JP5287296B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus using an electrophotographic process, and more particularly to an image forming apparatus provided with a toner detecting device capable of detecting a remaining amount of toner.

  Conventionally, in an image forming apparatus using an electrophotographic process such as a copying machine, a printer, and a facsimile machine, a photosensitive member is uniformly charged in advance and exposed on the photosensitive member to form an electrostatic latent image. The electrostatic latent image is developed with toner supplied from a developing device, and the visualized toner image is moved to a transfer roller by applying a voltage to a transfer roller to be transferred and fixed on a recording medium.

  First, before describing the toner detection apparatus, the main configuration of the image forming apparatus as a premise will be described with reference to FIGS. The image forming apparatus of the present invention only needs to form an image by an electrophotographic process. A facsimile is described as an image forming apparatus for monochrome printing, and a tandem type color image forming apparatus is simply used as an image forming apparatus for color printing. Will be explained.

  In the facsimile apparatus, when receiving a facsimile or printing a copy, the recording paper is conveyed through the first recording paper path, and image formation is performed by the image forming unit and the fixing device. Further, at the time of facsimile transmission or image reading, the original is conveyed through the second recording paper path, and the image is read.

  Therefore, a facsimile apparatus as an image forming apparatus will be described with reference to the structural diagram of the conventional image forming apparatus in FIG. The recording paper is picked up one by one from the paper supply tray 101 by the paper supply roller 102 along the recording paper path in FIG. This recording sheet is sent to the image forming unit 104 by the conveyance roller 103.

  The image forming unit 104 is provided with a photosensitive drum 105 that rotates at a constant speed, and the surface thereof is sequentially and uniformly charged by a charger 106 such as a scorotron charger. The charged surface is scanned by irradiating a laser beam from an LSU (Laser Scanning Unit) 107 to form an electrostatic latent image, and the electrostatic latent image is developed. The laser light from the LSU 107 forms an electrostatic latent image by neutralizing the charge at the portion irradiated with the light. Each part is arranged around the photosensitive drum 105 so that this process can be performed with rotation.

  Now, the image forming unit 104 is provided with a developing roller 108, and a toner such as a one-component developer is attached to the surface of the photosensitive drum 105. The toner is accommodated in a toner container 114 provided near the developing roller 108, conveyed while being stirred by the stirring paddle 112, and supplied to the developing roller 108 by the supply roller 113. The amount of toner is controlled by a doctor blade. The stirring paddle 112 is formed to rotate in conjunction with the developing roller 108 by a gear mechanism (not shown).

  The electrostatic latent image formed on the photosensitive drum 105 by the laser beam is visualized by the toner adhering to the developing roller 108, and a DC voltage is applied to the transfer roller 109 provided corresponding to the photosensitive drum 105. By applying the toner image, the toner image is transferred onto the recording paper conveyed between them. The recording paper on which the toner image is transferred is conveyed along the recording paper path.

  The toner image formed on the recording paper is fixed by the fixing roller 110. The recording paper on which the toner image is adhered is heated and fixed by the fixing roller 110 while being conveyed along the recording paper path. The fixing roller 110 is provided with a heating element such as a halogen lamp. After fixing, the recording paper is discharged by a paper discharge roller 111.

  Next, a tandem type color image forming apparatus will be described based on the structural diagram of the conventional image forming apparatus in FIG. There are only four color process units of yellow (Y), magenta (M), cyan (C), and black (K), and the basic structure is the same as that of a facsimile. An image forming unit that forms an image on recording paper through each process of charging, exposure, development, transfer, and fixing is provided. In this image forming unit, the recording paper contained in the paper feeding cassette is fed from the paper feeding cassette. It is conveyed through a recording paper path toward the image forming unit. The recording paper on which a required image is formed by the image forming unit is discharged from the image forming unit to the paper discharge unit through the next recording paper pass.

  The image forming unit includes a four-color image forming unit 121 that forms an image of each color component of yellow (Y), magenta (M), cyan (C), and black (K), and each image forming unit 121 in each image forming unit 121. It has an LSU 122 that scans the surface of the photosensitive drum with laser light for exposure, and an intermediate transfer belt 123 on which the toner images of the respective colors formed on the photosensitive drums in the image forming sections 121 are sequentially transferred. The photosensitive drums of the respective colors have a tandem structure in which the photosensitive drums are arranged along the intermediate transfer belt 123.

  In each image forming unit 121, the surface of each photoconductive drum uniformly charged by each charger is scanned with laser light from the LSU 122 to form an electrostatic latent image. The electrostatic latent image on each photoconductor drum is developed with each color toner supplied from each developing device, and is formed on each photoconductor drum as a toner image for each color component. There are four colors and only the intermediate transfer belt 123 is provided, which is substantially the same as the facsimile image forming unit 104 described above. The intermediate transfer belt 123 is stretched around a driving roller and a driven roller. Inside the intermediate transfer belt 123, the toner image on each photosensitive drum is transferred to the intermediate transfer belt 123 for each color. A primary transfer roller 124 is provided. A secondary transfer roller 125 is disposed at one end of the intermediate transfer belt to transfer the toner image formed on the intermediate transfer belt onto a recording sheet.

  The recording paper on which the toner image has been transferred by the secondary transfer roller 125 is conveyed to a fixing device, and a process for fixing the toner image on the recording paper by heat and pressure is performed. Thereafter, the recording paper passes through the recording paper path and is discharged onto the paper discharge unit by the paper discharge roller.

  Now, a toner detection device provided in a conventional image forming apparatus will be described (for example, see Patent Document 1). As shown in FIG. 15 as a configuration diagram of a conventional toner detection device, a permanent magnet 132 that attracts the detection body 131 to the stirring paddle 130 with a predetermined force is provided. A first operation state in which the detection body 131 is attracted by the permanent magnet 132 and rotates integrally with one stirring blade when the remaining amount of toner in the toner container is small as the stirring shaft rotates, and the toner When the remaining amount is large, the detection body 131 is separated from the permanent magnet 132 by the resistance of the toner, pushed up to the uppermost point by the other stirring blade not provided with the permanent magnet 132, and lowered by its own weight. It is comprised so that it can take. Thus, the magnetic permeability sensor 133 detects the number of magnetic field changes that occur in the first and second operating states of the detector 131.

Further, although not shown as another toner detection device, the present applicant has also proposed detection of the remaining amount of toner using a Hall element using a sensor agitation paddle and a free paddle (see Patent Document 2). The Hall element converts a magnetic field generated by a magnet provided in a free paddle or a magnetic field generated by a current into an electric signal and outputs the electric signal. The motion of the free paddle corresponds to the motion in the second operating state of the detector in Patent Document 1, and the remaining amount is determined by the length of the pulse detected by the Hall element.
JP 2002-108086 A JP 2007-164032 A

  By the way, in the magnetic sensor, it is said that the Hall element has lower sensitivity than the anisotropic magnetoresistive element. The anisotropic magnetoresistive element is also referred to as an AMR (Ancientpic-Magneto-Resistance) sensor, and will be described below using the expression AMR sensor. This Hall element is not only low in sensitivity but also more expensive than an AMR sensor. In addition, the cost of the AMR sensor is stable and inexpensive regardless of the sensitivity. For this reason, the AMR sensor is very advantageous for the toner detection device, but there are some problems described below to use the AMR sensor, which has not been realized so far.

  The problem of this AMR sensor will be described below. The AMR sensor has a sensitivity range of about 0.8 mT to 2.2 mT even with a standard sensitivity element that is not an element for toner detection (special specification). It has a sensitivity exceeding. On the other hand, the sensitivity of the Hall element for toner detection (special specification) is about 11.3 mT, and that of a normal Hall element is about 20.0 mT. Therefore, when an attempt is made to replace the Hall element with an AMR sensor, the AMR sensor reacts sharply, resulting in a large variation in the remaining amount of toner, which cannot be used in the toner detection device.

  In addition, the Hall element has the property of detecting the magnetic flux in the direction perpendicular to the substrate. By simply bringing the Hall element and the magnet close to each other, the magnetic flux in the vertical direction is detected and a detection signal (ON) is output. Easy to use in design. On the other hand, the AMR sensor has a characteristic of detecting a magnetic flux in a lateral direction that intersects with the base in parallel (see FIGS. 6A and 6B described later). For this reason, when the magnet is positioned directly above the sensor, the magnetic force of the AMR sensor is magnetically balanced in the vertical direction, and the detection signal is turned off near the important detection target.

  Since the directions of the magnetic flux detected by the Hall element and the AMR sensor are different in this way, in addition to the difference between ON and OFF of the detection signal, another technical characteristic difference occurs. In other words, the Hall element has a characteristic of outputting only one pulse of the ON signal only when the magnet is positioned directly above the sensor, while the AMR sensor is OFF when the magnet is positioned directly above the sensor. Before and after this position, the ON signal has a characteristic of outputting two pulses once. An AMR sensor having such technical characteristics cannot detect a state in which the remaining amount of toner is extremely low.

  Since the Hall element has a low sensitivity, it is suitable for detecting the remaining amount at a position where the remaining amount is low. However, the AMR sensor is more sensitive than the Hall element, and detects the magnetic flux more than twice as fast. If the detection start timing is advanced, the toner detection time becomes longer. The variation in detection inevitably increases, and there is a problem that the remaining amount of toner increases even if the problem that the detection signal is OFF is omitted.

  In order to prevent this, a low-sensitivity AMR sensor may be used. However, low sensitivity products with a sensitivity range of 0.8 mT to 2.2 mT or more are not commercially available. There is no environment where low sensitivity products can be used. For that reason, the image forming apparatus is limited in height and cannot take a great distance in terms of structure, if the position of the sensor should be simply moved away. Although a software-compatible method is also conceivable, since toner detection also performs other processing such as new product detection when the developing device is replaced, all these control specifications need to be reviewed, and software processing at this time Is also very complex. Therefore, a method corresponding to software is not practical.

  Therefore, it has been difficult to replace the conventional Hall element with an AMR sensor with a simple approach. It has been difficult to employ the AMR sensor in the toner detection device due to such a problem. However, the AMR sensor has the attractiveness and advantage of lower cost and higher sensitivity than the Hall element, and has an advantageous characteristic over the Hall element in practical use.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus including an inexpensive and highly sensitive toner detection device using an anisotropic magnetoresistive element.

  An image forming apparatus according to the present invention includes a container that contains toner, a toner stirring member that is provided inside the container and rotates around a rotation shaft to stir the toner, and is rotatably provided with respect to the rotation shaft. A rotating member that is rotated by being pushed by the member, a magnetic member that is provided at the end opposite to the rotating shaft of the rotating member, an anisotropic magnetoresistive element that is provided at the bottom of the container and detects the magnetic member, And a detecting means for detecting the amount of toner based on a change in time for detecting the magnetic member by the anisotropic magnetoresistive element, and the rotating member that can rotate the anisotropic magnetoresistive element with respect to the rotation axis is suspended by its own weight. The most important feature is that the rotating member is disposed downstream of the position of the rotating member in the rotational direction of the rotating member.

  The image forming apparatus of the present invention has an advantage that an inexpensive and highly sensitive toner detecting device using an anisotropic magnetoresistive element can be realized, and manufacturing and assembly are facilitated.

  In the first embodiment of the present invention, a container for containing toner, a toner stirring member that is provided inside the container and rotates around a rotation shaft to stir the toner, and is provided rotatably with respect to the rotation shaft. A rotating member that is pushed by the stirring member and rotates; a magnetic member provided at an end opposite to the rotating shaft of the rotating member; and an anisotropic magnetoresistive element that is provided at a lower portion of the container and detects the magnetic member A detecting means for detecting the amount of toner based on a change in the time for detecting the magnetic member by the anisotropic magnetoresistive element, and the rotating member capable of rotating the anisotropic magnetoresistive element with respect to the rotation axis by its own weight. An image forming apparatus characterized in that the image forming apparatus is arranged on the downstream side in the rotational direction of the rotating member from directly below the position when the ink is suspended. With this configuration, inexpensive and highly sensitive toner detection using an anisotropic magnetoresistive element is provided. Device can be realized Both design and manufacturing, assembling becomes easy.

Toner with a second embodiment of the present invention includes a container for containing the toner, a toner stirring member for stirring the rotating toner around a rotation shaft arranged inside the container, is provided rotatably for rotating shaft A rotating member that is pushed by the stirring member and rotates; a magnetic member provided at an end opposite to the rotating shaft of the rotating member; and an anisotropic magnetoresistive element that is provided at a lower portion of the container and detects the magnetic member A detecting means for detecting the amount of toner based on a change in the time for detecting the magnetic member by the anisotropic magnetoresistive element, and the rotating member capable of rotating the anisotropic magnetoresistive element with respect to the rotation axis by its own weight. An image forming apparatus characterized in that the image forming apparatus is disposed downstream of the rotating member in the rotational direction of the rotating member and shifted in the axial direction of the rotating shaft from directly below the position of the suspended member. Low price and high sensitivity using The toner detection device is possible realization of the design and manufacturing, assembling becomes easy. The mounting position can be easily adjusted without being affected by the height of the image forming apparatus.

In the third embodiment of the present invention, a container that contains toner, a toner stirring member that is provided inside the container and that rotates around a rotation shaft and stirs the toner, and that is rotatably provided with respect to the rotation shaft are provided. A rotating member that is pushed by the stirring member and rotates; a magnetic member provided at an end opposite to the rotating shaft of the rotating member; and an anisotropic magnetoresistive element that is provided at a lower portion of the container and detects the magnetic member A detecting means for detecting the amount of toner based on a change in the time for detecting the magnetic member by the anisotropic magnetoresistive element, and the rotating member capable of rotating the anisotropic magnetoresistive element with respect to the rotation axis by its own weight. A distance that can be detected only between the first timing and the second timing of the cycle, only the magnetic flux on the rotational direction side of the magnetic member on the downstream side in the rotational direction of the rotating member from directly below the position when the shaft is suspended. Away from magnetic orbit An image forming apparatus characterized by the arranged by the arrangement, at low cost using an anisotropic magnetoresistive element it is possible realize a toner detection device with high sensitivity, design and manufacture, assembly becomes easy. Since the three-dimensional design is based on the trajectory, the anisotropic magnetoresistive element can be attached at an accurate position.

Embodiment 4 of the present invention, the first embodiment, 2 or is in a form dependent on 3, thin strong anisotropic magnetoresistive element provided between a pair of electrodes and the pair of electrodes An image forming apparatus comprising a magnetic metal, wherein the thin film ferromagnetic metal is disposed at a predetermined angle with respect to a magnetic flux direction of the magnetic member. This makes it possible to realize a low-cost and high-sensitivity toner detection device using the toner, and to facilitate manufacture and assembly.

Fifth embodiment of the present invention, the first and second embodiments, 3 or is in a form that is dependent on 4, sensing means toner remaining amount by the time of detecting the magnetic member is shorter than the predetermined time The image forming apparatus according to claim 1, wherein the image forming apparatus detects that there is a large amount of toner, and detects that the remaining amount of toner is low when the time is longer than a predetermined time. Thus, a highly sensitive toner detection device can be realized, and manufacture and assembly are facilitated.

(Embodiment 1)
Hereinafter, an image forming apparatus according to Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 is an enlarged configuration diagram of an image forming unit of an image forming apparatus according to Embodiment 1 of the present invention, FIG. 2 is an operation explanatory diagram when an AMR sensor is disposed below a paddle angle reference, and FIG. FIG. 2 is a main part control block diagram of the image forming apparatus according to the first embodiment. The configuration of the main part of the image forming apparatus using an electrophotographic process such as a copying machine, a printer, or a facsimile machine is as described in the description of the background art with reference to FIGS. 13 and 14, and is omitted here. However, FIGS. 13 and 14 are referred to in the first embodiment at the same time as FIG. 1 in order to describe the overall configuration of the image forming apparatus.

  As shown in FIG. 1, the image forming apparatus includes an image forming unit 1. The image forming unit 1 includes a photosensitive drum 2 on which an electrostatic latent image is formed. As the photosensitive drum 2 rotates, the charging unit sequentially charges the surface, the exposure unit forms an electrostatic latent image thereon, the development unit develops the electrostatic latent image, and the transfer unit records. Transfer to paper. Each part is arranged around the photosensitive drum 2 so that charging to transfer can be performed around the photosensitive drum 2.

  The first configuration of each part is a charger. In the first embodiment, the charger is a charger 3 such as a non-contact charging type scorotron charger that charges the photosensitive drum 2. An exposure unit is provided as a second configuration. Although not shown in FIG. 1, an LSU as shown in FIGS. 13 and 14 is provided. This LSU irradiates the peripheral surface of the photosensitive drum 2 with laser light to remove the charge, thereby forming an electrostatic latent image.

  In order to develop the photosensitive drum 2 in a state where the electrostatic latent image is formed, a developing unit is provided as a third configuration. The developing unit includes a developing roller 6 that adheres toner 5 of a one-component developer to the surface of the charged photosensitive drum 2. The toner 5 in the toner container 4 is conveyed while being stirred by the stirring paddle 7 and supplied to the developing roller 6 by the supply roller 8. The stirring paddle 7 has a stirring body for stirring at the tip, and is formed to rotate in conjunction with the developing roller 6 by a gear mechanism (not shown) (see, for example, FIG. 11A). The toner 5 is not limited to a one-component developer, and may be a two-component developer.

  As shown in FIGS. 1 and 2, the rotating shaft 7 a that rotates the stirring paddle 7 is provided with a free paddle 11 that rotates together with the stirring paddle 7. The free paddle 11 is rotatably supported on the rotating shaft 7a of the stirring paddle 7, and is pushed up to the top (uppermost point) by the contact of the stirring paddle 7, and descends from its position by its own weight. The free paddle 11 is subjected to the resistance of the toner 5 remaining at the dropping point, and the rotational speed is temporarily lowered, and the movement becomes slow in this vicinity. However, immediately after this, the stirring paddle 7 abuts from behind and gives a rotational force again, and pushes it up to the highest point via the lowest point.

  A magnet 9 is provided at the tip of the free paddle 11. As shown in FIG. 2, a magnetic sensor S is provided on the side surfaces of the circular orbits of the free paddle 11 and the stirring paddle 7. The magnetic sensor S according to the first embodiment is an AMR sensor 10 that is fixed to the bottom surface of the image forming apparatus via a mounting member 15. However, in FIG. 2, the magnetic sensor S is placed at the same position as the Hall element. Therefore, the magnetic sensor S is described not as an AMR sensor 10 but as a superordinate magnetic sensor S. The magnetic sensor S detects a magnet 9 that rotates within a predetermined detection range. However, when the magnetic sensor S is the AMR sensor 10, detection of the toner 5 is more difficult as the residual amount is smaller in the arrangement of FIG.

  Now, returning to FIG. 1, the description of the developing unit will be continued. A voltage is applied from the power source to the developing roller 6 in order to adhere the toner 5 to the surface of the charged photosensitive drum 2. This power supply applies an AC superimposed bias to the developing roller 6 with a DC voltage of about 200V. And in order to adjust the alternating voltage applied by superimposing, the control part 12 (refer FIG. 3) which can control the power supply controller 13 is provided. The control unit 12 is a function realizing unit including a processor and a memory storing a program. An AMR sensor 10 is connected to the control unit 12, and the control unit 12 is provided with detection means 12 a that detects the remaining amount of toner 5 based on a change in time for detecting magnetic flux based on the output from the AMR sensor 10. ing. The detection means 12 a is also a function realization means mounted on the control unit 12. As shown in FIG. 3, the control unit 12 displays the remaining amount of toner 5 such as no toner, toner LOW display, and ENTTY on the display unit 14 based on the detection result of the detection unit 12a.

  Subsequently, a transfer unit is provided as a fourth configuration. The transfer unit includes a transfer roller for transferring the developed toner 5 of the photosensitive drum 2 to a recording sheet. The transfer roller is positioned above the photosensitive drum 2 (see FIG. 13) and rotates while being in contact with the photosensitive drum 2. The recording paper is transferred between the transfer roller and the photosensitive drum 2 to be transferred.

  In order to fix the toner 5 of the transferred recording paper, the image forming apparatus is provided with a fixing roller (not shown in FIG. 1). By applying pressure to the recording paper while heating the recording paper transferred by the fixing roller, the toner 5 is fixed and discharged (see FIG. 13).

  Now, details of the remaining amount detection of the toner 5 performed in the above-described image forming apparatus will be described. FIG. 4A is a diagram for explaining the principle of residual detection when toner 5 is present by the magnetic sensor S in FIG. 4A, and FIG. Description will be made based on the principle explanatory diagram of the residual detection when there is not. Since the arrangement is different from that of the AMR sensor 10 of the first embodiment, it will be described here as a general magnetic sensor S such as a Hall element. However, the basic operation principle itself is the same in the AMR sensor 10 of the first embodiment. 4A shows the state of the stirring paddle 7, the free paddle 11, the magnet 9, and the magnetic sensor S when the toner 5 is in a large amount in the toner container. FIG. 4B shows the toner 5 in the toner container. The state of the stirring paddle 7, the free paddle 11, the magnet 9, and the magnetic sensor S in a small state is shown in FIG. Hereinafter, description will be made assuming that the magnetic sensor S is a Hall element.

  As shown in FIGS. 4A and 4B, the stirring paddle 7 rotates around the rotating shaft 7a at a predetermined rotational speed to stir the toner 5. The free paddle 11 is rotatably supported by the rotary shaft 7 a and rotates with the stirring paddle 7. That is, it is brought into contact with the stirring paddle 7 that rotates following the free paddle 11 and pushed up to the uppermost point, and descends by its own weight from the rotational speed of the stirring paddle 7 from that position. The free paddle 11 receives the resistance of the toner 5 at the falling point on the toner 5 and temporarily decreases in speed. However, the following stirring paddle 7 pushes from behind, gives a rotational force again, passes through the toner 5 and pushes it up to the uppermost point, and this operation is repeated. A magnet 9 is provided at the tip of the free paddle 11, and the magnet 9 moves along a circular orbit at the tip of the free paddle 11, and the magnetic field of the magnet 9 also moves.

  Therefore, if the detection range of the magnetic sensor S is matched with a very small set range that the toner 5 is to detect or is arranged so as to have a width larger than that, the toner-free state can be detected with high accuracy. That is, when there is almost no toner 5, as shown in FIG. 4B, there is no resistance of the toner 5, and the movement of the free paddle 11 is not stopped by the presence of the toner 5. Accordingly, when the free paddle 11 is lowered by its own weight in the absence of the toner 5, the time for which the free paddle 11 is located at the lowermost position (the position where the free paddle 11 is suspended by its own weight) becomes longer. This means that, in a state where the amount of toner is small, the time during which the free paddle 11 is in the detection range becomes longer in the time from when the free paddle 11 falls from the uppermost point and is pushed up to the stirring paddle 7. .

  However, as shown in FIG. 4A, when the toner 5 is sufficiently present, when the free paddle 11 falls due to its own weight, it falls onto the toner 5 and receives resistance. Thereby, the magnet 9 cannot reach the detection range of the magnetic sensor S. Accordingly, when the free paddle 11 is lowered by its own weight in the absence of the toner 5, the time for the free paddle 11 to be positioned at the lowest position is only the time for which the free paddle 11 is pushed by the stirring paddle 7 and passes through. The time during which the paddle 11 is located at the lowest end is shortened. This means that the time until the free paddle 11 falls from the uppermost point and is pushed up to the stirring paddle 7 is short when the amount of toner 5 is large and the time existing in the detection range is shortened. Based on the principle described above, the remaining amount of toner 5 can be detected using the free paddle 11, the magnetic sensor S, and the magnet 9.

  However, it should be noted that the general residual amount detection of the toner 5 using the magnetic sensor S and the magnet 9 is based on the following assumptions. That is, when the magnet 9 approaches, the magnetic field strength increases, and the magnetic sensor S outputs a detection signal in response thereto. Therefore, when the magnetic sensor S is a Hall element and the free paddle 11 is lowered by its own weight when the toner 5 is not present, the magnetic sensor S is disposed below the lowermost position (position where it is suspended by its own weight). If so, the remaining amount of the toner 5 can be detected based on the principle described above.

  However, in the case of the AMR sensor 10 in which the magnetic sensor S responds nonlinearly with respect to the distance to the magnet 9, when the magnet 9 rotates on the AMR sensor 10, a nonlinear response characteristic different from that of the Hall element is exhibited. Therefore, although the basic concept in the above principle can be used, it cannot be actually detected as it is. This is because in the AMR sensor 10, the detection signal of the magnet 9 is turned off when the free paddle 11 passes through the lowermost end.

  5A and 5B are explanatory views of the appearance of the AMR sensor and the effect of anisotropic magnetoresistance, FIG. 6A is an explanatory view showing the magnetic field detection direction of the Hall element, and FIG. 6B is the magnetic field detection direction of the AMR sensor. 7A is an explanatory diagram of the response characteristic of the Hall element, FIG. 7B is an explanatory diagram of the response characteristic of the AMR sensor, and FIG. 8 is a waveform of the output signal of the Hall element and the AMR sensor. In the figure, the waveform of the output signal when the magnet passes once by the Hall element and the AMR sensor is shown. FIG. 9 is an explanatory view of the arrangement of the toner detection device of the image forming apparatus according to the first embodiment of the present invention. FIG. 10A is a perspective view of the magnet track and the AMR sensor of the toner detection device of FIG. FIG. 10B is a front view of the toner detection device of FIG. FIG. 11A is a perspective view showing a state in which the image forming unit of the image forming apparatus according to Embodiment 1 of the present invention is taken out, and FIG. 11B is an explanatory view showing the amount of deviation of the AMR sensor.

  Here, the structure of the anisotropic magnetoresistive element (AMR sensor) and the effect of the anisotropic magnetoresistance will be described. An AMR sensor 10 shown in FIG. 5 includes a substrate 21 such as a Si or glass substrate, an alloy thin film 22 mainly formed of a ferromagnetic metal such as Ni or Fe, and an elongated belt-shaped thin film. 22 is composed of electrodes 23 and 24 provided at both ends. When a magnetic field in the x-axis direction shown in FIG. 5 is applied along the substrate 21, the resistance value of the thin film 22 facing the y-axis direction in which current flows changes. Accordingly, the output current value also changes. The AMR sensor 10 utilizes the effect of this anisotropic magnetoresistance. A Hall element utilizes the Hall effect.

  When the characteristics of the AMR sensor 10 and the Hall element are compared, there are significant differences as shown in FIGS. 6 (a) and 6 (b) and FIGS. 7 (a) and 7 (b). As shown in FIG. 6A, the Hall element detects a magnetic flux perpendicular to the element (z-axis direction), and the AMR sensor 10 is a thin film on the surface of the substrate 21 as shown in FIGS. Magnetic flux in the lateral direction (x-axis direction) is detected with respect to the longitudinal direction (y-axis direction) in which 22 films are formed. Accordingly, when the magnetic sensor S is a Hall element and is disposed at the position shown in FIG. 2, either the N pole or the S pole of the magnet 9 (for example, the N pole) approaches as shown in FIG. Then, the magnetic field strength gradually increases in inverse proportion to the square of the distance, and the magnetic field strength decreases as the distance increases. Then, a response having hysteresis as shown in FIG.

  However, when the magnetic sensor S is the AMR sensor 10 and is disposed at the position of FIG. 2, when one of the N poles and S poles of the magnet 9 (for example, the N pole) approaches the AMR sensor 10, Since the magnetic field lines of the magnet 9 draw a donut-shaped magnetic flux flow and flow in and out of the magnet 9 (see FIGS. 6 and 10A), when the magnet 9 approaches, it first approaches the side (rotation direction side). The AMR sensor 10 reacts to half the magnetic flux and outputs an ON signal. When the magnet 9 reaches the upper side of the AMR sensor 10, the detection signal becomes an OFF signal, and then when the remaining half of the magnetic flux approaches, the AMR sensor 10 reacts again and outputs an ON signal. The response of the AMR sensor 10 is a response having hysteresis as shown in FIG. Therefore, in the position of FIG. 2 where the AMR sensor 10 is most necessary for toner detection, the magnetic force is balanced on both sides of the magnet 9 as shown in FIG. 6B, and the detection signal is turned off.

  Further, the waveforms of the detection signals of the Hall element and the AMR sensor 10 at this time are as shown in FIG. The wavy line in FIG. 8 is a detection signal from the Hall element, and the solid line is a detection signal from the AMR sensor 10. According to this, there is a detection time in a section with a considerable width including the lowest end of the circular orbit of the magnet 9, and the AMR sensor 10 cannot detect the magnet 9 in this section. A pulse (2 pulses in total) is generated in each of the first half section I and the second half section II across the non-detection section (see FIG. 2). Explaining the specific value of the detection time, when detecting the presence of toner using an AMR sensor (manufactured by Murata Manufacturing Co., Ltd.) having a minimum sensitivity of 3.0 mT, as an example, the sensor detection time is 1180 msec, the non-detection section is 280 msec, The first half section I was 450 msec, and similarly the second half section II was 450 msec. As a result, two pulses are output. Usually, this is the value. The detection time of the Hall element having the lowest sensitivity of 11.7 mT measured for comparison in FIG. 8 is 480 msec (one pulse). FIG. 8 shows the characteristics of both magnetic sensors S.

  Referring to FIG. 2 in more detail, the stirring paddle 7 rotates around the rotating shaft 7a, and the free paddle 11 that rotates with the rotating paddle 7 also rotates around the rotating shaft 7a. The magnet 9 provided at the tip of the free paddle 11 also rotates with this, and the magnetic field also rotates. When the AMR sensor 10 is disposed at a position below θ0 located at the lowermost end of the free paddle 11 as shown in FIG. 2, the AMR sensor 10 starts to detect the magnetic flux of the magnet 9 at the detection start angle position θ1, and θ2 The magnetic flux is detected to a position indicating, and a detection signal is output. This range is the sensor detection first half section I.

  However, the magnetic flux is not detected while passing through the sensor detection first half section I and the magnet 9 exists between the position θ2 through the position θ0 and the position θ3. The detection signal is turned off. This range is the first non-detection section of the AMR sensor 10. Further, the magnetic flux is detected again at the detection end angle until the magnet 9 passes the position θ3 and reaches the position θ4. This is the sensor detection latter half section II. When the position θ4 is passed, the second non-detection section is reached again until θ1.

  Therefore, the AMR sensor 10 having the characteristic of nonlinear response (two-pulse output) with respect to the distance to the magnet 9 cannot be used for detecting the remaining amount of toner 5 in the arrangement as shown in FIG.

  Therefore, in the first embodiment of the present invention, the remaining amount of toner 5 is detected by the AMR sensor 10 by devising the arrangement and installation direction of the AMR sensor 10 as shown in FIGS. 10 (a) and 10 (b). It was realized.

  10A and 10B, A, B, and C are three points on the circular orbit drawn by the magnet 9. FIG. In the figure, the donut-shaped ring indicates lines of magnetic force. The range from position θ1 to θ4 on the orbit is the magnetic field detection range. θ0 is a position that is the lowermost end of the free paddle 11 and serves as a reference for the paddle angle. This position is the lowermost position when it is lowered by its own weight in the absence of toner 5 (the position when it is gravity-stable and is suspended by its own weight). As can be seen from FIGS. 10 (b), 11 (a) and 11 (b), the AMR sensor 10 is disposed at a position initially displaced in the circular orbit drawn by the magnet 9. This arrangement is a position where the above-described first non-detection section does not appear in the AMR sensor 10. That is, of the magnetic flux of the magnet 9, only the magnetic flux on the rotation direction side is limited to the range of θ1 to θ4, and in terms of the period, only during the first and second timings (time) corresponding to θ1 and θ4, respectively. It arrange | positions away from the track | orbit of the magnet 9 in the distance which can be detected.

Therefore, in the first embodiment, the rotation direction of the free paddle 11 is lower than the plane M including the position of the paddle angle reference θ0 where the free paddle 11 on which the AMR sensor 10 is rotatably placed and the rotation shaft 7a is included. Take measures to place in. In addition, in the first embodiment, as shown in FIGS. 10B and 11B, not only the shift amount L1 on the downstream side in the rotation direction from the rotation shaft 7a but also the shift amount L2 in the direction of the rotation shaft 7a. It is provided and arranged. With such an arrangement, it is possible to react only to the magnetic flux on the approaching side of the magnet 9, and the AMR sensor 10 outputs an ON signal near the paddle angle reference θ 0, and the detection end angle and When the distance passes through θ4, the distance increases again, the AMR sensor 10 becomes unresponsive and turns off. One pulse can be output by using an inexpensive and highly sensitive AMR sensor 10. The direction in which the AMR sensor 10 is disposed is the longitudinal direction of the thin film 22 when the magnet 9 is at the position θ0 in FIG. Is the direction in which the current flows (y-axis direction), and the direction of the magnetic lines of force may be the direction of the x-axis direction orthogonal thereto. Although it may be better to incline the z-axis by the magnetic force of the magnet 9, the position of the AMR sensor 10 spreads two-dimensionally so that the xy plane of FIG. Since it can be placed in a positional relationship, it is usually sufficient without taking into account the setting of the elevation angle of the attachment member surface with respect to the position θ0. That is, the sensitivity of the AMR sensor 10 is high (it can be sufficiently detected even if the shift amounts L1 and L2 from the paddle angle reference θ0 are large). However, the magnetic flux detection time can be shortened by making the shift large and appropriate. The start angle position θ1 and the detection end angle θ4 can be set to appropriate angles. The greater the distance, the less the elevation angle becomes less problematic. In some cases, the deviation amounts L1 and L2 may be adjusted in advance by setting a predetermined elevation angle.

  Thus, depending on the sensitivity of the AMR sensor 10 and the strength of the magnetic force of the magnet 9, the three-dimensional distance from the θ0 of the paddle angle reference (in addition to the shift amounts L1 and L2, the height to the orbit in the z-axis direction is considered. And the installation direction of the AMR sensor 10 can be determined. The height of the image forming apparatus is often desired to be thin, and increasing the height in the z-axis direction is often limited. Therefore, in terms of structure, it is preferable to adjust θ1 and θ4 by increasing / decreasing the shift amount in a predetermined xy plane as shown in FIG.

  Even if the AMR sensor 10 is a low-sensitivity product of about 3.0 mT, the detection time is twice or more as compared with the Hall element. When θ1 increases, the detection time becomes longer and the remaining amount of toner increases. Therefore, it is conventional to adjust the shift amount so that θ1 and θ4 of the AMR sensor 10 are positioned at the same positions as θ1 and θ4 of the Hall elements. Therefore, the structure of the image forming apparatus of FIG. The angle α formed by θ0 and the AMR sensor 10 is preferably 25 ° ± 5 °. The distance should be adjusted at this angle. However, if 0 ° <α <30 °, the magnetic flux can be sufficiently detected.

  FIG. 11A shows a state in which the image forming unit 1 is taken out from the image forming apparatus, and at this time, the case 16 serving as a bottom surface to which the image forming unit 1 is mounted is exposed. The AMR sensor 10 is provided in a state of being hidden under the case 16, but in FIG. 11A, the position is shown by a solid line for easy understanding. A perspective view showing this by partially crushing the case 16 is a partially broken perspective view in a state where the image forming unit of the image forming apparatus of FIG. 12 is taken out. In FIG. 12, the AMR sensor 10 is fixed to the bottom surface of the image forming apparatus via an attachment member 15. The attachment member 15 is disposed so as to have a predetermined angle α determined by the position from the rotation shaft 7a and θ0, and shift amounts L1 and L2, and an elevation angle is also provided on the surface. The AMR sensor 10 is placed and fixed on this surface. The attachment member 15 is screwed together with the AMR sensor 10 to the bottom surface. The output terminal from the AMR sensor 10 is connected to the control unit 12 as shown in FIGS.

  As described above, the image forming apparatus according to the first embodiment can realize an inexpensive and high-sensitivity toner detection apparatus using an AMR sensor. The problem of no detection time peculiar to the AMR sensor can be solved without using an expensive Hall element as in the prior art, and the control can be performed by the conventional control method without reexamining the control specifications. There is no need to increase the height of the image forming apparatus because of the structure.

  The present invention can be applied to an image forming apparatus including a toner detection device.

1 is an enlarged configuration diagram of an image forming unit of an image forming apparatus according to Embodiment 1 of the present invention. Operation explanatory diagram when the AMR sensor is disposed below the paddle angle reference FIG. 2 is a main part control block diagram of the image forming apparatus according to the first embodiment of the present invention. (A) Principle explanatory diagram of residual detection when toner is present by magnetic sensor S, (b) Principle explanatory diagram of residual detection when no toner is present by magnetic sensor S Illustration of the appearance of the AMR sensor and the effect of anisotropic magnetoresistance (A) Explanatory diagram showing the magnetic field detection direction of the Hall element, (b) Explanatory diagram showing the magnetic field detection direction of the AMR sensor (A) Explanatory diagram of response characteristics of Hall element, (b) Explanatory diagram of response characteristics of AMR sensor Waveform diagram of output signal of Hall element and AMR sensor Arrangement explanatory drawing of the toner detection device of the image forming apparatus in Embodiment 1 of the present invention FIG. 9A is a perspective view of the magnet track and the AMR sensor of the toner detection device of the image forming apparatus of FIG. 9, and FIG. 10B is a front view of the toner detection device of FIG. (A) A perspective view of the image forming apparatus according to Embodiment 1 of the present invention with the image forming unit taken out, (b) An explanatory diagram showing the amount of deviation of the AMR sensor 1 is a partially fragmented perspective view of an image forming apparatus according to Embodiment 1 of the present invention in a state where an image forming unit is taken out. Structure of a conventional image forming apparatus Structure of a conventional image forming apparatus Configuration diagram of a conventional toner detection device

DESCRIPTION OF SYMBOLS 1 Image formation part 2 Photoconductor drum 3 Charger 4 Toner container 5 Toner 6 Developing roller 7 Stirring paddle 7a Rotating shaft 8 Supply roller 9 Magnet 10 AMR sensor 11 Free paddle 12 Control part 12a Detection means 13 Power supply part controller 14 Display part 15 Mounting member 16 Case 21 Substrate 22 Thin film 23, 24 Electrode 101 Paper feed tray 102 Paper feed roller 103 Transport roller 104 Image forming unit 105 Photosensitive drum 106 Charger 107 LSU
108 Developing Roller 109 Transfer Roller 110 Fixing Roller 111 Paper Discharge Roller 112 Stirring Paddle 113 Supply Roller 114 Toner Container 121 Image Forming Unit 122 LSU
123 Intermediate transfer belt 124 Primary transfer roller 125 Secondary transfer roller 130 Stirring paddle 131 Detector 132 Permanent magnet 133 Permeability sensor θ0, θ1, θ2, θ3, θ4 Position I First half of sensor detection section II Second half of sensor detection section α Bottom Angle between point and AMR sensor L1, L2 Deviation x, y, z Coordinate axes

Claims (5)

A container for storing toner, a toner stirring member that is provided inside the container and rotates around a rotation shaft to stir the toner, and is rotatably provided with respect to the rotation shaft and is pressed by the toner stirring member to rotate. A rotating member, a magnetic member provided at an end of the rotating member opposite to the rotating shaft, an anisotropic magnetoresistive element provided at a lower portion of the container for detecting the magnetic member, and the different member. Detecting means for detecting the amount of toner based on a change in time for detecting the magnetic member by the isotropic magnetoresistive element, and the rotating member that is capable of rotating the anisotropic magnetoresistive element with respect to the rotation axis. An image forming apparatus, wherein the image forming apparatus is disposed on the downstream side in the rotation direction of the rotating member from directly below the position when the unit is suspended by its own weight. A container for storing toner, a toner stirring member that is provided inside the container and rotates around a rotation shaft to stir the toner, and is rotatably provided with respect to the rotation shaft and is pressed by the toner stirring member to rotate. A rotating member, a magnetic member provided at an end of the rotating member opposite to the rotating shaft, an anisotropic magnetoresistive element provided at a lower portion of the container for detecting the magnetic member, and the different member. Detecting means for detecting the amount of toner based on a change in time for detecting the magnetic member by the isotropic magnetoresistive element, and the rotating member that is capable of rotating the anisotropic magnetoresistive element with respect to the rotation axis. An image forming apparatus, wherein the image forming apparatus is arranged so as to be downstream in the rotational direction of the rotating member and directly in the axial direction of the rotating shaft from directly below the position when the unit is suspended by its own weight. A container for storing toner, a toner stirring member that is provided inside the container and rotates around a rotation shaft to stir the toner, and is rotatably provided with respect to the rotation shaft and is pressed by the toner stirring member to rotate. A rotating member, a magnetic member provided at an end of the rotating member opposite to the rotating shaft, an anisotropic magnetoresistive element provided at a lower portion of the container for detecting the magnetic member, and the different member. Detecting means for detecting the amount of toner based on a change in time for detecting the magnetic member by the isotropic magnetoresistive element, and the rotating member that is capable of rotating the anisotropic magnetoresistive element with respect to the rotation axis. Only the magnetic flux on the rotational direction side of the magnetic member on the downstream side in the rotational direction of the rotating member from just below the position when suspended by its own weight is limited to the first and second timings of the cycle. Can detect An image forming apparatus characterized in that spaced apart from the track of the magnetic body distance. The anisotropic magnetoresistive element includes a pair of electrodes and a thin film ferromagnetic metal provided between the pair of electrodes, and the thin film ferromagnetic metal has a predetermined angle with respect to a magnetic flux direction of the magnetic member. in the image forming apparatus according to claim 1, 2 or 3, characterized in that it is arranged. The detection means detects that the remaining amount of toner is large when the time for detecting the magnetic member is shorter than a predetermined time, and detects that the remaining amount of toner is low when the time is longer than the predetermined time. the image forming apparatus according to claim 1, 2, 3 or 4 to.

Images