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US 8,558,858 B2Granted
Image forming apparatus
AssigneeBrother Kogyo Kabushiki Kaisha
InventorIsao Kubo
Life of this patent
Estimating the term…
Abstract
An image forming apparatus includes: a light source that emits a light beam; a photosensitive member; a brushless motor including a stator where a plurality of coils are placed and a rotor where a plurality of magnets are placed; a rotary polygon mirror, which is rotated by the brushless motor, and which periodically deflects the light beam emitted from the light source to sequentially form scanning lines on the photosensitive member; an energization switching unit that turns on and off energizations of the coils; a voltage detecting unit that outputs a detection signal based on induced voltages that are generated in the coils by rotation of the rotor; and a control unit that controls turning on/off of the energizations by the energization switching unit based on the detection signal.
Claims10
An image forming apparatus comprising:
- a light source configured to emit a light beam;
- a photosensitive member;
- a brushless motor comprising a stator where a plurality of coils are placed and a rotor where a plurality of magnets are placed;
- a rotary polygon mirror, which is configured to be rotated by the brushless motor, and which is configured to periodically deflect the light beam emitted from the light source to sequentially form scanning lines on the photosensitive member;
- an energization switching unit configured to turn on and off energizations of the coils;
- a voltage detecting unit configured to output a detection signal based on induced voltages that are generated in the coils by rotation of the rotor;
- a control unit configured to:
- control the energization switching unit to turn on and off the energizations of the coils based on the detection signal;
- and
- perform a chopping control on the energization switching unit during an energization-on time for the plurality of coils;
- and
- a sensor configured to receive the light beam deflected by the rotary polygon mirror and to output a light receiving signal,
- wherein the plurality of coils are connected via a star connection,
- wherein the voltage detecting unit is connected to a neutral point of the star connection and an end point of each coil of the plurality of coils different from the neutral point and is configured to output a signal, which is based on a difference in potential between the neutral point of the star connection and the end point of each coil of the plurality of coils different from the neutral point, as the detection signal,
- wherein, in a start-up process of the brushless motor, the control unit is configured to execute a rotation speed control of the brushless motor based on the detection signal, and
- wherein, in a stabilized time period during which a rotation speed of the brushless motor is within a target speed range, the control unit is configured to execute a rotation speed control of the brushless motor based on the light receiving signal and to increase a frequency of the chopping control to a frequency greater than a frequency in the rotation speed control of the brushless motor based on the detection signal.
13 more elements
An image forming apparatus comprising:
- a light source configured to emit a light beam;
- a photosensitive member;
- a brushless motor comprising a stator where a plurality of coils are placed and a rotor where a plurality of magnets are placed;
- a rotary polygon mirror, which is configured to be rotated by the brushless motor, and which is configured to periodically deflect the light beam emitted from the light source to sequentially form scanning lines on the photosensitive member;
- an energization switching unit configured to turn on and off energizations of the coils;
- a voltage detecting unit configured to output a detection signal based on induced voltages that are generated in the coils by rotation of the rotor;
- a control unit configured to:
- control the energization switching unit to turn on and off the energizations of the coils based on the detection signal;
- and
- perform a chopping control on the energization switching unit during an energization-on time for the plurality of coils;
- and
- a sensor configured to receive the light beam deflected by the rotary polygon mirror and to output a light receiving signal,
- wherein the control unit is further configured to:
- execute a rotation speed control of the brushless motor based on the light receiving signal when driving the light source to emit the light beam;
- execute a rotation speed control of the brushless motor based on the detection signal when not driving the light source;
- and
- increase a frequency of the chopping control in the rotation speed control of the brushless motor based on the light receiving signal to a frequency greater than a frequency in the rotation speed control of the brushless motor based on the detection signal.
14 more elements
An image forming apparatus comprising:
- a light source configured to emit a light beam;
- a photosensitive member;
- a brushless motor comprising a stator where a plurality of coils are placed and a rotor where a plurality of magnets are placed;
- a rotary polygon mirror, which is configured to be rotated by the brushless motor, and which is configured to periodically deflect the light beam emitted from the light source to sequentially form scanning lines on the photosensitive member;
- an energization switching unit configured to turn on and off energizations of the coils;
- a voltage detecting unit configured to output a detection signal based on induced voltages that are generated in the coils by rotation of the rotor;
- a control unit configured to:
- control the energization switching unit to turn on and off the energizations of the coils based on the detection signal;
- and
- perform a chopping control on the energization switching unit during an energization-on time for the plurality of coils;
- and
- a sensor configured to receive the light beam deflected by the rotary polygon mirror and to output a light receiving signal,
- wherein, in a start-up process of the brushless motor, the control unit is configured to execute a rotation speed control of the brushless motor based on the detection signal, and
- wherein, in a stabilized time period during which a rotation speed of the brushless motor is within a target speed range, the control unit is configured to execute a rotation speed control of the brushless motor based on the light receiving signal and to increase a frequency of the chopping control to a frequency greater than a frequency in the rotation speed control of the brushless motor based on the detection signal.
11 more elements
Dependencies are inferred from the claim text.