JPH0695509A - Developing device - Google Patents

Abstract

PURPOSE:To shorten the time required for setting the control voltage of a developing device having an L-type toner concn sensor. CONSTITUTION:When a new developer is loaded into a developing device by control of CPU 30, an initialization button 31 is pressed for setting the initialization mode and the developing device is driven for a predetermined period of time while no toner is supplied; during the period the output voltage VL of a concn. sensor 33 at a first checkpoint is compared with that at a second checkpoint, and when the difference is less than a predetermined value a semi- fixed resistance 39 is adjusted at the second checkpoint so as to initialize the control voltage VC of the concn. sensor 33, while when the difference is at or greater than the predetermined value the control voltage VC of the concn. sensor 33 is initialized after the device is driven for the predetermined driving period.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device loaded with a two-component developer used in an image recording device such as an electrophotographic copying machine, and more particularly to a method for initially setting a control voltage of a toner density sensor of the developing device. It is about.

[0002]

2. Description of the Related Art In an image recording apparatus such as an electrophotographic copying machine, an original is irradiated with light to form an electrostatic latent image on an image carrier by reflected light from the original, and this is used as a visible image on recording paper. The recording is performed on the recording paper, or an electric signal representing an image from the outside is recorded on the recording paper as a visible image.

In this type of image recording apparatus, a visible image is formed by a developing device using a two-component developer composed of toner and carrier, and this is recorded on recording paper. In the two-component developer, the toner is mixed at a constant mixing ratio with respect to a constant weight of carrier. This toner decreases as the image is recorded, so that it affects the density of the recorded image. Therefore, in order to always obtain a recorded image of a constant density, it is necessary to detect the toner density and, when the toner density decreases, replenish the toner and control the toner density to fall within an appropriate range.

By the way, for the toner density detection, a method of optically detecting the density of the toner image detected by a small piece of the reference density, or an L detection toner density sensor including a coil at a position in contact with the developer is installed. There is known a method of knowing the toner concentration (toner mixing rate) in the developer by measuring the magnetic permeability of the toner. The method based on the measurement of magnetic permeability is excellent in that it can always be measured and there is no need to change the image recording process. It is possible to compare the detected toner density with a toner density reference value and replenish the toner to keep the toner density in a preferable state.

The L detection toner density sensor is, for example, TDK.
There is a toner concentration sensor manufactured by Co., Ltd. (model programmable toner sensor), which is composed of an oscillation circuit including the above coil and a frequency / voltage conversion circuit. The relationship between the toner concentration and the output voltage is Has a small negative characteristic. This L detection toner density sensor has a control voltage input terminal, and the output voltage of the density sensor can be adjusted by changing the control voltage applied to this input terminal. FIG. 4 is a graph showing an example of the relationship between the control voltage of the L detection toner density sensor and the output voltage, and shows the case where the toner density is 5% by weight.

[0006]

However, the output characteristic of the toner density sensor applied to the developing device of such an image recording apparatus is not always constant, and varies depending on the error in the mounting position when the toner is mounted on the developing device. Therefore, the output of the toner concentration sensor is not constant and varies.

Further, as the two-component developer is used, the charge holding ability of the toner deteriorates. So for example 15,0
It is necessary to replace with a new developer every time 00 sheets are recorded. The new two-component type developer has insufficient agitation or has been stationary for a long time during storage, so the charge of the toner decreases and the repulsive force between the toners also decreases, so the number of carriers per unit volume increases. . Therefore, even though the toner density is constant, the apparent magnetic permeability changes so as to become large, so that the output of the L detection toner density sensor becomes large and the apparent toner density becomes low. . When the new developer is stirred, the charge amount of the toner increases with the stirring time and eventually reaches a saturated state. Therefore, the output of the L detection toner concentration sensor has a curve as shown in FIG. 3, the output in the initial stage of stirring rapidly decreases, and after the stirring for a certain period of time, it shows a constant output. That is, there is a property that the apparent density of the new developer changes with stirring time.

Since there are variations in the output characteristics of the L detection toner concentration sensor and the apparent toner concentration change due to stirring of the new developer as described above, a predetermined value is set every time the developer in the developing device is replaced with a new one. After stirring for a certain period of time, unless the initial setting for adjusting the control voltage so that the output voltage of the L detection toner concentration sensor becomes a predetermined value with respect to the toner concentration of the predetermined developer, the developer is made to have an appropriate toner concentration. Cannot be maintained. Moreover, the curve of the above output fluctuation is shown in FIG.
As indicated by a, b, and c, there are large variations in the time required to settle at a constant output, depending on the type and lot of the developer. For this reason, for safety, a predetermined stirring time (for example, 3 minutes) is set according to the developer that requires the longest time, and stirring is performed for a long time even for a developer that can obtain a constant output in a short time. Since the initial setting is performed after that, there is a problem that the adjustment work takes a lot of time and is complicated.

An object of the present invention is to solve the above problems and to provide a developing device capable of finishing the adjustment in a short time when the developer is replaced with a new one.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a toner concentration sensor for detecting a toner concentration of a developer by detecting a change in magnetic permeability of a two-component developer composed of toner and carrier. In a developing device for controlling the toner concentration of a developer, when the developing device is newly loaded with the developer, the developing device is driven for a predetermined time, and the developing device is driven at a first check time and a second check time shorter than the predetermined time. The output of the toner concentration sensor is compared, and if the difference is within a predetermined value, the second
This is achieved by a developing device characterized in that the control voltage of the toner concentration sensor is initialized at the time of checking, and if the difference is not less than a predetermined value, the control voltage is initialized after driving for the predetermined time.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a sectional view showing an example of the developing device 10 of the present invention. The schematic configuration and function of the developing device will be described with reference to FIG.

In FIG. 2, 6 is a photosensitive drum which is an image bearing member, 33 is the above-described L detection toner density sensor (hereinafter simply referred to as density sensor), and 34 is toner for detecting the toner remaining amount from vibration during toner replenishment. Remaining amount sensor, 35 is toner replenishing means, 35a and 35b are gears driven when replenishing toner, 35c is a ladder chain driven by gears 35a and 35b, and 35d is toner attached to the ladder chain 35c. A carriage, 41 is a toner replenishing cartridge, 42 is a replenishing roller for replenishing the toner conveyed by the carriage 35d of the toner replenishing means, 43 is a main agitator for agitating the developer consisting of toner and carrier, and 44 is also agitating A sub-agitator, 45 is a developing sleeve that develops toner by adhering toner to the electrostatic latent image on the photosensitive drum 6, and 46 is the height of the brush of the developer on the developing sleeve 45. It is napping regulating plate to win.

Next, the operation of the developing device 10 will be described. The toner supplied from the toner cartridge 41 is transferred to the replenishment roller 42 by the carriage 35d by the gears 35a and 35b being rotated by the rotation of a toner replenishing motor (not shown) to move the ladder chain 35c in the direction of the arrow. Carriage 35d
Toner sensor 34 installed on the slope where the toner is carried
Does not oscillate when there is an obstacle in front of the sensor surface,
Since there is a characteristic that the output oscillates and the output is turned on when there is no obstacle, the presence or absence of toner is determined by. The rotation of the supply roller 42 causes the toner to drop downward. Then, the developer (toner and carrier) already in the developing device 10 and the toner are agitated by the main agitator 43 and the sub agitator 44. A concentration sensor 33 whose output voltage changes according to the toner concentration of the developer is installed below the sub-agitator 44, and detects the change in the toner concentration of the developer in the developing device 10. The ears of the developer are formed on the developing sleeve 45, and the height of the ears is regulated by the ears rising regulation plate 46, and the ears are conveyed to the developing area to develop the latent image on the photosensitive drum 6. A visible toner image is formed.

FIG. 1 is a block diagram showing an example of the control circuit of the present invention.

In the figure, 30 is a CPU for controlling each part of the image recording apparatus, 31 is an initial setting button for setting or canceling the initial setting mode of the control voltage, 32 is for confirming the above input, and 32 from the CPU 30. A message, for example, a display section for displaying a toner shortage when the remaining amount of toner falls below a specified amount, 33 is the density sensor, TI is a drive voltage input terminal, and TL
Is an output terminal, TC is a control voltage input terminal, and G is a ground terminal. 34 is the toner remaining amount sensor, 36 is a toner replenishing motor that drives the toner replenishing means 35, 37 is a toner replenishing motor drive circuit that drives the toner replenishing motor 36, and 38 is a DC power supply that supplies a control voltage to the density sensor 33. , 39 are semi-fixed resistors for adjusting the control voltage.

Next, a method for initially setting the control voltage of the density sensor according to the present invention will be described. When a new developer having a specified toner concentration is loaded into the developing device when the device is manufactured or due to deterioration of the developer, a manufacturing engineer or a service person presses the initial setting button 31 to enter the initial setting mode. Can be switched. As a result, the CPU 30 drives the developing device 10 and switches the toner supply so as not to be performed. The serviceman outputs the output voltage VL of the density sensor 33 at the first check time (for example, 45 seconds after the start of driving).
And the output voltage VL at the second check time (for example, 90 seconds after the start of driving) are compared, and if the voltage difference is less than or equal to a predetermined voltage difference (for example, 0.02 V), the control voltage VC is immediately initialized. That is, the semi-fixed resistor 39 is adjusted to change the control voltage VC so that the output voltage VL of the concentration sensor 33 is, for example, 1.5V.
Try to be. If the above voltage difference is 0.02
If it is equal to or higher than V, the control voltage VC is initialized after a predetermined driving time (for example, 3 minutes) of driving the developing device 10 so that the output voltage VL of the density sensor 33 becomes 1.5V.

Thus, the initialization of the control voltage VC is completed, and the initialization button 31 is pressed again to return to the image recording mode.

When image recording is started, the CPU 30 compares the output voltage VL of the density sensor 33 with a reference value (1.5 V in this case) every time image recording is performed, and when VL becomes higher than the reference value,
The toner replenishment motor drive circuit 37 is operated for a predetermined time according to the difference, and the toner replenishment motor 36 is driven to replenish toner to the developer by the toner replenishment means 35 in the developing device 10. As a result, the toner concentration of the developer is always kept in the proper range.

In this embodiment, the manual initialization of the control voltage VC has been described, but the CPU 30 automatically causes the concentration sensor 33 to detect the first check time and the second check time.
Output voltage VL is compared, and if the voltage difference is within a predetermined value, the control voltage VC is initialized at the time of the second check. If the voltage difference is above the predetermined value, the developing device 10 is driven for a predetermined time and then the control voltage is controlled. It is also possible to perform the initial setting of VC.

[0021]

As described above, in the developing device of the present invention, when the developing device is newly loaded with the developer having the specified toner concentration, the first check time and the second check which are shorter than the predetermined stirring time are performed. The output voltage of the concentration sensor obtained at the time is compared with the output voltage of the concentration sensor, and if the difference is within a predetermined value, the control voltage of the concentration sensor is set at the second time. Since the control voltage is set, the variation of the toner concentration sensor is corrected, the toner concentration of the developer is always kept in an appropriate range, the recording image quality is maintained in good condition, and the developer of the developing device is replaced. The control voltage setting work done every
It has become possible to shorten it to nearly two.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an example of a control circuit of the present invention.

FIG. 2 is a cross-sectional view showing a developing device which is an embodiment of the present invention.

FIG. 3 is a graph showing changes in the output voltage of the concentration sensor due to stirring of a new developer.

FIG. 4 is a graph showing the relationship between the control voltage of the density sensor and the output voltage.

[Explanation of symbols]

 6 Photoconductor drum 10 Developing device 30 CPU 31 Initial setting button 33 Density sensor (L-type toner density sensor) 35 Toner replenishing means 36 Toner replenishing motor 37 Toner replenishing motor drive circuit 38 DC power supply 39 Semi-fixed resistance

Claims (1)

[Claims] 1. A developing device for controlling the toner concentration of a developer, comprising a toner concentration sensor for detecting a change in magnetic permeability of a two-component developer comprising toner and carrier to detect the toner concentration of the developer. When a new developer is loaded in the developing device, the developing device is driven for a predetermined time, and the output of the toner concentration sensor at the first check time and the second check time shorter than the predetermined time is compared. If the difference is within a predetermined value, the control voltage of the toner concentration sensor is initialized at the time of the second check, and if the difference is more than the predetermined value, the control voltage is initialized after driving for the predetermined time. And developing device.