JPH01129274A - Toner concentration controller - Google Patents

Abstract

PURPOSE:To control the temperature compensation of a toner sensor which is influenced by the change of the temperature of developer by using a temperature sensor already provided in an image forming device. CONSTITUTION:When real temperature of the developer is below (t) and the detected temperature by the temperature sensor 202 is (t) or above, a control means 203 controls an output from the toner sensor 201 to be VC. In such a case, the toner concentration is kept lower than at the time when a 1st set value is VA. When the detected temperature of the temperature sensor 202 becomes below (t) in such a state, 1st and 2nd set values are reset in VA and VB and the toner sensor 201 temporarily outputs the output VC since the toner concentration can not change suddenly from the concentration corresponding to the output VC from the toner sensor 201. It is assumed VC<VB, so that the image forming device 205 is not stopped and a display means 206 does not perform displaying. Thus, the temperature compensation of the toner sensor can be performed without malfunction.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a toner sensitivity control device for a developing device using a two-component developing agent, and is used in electrophotographic copying machines, laser printers, and the like.

(B) Conventional technology Conventionally, this type of toner sensitivity control device generally uses a toner sensor that detects changes in developer inductance due to changes in toner concentration, and ensures that the output of the sensor is always constant. Controls the toner replenishment means, and if the toner concentration drops below a predetermined value even after driving the toner replenishment means, it is determined that all the replenishment toner has been consumed and this is displayed to the user, or I am trying to stop the copying machine.

(c) Problems to be Solved by the Invention However, when toner concentration is detected by changes in inductance, it is necessary to temperature-compensate the output of the toner concentration sensor because the inductance has a characteristic of changing depending on the temperature of the developer. . However, providing a dedicated temperature sensor for detecting the temperature of the developer for this purpose is not preferable because it increases the number of parts of the device and leads to an increase in cost.

This invention was made in consideration of these circumstances,
The present invention provides a toner density control device that performs temperature compensation control of a toner sensor that is affected by changes in developer temperature by using a temperature sensor already provided in an image forming apparatus.

(d) Means to solve problems FIG. 1 is a block diagram showing the structure of the present invention.

201 is a toner sensor that detects the toner concentration in the developing device by a change in inductance; 202 is a temperature sensor that is installed near the photoconductor and detects the surface temperature of the photoconductor; −
When the set value VA is reached, the toner replenishing means 204 is activated, and when the toner density further decreases and the output of the toner sensor reaches the second set value V a (V a > V A ), the image forming apparatus 205 is stopped. Or display means 206
A control means 207 for displaying the first set value Vc (V
A<Vc<Va), set the second set value vo(vo
>ve).

(E) Effect In FIG. 1, when the actual developer temperature is lower than t and the temperature detected by the temperature sensor 202 exceeds t, the control means 203 sets the first set value to Vc and the second set value to Vo. The toner replenishing means 204 is driven by correcting the toner density, that is, the output of the toner sensor 201 becomes V.
Control so that it becomes C. In this case, since the developer temperature is lower than t, the toner concentration is maintained lower than when the first set value is VA. Then, when the detected temperature of the temperature sensor 201 becomes lower than t while the output of the toner sensor 201 is maintained at Vc, the first and second set values are reset to VA and VB.

At this time, since the toner concentration cannot suddenly change from the concentration corresponding to the output Vc of the toner sensor 202, the toner sensor 202 temporarily outputs the output Vc. However, V c <
Since it is Va, the image forming bag R2O5 may stop or
The display means 206 does not perform any display.

(f) Examples The present invention will now be described in detail based on examples shown in the drawings. This invention is not limited by this.

FIG. 2 is a configuration diagram showing the main parts of an electrophotographic copying machine to which an embodiment of the present invention is applied, in which 1 is a photosensitive drum, 2 is a developing device incorporating an agitation roller 2a and a developing roller 2b, and 3 3a is a toner hopper that stores toner; 3a is a toner replenishment roller that is provided at the bottom of the toner hopper and replenishes the toner contained in the toner box 3 to the developing device 2 when driven by a toner replenishment motor (not shown); 4 is a toner replenishment roller that replenishes the toner contained in the toner box 3; A cassette that stores the transfer paper, 5 a paper feed roller that conveys the transfer paper, 6 a registration roller that synchronizes the transfer paper with the rotation of the photoreceptor drum l, and 7 a transfer member that transfers the toner image on the photoreceptor drum to the transfer paper. 8 is a separation charger that separates the transfer paper from the photoreceptor l; 9 is a conveyance belt that transports the transfer paper to a fixing device (not shown); IO is a cleaning unit that cleans the surface of the photoreceptor drum l; 11 is a photoreceptor drum L is the image light that irradiates the photoreceptor drum L to form an electrostatic latent image;
A temperature sensor t3 detects the surface temperature of the photosensitive drum and corrects the image density, and a toner sensor 14 detects the toner density of the developing device 2 by a change in inductance.

FIG. 3 is a block diagram showing the main parts of the control circuit of the embodiment shown in FIG. 2, and 21 is a ROM and a CPU.

A microcomputer consisting of RAM and an I10 board (
(hereinafter referred to as a microcomputer), 22 is an indicator light, and 24 is a copying device. When the toner sensor 14 detects that there is no toner in the toner hopper 3 by human power, the indicator light 22 lights up and the copying device 24 stops.

Further, 23 is a motor that drives the toner replenishment roller when the toner concentration in the developing device 2 becomes less than a predetermined value by the toner sensor 14. The temperature is also input to the toner sensor 14 and used for temperature correction of the toner sensor 14.

FIG. 4 shows the relationship between the toner concentration (%) and the toner sensor output voltage (V) in this example with respect to the temperature change of the developer. This indicates that the output voltage of the sensor 14 increases by 1v.

By the way, in this embodiment, the most preferable image density is obtained when the toner concentration of the developer is 4%, and if the toner concentration exceeds 4.5% or falls below 3.5%, the image quality of the copied image deteriorates. . Therefore, from the relationship shown in Figure 4, the temperature 20
℃, when the output voltage of the toner sensor 14 reaches the reference voltage VA (=7V), the motor 23 is driven and toner is replenished, and when the reference voltage reaches the reference voltage Vs (=8.5V), the indicator light 22 turns on. The light is turned on and the copying device 24 is controlled to be stopped. If control is continued using these reference voltages VA and V, when the developer temperature reaches 35°C or higher, the toner density will be maintained at a value exceeding 4.5%,
%, the copying machine 24 is stopped and the indicator light 22 is turned on. Therefore, in this case, the reference voltage VA
, VB must be compensated for changes in developer temperature. By the way, in this invention, FIGS. 2 and 3
As shown in the figure, since the temperature sensor 13 is also used to detect the temperature change of the photoreceptor drum 1 to detect the temperature change of the developer, there is a relationship between the developer temperature inside the developing device 2 and the temperature around the drum. is as shown in FIG. 5(a), and when the temperature of the phenomenon agent is 35°C, the temperature sensor 13 detects a temperature of 37°C.
Detected as . Therefore, when the temperature sensor 13 outputs 37°C, the reference voltage VA.

From the relationship shown in Figure 4, VB is VC (=8.0V), respectively.
Vo (=9.5V) L: Corrected (VA<
Vc<Ve,Vo>VJ.

Next, the operation of the embodiment with such a configuration will be explained using the flowchart shown in FIG.

If the temperature of the developer is 35°C or lower, that is, the temperature sensor 13 is
If the temperature is below 7°C, no temperature correction is performed (step 10IL) and the output of the sensor 14 is set to the reference voltage VA.
(=7V) (step 102), the motor 23
is driven for one second, toner is supplied from the toner hopper 3 to the developing device 2 (step 103), and the output voltage of the toner sensor 14 matches the reference voltage VA as shown in (a) of the time chart shown in FIG. In other words, the toner concentration is controlled to be 4% (FIG. 4).

When the toner in the toner hopper 3 runs out, the output voltage of the toner sensor 14 reaches Va (=8.5V) (step 104), the indicator light 22 is turned on, and the copying device 24 is stopped (step 105). Then, when the toner hopper 3 is filled with toner by the user after time T, the routine of steps 102 to 104 is repeated, and the toner concentration is again changed to the output voltage of the toner sensor 4 as shown in FIG. 7(b). is controlled to match the reference voltage VA.

Next, when the temperature of the developer exceeds 35°C, the temperature around the drum, that is, the temperature detected by the temperature sensor 13, becomes 37°C.
, the microcomputer 21 sets the set value VA (= 7 V
) and Va (=8.5V) respectively as VC (=8
, OV ) and Vo (=9.5V). Therefore, in step 106 of FIG.
When the output voltage exceeds Vc (=8.OV), the motor 23 is driven for 1 second (step 107), and the output voltage of the toner sensor 14 reaches the reference voltage VC+, [holding voltage] as shown in FIG. 7(c). be done. Then, the toner hopper 3 runs out of toner, and the output voltage of the toner sensor 14 becomes the reference voltage V. (=9.5V) (step 108), the indicator light 22 is turned on and the copying machine 24 is stopped. Then, when the toner hopper is filled with toner by the operator after time T, the routine of steps 106 to 108 is repeated, and the output voltage of the toner sensor 14 is changed to (
As shown in d), toner is supplied to the phenomenon device 2 by the motor 23 so as to return to VC.

By the way, in this invention, in order to compensate for the temperature of the developer as described above, the temperature sensor 13 that detects the temperature around the drum is used. In this case, the developer temperature is room temperature (20
Even if the temperature around the drum is (I) in Figure 5,
1+), the temperature exceeds 37°C and can even reach 40°C. In this case, the microcomputer 1 determines that the developer temperature has risen, and sets the reference voltages VA and VB to V.
c and Vo, and the output of the toner sensor 14 for the developer whose temperature has not actually increased is read and compared with the reference voltages Vc and Vo. That is, the output of the toner sensor 14 is controlled to be Vc (=8.OV), and the toner concentration is reduced (see FIG. 4). However, as the temperature around the drum decreases, the reference voltage V c, V
oh< VA, V al: When reset, the toner concentration cannot change suddenly and the output of the toner sensor 14 will maintain VC for a while, but each set value is as shown in Figures 4 and 7. Since the relationship vA<vc<Va exists, there is no need for the indicator light 22 to turn on or for the copying machine 24 to be stopped. However, each set value is V A<
When the relationship is set as Va<Vc<Vo, the temperature around the drum that once rose as described above will fall again, and the set value will become Vc due to the output of temperature sensor I3.
, Vo to V A .

When the setting is switched to Va, even though there is sufficient toner in the toner hopper 3, the indicator light 22 is turned on and the copying device 24 is stopped, causing inconvenience in use.

By determining each set value of the toner concentration in this way, it becomes possible to perform temperature compensation of the toner sensor output due to a change in the temperature of the developer using a temperature sensor that measures the temperature around the drum.

(g) Effects of the Invention According to the present invention, it is possible to compensate for the temperature of the toner sensor without malfunction by reusing the temperature sensor that detects the surface temperature of the photoreceptor.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of the present invention, FIG. 2 is an explanatory diagram of a partial configuration of an electrophotographic copying machine to which an embodiment of the present invention is applied, and FIG. 3 is a control diagram of the embodiment shown in FIG. Blocks showing the main parts of the circuit. Figure 4 is a graph showing the relationship between toner concentration and toner sensor output voltage with respect to developer temperature. Figure 5 is a graph showing the relationship between developer temperature and drum surrounding temperature. This figure is a flowchart showing the operation of the embodiment shown in FIG. 2, and FIG. 7 is an explanatory diagram showing temporal changes in the toner output voltage. I3... Temperature sensor, 14... Toner sensor, 21... Microcomputer, 22...
...Indicator light, 23...Motor, 24...
・・・Copying device. Fig. 2 Fig. 3 Fig. 4 Toshi-ji ■ (o/.) Fig. 5] Noe I Kamei Ai 1-ji na (C) Fig. 6 Fig. 4-AI>-1: Tagai-(〉)

Claims (1)

[Claims] 1. A photoreceptor on which an electrostatic latent image is formed, a developing device for developing the photoreceptor with a two-component developer, and a toner replenishing means for replenishing the developing device with toner from a toner container. In an image forming apparatus, there is a toner sensor that detects the toner concentration in the developing device by changes in inductance, a temperature sensor that is installed near the photoconductor that detects the surface temperature of the photoconductor, and a temperature sensor that detects the toner concentration in the developing device by detecting the surface temperature of the photoconductor. When the first set value is reached, the toner replenishing means is activated, and when the toner concentration further decreases and the output of the toner sensor reaches a second set value that is larger than the first set value, a display is displayed or the image forming apparatus is stopped. and a correction means for increasing the first set value to a value smaller than the second set value and correcting the second set value to a larger value when the temperature sensor detects a predetermined temperature or higher. A toner density control device comprising: