Canon Kabushiki Kaisha

Mitsubishi Denki Kabushiki Kaisha

Takanori Iida

Yusuke Ishida

Tomoyuki Sakamaki

Yasushi Takeuchi

Toshiyuki Yamada

Hisashi Tsukijima

Katsuya Nose

Toshiya Kobayashi

Yuta Okuyama

Masashi Wakisaka

Shiro Higashikozono

Hiroto Kakinuma

Shinya Suzuki

Taisuke Matsuura

Osamu Ariizumi

Satoru Stephen Yamauchi

Koji Arimura

Ryohei Terada

Masahiro Ootsuka

Daisuke Makino

Ichiro Katsuie

Shoji Naruge

Takayuki Ganko

Mitsue Takamori

Akio Kirimura

Tadamitsu Isonaka

Jun Nosaka

Kouichi Katsumi

Chiaki Nobuoka

An image forming apparatus includes a permeability sensor configured to detect information on magnetic permeability of developer contained in a developer container for detecting toner density of the developer, and a controller configured to control a control voltage applied to the permeability sensor so that (i) a value of the control voltage that is applied to the permeability sensor in a case where a predetermined condition including a condition that the toner density of the developer contained in the developer container is a predetermined density is satisfied and an amount of the developer contained in the developer container is a first amount is greater than (ii) a value of the control voltage applied to the permeability sensor in a case where the predetermined condition is satisfied and the amount of the developer contained in the developer container is a second amount greater than the first amount.

Image forming apparatus having toner density control

An image forming apparatus includes a control portion, and in a first period from when use of a developing apparatus is started until when an amount of developer in a developing device reaches a predetermined amount larger than an amount of initial developer, when an amount of developer supplied from a supplying portion through a single supplying operation in an image forming operation is larger than a predetermined supplied amount, the control portion interrupts the image forming operation and drives a conveyance portion for a predetermined time. In a second period after the amount of the developer reaches the predetermined amount, when an amount of the supplying developer supplied through a single supplying operation in the image forming operation is larger than the predetermined supplied amount, the control portion continues the image forming operation without interruption.

Image forming apparatus having image formation interruption

A developing device includes a developing container, a developing sleeve, a magnet and grooves provided at a surface of the sleeve and formed along a direction crossing a circumferential direction of the sleeve. In a cross-section, each of the grooves is formed by a flat bottom portion contacting a carrier particle and a pair of side surface portions provided in both sides of the flat bottom portion with respect to the circumferential direction of the sleeve and satisfies the following relationship:&#x3c;22&#xd7;, and/2&#x2264;&#x3c;2 In the above, r is a volume-average particle size of the carrier particles, w is a length of the flat bottom portion, L is a width between the side surface portions at the surface of the sleeve, and s is a depth of each of the grooves.

Developing device

A developer circulated between first and second chambers in a function separation type development device including a developer discharge portion is prevented from being excessively discharged from the developer discharge portion. The developer discharge portion is disposed in the first chamber and is provided downstream of a region on a developer bearing member in the direction in which the developer in the first chamber is conveyed, the region corresponding to a maximum image region formable on an image bearing member.

Development device

A developing device includes a developing container, a rotatable member including a first screw portion and a second screw portion, a first feeding path configured to accommodate the first screw portion, a second feeding path provided in communication with the first feeding path at a position downstream of the second screw portion with respect to a develop feeding direction, and a developer discharging opening provided in the second feeding path. In a state in which the developing device is mounted to the image forming apparatus, in a cross section of the second feeding path perpendicular to a rotational axis of the rotatable member, the second feeding path includes a region where a distance between side surfaces of the second feeding path in a side above a center of a rotation shaft of the rotatable member with respect to a vertical direction increases upwardly.

In the present invention, an image forming apparatus using a method of replacing a developer is configured such that an immobile area in which the heights of a discharge passage and a conveyance passage are changed on the upstream side of a returning screw is filled. This causes the immobile area of the developer to be unlikely to occur and accordingly suppresses formation of a toner stain image due to an aggregation toner, enabling stable image formation over a long period of time.

Developing device and conveying screw for developing an electrostatic latent image on an image bearing member

When ending image forming, a state is realized where charging by a charging roller is stopped (charging bias off) and also applying DC voltage at a developing device is stopped (developing bias DC off). In this state, AC voltage is applied to the developing device (developing bias AC on), thereby adhering toner to the surface of a photosensitive drum and forming interposing toner. Driving of the photosensitive drum and an intermediate transfer belt is then stopped in the state with the interposing toner interposed between the photosensitive drum and intermediate transfer belt.

Image forming apparatus to suppress excessive interposing toner

A developing apparatus includes a developing container containing a developer and a stirring-conveying screw configured to feed the developer. The stirring-conveying screw includes a first feeding screw portion to feed the developer in a first direction, a second feeding screw portion to feed the developer in an opposite direction, and a third feeding screw portion. A first feeding passageway accommodates parts of the feeding screw portions, and a second feeding passageway is provided in fluid communication with the first feeding passageway. A bottom surface portion is disposed proximate to the communication opening and has a first portion provided at a position higher than a bottom surface of the second feeding screw and a second portion provided at a position lower than a bottom-most portion of the communication opening. The bottom surface portion is located downstream of the second feeding screw and faces the third feeding screw.

Developing apparatus

A developing device includes a developing container, a developing sleeve, a magnet and grooves provided at a surface of the sleeve and formed along a direction crossing a circumferential direction of the sleeve. In a cross-section, each of the grooves is formed by a flat bottom portion contacting a carrier particle and a pair of side surface portions provided in both sides of the flat bottom portion with respect to the circumferential direction of the sleeve and satisfies the following relationship:22&#xd7;and2&#x2266;&#x3c;2 In the above, r is a volume-average particle size of the carrier particles, w is a length of the flat bottom portion, L is a width between the side surface portions at the surface of the sleeve, and s is a depth of each of the grooves.

A developing apparatus, includes a developer carrying member; a containing portion configured to contain developer; a discharge outlet through which a surplus of the developer is discharged; a first conveying portion configured to convey the developer; a second conveying portion provided downstream of the first conveying portion in a conveying direction of the first conveying portion and having a spiral blade portion configured to convey the developer in a conveying direction opposite to the conveying direction of the first conveying portion; and a disk portion provided upstream of the second conveying portion in the conveying direction of the second conveying portion, the disk portion being formed to project radially-outwardly from a whole circumference of a rotary shaft. An upstream end of the spiral blade portion of the second conveying portion in the conveying direction of the second conveying portion and the disk portion are arranged with an interval therebetween.

Developing apparatus having supply device with compound spiral portions

A developing apparatus includes a developer carrying member configured to carry a developer, and a magnet member disposed inside the developer carrying member. The magnet member includes one or more first magnet portions having a first magnetic polarity at an outer surface thereof opposing an inner surface of the developer carrying member, and one or more second magnet portions having a second magnetic polarity at an outer surface thereof opposing the inner surface. In a cross-section perpendicular to a longitudinal direction of the magnet member at a longitudinally central portion thereof, a number of the first magnet portions is larger than a number of the second magnet portions, and a ratio of a total area of the first magnet portions in the cross-section is smaller at a longitudinally end portion of the magnet member than at the longitudinally central portion.

A developing device includes a developer carrying member and first and second chambers. A feeding member provided in the second chamber includes a normal feeding portion, a reverse feeding portion, and a discharging portion. An opposing portion in the second chamber opposes a peripheral surface of the reverse feeding portion and is formed so that a first region of an upper half of the reverse feeding portion is broader in clearance with the second chamber than a second region, and includes a projected portion for forming a predetermined clearance with the reverse feeding portion by being projected from a side surface of the second chamber in a horizontal direction. The projected portion is disposed higher than a rotation center of the reverse feeding portion and lower than a top of the reverse feeding portion and is more remote from the first chamber than a rotation center of the feeding member.

A developing apparatus includes a developing container for containing a developer comprising toner and carrier and first and second rotatable feeding members configured to feed the developer. The first feeding member includes a rotatable shaft, a first helical blade portion provided around the rotatable shaft and configured to feed the developer, and a second helical blade portion provided around the rotatable shaft at a position downstream of the first helical blade portion. The second helical blade portion has a helix which is opposed to that of the first helical blade portion. In addition, a disk portion is provided on the rotatable shaft at a position between the first helical blade portion and the second helical blade portion.

Developing apparatus with discharge regulating member

A development device wherein a magnetic force distribution of a developer bearing member in a longitudinal direction at positions at which a magnetic flux density of a low magnetic field area is minimal in the peripheral direction of the developer bearing member is set such that a difference between a maximum magnetic flux density in a range from a maximum position at which an attenuation rate of the magnetic flux density is maximal to a 30 mm distant position toward the center of the developer bearing member and a magnetic flux density on a further center side of the developer bearing member than the range is 3 mT or less, and an absolute value of the magnetic flux density of a further outer side in the longitudinal direction of the developer bearing member than the maximum position is set to 3 mT or less.

Growing community of inventors

Noda, Japan

Takanori Iida