U.S. patent application number 10/628070 was filed with the patent office on 2005-01-27 for fluid heater with integral heater elements.
Invention is credited to Harris, Daryl G., Kuebler, Karl-Heinz.
Application Number | 20050019028 10/628070 |
Document ID | / |
Family ID | 34080724 |
Filed Date | 2005-01-27 |
United States Patent
Application |
20050019028 |
Kind Code |
A1 |
Kuebler, Karl-Heinz ; et
al. |
January 27, 2005 |
Fluid heater with integral heater elements
Abstract
A heat source is disposed in a thermally conductive mass for
imparting heat to the mass. Fluid in a flow path through the mass
absorbs heat from the mass. Substantially all of the surface area
of one or more heater elements forming the heat source are insert
molded in the mass in direct contact to the mass. The mass may be
cast using a sub-liquidous temperature material for low porosity
and high thermal conductivity.
Inventors: |
Kuebler, Karl-Heinz; (Grand
Blanc, MI) ; Harris, Daryl G.; (Oxford, MI) |
Correspondence
Address: |
Andrew R. Basile
Young & Basile, P.C.
Suite 624
3001 West Big Beaver Road
Troy
MI
48084
US
|
Family ID: |
34080724 |
Appl. No.: |
10/628070 |
Filed: |
July 25, 2003 |
Current U.S.
Class: |
392/484 |
Current CPC
Class: |
F24H 9/2028 20130101;
B60S 1/488 20130101 |
Class at
Publication: |
392/484 |
International
Class: |
F24H 001/10 |
Claims
What is claimed is:
1. A heater apparatus for heating fluid, the heater apparatus
comprising: a thermally conductive mass; heating means, insert
molded in contact with the thermally conductive mass, for imparting
heat to the thermally conductive mass; and a fluid flow path formed
in the mass between an inlet and an outlet, the fluid flow path
coupled in heat transfer relation to the heating means so that
fluid in the fluid flow path absorbs heat from the thermally
conductive mass, the fluid flow path open to the exterior of the
thermally conductive mass;
2. The heater apparatus of claim 1 further comprising: control
means, connected to the heating means, for activating the heating
means.
3. The heater apparatus of claim 1 wherein the control means
further comprises: a printed circuit board.
4. The heater apparatus of claim 1 wherein the control means
further comprises: temperature sensor means, coupled to the control
means, for generating an output signal proportional to the
temperature of the thermally conductive mass.
5. The heater apparatus of claim 1 wherein the fluid expansion
means comprises: a closure having an enlarged portion defining a
hollow interior chamber overlaying the open ends of the fluid flow
channels in the thermally conductive mass;
6. The heater apparatus of claim 1 wherein the fluid flow path
comprises: a first flow path portion extending across one surface
of the thermally conductive mass; and a second flow path portion
extending across an opposed surface of the thermally conductive
mass, the first and second flow path portions disposed in fluid
flow communication.
7. The heater apparatus of claim 8 wherein the first and second
flow path portions are disposed in fluid flow communication
substantially at the center of the thermally conductive mass.
8. The heater apparatus of claim 1 wherein the heating means
comprises: at least one heater element mounted in the mass.
9. The heater apparatus of claim 8 wherein the heating means is in
direct contact with the thermally conductive mass over a
substantial portion of its outer surface.
10. The heater apparatus of claim 1 wherein the heating means
comprises: a plurality of heater elements mounted in the mass.
11. The heater apparatus of claim 11 further comprising: a
controller for controlling the activation of each of the heater
elements.
12. The heater apparatus of claim 1 further comprising: a closure
fixed to one surface of the mass; and seal means for fluidically
sealing the thermally conductive mass to the closure.
13. The heater apparatus of claim 12 wherein the seal means
comprises: an O-ring disposed between the peripheral portions of
the closure and the thermally conductive mass.
14 The heater apparatus of claim 1 further comprising: an
electrical ground member electrically connected to the heating
means, the ground member including a terminal and a plate
electrically connected to the terminal and to the heating
means.
15. A method for heating fluid comprising the steps of: providing a
thermally conductive mass having at least one fluid flow path
extending therethrough; and insert molding a heater means in the
thermally conductive mass, with a substantial portion of the heater
means in contact with the mass.
16. The method of claim 15 further comprising the step of:
providing a ground terminal in electrical contact with the at least
one heater element.
17. The method of claim 15 wherein the step of providing a
thermally conductive mass further comprises the step of: casting
the mass using a sub-liquidous temperature material.
18. A method for heating fluid comprising the steps of: providing a
thermally conductive mass having at least one fluid flow path
extending therethrough; and insert molding a heater means in the
thermally conductive mass, with a substantial portion of the heater
means in contact with the mass; and fluidically coupling a fluid
inlet to one end of the fluid flow path and a fluid outlet to the
other end of the fluid flow path wherein fluid in the fluid flow
path absorbs heat from the thermally conductive mass, the heat
imparted to the mass by the at least one heater element.
Description
BACKGROUND
[0001] This invention relates, in general, to fluid heater
apparatus and, more particularly, to fluid heater apparatus which
provides a heated wash fluid to a cleanable surface, and, still
more specifically, to a heated wash fluid apparatus for a vehicle
windshield wash system.
[0002] It is necessary in many diverse applications to quickly
elevate the temperature of a fluid to a higher use temperature. For
example, it is desirable to be able to provide instant hot water,
for use in homes, offices and campers, as well as for industrial
processes.
[0003] In cleaning applications, it is known that hot fluid removes
dirt and other debris from a surface much better and much faster
than colder fluids. One heated fluid application is a vehicle wash
fluid system, such as a windshield wash system as well as vehicle
wash systems applied to camera lenses, exterior lamps and lamp
lenses, mirrors, etc. Vehicles are typically provided with at least
one and usually multiple windshield washers which are used to clear
the field of vision in a windshield or rear backlight.
[0004] Typically, a nozzle or spray device is provided adjacent to
or as part of the windshield wiper to disperse a pattern of wash
fluid onto the windshield prior to and during the wiping operation
to improve the efficiency of the wiping operation so as to provide
a clear field of vision for the driver or vehicle passengers. The
wash fluid is typically stored in a reservoir in the engine
compartment and is pumped through the spray device upon manual
activation of a control actuator by the vehicle driver.
[0005] Since it is known that warm or heated fluid provides better
cleaning efficiency than cold fluid, it is known to provide a
heated wash fluid to a vehicle window spray device. Various wash
fluid heating devices have been developed, but all typically
utilize a heat exchanger design wherein a heat source is disposed
in a body through which the wash fluid flows. The wash fluid picks
up heat in the heat exchange body which elevates its temperature
prior to dispersion through the spray nozzle onto a vehicle
window.
[0006] To provide enhanced thermal conductivity for more efficient
heat transfer from the heater elements to the fluid being heated, a
fluid heater has been previously devised and assigned to the
Assignee of the present invention in which one or more heater
elements are mounted in and substantially encompassed by a
thermally conductive mass or body. A fluid flow channel is formed
in the body. Heat generated by activation of the heater elements is
transmitted to the thermal mass to elevate the temperature of the
thermal mass. The heat of the thermal mass is in turn transmitted
to the fluid flowing between an inlet and an outlet of the fluid
flow channel to elevate the temperature of the fluid as it is
discharged from the outlet.
[0007] In this prior construction, bores were formed by expensive
machining operations, i.e. milling or drilling, etc. in the thermal
mass to receive the heater elements. Tool chatter, manufacturing
tolerances in the diameter of the heater elements and the bore
requires clearance for insertion of the heater elements in the
bores. This causes air gaps between portions of the exterior
surfaces of the heater elements and the adjacent interior surfaces
of the bores in the thermal body. Since air acts as an insulator to
heat transfer, such gaps cause a loss of thermal efficiency of the
heat transmitted by the heater elements to the thermal mass due to
the lack of direct contact of the heater elements to the thermal
mass.
[0008] Thus, it would be desirable to provide a fluid heater
apparatus which has improved heat transfer from a heat source to a
fluid being heated.
SUMMARY
[0009] The present invention is a fluid heater apparatus, in one
aspect of which, at least one or more heater elements are fixedly
mounted in the mass through insert molding with the mass.
[0010] The material used to form the thermal mass may be any
material having a high thermal conductivity. Aluminum, aluminum
particles and ceramics may be advantageously employed.
[0011] The thermal mass may also be formed by sub-liquidous
processes, such as squeeze casting, thixocasting, rhiocasting, etc.
The end result of the use of these processes is a dense thermal
mass with low porosity or void space. This contributes to a high
thermal conductivity.
[0012] The fluid heater of the present invention has increased
thermal conductivity since substantially all of the exterior
surface of the heater element directly contacts the surrounding
thermally conductive mass for optimum heat transfer to the thermal
mass from the heater element.
BRIEF DESCRIPTION OF THE DRAWING
[0013] The various features, advantages and other uses of the
present invention will become more apparent by referring to the
following detail description and drawing in which:
[0014] FIG. 1 is a block diagram of a fluid heater apparatus
according to the present invention used in an exemplary vehicle
window wash fluid delivery system;
[0015] FIG. 2 is a perspective view of a heater module or the fluid
heater apparatus according to one aspect of the present
invention;
[0016] FIG. 3 is an exploded perspective view of the heater module
shown in FIG. 2;
[0017] FIG. 4 is a partially broken away, perspective view of the
assembled heater module shown in FIG. 2, oriented with the circuit
board upward;
[0018] FIG. 5 is a partially broken away, perspective view of the
heater module shown in FIG. 2, with the opposite surface oriented
upward;
[0019] FIG. 6 is a perspective view of the heater module in the
orientation of FIG. 5 of the present invention, without the covers
and the circuit board;
[0020] FIG. 7 is a perspective view of the circuit board side of
the heater module, without the covers;
[0021] FIG. 8 is a perspective view of the opposite orientation of
the heater module shown in FIG. 7;
[0022] FIG. 9 is a top perspective view of the heater module
thermal mass;
[0023] FIG. 10 is a bottom elevational view of the heater module
thermal mass shown in FIGS. 6-8;
[0024] FIG. 11 is an enlarged plan view of the heater module shown
in FIGS. 6-8;
[0025] FIG. 12 is a cross-sectional view generally taken along line
12-12 in FIG. 11;
[0026] FIG. 13 is a cross-sectional view generally taken along line
13-13 in FIG. 11;
[0027] FIG. 14 is a plan view of the freeze protection element
shown mounted over the seal on one surface of the thermal
conductive;
[0028] FIG. 15 is a side elevational view of another aspect of a
heater module which an alternate fluid expansion member according
to the present invention; and
[0029] FIG. 16 is a cross-sectional view, generally similar to FIG.
12, but showing another aspect of the present invention.
DETAILED DESCRIPTION
[0030] Referring now to FIG. 1, there is depicted an environment in
which a heater apparatus or module 10 constructed in accordance
with the teachings of the present invention can be advantageously
utilized. Although the following use of the heater module 10 of the
present invention is described in conjunction with a vehicle window
wash system, it will be understood that the present heater module
may be employed in other applications requiring heated fluid, such
as any cleaning system used to clean any vehicle window, i.e., the
windshield, rear backlight, or side windows, as well as cleaning
systems for vehicle mirrors, camera, lenses, or sensor covers,
etc.
[0031] As is conventional, a vehicle window 12, such as a
windshield, rear backlight or window, etc., has one or more fluid
delivery devices, such as spray nozzles 14 located in a position to
dispense or spray a pattern 16 of wash fluid onto the exterior
surface of the window 12. The dispersion of the wash fluid 16 is
usually in conjunction with activation of a windshield wiper 18
over the window 12.
[0032] The wash fluid 16 is supplied from a fluid source, such as a
reservoir or container 20. The fluid in the reservoir 20 is pumped
to the nozzle(s) 14 by means of a pump 22 usually located in close
proximity or attached to the reservoir 20.
[0033] As is conventional, an on/off switch 24, which may be
mounted on a vehicle steering column stalk switch, is suppled with
power from the vehicle battery 26 and enables the vehicle driver to
control the on or off operation of the wash pump 22.
[0034] According to the invention, the wash fluid pumped from the
reservoir 20 to the spray nozzles 14 is heated from ambient
temperature to a predetermined higher temperature, such as about
65.degree. C. to about 70.degree. C., by example only, by the
heater module 10. A suitable control circuit or controller 28 is
provided for controlling the operation of the heater elements in
the heater module 10. The controller 28 is also supplied with
electric power from the vehicle battery 26. The controller 28 is
activated by a "on" signal from the vehicle ignition 30 so as to
heat the fluid contained within the flow paths in the heater module
10, as described hereafter, whenever the vehicle ignition is in an
"on" state.
[0035] An optional on/off switch 25 may be connected between the
battery 26 and the controller 28 to provide on and off operation
for the entire heater system by disconnecting power to the
controller 28. This enables the heater system to be activated or
remain in an inactive state at the selection of the vehicle driver.
As described hereafter, the on/off switch 25 may also be replaced
by a separate input signal to the controller 28 from an external
signal source, such as a vehicle body controller, to provide for
selective deactivation of the heater module 10 under certain
circumstances, such as a thermal event, low battery power, etc.
[0036] Referring now to FIGS. 2-14, there is depicted one aspect of
the heater module 10 according to the present invention.
[0037] The heater module 110 includes a heat exchange mass or body
140 formed of a suitable high thermally conductive material.
Although the mass 140 is described as being formed of die-cast,
molded, or cast or machined aluminum, other materials, either
homogenous or nonhomogeneous, may also be employed. For example,
the mass 40 can be formed of alumina particles, ceramic materials,
etc. The use of molding or casting techniques enables highly
thermally conductive and moldable materials to be employed for the
thermal mass 140. For example, the mass 40 may be formed of a
highly conductive ceramic material, such as aluminum oxide,
aluminum nitride, boron nitride or magnesium oxide which can be
molded or cast into the shape of the thermal mass 140 described
hereafter and shown in FIGS. 2-14. The use of ceramic material
forms a compact, dense mass of low porosity which provides the
desired high thermal conductivity between the heater elements
mounted in the mass, the mass itself and the fluid flowing through
the mass.
[0038] When a casting process is employed, the heat transfer rate
and/thermal conductivity of the material forming the thermal mass
140 can be improved when a solid, low porosity material is
utilized. Material processing methods, such as squeeze casting,
thixocasting, rhiocasting, machining of a solid mill block, etc.,
can be advantageously employed since such processing methods remove
or minimize the porosity or voids for the final formed mass. This
enables the thermal conductivity of the thermal mass 140 to be
significantly increase.
[0039] The thixocasting and rhiocasting processes as described in
U.S. Pat. Nos. 6,311,759; 6,372,063; 6,200,396; 5,968,292; and
5,803,154, by way of example, the contents of which are
incorporated herein by reference, generally utilize semi-solid
materials where a precursor material of a suitable aluminum or
other highly thermally conductive material which has been formed
with a gobular a-AL phase and cooled into a slug, is placed in a
heating device, heated into the semi-solid region between the
solidus and liquidus temperatures and then injected or poured into
a casting mold.
[0040] The end result of these processes is a dense mass with low
porosity or void space. The lower porosity or void space
contributes to a higher thermal conductivity since air normally
trapped within such voids or interstices reduces the thermal
conductivity of the entire mass due to its insulating
properties.
[0041] For example, the heat transfer rate material effect for a
standard casing of 380 aluminum has a thermal conductivity of
approximately 96.2 W/m.degree. C. compared to a pored rhiocast or
thixocasting with a thermal conductivity of approximately 161
W/m.degree. C. using 356/357 aluminum.
[0042] When an application economically allows the use of a more
expensive aluminum material, the resulting heat transfer rate
material effect of a thixo or rhiocast material can reach
approximately 228 W/m.degree. C.
[0043] A thermal mass, similar to the thermal mass 140, with a
different shape or cross-section can also be formed of various
materials, such as aluminum, ceramics and poltruded carbon
materials by extrusion.
[0044] Regardless of which of the above mentioned materials and
processing techniques are used to form the thermal mass 140, the
present invention provides a thermal mass 140 with low porosity and
low internal void and interstitial spaces thereby providing the
thermal mass 140 with a high thermal conductivity for high heat
transfer between the heating elements through the thermal mass 140
to the fluid flowing through the channels in the thermal mass, as
described hereafter.
[0045] The heat exchange mass 40 is disposed within an enclosure or
housing formed by a first cover 50 and a second mating cover 52.
The first and second covers 50 and 52 have complementary mating
edges. The first cover 50 has a major wall surface 54 and a
surrounding peripheral lip 60.
[0046] The mass 40, as described in greater detail hereafter,
includes a fluid flow path between an inlet 42 and an outlet 44.
The inlet and outlet 42 and 44, respectively, each receives a
fitting 46 for receiving a fluid sealed connection to a fluid flow
conduit, element or tube, not shown. The inlet 42 will be connected
to receive the pump output from the window wash fluid reservoir 20;
while the outlet 44 will be connected to the spray nozzle(s)
14.
[0047] As vehicles typically have several spray nozzles 14, usually
one for each of the two windshield wipers, and at least one nozzle
14 for the rear backlight or rear window wiper, it will be
understood that the following description of a single heater module
10 for heating all of the fluid discharge from the fluid reservoir
20 will encompass multiple parallel paths, each containing a
separate heater module, for heating fluid from the reservoir 20 for
each different nozzle 14.
[0048] The heat exchange mass 40 is disposed within an enclosure or
housing formed by a first cover 50 and a second mating cover 52.
The first and second covers 50 and 52 have complementary mating
edges. The first cover 50 has a major wall surface 54 and a
surrounding peripheral lip 60.
[0049] A necked-down end portion 64 is formed in the first cover
50, and forms a tubular extension from one portion of the major
wall surface 54. The necked-down portion 64 forms an enclosure for
receiving a connector assembly 70 which provides electrical
signals, power and ground to the heating element(s) mounted in the
joined first and second covers 50 and 52 and to a circuit board,
described in detail hereafter.
[0050] The second cover 52 also has a major wall surface 56 and a
surrounding peripheral lip 62 projecting therefrom. The peripheral
lip 62 surrounds the entire periphery of the second major wall
surface 56.
[0051] The first and second covers 50 and 52 are fixedly joined
together, after the thermal mass 40 and the connector assembly 70
has been disposed within the first and second covers 50 and 52 by
suitable means, such as by heat, sonic or vibration welding. By
example, a peripheral groove 76 projects at least partially around
the entire edge of the peripheral lip 60. The groove 76 receives a
mating projection 77 extending around the peripheral lip 62 of the
second cover 52. The projection 77 and groove 76 are fixedly and
sealingly joined together by welding to fixedly join the covers 50
and 52 together.
[0052] Locating means are provided for locating and fixing the
thermal mass 40 to the first and second covers 50 and 52. At least
one and preferably a pair of circumferentially spaced slots 79 and
81, are formed on webs 83 extending between two bosses receiving
the threaded fasteners on the mass 40. The slots 79 and 81 receive
projections 85 and 87 carried on flanges in the first and second
covers 50 and 52 at circumferentially spaced locations
complementary to the location of the slots 79 81 in the mass 40.
The projections 85 and 87 are welded together when the covers 50
and 52 are subjected to a sonic, heat or vibration welding process.
In this matter, the thermal mass is fixedly positioned within the
covers 50 and 52 when the covers 50 and 52 are themselves joined
together.
[0053] A pair of seal elements 71 and 72, each having a ring shape
with another edge substantially the same as the peripheral shape of
the heat exchange mass 40 are disposed on opposite surfaces of the
heat exchange mass 40 as shown in FIG. 3. The seal members 71 and
72 are formed of a high thermal resistant, insulating material. The
seal members 71 and 72 seal the periphery of the heat exchange mass
40.
[0054] Upper and lower closures or plates 73 and 74, each also
having a shape complimentary to the shape of the heat exchange mass
40, are disposed in contact with the upper and lower seals 71 and
72, respectively, and fixed thereto by suitable fastening means,
such as nuts and bolts 75, which extend through apertures in each
of the upper and lower plates 73 and 74, and peripherally located
bores in heat exchange mass 40. The solid peripheral edges of the
plates 73 and 74 and the mating peripheral edges of the heat
exchange mass 40 trap the seals 71 and 72 therebetween to seal the
joint between the plates 73 and 74 and the mass 40. The upper and
lower plates 73 and 74 are formed of a good thermally conductive
material, such as aluminum.
[0055] As shown in detail in FIGS. 6-11, the heat exchange mass 40
has a solid cubical shape formed of a first major surface 80, a
second opposed major surface 82, and four sidewall portions 84, 86,
88 and 90, interconnecting the first and second surfaces 80 and
82.
[0056] A plurality of interior surfaces 92, 94 and 96 are formed in
the body 40 and project inwardly from the sidewall 84. The surfaces
92, 94 and 96 each contact one generally cylindrical heater
element. As partially shown in FIG. 11, each surface 92, 94 and 96
extends through the solid central portion of the mass 40 so as to
be completely surrounded by the solid material of the mass 40. This
defines the mass 40 as a heat source after receiving heat from the
heater elements contacting each 92, 94 and 96.
[0057] In the invention, the heater elements may be formed of
"calrod". Although different materials may be used, one example of
a calrod construction is a Nichrome wire inside of a stainless
steel sheath.
[0058] By way of example only, at least one and preferably a
plurality, i.e., two, more individual heater elements, with three
heater elements 100, 102 and 103, depicted by way of example only,
are disposed in contact with the surfaces 92, 94 and 96,
respectively. The function of the one or more heater elements, such
as heater elements 100, 102 and 103 will be described hereafter in
conjunction with the operation of the heater module 10.
[0059] As described above, the heat exchange or thermal conductive
mass 40 can be formed by molding or casting either a flowable or
molten material into a suitably formed mold cavity or by the
introduction of a metal, such as aluminum, at a semi-solid
temperature between the liquidus and solidus temperatures into a
mold cavity. Prior to the introduction of the thermal conductive
material into the mold cavity, the heater elements 100, 102 and 103
are fixably mounted in the cavity, with an end portion extending
outwardly from the mold cavity. The heater elements 100, 102, and
103 are thereby insert molded in the thermal conductive material as
a monolithic or unitary part of the 40 when the thermal conductive
material solidifies. This places substantially all of the exterior
surface of each of the heater elements 100, 102, and 103 in direct
contact with the interior surfaces 92, 94, and 96 in the body 40 so
as to maximize heat transfer via conduction from the heater
elements 100, 102, and 103 to the body 40.
[0060] Any air gaps or spaces between the exterior surface of the
heater elements 100, 102 and 103 and the adjacent interior surfaces
92, 94 and 96 which could decrease thermal transfer from the heater
elements 100, 102 and 103 to the body 40 due to the insulating
characteristics of air are minimized or eliminated.
[0061] As seen in FIGS. 4 and 7, one end 104, 106 and 107 of each
heater element 100, 102 and 103, respectively, projects outwardly
through the sidewall 84 of the body 40. The ends 104, 106 and 107
of the heater elements 100, 102 and 103, respectively, each have
individual terminals 108 extending therefrom and joined thereto by
soldering, welding, etc., for connection to mating sockets or
contact spring mounted on a printed circuit board 150, itself
mounted by means of fasteners, i.e., screws, rivets, or adhesives,
etc., to an exterior surface of the plate 73. Conductive traces in
the printed circuit board 150 are connected to sockets or contacts
which receive the terminals 108. Two of the connector terminals 70
are soldered to the printed circuit board 150 to receive power,
ground and control signals from the vehicle electrical system.
[0062] In FIG. 8, a ground terminal or connection is provided for
the exterior sheath of the heater elements 100, 102 and 103. One of
the terminals 70 includes a depending flange portion of a ground
plate which is fixed, such as by welding, to the normally stainless
steel exterior sheath of the heater elements 100, 102 and 103
exteriorly of the mass 40.
[0063] As shown in FIGS. 9 and 10, the thermally conductive mass 40
includes a fluid flow channel or path which extends from the inlet
42 to the outlet 44. The fluid flow path is, by example, a
labyrinthian path formed of a first fluid flow path portion 130 and
a second fluid flow path or channel 132 which are connected at a
generally centrally disposed bore 134. The first fluid flow channel
130 has a generally spiral shape formed of alternating straight and
arcuate sections which alternately create laminar and turbulent
flow of the fluid passing through the first flow channel 130 to
maximize the heat absorption of the fluid from the adjoining walls
of the mass 40. Further, the first fluid flow channel 130 has an
inward directed spiral shape from the inlet 42 to the bore 134 to
minimize temperature differential between adjoining portions of the
spiral shaped first flow channel 130.
[0064] As shown in FIG. 10, the second fluid flow channel 132 has a
substantially identical spiral shape. However, fluid flow through
the second fluid flow channel 132 is in an outward spiral direction
from the bore 134 to the outlet 44.
[0065] Thus, fluid flow through the first and second flow channels
130 and 132 starts from the inlet 44 then continues in a spirally
inward directed manner through the first flow channel 130 to the
central passage or bore 134. Upon exiting the central passage 134
into the second flow channel 132, fluid flow progresses in an
outward spiral direction through the second flow channel 132 to the
outlet 44.
[0066] In operation, the heater module 40 will be interconnected in
the vehicle wash fluid flow lines between the pump 22 and the spray
nozzle(s) 14 as shown in FIG. 1. The external connector is then
connected to the connector housing 70 to provide electric power
from the vehicle battery 26 and the controller 28 to the heater
elements 100, 102 and 103, in the heat exchange body 40.
[0067] Assuming that the first and second fluid flow channels 130
and 132 in the body 40 are filled with fluid, when the controller
28 activates the heater elements 100, 102 and 103, the heater
elements 100, 102 and 103 will begin radiating heat which will
immediately raise the temperature of the entire surrounding portion
of the heat exchange body 40. Heat from the body 40 will, in turn,
be radiated to and absorbed by the fluid disposed in the first and
second flow channels 130 and 132.
[0068] The straight and arcuate portions of the first and second
fluid flow channels 130 and 132 create alternating turbulent and
laminar flow regions in the fluid flowing through the mass 40 which
causes movement of the fluid in the first and second flow channels
130 and 132 bringing all molecules in the fluid in contact with the
wall of the body 40 forming the first and second flow channels 130
and 132 to efficiently absorb the maximum amount of heat possible.
This causes the temperature of the fluid to be quickly raised from
ambient temperature at the inlet 42 to approximately 160.degree.
F.-170.degree. F. at the outlet 44 in approximately sixty
seconds.
[0069] The fluid in the first and second fluid flow channels 130
and 132 removes or absorbs heat from the thermal mass 40 thereby
increasing the fluid temperature by physical contact with the mass
40. The heater elements 100, 102 and 103 maintain the heat of the
thermal mass 40 at a predetermined temperature thereby preventing
hot spots from occurring in the fluid. Normally, hot spots would
occur when the fluid comes in direct contact the heater elements
100, 102 and 103. Fluid which is not in physical contact with the
heater elements 100, 102 and 103 passes the heater elements 100,
102 and 103 by and does not absorb heat. By heating the thermal
mass 40, the physical hot contact area is increased along with an
increase in heat transfer efficiency. This requires less energy to
heat the same volume of fluid.
[0070] Although a single heater element 100 may be employed as the
heat source in the body 40, multiple heater elements, with two or
three heater elements, 100, 102 and 103, being described by way of
example only, have been found to be most advantageous. The
controller 28 can activate all of the plurality of heater elements
100, 102 and 103 upon receiving a first command to dispense heated
wash fluid onto the windshield 12. This generates a maximum amount
of heat to the body 40 to immediately and quickly raise the
temperature of the body 40 high enough to transfer sufficient heat
to the fluid in the fluid flow channels 130 and 132 to raise the
temperature of the fluid to the desired discharge temperature of
about 65.degree. C. to about 70.degree. C. The multiple heater
elements 100, 102 and 103 can remain in an activated state by the
controller 28 if immediate and successive commands from the on/off
switch 24 are supplied by the vehicle driver to supply additional
charges of fluid onto the windshield 12.
[0071] At the completion of the fluid dispensing operation, and
during other periods of non-fluid dispensing while the vehicle
engine is running or the engine is running and a dashboard mounted
switch, for example, is activated, the controller 28 can cyclically
activate one or more of the heater elements, such as heater element
100, to maintain the temperature of the fluid in the first and
second flow channels 130 and 132 at an elevated temperature for
immediate discharge onto the windshield 12 when activated by the
on/off switch 24. This minimizes electrical power requirements on
the vehicle battery 26.
[0072] Although the controller 28 can provide separate switchable
signals to each of the heater elements 100, 102 and 103, in order
to control each heater element 100, 102 and 103 separately under
program or logic control, one alternate approach includes a
bi-metal element or a switch mounted between the power connections
to one terminal 108 and each of the other terminals 108 connected
to the additional heater elements 102 and 103. The bi-metal element
can be set to open at a predetermined temperature, such as
50.degree. C., thereby deactivating the associated heater element.
This enables the additional heater elements 102 and 103, for
example, to remain deactivated until a high heat requirement is
initiated.
[0073] Although the following description of the use of high
amperage switching devices known as MOSFETs, are used as part of
the controller 28 and to provide the necessary high current,
typically 50 amps at 12 volts, to the heating elements 100, 102 and
103 in the thermal mass 40, other high amperage switching devices
may also be employed. Any number of MOSFETs 156 can be mounted in
any configuration on the printed circuit board 150.
[0074] A plurality of bores 158 are optionally formed through the
printed circuit board 150. The bores 158 improve heat flow between
the switching devices on the printed circuit board (PCB) 150 and
the underlying first plate 73.
[0075] A temperature sensor 159, such as a PTC, is mounted on the
printed circuit board 150, typically over or adjacent to the bores
158. The temperature sensor 159 measures the temperature of the
printed circuit board 150 and provides a temperature proportional
signal to the controller 28 which is used by the controller 28 to
control the on/off cycle of the heater elements 100, 102 and
103.
[0076] To further enhance transfer of the heat generated by the
MOSFETs 156 to the first plate 140, a highly conductive pad or
plate 161, hereafter referred to as a sill pad 161, is interposed
in contact between the printed circuit board 150 and the first
plate 23 as shown in FIGS. 3, 8 and 9. The sill pad 161 typically
has a planar shape and dimensions to extend over at least a portion
of the first plate 73. The pad 161 isolates stray electrical
currents to negative ground through the screws 75, provides a
positive contact between the MOSFETs and the thermal mass 40, and
stabilizes heat loss through the adjacent cover by maintaining the
temperature of the plate 73 at a higher temperature to thereby
create a lower temperature differential or gradient with respect to
the thermal mass 40.
[0077] The sill pad 161 preferably has a higher thermal
conductivity than the thermal conductivity of the plate 73 to
efficiently draw heat generated by the MOSFETs 156 to the plate 73
thereby maintaining the temperature of the plate 73 at an elevated
temperature. This elevated temperature of the plate 73 is higher
than the normal temperature of the plate 73 caused by heat escaping
from the sides of the thermal mass 40 around the seals 71 and
72.
[0078] It is known that during sub-freezing temperatures, wash
fluids which are formed substantially of water are subject to
freezing. The expansion of the frozen or semi-frozen fluid causes
pressure to be exerted against the surrounding components of the
heater module 10 which could lead to leaks or to the complete
destruction of the heater module 10.
[0079] As shown in FIGS. 3, 5 and 11-14, a fluid expansion means
160 is carried in the heater module 10 for reversibly allowing
expansion of the fluid in the fluid flow path when the fluid
changes phase from a liquid to a substantially solid state. The
fluid expansion means, in one aspect of the present invention, is
in the form of a thin compressive member such as a generally planar
member, formed of a closed cell foam.
[0080] One example of a suitable material which could be used to
form the fluid expansion means is a closed cell polyolefin foam
sold by Voltek, division of Sekisui America Corp., as product
number VOLARA type LM. Another possible material is a polyvinyl
chloride allied foam, trade name C/3002 or C-2301 from Specialty
Composites Division Cabot Safety Corp., Indianapolis, Ind.
46254.
[0081] The fluid expansion means 160 has sufficient rigidity under
normal fluid operating pressures in the mass 40 to resist
compression. The fluid expansion means or member 160 is disposed
over an inner edge of each of the seals 71 and 72 on both sides of
the thermal mass 30 and has a substantial center portion facing and
exposed to the fluid through the open ends of the channels in the
thermal mass 40. The fluid expansion member 160 has sufficient
rigidity to resist expansion or compression under the normal
operating pressures of the fluid in the heater module 10. However,
at the substantially higher forces exerted by freezing and
expansion of the fluid in the channels, the member 160 is capable
of compression as shown in phantom in FIGS. 12 and 13 to allow
space for the expanded frozen or semi-frozen fluid.
[0082] The fluid expansion member 160 has shape memory so as to
return to its normally generally planar shape, completely filling
an internal cavity 162 formed in an enlarged bulge in each cover 71
and 73.
[0083] The fluid expansion member 160 is compressed by the
fastening on the plate 73 and 74 to the mass to expand slightly
into the channels in the mass 40 and into substantial contact with
the surfaces of the thermal mass 40 to close off the open ends of
each of the channels in the fluid flow path through the thermal
mass 40.
[0084] As shown in FIG. 14, the fluid expansion member 160 has
additional features to facilitate its use in the heater module 10.
A pair of open ended recesses 164 and 166 are formed along one edge
of the fluid expansion member 160. The recesses 164 and 166 overlay
a portion of the underlying fluid flow channel of the thermal
conductive mass 40 to permit a small amount of the fluid in the
fluid flow channel to flow through the recesses 164 and 166 against
the inside surface of the plate 73 or 74. The high power consuming
electronic switching devices, such as the MOSFETs 156, are located
immediately opposite an enlargement in the plate 73. The switching
devices 156 are cooled by the flow of water so as to maintain the
switching devices 156 at a nominal operating temperature.
Additional apertures 168 and 170 are formed in an intermediate
portion of the thermal expansion member 160 for a similar purpose
to allow fluid flow through the channels in the thermal conductive
mass to flow against an inner surface of the adjacent plate 73 to
remove heat from the switching devices 156 located immediately
there over on the circuit board 150.
[0085] An additional open-ended recess 172 is formed on another
edge portion of the thermal expansion member 160. The recess 172
underlies the position of the thermal temperature sensor 159
mounted on the circuit board 150. Fluid flow through the recess 172
provides a more accurate temperature measurement by the temperature
sensor 159 since it is closer to the fluid flowing through the
channels in the thermal mass 40.
[0086] In another aspect of the fluid expansion means 200 shown in
FIG. 16, the fluid expansion means 200 is configured to eliminate
the seal 71 and 72. The peripheral edge portion 202 of the fluid
expansion means or element is compressed when the corresponding
plate 73 or 74 is securely fixed to the thermal mass 40 by means of
the fasteners 75. Alternately, the peripheral edge portion 202 of
the fluid expansion means 200 can be heat and pressure compressed
to a smaller thickness than the central portion of the fluid
expansion element 200.
[0087] In an optional modification shown in FIG. 15, the fluid
expansion means 180 is formed by the seal members 182 and 184
having a solid shape over their entire surface area. At least one
of the thus formed seal members 182 and 184 is formed with
sufficient rigidity to resist expansion when exposed to the normal
pressures of fluid flowing through the open ended channels in the
thermal mass 40. However, any of the seal members 182 and 184 are
capable of expansion into an interior cavity or chamber 186 formed
in the enlarged portion of the plate 73 between the seal 182 and
the inner surface of the plate 73 to accommodate the expanded
frozen or semi-frozen fluid from the mass 40. When the fluid
subsequently changes phase back to a liquid state, the seal members
182 and 184 will assume their original shape wherein each of the
seal members 182 and 184 is disposed in contact with the open ends
of the channels closing off the open end of the channels in the
fluid flow path to maintain the desired labyrinthian flow of fluid
through the thermal mass 40 as described above.
* * * * *