JP4008438B2 - Development device - Google Patents

Description

  The present invention relates to a developing device having a function of detecting the remaining amount of developer remaining in a developing tank.

  The developing device needs to be replaced with a new developing device when the developer stored in the developing tank is exhausted. Therefore, the developing device is provided with a developer detection mechanism for detecting the remaining amount of developer stored in the developing tank.

  As a technique related to such a developer detection mechanism, a developer detection mechanism shown in FIG. 13 is known (see, for example, Patent Document 1).

  This developer detection mechanism is a U-shaped toner agitator that sends developer (hereinafter referred to as “toner”) accumulated in a developer tank (hereinafter referred to as “toner tank”) 200 to a developing roller (not shown). A member 201 is provided, and further, at one end thereof, a rotating shaft 202 that supports the member and a gear 203 that rotates the rotating shaft 202 by an external force are provided.

  A slit plate 205 that passes between the photosensors 204 is provided at the other end of the toner stirring member 201. The slit plate 205 is a disk having a plurality of slits. In addition, a light emitting unit and a light detecting unit are arranged to face each other in the photosensor 204, and the slit plate 205 is set so as to pass between them. Accordingly, the light detection unit of the photosensor 204 is turned on (receives light from the light emitting unit) when the slit of the slit plate 205 passes through the photosensor 204.

  In the toner tank 200, the U-shaped toner stirring member 201 rotates to stir the internal toner, and a part of the toner is sent to the developing roller. Further, during the stirring, when the toner stirring member 201 enters the toner (toner reservoir) of the toner stirring member 201, the rotation speed is momentarily decreased because of the resistance by the toner. Accordingly, the speed at which the slit plate 205 rotating together with the toner agitating member 201 passes through the photosensor 204 is also reduced. For this reason, the period of light detection in the photosensor 204 (corresponding to the passage period of the slit) becomes longer.

  On the other hand, when the toner stirring member 201 escapes from the toner, the resistance of the toner suddenly disappears, so that the rotational speed is increased momentarily. Accordingly, the speed at which the slit plate 205 passes through the photosensor 204 is similarly increased, and the light detection period of the photosensor 204 is shortened.

Further, the time from the entry to the exit of the toner by the toner stirring member 201 becomes longer as the amount of toner contained (the remaining amount of toner) increases. Therefore, in the toner tank 200, it is possible to estimate the remaining amount of toner by monitoring the change in the light detection period in the photosensor 204.
JP 2004-12893 A

  By the way, in many cases, an image printed on a recording sheet is generally concentrated in a central portion rather than an end portion of the recording sheet. For this reason, the toner in the toner tank 200 consumes a large amount at the center and consumes less at both ends. Therefore, the toner in the toner tank 200 has a difference in level as a whole, and density unevenness occurs during printing. There was a problem.

  However, the conventional developer detection mechanism described above merely agitates the toner in the toner tank 200 by the toner agitating member 201 and does not have the ability to convey the toner in the lateral direction. That is, it does not have the ability to make the toner level in the entire width direction in the toner tank 200 uniform. Therefore, if there is an extreme difference in toner level between the center and both ends of the toner tank 200, there is a possibility that an error in detecting the remaining amount of toner may occur, and sufficient detection accuracy may not be ensured. There was a problem.

  The present invention was devised to solve such problems. The purpose of the present invention is to decenter the weight balance of the agitating and conveying roller that agitates and conveys the toner, thereby providing the function as the toner agitating member of the above-described prior art. Another object of the present invention is to provide a developing device having a developer detection mechanism with high detection accuracy that has both the ability to convey toner and the ability to stir.

  The developing device of the present invention includes an agitating and conveying member that agitates and conveys the developer that is eccentrically distributed with respect to the rotation center, a detachable drive transmission member that rotationally drives the agitating and conveying member, and the agitation A rotation detector for detecting a rotation state of the conveying member, and detecting a remaining amount of the developer based on the rotation state detected by the rotation detector.

  According to the developing device having the above-described configuration, the agitating and conveying member is eccentrically distributed with respect to the rotation center. Specifically, the stirring and conveying member is composed of a rotating shaft and a conveying blade arranged in a spiral around the rotating shaft, and a rod-like shape arranged in parallel to the rotating shaft at the peripheral end of the conveying blade. It has a structure with an eccentric rod attached. That is, the eccentric rods are fixed at a plurality of locations on the peripheral end of the conveying blade at a constant interval that matches the helical pitch of the conveying blade.

The drive transmission member has a detachable clutch structure that applies a rotational force to the rotation shaft of the agitation transport member by an external force. More specifically, the drive transmission member includes a disk-shaped rotated plate attached to one end of the rotating shaft, and a disk-shaped transmission rotating plate that transmits an external force to the rotated plate. The rotating plate is provided with an engaging pin at one position on the peripheral edge of the transmission rotating plate on the opposite surface side, and the transmission rotating plate passes the center of rotation on the opposite surface side of the rotating plate. In the rotation detector, the light emitting element and the light receiving element are arranged to face each other through a concave groove portion in the case body formed in a concave shape in cross section. The detection is formed in the fan shape passing through the concave groove portion on the rotary shaft facing the opening of the concave groove portion, the concave groove portion being arranged to open toward the axis of the rotary shaft. A plate is provided. That is, when the eccentric rod rotates 180 degrees in one direction from the lowermost position to the uppermost position, the transmission mechanism portion (transmission rotating plate) on the side transmitting the external force is provided on the rotating shaft side that receives the external force. The transmitted mechanism portion (rotated plate) is engaged so as to push it up in one direction, and the rotational force is transmitted. On the other hand, when the eccentric rod further rotates slightly in one direction from the uppermost portion, the stirring and conveying member rotates at an increased rotational speed due to the eccentric load caused by the eccentric rod. In other words, when the eccentric rod rotates in one direction from the top to the bottom, the rotational speed at which the agitating and conveying member rotates due to the eccentric load due to the eccentric rod is faster than the rotational speed received from the external force. transmission mechanism on the side of transmitted (transmission rotary plate), the engagement between the transmission mechanism provided on the rotary shaft side (the rotating plate) is to be released.

Such a difference in rotational speed, that is, the rotation speed of the agitating / conveying member when the eccentric rod rotates 180 degrees in one direction from the bottom to the top, and 180 degrees in one direction from the top to the bottom The difference from the rotational speed of the agitating / conveying member occurs when almost no developer remains in the developing tank, and does not occur when sufficient developer remains in the developing tank. In other words, when the developer remains sufficiently in the developing tank and the agitating / conveying member is buried in the developer, the eccentric rod is subjected to a load from the developer. For this reason, even if an eccentric load due to the eccentric rod is applied to the agitating / conveying member by further rotating the eccentric rod from the top to one direction, a load sufficient to cancel the eccentric load is applied to the eccentric rod from the developer. Will be. As a result, even when the eccentric rod rotates 180 degrees in one direction from the uppermost part to the lowermost part, the transmission mechanism part (transmission rotating plate) on the side transmitting the external force is transmitted to the transmission mechanism part ( The rotating plate is engaged so as to push it down in one direction, and the rotational force is transmitted. That is, when a sufficient amount of developer remains in the developing tank, the agitation transport member always rotates at a constant rotational speed regardless of the load caused by the eccentric wrinkle.

  As can be understood from the above description, the rotation speed pattern of the agitating / conveying member when it rotates once varies depending on the remaining amount of the developer in the developing tank. Therefore, the remaining amount of the developer can be detected by detecting this rotation speed pattern with the rotation detector. In this case, the rotation detector is provided in the agitating / conveying member, and the agitating / conveying member has the ability to convey the developer in the developing tank from, for example, both ends toward the center. The developer in the tank has a uniform powder pressure and is always leveled. Therefore, it is possible to maintain a good image quality and to detect the remaining amount of the developer with high accuracy without causing a detection error as in the prior art.

  In the present invention, such a stirring and conveying member is disposed above the developer supply roller. By disposing in this portion, the developer powder pressure in the vicinity of the developer supply roller and in the vicinity of the developer layer thickness regulating member (layer pressure regulating blade) can be made uniform, and a more stable operation is possible. Further, the rotation detector may be configured to generate a plurality of output pulses for one rotation of the stirring and conveying member. Thereby, the remaining amount of the developer can be detected with higher accuracy.

  Moreover, in this invention, you may arrange | position one or more 2nd stirring conveyance members different from the said stirring conveyance member. In this case, the second agitating and conveying member is configured to agitate and convey the internal developer in a direction opposite to the agitating and conveying direction of the agitating and conveying member. In this way, by setting the conveying direction opposite to the conveying direction of the agitating and conveying member that is eccentric and distributed in weight, the developer powder pressure can be made more uniform, and the upper surface of the developer is leveled more flat. Thus, the image quality can be further improved and the remaining amount detection accuracy can be improved.

  In the present invention, the eccentric weight distribution is realized by using a rod-like weight member (for example, a stainless shaft) that is arranged and fixed eccentrically with respect to the rotating shaft without using the eccentric rod. Also good. In this case, the agitating and conveying member is constituted by a spiral member having an inner diameter larger than the outer diameter of the weight member (stainless shaft), and the agitating and conveying is realized by rotatably inserting the helical member into the stainless steel shaft. Also good. Here, a coil spring can be used as the spiral member.

  Stirring by a stirring blade (screw) causes the toner to be packed and solidified around the screw due to a decrease in toner fluidity due to changes in humidity, etc., resulting in insufficient toner supply, increased stirring driving torque, locking and locking of the stirring drive system There is a risk of damage to the drive system accompanying this. On the other hand, in the method of stirring and transporting using a coil spring with play as in the present invention, the coil spring can move in the radial direction, so that the toner that causes solidification around the spiral rotates without staying. Accordingly, it is possible to prevent a harmful effect such as packing and solidification, and to perform a highly reliable developing operation. Furthermore, when a load is applied by the toner as a result of rotation driving, if there is no stainless steel shaft, the coil spring will be bent and bend and contact the inner wall of the case. Since deformation is regulated by the stainless steel shaft, highly reliable operation is possible.

  In the present invention, the coil spring may be composed of a plurality of separated members having different winding directions. For example, it may be separated into two coil springs, a right-handed winding and a left-handed winding, at the central portion of the stainless steel shaft. Since the developer in the developing tank is conveyed so as to gather from, for example, both ends toward the center by the two coil springs of such reverse winding, the powder pressure of the developer in the developing tank is made uniform, And it will always be leveled. Therefore, it is possible to maintain a good image quality and to detect the remaining amount of the developer with high accuracy without causing a detection error as in the prior art. Also, if you try to secure the agitation function (function to loosen the coherent toner) with a screw, there is a risk that the conveying force will be too strong and the toner thickness at the center will be too high. Since the degree of freedom is large, such a problem can be easily solved.

  In the present invention, the coil spring is inserted into the stainless steel shaft with a clearance that can move in the thrust direction. By inserting into the stainless steel shaft with a clearance in this way, even when the coil spring is stretched and deformed due to a load of toner, the clearance can be absorbed by the clearance, and failure due to stretching and contacting the side wall can be prevented. be able to. Note that the present invention works effectively in the case where any of a plurality of separated coil springs described in detail in the embodiment or a single coil spring having a substantially developing width is used. Further, in this case, the coil spring is configured such that both ends are tightly wound around the stainless steel shaft. Thus, it is possible to prevent the adjacent ends of the plurality of separated coil springs from being inadvertently entangled with each other. Further, even when a plurality of or single coil spring ends rub against the inner wall of the case, the inner wall of the case can be prevented from being damaged.

  According to the developing device of the present invention, the agitating and conveying member for agitating and conveying the developer that is eccentrically distributed with respect to the rotation center, the detachable drive transmission member for rotationally driving the agitating and conveying member, and the agitation Since it has a configuration that includes a rotation detector that detects the rotation state of the conveying member, the developer in the developer tank has a uniform powder pressure and is always leveled to a flat surface. And the remaining amount of the developer can be detected with high accuracy. In addition, by providing the second agitating / conveying member in parallel with the agitating / conveying member, the developer in the developing tank has a more uniform powder pressure and is evened to a flat surface. The image quality can be maintained and the remaining amount of the developer can be detected with higher accuracy.

  Further, according to the developing device of the present invention, as a means for realizing the eccentric weight distribution, a rod-like weight member that is arranged and fixed eccentrically with respect to the rotation shaft is used, and the stirring and conveying member is formed from the outer diameter of the weight member. The coil spring is a helical member with a large inner diameter, and this coil spring is rotatably inserted into the weight member to achieve agitation and conveyance. In addition, since it is always leveled to a flat surface, it is possible to maintain good image quality and to accurately detect the remaining amount of developer. In addition, by moving the coil spring in the radial direction, the toner that causes solidification around the spiral is discharged with rotation without staying, preventing adverse effects such as packing and solidification, and a highly reliable development operation is possible. Become.

  Hereinafter, an image forming apparatus including a developing device according to an embodiment of the present invention will be described with reference to the drawings.

-Description of the entire image forming apparatus-
FIG. 1 is a schematic sectional view showing a configuration of a digital color copying machine (hereinafter simply referred to as a copying machine) 100 as a color image forming apparatus according to the present embodiment.

  The copying machine 100 forms multicolor and single color images on a predetermined sheet (recording paper) in accordance with image data transmitted from the outside, and includes an exposure unit 1, a developing device 2, and a photoconductor. The drum 3, the charger 5, the cleaner unit 4, the transfer conveyance belt unit 8, the fixing unit 12, the sheet conveyance path S, the sheet feed tray 10, the sheet discharge trays 15 and 33, and the like.

  Note that image data handled in the copying machine 100 corresponds to a color image using each color of black (K), cyan (C), magenta (M), and yellow (Y). Accordingly, the exposure unit 1 (1a, 1b, 1c, 1d), the developing device 2 (2a, 2b, 2c, 2d), the photosensitive drum 3 (3a, 3b, 3c, 3d), and the charger 5 (5a, 5b, 5c, 5d) and four cleaner units 4 (4a, 4b, 4c, 3d) are provided so as to form four types of latent images corresponding to the respective colors, a being black, b being cyan, Four image stations are configured with c set to magenta and d set to yellow.

  The photosensitive drum 3 is disposed (attached) at substantially the center of the copying machine 100.

  The charger 5 is a charging means for uniformly charging the surface of the photosensitive drum 3 to a predetermined potential. In addition to a contact type roller type or brush type charger, a charger type as shown in FIG. The charger is used.

  The exposure unit 1 uses, for example, an EL or LED writing head in which light emitting elements are arranged in an array, or a laser scanning unit (LSU) including a laser irradiation unit and a reflection mirror. The charged photosensitive drum 3 has a function of forming an electrostatic latent image corresponding to the image data on the surface thereof by exposing the photosensitive drum 3 according to the input image data.

  The developing device 2 visualizes the electrostatic latent images formed on the respective photosensitive drums with (K, C, M, Y) toner. The cleaner unit 4 removes and collects toner remaining on the surface of the photosensitive drum after development and image transfer.

  The transfer conveyance belt unit 8 disposed below the photosensitive drum 3 includes a transfer belt 7, a transfer belt driving roller 71, a transfer belt tension roller 73, transfer belt driven rollers 72 and 74, and transfer rollers 6 (6a, 6b, 6c, 6d) and a transfer belt cleaning unit 9.

  The transfer belt driving roller 71, the transfer belt tension roller 73, the transfer roller 6, the transfer belt driven rollers 72, 74, and the like stretch the transfer belt 7 and rotate the transfer belt 7 in the direction of arrow B.

  The transfer roller 6 is rotatably supported by a transfer roller mounting portion of a housing (not shown) of the transfer belt unit 8, and a sheet (recording) on which the toner image on the photosensitive drum 3 is adsorbed onto the transfer belt 7 and conveyed. A transfer bias for transferring to a sheet of paper.

  The transfer belt 7 is provided so as to come into contact with the respective photosensitive drums 3, and each color toner image formed on the photosensitive drum 3 is sequentially superimposed and transferred onto a sheet (recording paper). Thus, a color toner image (multicolor toner image) is formed. This transfer belt is formed endlessly using a film having a thickness of about 100 μm to 150 μm.

  The transfer of the toner image from the photosensitive drum 3 to the sheet (recording paper) is performed by the transfer roller 6 in contact with the back side of the transfer belt 7. A high voltage transfer bias (a high voltage having a polarity (+) opposite to the toner charging polarity (−)) is applied to the transfer roller 6 in order to transfer the toner image. The transfer roller is a roller whose base is a metal (for example, stainless steel) shaft having a diameter of 8 to 10 mm and whose surface is covered with a conductive elastic material (for example, EPDM, urethane foam, or the like). With this conductive elastic material, a high voltage can be uniformly applied to the recording paper (sheet). In this embodiment, the transfer roller 6 is used as the transfer electrode, but a brush or the like is also used.

  Further, the toner adhering to the transfer belt 7 due to contact with the photosensitive drum 3 is set to be removed and collected by the transfer belt cleaning unit 9 in order to cause the back surface of the recording paper to become dirty. The transfer belt cleaning unit 9 includes a cleaning blade as a cleaning member that contacts the transfer belt 7, for example, and the transfer belt 7 that contacts the cleaning blade is supported by a transfer belt driven roller 74 from the back side.

  The paper feed tray 10 is a tray for storing sheets (recording paper) used for image formation, and is provided below the image forming unit of the copying machine 100. A paper discharge tray 15 provided at the top of the copying machine 100 is a tray for placing printed sheets face down, and a paper discharge tray provided at the side of the copying machine. Reference numeral 33 denotes a tray on which an image-formed sheet is placed face up.

  Further, the copying machine 100 is provided with an S-shaped sheet conveyance path S for sending the sheet in the sheet feeding tray 10 to the sheet discharge tray 15 via the transfer conveyance unit 8 and the fixing unit 12. Yes. Further, in the vicinity of the sheet conveyance path S from the sheet feed tray 10 to the sheet discharge tray 15 and the sheet discharge tray 33, a pickup roller 16, a registration roller 14, a fixing unit 12, a conveyance direction switching guide 34, and a conveyance for conveying a sheet. A roller 36 and the like are arranged.

  The conveyance roller 36 is a small roller for promoting and assisting conveyance of the sheet, and a plurality of conveyance rollers 36 are provided along the sheet conveyance path S. The pickup roller 16 is a drawing roller that is provided at the end of the paper feed tray 10 and feeds sheets one by one from the paper feed tray 10 to the paper transport path S.

  The conveyance direction switching guide 34 is rotatably provided on the side cover 35, and the sheet is separated from the middle of the conveyance path S by changing from the state indicated by the solid line to the state indicated by the broken line, and the sheet is placed on the sheet discharge tray 33. Can be discharged. In the state indicated by the solid line, the sheet passes through the conveyance unit S ′ (a part of the sheet conveyance path S) formed between the fixing unit 12, the side cover 35, and the conveyance switching guide 34, and the upper discharge tray 15. To be discharged.

  Further, the registration roller 14 temporarily holds the sheet being conveyed on the sheet conveyance path S. The sheet has a function of transporting the sheet with good timing in accordance with the rotation of the photosensitive drum 3 so that the toner image on the photosensitive drum 3 can be satisfactorily transferred onto the sheet.

  That is, the registration roller 14 conveys the sheet so that the leading edge of the toner image on each photosensitive drum 3 is aligned with the leading edge of the image forming range on the sheet based on a detection signal output from a pre-registration detection switch (not shown). Is set to

  The fixing unit 12 includes a heat roller 31, a pressure roller 32, and the like, and the heat roller 31 and the pressure roller 32 rotate with a sheet interposed therebetween.

  Further, the heat roller 31 is controlled by the control unit so as to reach a predetermined fixing temperature based on a signal from a temperature detector (not shown), and is transferred to the sheet by thermocompression bonding with the pressure roller 33. The resulting multicolor toner image is melted, mixed, and pressed to thermally fix the sheet.

  The sheet after the fixing of the multicolor toner image is transported to the reverse paper discharge path of the paper transport path S by the transport roller 36 and discharged in a reversed state (with the multicolor toner image facing downward). The paper is discharged onto the tray 15.

-Description of the developing device according to the present invention-
FIG. 2 is an enlarged schematic sectional view showing the developing device 2 according to the present invention.

  In the developing device 2, a developing roller 21 is disposed horizontally (disposed perpendicularly to the paper surface) inside the developing tank 20 so as to face the photosensitive drum 3, and is in contact with the developing roller 21. The toner supply roller 22 is horizontally disposed. The developing roller 21 is provided with a layer pressure regulating blade 23 for regulating the layer pressure of the toner attached to the roller. In addition, the agitating and conveying roller 24 for agitating and conveying the toner is disposed horizontally in the vicinity of the upper portion of the toner supply roller 23 and the layer pressure regulating blade 23 arranged in this manner. In the present embodiment, the stirring and conveying roller 24 is eccentrically distributed with respect to the center of rotation.

  FIG. 3 is an explanatory diagram of a developer detection mechanism unit of the developing device having the above configuration.

  The agitating / conveying roller 24 is composed of a rotating shaft 24a and a conveying blade 24b arranged in a spiral around the rotating shaft 24a, and a rod-like member arranged in parallel to the rotating shaft 24a at the peripheral end of the conveying blade 24b. The eccentric rod 24c is attached. That is, the eccentric rods 24c are fixed at a plurality of locations on the peripheral end portion of the conveying blade 24b at a constant interval in accordance with the helical pitch of the conveying blade 24b. In the present embodiment, the conveying blade 24b is divided into two in the left and right directions, and the respective spiral directions are opposite to each other. Therefore, the toner in the developing tank 20 is transported from both ends toward the center or from the center toward both ends depending on the rotation direction of the rotation shaft 24a. In this embodiment, as shown by the arrows in the figure, it is conveyed from both ends toward the center.

  A drive transmission member 27 is provided at one end (right end in FIG. 3) of the rotating shaft 24a. The drive transmission member 27 has a detachable clutch structure that applies a rotational force to the rotating shaft 24a of the agitating / conveying roller 24 by an external force, and includes a disk-shaped rotated plate 25 attached to the rotating shaft 24a side, It comprises a disk-shaped transmission rotating plate 26 on the side for transmitting an external force (not shown). As shown in FIGS. 4 (a) and 4 (b), the rotation plate 25 is provided with an engagement pin 25 a at one location on the peripheral edge of the transmission rotation plate 26 on the opposite surface side. On the other hand, as shown in FIGS. 4 (c) and 4 (d), the transmission rotating plate 26 has an engagement piece 26 a formed on the opposite surface side of the rotated plate 25 so as to project diagonally so as to pass through the center of rotation. Is provided.

  FIG. 5 shows a state in which the agitating and conveying roller 24 is rotated by the drive transmission member 27 having the above configuration. However, in this example, a case will be described in which the engagement pin 25a and the eccentric rod 24c are provided at positions facing each other diagonally via the rotation center of the rotated plate 25.

  The eccentric rod 24c rotates 180 degrees in one direction (clockwise) from the lowermost position shown in FIG. 5 (a) to the uppermost position shown in FIG. 5 (c) through the position shown in FIG. 5 (b). When engaging, the engaging piece 26a of the transmission rotating plate 26 that transmits external force always engages and rotates so as to push down the engaging pin 25a of the rotated plate 25 in one direction (clockwise).

  Thereafter, when there is no toner in the developing layer 20, as shown in FIG. 5D, when the eccentric rod 24c is further rotated slightly in one direction (clockwise) from the top, the eccentricity by the eccentric rod 24c. The agitating / conveying roller 24 rotates at a higher rotational speed due to the load. That is, when the eccentric rod 24c rotates in one direction (clockwise) from the top to the bottom, the rotational speed at which the agitating and conveying roller 24 rotates due to the eccentric load by the eccentric rod 24c is higher than the rotational speed received from the external force. As a result, as shown in FIGS. 5D and 5E, as shown in FIGS. 5D and 5E, the engagement pin 25a rotates freely in a state where it is separated from the engagement piece 26a (that is, in a state where the engagement is released). become. In other words, when there is no toner in the developing layer 20 (when the remaining amount is small), a period during which the rotation speed is high and a period during which the agitation conveyance roller 24 rotates once are generated.

  On the other hand, when the toner is present in the developing layer 20 (that is, when the agitating / conveying roller 24 is buried in the toner), the eccentric rod 24c is further rotated slightly in one direction (clockwise) from the top. Thus, even if an eccentric load due to the eccentric rod 24c is applied to the agitating / conveying roller 24, a load sufficient to cancel the eccentric load is applied from the toner to the eccentric rod 24c. As a result, as shown in FIGS. 5D and 5E, the engaging piece 26a is engaged even while the eccentric rod 24c rotates 180 degrees in one direction (clockwise) from the top to the bottom. The pin 25a rotates while maintaining the engagement relationship so as to push it up in one direction (clockwise). In other words, when sufficient toner remains in the developing tank 20, the stirring and conveying roller 24 always rotates at a constant rotational speed by the rotational force of the external force regardless of the load by the eccentric rod 24c.

  As can be understood from the above description, the rotation speed pattern of the agitating and conveying roller 24 when it rotates once varies depending on the remaining amount of toner in the developing tank 20. Therefore, it is possible to detect the remaining amount of toner by detecting this rotational speed pattern.

  Therefore, as shown in FIG. 3, a rotation detector 28 for detecting the rotation of the stirring and conveying roller 24 is provided between the stirring and conveying roller 24 and the drive transmission member 27. The rotation detector 28 is a transmissive photocoupler in which a light emitting element and a light receiving element are arranged to face each other through a concave groove 28a in a case body formed in a concave shape in cross section. The rotation detector 28 is arranged so as to open the concave groove 28a toward the axis of the rotation shaft 24a. On the other hand, the rotating shaft 24a facing the opening of the concave groove 28a is provided with a detection plate 28b formed in a fan shape as shown by a broken line in FIG. The rotation of the agitation transport roller 24 is detected by passing through the concave groove 28 a of the rotation detector 28.

  As described above, the rotational speed pattern of the agitating and conveying roller 24 differs depending on whether or not there is toner in the developing tank 20.

  FIG. 6 shows a detection waveform when the rotation of the agitating / conveying roller 24 is detected by the rotation detector 28 having the above-described configuration. In FIG. 6A, when the toner is present, FIG. Is the case. However, this signal waveform indicates that the detection plate 28b passes through the concave groove 28a of the rotation detector 28, that is, when the rotation detector 28 is in the OFF state, as an “H” level signal. As shown in FIG. 6, the period of “H” level differs between when toner is present and when toner is absent (t11> t12). Accordingly, it is possible to detect whether or not there is toner in the developing tank 20 based on the difference in the “H” level period. That is, in a state where there is sufficient toner and the agitating / conveying roller 24 is buried in the toner, the signal shown in FIG. 6A is detected, the remaining amount of toner decreases, and the agitating / conveying roller 24 moves from the upper surface of the toner. In the state of being exposed upward, the signal shown in FIG. 6B is detected. In this rotation detector 28, since the detection plate 28b has a fan shape, only one pulse signal is detected by one rotation of the agitating / conveying roller 24. Is only detected. However, it is possible to detect which level of the remaining amount of toner is by measuring the change in the period of the “H” level, but the accuracy has to be low.

  FIG. 7 shows another embodiment of the detection plate 28c. In this example, the detection plate 28c has a disk shape, and a plurality of radial slit portions are formed at equal intervals on the entire circumference. By forming the detection plate 28 c in such a shape, the rotation detector 38 can detect a plurality of pulses per one rotation of the stirring and conveying roller 24.

  FIG. 8 shows the signal waveform of the detection pulse at this time. FIG. 8A shows the case where the toner is present, and FIG. 8B shows the case where the toner is not present. However, this signal waveform indicates that the detection plate 28c passes through the concave groove 28a of the rotation detector 28, that is, when the rotation detector 28 is in the OFF state, as an “H” level signal.

  When the toner is present, the agitating and conveying roller 24 rotates one rotation at a constant speed as described above. As a result, as shown in FIG. 8A, the detection pulses are detected at regular intervals when toner is present.

  On the other hand, when there is no toner, as described above, the stirring roller 24 rotates at a constant speed during the first half rotation (180 degrees) of the rotation, and the eccentric half 24c during the next half rotation (180 degrees). The eccentric load increases the rotational speed. As a result, as shown in FIG. 8B, the pulse width and the pulse interval of the detection pulse are shorter in the next half rotation than in the first half rotation. In this example, the detection pulse is interrupted in the middle of the next half rotation. This is a detection pulse waveform when the upper surface of the toner in the developing tank 20 is at a level just around the axis of the rotation shaft 24 a of the stirring and conveying roller 24. That is, as shown in FIG. 5 (d), when the eccentric rod 24c further rotates in one direction (clockwise) from the uppermost portion, the agitating and conveying roller 24 increases its rotational speed due to the eccentric load by the eccentric rod 24c. Rotate. As a result, as shown by a period t21 in FIG. 8B, the pulse width and pulse interval of the detection pulse are shortened. Then, when the eccentric rod 24c rotates approximately 90 degrees in one direction (clockwise) from the top, the eccentric rod 24c reaches the upper surface of the toner, and the eccentric stirring rod 24c is received by the toner so that the conveying and stirring roller 24 is moved. Stop rotation. Therefore, the rotation of the conveying stirring roller 24 is continued until the engaging piece 26a of the transmission rotating plate 26 of the drive transmitting member 27 catches up with the engaging pin 25a of the rotated plate 25 (period t22 shown in FIG. 8B). Stops, and no detection pulse is output during that time. However, during this period t22, the detection pulse may be at the “H” level depending on the stop position of the detection plate 28c. When the transmission rotating plate 26 rotates 90 degrees and the engagement piece 26a catches up with the engagement pin 25a, the engagement pin 25a is pushed again by the engagement piece 26a, and the rotation is detected during the next period t23. The detector 28 outputs a detection pulse having the same pulse width and pulse interval as in the first half rotation.

  As described above, when there is no toner (exactly, when the remaining amount of toner decreases and the agitating and conveying roller 24 starts to be exposed from the toner-embedded state), the waveform (pattern) of the next half-turn detection pulse is detected. ) Becomes a pattern different from the waveform (pattern) of the detection pulse of the first half rotation. In the pattern, the ratio of the three periods t21, t22, and t23 varies depending on the height position of the toner upper surface with respect to the agitating / conveying roller 24. Therefore, the remaining amount of toner can be detected in more detail by determining the ratio of these periods.

  For example, when the total period of the above-described periods t21 and t22 is substantially equal to the period t23, the upper surface of the toner in the developing tank 20 is the height per axis center of the rotation shaft 24a of the agitation transport roller 24. It turns out that it is a level. When the total period of the periods t21 and t22 is much shorter than the period t23, the upper surface of the stirring and conveying roller 24 arranged in the horizontal direction is slightly exposed on the upper surface of the toner in the developing tank 20. It can be seen that the level is high enough. Further, when the total period of the periods t21 and t22 is very long compared to the period t23, the upper surface of the toner in the developing tank 20 is completely up to the vicinity of the lower part of the stirring and conveying roller 24 arranged in the horizontal direction. It can be seen that the level is high enough to be exposed.

  In the present embodiment, detection plates 28b and 28c that are detected by the rotation detector 28 are attached to the rotation shaft 24a of the stirring and conveying roller 24a. Further, since the agitating / conveying roller 24 has the ability to convey the toner in the developing tank 20 from both ends toward the center, the toner in the developing tank 20 has a uniform powder pressure and is always flat. Will be averaged. Therefore, it is possible to maintain a good image quality and to detect the remaining amount of toner with high accuracy without causing a detection error as in the prior art. In the present embodiment, such a stirring and conveying roller 24 is disposed in the vicinity of the upper portion of the toner supply roller 22. By disposing in this portion, the toner powder pressure in the vicinity of the toner supply roller and also in the vicinity of the layer pressure regulating blade 23 can be made uniform, and a more stable operation is possible.

<Description of Other Configuration Example 1 of Developer Detection Mechanism>
9 and 10 are explanatory views showing another configuration example 1 of the developer detection mechanism unit of the developing device 2 according to the present invention.

In addition to the stirring and conveying roller 24 configured as described above, the developer detection mechanism unit includes one second stirring and conveying roller 241 that is in the vicinity of the stirring and conveying roller 24 and in parallel with the stirring and conveying roller 24. It is a configuration. The second agitating and conveying roller 241 does not have a weight distribution that is eccentric with respect to the center of rotation. Moreover, in this structural example 1 , the conveyance blade 24b of the stirring conveyance roller 24 is not divided into two at the central portion, but rotates in a spiral manner in one direction over the entire length in the longitudinal direction. Similarly, the conveying blade 241b of the second agitating / conveying roller 241 also rotates in a spiral shape in one direction over the entire length in the longitudinal direction. In this example, by rotating the agitating / conveying roller 24 and the second agitating / conveying roller 241 in opposite directions, the agitating / conveying roller 24 moves the toner in the developing tank 20 from right to left in FIG. The toner is conveyed in the direction of the arrow X1, and the toner in the developing tank 20 is conveyed in the direction of the arrow X2 from the left to the right in FIG. That is, the toner conveyance direction by the agitation conveyance roller 24 and the toner conveyance direction by the second agitation conveyance roller 241 are set to be opposite to each other. As a result, the powder pressure of the toner can be made more uniform, and the upper surface of the toner can be leveled to a flatter surface, so that the image quality can be further improved and the remaining amount detection accuracy can be improved. In this example, only one second stirring / conveying roller 241 is disposed, but it is natural that two or more second stirring / conveying rollers 241 may be disposed.

<Description of Other Configuration Example 2 of Developer Detection Mechanism Unit>
11 and 12 are explanatory views showing another configuration example 2 of the developer detection mechanism section of the developing device 2 according to the present invention.

  This developer detection mechanism section has a crank shape in which a stainless shaft (bar-shaped weight member described in the claims) 101 having an outer diameter of 4 mm is decentered by 6 mm with respect to the drive rotation center R and fixedly supported on the rotation support members 104 and 105. It has become. In the figure, reference numeral 106 denotes a rotation shaft of the rotation support member 104, and reference numeral 17 denotes a rotation shaft of the rotation support member 105.

  Two coil springs 102 and a coil spring 103 having a wire diameter of 0.8 mm, an outer diameter of 8 mm, and a helical pitch (P) of 8 mm are inserted into the stainless steel shaft 101. The coil spring 102 is wound clockwise and the coil spring 103 is wound. Is formed in the left-handed winding direction.

  Further, if the effective length of the stainless steel shaft 101 is L1, the spring length of the coil spring 102 is L2, and the spring length of the coil spring 103 is L3, a total of about 5 mm [≈L1- (L2 + L3)] is provided, and the coil springs 102 and 103 are independently inserted in the radial direction and the thrust direction so as to freely move.

  As described above, since the coil spring 101 can move in the radial direction, the toner that causes solidification around the spiral is discharged while rotating without staying, and the development such as packing and solidification can be prevented and the development is highly reliable. Operation is possible. Furthermore, when the stainless shaft 101 is not provided when a load is applied by the toner in accordance with the rotation drive, the coil springs 102 and 103 are bent (bending) and come into contact with the inner wall of the case (not shown). According to the above structure, since the deformation is regulated by the stainless steel shaft 101, a highly reliable operation is possible. Furthermore, since the coil springs 102 and 103 are wound in the reverse direction, the developer in the developing tank is conveyed so as to gather, for example, from both ends toward the center, so that the developer in the developing tank has a powder pressure. It will be uniform and always leveled. Therefore, it is possible to maintain a good image quality and to detect the remaining amount of the developer with high accuracy without causing a detection error as in the prior art.

  Furthermore, both ends 102a and 102b of the coil spring 102 and both ends 103a and 103b of the coil spring 103 have a predetermined clearance with respect to the stainless steel shaft 101, and the spring wire is wound tightly. Such close winding prevents the end portions 102a and 103a of the two coil springs 102 and 103 from being inadvertently entangled with each other at the center. Further, when the other ends 102b, 103b of the coil springs 102, 103 are rubbed against a case inner wall (not shown), the case inner wall is prevented from being damaged.

1 is a schematic cross-sectional view showing a configuration of a digital color copying machine as a color image forming apparatus equipped with a developing device of the present invention. 1 is an enlarged schematic sectional view showing a developing device of the present invention. It is explanatory drawing which shows an example of the developer detection mechanism part of the developing device of this invention. It is explanatory drawing which shows the structure of a transmission mechanism part, (a) is a front view of a transmission rotation board, (b) is a side view of a transmission rotation board, (c) is a front view of a to-be-rotated board, (d) is to be covered. It is a side view of a rotating plate. It is explanatory drawing which shows a mode that a stirring conveyance roller rotates by a drive transmission member later on. The detection waveforms when the rotation of the agitating and conveying roller is detected by the rotation detector are shown. (A) shows the case with toner, and (b) shows the case without toner. It is explanatory drawing which shows the other Example of a detection board. The detection waveforms when the rotation of the agitating and conveying roller is detected by the rotation detector are shown. (A) shows the case with toner, and (b) shows the case without toner. It is a schematic sectional drawing which expands and shows the other structural example 1 of the image development apparatus of this invention. It is explanatory drawing which shows the other structural example 1 of the developer detection mechanism part of the developing device of this invention. It is explanatory drawing which shows the other structural example 2 of the developer detection mechanism part of the developing device of this invention. 11A is a view of the developer detection mechanism portion of FIG. 11 as viewed from the direction of arrow A, FIG. 11B is a cross-sectional view taken along line BB in FIG. 11, and FIG. 11C is a cross-sectional view taken along line CC in FIG. is there. It is explanatory drawing which shows an example of the developer detection mechanism part of the conventional developing device.

Explanation of symbols

2 Developing Device 3 Photosensitive Drum 20 Developing Tank 21 Developing Roller 22 Toner Supply Roller 23 Layer Pressure Suppression Blade 24 Stirring Conveying Roller 24a Rotating Shaft 24b Conveying Blade 24c Eccentric Shaft 25 Rotated Plate 25a Engaging Pin 26 Transmitting Rotating Plate 26a Engaging Piece 27 Drive transmission member 28 Rotation detector 28a Groove groove portion 28b, 28c Detection plate 101 Stainless steel shaft 102, 103 Coil spring 102a, 102b, 103a, 103b End portion 104, 105 Rotation support member 106, 107 Rotating shaft 241 Second agitation Transport roller R Drive rotation center P Spiral pitch

Claims (10)

A stirring and conveying member for agitating and conveying the developer was made weight distribution eccentric to the rotation center of the rotary shaft, a disjunction can drive transmission member for rotating the agitation conveying member, the rotation of the agitation conveying member and a rotation detector for detecting the state, in the developing device for detecting the remaining amount of the developer by rotating state detected by the rotation detector,
The eccentric weight distribution is made by a rod-like weight member that is eccentrically arranged and fixed with respect to the rotating shaft, and the stirring and conveying member is a coil spring having an inner diameter larger than an outer diameter of the weight member, A developing device , wherein the coil spring is rotatably inserted into a weight member .   The developing device according to claim 1, wherein the agitating and conveying member is disposed above the developer supply roller.   The developing device according to claim 1, wherein the agitating and conveying member agitates and conveys an internal developer from both ends of the agitating and conveying member toward a central portion.   The developing device according to claim 1, wherein the rotation detector generates a plurality of output pulses for one rotation of the stirring and conveying member.   The developing device according to claim 1, wherein one or a plurality of second agitating and conveying members different from the agitating and conveying member are arranged.   The developing device according to claim 5, wherein the second agitating and conveying member agitates and conveys the internal developer in a direction opposite to the agitating and conveying direction of the agitating and conveying member. The developing device according to claim 1, wherein the coil spring includes a plurality of separated members having different winding directions . The developing device according to claim 7, wherein the coil spring is inserted into the weight member with a clearance movable in a thrust direction . Said coil spring, a developing device according to 請 Motomeko 8 you wherein each both end portions are closely wound. The drive transmission member includes a disk-shaped rotated plate attached to one end of the rotating shaft, and a disk-shaped transmission rotating plate that transmits external force to the rotated plate. An engagement pin is provided at one location on the peripheral edge of the transmission rotating plate on the opposite surface side, and the transmission rotation plate is formed to protrude diagonally so as to pass through the rotation center on the opposite surface side of the rotated plate. Engagement pieces are provided,
In the rotation detector, a light emitting element and a light receiving element are arranged to face each other through a concave groove portion in a case body formed in a concave shape in cross section, and the concave groove portion is opened toward an axis of the rotation shaft. are arranged such that the rotating shaft which faces the opening of the groove portion, claim 1, wherein the sensing plate formed in a fan shape pass through the concave groove portion is al provided The developing device according to 1.

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