Toner residual amount detecting mechanism

Abstract: The toner residual amount detecting mechanism comprises a stirring shaft, a guide pin disposed on the central portion of the stirring shaft crossing the stirring shaft at right angles thereto, a rotor having a C-shape in cross section and extending in the axial direction of the stirring shaft, the rotor having a slot provided in the circumferential direction of the central portion thereof, the slot being freely engaged with one end of the guide pin so as to constitute a turning pair together with the stirring shaft, a reset spring extending in the axial direction of the stirring shaft and having both ends respectively slidably held by both ends of the rotor and a central portion which brings into contact with the peripheral surface of the other end of the guide pin so as to bias the rotor and cause one end of the slot to bring into contact with one end of the guide pin, and an actuator having one end fixed to a sensor shaft which is rotatably supported in parallel with the stirring shaft and another end extending toward the stirring shaft so as to cross the stirring shaft and being in contact with the central portion of the rotor.

Description: BACKGROND OF INVENTION 1. Field of the Invention: The present invention relates to a developing device used in a electrophotographic recording apparatus, particularly to a toner residual amount detecting mechanism of the same. 2. Description of the Related Art: Conventionally some developing devices used in the electrophotographic apparatus are provided with a toner residual detecting mechanism, which rotates a supported stirring shaft extending in the longitudinal direction of a hopper which stores therein toner supplied thereto, transmits the resistance of the residual toner to the rotor provided on the stirring shaft, and detects the operation of the rotor by a photosensor. For example, such a typical developing device is disclosed in a maintenance manual entitled "Laser Line ™ 6 elite" pp 3-21 to 22, published by Oki Electric Industry Co., Ltd. in January 1988. This developing device will be described hereinafter with reference to drawings. Fig. 2 is a cross-sectional view of toner residual amount detecting mechanism of the developing device. The developing device 1 comprises a hopper portion 3 for storing toner 2 supplied thereto, a developing roller 5, a supply roller 6, and a stirring shaft 7 which extend in the longitudinal direction of the portion 3 and rotatably supported by both side portions of a frame 4, and a blade portion 8 which extends along the surface of the developing roller 5 in the axial direction thereof. The developing roller 5, the supply roller 6 and the stirring shaft 7 each have one end extending out of one side portion of the frame 4 and being connected to a gear. Each of the gears meshes an intermittent gear, not shown, to thereby form a chain of gears. As illustrated in Fig. 3A, the gear 11 coupled to the stirring shaft 7 has a stepped portion 11a and contacts a rotor 12 which rotates together with the gear 11. The stepped portion 11a and the rotor 12 have substantially the same radius. The stirring shaft 7 is fixed to the rotor 12 at one end thereof and the gear 11 is rotatable relative to the stirring shaft 7. The gear 11 and the rotor 12 can be rotatable relative to each other by engaging a stopper 15 provided on the gear 11 into a long slit 14 provided in the rotor 12 and engaging a protrusion 16 provided on the rotor 12 into a long slit 13 provided in the gear 11 wherein the long slits 13 and 14 are arc-shaped relative to the centers of the gear 11 and the rotor 12. An extension spring 18 stretches across a protrusion 17 provided on the gear 11 and the protrusion 16 provided on the rotor 12 so that the stopper 15 of the gear 11 is brought into contact with one end of the long slit 14. At this state, the concave portion 19 provided on the gear 11 is positioned to overlap the concave portion 20 provided on the rotor 12. The developing roller 5 contacts a photoconductor drum 22 as illustrated in a two dot chain line in Fig. 2. The stirring shaft 7 has a stirring device 21 before the toner 2 in the hopper portion 3 for preventing the toner 2 lumps in the hopper portion 3. Figs. 3A and 4A show the state where the toner 2 is stored in the hopper portion 3 while Figs. 3B and 4B show the state where the toner 2 is not stored in the hopper portion 3. A sensor lever 23 has a fulcrum 24 at one end thereof, an extension spring 25 provided at the other end thereof and a convex portion 23a provided at the substantially central portion thereof. The convex portion 23 of the sensor lever 23 contacts the stepped portion 11a and the outer periphery of the rotor 12 by resiliency of the extension spring 25. A protrusion 23b of the sensor lever 23 is retained by a microswitch 26 provided in the developing device. An operation of the developing device will be described hereinafter. Since the gear of the developing roller 5 meshes a gear, not shown, for driving the photoconductor drum 22, the developing roller 5, the supply roller 6 and the stirring shaft 7 are rotated in the directions of the arrows B, B and D when the photoconductor drum 22 rotates in the direction of the arrow C. The toner 2 charged with electricity on the surface of the developing roller 5 is uniformly layered and attached thereon by the blade 8. The toner 2 adheres to an electrostatic latent image formed on the photoconductor drum 22 which rotates at the constant speed in the direction of the arrow C and visualize the electrostatic latent image. At this time, the stirring device 21 rotates together with the stirring shaft 7 in the direction of the arrow D so that the toner 2 is conveyed to the supply roller 6 and it stirs the toner 2 for preventing the toner 2 from lumping therein. When the residual amount of the toner 2 is sufficiently large in the hopper portion 3, the resistance of the toner 2 applied to the stirring device 21 is high so that the extension spring 18 stretches as illustrated in Fig. 4A in which the rotary force of the gear 11 is transmitted to the rotor 12 to thereby rotate the stirring shaft 7 in the direction of the arrow D while the other end of the long slit 14 of the rotor 12 is in contact with the stopper 15 of the gear 11. At this time, since the concave portion 20 of the gear 11 does not overlap the concave portion 19 of the rotor 12, the sensor lever 23 does not turn so that the microswitch 26 attached to the developing device does not operate. When the residual amount of the toner 2 stored in the hopper portion 3 is small, the resistance of the toner 2 acting on the stirring device 21 becomes weak. The extension spring 18 contracts and transmits the rotary force of the gear 11 to the rotor 12 while one end of the long slit 14 of the rotor 12 is in contact with the stopper 15 of the gear 11 as illustrated in Fig. 4B. As a result, the stirring shaft 7 is rotated in the direction of the arrow D. At this time, the concave portion 20 of the gear 11 overlaps the concave portion 19 of the rotor 12 so that the sensor lever 23 turns when the convex portion 23a of the same enters the concave portions 19 and 20 whereby the protrusion 23b of the sensor lever 23 operates the microswitch 26. In the series of the operations, the residual amount of the toner 2 in the hopper portion 3 is detected. However, there is the following drawback in the conventional toner residual amount detecting mechanism. That is, when the resistance of the toner to the stirring device is sufficiently high, the extension spring stretches to thereby cause the stopper provided on the gear to be brought into contact with the other end of the long slit provided in the rotor whereby the microswitch does not operate. On the contrary, when the resistance of the toner to the stirring device is low, there occurs an unstable situation where the extension spring contracts so that the stopper provided on the gear is brought into contact with neither one end nor the other end of the long slit provided in the rotor. Resistance received from the toner is varied in proportion to the depth to which the stirring device enters toner, the stopper vibrates in the long slit in such a situation. At this time, the concave portions of both the gear and the rotor overlap each other to thereby operate the sensor lever. SUMMARY OF THE INVENTION It is an object of the present invention to provide a toner residual amount detecting mechanism capable of performing a stable detecting operation even if the resistance of the toner is low to thereby inform an operator a correct toner supply time. To achieve the same object, the toner residual amount detecting mechanism according to the present invention comprises a stirring shaft, a guide pin disposed on the central portion of the stirring shaft crossing the stirring shaft at right angles thereto, a rotor having a C-shape in cross section and extending in the axial direction of the stirring shaft, the rotor having a slot provided in the circumferential direction of the central portion thereof, the slot being freely engaged with one end of the guide pin so as to constitute a turning pair together with the stirring shaft, a reset spring extending in the axial direction of the stirring shaft and having both ends respectively slidably held by both ends of the rotor and having a central portion contacting the peripheral surface of the other end of the guide pin so as to bias the rotor in a direction to cause one end of the slot to come into contact with one end of the guide pin, and an actuator having one end fixed to a sensor shaft which is rotatably supported in parallel with the stirring shaft and another end extending toward the stirring shaft and being in contact with the central portion of the rotor. When the toner remains in the hopper portion, the rotor rotated together with the stirring shaft receives the resistance from the toner and rotates against the resiliency of the reset spring until it is contacted with the one end of the slot along the one end of the guide pin. At this time, the other end of the guide pin is positioned on the chord side of the crescent-shaped rotor. Since the other end of the actuator is brought into contact with the rotor and the other end of the guide pin during one revolution of the stirring shaft, the actuator cannot turn so that the sensor shaft coupled to the actuator cannot turn on or off the photosensor. Meanwhile, when the hopper portion is empty of the toner, the rotor does not turn since it does not receive the resistance from the toner, whereby the guide pin is in parallel with the chord of the crescent-shaped rotor. When the other end of the actuator is positioned at the chord side of the crescent-shaped rotor, the rotor turns so that the sensor shaft coupled to the actuator turns on or off the photosensor since the actuator is not impeded in the turning thereof by the rotor and the guide pin. Accordingly, it is possible to detect the toner supply time. According to the invention, since the spring can stretch in the axial direction of the stirring shaft, the spring constant can be set in conformity with the resistance of the toner. As a result, it is possible to provide the toner residual amount detecting mechanism capable of performing the stable operation. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view showing the structure of a developing device including a toner residual amount detecting mechanism according to the present invention; Fig. 2 is a cross-sectional view showing the structure of a conventional developing device; Figs. 3A and 3B are views showing the operation of the photosensor of the conventional toner residual amount detecting mechanism; Figs. 4A and 4B are views showing the relation between the sensor lever of the conventional toner residual amount detecting mechanism and the rotor of the same; Fig. 5 is a perspective view showing a schematic arrangement of the main portion of a toner residual amount detecting mechanism according to an embodiment of the present invention; Fig. 6 is a perspective view showing the structure of a sensor member viewed in the direction of the arrow K in Fig. 5; Figs. 7A to 7D are views showing the operation of the toner residual amount detecting mechanism when the toner hopper portion is full of the toner; Figs. 8A to 8C are views showing the operation of the toner residual amount detecting mechanism when the toner hopper portion is empty of the toner; and Fig. 9 is a perspective view showing a modified actuator. DESCRIPTION OF THE PREFERRED EMBODIMENT A toner residual amount detecting mechanism according to the present invention will be described with reference to Fig. 1 and Figs. 5 to 9. Fig. 1 is a perspective view showing the structure of a developing device provided with a toner residual amount detecting mechanism according to the present invention. In Fig. 1, a developing device 1 comprises a developing roller 5, gears 9 and 10, a stirring device 30 for stirring toner 2 stored in the hopper portion to prevent the toner 2 from lumping and a photo sensing mechanism 70 (not shown precisely in shape). As illustrated in Fig. 1, the toner residual amount detecting mechanism is attached to one end of the developing apparatus 1. Fig. 5 is a perspective view showing a schematic arrangement of the main portion of the toner residual amount detecting mechanism according to the second embodiment of the present invention. A sensor shaft 53 is rotatably supported by the side portion of the frame 4 and disposed in parallel with the stirring shaft 7. A guide pin 51 penetrates the central portion of the stirring shaft 7 so as to make a cross. A sensor member 50 as a rotor is turnably provided at the central portion of the stirring shaft 7 while the guide pin 51 serves as the guide for the sensor member 50. A reset spring 52 has both ends slidably supported by both ends of the rotor 50 and a central flexible portion which is in contact with one end 51a of the guide pin 51. That is, when the rotor 50 turns in the direction of the arrow I, the reset spring 52 twists and flexes so as to return the rotor 50 in the direction of the arrow J. An actuator 54 has one end 54a which is fixed to the sensor shaft 53 and the other end 54b which is in contact with the central portion of the rotor 50. A sensor lever 60 is fixed to one end of the center shaft 53 which extends out of the hopper and turns on and off a photosensor 61 in response to the rotation of the actuator 54. Fig. 6 is a perspective view of the rotor 50 as viewed from the direction of the arrow K in Fig. 5. The rotor 50 includes a central portion 55, both ends 56 and 57 and arms 58. The arms 58 for coupling the central portion 55 with the both ends 56 and 57 are disposed symmetrically with each other relative to the stirring shaft 7. The central portion 55 and both ends 56 and 57 have C-shapes in cross section. A slot 59 is provided at the central portion 55 so as to guide rotatably the other end 51b of the guide pin 51. The central portion 55 constitute a turning pair together with the stirring shaft 7. The other end 51b of the guide pin 51 is brought into contact with one end 59a of the slot 59 when it is reset by resiliency of the reset spring 52. When the rotor 50 is rotated together with the stirring shaft 7, it receives the resistance of the toner so that the other end 51b of the guide pin 51 is brought into contact with the other end 59b of the slot 59. An operation of the embodiment will be described hereinafter. Figs. 7A to 7D are views showing the operation of the mechanism when the hopper portion is full of the toner and the rotor turns half in the direction of the arrow J. Fig. 7A shows the state where the other end 54b of the actuator 54 is in contact with the other end 51b of the guide pin 51 so that the photosensor 61 is OFF. Fig. 7B shows the state where the other end 54b of the actuator 54 is in contact with the rotor 50. Fig. 7C shows the state where the other end 54b of the actuator 54 is in contact with one end 51a of the guide pin 51. A two dot chain line shows that the other end 54b of the actuator 54 is in the state as illustrated in Fig. 7B. Fig. 7D shows the state where the other end 54b of the actuator 54 is in contact with one end 51a of the guide pin 51. Successively, the other end 54b of the actuator 54 is in contact with a circular portion of the rotor 50 and thereafter returns to the state as illustrated in Fig. 7A. That is, since the other end 54b of the actuator 54 does not turn to reach the bottom dead point, the sensor shaft 53 does not turn ON the photosensor 61. Figs. 8A to 8C are views showing the operation of the mechanism that when the toner hopper portion is empty of the toner, the rotor turns half in the direction of the arrow J. Fig. 8A shows the same state as that in Fig. 7A. Fig. 8B shows the state where the other end 54b of the actuator 54 turns to reach the bottom dead point to thereby turn ON the photosensor 61. Fig. 8C shows the state where the actuator 54 which had turned to reach the bottom dead center was again brought into contact with one end 51a of the guide pin 51 and thereafter has returned to the position as illustrated in Fig. 8A. Thereafter, the other end 54b of the actuator 54 is brought into contact with the circular portion of the rotor 50 and returns to the state as illustrated in Fig. 8A. The rotor according to the embodiment operates not only to detect the residual amount of the toner but to stir the toner. Modification of Embodiment (Fig. 9): According to the embodiment, the width of the actuator is substantially same as the width of the central portion of the rotor. However, a stirring bar 63 may be provided at the other end 62b of an actuator 62 which is arranged over the whole length of the rotor member as illustrated in Fig. 9. In this case, when the actuator 62 moves up and down in accordance with the rotation of the rotor, the stirring bar 63 collapses the toner located adjacent to the rotor 50 whereby the toner is prevented from hollowing around the periphery of the rotor 50.

Claims: A toner residual amount detecting mechanism comprising: a stirring shaft (7), a guide pin (51) disposed on the stirring shaft so as to make a cross therewith; a rotor (50) having a C-shape in cross section and extending in the axial direction of the stirring shaft (7), the rotor having a slot (59) provided in the circumferential direction of the central portion (55) thereof, the slot being freely engaged with one end (51b) of the guide pin (51) so as to constitute a turning pair together with the stirring shaft (7); a reset spring (52) extending in the axial direction of the stirring shaft and having both ends respectively slidably held by both ends of the rotor (50) and having a central portion contacting the peripheral surface of the other end (51a) of the guide pin (51) so to bias the rotor in a direction to cause one end (59a) of the slot to come into contact with one end of the guide pin; and an actuator (54, 62) having one end (54a) fixed to a sensor shaft (53) which is rotatably supported in parallel with the stirring shaft (7) and another end (54b) extending toward the stirring shaft (7) and being in contact with the central portion (55) of the rotor. A toner residual amount detecting mechanism according to claim 1, wherein the rotor (50) has the central portion (55) and both ends (56, 57) which are respectively C-shaped in cross section and coupled with one another by plate-shaped arms (58) while the stirring shaft (7) intervenes between the plate-shaped arms. A toner residual amount detecting mechanism according to claim 1 or 2, wherein the actuator (62) has a stirring bar (63) at the other end thereof, the length of the stirring bar being equivalent to that of the rotor (50).

Inventors: KIKUCHI HIROSHI, MOMIYAMA YOSHIHARU, NAKAJIMA SHIGEKI, OTA YUKIO, TAKANO MASATO, KIKUCHI, HIROSHI, MOMIYAMA, YOSHIHARU, NAKAJIMA, SHIGEKI, OTA, YUKIO, TAKANO, MASATO, Kikuchi, Hiroshi , c/o Oki Electr.Ind.Co.Ltd., Momiyama, Yoshiharu, c/o Oki Electr.Ind.Co.Ltd., Nakajima, Shigeki, c/o Oki Elec. Ind. Co. Ltd., Ota, Yukio, c/o Oki Electr.Ind.Co.Ltd., Takano, Masato, c/o Oki Electr.Ind.Co.Ltd.
Applicants: OKI ELECTRIC IND CO LTD, OKI ELECTRIC INDUSTRY CO., LTD.
Application year: 1992
Main classification: G03G15
IPC codes: G03G15