the control means 16 determines that the amount of Y exceeding (PWM1 + α) is β
Is greater than (step S30
7) If the amount of Y exceeding (PWM1 + α) is larger than β, the display unit of the operation panel 25 is made to warn the replacement of the photoconductor (step S308). The control unit 16 does not cause the display unit of the operation panel 25 to give a warning when the amount of Y exceeding (PWM1 + α) is β or less. β may be a constant of 0 or more or an arbitrary number of 0 or more. Here, β = 0 in some cases.

Steps S309 to S312 shown in FIG.
Is the same as steps S107 to S110 shown in FIG. 7, and a description thereof will be omitted. After step S312, the control means 16 proceeds to step S111 shown in FIG.
Further, steps S321 to S326 shown in FIG.
Since it is the same as steps S119 to S124 shown in
The description is omitted.

As in the third embodiment, the P sensor 15
If a means for issuing a warning such as replacement of the photoconductor when it exceeds the predetermined level while storing the final light emission amount adjustment value (PWM value) of the photoconductor 1
It is possible to set the service life of, and it is possible to use it in a stable state in the market at all times. However, in this case as well, it goes without saying that the excessive increase in TC can be avoided only by keeping the PWM value when the P sensor 15 emits light at (PWM1 + α).

When the detection surface of the P sensor 15 and the mounting position error are the same, the relationship of Vsp with respect to the PWM value is almost unchanged between the initial stage and the elapsed time of the photoconductor 1 as shown in FIG. That is, the PWM value adjustment up to a certain range is P
Due to dirt of toner or paper powder on the detection surface of the sensor 15,
Alternatively, it can be considered to be due to an error in the mounting position of the P sensor 15, and if the PWM value exceeds a certain range, it can be considered to be due to severe deterioration of the surface of the photoconductor 1.

Actually, when both the P sensor 15 and the photoconductor 1 are new, the variation of the PWM value is about 50 to 75, and the PWM value never exceeds 95. Therefore, in the fourth embodiment of the present invention, the PWM value of the new photoconductor 1 is 66.
When the PWM value is less than (PWM1 + 30) = 96, it is considered that the detection surface of the P sensor 15 is contaminated with toner or paper dust or the mounting position error of the P sensor 15
When the image density of the reference image on the photoconductor 1 is detected, the PWM value is calculated by using the ratio Vsp / Vsg of the P sensor 15 output value Vsp for the P pattern and the P sensor 15 output value Vsg for the background portion of the photoconductor. When PWM1 + 30) = 96 or more, when the image density of the reference image on the photoconductor is detected, as shown in the flowchart of FIG. Only the output value Vsp of the P sensor 15 for the reference image is used in S408. In this case, the control unit 16 causes the P sensor 15 to emit light with the emitted light amount of the set PWM value (PWM1 + α) via the PWM controller 26, and the P sensor 1 for the reference image on the photoconductor 1 is detected.
The output value (density) Vsp of No. 5 is fetched, and the output value (density) Vsg of the P sensor 30 for the non-image portion on the photoconductor 1 is not fetched and the process proceeds to step S111 shown in FIG.
Vsg is used instead of sg.

In the fourth embodiment, the processing flow shown in FIG. 12 is executed instead of the processing flow shown in FIG. 7 in the first embodiment. Step S40 shown in FIG.
0 to S407, S417 to S422 and S423 are steps S100 to S107, S419 to S424 shown in FIG.
Since it is similar to S110, its description is omitted. The control means 16 proceeds from step S422 through step S423 to step S111 shown in FIG.

Next, in the fourth embodiment, P for the reference image
The reason why only the output value Vsp of the sensor 15 is used will be described below. As shown in FIG. 5, in the case of the photosensitive member having the wax filmed, the P sensor 15 determines that the toner concentration TC is considerably low at Vsp / Vsg with respect to the PWM value, although the image ID is 1.25 and is appropriate. It raises TC excessively. On the other hand, in the fourth embodiment, as shown in FIG.
With respect to Vsp with respect to the PWM value, the P sensor 15 determines that TC is almost proper or slightly low, and no trouble occurs due to excessive TC rise. As a result, it is possible to avoid the problem that TC rises too much even if the surface of the photoconductor 1 deteriorates. In addition, in the second embodiment and the third embodiment, the PWM value is (PWM
1 + 30) = less than 96, it is considered that the detection surface of the P sensor 15 is contaminated with toner or paper powder or the mounting position error of the P sensor 15 is considered, and the image density of the reference image on the photoconductor 1 is determined. At the time of detection, the PWM value is (PWM1 + 30) using the ratio Vsp / Vsg of the P sensor 15 output value Vsp for the P pattern and the P sensor 15 output value Vsg for the photoconductor background portion.
= 96 or more, when detecting the image density of the reference image on the photoconductor, the output value V of the P sensor 15 with respect to the background portion of the photoconductor is detected.
Output value Vs of P sensor 15 for the reference image without using sg
You may make it use only p.

Next, a fifth embodiment of the present invention will be described based on the flow chart shown in FIG. In the fifth embodiment, the processing flow shown in FIG. 13 is executed instead of the processing flow shown in FIG. 7 in the first embodiment. The control means 16 is the minimum of the light emission amount adjustment value (PWM value) of the P sensor 15 from the time when the photoconductor (OPC) 1 is new to the time when the light emission amount of the P sensor 15 is adjusted a predetermined number of times (n times). The PWM value of is stored as PWMmin. (Step S50
0). Steps S501 to S503 shown in FIG.
Since it is the same as steps S101 to S103 shown in
The description is omitted.

Next, the control means 16 determines that the PWM value is (PWMmin.
It is checked whether or not + predetermined value α) has been exceeded (step S504). The control means 16 has a PWM value of (PWMmin. +
If α is exceeded, the calibration is stopped (step S505), and the final light emission amount adjustment value (PWM value) of the P sensor 15 is set to (PWMmin. + α) (step S505).
506).

Next, the control means 16 controls each part of this embodiment to form a reference image on the photoconductor 1 on the photoconductor 1 (step S507), and controls the P sensor 15 via the PWM controller 26. The output value (density) Vsp of the P sensor 15 with respect to the reference image on the photoconductor 1 is fetched by emitting light with the light emission amount of the set PWM value (PWMmin. + Α) (step S
508) and P through the PWM controller 26.
The output value (density) Vsg of the P sensor 30 for the non-image portion on the photoconductor 1 is taken in by causing the sensor 15 to emit light with the emitted light amount of the set PWM value (PWMmin. + Α) (step S50).
9). Steps S510, S515 to S5 shown in FIG.
20 denotes steps S110 and S119 to S12 shown in FIG.
Since it is the same as that of 4, the description thereof will be omitted.

In the fifth embodiment, the lowest emitted light amount adjustment value PWMmin.
Since the value obtained by adding the predetermined value α is set to the predetermined fixed value, it is possible to prevent an error due to a difference in environmental conditions or use conditions. In the second to fourth embodiments, as in the fifth embodiment, among the emission light amount adjustment values of the P sensor 15 obtained by the calibration,
Equipped with means for storing the first light emission amount adjustment value of the P sensor 15 to the new photoreceptor 1 to the nth emission light amount adjustment value, the light emission amount of the P sensor 15 obtained by the (n + 1) th and subsequent calibrations. When the adjustment value exceeds the minimum value PWMmin. Of the first emission light amount adjustment value to the nth emission light amount adjustment value by a predetermined value α or more, the calibration is stopped,
After that, the emission light amount adjustment value of the P sensor 15 is set to (PWMmin. +
It may be fixed to α) and only the P sensor 15 may be operated.

[0062]

As described above, according to the present invention, it is possible to solve at a low cost the problem of erroneously determining that the toner concentration is considerably low when the photoconductor deteriorates due to wax filming or the like. It is possible to prevent various toner replenishments. In addition, by performing a calibration and issuing a warning when the light emission amount adjustment value of the image density detection means exceeds a predetermined value, it becomes possible to set the life of the image carrier according to the usage situation and environment, and Therefore, it can be used in a stable state.

Further, the toner replenishment control is performed after fixing the emission light amount adjustment value of the image density detecting means to a predetermined value.
By performing only on the basis of the output value of the image density detecting means with respect to the reference image for detecting the image density obtained by operating the image density detecting means, the toner density increases too much even if the surface of the image carrier deteriorates. The trouble can be avoided.

Further, the emission light amount adjustment value of the image density detecting means obtained by the calibration after the (n + 1) th time is the predetermined minimum value min of the emission light amount adjustment value of the first time to the emission light amount adjustment value of the nth time. When the value exceeds the above, the calibration is stopped, and thereafter, the emission light amount adjustment value of the image density detecting means is fixed to (min + α) and only the image density detecting means is operated. It is possible to prevent an error.

[Brief description of drawings]

FIG. 1 is a block diagram showing a control unit according to a first embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a general relationship between a P pattern toner adhesion amount M / A per unit area on a photoconductor in an image forming apparatus and a P sensor output value Vsp for the P pattern.

FIG. 3 is a correction value Δ of the toner replenishment amount in the image forming apparatus.
It is a figure which shows the example of the table for determining Vt.

FIG. 4 is a diagram showing a result of plotting a light emission amount adjustment value (PWM value) of a P sensor on a horizontal axis and a P sensor output value in a non-image area on a vertical axis of each photoconductor in the image forming apparatus.

FIG. 5 is a diagram showing a relationship between a light emission amount adjustment value (PWM value) of a P sensor and Vsp / Vsg in each photoconductor in the image forming apparatus.

FIG. 6 is a cross-sectional view showing a schematic configuration of the first embodiment.

FIG. 7 is a flowchart showing a part of a toner supply control flow in the first embodiment.

FIG. 8 is a flowchart showing another part of the toner supply control flow in the first embodiment.

FIG. 9 is a flowchart showing a part of a toner supply control flow in the second embodiment of the invention.

FIG. 10 is a flowchart showing a part of a toner supply control flow in the third embodiment of the invention.

FIG. 11 is a diagram showing the relationship of Vsp with respect to the emission light amount adjustment value (PWM value) of the P sensor when the detection surface of the P sensor and the mounting position error are equal in the image forming apparatus.

FIG. 12 is a flowchart showing a part of a toner supply control flow in the fourth embodiment of the invention.

FIG. 13 is a flowchart showing a part of a toner supply control flow in the fifth embodiment of the invention.

FIG. 14 is a diagram showing a correction table for determining a correction amount ΔVt of the toner density control reference value Vtref of the T sensor in the first embodiment.

[Explanation of symbols]

1 photoconductor 2 charging roller 4 Developing device 11 T sensor 16 Control means 24 Toner supply clutch 25 Operation panel 26 PWM controller 27, 28 A / D converter

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2H027 DA10 DD07 DE02 DE07 DE10                       EA06 EC03 EC06 EC07 EC10                       EC20 GA23 GA30 GA47 GA48                       GB05                 2H077 AB02 AB14 AC02 AD02 AD06                       DA03 DA10 DA42 DA47 DA52                       DA63 DB02 DB10 EA01

Claims (10)

[Claims] 1. A developing unit for supplying toner to a latent image formed on an image carrier to visualize the latent image, a toner replenishing unit for supplying toner to the developing unit, and the image carrier. And an image density detecting means for detecting an image density of a reference image for image density detection formed on the image carrier, and an output value of the image density detecting means for a non-image portion on the image carrier is a predetermined value. Calibration is performed to adjust the amount of light emitted from the image density detecting means, and based on at least the output value of the image density detecting means with respect to the reference image on the image carrier, the toner replenishing means to the developing means. In the image forming apparatus for controlling toner replenishment to the image forming apparatus, one of the image density detecting means for the new image carrier is included in the emission light amount adjustment value of the image density detecting means obtained by the calibration. A means for storing the light emission amount adjustment value of the eye is provided, and the calibration is performed for the second time and thereafter, and the light emission amount adjustment value of the image density detecting means exceeds the light emission amount adjustment value of the first time by a predetermined value α or more. In this case, the calibration is stopped, and thereafter, the light emission amount adjustment value of the image density detecting means is fixed to (+ α) to operate the image density detecting means. 2. The image forming apparatus according to claim 1, wherein the calibration is executed and a warning is issued when the emission light amount adjustment value of the image density detecting means exceeds (+ α). Forming equipment. 3. The image forming apparatus according to claim 1, wherein when the calibration is executed and a light emission amount adjustment value of the image density detecting means exceeds (+ α), a warning is given and the calibration is performed. The final emission light amount adjustment value of the image density detecting unit is continuously stored, and thereafter, the emission light amount adjustment value of the image density detecting unit is (+ α).
An image forming apparatus, characterized in that the image density detecting means is fixed to operate the image density detecting means. 4. The image forming apparatus according to claim 3, wherein when the numerical value of the emission light amount adjustment value of the image density detecting means exceeds (+ α) is β, the warning is given depending on the degree of β. An image forming apparatus characterized by the absence thereof. 5. The image forming apparatus according to claim 2, wherein the warning is given via a display section of an operation panel. 6. The image forming apparatus according to claim 2, wherein the warning is given by sound or voice. 7. The image forming apparatus according to claim 1, wherein the toner replenishment control is performed after the emission light amount adjustment value of the image density detecting means is fixed to (+ α). An image forming apparatus, characterized in that it is performed based on only an output value of the image density detecting means for a reference image for detecting the image density obtained by operating the image density detecting means. 8. The image forming apparatus according to claim 1, further comprising a toner density detecting means for detecting a toner density of the developing means, and a toner corresponding to an output value of the toner density detecting means. The density control reference value is corrected based on the output value of the image density detection means, and the toner replenishment is controlled by the output value of the toner density detection means based on the corrected toner density control reference value. Image forming apparatus. 9. The image forming apparatus according to claim 1, wherein a new image carrier is included in the emission light amount adjustment value of the image density detecting unit obtained by the calibration. With respect to the image density detecting means for the first-time emission light amount adjustment value to the image carrier for the n-th emission light amount adjusting value, and (n + 1) th and subsequent calibrations. The obtained light emission amount adjustment value of the image density detecting means is 1
The calibration is stopped when the minimum value min of the n-th emission light amount adjustment value to the n-th emission light amount adjustment value exceeds a predetermined value α, and thereafter, the emission light amount adjustment value of the image density detecting means is set to (min + α). ), And only the image density detecting means is operated. 10. The image forming apparatus according to claim 1, further comprising a unit that can arbitrarily change the α.