Title: Automotive electric heater apparatus
Abstract: An electric heater apparatus for automobiles is disclosed. A sheathed heater (14a) constituting a heat generating member of a heater assembly (14) generates heat by power supplied from a main power supply for generating a DC high voltage through an inverter. A thermal fuse (15) has a temperature detecting element (15a) (low-melting alloy) adapted to fuse when a set temperature is reached. The temperature detecting element (15a) is connected to the power circuit of the sheathed heater (14a) through lead wires (15b, 15c). The thermal fuse (15) is arranged in such a position that the longitudinal direction of the temperature detecting element (15a) accommodated in the casing (17) is coincident with the longitudinal direction of the heater assembly 14, and mounted in surface-to-surface contact with the body (aluminum body (14c)) of the heater assembly (14). Also, the interior of the casing (17) is sealed with a material (such as cement or a silicon caulking material) higher in heat conductivity than air.
Patent Number: 7,015,430 Issued on 03/21/2006 to Matsunaga
| Inventors:
|
Matsunaga; Ken (Kariya, JP)
|
| Assignee:
|
Denso Corporation (Kariya, JP)
|
| Appl. No.:
|
798931 |
| Filed:
|
March 11, 2004 |
Foreign Application Priority Data
| Mar 12, 2003[JP] | 2003-066599 |
| Current U.S. Class: |
219/481; 219/505; 219/517 |
| Current Intern'l Class: |
H05B 1/02 (20060101) |
| Field of Search: |
219/481,497,517,519,505,501,494
|
References Cited [Referenced By]
U.S. Patent Documents
| 4394639 | Jul., 1983 | McGalliard.
| |
| 5408579 | Apr., 1995 | Hunt.
| |
| 5928538 | Jul., 1999 | Thivet.
| |
| Foreign Patent Documents |
| 2091980 | Aug., 1982 | GB.
| |
| 2086698 | Dec., 1982 | GB.
| |
| 2002/-324653 | Nov., 2002 | JP.
| |
Primary Examiner: Paschall; Mark
Attorney, Agent or Firm: Harness, Dickey & Pierce, PLC
Claims
The invention claimed is:
1. An automotive electric heater apparatus comprising an electric heater for
generating heat with power supplied from a high voltage power supply, and a thermal
fuse including a temperature detecting element connected in series to the electric
heater through lead wires, the temperature detecting element fusing and turning
off the power circuit of the electric heater when the electric heater is abnormally
overheated, wherein
the thermal fuse includes a casing accommodating the temperature detecting element
and the lead wires therein and mounted on a body surface of the electric heater,
and the interior of the casing is filled up with a material being higher in heat
conductivity than air;
the casing of the thermal fuse is arranged in such a manner that the longitudinal
direction of the temperature detecting element coincides with the longitudinal
direction of the electric heater, and one of the lead wires connected to an end
of the temperature detecting element is bent in the shape of U in the casing on
a plane generally parallel to the body surface of the electric heater and led out
in the same direction as the other lead wire connected to the other end of the
temperature detecting element; and
the casing is mounted in surface-to-surface contact with the body of the electric heater.
2. An automotive electric heater apparatus according to claim 1,
wherein said material having a higher heat conductivity than air contains ceramic
or cement as a main component.
3. An automotive electric heater apparatus according to claim 1,
wherein the casing of the thermal fuse is fixed on the body of the electric heater
through a bracket.
4. An automotive electric heater apparatus according to claim 1, wherein the
temperature detecting element is encased in an insulating container.
5. An automotive electric heater apparatus according to claim 4, wherein the
insulated container and the lead wires are fixed in place by the material being
higher in heat conductivity than the air.
6. An automotive electric heater apparatus according to claim 1, wherein the
lead wires are fixed in place by the material being higher in heat conductivity
than the air.
7. An automotive electric heater apparatus according to claim 1, wherein the
material being higher in heat conductivity is disposed between the temperature
detecting element and the electric heater.
8. An automotive electric heater apparatus according to claim 1, wherein the
electric heater includes a sheathed heater and a hot water pipe, the sheathed heater
being arranged adjacent to one of two straight portions of a U-shaped lead wire
and the hot water pipe being arranged adjacent to the other of the two straight
portions of the U-shaped lead wire, and the temperature detecting element is arranged
at a straight portion of the hot water pipe side.
9. An automotive electric heater apparatus according to claim 1, wherein the
electric heater includes a sheathed heater and a hot water pipe, both of the sheathed
heater and the hot water pipe being embedded in an aluminum body.
10. An automotive electric heater apparatus comprising an electric heater for
generating heat with power supplied from a high voltage power supply, and a thermal
fuse including a temperature detecting element connected in series to the electric
heater through lead wires, the temperature detecting element fusing and turning
off the power circuit of the electric heater when the electric heater is abnormally
overheated, wherein
the thermal fuse includes a casing accommodating the temperature detecting element
and the lead wires therein and mounted on a body surface of the electric heater,
the casing is arranged in such a manner that the longitudinal direction of the
temperature detecting element coincides with the longitudinal direction of the
electric heater, and one of the lead wires connected to an end of the temperature
detecting element is bent in the shape of U in the casing on a plane generally
parallel to the body surface of the electric heater and led out in the same direction
as the other lead wire connected to the other end of the temperature detecting
element; and
the casing is mounted in surface-to-surface contact with the body of the electric heater.
11. An automotive electric heater apparatus according to claim 10,
wherein said material higher in heat conductivity than air contains ceramic or
cement as a main component.
12. An automotive electric heater apparatus according to claim 10,
wherein the casing of the thermal fuse is fixed on the body of the electric heater
through a bracket.
13. An automotive electric heater apparatus according to claim 10, wherein the
electric heater includes a sheathed heater and a hot water pipe, the sheathed heater
being arranged adjacent to one of two straight portions of a U-shaped lead wire
and the hot water pipe being arranged adjacent to the other of the two straight
portions of the U-shaped lead wire, and the temperature detecting element is arranged
at a straight portion of the hot water pipe side.
14. An automotive electric heater apparatus according to claim 10, wherein the
electric heater includes a sheathed heater and a hot water pipe, both of the sheathed
heater and the hot water pipe being embedded in an aluminum body.
15. An automotive electric heater apparatus comprising:
an electric heater;
a thermal fuse including a temperature detecting element and a casing accommodating
the temperature detecting element and lead wires connecting the temperature detecting
element in series with the electric heater; and
a material being higher in heat conductivity than air disposed between the temperature
detecting element and the electric heater; wherein
the material is disposed between the lead wires and the electric heater; and
one of the lead wires is bent in the shape of a U in the casing on a plane generally
parallel to a body surface of the electric heater.
16. An automotive electric heater apparatus according to claim 15, wherein the
electric heater includes a sheathed heater and a hot water pipe, the sheathed heater
being arranged adjacent to one of two straight portions of a U-shaped lead wire
and the hot water pipe being arranged adjacent to the other of the two straight
portions of the U-shaped lead wire, and the temperature detecting element is arranged
at a straight portion of the hot water pipe side.
17. An automotive electric heater apparatus according to claim 15, wherein the
electric heater includes a sheathed heater and a hot water pipe, both of the sheathed
heater and the hot water pipe being embedded in an aluminum body.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an automotive electric heater apparatus utilizing
a high voltage power supply of 200 V to 400 V DC.
2. Description of the Related Art
Automotive vehicles such as a fuel cell-powered vehicle, an electric car
and a hybrid car with little waste heat are designed to employ an electric heater
as a heating system by using a high-voltage power supply together with a thermal
fuse for protecting the electric heater (Japanese Unexamined Patent Publication
No. 2002-324653).
The thermal fuse, as shown in FIGS. 4A,
4B, includes a temperature detecting
element
120 (low-melting alloy) connected to an electric heater
110
through lead wires
100. A ceramic container
130 accommodating the
temperature detecting element
120 is inserted into an insulating tube
140
together with the lead wires
100, and the insulating tube
140 is
mounted in contact with an aluminum body
150 of the electric heater
110.
In the case where the electric heater
110 is abnormally overheated, heat
is transmitted from the aluminum body
150 to the lead wires
100 in
the insulating tube
140, and when the temperature detecting element
120
which has received the heat from the lead wires
100 reaches a set temperature,
the thermal fuse fuses and turns off the power circuit of the electric heater
110.
In the thermal fuse described above, however, only a peripheral part of the insulating
tube
140 is in contact with the surface of the aluminum body
150
of the electric heater
110 as shown in FIG. 4B and, therefore, the contact
area between the insulating tube
140 and the aluminum body
150 is
very small. Also, an air layer (an air layer in the insulating tube
140)
low in heat conductivity in the path of the heat transmitted from the aluminum
body
150 to the lead wires
100 causes a considerable length of time
to be consumed before the temperature detecting element
120 blows (the thermal
fuse has a low temperature sensitivity). As a result, the surface temperature of
the aluminum body
150 increases greatly (to, say, 400° C. or higher)
before the temperature detecting element
120 actually fuses, thereby posing
a safety problem.
Also, in the thermal fuse shown in FIGS. 4A,
4B, the two lead wires
100 connected to the temperature transducer
120 are led out in opposite
directions. Therefore, a harness (not shown) connected to one of the lead wires
100 is required to be laid in U-turn form, and the resulting detour-connection
of harness reduces the working efficiency.
SUMMARY OF THE INVENTION
This invention has been achieved in view of the situation described above, and
the object thereof is to provide an automotive electric heater apparatus in which
the temperature sensitivity of the thermal fuse is improved, for a higher safety,
while, at the same time, improving the connection of the harness to the lead wires
of the thermal fuse.
According to one aspect of the invention, there is provided an automotive
electric heater apparatus comprising an electric heater, for generating heat with
power supplied from a high voltage power supply of 200 V to 400 V DC, and a thermal
fuse including a temperature detecting element connected in series to the electric
heater through lead wires,
- wherein the temperature detecting element is adapted to blow and turn
off the power circuit of the electric heater when the electric heater is abnormally
overheated, and
- wherein the thermal fuse includes a casing accommodating the temperature
detecting element and the lead wires therein and mounted on the body surface of
the electric heater, and the interior of the casing is sealed with a material higher
in heat conductivity than air.
In this configuration, as described above, the interior of the casing accommodating
the temperature detecting element and the lead wires is sealed with a material
higher in heat conductivity than the air. As compared with a case in which the
interior of the casing is filled with air, therefore, the temperature sensitivity
of the thermal fuse is improved and, when the electric heater is abnormally overheated,
therefore, the temperature detecting element fuses within a shorter time. As a
result, in the case where the electric heater is abnormally overheated, the temperature
detecting element fuses and turns off the power circuit of the electric heater
at an early time to assure a higher safety.
Also, the periphery of the temperature detecting element and the lead wires
is fixedly covered with a material high in heat conductivity. Should the casing
be broken, therefore, the lead wires (blown portion) are not exposed and the power
circuit of the electric heater is positively turned off when the temperature detecting
element fuses.
According to another aspect of the invention, there is provided an automotive
electric heater apparatus comprising an electric heater, for generating heat with
power supplied from a high voltage power supply of 200 V to 400 V DC, and a thermal
fuse including a temperature detecting element connected in series to the electric
heater through lead wires,
- wherein the temperature detecting element is adapted to fuse and turn
off the power circuit of the electric heater when the electric heater is abnormally
overheated, and
- wherein the thermal fuse includes a casing accommodating the temperature
detecting element and the lead wires therein and mounted on the body surface of
the electric heater, the casing is arranged in such a manner that the longitudinal
direction of the temperature detecting element coincides with the longitudinal
direction of the electric heater, and one of the lead wires connected to an end
of the temperature detecting element is bent in the shape of U in the casing and
led out in the same direction as the other lead wire connected to the other end
of the temperature detecting element.
In this configuration the two lead wires connected to the temperature detecting
element are led out of the casing in the same direction. Therefore, the harness
connected to the lead wires is not required to be laid in U-turn fashion, thereby
improving the harness connection for an improved working efficiency.
As the thermal fuse is of such a type that the longitudinal direction of the
temperature
detecting element is arranged in the longitudinal direction of the electric heater,
the width of the casing can be reduced as compared with the type in which the lead
wires are led out in the direction at right angles to the temperature detecting
element. Thus, the casing is not exposed outside the body of the electric heater
and can be arranged efficiently.
According to still another aspect of the invention, there is provided an
automotive electric heater apparatus,
- wherein the casing of the thermal fuse is arranged in such a manner
that the longitudinal direction of the temperature detecting element coincides
with the longitudinal direction of the electric heater, and one of the lead wires
connected to an end of the temperature detecting element is bent in the shape of
U in the casing and led out in the same direction as the other lead wire connected
to the other end of the temperature detecting element.
In the automotive electric heater apparatus according to this invention, a material
containing ceramic or cement, as a main component having a higher heat conductivity
than air, can be used.
In the automotive electric heater apparatus according to this invention, the
casing
is mounted in surface-to-surface contact with the body of the electric heater.
With this configuration, as compared with the prior art (Japanese Unexamined
Patent Publication No. 2002-324652) in which an insulating tube is arranged in
contact with the body surface of the electric heater, the contact area between
the casing and the body surface of the electric heater is increased and, therefore,
the temperature sensitivity of the thermal fuse increases. In the case where the
electric heater is abnormally overheated, the temperature detecting element fuses
and turns off the power circuit of the electric heater earlier for a further improved safety.
In the automotive electric heater apparatus according to this invention, the
casing
of the thermal fuse is fixed on the body of the electric heater through a bracket.
The thermal fuse according to the invention is not fixed by solder or the like
on a control board, for example, but on the body of the electric heater through
a bracket which is screwed and securely fixed.
The present invention may be more fully understood from the description of preferred
embodiments of the invention, as set forth below, together with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1A is a perspective view of an electric heater apparatus having a thermal
fuse, and FIG. 1B a sectional view of a heater assembly.
FIG. 2 is a perspective view showing a method of fixing the thermal fuse and
is a sectional view of a casing accommodating a temperature detecting element.
FIG. 3 is a schematic diagram showing a configuration of an air conditioning system.
FIGS. 4A, 4B are a diagram for explaining the prior art.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Next, an embodiment of the invention will be explained with reference to the
accompanying drawings.
This embodiment represents an example of application of the electric heater
apparatus according to the invention to the air conditioning system of a fuel cell-powered
vehicle driven with an electric motor as a power source. FIG. 1A is a perspective
view of the electric heater apparatus, and FIG. 3 a schematic diagram showing a
configuration of the air conditioning system.
The air conditioning system includes a duct
1 for introducing the air
into the passenger compartment, a blower
2 for introducing and supplying
the air from inside or outside the passenger compartment into the duct
1,
an evaporator
3 and a heater core
4 arranged in the duct
1,
and an air mix door
5 for adjusting the temperature of the air blown into
the passenger compartment. The air conditioning system is controlled by an electronic
control unit (ECU)
6.
The evaporator
3 is a well-known heat exchanger used in a refrigeration
cycle and cools the blown air by exchanging heat with a low-temperature refrigerant
supplied by the operation of a compressor
7.
The compressor
7 is driven by an AC motor, and the rotational speed of
the AC motor (i.e. the amount of the refrigerant discharged from the compressor
7) is controlled by the ECU
6 through an inverter
8. The inverter
8 is supplied with DC current from a main power supply
9 (the high
voltage power supply according to the invention) mounted on the vehicle. The main
power supply
9 is charged by a fuel cell not shown and generates a high
voltage of 200 V to 400 V DC.
The heater core
4 is arranged downstream of the evaporator
3 along
the air flow in the duct
1, is connected with a cooling water circuit
10,
and heats the blown air by exchanging heat with the hot water flowing in the heater
core
4.
The cooling water circuit
10 includes a pump
11 for circulating
the cooling water, an electric heater apparatus
12 according to the invention
for heating the cooling water, and a water temperature sensor
13 for detecting
the temperature of the cooling water supplied to the heater core
4.
The air mix door
5 is arranged rotatably between a position of the lowest
temperature (position indicated by dashed line in FIG. 3) where the air inlet side
of the heater core
4 is closed up and a position of the highest temperature
(position indicated by solid line in FIG. 3) where the detour circuit of the heater
core
4 is closed up. The air mix door
5 thus adjusts the ratio between
the air passing through the heater core
4 and the air detouring the heater
core
4 (the air flowing in the detour circuit) thereby to change the blown
air temperature.
The air adjusted in temperature by the air mix door
5 is blown into the
passenger compartment by way of an air outlet (not shown) selected in accordance
with the air outlet mode.
Next, the electric heater apparatus
12 is explained.
The electric heater apparatus
12 comprises, as shown in FIGS. 1A,
1B,
a heater assembly
14 for heating the cooling water, and a thermal fuse
15
constituting a protection device of the heater assembly
14.
The heater assembly
14, as shown in FIG. 1B, is configured of a sheathed
heater
14a making up a heat generating member embedded in an aluminum
body
14c together with a hot water pipe
14b.
The sheathed heater
14a is connected to the inverter
8 and
heated by the power supplied from the main power supply
9 through the inverter
8.
The duty cycle of the power supplied to the sheathed heater
14a is
controlled by the ECU
6 through the inverter
8 in such a manner that
the cooling water temperature detected by the water temperature sensor
13
is held at a predetermined level (say, 80° C. at maximum).
The hot water pipe
14b has an end thereof connected to the outlet
of the pump
11, and the other end thereof connected to the hot water inlet
of the heater core
4, thus constituting a part of the cooling water path.
The thermal fuse
15 includes a temperature detecting element
15a
(low-melting alloy) adapted to fuse when a set temperature (say, 180°
C.) is reached. The temperature detecting element
15a is connected
to the power circuit of the sheathed heater
14a through two lead
wires
15b15c. (Specifically, the lead wire
15b
is connected to the inverter
8, and the other lead wire
15c
is connected in series with the sheathed heater
14a.)
The thermal fuse
15 has a casing
17 for accommodating the temperature
detecting element
15a encased in the insulating container
16
and the two lead wires
15b,
15c.
The lead wire
15b connected to an end of the temperature detecting
element
15a is bent in the shape of U in the casing
17 and,
together with the other lead wire
15c connected to the other end
of the temperature detecting element
15a, is led out in the same
direction from one side of the casing
17.
The casing
17 is formed of an insulating material, such as a ceramic,
high in heat conductivity and is screwed, through a bracket
18 (FIG. 2),
to an aluminum body
14c of the heater assembly
14. The casing
17, as shown in FIG. 1A, is arranged so that the longitudinal direction
of the temperature detecting element
15a is coincident with the longitudinal
direction of the heater assembly
14 and is mounted in surface contact with
the body of the heater assembly
14.
Also, the interior of the casing
17 is sealed (filled up) with a material
being higher in heat conductivity than air and having stiffness capable of enduring
breaking energy when the thermal fuse
15 is fused (such as cement or a silicon
caulking agent).
As described above, the electric heater apparatus
12 has the interior
thereof
sealed with a material having a higher heat conductivity than air. Therefore, heat
is transmitted more quickly from the body surface of the heater assembly
14
through the lead wires
15b,
15c to the temperature
detecting element
15a. The casing
17, which is formed of a
ceramic high in heat conductivity, is mounted in surface contact on the body of
the heater assembly
14, and, therefore, the thermal resistance thereof is
reduced. As a result, the temperature sensitivity of the thermal fuse
15
is improved. As compared with the prior art (Japanese Unexamined Patent Publication
No. 2002-324653), therefore, the temperature detecting element
15a fuses
within a shorter time when the sheathed heater
14a is abnormally
overheated. The earlier fusing of the temperature detecting element
15a
turns off the power circuit of the sheathed heater circuit
14a earlier.
Thus, the surface temperature of the heater assembly
14 (the surface temperature
of the aluminum body
14c) is prevented from increasing excessively
(say, 400° C. or higher) thereby to assure an improved safety.
The interior of the casing
17 is sealed with a material high in heat conductivity
(i.e. the surroundings of the insulating container
16 and the lead wire
15b are fixed by a material high in heat conductivity), as described
above. Should the casing
17 be broken, therefore, the temperature detecting
element
15a which may fuse is not exposed to the exterior. Thus,
the fused part of the temperature detecting element
15a is kept out
of contact with the body surface of the heater assembly
14 and prevented
from being grounded. In this way, the power circuit of the sheathed heater
14a
can be turned off safely and positively.
Further, the lead wire
15b of the thermal fuse
15 connected
to an end of the temperature detecting element
15a is bent in the
shape of U in the casing
17, and together with the other lead wire
15c
connected to the other end of the temperature detecting element
15a,
is led out in the same direction from one side of the casing
17. As shown
in FIG. 1A, therefore, the harness
19 connected to the lead wires
15b,
15c is not required to be laid in U-turn fashion. Thus, the connection
of the harness
19 is improved for an improved working efficiency.
Also, in view of the fact that the length of the temperature detecting element
15a is arranged along the length of the heater assembly
14,
the width of the casing
17 (horizontal width in FIG. 2) can be reduced as
compared with the thermal fuse of the type in which the lead wires are led in the
direction at right angles to the temperature detecting element. As a result, the
casing
17 can be arranged in an efficient way without being exposed from
the heater assembly
14.
The bracket
18 for fixing the casing
17 of the thermal fuse
15
to the heater assembly
14 may be fixed by other than the screw (by a clamp,
for example).
According to this embodiment, the electric heater apparatus
12 according
to the invention is applied to the air conditioning system of the fuel cell-powered
vehicle. Nevertheless, the electric heater apparatus
12 according to the
invention may be used for the heating system of other vehicles (such as an electric
car and a hybrid car), with little waste heat, with equal effect.
While the invention has been described by reference to specific embodiments
chosen for purposes of illustration, it should be apparent that numerous modifications
could be made thereto by those skilled in the art without departing from the basic
concept and scope of the invention.
*
