JPS61281266A - Developing agent detecting device - Google Patents

Abstract

PURPOSE:To hold constantly the toner concn. in a developing agent and to obtain a satisfactory reproducing picture by setting the detecting timing to detect the presence and absence of the developing agent and making different the oscillating force of the piezoelectric element with a detecting timing and a non-detecting timing. CONSTITUTION:The waveform 17 of the oscillating output of a piezoelectric element 4 is a vibrating mode when a switch is OFF, shows the oscillating output at the time of the non-load to which the pressure of a developing powder 3 is not applied and a waveform 18 shows the oscillating output at the time of the load to which the pressure of the developing powder 3 is applied. On the other hand, a waveform 19 shows the oscillating output at the time of the non-load when the switch 15 is ON, a waveform 20 shows the time of the load, the piezoelectric element 4 receives the pressure by the developing agent 3 for which fluidity is lowered, and the condition that the oscillation is stopped is shown. Consequently, by using the piezoelectric element 4 of the strong oscillating condition shown in the waveform 17, the toner, etc., stuck to the piezoelectric element 4 are shaken down, and by using the output of the piezoelectric element 4 of the oscillating condition shown in a waveform 19 or 20, the toner concn. in the developing agent 3 is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a device that controls toner density, etc. by detecting the presence or absence of developer on the surface of a piezoelectric element.

[Traditional technique]

FIG. 3 is a longitudinal sectional view showing an example of the main parts of the developing device.

The figure is provided on the developing roll 1. This is a developing device that regulates developer 3 to a constant thickness using a doctor blade 2, and is provided with a piezoelectric element 4 as a sensor for detecting the amount of developer 3. As shown in the figure, the piezoelectric element 4 is installed so as to face the flow direction of the developer 3 and tilted at a predetermined angle.

When the developer 3 is a two-component developer composed of toner and carrier, if there is enough toner in the developer 3, the ratio of carrier with good fluidity in the developer 3 is small, and the developer Agent 3 draws a large arc as shown by arrow P (
On the other hand, it exhibits a fluid state.

If the toner in the developer 3 is insufficient, the developer 3
This is because there is a large proportion of toner with poor fluidity.

The developer 3 exhibits a small-turn fluid state as shown by an arrow Q.

9. For example, 1 using only magnetic toner as the developer 3.
The component development method has a similar configuration.

When the flow state is indicated by arrow P, there is a sufficient amount of developer 3, and when it is indicated by arrow Q, there is a small amount of developer 3.

Similar to the two-component development method, toner is replenished by a control circuit shown in FIG. 2, which will be described later.

FIG. 2 is a circuit diagram of a conventional toner concentration control device including a piezoelectric element 4. As shown in FIG.

Here, some explanation will be given regarding this control circuit. The piezoelectric ceramic that constitutes the piezoelectric element 4 has a characteristic that when an alternating voltage is applied, it repeatedly expands and contracts according to the polarity of the electric field. In this case, the figure shows a positive feedback oscillation circuit using the piezoelectric element 4 itself as an oscillator. be. Therefore, this piezoelectric element 4 serves both as a single oscillator and as a sensor that detects the fluidity of the developer 3 as pressure. Here, for example, as shown in the figure, the coupling ratio of the piezoelectric element 4 is 1 α2.

The attenuation factor due to the resistance R+ from the amplifier 7 with the amplification factor -A is α
If it is 1, then the 1 transmission condition is.

(-A)・α1・ (−α2)〉1・・・・・・(1)
Then, R1. R2: Represented as resistance. Therefore, if the amplification factor -A and the attenuation factor α1 are appropriately set, a single oscillation circuit is established.

Therefore, when the toner is consumed and the toner concentration in the developer 3 decreases, the fluidity of the developer 3 improves as described above and the pressure on the piezoelectric element 4 decreases, so that the bonding ratio -α2 of the piezoelectric element 4 decreases. As the voltage increases, the oscillation of the piezoelectric element 4 becomes strong (and continues).

Therefore, the oscillation output from the amplifier 7 is compared with a reference value in the detection comparison circuit 8.

Since the oscillation output is larger, transistor 9 is turned on.
A replenishment signal 10 is generated. This replenishment signal 10 drives the toner replenishment roller 5 to perform a toner replenishment operation. On the other hand, if there is a sufficient amount of toner in the developer 3, the fluidity of the developer 3 deteriorates as described above, increasing the pressure on the piezoelectric element 4 and lowering the coupling ratio -α2, resulting in a small and unstable oscillation output. or oscillation stops.

In this case, transistor 9 is turned off and replenishment signal 10
This does not occur, and the toner replenishing roller 5 is not driven to replenish toner.

As described above, in the conventional toner replenishment operation, when the pressure of the developer 3 applied to the piezoelectric element 4 increases, the toner replenishment roller 5 stops replenishing the toner, and the pressure of the developer 3 decreases or increases. When the toner runs out, toner replenishment begins. That is, this operation keeps the toner concentration of the developer 3 constant.

[Problems with conventional technology]

However, in such conventional toner density control devices, when the carrier wears out due to high temperature and high humidity or long-term use and its fluidity deteriorates, or after a long period of non-use, the developer 3 is If the fluidity becomes worse than when it was set, and the developer 3 becomes stuck to the surface of the piezoelectric element 4, which is the detection sensor, the piezoelectric element 4 will be different when the developer 3 is present and when it is not. There is no vibration.

Even if toner is consumed and the toner density decreases, the lack of toner cannot be detected and the image quality deteriorates significantly.In addition, in the two-component developing system, a carrier pull phenomenon occurs. This has become a big problem.

[Purpose of the invention]

In view of the above-mentioned conventional drawbacks, the present invention provides an oscillation (vibration) of a detection section including a piezoelectric element for a certain period of time when a piezoelectric element detects a pressure change due to fluidity of developer to control toner concentration.
By increasing the output and once shaking off the developer on the surface of the piezoelectric element, the piezoelectric element performs one normal detection operation, thereby maintaining the toner concentration in the developer at a constant level and obtaining a good reproduced image. The purpose of this invention is to provide a toner density control device that makes it possible to do this.

[Key points of the invention]

In order to achieve the above object, the present invention provides a developer detection device that uses a piezoelectric element to detect the presence or absence of a developer on the surface of the piezoelectric element, in which a detection timing for detecting the presence or absence of the developer is set, and a detection timing for detecting the presence or absence of the developer is set. It is characterized in that the oscillation output of the piezoelectric element is made different between detection timing and non-detection timing.

[Embodiments of the invention]

Hereinafter, two embodiments of the present invention will be described based on FIG. 1 and FIG. 4 onwards. Note that the same members as in the conventional example are designated by the same reference numerals, and their explanations will be omitted.

First, the configuration will be described.

FIG. 4 is a sectional view of a developing device having a toner density control device of the present invention, and FIG. 5 is a sectional view of the developing device as well.
Indicates a state where there is little toner in the developing device.

The developing device 26 used in the present invention includes a developing hopper 27
Inside the sleeve 28. Stirring roll29. Doctor blade as a regulating member 2. A piezoelectric element 4 is arranged as a detection sensor, a toner storage section 6a for storing replenishing toner 6 is formed in the upper part of the development hopper 27, and a toner replenishment roller 5 is provided below this toner storage section 6a. .

The sleeve 28 is made of a non-magnetic cylinder made of aluminum or the like, and rotates in the direction of the arrow. A magnet roll 1 magnetized with multiple poles is fixedly arranged inside the sleeve 28, and the developer 3
is attracted to the surface of the sleeve 28. The developer 3 is composed of a mixture of a carrier whose main component is a magnetic material and has a particle size of 20 to 200 μm, and a toner whose main component is a resin. The carrier may also be a magnetic material coated with resin or a carrier mixed with resin. Piezoelectric element 4
is for detecting the fluidity of the developer 3.

Next, to briefly describe the operation of the developing device 26 based on the above configuration, the photoreceptor 30 passes through a charging and exposure area (not shown), and is connected to the developing device 26 while holding an electrostatic latent image corresponding to the original image. It enters the opposing development area 30b.

The developer 3 consisting of carrier and toner is transferred to the stirring roll 29
The photoreceptor 3 is agitated and triboelectrically charged.
It is charged with a polarity opposite to that of the electrostatic latent image formed on the surface. The developer 3 is adsorbed on the surface of the sleeve 28, and is conveyed in the direction of the arrow by the rotation of the sleeve 28. The thickness of the developer 3 is regulated by passing through the doctor blade 2, and is directed to the developing area 30b with the photoreceptor 30. Sent.

In the developing area 30b with the photoreceptor 30, the developer 3 forms spikes with the main pole N+ of the developing roll 1 and comes into contact with the surface of the photosensitive layer 30a, and the electrostatic latent image is visualized by toner. The developer 3 after development is stirred by the stirring roll 29 and sent onto the sleeve 28 again.

By the way, the developer 3 conveyed on the sleeve 28 is
The height of the brush is regulated to a certain level by the doctor blade 2, but the excess developer 3 that is being conveyed collides with the doctor blade 2, and rises along the doctor blade 2 due to the conveyance force of the sleeve 28. arise. Then, the developer 3 reaches a position where it is not affected by the magnetic field of the developing roll 1 after being raised, and flows down as shown by arrow S, collapsing while contacting the surface of the piezoelectric element 4. Here, two flows of the developer 3 occur, one being conveyed to the doctor blade 2 and the other flowing down.

On the other hand, FIG. 1 shows a circuit diagram of a toner density control device which is a main part of the present invention. The diagram shows a positive return circuit 11 consisting of a resistor R3, a piezoelectric element 4, and an amplifier 7.

A resistor Ra connected in series from the connection point 12 of resistors R3 and R4,
A circuit 13 grounded via Rs, and both resistors Ra,
It is composed of a switch circuit 16 that connects a connection point 14 of Rs to ground via a switch 15.

Further, the oscillation output from the amplifier 7 is input to a detection comparison circuit 8, and the detection comparison circuit 8 compares the oscillation output with a reference value set in advance within the detection comparison circuit s.

The comparison result of the detection comparison circuit 8 is input to the base of a transistor 9, and when the output of the detection comparison circuit 8 is a high signal, the transistor 9 is turned ON, and when the output of the detection comparison circuit 8 is a low signal, the transistor 9 is turned OFF.

Voltage element 4 described in the above-mentioned configuration and the above-mentioned prior art page
Due to the characteristics of switch 1, the attenuation factor from amplifier 7 is
5 is ON, and when switch 15 is OFF.

becomes. In other words, when the switch 15 is OFF, expressed by equation (4), the attenuation rate is larger than when it is ON, expressed by equation (3), so as can be understood from the oscillation condition of equation (1) above, positive feedback is generated. The rate increases and stronger oscillations occur.

FIG. 6 is a diagram showing the waveform of the oscillation output of the piezoelectric element 4 at this time. Waveform 17 is the vibration mode when the switch 15 is OFF, and is a so-called no-load mode in which the pressure of the developer 3 is not applied. The waveform 18 shows the oscillation output during so-called load when the pressure of the developer 3 is applied. Even at this time, the oscillation conditions are met and oscillation continues. on the other hand.

Waveform 19 shows the oscillation output under no load when the switch 15 is ON, and waveform 20 shows the oscillation output under load. Indicates a stopped state.

Therefore, the toner and the like adhering to the piezoelectric element 4 are screened off using the piezoelectric element 4 in the strong oscillation state shown in waveform 17, and the developer 3 is removed using the output of the piezoelectric element 4 in the oscillation state shown in waveform 19 or 20. It turns out that it is sufficient to detect the toner concentration within the range. FIG. 7 is a time chart showing the operation timings of the toner sieving operation (hereinafter referred to as vibration mode) and toner concentration detection operation (hereinafter referred to as detection mode) of the piezoelectric element 4. FIG. 2A shows a state where the timing of the drive motor (not shown) 21 is ON, that is, the photosensitive drum 30 is rotating and a copying operation is being performed. Reference numeral 22 indicates a state in which the drive motor is OFF, that is, the photosensitive drum 30 has stopped rotating and no copying operation is being performed. 011) in the figure shows the oscillation output of the piezoelectric element 4, which can be set to vibration mode 23 by switching the switch 15 as described above. Detection mode 24 is performed alternately.

During the vibration mode 23, no development is performed, and during the detection mode 24, development is performed. In other words, the detection mode 24 is applied only during the period when the drive motor is 0N21 (the period when copying is being performed), and the piezoelectric element 4 is always in the vibration mode 23 when the drive motor is 0FF22, and the piezoelectric element 4 is in the vibration mode 23 when the drive motor is OFF22. This action is performed to sift off toner, etc.

Further, a period (detection period) 25 in which the toner concentration is actually detected by the control circuit is a part of the period in which the piezoelectric element 4 is in the detection mode 24. In other words, the detection timing is set during this period and the actual detection operation is performed.

Let me summarize what I have explained above.

The piezoelectric element 4 operates as a vibrator in the vibration mode 23, and the strong vibrations of the piezoelectric element 4 shown in waveforms 17 and 18 shake off toner, etc., thereby eliminating toner on the surface of the piezoelectric element 4 and its vicinity, which has been a problem in the past. Toner concentration detection operation is performed by the piezoelectric element 4 vibrating as shown in the waveform 19 or 20 during the detection period 25, which is a certain period after turning on the switch 15 and lowering the oscillation output to the detection level. This is how the toner density is controlled.

Therefore, according to the toner density control device of this embodiment,
When the developer concentration of the developer 3 is relatively high, the fluidity of the flowing developer 3 is poor and the contact resistance with the surface of the piezoelectric element 4 is high, so that the control circuit does not output and toner replenishment is not performed.

On the other hand, as the development cycle is repeated and the toner concentration of the developer 3 decreases, the fluidity of the developer 3 becomes good and the contact resistance with the surface of the piezoelectric element 4 decreases.

A signal for rotating the toner replenishing roller 5 is output from the control circuit, and a toner replenishing operation is performed. As a result, the toner concentration of the developer 3 is always kept constant.

That is, toner replenishment control is always performed accurately by changing the fluidity of the developer 3 on the surface of the piezoelectric element 4 according to the toner concentration of the developer 3.

The implementation of toner density control using the secondary developer has been described above, but the replenishment control of the primary developer and the like have been described.

Of course, the present invention can also be applied to toner hopper detection of secondary toner.

〔Effect of the invention〕

As described above, according to the present invention, the oscillation output of the toner density control circuit including the piezoelectric element is increased to eliminate the adhesion of developer on the piezoelectric element.

The present invention provides a device that controls toner density by lowering the detection level of a toner density control circuit and setting a detection timing to detect the presence or absence of developer.

Even when developer fluidity deteriorates, such as at high temperature and high humidity, when detecting the presence of developer toner 4, there is no developer attached to the surface of the piezoelectric element, and accurate and reliable developer (toner) is detected. ) can be detected. Therefore, a reproduced image developed by a developing device that always has a constant amount of developer is a good reproduced image without carrier drag.

[Brief explanation of drawings]

FIG. 1 is a toner density control circuit diagram which is a main part of the present invention. FIG. 2 is a control circuit diagram used for conventional developer presence/absence detection. FIG. 3 is a cross-sectional view of the developing device showing the flow state of the developer in the detection device. FIGS. 4 and 5 are cross-sectional views showing embodiments of the present invention. FIG. 6 is a waveform diagram of oscillation output for the piezoelectric element in the present invention. FIG. 7 is a time chart for detecting the presence or absence of developer. 1...Developing roll. 2...Doctor Blade. 3...Developer. 4...Piezoelectric element. 5... - Toner supply roller. 6. . . Toner. 7...Amplifier. 8...Detection comparison circuit. 9...Transistor. 10...Replenishment signal. 11...Positive feedback circuit. 12... Connection point. 13...Circuit. 14... Connection point. 15...Switch. 16...Switch circuit. 17... Waveform. 18... Waveform. 19...Waveform. 20... Waveform. 21... Timing when the drive motor is ON'. 22... Timing when the drive motor is OFF. 23... Vibration mode. 24...Detection mode. 25...Detection period. -α2...Binding rate. -A...Amplification factor. α1... Attenuation rate (conventional example). α1'...Attenuation rate (when switch is ON). α1"... Attenuation rate (when switch is OFF). R1, R2... Resistance. R3, Ra, Rs... Resistance. Patent Applicant: Casio Computer Co., Ltd. Same as above
Casio Electronics Co., Ltd.Figure 1Figure 3Figure 4Figure 5Figure 6Figure 7

Claims (2)

[Claims] (1) In a developer detection device that uses a piezoelectric element to detect the presence or absence of developer on the surface of the piezoelectric element, a detection timing for detecting the presence or absence of the developer is set, and the detection timing and non-detection timing are set as described above. A developer detection device characterized by varying the oscillation output of a piezoelectric element. (2) The developer detection device according to claim 1, wherein the oscillation output of the piezoelectric element at the detection timing is smaller than the oscillation output of the piezoelectric element at the non-detection timing.