Abstract:
A fluid heater apparatus supplies heat to wash fluid via a continuous, labyrinthian flow path in a thermally conductive body. A heat source is disposed in the thermally conductive body for imparting heat to the body. Fluid flowing through the thermally conductive body substantially envelopes the heat source to absorb heat from the body.

Description:
BACKGROUND 
   This invention relates, in general, to fluid heater apparatus and, more particularly, to fluid heater apparatus which provide a heated wash fluid to a cleanable surface, and, still more specifically, to a heated wash fluid for a vehicle windshield wash system. 
   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. 
   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. 
   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. 
   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 source in the heat exchange body to elevate its temperature prior to dispersion through the spray nozzle onto a vehicle window. 
   However, such prior wash fluid heating devices are inefficient in terms of heat transfer capability as well as being able to only provide a small quantity or a short duration of heated wash fluid onto a vehicle window. Further, direct contact of the fluid with the heat source causes hot spots in the fluid and lower temperature fluid portions which do not contact the heat source. 
   Thus, it would be desirable to provide a fluid heater apparatus which provides a heated fluid in an efficient manner, which has a minimal power requirements, and, which is capable of providing near instantaneous heated wash fluid and larger quantities of heated wash fluid for a longer spray application of the heated fluid onto a cleanable surface than previously devised wash fluid heater devices. 
   SUMMARY 
   The present invention is a heater apparatus for elevating the temperature of a fluid. 
   In one aspect, the heater apparatus includes a thermally conductive mass, heating means thermally coupled to the thermally conductive mass for imparting heat to the thermally conductive mass, and a continuous labyrinthian fluid flow path formed in the thermally conductive mass between an inlet and an outlet. The fluid flow path substantially envelopes the heating means to absorb heat from the thermally conductive mass as fluid flows through the fluid flow path between the inlet and the outlet. 
   In another aspect, the present invention is a wash apparatus including a fluid reservoir adapted for containing a wash fluid, a pump coupled to the fluid reservoir for pumping fluid from the reservoir, a spray nozzle fluidically coupled to the pump for discharging fluid pumped from the reservoir onto a cleanable surface, and the heater apparatus disposed in fluid flow communication between the pump, the reservoir and the nozzle. 
   The apparatus also includes a controller for supplying power to the heater elements of the heater apparatus. 
   The present heater apparatus is also usable in non-vehicle and non-cleaning fluid applications. For example, the present heater apparatus can be easily adapted for use in providing elevated, high temperature fluids for home, office and camper use as well as for industrial processes. 
   The fluid heater apparatus of the present invention affords a highly efficient heater apparatus which quickly and efficiently raises the temperature of a fluid. The heater apparatus is constructed to enable quick elevation of the temperature of a fluid to a desired discharge temperature and to a supply of greater quantities of heated, elevated temperature fluid at or substantially near the desired discharge temperature. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
     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: 
       FIG. 1  is a block system diagram of a fluid heater apparatus according to the present invention used in an exemplary vehicle window wash fluid delivery system; 
       FIG. 2  is a perspective view of a heater module according to one aspect of the present invention; 
       FIG. 3  is an exploded perspective view of the heater module shown in  FIG. 2 ; 
       FIG. 4  is a partially broken away, perspective view of the heater module shown in  FIG. 2 ; 
       FIG. 5  is a top perspective view of the heater module thermal mass; 
       FIG. 6  is a bottom elevational view of the heater module thermal mass shown in  FIG. 5 ; 
       FIG. 7  is a perspective view of the interior of the heater module thermal mass shown in  FIGS. 5 and 6 ; 
       FIG. 8  is a side, cross sectional view of the heater module thermal mass shown in  FIGS. 2-7 ; 
       FIG. 9  is an exploded, perspective view of the connector housing and terminals employed in the heater module shown in the previous drawing figures; 
       FIG. 10  is a perspective view of the assembled connector housing and terminals shown in  FIG. 9 ; 
       FIG. 11  is a perspective view of an alternate aspect of the heater module according to the present invention; 
       FIG. 12  is a partially broken, perspective view of the heater module shown in  FIG. 11 , depicting an alternate heater element; 
       FIG. 13  is a perspective view of thick film heater elements usable in another aspect of the heater module according to the present invention; 
       FIG. 14  is a perspective view of the heater module according to the present invention using the thick film heater elements shown in  FIG. 13 ; 
       FIG. 15  is a partially broken away, perspective view of another aspect of a heater module according to the present invention; and 
       FIG. 16  is an exploded, perspective view of the heater module shown in FIG.  15 . 
   

   DETAILED DESCRIPTION 
   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. 
   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 . 
   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 . 
   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 . 
   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 160° F.-170° F., 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 an “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. 
   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. 
   Referring now to  FIGS. 2-10 , there is depicted one aspect of the heater module  10  according to the present invention. 
   The heater module  10  includes a heat exchange mass or body  40  formed of a suitable high thermally conductive material. Although the mass  40  is described as being formed of diecast, molded or machined aluminum, other materials, either homogenous or non-homogenous, may also be employed. For example, the mass  40  can be formed of alumina particles, ceramic materials, etc. 
   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, receive a fitting  46  and an outer sleeve  48  which are joined together 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 . 
   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 . 
   The heat exchange body  40  is disposed within an insulated housing formed by a first housing part  50  and a mating second housing part  52 . The first and second housing parts  50  and  52  have complementary shapes with a major wall surface  54  and  56 , respectively, and a surrounding peripheral lip  60  and  62 , respectively. 
   A necked-down end portion  64  and  66  is formed in each first and second housing part  50  and  52 , and forms an extension from one end of the respective major walls  54  and  56  as well as from the peripheral edge lips  60  and  62 . The necked-down portions  64  and  66 , when joined together, form an end cavity for receiving a connector assembly  70  which connects electrical conductors to the heating element(s) mounted in the joined first and second housing parts  50  and  52 . 
   Seal members  74  and  75 , formed of a resilient and thermally insulating material, are interposed between the opposed major surfaces of the heat exchange body  40  and the inner surfaces of the major walls  54  and  56  of the first and second housing parts  50  and  52 , respectively. The seals  74  and  75  seal the open ends of the fluid flow channels or paths, described hereafter, in the opposed major surfaces of the heat exchange body  40 . 
   The first and second housing parts  50  and  52  and the heat exchange body  40  are fixedly joined together, after the connector assembly  70  has been disposed in the extension  64  and  66  of the first and second housing parts  50  and  52  by suitable means, such as by heat stake rivets or projections  76  projecting outwardly from opposite major surfaces of the heat exchange body  40 . The projections  76  engage apertures  77  in the major wail surfaces  54  and  56  of the first and second housing parts  50  and  52  and are heat welded together to join the first and second housing parts  50  and  52  together in a fixed connection; while maintaining the seal elements  74  and  76  in tight contact with the open ends of the fluid flow paths in the heat exchange body  40 . 
   As shown in detail in  FIGS. 4-7 , the heat exchange mass or body  40  has a solid cubical shape formed of a first major surface  80 , a second opposed major surface  82 , and four sidewalls  84 ,  86 ,  88  and  90 , interconnecting the first and second surfaces  80  and  82 . 
   A plurality of bores  92 ,  94 ,  96  and  98  are formed in the body  40  and project inwardly from the sidewall  84 . The bores  92 ,  94 ,  96  and  98  are each adapted for receiving one generally cylindrical heater element. As partially shown in  FIG. 4 , each bore, such as bores  96  and  98 , extend through the solid central portion of the body  40  so as to be completely surrounded by the solid material of the body  40 . This defines the body  40  as a heat source after receiving heat from activation of the heater elements describe hereafter. 
   In the aspect of the invention shown in  FIGS. 4-7 , the heater elements are formed of CALROD. Although different materials many be used, one example of a CALROD construction is a Nichrome wire inside of a stainless steel sheath. 
   By way of example only, at least one and preferably a plurality, i.e., two or three or more individual heater elements  100 ,  102  and  103 , with only heater elements  100 ,  102  being shown in  FIG. 4 , are disposed in the bores  96 ,  94  and  98 . The function of the one or more heater elements, such as heater elements  100  and  102 , will be described hereafter in conjunction with the description of the heater module  10 . 
   As seen in  FIGS. 4 and 7 , one end  104 ,  106  and  107  of each heater element, elements  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, engage individual terminals  108  formed at one end of a grid assembly  110  shown in detail in FIG.  9 . The grid assembly  110  is initially formed as a single element wherein individual terminals  112  are unitarily joined together by interconnecting tabs  114 . The tabs  114  are later separated from the terminals  112  to provide a separate contact for each heater element  100 ,  102  and  103 . One terminal  112  is connected to a ground rod. The grid assembly  100  is mounted in a connector housing  116  having a generally cylindrical shape with a hollow interior. One end of the terminals  112  is connected to a circuit board  113  shown in FIG.  3 . The circuit board  113  is fixedly mounted by suitable locating pins in the cavity formed by the extensions  64  and  66  of the first and second housing parts  50  and  52 . One of the terminals  112  acts as a ground lead in that an end portion is disposed in contact with the outer stainless steel sheath of each heater element or CALROD  100 ,  102  and  103 . Another of the terminals  112  is the power lead for CALROD  100 . This terminal  112  provides electric power to the CALROD  100  through contact with the end  104  of heater element  100  in the grid assembly  110 . 
   The other two terminals  112  provide power connections to the other two heater elements  102  and  103 . A switch, not shown, may be interposed between the terminal  112  and the other two terminals  112  to selectively provide power to the other two terminals  112  when power is supplied to the power terminal. This switch can be a bi-metal switch, for example, which will open at a predetermined temperature, such as 50° C., as described hereafter. Alternately, a switch controlled by the circuitry on the circuit board  113  of the controller  28  will selectively connect power from the power terminal  112  to the other terminals  112 . This provides the controller  28  with the capability, when receiving suitable external input signals from the vehicle body controller, for example, to deactivate the heater module  10  during the occurrence of low vehicle battery power, a thermal event, etc. 
   As shown in  FIG. 10 , another set of terminals  112 , mounted in the connector housing  116 , are connected internally to the circuit board  113  to provide the power, ground and external signals to the circuit board  113  as described above. 
   The connector housing  116  includes a pair of spaced walls  118  and  120  formed along one side edge and an intermediate latch projection  122 . The walls  118  and  120  and the latch projection  122  mate with complementary recesses and a latch receiver, not shown, in a complementary connection engagable with the connector housing  116 . The mating connector will include sockets which receive the terminals  115 . 
   As shown in  FIGS. 4-7 , the thermally conductive mass or body  40  includes a fluid flow channel or path which extends from the inlet  42  to the outlet  44 . The fluid flow path has 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 alternatingly 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 . 
   As shown in  FIG. 6 , 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 . As described above, the seal members  74  and  75  sealingly close the open ends of the first and second fluid flow channels  130  and  132 . 
   Thus, fluid flow through the first and second flow channels  130  and  132  starts from the inlet  42  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 . 
   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 . 
   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 . 
   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° F.-170° F. at the outlet  44  in approximately sixty seconds. 
   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 should occur when the fluid comes into direct contact with 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. 
   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 160° F.-170° F. 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 . 
   At the completion of the fluid dispensing operation, and during other periods of non-fluid dispensing while the vehicle ignition is still “on”, 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 . 
   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 simple approach includes the bi-metal element or a switch mounted between the power connections to one terminal  112  and each of the other terminals  112  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° 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. 
   Alternate heater element constructions are also possible in the heater module  10  of the present invention. As shown in  FIG. 11 and 12 , a single heater element  140  may be provided in a complementary shaped cavity in the heat exchange body  141 . The single heat exchange element  140  can have a irregular shape formed of alternating, angularly disposed straight sections interconnected by arcuate corners. The single heater element  140  forms a single loop through the heat exchange body  140  from a first end  142  to a second end  144 . In this aspect, the body  140  would be formed of two mating halves which are tightly joined together about the heater element  140 . The same terminals  112  in the connector housing  70  may be employed to connect the single heater element  140  to the vehicle battery  26  or the controller  28 . 
   Although slightly less electric energy efficient as the multiple CALROD beater elements  100 ,  102  and  103  described above and shown in  FIGS. 4-7 , the single irregularly shaped CALROD heater element  140  still is capable of suppling sufficient heat to the heat exchange body  141  to raise and maintain the temperature of fluid in the fluid flow channels  130  and  132  at an elevated temperature for discharge of the fluid from the body  141  at the desired discharge temperature. 
   Different heater elements  152  and  154  may also be employed in the body  40 . As shown in  FIGS. 13 and 14 , the heater elements  152  and  154  comprise thick film circuit elements having circuit connections or leads  156  and  158  at opposed ends. The thick film heater elements  152  add  154  are inserted in oppositely facing directions, (the side-by-side arrangement of the heater elements  152  and  154  is depicted only for reasons of clarity) in suitably formed bores in the body  40 , with the leads  156  and  158  projecting through the sidewall  84  for connection to a suitable shaped terminal assembly in the connector housing  70 , not shown. 
   The thick film heater elements  152  and  154  are operated by the controller  28  either simultaneously for maximum power input to the heat exchange body  40 , with possibly only one of the heater elements  152  and  154  being operated during periods of non-fluid discharge to maintain the temperature of the fluid in the heat exchange body  40  at an elevated temperature with minimum electrical power drain on the vehicle battery  26 . 
   Referring now to  FIGS. 15 and 16 , there is depicted another aspect of a heater module  210 . The heater module  210  is substantially the same as the heater module  10  described above and shown in  FIGS. 1-10 . However, for clarity, like elements in the two different aspects of the heater modules  10  and  210  are distinguished in the heater module  210  by a “ 200 ” reference number prefix, but the same tens and units. Only the major differences between the heater module  210  and the heater module  10  will be discussed will be discussed in detail. 
   The heater module  210  as shown in  FIGS. 15 and 16  includes first and second housing parts  250  and  252 . Extensions  264  and  266  are disposed with an elongated or longer dimension extending perpendicular to the direction of the heater elements inserted into a thermal mass  240 . 
   Projections or stakes  276  on opposite major surfaces of the mass  240  extend through apertures  277  in seals or gaskets  275  and corresponding apertures in the housing parts  250  and  260 . Outer ends of the stakes  276  are riveted or heat welded to securely join the housing parts  250  and  252  about the thermal mass  240 . For added strength, ribs  279  extend from each side edge of the thermal mass  240 . The ribs  279  extend through notches  281  in the gaskets  275  and through slotted bosses  283  in each housing part  250  and  252 . The outer ends of the ribs  279 , after passing through the bosses  283 , are bent over or otherwise securely mechanically joined to the outer surface of the housing parts  250  and  252 . 
   As shown in  FIGS. 15 and 16  as well as in  FIG. 3  for the heater module  10 , a plurality of ribs  285  are formed on the outer surface of each housing part  250  and  252 . The ribs  285 , which are depicted only in an exemplary configuration, provide structural strength to the housing parts  250  and  252  which are typically formed of plastic. 
   In this aspect of the heater module  210 , heater elements or CALRODS  300 ,  302  and  304  are mounted in bores  301  formed in the mass  240 . The bores  301  extend generally parallel to two opposed side surfaces of the mass  240 . 
   Other than the above described differences, the heater module  210  functions in the same manner as the heater module  10  described above. 
   In summary, there has been disclosed a unique fluid heater apparatus which efficiently heats fluid to a desired discharge temperature with minimum power requirements and a quick temperature rise time.