JPH0713427A - Developing device - Google Patents

Abstract

PURPOSE:To reduce cost and to accurately detect the shortage of toner. CONSTITUTION:A current I flowing through a developing roller shaft 30 is detected by a current detection circuit 38 when development is not performed. When the toner is sufficient, the current I flows by friction between the toner 22 and a toner supply roller 24, a developing roller 26 and a doctor blade 28, and when the toner is insufficient, it becomes larger by the friction between the blade 28 and the developing roller 26. Reference values Is1 and Is2 based on which the shortage of the toner and insufficient electrostatic charged amount are judged are previously set, and compared with the current I by a comparison circuit 40. When I>Is1 is obtained and a toner detection circuit 42 detects the shortage of the toner, an agitator 20 is driven by an agitator control circuit 44 so as to supply the toner 22 to a developing tank 16. When I<Is2 is obtained and the electrification amount of the toner is insufficient, a relay 46 is turned on, so that voltage is impressed on the blade 28 and charge is forcibly injected in the toner 22.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device, and more particularly, it is used in an image forming apparatus such as a copying machine, an image recording device, a printer and a facsimile, and uses a one-component developer and detects a shortage of the developer. Having means,
The present invention relates to a developing device.

[0002]

2. Description of the Related Art Conventionally, various sensors have been used as a toner remaining amount detecting means in a developing device such as an electrophotographic device using a one-component developer. For example, JP-A-3
In Japanese Patent Laid-Open No. 18880 [G03G 15/08], there is disclosed a toner remaining amount detecting device in which a light emitting diode and a phototransistor are combined, and JP-A-3-3-3.
In 9765 [G03G 15/08],
A piezoelectric vibration type toner sensor is shown.

[0003]

In the former case, it is necessary to secure a path through which light passes, and the remaining toner amount cannot be accurately detected unless the light transmitting surface is always cleaned. In the latter case, the sensor is provided in the developing device unit, and there is a design restriction on the installation location of the sensor. Therefore, the sensor cannot always be installed at the best position, and the remaining toner amount cannot be accurately detected. Also, the developing device itself is a consumable item,
Providing an expensive sensor in the developing device also has the disadvantage of increasing the cost.

Further, since various sensors as toner residual amount detecting means are generally installed in the toner tank, both of the above-mentioned two conventional techniques include the toner which cannot be actually supplied to the developer carrier. The remaining amount is being detected. Also,
Since the actual amount of toner adhered on the developer carrier is not detected, it may be judged that the toner is insufficient even if there is no problem in printing, or conversely, a warning of insufficient toner may be issued even if printing defects occur. There was an inconvenience of not notifying the user.

Therefore, a main object of the present invention is to provide a developing device capable of accurately detecting a toner shortage without increasing the cost.

[0006]

SUMMARY OF THE INVENTION The present invention is a developing device including a developer carrying member and a layer thickness controlling means for controlling the layer thickness of the developer on the developer carrying member. Current detection means for detecting the current value of the current generated by at least one of friction with the developer, friction between the layer thickness regulation means and the developer, and friction between the developer carrier and the layer thickness regulation means, and the current value is preset. The developing device is provided with a comparison unit that compares the reference value with the reference value, and a shortage detection unit that detects whether or not a developer shortage has occurred based on a comparison result from the comparison unit.

[0007]

The value of the current flowing through the developer carrying member is detected by the current detecting means during non-development, for example. When the amount of the developer adhering to the developer carrier is sufficiently large, an electric current flows through the developer carrier due to the friction between the developer and the layer thickness regulating means and the friction between the developer and the developer carrier. When the amount of the developer adhered to the developer carrying member is small, the layer thickness regulating means and the developer carrying member come into contact with each other, and the friction increases the current value flowing through the developer carrying member. Therefore, a reference value is set in advance so that the shortage of the developer can be detected, and this reference value is compared with the current value flowing through the developer carrying member by the comparison means. Based on the comparison result, the shortage detection means determines whether or not the developer adhering to the developer carrier is insufficient. If the developer is insufficient, for example, the developer is replenished or the control panel is provided with the developer. Display a shortage and warn the user.

[0008]

According to the present invention, since it is not necessary to use an expensive sensor or the like as in the conventional case, the cost can be reduced. Further, since the shortage of the developer attached to the developer carrier can be detected, the shortage of the toner can be detected considerably more accurately than before. The above-mentioned objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of the embodiments with reference to the drawings.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, the developing device 10 of this embodiment.
Is a one-component non-magnetic contact developing device. The developing device 10 includes a toner unit 12. The toner unit 12 includes a toner container 14 and a developing tank 16.
And are formed. A shaft 18 is provided in the toner storage portion 14.
The agitator 20 attached to the developing tank 16 is provided, and the toner 22 is supplied to the developing tank 16 by the agitator 20. As the toner 22, for example, a non-magnetic negatively charged toner whose main component is styrene-acrylic resin is used. The toner 22 sent to the developing tank 16 is supplied to the developing roller 26 by the toner supply roller 24. A thin toner layer is formed on the surface of the developing roller 26 by the doctor blade 28 attached to the toner unit 12 and arranged upstream of the developing roller 26. Developing roller 26
Is rotatably supported by the developing roller shaft 30, and the toner 22 is transferred by the developing roller 26 to the latent image formed on the surface of the photosensitive drum 32, which is an electrostatic latent image carrier, to visualize the electrostatic latent image. To do. A negatively charged organic photoconductor is used as the photoconductor drum 32, and the photoconductor drum 32 is grounded as shown in FIG. Then, the remaining toner 2
The toner 2 passes through the toner leakage prevention member 34 provided on the inner surface of the toner unit 12 and on the downstream side of the developing roller 26 and returns to the developing tank 16 again.

A voltage is applied to the developing roller shaft 30 by a voltage source 36. Voltage source 3
A current detection circuit 38 for detecting the value of the current flowing from the developing roller 26 to the developing roller shaft 30 is connected in series to 6, and one end of the current detection circuit 38 is grounded. A comparison circuit 40 is connected to the current detection circuit 38. In the comparison circuit 40, the current value detected by the current detection circuit 38 is compared with the reference value. The toner detection circuit 42 connected to the comparison circuit 40 detects whether or not the toner 22 attached to the developing roller 48 is insufficient based on the comparison result of the comparison circuit 40. If the toner 22 is insufficient, a signal for notifying the toner shortage is given from the toner detection circuit 42 to the agitator control circuit 44, and the agitator control circuit 44 drives the shaft 18 to rotate the agitator 20. The toner 22 is supplied to the developing tank 16 by the rotation of the agitator 20. When the toner 22 attached to the developing roller 48 is full, the agitator control circuit 44
Does not drive shaft 18.

When the toner detection circuit 42 detects that the toner charge amount is insufficient, the relay 46 is turned on and the voltage based on the voltage generation source 36 is applied to the doctor blade 28. As a result, the charge is forcibly injected into the toner 22 to compensate for the toner charge amount shortage. In operation, first, the surface potential of the photoconductor drum 32 is adjusted to -700V by the charging device 52 (shown in FIG. 2), and the developing roller shaft 30 has a developing bias potential of -300V on the developing roller shaft 30. Is applied.

The toner 22 sent from the toner accommodating section 14 to the developing tank 16 is supplied to the developing roller 26 by the toner supply roller 24, and the developing roller 26 rotates to contact the developing roller 26 with the doctor blade 28. Four
It is transported to 8. At this time, the toner 22, the toner supply roller 24, the toner 22, the developing roller 26, and the toner 22
Friction occurs between the doctor blade 28 and the doctor blade 28, and the toner 22 is negatively charged. In this case, as the material of the developing roller 26, silicone rubber or the like located at a position apart from the toner material in the triboelectric charging series is suitable.

Then, the toner 2 supplied to the contact portion 48
The conveyance of No. 2 is regulated by the doctor blade 28, and is thinned on the developing roller 26. The toner layer thickness is regulated to about 10 to 30 μm, and the toner 22 is conveyed to the photosensitive drum 32. The developing roller 26 itself is pressed against the photosensitive drum 32 by a spring or the like (not shown),
The development nip is appropriate in the development area 50 (approximately 1-2 mm)
The electrostatic latent image on the photosensitive drum 32 is developed.

As described above, the toner 22 is negatively charged, so that the developing roller shaft 30 has the structure shown in FIG.
A current I flows as shown in (B) and. First, FIG.
At the time of development shown in (A), the surface potential of the photosensitive drum 32 becomes a residual potential of about −100 V as an exposure potential. At this time, since the photosensitive drum 32 is developed by the negatively charged toner 22, that is, the negative toner 22 moves from the developing roller 26 to the photosensitive drum 32, the current I flows in the opposite direction of arrow a. On the other hand, in the non-developing state of FIG. 2B, the developing roller 26 and the toner 22 are
Since the developing roller 26 is positively charged and the toner 22 is negatively charged by the friction with the current I, the current I flows in the direction of arrow b.

At this time, at the time of development, the amount of toner given to the photoconductor drum 32 for development, that is, the amount of charge of the entire toner 22 given to the photoconductor drum 32 changes depending on the original, so that the flowing current value changes. To do. On the other hand, at the time of non-development, the current value I is stable because the current I flows only by friction. Therefore, it is not suitable for detecting the toner shortage at the time of development in which the current value varies depending on the original to be copied, and detects the toner shortage at the time of non-development. That is, it is desirable that the sampling of the current I be performed during non-development, that is, during warming up or while the main motor (not shown) is stopped after image output. However, even at the time of development, if you prepare a specific original (for example, the one with the entire surface painted in black) and detect the current value that flows when copying this original at the time of determination, the toner shortage can be detected. it can.

The current I as described above is detected by the current detecting circuit 38.
2 is consumed, and the amount of toner 22 in the toner storage portion 14 and the developing tank 16 is reduced. Then, the amount of toner supplied to the contact portion 48 that forms the toner 22 in a thin layer decreases, and finally, the developing roller 26 and the doctor blade 28.
Partially comes into contact with. Then, the friction between the developing roller 26 and the doctor blade 28 causes excessive triboelectric charge, and the flowing current value increases. Therefore, the current value that is normally generated when the toner 22 is interposed between the developing roller 26 and the doctor blade 28 is set in advance in the comparison circuit 40 (for example, stored in the memory), and this is set as the reference value I _s1. And Then, the comparison circuit 40 compares the current value I supplied from the current detection circuit 38 with the reference level I _s1, and if I> I _s1 , the toner detection circuit 42 _{uses the} toner 2
Detect a shortage of 2.

FIG. 3 shows the result of measuring the value of the current I output from the current detection circuit 38. The horizontal axis represents time and the vertical axis represents the value of the generated current I. In the vertical axis of FIG. 3, the (+) side is the non-developed state and the (−) side is the developed state. In this case, when Io> I _s1 , that is, time P
The toner shortage occurs, and the agitator 20 is rotated to compensate for the toner shortage.

Further, under environmental conditions, especially under high temperature and high humidity, the amount of electric charge generated by friction of the toner 22 is reduced, and image deterioration may occur. In order to avoid this, in addition to the above-mentioned upper limit reference value I _s1 , the lower limit reference value I
Provide _s2 . When the current I is below the reference value I _s2 ,
The toner detection circuit 42 turns on the relay 46, and a voltage is applied to the doctor blade 28. Then, electric charges are forcibly injected into the toner 22, and the amount of toner charge is increased, so that the current I satisfies I _s1 <I <I _s2 , and image deterioration is prevented. As described above, by adjusting the toner charge amount, a stable and good image can be obtained under any environment.

According to this embodiment, by forming a circuit such as the toner detection circuit 42 on the high-voltage board (not shown) side of the main body side without using an expensive sensor as in the prior art, The cost of the toner unit 12, which is a consumable item, can be reduced. In addition, like the other developing device 10 shown in FIG.
Toner supply roller 1 is turned on by turning on relay 46.
Alternatively, a voltage may be applied to 4. Then, the electric charge is forcibly injected into the toner 22 and the current I becomes I _s1 <I
<I _s2 is set.

Further, in the developing device 10 of the other embodiment shown in FIG. 5, unlike the embodiment of FIG. 1, the developing device unit 54 in which the toner container 14 and the developing tank 16 are not distinguished from each other is used. Then, the replacement timing of the developing device 10 is determined based on the output of the toner detection circuit 42. That is, when the toner detection circuit 42 detects that the toner 22 is insufficient, the control panel (not shown) or the like displays "Insufficient toner" to warn the user. Therefore, in this case, unlike the embodiment of FIG. 1, the agitator 20, the shaft 1
8 and the agitator control circuit 44 are unnecessary. The rest of the configuration and operation are the same as in the embodiment of FIG. 1, and therefore their explanation is omitted here.

Further, as in the developing device 10 shown in FIG. 6, a voltage may be applied to the toner supply roller 24 by the relay 46. The toner 22 may be positively charged. Also, in the above embodiment,
Although the toner 22 is used as the developer, a two-component toner containing a toner and a carrier may be used as the developer.

[Brief description of drawings]

FIG. 1 is an illustrative view showing one embodiment of the present invention.

FIG. 2 is an illustrative view showing a direction of a current flowing through a transfer roller shaft.

FIG. 3 is a graph showing a result of actually measuring a temporal change of an output current I.

FIG. 4 is an illustrative view showing another embodiment of the present invention.

FIG. 5 is an illustrative view showing another embodiment of the present invention.

FIG. 6 is an illustrative view showing still another embodiment of the present invention.

[Explanation of symbols]

 10 developing device 22 toner 24 toner supply roller 26 developing roller 28 doctor blade 30 transfer roller shaft 38 current detection circuit 40 comparison circuit 42 toner detection circuit

Claims (1)

[Claims] 1. A developing device comprising a developer carrying member and a layer thickness regulating means for regulating the layer thickness of the developer on the developer carrying member, wherein the friction between the developer carrying member and the developer, Current detecting means for detecting a current value of a current generated by at least one of friction between the layer thickness regulating means and the developer and friction between the developer carrying member and the layer thickness regulating means, the current value and preset A developing device, comprising: a comparison unit that compares the reference value with the determined reference value; and a shortage detection unit that detects whether or not a developer shortage has occurred based on a comparison result from the comparison unit.