JP2006350072A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus having a toner quantity detection means capable of linearly detecting the residual quantity of toner. <P>SOLUTION: An ultrasonic sensor is used as the means for detecting toner quantity, and the toner quantity is measured by counting time from the reflection of an ultrasonic wave transmitted from a transmission part side on the upper surface of toner in a toner container up to reception of the reflected ultrasonic wave on a receiving part side. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus having toner amount detecting means for detecting the amount of toner in a toner container.

  Conventionally, a toner container for supplying toner to a developing unit for developing an electrostatic latent image formed on a photosensitive member of an image forming apparatus such as a copying machine, a printer or a facsimile using an electrophotographic system with a two-component developer is provided. As a method for detecting the remaining amount of toner in the toner container, toner amount detection using a piezoelectric element is widely known. This utilizes the fact that an element is incorporated in the toner container, the frequency of the element is small when the toner is in the toner container, and the frequency is increased when the toner is exhausted. However, the piezo element method can only determine the presence or absence of toner, and it is difficult to detect the remaining amount of toner in a linear manner, and there has been a problem that many elements must be provided in order to carry out fine detection.

  Further, the toner amount detection method using a piezo element has the following problems. That is, since the piezo element is a contact type sensor, the surface cleaning member is necessary because the detection accuracy becomes unstable due to toner adhesion on the sensor surface. As a cleaning member, PET (polyethylene terephthalate) or the like is generally used as a means for cleaning the sensor surface. However, a so-called kamakura phenomenon in which a void is formed may occur depending on the stop position of the cleaning member. This is a false detection in which it is determined that there is no toner despite the presence of toner. When this erroneous detection occurs, the toner is excessively supplied, and in the worst case, the toner leaks to the outside and the inside of the machine becomes dirty.

In order to solve the above problems, it has been proposed to use a transmission optical sensor, a reflection optical sensor, or a transmission ultrasonic sensor that detects toner without contact. (For example, Patent Document 1)
In order to detect the amount of toner in the rotating toner bottle, a means for measuring the toner amount by measuring the mass of the toner bottle or a means for measuring the ultrasonic transmittance has been proposed. (For example, Patent Document 2)
Japanese Patent Laid-Open No. 2000-221864 JP 2004-286793 A

  However, Patent Documents 1 and 2 propose means for using ultrasonic transmittance as means for detecting the amount of toner. In the case of a transmission type, the ultrasonic transmission side and reception side of the ultrasonic sensor are connected to a toner container or Position adjustment, toner adhesion cleaning means on the sensor surface, and the like must be provided on the opposite side of the toner bottle. In particular, in the case of a toner bottle, since the bottle confidence is rotated, a problem occurs in the toner amount detection accuracy.

  An object of the present invention is to use an ultrasonic sensor as means for detecting the amount of toner, and to measure the time until the ultrasonic wave transmitted from the transmitting unit is reflected on the toner upper surface of the toner container and received by the receiving unit. Thus, the toner amount is measured, and a stable toner amount detecting means is provided.

The above object can be achieved by the following configuration.
(Claim 1)
An image forming apparatus comprising: a developing unit that develops an electrostatic image formed on an image carrier with toner; a toner container that supplies toner to the developing unit; and a toner amount detection unit that detects the amount of toner in the toner container. In
The toner amount detection means comprises an ultrasonic sensor and a time measurement means,
The ultrasonic sensor has an ultrasonic transmitter and an ultrasonic receiver, the ultrasonic transmitter transmits toward the upper surface of the toner in the toner container, and the ultrasonic receiver reflects from the upper surface of the toner. Configured to receive the ultrasonic waves
The time measuring means measures the time until an ultrasonic wave is transmitted from the ultrasonic wave transmitting unit and the ultrasonic wave reflected by the ultrasonic wave receiving unit is received.
An image forming apparatus.
(Claim 2)
The toner container according to claim 1, further comprising a toner stirring member that rotates in the toner container, and a control unit that controls the stirring member so that a rotation stop position of the stirring member is lower than the upper surface of the toner. Image forming apparatus.
(Claim 3)
The horn having a small mouth portion and a large mouth portion is provided between the ultrasonic sensor and the toner upper surface portion, and the small mouth portion of the horn is disposed on the ultrasonic sensor side. The image forming apparatus described.
(Claim 4)
The image forming apparatus according to claim 3, wherein a member of the horn is covered with a sound absorbing material.
(Claim 5)
Control means for controlling the time from when the ultrasonic wave is transmitted from the ultrasonic wave transmission unit until the ultrasonic wave reflected by the ultrasonic wave reception unit is received to be longer than the reverberation time of the ultrasonic sensor. The image forming apparatus according to claim 1, further comprising: an image forming apparatus according to claim 1;

  According to the first aspect of the present invention, the ultrasonic sensor has an ultrasonic transmitter and a receiver, the ultrasonic transmitter transmits the toner toward the upper surface of the toner in the toner container, and the receiver receives the toner. Since the amount of toner is detected from the time when the ultrasonic wave reflected from the upper surface is received, the remaining amount of toner can be detected linearly.

  According to the second aspect of the present invention, since the rotation stop position of the stirring member is controlled to be lower than the upper surface of the toner, the distance between the sensor surface and the stirring member is not erroneously measured.

  According to the third and fourth aspects of the present invention, since the horn covered with the sound absorbing material is provided and the ultrasonic sensor is provided in the lip portion of the horn, the directivity of the ultrasonic wave is improved.

  According to the fifth aspect of the present invention, since there is a control means for making the time from when the ultrasonic wave is transmitted until the ultrasonic wave reflected by the receiving unit is received longer than the reverberation time of the ultrasonic sensor, Since there is no overlap between the sensor reverberation time and the sensor reverberation time on the receiving side, there is no detection error.

<Image forming apparatus>
FIG. 1 is a cross-sectional view of an image forming apparatus as an example of the image forming method of the present invention.

  In FIG. 1, reference numeral 50 denotes a photosensitive drum (photosensitive member) which is an image carrier, and is driven to rotate in the clockwise direction. Reference numeral 52 denotes a scorotron charger (charging means) for uniformly charging the circumferential surface of the photosensitive drum 50 by corona discharge. Prior to the charging by the charger 52, the peripheral surface of the photosensitive member may be discharged by performing exposure by the pre-charging exposure unit 51 using a light emitting diode or the like in order to eliminate the history of the photosensitive member in the previous image formation.

  After uniform charging of the photoreceptor, image exposure based on the image signal is performed by an image exposure unit 53 as an image exposure unit. The image exposure unit 53 in this figure uses a laser diode (not shown) as an exposure light source. Scanning on the photosensitive drum is performed by the light whose optical path is bent by the reflection mirror 532 through the rotating polygon mirror 531 and the fθ lens, and an electrostatic latent image is formed.

  In the digital image forming method, a reversal development process is generally used. In the reversal development process, the surface of the photosensitive member is uniformly charged by the charger 52 and the image exposure is performed, that is, the exposed portion potential of the photosensitive member. In this image forming method, the (exposed area) is visualized by a developing process (means). On the other hand, the unexposed portion potential is not developed by the developing bias potential applied to the developing sleeve 541.

  The electrostatic latent image is then developed by a developing device 54 as developing means. A developing device 54 containing a two-component developer composed of a magnetic carrier and a non-magnetic toner is provided at the periphery of the photosensitive drum 50, and development is performed by contact between the rotating developing sleeve 541 and the photosensitive member. Is called. Normally, development is performed by applying a direct current bias between the photosensitive drum 50 and the developing sleeve 541 and, if necessary, an alternating current bias voltage. Further, the developer is developed in a non-contact state with respect to the photoreceptor. The potential of the photosensitive member is measured by providing a potential sensor 547 above the development position as shown in FIG.

  The recording paper P is fed to the transfer area by the rotation operation of the paper feed roller 57 when the transfer timing is ready after the image formation.

  In the transfer area, a transfer electrode (transfer means: transfer device) 58 is operated on the peripheral surface of the photosensitive drum 50 in synchronization with the transfer timing, and the charged recording paper P is charged with a polarity opposite to that of the toner. Transfer the toner.

  Next, the recording paper P is neutralized by a separation electrode (separator) 59, separated by the peripheral surface of the photosensitive drum 50 and conveyed to the fixing device 60, and the toner is removed by heating and pressurization of the heat roller 601 and the pressure roller 602. After the welding, the sheet is discharged to the outside of the apparatus via the sheet discharge roller 61. The transfer electrode 58 and the separation electrode 59 stop the primary operation after passing through the recording paper P, and prepare for the next toner image formation. In FIG. 1, a transfer band electrode of corotron is used as the transfer electrode 58. The transfer electrode setting conditions vary depending on the process speed (peripheral speed) of the photosensitive member and cannot be specified. For example, the transfer current is set to +100 to +400 μA, and the transfer voltage is set to +500 to +2000 V. can do.

  On the other hand, after the recording paper P is separated, the photosensitive drum 50 removes and cleans residual toner by pressure contact of the blade 621 of the cleaning device (cleaning means) 62, and again performs charge removal by the pre-charge exposure unit 51 and charging by the charger 52. Then, the next image forming process is started.

<Developing means>
Next, the developing means 54 and the toner replenishing means 40 will be further described with reference to the schematic diagram of FIG. FIG. 2B is a perspective view of the toner container portion.

  In FIG. 2A, a developing device 54 is a developing means using a known technique of electrophotography, and is a developing sleeve 541 made of a non-magnetic material that is formed in a cylindrical shape that faces the photoreceptor 50 and can rotate. A developer conveying member 542 for supplying the developer to the developing sleeve 541 and a developer agitating member 543 for agitating the developer and the toner are provided. The developing sleeve 541 is provided with a plurality of magnets for adsorbing the developer.

  The developing device 54 is provided with toner density detecting means T1. The toner concentration detecting means T1 is a widely used publicly known means for capturing a change in toner density, which is a mixing ratio of toner and carrier, as a change in magnetic permeability. When the toner density falls below a preset density value, toner supply from the toner supply means 40 is executed.

<Toner supply means>
The toner supply unit 40 includes a toner container 410, a toner discharge unit 420, a horn 430, a toner stirring member 440, a toner amount detection unit T2, and the like.

The toner amount detection means T2 is attached to the fore edge portion side of the horn 430. (See Fig. 2 (b))
The toner amount detection means T2 includes a reflection type ultrasonic sensor 470 provided with an ultrasonic transmission unit 450 and an ultrasonic reception unit 460 on the same surface. By measuring the time until the ultrasonic wave transmitted from the ultrasonic wave transmitting unit 450 is reflected by the object and received by the ultrasonic wave receiving unit 460, the distance to the object at the shortest distance can be measured.

Ultrasonic waves propagate in air at a velocity of about 344 m / sec (20 ° C.). Accordingly, the time T (seconds) required for reciprocating the distance of L1 mm is T = L1 × 2/344000.
It is. Therefore, when the ultrasonic wave is transmitted from the transmitter, the reflected wave returned to the object is received by the receiver, and the time interval t is measured, the distance D (mm) to the object is
D = L1 / T × t = 172000 × t
Thus, it is possible to know the distance to the object in the ultrasonic wave transmission direction. If the bulkiness when the toner is full in the toner container 410 is Dmax, the remaining amount of toner is expressed by the product of the difference, the toner container 410 opening area, and the toner density. That is, the remaining amount of toner = (Dmax−D) × the toner container opening area × the toner density. However, since the variable in the above equation is (Dmax-D), the remaining amount of toner can be substituted with (Dmax-D).

  In the present invention, the amount of toner in the toner container 410 is detected by measuring the reflection time until receiving the reflected wave returned when the ultrasonic wave transmitted from the transmitter of the ultrasonic sensor 470 hits the upper surface of the toner.

  FIG. 3 is a timing chart showing the process from reception of the reflected wave returned from the ultrasonic wave transmitted from the transmitter of the ultrasonic sensor 470 to the time when the time measurement means performs waveform processing.

  The transmission pulse transmitted from the transmitter 450 of the ultrasonic sensor 470 is a rectangular wave and is repeatedly transmitted at the same interval (FIG. 3a). The received wave reflected from the toner upper surface of the toner container 410 is received by the receiving unit 460 as shown in FIG. At this time, when there is a received wave that cannot be waveform-shaped as shown in FIG. 3e, the control unit of the waveform processing control unit 500 shown in FIG. 4 provides a predetermined threshold (FIG. 3f) obtained experimentally. Judge as disturbance (referred to as electrical noise) and do not perform waveform shaping. Further, even if the received wave is equal to or greater than the threshold value as shown in FIG. 3g, it is determined as electrical noise when it is ½ or less of the reference received wave arrival time or when it is twice or more the reference received wave arrival time as shown in FIG. Similarly, waveform shaping is not performed. When a waveform as shown in FIG. 3c is received, waveform processing is performed (FIG. 3j).

  The waveform processing control unit 500 repeatedly measures the time from when the transmission pulse is transmitted to when the waveform-shaped rectangular wave of FIG. 3c is received, obtains an average value t1 of the time interval, and calculates the sensor and toner upper surface. The control is performed to determine the remaining amount of toner by calculating the distance D1 up to.

  FIG. 4 is a block diagram schematically showing toner amount detection using the ultrasonic sensor 470. The waveform processing control unit 500 incorporates a CPU 1 (central processing unit), and the transmission pulse transmitted from the ultrasonic transmission pulse generation unit in the waveform processing control unit 500 is transmitted through the transmission circuit to the ultrasonic sensor 470. Is transmitted from the ultrasonic transmission unit 450 toward the upper surface of the toner in the toner container 410. The ultrasonic receiving unit 460 receives the ultrasonic wave reflected from the upper surface of the toner, and the received signal is converted into a rectangular wave by the waveform processing unit of the CPU 1 via the receiving circuit and the reception waveform shaping circuit. Here, the distance is calculated from the time when the transmission pulse is transmitted and the time when the rectangular wave is received.

  When it is determined that the amount of toner in the toner container 410 is less than the specified amount, the CPU 1 displays a message “Toner is low” on a display unit (not shown). The CPU 1 has a toner density control function, and controls the toner replenishment drive device (not shown) so as to obtain an appropriate toner density based on the toner density information from the toner density detecting means T1.

<Toner container>
Next, the toner container 410 will be described. The toner agitating member 440 functions to agitate the toner by a rotating blade-like agitating member to make the toner bulk density constant and move the toner to the toner discharging means 420. At this time, if the blade-like stirring member is above the upper surface of the toner in the toner container 410 (FIG. 5A), it is transmitted from the ultrasonic transmitter 450 of the ultrasonic sensor 470 and reflected by the ultrasonic receiver 460. The distance until the ultrasonic wave is received will measure the stirring member position. Therefore, the toner container 410 is provided with a position detection encoder 480 and a photo sensor 490 outside the side surface of the toner container 410 at the end of the rotating shaft of the stirring member 440 (FIG. 5B) so that the blade position of the stirring member 440 can be detected. It has a special mechanism. This stirring member positioning detection mechanism is controlled by the CPU 1 so that the blade position of the stirring member 440 stops at a position lower than the upper surface of the toner when the ultrasonic sensor 470 measures the remaining amount of toner.

In the toner container 410, a horn 430 having a small mouth portion and a large mouth portion is provided in order to efficiently transmit and receive ultrasonic waves, and the horn mouth portion is disposed on the ultrasonic sensor side. Yes. The peripheral surface of the horn 430 is covered with a sound absorbing material 510 made of foamed rubber or the like, and this sound absorbing material plays a role of reducing detection of extra reflected waves (disturbance waves) and stabilizing detection accuracy. (See Fig. 5 (c))
The ultrasonic sensor is installed on the upper surface where the toner surface is stable as shown in FIG. 6a. When attached to the position of FIG. 6b, the reflected wave does not enter the ultrasonic wave receiving unit 460 of the sensor.

  The ultrasonic sensor 470 is a hermetically sealed sensor that does not contain powder of toner or the like. Further, the transmitter surface and the receiver surface are prevented from adhering toner due to the self-vibration of the sensor.

  Furthermore, when the ultrasonic wave transmission unit 450 of the ultrasonic sensor 470 stops the ultrasonic wave transmission, the vibration of the vibrator self as shown in FIG. Although this phenomenon is referred to as sensor reverberation time, in order to reduce the influence of sensor reverberation time, the waveform processing control unit 500 has control means that makes the reflected wave arrival time between the sensor surface and the toner surface be equal to or longer than the sensor reverberation time. ing.

The toner container shown in FIG. 2 was mounted on the image forming apparatus shown in FIG. 1 and the toner amount detection accuracy was measured.
The outline of the configuration used in this device is: Ultrasonic sensor: Murata Manufacturing Input voltage: DC12V
Transmission pulse transmission frequency: 220 ± 20 kHz
10 pulses of rectangular wave every 1.2 msec Transmission threshold: 2V
Average value: Average value when measured 5 times Toner: Volume average particle diameter 4.5 μm Polymerized toner (black)
Toner container capacity: 1475 cm ³
Toner amount: 1200g
Distance from sensor to toner top surface: MAX100mm, MIN20mm
It is.

  FIG. 8 shows the relationship between the arrival time of the reflected ultrasonic wave and the distance between the sensor and the toner upper surface as a theoretical calculation value and an actual measurement value. In FIG. 8, it can be seen that the calculated value and the actually measured value are substantially the same.

  From the above, the toner amount detecting means using the ultrasonic sensor can detect the toner amount linearly with a smaller number of sensors than the conventional detecting means using the piezoelectric element. Further, since a surface cleaning member for removing toner adhesion on the sensor surface such as a piezo element is unnecessary, the amount of toner can be detected stably without a kamakura phenomenon.

1 is a cross-sectional view of an image forming apparatus as an example of an image forming method of the present invention. FIG. 2A is a sectional view of the developing means and the toner replenishing means. FIG. 2B is a perspective view of the toner container portion. 6 is a timing chart showing a process from reception of a reflected wave returned when an ultrasonic wave hits an upper surface of a toner until waveform processing is performed by a time measuring unit. 3 is a block diagram schematically illustrating toner amount detection using an ultrasonic sensor. FIG. FIG. 5A is a diagram illustrating a state where the stirring member in the toner container is above the upper surface of the toner. FIG. 5B is a perspective view provided with a position detection encoder and a photosensor for detecting the rotation stop of the stirring member. It is a figure which shows that the attachment position of an ultrasonic sensor is installed in the upper surface of the location where the toner surface is stable. It is a figure which shows a vibrator | oscillator self-oscillation when an ultrasonic transmission is stopped. It is a figure which shows the relationship between ultrasonic reflected wave arrival time and the distance between sensor-toner upper surfaces.

Explanation of symbols

DESCRIPTION OF SYMBOLS 50 Photosensitive drum 52 Charging device 40 Toner replenishing means 53 Image exposure device 54 Developing means 59 Separating electrode 60 Fixing device 62 Cleaning means 410 Toner container 420 Toner discharging means 430 Horn 440 Toner stirring member 450 Ultrasonic transmission part 460 Ultrasonic wave receiving part 470 Ultrasonic sensor 480 Position detection encoder 490 Photo sensor 500 Waveform processing control unit 510 Sound absorbing material P Recording paper T1 Toner density detection means T2 Toner amount detection means

Claims (5)

An image forming apparatus comprising: a developing unit that develops an electrostatic image formed on an image carrier with toner; a toner container that supplies toner to the developing unit; and a toner amount detection unit that detects the amount of toner in the toner container. In
The toner amount detection means comprises an ultrasonic sensor and a time measurement means,
The ultrasonic sensor has an ultrasonic transmitter and an ultrasonic receiver, the ultrasonic transmitter transmits toward the upper surface of the toner in the toner container, and the ultrasonic receiver reflects from the upper surface of the toner. Configured to receive the ultrasonic waves
The time measuring means measures the time until an ultrasonic wave is transmitted from the ultrasonic wave transmitting unit and the ultrasonic wave reflected by the ultrasonic wave receiving unit is received.
An image forming apparatus. The toner container according to claim 1, further comprising a toner stirring member that rotates in the toner container, and a control unit that controls the stirring member so that a rotation stop position of the stirring member is lower than the upper surface of the toner. Image forming apparatus. The horn having a small mouth portion and a large mouth portion is provided between the ultrasonic sensor and the toner upper surface portion, and the small mouth portion of the horn is disposed on the ultrasonic sensor side. The image forming apparatus described. The image forming apparatus according to claim 3, wherein a member of the horn is covered with a sound absorbing material. Control means for controlling the time from when the ultrasonic wave is transmitted from the ultrasonic wave transmission unit until the ultrasonic wave reflected by the ultrasonic wave reception unit is received to be longer than the reverberation time of the ultrasonic sensor. The image forming apparatus according to claim 1, further comprising: an image forming apparatus according to claim 1;

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