Sheet conveyance apparatus and image forming apparatus

A sheet conveyance apparatus for conveying a sheet, the sheet conveyance apparatus comprising:

• a conveyance roller configured to convey the sheet;
• a motor configured to drive the conveyance roller;
• a clutch unit configured to switch between a first state and a second state, wherein the first state is a state in which a driving force of the motor is transmitted to the conveyance roller, and the second state is a state in which the driving force of the motor is not transmitted to the conveyance roller;
• a phase determiner configured to determine a rotation phase of a rotor of the motor;
• a speed determiner configured to determine a rotation speed of the rotor;
• a detector configured to detect a driving current flowing through a winding of the motor;
• and
• a controller configured to control the driving current flowing through the winding of the motor so that a value of a torque current component of the driving current detected by the detector becomes a target value of the torque current component and to perform field weakening for reducing an intensity of a magnetic flux passing through the winding by controlling the driving current flowing through a winding of the motor so that a value of an exciting current component of the driving current detected by the detector becomes a target value of the exciting current component,
• wherein the torque current component is a current component that generates torque on the rotor and is expressed in a rotating coordinate system based on the rotation phase determined by the phase determiner, and the exciting current component is a current component that has an influence on the intensity of the magnetic flux passing through the winding and is expressed in the rotating coordinate system,
• wherein the controller sets the target value of the torque current component so as to reduce a deviation between an instructed speed representing a target speed of the rotor and the rotation speed determined by the speed determiner, and
• wherein, in a period in which the rotor rotates at a predetermined speed, the controller sets the target value of the exciting current component such that a degree of the field weakening in a first period after a first timing is greater than a degree of the field weakening in a second period before the first timing, wherein the first timing is earlier by first predetermined time than switching of the motor and the conveyance roller from the second state to the first state.

A sheet conveyance apparatus for conveying a sheet, the sheet conveyance apparatus comprising:

• a conveyance roller configured to convey the sheet;
• a motor configured to drive the conveyance roller;
• a clutch unit configured to switch between a first state and a second state, wherein the first state is a state in which a driving force of the motor is transmitted to the conveyance roller, and the second state is a state in which the driving force of the motor is not transmitted to the conveyance roller;
• a phase determiner configured to determine a rotation phase of a rotor of the motor;
• a detector configured to detect a driving current flowing through a winding of the motor;
• and
• a controller configured to control the driving current flowing through the winding of the motor so that a value of a torque current component of the driving current detected by the detector becomes a target value of the torque current component and to perform field weakening for reducing an intensity of a magnetic flux passing through the winding by controlling the driving current flowing through a winding of the motor so that a value of an exciting current component of the driving current detected by the detector becomes a target value of the exciting current component,
• wherein the torque current component is a current component that generates torque on the rotor and is expressed in a rotating coordinate system based on the rotation phase determined by the phase determiner, and the exciting current component is a current component that has an influence on the intensity of the magnetic flux passing through the winding and is expressed in the rotating coordinate system,
• wherein the controller sets the target value of the torque current component so as to reduce a deviation between an instructed phase representing a target phase of the rotor and the rotation phase determined by the phase determiner,
• wherein, in a period in which the rotor rotates at a predetermined speed, the controller sets the target value of the exciting current component at a first value, which is negative, for a first period after a first timing that is earlier by first predetermined time than switching of the motor and the conveyance roller from the second state to the first state, and sets the target value of the excitation current component at a second value,
• wherein the second value is greater than the first value, for a second period that is before the first timing, and
• wherein a direction of a magnetic flux generated because the value of the exciting current component is negative is opposite of a direction of a magnetic flux of the rotor.

A sheet conveyance apparatus for conveying a sheet, the sheet conveyance apparatus comprising:

• a conveyance roller configured to convey the sheet;
• a motor configured to drive the conveyance roller;
• a clutch unit configured to switch between a first state and a second state, wherein the first state is a state in which a driving force of the motor is transmitted to the conveyance roller, and the second state is a state in which the driving force of the motor is not transmitted to the conveyance roller;
• a phase determiner configured to determine a rotation phase of a rotor of the motor;
• a speed determiner configured to determine a rotation speed of the rotor;
• and
• a controller configured to control a driving current flowing through a winding of the motor so that a value of a torque current component of the driving current detected by a detector becomes a target value of the torque current component and to perform field weakening for reducing an intensity of a magnetic flux passing through the winding by controlling the driving current flowing through a winding of the motor so that a value of an exciting current component of the driving current detected by the detector becomes a target value of the exciting current component,
• wherein the torque current component is a current component that generates torque on the rotor and is expressed in a rotating coordinate system based on the rotation phase determined by the phase determiner, and the exciting current component is a current component that has an influence on the intensity of the magnetic flux passing through the winding and is expressed in the rotating coordinate system,
• wherein the controller sets the target value of the torque current component so as to reduce a deviation between an instructed speed representing a target speed of the rotor and the rotation speed determined by the speed determiner,
• wherein, in a period in which the rotor rotates at a predetermined speed, the controller sets the target value of the exciting current component at a first value, which is negative, for a first period after a first timing that is earlier by first predetermined time than switching of the motor and the conveyance roller from the second state to the first state, and sets the target value of the excitation current component at a second value,
• wherein the second value is greater than the first value, for a second period that is before the first timing, and
• wherein a direction of a magnetic flux generated because the value of the exciting current component is negative is opposite of a direction of a magnetic flux of the rotor.

A document reading apparatus for reading a document, the document reading apparatus comprising:

• a document tray on which a document is stacked;
• a conveyance roller configured to convey the document stacked on the document tray;
• a reading unit configured to read the document conveyed by the conveyance roller;
• a motor configured to drive a load;
• a clutch unit configured to switch between a first state and a second state, wherein the first state is a state in which a driving force of the motor is transmitted to the load, the second state is a state in which the driving force of the motor is not transmitted to the load;
• a phase determiner configured to determine a rotation phase of a rotor of the motor;
• a speed determiner configured to determine a rotation speed of the rotor;
• and
• a detector configured to detect a driving current flowing through a winding of the motor;
• and
• a controller configured to control the driving current flowing through the winding of the motor so that a value of a torque current component of the driving current detected by the detector becomes a target value of the torque current component and to perform field weakening for reducing an intensity of a magnetic flux passing through the winding by controlling the driving current flowing through a winding of the motor so that a value of an exciting current component of the driving current detected by the detector becomes a target value of the exciting current component,
• wherein the torque current component is a current component that generates torque on the rotor and is expressed in a rotating coordinate system based on the rotation phase determined by the phase determiner, and the exciting current component is a current component that has an influence on the intensity of the magnetic flux passing through the winding and is expressed in the rotating coordinate system,
• wherein the controller sets a target value of the torque current component so as to reduce a deviation between an instructed speed representing a target speed of the rotor and the rotation speed determined by the speed determiner, and
• wherein, in a period in which the rotor rotates at a predetermined speed, the controller sets the target value of the exciting current component such that a degree of the field weakening in a first period after a first timing is greater than a degree of the field weakening in a second period before the first timing, wherein the first timing is earlier by first predetermined time than switching of the motor and the conveyance roller from the second state to the first state.

An image forming apparatus for forming an image on a print target medium, the image forming apparatus comprising:

• a conveyance roller configured to convey the print target medium;
• an image forming unit configured to form an image on the print target medium conveyed by the conveyance roller;
• a motor configured to drive a load;
• a clutch unit configured to switch between a first state and a second state, wherein the first state is a state in which a driving force of the motor is transmitted to the load, the second state is a state in which the driving force of the motor is not transmitted to the load;
• a phase determiner configured to determine a rotation phase of a rotor of the motor;
• a speed determiner configured to determine a rotation speed of the rotor;
• and
• a detector configured to detect a driving current flowing through a winding of the motor;
• and
• a controller configured to control the driving current flowing through the winding of the motor so that a value of a torque current component of the driving current detected by the detector becomes a target value of the torque current component and to perform field weakening for reducing an intensity of a magnetic flux passing through the winding by controlling the driving current flowing through a winding of the motor so that a value of an exciting current component of the driving current detected by the detector becomes a target value of the exciting current component,
• wherein the torque current component is a current component that generates torque on the rotor and is expressed in a rotating coordinate system based on the rotation phase determined by the phase determiner, and the exciting current component is a current component that has an influence on the intensity of the magnetic flux passing through the winding and is expressed in the rotating coordinate system,
• wherein the controller sets a target value of the torque current component so as to reduce a deviation between an instructed speed representing a target speed of the rotor and the rotation speed determined by the speed determiner, and
• wherein, in a period in which the rotor rotates at a predetermined speed, the controller sets the target value of the exciting current component such that a degree of the field weakening in a first period after a first timing is greater than a degree of the field weakening in a second period before the first timing, wherein the first timing is earlier by first predetermined time than switching of the motor and the conveyance roller from the second state to the first state.