Cam drive device and image forming apparatus incorporating same

Patent metadata

Field	Value
Publication number	US-10401764-B2
Application number	US-201715832900-A
Country	US
Kind code	B2
Filing date	Dec 6, 2017
Priority date	Dec 9, 2016
Publication date	Sep 3, 2019
Grant date	Sep 3, 2019

Abstract

A cam drive device includes a cam to rotate; a displacement body to be displaced in response to a change in a rotation position of the cam in contact with the displacement body; a motor to rotate the cam; and a power source to output an electric current to be supplied to the motor. An electric current to cause a stall torque to the motor being a stop state is changed in response to a change in a rotation stop position of the cam.

First claim

What is claimed is:

1. A cam drive device comprising:
an eccentric cam configured to rotate, the eccentric cam including a first portion and a second portion, the second portion having a different curvature from the first portion;
a displacement body configured to displace in response to a change in a rotation position of the eccentric cam in contact with the displacement body;
a motor configured to rotate the eccentric cam; and
a power source configured to output an electric current to be supplied to the motor, wherein
an electric current configured to cause a stall torque to the motor being a stop state is changed in response to a rotation stop position of the eccentric cam changing between a first rotation stop position associated with the first portion of the eccentric cam and a second rotation stop position associated with the second portion of the eccentric cam such that the electric current at the first rotation stop position is less than the electric current at the second rotation stop position.

2. The cam drive device according to claim 1 , wherein
the first portion is a concentric curved portion in which a curvature centered on an axis of the eccentric cam is constant,
the second portion is a non-concentric curved portion in which the curvature centered on the axis of the eccentric cam is not constant, and
wherein the electric current is changed between the first rotation stop position of the eccentric cam and the second rotation stop position of the eccentric cam, the first rotation stop position at which the concentric curved portion is in contact with the displacement body, the second rotation stop position at which the non-concentric curved portion is in contact with the displacement body.

3. The cam drive device according to claim 2 , wherein the second rotation stop position includes:
a small-radius position at which a small radius portion of the non-concentric curved portion is in contact with the displacement body; and
a large-radius position at which a large radius portion of the non-concentric curved portion is in contact with the displacement body, the large radius portion larger in radius of curvature than the small radius portion,
wherein the electric current when the eccentric cam is at the small-radius position is set smaller than the electric current when the eccentric cam is at the large-radius position.

4. The cam drive device according to claim 2 , wherein the electric current configured to rotate the eccentric cam by driving of the motor is smaller than the electric current when the eccentric cam is at the first rotation stop position.

5. The cam drive device according to claim 1 , further comprising:
a controller configured to control the electric current such that the electric current at the first rotation stop position is less than the electric current at the second rotation stop position.

6. An image forming apparatus comprising:
an image forming device configured to form a toner image on a recording sheet, the image forming device including a cam drive device, the can drive device including,
an eccentric cam configured to rotate, the eccentric cam including a first portion and a second portion, the second portion having a different curvature from the first portion;
a displacement body configured to displace in response to a change in a rotation position of the eccentric cam in contact with the displacement body;
a motor configured to rotate the eccentric cam; and
a power source configured to output an electric current to be supplied to the motor, wherein
an electric current configured to cause a stall torque to the motor being a stop state is changed in response to a rotation stop position of the eccentric cam changing between a first rotation stop position associated with the first portion of the eccentric cam and a second rotation stop position associated with the second portion of the eccentric cam such that the electric current at the first rotation stop position is less than the electric current at the second rotation stop position.

7. The image forming apparatus according to claim 6 , further comprising:
an image bearer configured to bear the toner image formed by the image forming device;
a nip forming body configured to contact the image bearer to form a transfer nip; and
a transfer device configured to transfer the toner image from the image bearer onto a recording sheet sandwiched in the transfer nip, wherein:
the first portion is a concentric curved portion in which a curvature centered on an axis of the eccentric cam is constant; and
the second portion is a non-concentric curved portion in which the curvature centered on the axis of the eccentric cam is not constant,

wherein at the first rotation stop position the concentric curved portion is in contact with the displacement body, and at the second rotation stop position the non-concentric curved portion is in contact with the displacement body, and
wherein the cam drive device changes, with driving of the cam, at least one of a nip pressure in the transfer nip and a distance between the image bearer and the nip forming body.

8. The image forming apparatus according to claim 7 , wherein the nip pressure is set smaller at a sheet main portion entry timing at which a main portion of the recording sheet is not in the transfer nip than when the main portion of the recording sheet is in the transfer nip.

9. The image forming apparatus according to claim 8 , further comprising:
a biasing member configured to press the nip forming body toward the image bearer,
wherein, at the sheet main portion entry timing, the cam is set at a position contactless with the displacement body to form the transfer nip.

10. The image forming apparatus according to claim 9 , wherein, at a pre-entry timing immediately before a leading end of the recording sheet enters between the image bearer and the nip forming body, the cam is set at the second rotation stop position to separate the nip forming body from the image bearer, and
wherein the electric current is larger at the pre-entry timing than at the sheet main portion entry timing.

11. The image forming apparatus according to claim 10 , wherein the concentric curved portion of the cam includes:
a first concentric portion; and
a second concentric portion smaller in radius of curvature than the first concentric portion,
wherein, when an image forming action is not performed, the cam is set at a position at which the first concentric portion is in contact with the displacement body to separate the nip forming body from the image bearer, and
wherein the electric current is set smaller when the image forming action is not performed than at the pre-entry timing.

12. The image forming apparatus according to claim 10 , wherein, at a pre-ejection timing immediately before a trailing end of the recording sheet in a direction of conveyance of the recording sheet is ejected from between the image bearer and the nip forming body, the cam is stopped at the second rotation stop position to reduce the nip pressure, and
wherein the electric current is set greater at the pre-ejection timing than at the sheet main portion entry timing.

13. The image forming apparatus according to claim 12 , wherein the concentric curved portion of the cam includes:
a first concentric portion; and
a second concentric portion smaller in radius of curvature than the first concentric portion,
wherein, when an image forming action is not performed, the cam is set at a position at which the first concentric portion is in contact with the displacement body to separate the nip forming body from the image bearer, and
wherein th

Assignees

• Nagata Haruki
• Hasegawa Ryo
• Nagata Atsushi
• Honjoh Kenji
• Ricoh Co Ltd

Inventors

• Nagata Haruki
• Hasegawa Ryo
• Nagata Atsushi
• Honjoh Kenji

Classifications

• F01L13/00

  Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations · CPC title

• G03G2221/1657

  transmitting mechanical drive power · CPC title

• G03G15/5004

  Power supply control, e.g. power-saving mode, automatic power turn-off · CPC title

• G03G15/167

  at least one of the recording member or the transfer member being rotatable during the transfer · CPC title

• G03G15/1615

  relating to the driving mechanism for the intermediate support, e.g. gears, couplings, belt tensioning · CPC title