Heating device with asymmetrically configured thermal conductor, fixing device, and image forming apparatus
A heating device includes a rotator, a heater including a base and a heat generator that forms a heat generation region, and a thermal conductor. The base, the heat generation region, the thermal conductor, and a maximum sheet passing region shorter than the heat generation region each extend from one end to another end in the longitudinal direction. A protrusion amount between the heat generation region and the base regarding the one end is shorter than that between them regarding another end. The following expressions are satisfied. L 1 R ≤ L 2 R ≤ L 1 R + 1 ( mm ) ( 1 ) 0 ≤ ( L 2 R - L 1 R ) ≤ ( L 2 L - L 1 L ) ( mm ) ( 2 ) where L1 means the protrusion amount between the maximum sheet passing region and the heat generation region, L2 means the protrusion amount between the maximum passing region and the thermal conductor, and R means the amount regarding another end.
1 . A heating device comprising:
a rotator;
a heater extending in a longitudinal direction to heat the rotator, the heater including:
a base extending from one end to another end in the longitudinal direction; and
a resistive heat generator on the base, the resistive heat generator forming a main heat generation region extending from one end to another end in the longitudinal direction; and
a thermal conductor having a higher thermal conductivity than the base, the thermal conductor extending from one end to another end in the longitudinal direction,
wherein the heating device has a maximum passing region through which a maximum recording medium having the largest width of recording media used in the heating device passes, the maximum passing region has one end and another end in the longitudinal direction,
the base has:
a first base portion protruding from the one end of the main heat generation region to the one end of the base by a first protrusion amount (L5L); and
a second base portion protruding from said another end of the main heat generation region to said another end of the base by a second protrusion amount larger than the first protrusion amount of the first base portion,
the main heat generation region has:
a first heater portion protruding from the one end of the maximum passing region to the one end of the main heat generation region by a third protrusion amount; and
a second heater portion protruding from said another end of the maximum passing region to said another end of the main heat generation region by a fourth protrusion amount,
the thermal conductor has:
a first conductor portion protruding from the one end of the maximum passing region to the one end of the thermal conductor by a fifth protrusion amount; and
a second conductor portion protruding from said another end of the maximum passing region to said another end of the thermal conductor by a sixth protrusion amount, and
the base, the main heat generation region, and the maximum passing region satisfy the following expressions,
L
1
R
≦
L
2
R
≦
L
1
R
+
1
mm
(
1
)
0
≦
L
3
R
<
L
3
L
(
2
)
where
L1R (mm) is the fourth protrusion amount,
L2R (mm) is the sixth protrusion amount,
L
3
R
=
L
2
R
-
L
1
R
,
L
3
L
=
L
2
L
-
L
1
L
,
L1L is the third protrusion amount, and
L2L is the fifth protrusion amount.
2 . The heating device according to claim 1 ,
wherein the base and the maximum passing region satisfy the following expressions,
L
2
L
≤
L
4
L
(
3
)
L
2
R
≤
L
4
R
(
4
)
where
L4L is a protrusion amount (mm) from the one end of the maximum passing region to the one end of the base in the longitudinal direction, and
L4R is a protrusion amount (mm) from said another end of the maximum passing region to said another end of the base in the longitudinal direction.
3 . The heating device according to claim 1 ,
wherein the base, the main heat generation region, and the maximum passing region satisfy the following expressions,
0.6
≤
AL
/
AR
≤
1.4
(
5
)
AL
=
λ
1
×
V
1
L
+
λ
2
×
V
2
L
AR
=
λ
1
×
V
1
R
+
λ
2
×
V
2
R
where
λ1 is a thermal conductivity [W/m·K] of the base,
λ2 is a thermal conductivity [W/m·K] of the thermal conductor,
V1L is a volume (mm 3 ) of the first base portion,
V2L is a volume (mm 3 ) of the thermal conductor from the one end of the main heat generation region to the one end of the thermal conductor in the longitudinal direction,
V1R is a volume (mm 3 ) of the second base portion, and
V2R is a volume (mm 3 ) of the thermal conductor from said another end of the main heat generation region to said another end of the high thermal conductor in the longitudinal direction.
4 . The heating device according to claim 3 ,
wherein the base, the main heat generation region, and the maximum passing region satisfy the following expressions.
0.8
≤
AL
/
AR
≤
1.2
.
(
6
)
5 . The heating device according to claim 1 ,
wherein the thermal conductor is made of aluminum.
6 . The heating device according to claim 1 , further comprising
grease interposed between the heater and the rotator.
7 . A fixing device comprising
the heating device according to claim 1 .
8 . An image forming apparatus comprising
the fixing device according to claim 7 .
9 . A heating device comprising:
a rotator;
a heater extending in a longitudinal direction to heat the rotator, the heater including:
a base extending from one end to another end in the longitudinal direction;
a resistive heat generator on the base, the resistive heat generator forming a main heat generation region extending from one end to another end in the longitudinal direction;
a first conductor adjacent to the one end of the main heat generation region; and
a second conductor adjacent to said another end of the main heat generation region, the second conductor longer than the first conductor in the longitudinal direction; and
a thermal conductor having a higher thermal conductivity than the base, the thermal conductor extending from one end to another end of the thermal conductor in the longitudinal direction,
wherein the heating device has a maximum passing region through which a maximum recording medium having the largest width of recording media used in the heating device passes, the maximum passing region has one end and another end in the longitudinal direction,
the main heat generation region has:
a first heater portion protruding from the one end of the maximum passing region to the one end of the main heat generation region by a third protrusion amount; and
a second heater portion protruding from said another end of the maximum passing region to said another end of the main heat generation region by a fourth protrusion amount,
the thermal conductor has:
a first conductor portion protruding from the one end of the maximum passing region to the one end of the thermal conductor by a fifth protrusion amount; and
a second conductor portion protruding from said another end of the maximum passing region to said another end of the thermal conductor by a sixth protrusion amount, and
the base, the main heat generation region, and the maximum passing region satisfy the following expressions,
L
1
R
≦
L
2
R
≦
L
1
R
+
1
mm
(
1
)
0
≦
L
3
R
<
L
3
L
(
2
)
where
L1R (mm) is the fourth protrusion amount,
L2R (mm) is the sixth protrusion amount,
L
3
R
=
L
2
R
-
L
1
R
,
L
3
L
=
L
2
L
-
L
1
L
,
L1L is the third protrusion amount, and
L2L is the fifth protrusion amount.
10 . A fixing device comprising
the heating device according to claim 9 .
11 . An image forming apparatus comprising
the fixing device according to claim 10 .
12 . A heating device comprising:
a rotator;
a heater extending in a longitudinal direction to heat the rotator, the heater including:
a base extending from one end to another end in the longitudinal direction; and
a resistive heat generator on the base, the resistive heat generator forming a main heat generation region extending from one end to another end in the longitudinal direction; and
a thermal conductor having a higher thermal conductivity than the base, the thermal conductor extending from one end to another end in the longitudinal direction,
wherein the heating device has a maximum passing region through which a maximum recording medium having the largest width of recording media used in the heating device passes, the maximum passing region has one end and another end in the longitudinal direction,
the base has:
a first portion from a center of the main heat generation region to the one end of the base in the longitudinal direction; and
a second portion from the center of the main heat generation region to said another end of the base in the longitudinal direction,
a saturation temperature of the first portion is higher than a saturation temperature of the second portion when the heater itself generates heat,
the main heat generation region has:
a first heater portion protruding from the one end of the maximum passing region to the one end of the main heat generation region by a third protrusion amount; and
a second heater portion protruding from said another end of the maximum passing region to said another end of the main heat generation region by a fourth protrusion amount,
the thermal conductor has:
a first conductor portion protruding from the one end of the maximum passing region to the one end of the thermal conductor by a fifth protrusion amount; and
a second conductor portion protruding from said another end of the maximum passing region to said another end of the thermal conductor by a sixth protrusion amount, and
the base, the main heat generation region, and the maximum passing region satisfy the following expressions,
L
1
R
≦
L
2
R
≦
L
1
R
+
1
mm
(
1
)
0
≦
L
3
R
<
L
3
L
(
2
)
where
L1R (mm) is the fourth protrusion amount,
L2R (mm) is the sixth protrusion amount,
L
3
R
=
L
2
R
-
L
1
R
,
L
3
L
=
L
2
L
-
L
1
L
,
L1L is the third protrusion amount, and
L2L is the fifth protrusion amount.
13 . A fixing device comprising
the heating device according to claim 12 .
14 . An image forming apparatus comprising
the fixing device according to claim 13 .