Abstrict
A core unit of a heat exchanger is composed of a plurality of parallel
flat tubes, a plurality of corrugated fins, a support member disposed
between two of the corrugated fins and an electric heater disposed
inside the support member. The support member has a pair of parallel
plates bonded to the corrugated fins at the summits of corrugation
of the corrugated fins. The electric heater is composed of a heating
element and an insulation member inserted between the heating element
and the parallel plates.
Claims
What is claimed is:
1. A core unit of a heat exchanger including an inlet tank and
an outlet tank for a heat carrier, said core comprising:
a plurality of corrugated fins disposed in parallel with each other;
a plurality of parallel flat tubes each of which is disposed in
contact with first adjacent corrugated fins and connected to said
inlet and outlet tanks to conduct said heat carrier; and
a heater support member in contact with second adjacent corrugated
fins in parallel with said plurality of flat tubes, said heater
support member including a pair of plates parallelly extending along
said flat tubes and an electric heater held between said pair of
plates to generate heat when said heater is energized, thereby heating
air flowing through said second adjacent corrugated fins, said electric
heater being electrically insulated from said plurality of fins.
2. A core unit as claimed in claim 1, wherein
said flat tubes, said corrugated fins and said support plates are
made of aluminum and soldered with each other.
3. A core unit as claimed in claim 1, wherein
said electric heater further comprises a plus electrode, a minus
electrode and an insulating cover surrounding said two electrodes,
and
said electric heater is inserted between said pair of plates.
4. A core unit as claimed in claim 3, wherein
each of said plus electrode and said minus electrode has a connecting
terminal integrally formed thereon.
5. A core unit as claimed in claim 4, wherein
each of said connecting terminals projects from corresponding one
of said plus electrode and said minus electrode in a direction of
thickness of said core unit.
6. A core unit as claimed in claim 4 further comprising means for
holding said electric heater under pressure between said pair of
plates.
7. A core unit as claimed in claim 1, wherein
said electric heater has a positive temperature characteristic
sharply changing resistance thereof at a set temperature,
said electric heater is electrically insulated from said plurality
of fins, and
said electric heater heats portions of said fins adjacent to said
flat tubes at a temperature equal to temperature of said heat carrier
in said flat tubes if a temperature of said heat carrier is equal
to or higher than 60.degree. C. and temperature of air to be heated
is equal to or lower than 0.degree. C.
8. A core unit as claimed in claim 1, wherein
said electric heater has a positive temperature characteristic
sharply changing resistance thereof at a set temperature,
said electric heater is electrically insulated from said plurality
of fins,
said fins have summits disposed between two of said flat tubes,
said fins have a height between 3.9 mm and 5 mm, and
said set temperature of said electric heater is between 85.degree.
C. and 120.degree. C.
9. A core unit of a heat exchanger core having an air inlet side
and an air outlet side, said core comprising:
a plurality of parallelly disposed flat tubes which conduct heat
carrier;
a plurality of corrugated fins disposed in contact with said flat
tubes;
a support member having a pair of plates parallelly extending along
said flat tubes, an opening end portion and a U-shaped closing end
portion, said support member disposed between summits of corrugation
of adjacent two of said corrugated fins, said U-shaped closing end
portion is disposed at said air inlet side, each of said plates
being bonded to one of said corrugated fins at summits of corrugation;
and
an electric heater disposed between said support plates and insulated
from said support member.
10. A core unit as claimed in claim 9, wherein
said opening end portion projects from an end of said electric
heater.
11. A core unit as claimed in claim 9, wherein
said opening end portion spreads in a skirt-shape.
12. A core unit as claimed in claim 9, wherein
said support member has the same thickness as said core unit in
the air flow direction, and
said electric heater has smaller thickness in the direction of
core thickness than said support member, and
said support member comprises means for positioning said electric
heater therein.
13. A core unit as claimed in claim 12, wherein
said means for positioning comprises a stopper projecting inside
from at least one of said two plates.
14. A core unit for a heater as claimed in claim 13, wherein one
of said plates has a reinforcement rib disposed between said stopper
and said closing end portion.
15. A core unit as claimed in claim 13, wherein
said means for positioning comprises a stopper member disposed
between said electric heater and said closing end portion.
16. A core unit as claimed in any one of claim 9, wherein
each of said flat tubes, corrugated fins and support member is
made of aluminum and soldered to each other.
17. A core unit as claimed in claim 9, wherein
said electric heater comprises a plus electrode, a minus electrode,
a heating element disposed between said two electrodes, and an insulating
cover member covering said two electrodes, and
said cover member is pressed fitted between said plates to hold
said electric heater therein.
18. A core unit as claimed in claim 17, wherein
each of said plus electrode and said minus electrode has a connecting
terminals projecting therefrom.
19. A core unit as claimed in claim 9 further comprising
a fastening member, disposed on said air outlet side of said core
unit, said for holding said electric heater in said support member.
20. A core unit of a heat exchanger including an inlet tank and
an outlet tank for a heat carrier, said core unit comprising:
a plurality of parallelly disposed flat tubes which conduct said
heat carrier;
a plurality of corrugated fins having summits disposed in contact
with said plurality of flat tubes; and
an electric heater disposed between two of said plurality of corrugations
in parallel with said plurality of flat tubes, said electric heater
having a positive temperature characteristic sharply changing resistance
thereof at a set temperature, said electric heater being electrically
insulated from said plurality of fins, wherein
said electric heater with said set temperature heats portions of
said fins adjacent to said flat tubes at a temperature equal to
temperature of said heat carrier in said flat tubes if a temperature
of said heat carrier is equal to or higher than 60.degree. C. and
temperature of air to be heated is equal to or lower than 0.degree.
C.
21. A core unit of a heat exchanger including an inlet tank and
an outlet tank for a heat carrier, said core unit comprising:
a plurality of parallelly disposed flat tubes which connect said
inlet and outlet tanks to said heat carrier;
a plurality of corrugated fins each of which is disposed between
two of said flat tubes;
an electric heater disposed at a portion of said heat exchanger
core in parallel with said flat tubes, said electric heater having
a positive temperature characteristic sharply changing resistance
thereof at a set temperature, said electric heater being electrically
insulated from said plurality of fins, wherein
said fins have summits disposed between two of said flat tubes,
said fins have a height between 3.9 mm and 5 mm, and
said set temperature of said electric heater is between 85.degree.
C. and 120.degree. C.
22. A core unit as claimed in claim 20, wherein
said core unit is made of aluminum alloy,
said electric heater is a three-layered sandwich structure composed
of an electric heater element and two flat electrodes on opposite
sides of said electric heater element and is inserted between said
corrugated fins and said two electrodes, and
said two electrodes are pressed fitted to said summits of the corrugation.
23. A core unit as claimed in claim 22, wherein
said heater element has a positive temperature characteristic sharply
changing resistance thereof at a set temperature which is between
120.degree. C. and 170.degree. C.
24. A method of manufacturing a core unit of a heat exchanger to
be assembled with an inlet tank and an outlet tank, said core unit
being composed of a plurality of parallelly disposed flat tubes,
corrugated fins having summits, a pair of support plates and an
electric heater, said method comprising steps of:
stacking a portion of said flat tubes of said heat exchanger core
and said corrugated fins alternately;
stacking said pair of support plates in the same manner as said
flat tubes between said summits of corrugation at a portion where
said electric heater is to be disposed;
soldering said flat tubes, said corrugated fins and said support
plates into a unit; and
inserting said electric heater between said two plates such that
said electric heater is electrically insulated from said plurality
of fins.
25. The core unit as claimed in claim 1, wherein said heater support
member comprises a U-shaped support plate having a U-shaped closing
portion located at the air inlet side of said core unit.
26. The core unit as claimed in claim 1, further comprising a fastening
member for applying fastening force to said core unit so that said
electric heater can be tightly held in said support member.
27. The core unit as claimed in claim 26, wherein
said fastening member has a pair of hook portions at opposite ends
thereof and a band portion between said hook portions, and
said band portion is narrower than said hook portions to reduce
draft resistance of air passing through said core unit.
28. The core unit as claimed in claim 27, wherein said band portion
has a bend projecting forward from said core unit.
29. The core unit as claimed in claim 26, further comprising an
upper side plate disposed on upper side of said core unit and a
lower side plate disposed under a lower side of said core unit,
wherein
each of said upper and lower side plates has a plurality of reinforcement
ribs and at least one groove between said ribs, and
said hook portions are engaged with said groove of said upper and
lower side plates.
30. The core unit as claimed in claim 29, wherein said hook portions
respectively have members for applying fastening force to one of
said ribs.
31. A core unit of a heat exchanger comprising:
a plurality of cooling fins disposed in parallel with each other;
a plurality of parallel tubes each of which is disposed in contact
with first adjacent one of said cooling fins;
a heater support member in contact with second adjacent one of
said cooling fins in parallel with said plurality of tubes, said
heater support member extending along said tubes;
an electric heater held by said heater support member, said electric
heater being electrically insulated from said plurality of fins;
and
a fastening member for applying fastening force to said core unit
so that said electric heater can be tightly held in said support
member, said fastening member having a pair of hook portions at
opposite ends thereof and a band portion between said hook portions,
said band portion having longitudinal draft opening to reduce draft
resistance of air passing through said core unit.
32. The core unit as claimed in claim 31, wherein said band portion
has a bend projecting forward from said core unit.
33. The core unit as claimed in claim 31, further comprising an
upper side plate disposed on upper side of said core unit and a
lower side plate disposed under a lower side of said core unit,
wherein
each of said upper and lower side plates has a plurality of reinforcement
ribs and at least one groove between said ribs, and
said hook portions are engaged with said groove of said upper and
lower side plates.
34. The core unit as claimed in claim 33, wherein said hook portions
respectively have members for applying fastening force to one of
said ribs.
35. The core unit as claimed in claim 33, wherein
each of said hook portions has an arc-shaped portion.
36. The core unit as claimed in claim 31, wherein one of said pair
of hook portions has an inwardly extending nail portion, and
the other of said pair of hook portions has an inward projection
and a guide portion.
37. The core unit as claimed in claim 31, wherein
each of said plurality of tubes is a flat tube,
each of said plurality of cooling fins is a corrugated fin having
a plurality of summits,
said heater support member comprise a U-shaped member disposed
between said summits.
Electric heater descriptionBACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is related to a heat exchanger of a heater
in which an electric heater is disposed integrally therewith to
heat air in addition to hot water heated by a vehicle engine.
2. Description of the Related Art
Conventional heat exchangers having an integrated electric heater
therein are disclosed in JP-A-5-69732 and JP-A-63-203411. A heat
exchanger of a heater in which hot water or engine coolant is used
to heat air is provided with an integrated electric heater. When
the coolant temperature is low, for example when the engine is just
started, the electric heater is turned on to generate heat, thereby
heating air. This structure reduces pressure loss in the heating
air blow system of the heater as compared with a structure having
a separate PTC heater. Because the PTC heater has a positive temperature
characteristic sharply changing the resistance thereof at a set
temperature, it is not necessary to provide a temperature control
circuit so that the driving circuit thereof can be made simple.
The electric heater is composed of a PTC element and electrodes
and is soldered to a heat exchanger core. Therefore, the PTC element
is exposed to high-temperature air for soldering (e.g. 600.degree.
C. for soldering aluminum members) and, accordingly, the electric
characteristic of the heater element may be damaged substantially.
In a common air conditioning system for a vehicle, a heat exchanger
of a heater is disposed at a downstream side of a heat exchanger
for cooling air to control reheating by the heat exchanger of the
heater, thereby controlling temperature of the air blown into the
passenger compartment of the vehicle. Therefore, condensed water
formed on the heat exchanger for cooling air or snow coming from
the air inlet may adhere the front surface of the heat exchanger
of the heater. Because the electric heater is exposed to the outside
from the heat exchanger core, the water or snow may cause short
circuiting or electric leakage.
In the above conventional device disclosed in the publication,
it is only disclosed that the set temperature of the PTC heater
is 80.degree. C. There is no explanation about how to decide the
set temperature. Our experiments have revealed that the heat generated
by the PTC heater may not be utilized for the heating air to be
heated if the set temperature of the PTC heater is not suitable.
In a core unit of a heat exchanger, a plurality of flat tubes for
conducting water or engine coolant are parallelly disposed, and
each of a plurality of corrugated fins is disposed between two of
the flat tubes. If a PTC heater is installed in place of one of
the flat tubes, the heat of the PTC heater is conducted via the
corrugated fins and the adjacent flat tubes to the water. If the
PTC heater is powered when the water temperature is low, temperature
of portions of the corrugated fins adjacent to the PTC heater becomes
higher than the temperature of portions of the corrugated fins adjacent
to the flat tubes. If the set temperature of the PTC is too high,
the heat generated by the PTC heater is transmitted to the water.
That is, the PTC heater can not heat the heating air to be used
for the heater effectively. On the other hand, if the set temperature
is too low, the PTC heater can not generate power sufficient to
heat the heating air.
SUMMARY OF THE INVENTION
The present invention has been made, in view of the above problems,
to provide a core unit of a heat exchanger in which an electric
heater can be installed without damage.
According to a feature of the present invention, a core unit of
a heat exchanger is composed of a plurality of parallel flat tubes,
a plurality of corrugated fins, a support member disposed between
two of the corrugated fins, and an electric heater disposed inside
the support member. The support member has a pair of parallel plates
bonded to the corrugated fins at the summit of corrugation, and
the electric heater comprises a heating element and an insulation
member inserted between the heating element and the parallel plates.
Accordingly, the support plates can be soldered to the corrugated
fins before the electric heater is inserted between the two support
plates. Therefore, the electric characteristic of the electric heater
is not damaged during the soldering step of the core unit. Although
the corrugated fins have complicated shape, the electric heater
can be inserted easily without damage to the corrugated fins. Further,
because the electric heater is inserted between and insulated from
the two support plates, electric current can be supplied to the
electric heater without passing metal portions (tubes, etc.) of
the core unit, so that electric corrosion of the metal portions
of the core unit can be prevented. Moreover, even if the height
of the corrugations of the corrugated fins are formed uneven, solder
melts and moves due to capillarity and fills gaps between the summits
of the corrugation of the corrugated fins and the support plates.
Thus, the summits of corrugation of the corrugated fins can be soldered
to the support plates with confidence, and heat generated by the
electric heater can be conducted from the support plates to the
corrugated fins effectively.
It is another object of the present invention to prevent short
circuiting and electric leakage caused by condensed water or the
like.
According to another feature of the present invention, a core unit
of a heat exchanger core having an air inlet side and an air outlet
side includes a plurality of parallelly disposed flat tubes which
conduct the heat carrier, a plurality of corrugated fins, a U-shaped
support member having a pair of plates parallelly extending along
the flat tubes, an opening end portion and a U-shaped closing end
portion, and an electric heater disposed between the support plates
and insulated from the support member. The support member is disposed
between the summits of corrugation of adjacent two of the corrugated
fins, the U-shaped closing end portion is disposed at the air inlet
side, and each of the plates is bonded to one of the corrugated
fins at the summits of corrugation. The opening end portion preferably
projects from an end of the electric heater. The opening end portion
may spread in a skirt-shape. The support member may have the same
thickness as the core unit in the air flow direction, and the electric
heater may have smaller thickness in the direction of core thickness
than the support member.
Because the U-shaped closing portion of the support member is disposed
at the air inlet side of the heat exchanger core, the closing portion
prevents water from entering the inside of the support member even
if water adheres to an upstream portion of the core unit. Therefore,
condensed water can not adhere to the electric heater, and the short
circuiting or electric leak of the electric heater due to water
is prevented. Because the opening portion of the support member
projects from an end of the electric heater, water can be prevented
from adhering to the electric heater even if water moves along the
surface of the support member to the opening portion.
It is another object of the present invention is to provide an
improved core unit of a heat exchanger for heating air by hot water
or engine coolant having a PTC heater which can heat the heating
air at a maximum efficiency.
According to another feature of the present invention, a core unit
of a heat exchanger core includes a plurality of parallelly disposed
flat tubes which conduct the heat carrier, a plurality of corrugated
fins having summits of corrugation disposed between two of the flat
tubes, and an electric heater disposed between two of the summits
of corrugation instead of one of the flat tubes. The electric heater
has a positive temperature characteristic sharply changing resistance
thereof at a set temperature and heats portions of the fins adjacent
to the flat tubes at a temperature equal to temperature of water
in the flat tubes if the water temperature is equal to or higher
than 60.degree. C. and temperature of air to be heated is equal
to or lower than 0.degree. C.
Usually, the diesel engine operates at a high efficiency, and the
water temperature thereof can not rise sufficiently even after engine
has warmed up. In such a highly efficient engine, the water temperature
may not rise up to 60.degree. C. If the water temperature in the
flat tubes does not rise above 60.degree. C., the heat generated
by the PTC heater is not transmitted to the water, so that the PTC
heater can heat the heating air efficiently.
According to another feature of the present invention, a core unit
of a heat exchanger core includes a plurality of parallelly disposed
flat tubes which conduct the heat carrier, a plurality of corrugated
fins each of which is disposed between two of the flat tubes, a
PTC heater disposed at a portion of the core unit instead of the
flat tubes. The corrugated fins have summits of corrugation disposed
between two of the flat tubes which has a height between 3.9 mm
and 5 mm, and the set temperature of the PTC heater is between 85.degree.
C. and 110.degree. C. The electric heater is preferably a three-layered
sandwich structure composed of an electric heater element and two
flat electrodes on opposite sides of the electric heater element
and is inserted between the corrugated fins and the two electrodes,
and the two electrodes are press-fitted to the summits of the corrugation.
The PTC heater may have a heater element whose positive temperature
characteristic sharply changing resistance thereof at temperature
between 120.degree. C. and 170.degree. C.
According to the inventor's study, the height and the set temperature
of the PTC heater are set as the above, the heat of the PTC heater
is not transmitted to the water under the conditions: the heating
air temperature .ltoreq.0.degree. C.; the water temperature in the
flat tubes .gtoreq.60.degree. C.
Further, the height of the fins between 3.9 mm and 5 mm reduces
the difference in the temperature between the fins and the heating
air, so that the corrugated-fin-type heat exchanger core unit can
provide both sufficient heat radiation performance and effective
heating of the heating air by the PTC heater.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects, features and characteristics of the present invention
as well as the functions of related parts of the present invention
will become clear from a study of the following detailed description,
the appended claims and the drawings. In the drawings:
FIG. 1 is a perspective view illustrating a heat exchanger having
an electric heater integrated therewith according to a first embodiment
of the present invention;
FIG. 2 is an enlarged perspective view of a portion where the electric
heater is installed;
FIG. 3A is a fragmentary perspective view of the electric heater
shown in FIG. 2, FIG. 3B is a cross-sectional side view of the electric
heater, FIG. 3C is a cross-sectional elongation of the electric
heater, and FIG. 3D is a plan view of the electric heater;
FIG. 4 is a schematic view illustrating a portion where an electric
heater is disposed,
FIG. 5 is an enlarged perspective view of a portion where an electric
heater of a heat exchanger according to a second embodiment of the
present invention;
FIG. 6 is a cross-sectional view of the portion where the electric
heater shown in FIG. 5 is installed;
FIG. 7 is a schematic view illustrating air flow system of the
vehicle air conditioner including the heat exchanger according to
the second embodiment;
FIG. 8 is a cross-sectional view of a variant of the electric heater
according to the second embodiment of the present invention;
FIG. 9 is a perspective view of a second variant of the heat exchanger
of an electric heater according to the second embodiment of the
present invention;
FIG. 10 is a cross-sectional view of a third variant of the electric
heater according to the second embodiment;
FIG. 11 is a cross-sectional view of a fourth variant of the electric
heater according to the second embodiment;
FIG. 12 is a cross-sectional view of a fifth variant of the electric
heater according to the second embodiment;
FIG. 13 is a cross-sectional view of a sixth variant of the electric
heater according to the second embodiment;
FIG. 14 is a schematic view illustrating a main portion of Ad a
heat exchanger core unit according to a third embodiment of the
present invention;
FIG. 15 is a driving circuit diagram for the PTC heater integrated
in the core unit shown in FIG. 14;
FIG. 16 is a schematic diagram showing temperature distribution
of the corrugated fin adjacent to the PTC heater shown in FIG. 15;
FIG. 17 is a graph showing relationship between the set temperature
of the PTC heater and the height of the corrugated fins at water
temperature of 60.degree. C.;
FIG. 18 is a graph showing relationship between the set temperature
of the PTC heater and the height of the corrugated fins at water
temperature of 80.degree. C.;
FIG. 19 is a graph showing relationship between the set temperature
of the PTC heater and the temperature of the heating air with the
height of the fins being 4.5 mm;
FIG. 20 is a graph showing relationship between the temperature
of the PTC heater and the temperature of the heating air with the
height of the fins being 4.0 mm; and
FIG. 21 is a graph showing temperature distribution of the corrugated
fin.
FIG. 22 is a perspective view illustrating a heat exchanger according
to a fourth embodiment of the present invention;
FIGS. 23A, 23B and 23C are respectively a plan view, a front view
and a side view of a fastening member according to the fourth embodiment;
FIG. 24 is a perspective view of a side plate shown in FIG. 22;
FIG. 25 is a fragmentary enlarged view of the side plate and a
portion of the fastening member in engagement;
FIGS. 26A, 26B, and 26C illustrate a fastening member according
to a fourth embodiment of the present invention;
FIGS. 27A, 27B and 27C illustrate a fastening member according
to a fifth embodiment of the present invention;
FIGS. 28A, 28B, and 28C illustrate a fastening member according
to a sixth embodiment of the present invention; and
FIGS. 29A and 29B illustrate a fastening member according to a
seventh embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Preferred embodiments of the present invention are described with
reference to the appended drawings.
(First Embodiment)
In FIGS. 1 and 2, the heat exchanger for a heater has a hot-water
inlet tank 1, a hot-water outlet tank 2 and a heat exchanger core
unit 3 disposed between the tanks 1 and 2. The hot-water inlet tank
1 has an inlet pipe 4 through which hot water or engine coolant
flows from a vehicle engine (not shown). The hot-water outlet tank
2 has an outlet pipe 5 through which the hot water is discharged
and returned to the engine. The heat exchanger is symmetrical, and
therefore the hot-water inlet tank 1 and the hot-water outlet tank
2 can be exchanged.
The inlet tanks 1 is composed of a tank body 1a, and the outlet
tank 2 is composed of a tank body 2a. Sheet metals 1b and 2b close
the open end of the tank bodies 1a and 2a respectively. The vertical
direction of the heat exchanger in FIGS. 1 and 2 is the longitudinal
direction of the tanks 1 and 2. Each of the sheet metals 1b and
2b has a plurality of elliptic tube receiving holes (not shown).
The elliptic tube receiving holes are formed in the vertical direction
in FIGS. 1 and 2 in a single line or a plurality of lines.
The heat exchanger core unit 3 has a plurality of the flat tubes
6 stacked in the vertical direction. One of a plurality of corrugated
fins 7 is disposed between each pair of the flat tubes 6 and soldered
thereto. Each of the corrugated fins 7 has a plurality of louvers
extending at an angle from the direction A of heating air to increase
the heat exchange rate.
Opposite ends of each of the flat tubes 6 are inserted into corresponding
tube receiving holes of the sheet metals 1b and 2b of the inlet
and outlet tanks 1 and 2 and soldered thereto. Side plate 8a and
8b are disposed on the outermost corrugated fins 7 and are soldered
to the same outermost corrugated fins 7 and to the sheet metals
1b and 2b.
A pair of support plates 10 and 11 is disposed between the summits
of the corrugation of adjacent two of the corrugated fins 7 in place
of one of the flat tube 6 at each one of four portions of the core
unit 3 and extend in parallel with each other at a distance L. The
distance L is the same as thickness of the electric heater 9. Each
of four electric heaters 9 is inserted between the support plates
10 and 11 to be held therein.
Elements and components 1-8b of the core unit 3 as well as the
support plates 10 and 11 are made of aluminum or aluminum alloy.
Each of the support plates 10 and 11 is made of a thin sheet having
thickness between 0.1 and 0.5 mm and width (in the direction of
the hot air) having nearly the same size as the corrugated fins
7. The length (in the horizontal direction in FIG. 1) of the support
plates 10 and 11 is nearly the same as the distance between the
sheet metals 1b and 2b.
The electric heater 9 has a three-layered sandwich structure composed
of a flat heating element 9a and long flat electrodes 9b and 9c
disposed on the opposite surfaces of the heating element 9a as shown
in FIGS. 3A-3D. An insulating cover 9d made of insulating material
covers the circumferences of the electrodes 9b and 9c. The heating
element 9a is a PTC heater element made from resistance material
(such as barium titanate), which has a positive temperature characteristic
increasing the resistance sharply at a set temperature T0 (e.g.
around 200.degree. C.). The thickness of the heating element 9a
is between 1.0-2.0 mm.
The electrodes 9b and 9c are made of aluminum, copper or stainless
or the like and have a thickness between 0.1-0.5 mm. The length
of the electrodes 9b and 9c (horizontal size in FIG. 1) is nearly
equal to the length of the support plates 10 and 11. The heating
element 9a and the electrodes 9b and 9c are pressed to each other
to provide good electric conduction.
The insulating cover 9d is press-fitted into the space between
the support plates 10 and 11 to insulate the support plates 10 and
11 from the plates 9b and 9c and to conduct heat generated by the
heating element 9a to the support plates 10 and 11. For this purpose,
the thickness t1 of the insulating cover 9d disposed between the
support member and one of the plates 9b and 9c is formed between
25.mu.-100.mu..
The thickness t2 of the insulating cover 9d at the opposite sides
of the heating elements is about 1-2 mm to protect the heating elements
9a. The insulating cover 9d is preferably made of high temperature
resistive resin (e.g. polyimide).
Terminals 9e and 9f are formed integrally with the plus electrode
9b and the minus electrode 9c respectively to be connected to an
outside circuit. The terminals 9e and 9f project from the rear side
(down stream side of air flow A in FIG. 1) of the core unit 3. The
terminal 9e is formed at the right side of the plus electrode 9b,
and the terminal 9f is formed at the left side of the minus terminal
9c. Both terminals 9e and 9f may project toward the rear side (air
flow direction A).
The terminals 9e and 9f are connected to an outside circuit (not
shown) so that the electric heaters 9 can be energized by a vehicle
electric source.
Reference numerals 12 and 13 indicate fastening members or bands
made of anticorrosion metal respectively disposed on a surface of
the air inlet side and on a surface of the air outlet side of the
core unit 3. Each of the fastening members 12 and 13 has hook portions
at the opposite ends thereof to engage grooves 8c and 8d formed
at middle of the upper and lower side plates 8a and 8b. The fastening
members 12 and 13 provides the support plates 10 and 11 with fastening
force to hold the electric heater 9.
In assembling, the tubes 6 and corrugated fins 7 are alternately
stacked on one another, and the support plates 10 and 11 are inserted
between the corrugation summits of the corrugated fins 7 which are
located in four hatched portions. In order to keep the distance
between two plates 10 and 11, a dummy spacer (not shown) is inserted
into the support plate 10.
The spacer is made of material (such as carbon) which is resistant
to the soldering heat and is not soldered to aluminum. The tanks
1 and 2, the pipes 4 and 5 and the side plates 8a and 8b are also
assembled in a well-known manner.
The above assembled unit is held by an assembling tool (not shown)
and sent to a brazing furnace to be brazed or soldered. The assembled
unit is heated at a soldering temperature (600.degree. C.) to melt
solder in aluminum clad members of the core unit 3.
Thereafter, the assembled unit is taken out from the furnace and
is cooled until the temperature of the assembled unit goes down
to the ambient temperature. Then, the flat heating element 9a is
inserted between the electrodes 9b and 9c to form the three-layered
sandwich unit, which is covered by the insulating cover 9d.
Thereafter, the dummy spacers are removed from the support plates
10 and 11, and each of the electric heaters 9 is inserted thereto
in a manner that the insulating cover 9d is press-fitted to the
support member 10. Thereafter, the hooks of the fastening members
12 and 13 are engaged with the grooves 8c and 8d of the upper and
lower side plates 8a and 8b to fasten the core unit 3 tight.
In operation, when the passenger compartment is to be warmed, the
motor-driven fan 15 is operated to pass air through the spaces between
the flat tubes 6 and the corrugated fins 7 in the direction indicated
by the arrow A in FIG. 1. On the other hand, a water pump (not shown)
is operated and hot water flows into the inlet tank 1 from the inlet
pipe 4.
The hot water is distributed to a plurality of flat tubes 6 and
transfer the heat thereof to the air to be heated while the water
flows along the flat tubes. All the water flowing along the flat
tubes 6 are collected in the outlet tank 2 and goes out of the outlet
pipe 5 to the engine.
When the temperature of the hot water of the engine is lower than
a preset temperature (e.g. 80.degree. C.), the electric source voltage
of the vehicle is applied across the terminals 9e and 9f of the
electrodes 9b and 9c. consequently, the heating elements 9a are
energized to generate heat, which is conducted to the corrugated
fins 7 via the electrodes 9b and 9c, the insulating cover 9d and
the support plates 10 and 11. Therefore, the air is heated in a
short time even if the water is not sufficiently hot.
Since the heating element 9a is composed of a PTC element which
has a positive temperature characteristic the resistance of which
increases sharply at a preset temperature T0, it regulates the temperature
thereof to the preset temperature by itself.
Since the corrugated fins 7 and the support plates 10 and 11 are
soldered beforehand, the solder melts in the subsequent soldering
step of the core, is guided by the capillarity to the gaps between
the summits of the corrugation of the corrugated fins 7 and support
plate and fills the gaps even though the gaps forms due to irregular
height of the corrugation.
The insulating cover 9d of the electric heater 9 can be made of
adhesive resinous material to bond the electric heater 9 to the
support plates 10 and 11. In this case, the fastening members can
be omitted.
(Second Embodiment)
A second embodiment is described with reference to FIGS. 5-7. As
shown in FIG. 5, each of the portions of the heat exchanger core
unit 3 where the electric heaters are installed has a U-shaped support
member 100 extending in the longitudinal direction of the flat tubes
6 between the summits of the corrugation of adjacent two of the
corrugated fins. A U-shaped closing portion 10a of the support member
100 is located at the air inlet side of the heat exchanger core
unit 3, and the opening portion 10b thereof is located at the air
outlet side of the heat exchanger core unit 3.
The support member 100 has plates 10 and 11 extending in parallel
at a distance L1, and they are soldered to the summits of the corrugations
in the same manner as in the first embodiment. The electric heater
9 is inserted from the opening portion 10b into the inside of the
support member 100 to be held therein. The electric heater 9 is
held by an insulating member as described before.
Total thickness L2 of the support member 100 is same as thickness
L3 of the flat tube 6 so that the support member 100 can be installed
between the corrugated fins 7 instead of the flat tube 6. In FIG.
6, D is the thickness of the core unit 3 as well as the width of
the flat tubes 6 and the corrugated fins 7 in the air flow direction.
Each of the support members 100 is made of a thin sheet having
thickness between 0.1 and 0.5 mm and width (in the direction of
the hot air) having nearly the same size as the core thickness D.
The length (in the horizontal direction in FIG. 1) of the support
member 100 is nearly the same as the distance between the sheet
metals 1b and 2b.
The electric heater 9 has a three-layered sandwich structure composed
of a flat heating element 9a and long flat electrodes 9b and 9c
disposed on the opposite surfaces of the heating element 9a as shown
in FIGS. 5 and 6. An insulating cover 9d covers the electrodes 9b
and 9c. The heating element 9a is a PTC heater element which has
a positive temperature characteristic to increase the resistance
sharply at a prescribed temperature T0 (e.g. around 200.degree.
C.). The thickness of the heating element 9a is between 1.0-2.0
mm.
The electrodes 9b and 9c of the heating element 9a is made of aluminum,
copper, stainless or the like and has the thickness between 0.1-0.5
mm. The length of the electrodes 9b and 9c (horizontal size in FIG.
1) is nearly equal to the length of the support member 100.
Since the support member 100 has the U-shaped closing portion 10a,
the electric heater can be held by a single fastening member 12
disposed on the opening portions 10b.
FIG. 7 illustrates an air conditioner to which a heat exchanger
of a heater H according to this embodiment is installed. Outside
air or inside air is introduced by a motor-driven fan 15 disposed
in the upstream side of a resinous case 14 and sent to an evaporator
16 of the refrigerating cycle to be cooled and dried. The cooled
air is separated by an air-mix door 17 into a flow passing the heat
exchanger H for cooling air and a flow passing a bypass 18 so that
the air heated by the heat exchanger H and the air passing the bypass
18 can be mixed and adjusted by turning the air-mix door 17, thereby
controlling temperature of the air blown into the compartment of
a vehicle.
The present invention can be applied to an air conditioner for
a vehicle in which hot water supplied to the heat exchanger H is
controlled by a hot-water control valve to control the temperature
of the air blown into the vehicle compartment instead of the air-mix
door 17.
In assembling, the heat exchanger core is assembled first. The
tubes 6 and corrugated fins 7 are alternately stacked on one another,
and one of the U-shaped support member 100 which extends along the
tubes 6 is inserted between the corrugation summits of the corrugated
fins 7 which are located in portions (four hatched portions). Other
steps are substantially the same as those of the first embodiment.
In operation, when the passenger compartment is to be warmed, the
motor-driven fan 15 is operated to pass air to be heated through
the spaces between the flat tube and the corrugated fins. On the
other hand, a water pump (not shown) is operated and hot water flows
into the inlet tank 1 from the inlet pipe 4. The hot water is distributed
to a plurality of flat tubes 6 and transfer the heat thereof to
the air to be heated while the water flows along the flat tubes.
All the water flowing along the flat tubes 6 are collected in the
outlet tank 2 and goes out of the outlet pipe 5 to the engine.
When the temperature of the hot water of the engine is lower than
a preset temperature (e.g. 80.degree. C.), the electric source voltage
of the vehicle is applied in the same manner as described before.
As shown in FIG. 7, the heat exchanger H for heating air is disposed
at a downstream side of the heat exchanger 16 for cooling air in
the case of the vehicle air conditioner. Therefore, condensed water
generated in the heat exchanger 16 may be carried by the cooled
air to the heat exchanger H and may adhere to the surface of the
heat exchanger H. Snow may come from the air inlet into the case
14, melt and adhere to the upstream surface of the heat exchanger
H.
The U-shaped closing portions 10a of the support member 100 are
located at the air inlet side of the heat exchanger H, and the opening
portions 10b are located at the air outlet side thereof. Even if
the condensed water adheres to the upstream side of the heat exchanger
H of the heater, the closing portions 10a keep off water or snow
from the electric heater 9.
As shown in FIG. 6, the opening portion 10b projects a little from
the downstream side of the electric heater 9. Even if water moves
along the outer surface of the support members 100 to the opening
portion 10b, the water can not adhere to the surface of the electric
heater 9.
The electric terminals 9e and 9f of the electric heater 9 project
from the downstream side of the heat exchanger core unit 3 in the
air flow A, water does not adhere to the terminals 9e and 9f. Therefore,
deterioration of the terminals 9e and 9f, short-circuiting and electric
leakage can be prevented. Since the electric heaters 9 can be held
in the U-shaped support members 100, the electric heater 9 can be
positioned accurately.
Since the heating element 9a and the electrodes 9b and 9c of the
electric heater 9 are covered by the insulating cover 9d and insulated
from the support plate 10, electric current can not flow into the
metal members of the heat exchanger H, and the electric corrosion
of the metal members such as tubes or fins can be prevented.
FIG. 8 shows a variant of the second embodiment. The opening portion
10b of the support member 100 projects slightly from the end of
the electric heater 9. The opening portion 10b is positioned at
the downstream side of the corrugated fins in the air flow and is
expanded at the end thereof like a skirt. Accordingly, the water
moving along the surface to the opening portion 10b of the support
member 100 is prevented from adhering to the electric heater with
more confidence.
FIG. 9 shows a second variant of the second embodiment. The heat
exchanger H according to the second variant is a type in which hot
water is returned as compared with the heat exchanger H according
to the first embodiment, so called full-pass (one way) type, in
which the hot water flows in one direction in all the flat tubes
from the hot water inlet tank 1 to the hot water outlet tank 2.
In other words, the tank disposed on a side of the core unit 3 is
divided into the hot water inlet tank 1 and the hot water outlet
tank 2, and a connecting tank 19 is disposed to return the water
to the opposite side of the tanks 1 and 2. Hot water is introduced
from the inlet tank 1 through the flat tubes 6 on the left side
of the core unit 3 into the connecting tank 19. From the connecting
tank 19, the hot water is introduced to the outlet tank 2 through
the flat tubes 6 on the right side of the core unit 3 and goes out
from the outlet 5. The electric heater 9 can be installed in this
type in the same manner as in the first embodiment.
FIG. 10 shows a third variant of the second embodiment. Two rows
of the flat tubes 6 are disposed in the thickness of the core and,
therefore, the thickness D of the core unit 3 is about twice as
thick as the thickness of electric heater. A stopper portion 10e
is formed at the middle of the support member 100 to hold the electric
heater 9 in position. The middle portions of the support member
100 are pinched to be in contact with each other. Thus, the same
electric heater 9 can be used to any heat exchanger H of a heater
having core with different thickness.
FIG. 11 shows a fourth variant of the second embodiment. A separate
stopper member (made of resin or metal) 10f is disposed inside the
support member 100.
FIG. 12 shows a fifth variant of the second embodiment. The plate
10 of the support member 100 is pinched to form the stopper 10e.
FIG. 13 shows a sixth variant of the second embodiment. The support
member 100 has a reinforcement rib 10g between the stopper portion
10e and the closing portion 10a. The reinforcement rib 10g is formed
by pinching middle portions of the plates 10 and 11. The reinforcement
rib 10g increases the stiffness of the portion between the stopper
portion 10e and the closing portion 10a. The reinforcement rib 10g
of the seventh embodiment can be formed on either one of the two
plates 10 and 11.
The stopper 10e and the reinforcement rib 10g can be formed along
the whole length of the tubes of the core continuously or intermittently
[Third Embodiment]
The PTC heater 9 shown in FIG. 14 is composed of a flat heating
element 9a and long flat electrodes 9b and 9c disposed on the opposite
surfaces of the heating element 9a. The heating element 9a is a
PTC heater element which has a positive temperature characteristic
to increase the resistance sharply at a prescribed temperature T0.
The electrodes 9b and 9c of the PTC heater element 9a are bonded
by adhesive insulating material 10 to the summits of corrugation
of the corrugated fins 7. The opposite ends of the PTC heater element
9a (horizontal direction in FIG. 1) are bonded by adhesive insulating
material 10 to the sheet metals 1b and 1c. The adhesive insulating
material 10 is made of adhesive, electrically insulating and heat
conductive resin. Heat generated by the PTC heater element 9a is
conducted by the corrugated fins 7 to heat the heating air.
FIG. 15 shows an electric driving circuit of the PTC heater 9.
The four PTC heaters 9 are parallelly connected to a vehicle electric
source BA via a switch SW1. The switch SW1 is controlled by a control
circuit CC. The control circuit CC receives signals from a water
temperature sensor TS for detecting temperature of the water flowing
from the engine into the heat exchanger of a heater and a switch
SW2 operated when the heater operates. If the water temperature
is lower than a certain temperature (e.g. 80.degree. C.), the control
circuit CC turns on the switch SW1 to power the PTC heaters 9.
In operation, an air blower operates and drives air to the spaces
between the flat tubes 6 and the corrugated fins 7. On the other
hand, hot water is driven by a water pump (not shown) installed
in the engine to flow from the engine through the inlet pipe 4 into
the inlet tank 1. Then, the hot water is distributed into a plurality
of the flat tubes 6 to heat the heating air via the corrugated fins
while passing the tubes 6. Thereafter, the hot water flows into
the outlet tank 2, gets together, flows out of the outlet pipe 5
of the heat exchanger and returns to the engine.
If the temperature of water flowing out of the engine is low, the
switch SW1 of the electric circuit closes to power the four PTC
heaters 9. The PTC heaters 9 self-controls the temperature and rises
to the temperature T0, which is transmitted to the heating air through
the adjacent corrugated fins 7. Thus, the heating air is heated
in a short time even if the water temperature is low.
In order to utilize the heat generated by the PTC heater 9 effectively,
the set temperature T0 is an important factor.
FIG. 16 shows temperature distribution of the corrugated fin 7
disposed between the surface of the PTC heater 9 and the surface
of the adjacent flat tube 6.
The following relations expressed by E1 and E2 are known, where
temperature of the heating air flowing in the direction vertical
to the drawing is Tair, set temperature (surface temperature) of
the PTC heater 9 is T0, height of the corrugated fin 7 is hf, height
of a certain position of the corrugated fin 7 is x, and temperature
of the fin at the height x of the certain position is .theta.:
.theta.=cosh[m(hf-x)]/cosh(m.multidot.hf).times.(T0-Tair)+Tair,
E2:
where m is a dimensionless number expresses in the following expression
E3.
where h.sub.0 is a coefficient of heat transfer of the fin surface,
b is a thickness of the fin, and .lambda.f is a coefficient of heat
conductivity of the fin material.
In order to utilize the heat generated by the PTC heater 9 effectively,
the temperature .theta. of the portions of the corrugated fins 7
adjacent to the flat tubes 6 (the portions at x=hf) is made equal
to the temperature Tw of the peripheral surface of the tubes (or
the water temperature in the tubes) in order to prevent the heat
generated by the PTC heater 9 from transferring to the water.
If x=hf, and .theta.=Tw, the expression E1 is expressed by the
following expression E4.
The set temperature T0 of the PTC heater 9 to satisfy the above
condition can be obtained from the following expression E5.
FIG. 17 shows relationship between the height hf of the fin and
the set temperature T0 of the PTC heater 9 with various heating
air temperatures Tair under the following conditions:
the heating air temperature Tair Tw=60.degree. C., h.sub.0 =300
W/m.sup.2 K, b=0.06 mm, .lambda.f=193 W/m K (fin material:A3003).
Thus, m is calculated by the expression E3 as follows:
m=227.626
In the air conditioner for a vehicle, outside dry air is introduced
to the heater in order to prevent frosting of the windshield glass.
Therefore, Tair is the outside temperature in winter. Because a
recent highly-efficient-engine can provide hot water of 60.degree.
C. at the highest in winter, 60.degree. C. is selected as Tw.
FIG. 18 shows relationship between the height hf of the fin and
the set temperature T0 of the PTC heater 9 with various heating
air temperatures Tair when Tw is 80.degree. C. under the same conditions
as above.
FIG. 19 shows relationship between the set temperatures T0 and
the heating air temperatures Tair at various water temperatures
Tw with the height of the corrugated fins being 4.5 mm. When the
water temperature Tw changes from 60.degree. C. to 80.degree. C.
and the heating air temperature Tair is 0.degree. C. or lower, the
set temperature of the PTC heater 9 changes from 96.degree. C. to
126.degree. C.
FIG. 20 shows relationship between the set temperatures T0 and
the heating air temperatures Tair at various water temperatures
Tw when the height of the fins hf is 4.0 mm. When the water temperature
Tw changes from 60.degree. C. to 80.degree. C. and the heating air
temperature Tair is 0.degree. C. or lower, the set temperature of
the PTC heater 9 changes from 87.degree. C. to 118.degree. C.
FIG. 21 is a graph showing relationship between temperatures on
the fin surfaces and distances x of the fin surfaces from the PTC
heater 9 with following conditions:
The height hf is 4.5 mm, the water temperature Tw is 60.degree.
C., and the heating air (outside air) temperature Tair is 0.degree.
C.
If the set temperature T0 of the PTC heater 9 is higher than 100.degree.
C., the temperature of the portions (at x=4.5 mm) of the corrugated
fins 7 adjacent to the flat tubes 6 becomes higher than the temperature
Tw (60.degree. C.) of the water in the flat tubes 6. In this case,
the heat of the corrugated fins, which is transferred from the PTC
heater 9, is transferred to water and the heat generated by the
PTC heater 9 is not utilized efficiently.
In the heat exchanger of a heater for a vehicle, the shorter width
of the elliptic opening of the flat tube 6 is about 1.4 mm. It is
found preferable that the height of the corrugated fins 7 is equal
to or larger than 3.9 mm in combination with the above sized tubes.
If the height of the fins is less than 3.9 mm, the ratio of the
heat conduction area of the corrugated fins to the number of the
flat tubes 6 is too small to have a sufficient heat radiation capacity.
The height hf of the fins is, preferably, smaller than 5 mm. Otherwise,
temperature of the middle portions of the corrugated fins becomes
excessively lower than the temperature of the portions of the corrugated
fins 7 adjacent to the tubes. This reduces the difference between
the fin temperature, and the heating air temperature becomes too
small for efficient heat transfer. Thus, the desirable height hf
of the corrugated fins 7 is between 3.9 and 5.0 mm.
In FIG. 17, when the heating air (outside air) Tair is 0.degree.
C., the set temperature T0 of the PTC heater 9 is between 80.degree.
C. and 120.degree. C. if the height hf of the fins being between
3.9 and 5.0. In order to provide the above set temperature in this
embodiment, the heater element 9a has positive temperature characteristic
sharply changing the resistance thereof at temperature between 120.degree.
C. and 170.degree. C.
(Fourth Embodiment)
In FIG. 22, a heat exchanger H for a heater, according to a fourth
embodiment of the invention, has a hot-water inlet tank 1, a hot-water
outlet tank 2 and a heat exchanger core unit 3 disposed between
the tanks 1 and 2. The hot-water inlet tank 1 has an inlet pipe
4 through which hot water or engine coolant flows from a vehicle
engine (not shown). The hot-water outlet tank 2 has an outlet pipe
5 through which the hot water is discharged and returned to the
engine. The heat exchanger is symmetrical, and therefore the hot-water
inlet tank 1 and the hot-water outlet tank 2 can be exchanged. Thus,
the heat exchanger H is almost the same in basic construction, and,
therefore, portions different from the first embodiment is described
hereafter.
The electric heater 9 has the same three-layered sandwich structure
as described with reference to FIGS. 3A-3D. The heating element
9a is a PTC heater element made from resistance material (such as
barium titanate), which has a positive temperature characteristic
increasing the resistance sharply at a set around 200.degree. C.
An electric wire cover 2c is fixed to the outlet tank 2. The wire
cover 2c is a flexible member made of resinous material such as
polypropylene covering peripheral portion of the outlet tank. The
wire cover 2c has a detachable member for elastically engaging with
a portion of the outlet tank 2 and three terminal portions 26, 27,
and 28. A positive connector 22 with its three lead wires 23 and
a negative connector 24 with its three lead wires 25 are respectively
connected, at the three terminal portions 26, 27 and 28, to the
electrodes 9b and 9c of the PTC heater element 9a via connection
members (not shown) and held by the wire cover 2c. The positive
and negative connectors 22 and 24 are connected to an outside control
circuit (not shown) so that electric power can be supplied to the
electric heaters 9.
A pair of elastic fastening members 12 are located at the air outlet
side of the core unit 3. Each of the fastening members 12 has hook
portions 12b at the opposite ends thereof to engage grooves of the
side plates 8a and 8b. Thus, the pair of fastening members 12 are
disposed between upper and lower side plates 8a and 8b, so that
the fastening members 12 can provide the support plates 10 and 11
with force to hold the electric heater 9. The number of the fastening
members 12 can be reduced to one, or increased to three according
to circumstances of the heat exchanger in use.
The fastening member 12 is made of a thin steel plate that is as
thick as about 1 mm and has a slender band portion 12a, a pair of
hook portions 12b and 12c, and a hole 12d, as shown in FIGS. 23A
and 23B. The pair of hook portions 12b and 12c is as wide as about
10 mm, and the band portion 12a is as wide as about 4 mm. In other
words, the width W2 of the band portion 12a is less than one half
(1/2) of the width W1 of the hook portion 12b or 12c. This reduces
a draft resistance or draft loss of air passing through the core
unit 3. The pair of hook portions 12b and 12c is connected to the
band portion 12a by neck portions 12e having gradually narrowing
arc-shaped or tapering sides.
The hook portion 12b or 12c has an arc-shaped portion 121b or 121c.
The hook portion 12b has a nail portion 122b which extends further
inward. On the other hand the hook portion 12c has an inward projection
122c and a guide portion 123c which extends axially outward.
As shown in FIG. 24, each of the side plates 8a and 8b has longitudinally
extending reinforcement ribs 81a forming grooves 81b therebetween.
The reinforcement ribs 81a prevent the corrugated fins 7 from buckling.
The hole 12d is formed to be engaged with a hanger of a transfer
machine of a plating process for plating the fastening members 12
with anticorrosion metal.
The hook portion 12b of the pair of fastening members 12 is put
on the upper side plate 8a so that the nail portion 122b can be
fitted to one of the grooves 81b as shown in FIG. 25. Then, the
hook portion 12c thereof is brought to the lower side plate 8b so
that the inward projection 122c can be guided by the guide portion
123c and fitted into one of the grooves 81b of the lower side plate
8b. As a result, the fastening force of the fastening member 12
is applied to one of the rib 81a of the core unit 3 as indicated
by an arrow B. Because of the elasticity of the hook portions 12b
and 12c as shown in FIG. 23B, the fastening members 12 can hold
the core unit 3 tight irrespective of variations in size thereof.
This provides a high productivity.
The heat exchanger H according to the fourth embodiment is assembled
almost in the same manner as the heat exchanger according to the
first embodiment.
(Fifth Embodiment)
As shown in FIGS. 26A and 26B, The hook portions 12b of the fastening
member 12 is the same in shape as the hook portion 12c. Therefore,
it is not necessary to distinguish one hook portion from the other.
(Sixth Embodiment)
As shown in FIGS. 27A and 27B, the neck portion 12e is removed
to reduce the draft resistance a little more.
(Seventh Embodiment)
As shown in FIGS. 28A and 28B, the band portion 12a is as wide
as the hook portions 12b and 12c. Instead, the band portion 12a
has a longitudinal draft opening 12f. The draft opening 12f can
be divided into two or more openings.
(Eighth Embodiment)
As shown in FIGS. 29A and 29B, the band portion 12a has a plurality
of bends 12g projecting forward from the core unit 3. This makes
the fastening members more flexible to improve the assembling productivity.
The present invention can be applied to various heat exchanger
core having fins other than the corrugated fins, such as plate fins
or the like.
The position of the PTC heater 9 can be changed in accordance with
various specifications of the heat exchanger of the heaters.
In the foregoing description of the present invention, the invention
has been disclosed with reference to specific embodiments thereof.
It will, however, be evident that various modifications and changes
may be made to the specific embodiments of the present invention
without departing from the broader spirit and scope of the invention
as set forth in the appended claims. Accordingly, the description
of the present invention in this document is to be regarded in an
illustrative, rather than restrictive, sense.
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