JP5124986B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile using an electrophotographic technique.

  A developing device in an electrophotographic image forming apparatus transports toner by a magnetic brush formed on a rotating sleeve and develops an electrostatic latent image formed on an image carrier as a toner image. Widely known.

  In the developing process by such a developing device, floating toner that is not held on either the surface of the image carrier or the magnetic brush is generated. This floating toner falls downward from between the image carrier and the outer wall of the developing tank of the developing device. Still further, since air is drawn into the developing tank by the rotating magnetic brush from the gap formed between the image carrier and the outer wall of the developing tank, the air pressure inside the developing tank rises, and the developing tank slightly increases. The internal toner may be scattered to the outside through a simple opening or gap. As described above, the toner dropped or scattered outside the developing tank adheres to various sensors inside the image forming apparatus, and may cause malfunction.

  In order to cope with such problems, a slit-like opening having a breathable sheet attached to the bottom wall of the developing device is provided, and the air inside the developing tank is blown from the opening through the exhaust passage by a blower. There is a proposal of exhaust means for suction (see, for example, Patent Document 1). In addition, an air suction port is provided in the bottom wall of the developing device adjacent to the image carrier to collect the scattered toner, and an exhaust unit that performs suction control to change the suction air speed between the developed state and the non-developed state. There is also a proposal (for example, Patent Document 2).

  As described in the above proposal, a toner filter that collects toner is provided in the exhaust path that guides air and toner from the suction port to the exhaust port so that the sucked toner is not discharged outside the apparatus. ing. As a result, the toner gradually adheres to the toner filter, and the suction by the exhaust fan rotating at a constant speed reduces the amount of air sucked with the progress of the dirt on the toner filter.

  In order to prevent such a phenomenon, a duct is provided at the end of a plurality of exhaust passages composed of an exhaust duct and an exhaust fan to guide the air sent from these exhaust passages to the exhaust outlet. There is also a proposal of an exhaust means for controlling the air pressure so as to be maintained at a predetermined value or less so that the exhaust amount of air does not become a predetermined value or less (see, for example, Patent Document 3).

  However, in such a configuration, in order not to reduce the exhaust efficiency of the exhaust fan, it is necessary to reduce the air resistance (exhaust impedance) of the duct from the exhaust fan to the exhaust port as much as possible. In order to measure the air pressure in the duct, the condition that the change in the air pressure should appear as large as possible is incompatible with each other. Therefore, the change in the air pressure in the duct due to the progress of the dirt on the toner filter is inevitably small. It becomes a thing. As a result, there arises a problem that it is difficult to accurately grasp the degree of progress of toner filter contamination.

Therefore, the replacement timing of the toner filter provided in the exhaust passage or the exhaust passage of the air containing toner, called the exhaust duct, described above is the cumulative number of copies output by the image forming apparatus or the blackening rate of the copy and the output. In many cases, it is determined based on the accumulated number of sheets. Since such a technical means does not directly detect the degree of progress of the dirt on the toner filter, the force for sucking the floating toner in the exhaust means may be different from that assumed. Over and under problems will occur. In addition, there may be a problem that the replacement time of the toner filter becomes inappropriate.
JP-A-5-53425 JP 2000-47483 A JP 2004-354663 A

  The present invention has been made in view of the above-described situation. An air pressure sensor is arranged at a position where a change in air pressure in the exhaust passage appears greatly due to contamination of the toner filter, and the exhaust fan is based on the obtained measurement value. It is an object of the present invention to provide an image forming apparatus having exhaust means that can maintain a constant amount of air flowing in the exhaust passage by controlling the rotation speed of the exhaust passage and that accurately indicates the replacement timing of the toner filter.

The above-mentioned subject is achieved by realizing the following invention.
1. An image forming apparatus including a developing device for developing toner on a latent image formed on an image carrier,
An exhaust duct having a suction port below or above a region where the image carrier and the developing device face each other, and guiding the air sucked from the suction port to the outside of the device;
An exhaust fan provided at an exhaust port of the exhaust duct;
A toner filter provided in the exhaust duct;
An atmospheric pressure sensor for measuring an atmospheric pressure in an exhaust duct between the exhaust fan and the toner filter;
An image forming apparatus comprising: a control unit that controls a rotation speed of the exhaust fan based on a measurement value obtained by the atmospheric pressure sensor.
2. The control means includes
Referring to an exhaust characteristic curve showing a relationship between the rotational speed of the exhaust fan and the atmospheric pressure measured by the atmospheric pressure sensor, the rotational speed of the exhaust fan is determined so that the exhaust amount is constant 1 The image forming apparatus described in the item.
3. The control means includes
When the toner filter is newly replaced, a toner filter characteristic curve indicating a relationship between the rotation speed of the exhaust fan and the atmospheric pressure measured by the atmospheric pressure sensor is obtained, and the exhaust characteristic curve is corrected from the toner filter characteristic curve. 3. The image forming apparatus according to item 2, wherein
4). A shutter for blocking the flow of air in the exhaust duct is provided on the front or rear surface of the toner filter,
The control means includes
When the shutter is closed, an exhaust fan characteristic curve indicating a relationship between the rotation speed of the exhaust fan and the atmospheric pressure measured by the atmospheric pressure sensor is obtained, and the exhaust characteristic curve is corrected from the exhaust fan characteristic curve. Item 4. The image forming apparatus according to Item 2 or 3,
5. The control means includes
Item 5. The instruction information for prompting replacement of the toner filter is output when a value measured by the pressure sensor exceeds a preset value with the shutter opened. The image forming apparatus according to claim 1.

  According to the present invention, an exhaust unit is realized in which the optimum air volume or air speed is maintained to suck the floating toner discharged from the developing device, so that excessive exhaust and excessive suction of toner by the exhaust unit are prevented. As a result, both an unnecessary increase in toner consumption and toner scattering inside the image forming apparatus are prevented.

  In addition, it is possible to accurately indicate the replacement time of the toner filter that collects the sucked toner.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a conceptual diagram of the image forming apparatus G.

  The image forming apparatus G is a digital image forming apparatus having a function of a copying machine, a facsimile machine, and a printer, commonly called a multifunction machine.

  An automatic document feeder F is provided in the upper part of the image forming apparatus main body G, and below that there are an image reading means 1, an image writing means 2, an image forming means 3, an input operation means 4, a paper feeding means 5, and a paper discharge. A re-feeding unit 6, a fixing device 7, a control unit C1, and the like are arranged.

  The automatic document feeder F feeds a document placed on the document table 11 to the document transport unit 13 one by one by the document peeling unit 12, and the document transport unit 13 transports the sent document to the document discharge unit 14. Then, the document discharge means 14 discharges the sent document to the document discharge table 15. The document image is read by a slit 21 provided in the document conveyance path, which is a document image reading position of the image reading unit 1.

  When reading images on both sides of the document, the document which has been read on the first surface is reversed by the document reversing means 16 having a pair of rollers, and is sent again to the document conveying means 13 to re-feed the second surface. Reading is done. The document that has been read is discharged to the document discharge table 15.

  The image reading means 1 is a means for reading a document image to obtain image data. The document image irradiated with light by the lamp 231 at the position of the slit 21 is a first mirror unit 23 and a second mirror unit 24. And an imaging lens 25 to form an image on the image sensor 26 which is a linear CCD. The signal output from the image pickup device 26 is A / D converted by the image processing unit of the control means C1, subjected to processing such as shading correction and image compression, and stored as image data in the memory M1.

  The image writing means 2 is an image carrier 31 that is rotated by being uniformly charged by a charging means 32 by a laser beam and a polygon mirror based on image data that has been called from the memory M1 and subjected to predetermined image processing. The electrostatic latent image corresponding to the original image is formed on the surface of the image carrier 31 by scanning the surface.

  The electrostatic latent image is reversely developed by the developing device 34 having the magnetic brush 342 of the image forming unit 3, and a toner image is formed on the image carrier 31.

  Corresponding to the timing of toner image formation, the recording paper P is fed from the manual paper feeding means 55 or the paper feeding means 5 having a cassette or tray for storing the recording paper P, and is transported by the transport roller 56. Then, the timing roller 39 is synchronized with the toner image formed on the image carrier and is sent to the transfer area.

  In the transfer area, the toner image formed on the surface of the image carrier 31 is transferred to the recording paper P charged to the opposite polarity by the transfer means 35.

  The recording paper P carrying the toner image is separated from the surface of the image carrier 31 by the action of the separation / elimination means 36 and sent to the fixing device 7.

  In the fixing device 7, the recording paper P carrying the toner image is conveyed while being heated and pressurized by the heating roller 71 as the rotating body 1 and the pressure roller 72 as the rotating body 2, and the toner image is transferred to the recording paper. The toner is fixed to P and discharged to a paper discharge tray 64 by a discharge roller 63.

  When the recording paper P is turned upside down and discharged onto the paper discharge tray 64, the recording paper P is guided to the paper discharge refeeding means 6 by the switching guide 62, and the recording paper P is switched back to discharge rollers. Send to 63.

  Further, when forming an image on both sides of the recording paper P, the recording paper P that has been fixed on the first surface is guided to the paper discharge refeeding means 6 by the switching guide 62 and reversed by the reversing unit 65. After that, the sheet is fed to a conveyance path 66 for paper feeding and used for image formation on the second surface.

  On the other hand, the surface of the image carrier 31 that has finished transferring the toner image onto the recording paper P is prepared for the next image formation after the residual toner is removed by the cleaning means 37.

  The input operation means 4 is a touch panel and is a known means having both an input operation function and a display function.

  FIG. 2 is a block diagram illustrating a control relationship of the image forming apparatus G.

  The control means C1 is a computer system including a CPU, a memory M1, and an arithmetic unit, an I / O port, a communication interface, a drive circuit, etc. (not shown). They are connected by corresponding I / O ports, communication interfaces, and drive circuits.

  Further, the control by the control means C1 is performed by executing a predetermined program stored in the memory M1.

  The automatic document feeder F is also smaller in scale than the control means C1, but is provided with similar control means centered on the CPU, and is connected to the control means C1 by the communication means R2.

  Further, the control means C1 can exchange information with a plurality of information processing apparatuses via the communication means R1.

  FIG. 3 is a conceptual diagram of the exhaust means 300.

  As shown in the figure, the exhaust unit 300 has a suction port 301 below a region where the image carrier 31 and the magnetic brush 342 of the developing device 34 face each other, and sucks air and toner from the suction port 301 to the exhaust port of the apparatus. Exhaust ducts 302, 303, 304 led to 321, an exhaust fan 310 that sucks air from the suction port 301 and exhausts it to the outside of the apparatus, and prevents floating toner sucked together with the air from being discharged outside the apparatus. The toner filter 311, a shutter 312 that blocks the flow of air in the exhaust ducts 302 and 303, and an air pressure sensor PS that detects the air pressure in the exhaust duct 304 between the toner filter 311 and the exhaust fan 310. . The suction port 301 may be provided above the developing device 34 in some cases.

  The floating toner sucked together with air from the suction port 301 is collected by the toner filter 311, and the amount of collected toner (referred to as collected toner amount) increases in proportion to the processing amount of the image forming apparatus G.

  As the amount of collected toner increases, the air resistance (exhaust impedance) of the air ducts 302, 303, and 303, which are air flow paths, increases. If the exhaust fan 310 continues to rotate at a constant speed, it gradually increases. As a result, the amount of air sucked from the suction port 301 is reduced.

  In order to steadily take in the floating toner released outside the developing tank 341 from the suction port 301 without sucking toner more than necessary, the amount of air sucked from the suction port 301 within a unit time, in other words, For example, since it is desirable that the flow velocity of air sucked from the suction port 301 is constant, it is necessary to make the above-described change as small as possible. That is, it is necessary to increase the exhaust capacity by increasing the rotational speed of the exhaust fan 310 and increasing the exhaust capacity as the amount of toner collected by the toner filter 311 increases.

  The present invention detects a pressure in the air duct 304 that changes with an increase in the amount of collected toner by the pressure sensor PS, and stores a relationship between a pressure obtained by an experiment in advance and a rotational speed of the exhaust fan 310; Alternatively, a constant displacement is maintained by controlling the rotational speed with reference to the equation.

  FIG. 4 is a diagram showing the relationship between the atmospheric pressure (Pa) in the air duct 304 and the rotational speed (rpm) of the exhaust fan 310 when the exhaust amount of the exhaust means 300 is kept constant.

  A characteristic curve a (referred to as an exhaust characteristic curve) in FIG. 4 indicates that the load impedance of the exhaust fan 310 increases as the amount of toner collected by the toner filter 311 increases, and the exhaust amount is kept constant. Indicates that the rotational speed must be increased.

  For example, when the exhaust fan 310 initially rotates at the rotation speed R1 and the air pressure in the air duct 304 is P1, the rotation speed of the exhaust fan 310 reaches R1 due to an increase in the amount of toner collected by the toner filter 311. If maintained, the air pressure in the air duct 304 has dropped to P2. Therefore, in order to maintain the initial exhaust amount, it is required from the characteristic curve that the rotational speed of the exhaust fan 310 needs to be increased to R2.

  In addition, the atmospheric pressure in the figure is expressed with reference to the atmospheric pressure at the time of measurement (zero position).

  FIG. 5 is a diagram showing the relationship (toner filter characteristic curve, exhaust fan characteristic curve) between the air pressure in the air duct 304 and the rotation speed of the exhaust fan 310 when the shutter 312 of the exhaust means 300 is opened and closed.

  A shutter 312 is provided between the air duct 302 and the air duct 303 to block the flow of air in the duct. Normally, the shutter 312 is in an open state. When the rotational speed of the exhaust fan 310 is increased, the air pressure in the air duct 304 gradually decreases as indicated by the characteristic curve b1 (toner filter characteristic curve), and the atmospheric pressure converges to a constant value PP.

  A characteristic curve c1 (exhaust fan characteristic curve) in FIG. 5 is obtained when the shutter 312 is in a closed state.

  When the shutter is closed and the rotational speed of the exhaust fan 310 is increased, the air pressure in the air duct 304 rapidly decreases as shown by the characteristic curve c1, and the air pressure is converged to a constant value PP to be in an equilibrium state. Become.

  The characteristic curves b1 and c1 shown in the figure are not always the same. The former is due to variations in air resistance (exhaust impedance) for each toner filter. For example, the latter is different for each exhaust fan as shown by the characteristic curve b2. Depending on the variation in the exhaust capacity, the characteristic curve c2 may be obtained, for example.

  If the exhaust characteristic curve shown in FIG. 4 is obtained by the toner filter that obtains the characteristic curve b1 in FIG. 5 and the exhaust fan that obtains the characteristic curve c1, the toner filter or the exhaust fan is replaced with a new one. When the new characteristic curve obtained corresponding to each is, for example, b2 or c2, based on the difference between them, the toner filter for obtaining the stored characteristic curve b1, and the characteristic curve c1 The exhaust characteristic curve obtained by the exhaust fan that obtains is corrected.

  When toner is collected in the toner filter 311, the characteristic curve of the toner filter moves in the direction of the arrow d, for example, from b1 to b2.

  FIG. 6 is a flowchart showing a flow of processing for obtaining the exhaust fan characteristic curve indicating the relationship between the atmospheric pressure sensor PS and the rotational speed of the exhaust fan 310 by closing the shutter 312.

  When the exhaust fan 310 is first attached or replaced with a new exhaust fan 310 (step S1: Y), the shutter 312 is closed (step S2), and when the rotational speed of the exhaust fan 310 is increased, a short time The value of the atmospheric pressure sensor is close to a certain value PP. During this time, exhaust fan characteristic curves as exemplified in c1 and c2 of FIG. 5 are created from the rotational speed of the exhaust fan 310 and the measured value by the atmospheric pressure sensor PS. The created exhaust fan characteristic curve is stored in the memory M1 in a table format (step S4). Note that the exhaust fan characteristic curve may be expressed and stored instead of a table format.

  A new exhaust characteristic curve in which a difference in the exhaust fan characteristic curve is corrected is obtained from the exhaust fan characteristic curve and an exhaust characteristic curve stored in the memory M1 in advance on the assumption of a predetermined exhaust fan characteristic curve (step) S5). The obtained new exhaust characteristic curve is stored in the memory M1 in place of the previous exhaust characteristic curve.

  When the processing described above is completed, the shutter 312 is opened (step S6), and the routine is exited.

  FIG. 7 is a flowchart showing a flow of processing for obtaining a toner filter characteristic curve indicating the relationship between the atmospheric pressure sensor PS and the rotation speed of the exhaust fan 310 when the toner filter 311 is replaced.

  When the toner filter 311 is first attached or replaced with a new toner filter 311 (step S11: Y), the shutter 312 is opened (step S12), and the rotational speed of the exhaust fan 310 is increased. A toner filter characteristic curve as illustrated in b1 and b2 of FIG. 5 is created from the rotational speed of the exhaust fan 310 and the measured value by the atmospheric pressure sensor PS. The created toner filter characteristic curve is stored in the memory M1 in a table format (step S14). Note that the toner filter characteristic curve may also be stored in the form of an expression instead of a table format.

  A new exhaust characteristic curve in which a difference in the toner filter characteristic curve is corrected is obtained from the toner filter characteristic curve and an exhaust characteristic curve stored in the memory M1 in advance on the assumption of a predetermined toner filter characteristic curve (step) S15). The obtained new exhaust characteristic curve is stored in the memory M1 in place of the previous exhaust characteristic curve, and the routine ends.

  FIG. 8 is a flowchart showing the flow of control for determining the rotational speed of the exhaust fan 310 with reference to the exhaust characteristic curve.

  When the image forming apparatus G is operated, the exhaust fan 310 starts rotating (step S20), the timer TM that determines the measurement period of the atmospheric pressure sensor PS is once reset (step S21), and time measurement is started (step S22). When the value T of the timer TM reaches a preset value TT (step S23: Y), the atmospheric pressure is measured by the atmospheric pressure sensor PS (step S24).

  When the measured value AP is lower than the preset value PP (step S25: N), referring to the exhaust characteristic curve (step S26), the rotational speed necessary to maintain a predetermined exhaust amount. Is determined (step S27), and the process returns to step 21 to perform the next measurement again.

  If the measured value AP is equal to or greater than the preset value PP (step S25: Y), it is determined that the amount of toner collected by the toner filter 311 exceeds a predetermined amount, and the toner A display prompting the replacement of the filter is output to the input operation means 4, or the operation of the apparatus is stopped (step S28), and the routine is exited.

  As described above, even when there is a change in air resistance of the exhaust passage due to a change in the amount of toner collected by the toner filter, a constant amount of air is always sucked, that is, floating toner is sucked at a constant flow rate at the suction port. At least one of exhaust means that can be performed, exhaust means that can correct the variation in the exhaust capacity of the exhaust fan, and can keep the exhaust amount constant, or that can appropriately detect the replacement timing of the toner filter. An image forming apparatus is realized.

1 is a conceptual diagram of an image forming apparatus. 2 is a block diagram illustrating a control relationship of the image forming apparatus. FIG. It is a conceptual diagram of an exhaust means. It is a figure which shows an exhaust characteristic curve. It is a figure which shows the relationship (toner filter characteristic curve, exhaust fan characteristic curve) of the atmospheric pressure and the rotational speed of an exhaust fan when a shutter is opened and closed. It is a flowchart which shows the flow of the process which obtains an exhaust fan characteristic curve. 6 is a flowchart illustrating a flow of processing for obtaining a toner filter characteristic curve. It is a flowchart which shows the flow of control which determines the rotational speed of an exhaust fan.

Explanation of symbols

301 Suction Ports 302, 303, 304 Exhaust Duct 310 Exhaust Fan 311 Toner Filter 321 Exhaust Port 34 Developing Device 341 Developing Tank 342 Magnetic Brush G Image Forming Device C1 Control Unit M1 Memory PS Pressure Sensor

Claims (5)

An image forming apparatus including a developing device for developing toner on a latent image formed on an image carrier,
An exhaust duct having a suction port below or above a region where the image carrier and the developing device face each other, and guiding the air sucked from the suction port to the outside of the device;
An exhaust fan provided at an exhaust port of the exhaust duct;
A toner filter provided in the exhaust duct;
An atmospheric pressure sensor for measuring an atmospheric pressure in an exhaust duct between the exhaust fan and the toner filter;
An image forming apparatus comprising: a control unit that controls a rotation speed of the exhaust fan based on a measurement value obtained by the atmospheric pressure sensor. The control means includes
The rotational speed of the exhaust fan is determined so that the exhaust amount becomes constant with reference to an exhaust characteristic curve showing a relationship between the rotational speed of the exhaust fan and the atmospheric pressure measured by the atmospheric pressure sensor. Item 2. The image forming apparatus according to Item 1. The control means includes
When the toner filter is newly replaced, a toner filter characteristic curve indicating a relationship between the rotation speed of the exhaust fan and the atmospheric pressure measured by the atmospheric pressure sensor is obtained, and the exhaust characteristic curve is corrected from the toner filter characteristic curve. The image forming apparatus according to claim 2. A shutter for blocking the flow of air in the exhaust duct is provided on the front or rear surface of the toner filter,
The control means includes
When the shutter is closed, an exhaust fan characteristic curve indicating a relationship between the rotation speed of the exhaust fan and the atmospheric pressure measured by the atmospheric pressure sensor is obtained, and the exhaust characteristic curve is corrected from the exhaust fan characteristic curve. The image forming apparatus according to claim 2, wherein the image forming apparatus is an image forming apparatus. The control means includes
5. Instruction information for prompting replacement of a toner filter is output when a value measured by the atmospheric pressure sensor exceeds a preset value in a state where the shutter is opened. The image forming apparatus according to any one of the above.

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