Image forming apparatus capable of detecting sheet

Patent metadata

Field	Value
Publication number	US-2018203402-A1
Application number	US-201715855384-A
Country	US
Kind code	A1
Filing date	Dec 27, 2017
Priority date	Jan 19, 2017
Publication date	Jul 19, 2018
Grant date	—

Abstract

An emitter emits light such that the light crosses a conveyance path. A reflector reflects the light. A receiver receives reflected light. A determiner determines that a sheet is present on the basis of an amount of reflected light. A controller may increase a light amount of the light-emitting unit from a first light amount to a second light amount on the basis of a temperature of the light-emitting unit and a reflectance of the reflecting member. The controller may increase a receiving gain of the receiver from a first gain to a second gain on the basis of a reflectance of the reflecting member.

First claim

What is claimed is:

1 . An image forming apparatus comprising:
a light-emitting unit that emits light such that the light crosses a conveyance path along which a sheet is conveyed; a reflecting member, provided opposite the light-emitting unit, that reflects the light; a light-receiving unit that receives reflected light from the reflecting member; a cooling unit that cools the light-emitting unit by supplying air to the light-emitting unit; a determination unit that determines whether or not the sheet is present on the basis of an amount of reflected light received by the light-receiving unit; and a light amount control unit that increases a light amount of the light-emitting unit from a first light amount to a second light amount on the basis of a temperature of the light-emitting unit cooled by the cooling unit and a reflectance of the reflecting member.

2 . The image forming apparatus according to claim 1 ,
wherein the light amount control unit increases the light amount of the light-emitting unit from the first light amount to the second light amount in a period from when condensation has formed on the reflecting member to when the amount of reflected light drops below a permissible limit.

3 . The image forming apparatus according to claim 2 , further comprising:
a counting unit that counts an amount of time that has passed from when the cooling unit starts cooling operations, wherein the light amount control unit increases the light amount of the light-emitting unit from the first light amount to the second light amount when the amount of time that has passed reaches a predetermined amount of time.

4 . The image forming apparatus according to claim 2 , further comprising:
a counting unit that counts an amount of time that has passed from when the cooling unit has increased an airflow rate from a first airflow rate to a second airflow rate, wherein the light amount control unit increases the light amount of the light-emitting unit from the first light amount to the second light amount when the amount of time that has passed reaches a predetermined amount of time.

5 . The image forming apparatus according to claim 4 ,
wherein the first airflow rate is zero.

6 . The image forming apparatus according to claim 1 , further comprising:
a fixing unit that applies heat to a toner image transferred onto a sheet to fix the toner image onto the sheet; a temperature measurement unit that measures a temperature of the fixing unit; and a deciding unit that decides the second light amount in accordance with the temperature.

7 . The image forming apparatus according to claim 6 ,
wherein the temperature measurement unit measures the temperature when the image forming apparatus starts forming an image.

8 . The image forming apparatus according to claim 6 ,
wherein the light-emitting unit, the light-receiving unit, and the reflecting member are disposed within or near the fixing unit.

9 . The image forming apparatus according to claim 1 , further comprising:
a temperature measurement unit that measures an ambient temperature of the reflecting member; and a deciding unit that decides the second light amount in accordance with the ambient temperature.

10 . The image forming apparatus according to claim 9 ,
wherein the temperature measurement unit measures the ambient temperature when the image forming apparatus starts forming an image.

11 . The image forming apparatus according to claim 1 , further comprising:
a ventilation duct that leads air blown from the cooling unit or sucked by the cooling unit to the light-emitting unit so as to cool the light-emitting unit.

12 . The image forming apparatus according to claim 1 , further comprising:
a first guide member and a second guide member, provided opposite each other in the conveyance path, that guide the sheet, wherein the light-emitting unit and the light-receiving unit are fixed to the first guide member; and the reflecting member is fixed to the second guide member.

13 . The image forming apparatus according to claim 1 , further comprising:
a light shielding member provided between the light-emitting unit and the light-receiving unit.

14 . The image forming apparatus according to claim 13 ,
wherein the light shielding member shields direct light directed from the light-emitting unit toward the light-receiving unit, and guides air from the cooling unit or air traveling toward the cooling unit to the reflecting member.

15 . The image forming apparatus according to claim 1 ,
wherein the light amount control unit furthermore increases the light amount of the light-emitting unit on the basis of an amount of light received by the light-receiving unit.

16 . An image forming apparatus comprising:
a light-emitting unit that emits light such that the light crosses a conveyance path along which a sheet is conveyed; a reflecting member, provided opposite the light-emitting unit, that reflects the light; a light-receiving unit that receives reflected light from the reflecting member; a determination unit that determines whether or not the sheet is present on the basis of an amount of reflected light received by the light-receiving unit; and a gain control unit that increases a receiving gain of the light-receiving unit from a first gain to a second gain on the basis of a reflectance of the reflecting member.

17 . The image forming apparatus according to claim 16 ,
wherein the gain control unit increases the receiving gain of the light-receiving unit from the first gain to the second gain in a period from when condensation has formed on the reflecting member to when the amount of reflected light drops below a permissible limit.

18 . The image forming apparatus according to claim 17 , further comprising:
a blower unit that supplies air to the reflecting member; and a counting unit that counts an amount of time that has passed from when the blower unit starts blowing air, wherein the gain control unit reduces the receiving gain of the light-receiving unit from the second gain to the first gain upon the amount of time that has passed reaching a predetermined amount of time.

19 . The image forming apparatus according to claim 18 , further comprising:
a ventilation duct that leads air blown from the blower unit or sucked by the blower unit to the reflecting member so as to blow on the reflecting member.

20 . The image forming apparatus according to claim 16 , further comprising:
a fixing unit that applies heat to a toner image transferred onto a sheet to fix the toner image onto the sheet; a temperature measurement unit that measures a temperature of the fixing unit; and a deciding unit that decides a value of the second gain in accordance with the temperature.

21 . The image forming apparatus according to claim 20 ,
wherein the temperature measurement unit measures the temperature when the image forming apparatus starts forming an image.

22 . The image forming apparatus according to claim 20 ,
wherein the light-emitting unit, the light-receiving unit, and the reflecting member are disposed within or near the fixing unit.

23 . The image forming apparatus according to claim 16 , further comprising:
a temperature measurement unit that measures an ambient temperature of the reflecting member; and a deciding unit that decides the value of the second gain in accordance with the ambient temperature.

Assignees

• Canon Kk

Inventors

• Okuma Yasuhiko
• Nakano Keisuke

Classifications

• G03G15/70 Primary

  Detecting malfunctions relating to paper handling, e.g. jams · CPC title

• G03G15/2039

  with means for controlling the fixing temperature · CPC title

• G03G15/5029

  by measuring the copy material characteristics, e.g. weight, thickness · CPC title

• G03G21/206

  Conducting air through the machine, e.g. for cooling, filtering, removing gases like ozone · CPC title

• G03G2215/00721

  of sheet position · CPC title