PPTC actuator heater

Abstract

A novel heater for a temperature-sensitive actuator is disclosed. The heater is a polymer positive temperature coefficient (PPTC) device composed of a conductive filler and a semi-crystalline polymer. The PPTC heater is strategically designed to have a predetermined self-regulating temperature and is suitable for any application that utilizes the heater. Physical characteristics of the PPTC heater such as gap width and thickness enable the current flowing through the heater to be strategically controlled.

Description

Technical Field

[0001] Embodiments of the present disclosure relate to PPTC devices, and more particularly to PPTC devices operating as heaters. Background Art

[0002] Positive temperature coefficient (PTC) and polymer PTC (PPTC) devices are utilized in circuits to interrupt overcurrent and overvoltage situations that may damage expensive circuitry within an electronic system. PTCs include materials that change their physical properties upon heating. As current flow increases, the PTC increases in resistance as the temperature rises. Once the fault condition is removed, the PTC device cools to its original configuration. Thus, PTCs and PPTCs are considered resettable fuses.

[0003] Recently, PTC technology has been used in heater applications. However, PTC devices have somewhat awkward dimensions and shapes for some applications, such that they must have a much higher power density than is effective for heating applications.

[0004] It is with respect to these and other considerations that improvements of the present invention may be useful. Summary of the Invention

[0005] The present Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. The present Summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to assist in determining the scope of the claimed subject matter.

[0006] An exemplary embodiment of a polymer positive temperature coefficient (PPTC) heater according to the present disclosure may include: a first electrode connected to a first wire, a heater body composed of a PPTC polymer matrix, wherein the PPTC polymer matrix includes both a conductive filler and a semi-crystalline polymer. The PPTC heater further includes a second electrode connected to a second wire, wherein the PPTC polymer matrix is disposed between the first electrode and the second electrode to form a sandwich. A bending process is employed to shape the sandwich into an annular shape.

[0007] Another exemplary embodiment of the PPTC heater according to the present disclosure may include: a heater body including a conductive filler and a semi-crystalline polymer, the heater body being configured as a rectangular sheet having a predetermined thickness; a first electrode located above a side surface of the heater body at a first end, the first electrode being connected to a first wire; a second electrode located above the same side surface of the heater body at a second end, the second electrode being connected to a second wire. There is a gap between the first electrode and the second electrode, and the gap is horizontal with respect to the first wire and the second wire. The gap has a second predetermined thickness, and the heater body between the first electrode and the second electrode is exposed by the gap. The PPTC heater is formed in an annular shape such that both the first electrode and the second electrode are on the inner surface.

[0008] Another exemplary embodiment of the PPTC heater according to the present disclosure may include: a heater body including a polymer matrix, the heater body being configured as a rectangular sheet having a predetermined thickness; a first electrode located above a side surface of the heater body at a first end, the first electrode being connected to a first wire; a second electrode located above the same side surface of the heater body at a second end, the second electrode being connected to a second wire. There is a gap between the first electrode and the second electrode, and the gap is vertical with respect to the first wire and the second wire. The gap has a second predetermined thickness, and the heater body between the first electrode and the second electrode is exposed by the gap. The PPTC heater is formed in an annular shape such that both the first electrode and the second electrode are on the inner surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1A - 1C is a diagram of a PPTC heater according to an exemplary embodiment;

[0010] Figure 2A - 2C is a diagram of a PPTC heater according to an exemplary embodiment;

[0011] Figure 3A - 3C is a diagram showing the properties of the PPTC heaters of FIGS. 1 and 2 according to an exemplary embodiment;

[0012] Figure 4A - 4B are a diagram and an equivalent circuit of a PPTC heater according to an exemplary embodiment, respectively;

[0013] Figure 5 is a diagram of a PPTC heater according to an exemplary embodiment;

[0014] Figure 6A - 6D is a diagram showing a PPTC heater including an equivalent circuit according to an exemplary embodiment;

[0015] Figure 7A - 7DA diagram of an actuator activated by a PPTC heater according to an exemplary embodiment;

[0016] Figure 8 A diagram of a heater body for any of the disclosed PPTC heaters according to an exemplary embodiment;

[0017] Figure 9A - 9C A test circuit and two graphs related to a test PPTC heater according to an exemplary embodiment;

[0018] Figure 10A - 10C A test circuit and two graphs related to a test PPTC heater according to an exemplary embodiment;

[0019] Figure 11A and Figure 11B An illustration of the effect of bending a PPTC heater according to an exemplary embodiment; and

[0020] Figure 12 A flowchart for manufacturing a PPTC heater according to an exemplary embodiment. Detailed Description

[0021] According to the embodiments described herein, a novel heater is disclosed for use in temperature-sensitive actuators such as for waste heat recovery systems. The heater is a polymer positive temperature coefficient (PPTC) device composed of a conductive filler and a semi-crystalline polymer. As an example, the conductive filler can be a carbon / graphene combination, but the PPTC heater can be made of a variety of conductive fillers. The PPTC heater is strategically designed to have a predetermined self-regulating temperature and is suitable for any application that utilizes the heater. The physical characteristics of the PPTC heater (such as gap width and thickness) enable the flow of current to be strategically controlled.

[0022] Figure 1A - 1C A representative diagram and illustration of a novel PPTC heater 100 or a PPTC actuator heater 100 for operating an actuator according to an exemplary embodiment; Figure 1A and Figure 1B respectively depict a side plan view and a top cross-sectional view of the PPTC heater 100. The PPTC heater 100 includes a heater body 104 made of a PTC material. The heater body 104 is generally planar in shape and has two opposite surfaces. In an exemplary embodiment, the thickness of the heater body 104 is less than 1 mm. The heater body will be further described and illustrated in the following Figure 8 below.

[0023] The PPTC heater 100 includes a first electrode 106 and a second electrode 102, both of which are disposed on a first opposing surface of the heater body 104. Electrodes 102 / 106 are conductive layers separated by a gap 116 in which no conductive layer exists, and the heater body 104 is exposed at the gap. In Figure 1A a side plan view, the gap 116 is horizontally disposed, with the first electrode 106 below the gap 116 and the second electrode 102 above the gap. A first lead (wire) 108 is connected to the first electrode 106, while a second lead 110 is connected to the second electrode 102.

[0024] Figure 1B Further shown is a third electrode 118 disposed on a second opposing surface of the heater body 104, the second surface being opposite to the first surface on which the first electrode 106 and the second electrode 102 are disposed. The third electrode 118 is not visible in Figure 1A . The heater body 104 has a thickness 120. Thus, the heater body 104 is sandwiched between the electrodes 102 / 106 on one side and the electrode 118 on the other side, where the gap 116 exposes the heater body between the electrodes 102 and 106.

[0025] Figure 1C is an illustration of a PPTC heater 100 according to an exemplary embodiment. The PPTC heater 100 is in an annular (ring) shape and is adapted to be placed around a cylindrical device to be heated. In the exemplary embodiment, the device to be heated is an actuator. An actuator is a device that moves or operates something. An actuator converts an energy source (electrical, hydraulic, or pneumatic) into physical mechanical motion. An actuator can move in a linear or circular (rotational) direction. In the exemplary embodiment, heating of the actuator by the PPTC heater 100 activates the actuator to move in a linear or rotational direction.

[0026] In Figure 1C the illustration, the electrodes 102 and 106 are disposed on the inner surface of the annular shape of the PPTC heater 100, while the electrode 118 is disposed on the outer surface. The PPTC material of the heater body 104 is shown both between the electrodes 102 and 106 (as a horizontally disposed opening) and along the upper edge of the ring. The wires 108 and 110 are respectively disposed on the inner electrodes 102 and 106.

[0027] In an exemplary embodiment, the annular shape of the PPTC heater 100 is wrapped around the thermo - element of a cylindrical actuator. Thus, the PPTC heater 100 is in contact with the actuator's thermo - element, enabling the actuator to be rapidly heated and activated to move. In this way, the PPTC actuator heater 100 provides an advantage in the application of a waste heat recovery system, in which a piston is activated by the actuator to linearly move (advance and retract). Additionally, the annular shape of the PPTC heater 100 is a temperature - limiting feature, as the heater confines the distribution of heat to an exact location (the thermo - element of the actuator). Thus, the PPTC heater ensures a stable output of the linear motion of the piston by restricting the heating of the thermo - element.

[0028] In an exemplary embodiment, the PPTC actuator heater 100 is thin (less than 1 mm in thickness) and small (less than 1 cm in diameter). In some embodiments, this small size enables the PPTC actuator heater 100 to be in direct contact with the actuator's thermo - element, which results in high thermal efficiency. Thus, the cylindrical PPTC heater 100 can be installed in the heating target area of the actuator.

[0029] In addition to reducing heat loss, in an exemplary embodiment, the design of the PPTC heater 100 is simpler than some conventional PPTC devices, which can save manufacturing costs. Currently available conventional PPTC or ceramic PTC (cPTC) devices are generally flat rectangular or circular and have a thickness exceeding 1 mm. In applications involving limited space and / or electrical insulation requirements, these PTC heating elements cannot be located close to the target. The resulting arrangement of conventional PTC devices leads to slow heating of the target surface and high heat loss. In one example, the use of a conventional PTC device for heating a target surface causes the surface temperature of the PTC device to reach approximately 200 °C, but the target surface only reaches 100 °C, with rather low efficiency.

[0030] There are some thin - film PPTC devices with a thickness less than 1 mm, but the power density for these devices is very low. Thus, such thin - film PPTC devices need to be large enough to generate sufficient heat in a short time. In one embodiment, the PPTC heater 100 has a much higher power density than existing thin - film PPTC devices.

[0031] Figure 2A - 2C is a representative diagram associated with a PPTC heater for operating an actuator according to an exemplary embodiment; Figure 2A and Figure 2BSide plan view and top cross-sectional view of a PPTC heater 200 according to an exemplary embodiment are depicted respectively. The PPTC heater 200 includes a heater body 204 made of a PTC material. The heater body 104 is substantially planar in shape and has two opposite surfaces. In an exemplary embodiment, the thickness of the heater body 204 is less than 1 mm. The heater body will be further described and illustrated in Figure 8 below.

[0032] The PPTC heater 200 includes a first electrode 206 and a second electrode 202, both of which are disposed on the first opposite surface of the heater body 204. These electrodes 202 / 206 are conductive layers separated by a gap 216 in which there is no conductive layer and the heater body 204 is exposed at the gap. In Figure 2A the side plan view, the gap 216 is disposed vertically with the first electrode 206 on the left side of the gap and the second electrode 202 on the right side of the gap. A first lead (wire) 208 is connected to the first electrode 206 while a second lead 210 is connected to the second electrode 202.

[0033] Figure 2B Further shown is a third electrode 218 disposed on the second opposite surface of the heater body 204, the second surface being opposite to the first surface on which the first electrode 206 and the second electrode 202 are disposed, where the third electrode 218 is not visible in Figure 2A the figure. The heater body 204 has a thickness 220. Thus, the heater body 204 is sandwiched between the electrodes 202 / 206 on one side and the electrode 218 on the other side, with the gap 216 exposing the heater body between the electrodes 202 and 206.

[0034] Figure 2C is an illustration of a PPTC heater 200 according to an exemplary embodiment. The PPTC heater 200 is in an annular (ring) shape and is adapted to be placed around a cylindrical device to be heated. In an exemplary embodiment, the device to be heated is an actuator. In an exemplary embodiment, heating of the actuator by the PPTC heater 200 activates the actuator to move in a linear or rotational direction.

[0035] In Figure 2CIn the illustration, electrodes 202 and 206 are disposed on the inner surface of the annular shape of the PPTC heater 200, while electrode 218 is disposed on the outer surface. The PPTC material of the heater body 204 is shown both between electrodes 202 and 206 (as a vertically disposed opening) and along the upper edge of the circular ring. Conductors 208 and 210 are respectively disposed on the inner electrodes 206 and 202. The PPTC heaters 100 and 200 exhibit the same overall power design, N = 1 (where N represents the total number of slots on both sides of the heater electrodes).

[0036] Figure 3A - 3C is a representative diagram showing the properties of the PPTC heaters 100 and 200 according to an exemplary embodiment. Figure 3A presents the equivalent circuits of the PPTC heaters 100 ( Figure 1A - 1C ) and 200 ( Figure 2A - 2C ). R0 and R7 respectively represent the resistances of the conductors 108 / 208 and 110 / 210 (and vice versa), R1 and R6 respectively represent the resistances of the electrodes 102 / 202 and 106 / 206 (and vice versa), R3 represents the resistance of the electrodes 118 / 218, and R2, R4, and R5 represent the heater bodies 104 / 204 (PTC material). In the exemplary embodiment, the resistance R4 is significantly greater than the resistance R2 or R5.

[0037] Although there is a single heater body 104 / 204 made of PTC material, the flow of current through the heaters 100 / 200 can take three possible paths through the PTC material of the heater body 104 / 204, as given by R2, R4, and R5. Figure 3B shows three possible current paths through the heater body that can occur in both the cases of the PPTC heaters 100 and 200 according to an exemplary embodiment. Arrows 302, 304, and 306 show the directions of the current flow through the PPTC material. Figure 3A shows that there are two possible paths for current flow. The first current path passes through R0, R1, R2, R3, R5, R6, and R7. Arrows 302 and 304 are thus sub-paths of the first current path. The second current path passes through R0, R1, R4, R6, and R7. Arrow 306 is thus part of the second current path.

[0038] At resistor R2 (represented by arrow 302), current flows through the PPTC material between electrode 106 / 206 (R1) and electrode 118 / 218 (R3). At resistor R5 (represented by arrow 304), current flows through the PPTC material between electrode 118 / 218 (R3) and electrode 102 / 202 (R6). At resistor R4 (represented by arrow 306), current flows through the PPTC material between electrode 106 / 206 (R1) and electrode 102 / 202 (R6). Because resistor R4 is significantly greater than resistor R2 or R5, in the exemplary embodiment, the third current flow direction (R4) is less likely to occur than the other current flow directions given by resistor R2 or R5.

[0039] Figure 3C FIG. is a representative view of a PPTC heater 100 or 200 in an annular shape according to an exemplary embodiment. Figure 3C For showing possible current flow directions through the annular PPTC heaters 100 and 200. The annular ring is formed by a heater body 104 / 204 at the center, wherein a third electrode 118 / 218 surrounds the outer surface of the ring, and a first electrode 106 / 206 and a second electrode 102 / 202 are disposed on the inner surface of the ring. For the PPTC heater 100, the second electrode 102 is disposed above the first electrode 106 on the inner surface of the ring (see also Figure 1A and Figure 1C ). For the PPTC heater 200, the first electrode 206 is disposed on one side of the inner surface of the ring, while the second electrode 202 is disposed on the other side of the inner surface of the ring (see also Figure 2A and Figure 2C ).

[0040] As Figure 3B shown, the arrows show the possible directions of current flow. Starting from the lead 108 / 208 (represented by arrow 308 and resistor R2), current flows from the electrode 106 / 206 through the PPTC material of the heater body 104 / 204 to the electrode 118 / 218 disposed on the opposite side of the heater body. The current flows along the electrode 118 / 218 (represented by arrow 310 and resistor R3). Next, the current flows from the electrode 118 / 218 through the PPTC material of the heater body 104 / 204 to the lead 110 / 210 (represented by arrow 312 and resistor R5). Alternatively, the current can flow between the electrode 106 / 206 and the electrode 102 / 202, as represented by arrows 314 and 316 (and vice versa), and also as represented by resistor R4.

[0041] In various embodiments, the design of the heater body and electrodes of the PPTC heaters 100 and 200 can be such that the value of R4 is much greater than the value of R2 or R5 ( Figure 3A)。This situation can be achieved in the PPTC heater 100 ( Figure 1A and Figure 1B ) and the PPTC heater 200 ( Figure 2A and Figure 2B ) by arranging the thickness 120 / 220 of the heater body 104 to be relatively smaller than the gap 116 / 216. In an exemplary embodiment, the thickness 120 of the heater body 104 ( Figure 1B ) or the thickness 220 of the heater body 204 ( Figure 2B ) ranges between 3 mils and 120 mils in various non - restrictive embodiments, and in some embodiments, between 5 mils and 10 mils, while the value of the gap, whether it is the horizontally - arranged gap 116 ( Figure 1A ) between the electrodes 102 and 106 or the vertically - arranged gap 216 ( Figure 2A ) between the electrodes 202 and 206, is relatively greater than the thickness 116 / 216 of the corresponding heater body 104 / 204. For example, if the thickness 120 of the heater body 104 is 10 mils, the value of the gap 116 or 216 can be 50 mils or greater, thus ensuring that R4 is much greater than R2 or R5.

[0042] In an exemplary embodiment, the resistance of the PPTC heaters 100 and 200 represented by the equivalent circuit ( Figure 3A ) is approximately equal to the value of the initial resistance multiplied by 4 (when R2 = R5 and the heater is in a non - tripped state, R≈4R i ). According to a variant of these embodiments, the design of the slot (gap 116 or gap 216) position can determine the thermal effect (higher on one side; lower on the other side, by controlling the resistance of each PPTC segment) on the top and bottom (PPTC heater 100) or on the left and right (PPTC heater 200). In one embodiment, in the example where the entire heater is to be bent in an annular shape, the PPTC heater 100 has better mechanical strength than the PPTC heater 200.

[0043] Figure 4 is a side plan view of a PPTC heater 400 according to an exemplary embodiment. As shown in the foregoing embodiments, the design of the PPTC heater 400 is also characterized by two electrodes connected to external leads disposed on the same side of the device. Electrode 406 is connected to lead 408, and electrode 402 is connected to lead 410. Electrode 402 is separated from electrode 406 by slot 420 and slot 412, where there is no conductive layer, exposing heater body 404 made of PPTC material. Additionally, a conductive region 422 is provided between slot 412 and slot 420, where there is material such as that of electrodes 402 and 406. Thus, slots 420, 412 define a region along the surface of the PPTC heater 400 that has a relatively high resistance compared to the resistance of the materials of electrodes 402, 406, and conductive region 422. In the side plan view of FIG. 4, slots 412, 420 are arranged to extend perpendicular to the general direction of leads 408 and 410. In addition to electrodes 402, 406, and conductive region 422, the PPTC heater 400 also includes conductive regions 414 and 418, which in each case are disposed on opposite sides of heater body 404 and are separated by slot 416. Since they are on opposite sides of the heater body, slot 416 is shown in a lighter shade.

[0044] Thus, the PPTC heater 400 can be characterized by Figure 4B the equivalent circuit shown, where R0 and R 12 represent the resistance of leads 408, 410, R1, R3, R6, R8, R 11 represent the resistance of the electrodes, R2, R5, R7, and R 10 represents the resistance of heater body 404 to current flowing through the thickness of heater body 404 (i.e., perpendicular to both leads 408, 410 and slots 412, 416, and 420, or in the Z direction), and R4, R9, and R 13Represents the resistance of the heater body 404 to the current flowing along the surface of the heater body 404 (i.e., parallel to the wires 408, 410 but perpendicular to the slots 412, 416 or 420, or in the Y direction). Specifically, during operation below the trip temperature, the current of the PPTC heater 400 can flow between the wire 408 and the wire 410, mainly through the wire 408 (R0), through the electrode 406 (R1), through the thickness of the heater body 404 (R2) (in the Z direction); along the surface of the conductive region 414 (R3) (along the back of the heater body), back through the thickness of the heater body 404 (R5), in the Z direction, to the front of the device; along the surface of the conductive region 422 (R6); through the thickness of the heater body 404 (R7) and flow in the Z direction to the back of the device; along the surface of the conductive region 418 (R8); through the thickness of the heater body 404 (R 10 ) and flow back to the front of the device in the Z direction again; and through the electrode 402 (R 11 ) and the wire 410 (R 12 ). In other words, during operation below the trip temperature, the current does not jump over the slots 412 or 420 on the front of the device in the Y direction, nor does it jump over the slot 416 on the back of the device. Generally, since the dimensions of the slots 416, 412, 420 (gaps) can be much larger than the thickness of the heater body 404, the current typically does not flow along the path in the plane of the heater body (in the Y direction), as represented by the resistances R4, R9, R 13 .

[0045] Figure 5 is a side plan view of a PPTC heater 500 according to an exemplary embodiment. In Figure 5 , the heater configuration is generally the same as that of the PPTC heater 400 ( Figure 4A)The same, except that a pair of slots 520, 512 are arranged to extend generally parallel to the overall direction of wires 508 and 510. Specifically, electrode 502 is connected to wire 508, and electrode 506 is connected to wire 510. Electrode 502 is separated from electrode 506 by slots 512 and 520, where there is no conductive layer, exposing heater body 504. Additionally, a conductive region 522 is provided between slots 512 and 520, where there is a material such as the material of electrodes 502 and 506. Thus, slots 512, 520 define a region along the surface of the PPTC heater 500 that has a relatively high resistance compared to the resistance of the materials of electrodes 502, 506, and conductive region 522. In addition to electrodes 502, 506, and conductive region 522, the PPTC heater 500 also includes conductive regions 514 and 518, both of which are provided on opposite sides of heater body 504 and are separated by slot 516. Since on opposite sides of the heater body, slot 416 is shown in a lighter shade.

[0046] Just as the PPTC heater 400( Figure 4A ) is, the PPTC heater 500 can also be characterized by Figure 4B the equivalent circuit shown, where R0 and R 12 represent the resistance of wires 508, 510, R1, R3, R6, R8, R 11 represent the resistance of the electrodes, R2, R5, R7, and R 10 represent the resistance of heater body 504 to current flowing through the thickness of heater body 504 (i.e., perpendicular to both wires 508, 510 and slots 512, 516, and 520, or in the Z direction), and R4, R9, and R 13 represent the resistance of heater body 504 to current flowing along the surface of heater body 504 (i.e., perpendicular to both wires 508, 510 and slots 512, 516, and 520, or in the X direction). Specifically, during operation below the trip temperature, the current in the PPTC heater 500 can flow between wire 508 and wire 510, mainly through wire 510 (R0), through electrode 502 (R1), through the thickness of heater body 504 (R2), flowing in the Z direction to the back of the device; along the surface of conductive region 514 (R3), through the thickness of heater body 504 (R5), flowing in the Z direction along the surface of conductive region 522 (R6) back to the front of the device; through the thickness of heater body 504 (R7); along the surface of conductive region 518 (R8); through the thickness of heater body 504 (R 10 ), flowing in the Z direction again to the front of the device; through electrode 506 and wire 510 (R 12)。Generally, since the dimensions of the slots 516, 512, 520 (gaps) can be much larger than the thickness of the heater body 504, the current may not flow along a path in the plane of the heater body, as represented by the resistances R4, R9, R 13 as shown.

[0047] In summary, the PPTC heaters 400 and 500 configurations provide the same power design (N = 3). The resistance of a given heater resistance is approximately the initial resistance multiplied by 16 (when R2 = R5 = R7 = R 10 and the heater is in the non-tripped state, R ≈ 16R i ).

[0048] Figure 6A - 6D is a representative diagram associated with the PPTC heater 600 according to an exemplary embodiment. Figure 6A Shows a side planar view of the PPTC heater 600, Figure 6B is an equivalent circuit for the PPTC heater 600, Figure 6C is a photograph of the PPTC heater 600, and Figure 6D shows the PPTC heater 600 in an annular shape, such as can be used with an actuator. In Figure 6A and Figure 6D , the PPTC heater 600 includes a heater body 604 sandwiched between a first electrode 602 ( Figure 6D shown on the outer surface of the annular shape in Figure 6D ) and a second electrode 606 ( Figure 6A shown on the inner surface of the annular shape in Figure 6B ). The first wire 608 is disposed on the front side (outside the annular surface) of the PPTC heater 600, while the second wire 610 is disposed on the back side (inside the annular surface). In this example, the first electrode 602 is connected to the wire 608, and the second electrode 606 is connected to the wire 610. Thus, the current will flow through the thickness of the PPTC heater body in the Z direction. In the equivalent circuit of

[0049] , R0 and R4 represent the resistances of the wires 608, 610, R1 and R3 represent the resistances of the electrodes 602, 606, and R2 represents the resistance of the heater body 604 to the current flowing through the thickness of the heater body.

[0050] Figure 7A - 7D is a side plan view of a PPTC heater 700 according to an exemplary embodiment. The PPTC heater 700 is disposed on an actuator 702. Although shown as rectangular in the Figure 7A - 7D side plan view, the PPTC heater 700 is actually annular, such as in Figure 1C , 2C , 3C, 6C or 6D, and is disposed on top of the actuator 702 or above a heating element 704. In one embodiment, the heating element 704 of the actuator 702 includes a waxy matrix 706, such as paraffin wax mixed with a metallic material, such that when the PPTC heater is disposed thereon, the waxy matrix is between the PPTC heater 700 and the actuator 702. The presence of the waxy matrix 706 is to facilitate control of an on / off valve (not shown) of the actuator 702. Note that according to various embodiments, the PPTC heater 700 is disposed in a thin, annular form to circumferentially surround the heating element 704 (see, for example, Figure 1C ). Thus, the PPTC heater 700 heats and ultimately melts the waxy matrix 706, which then heats the heating element 704 and activates the actuator 702, causing the actuator to then move in a linear or rotational direction. Once the temperature of the PPTC heater 700 cools down, the melted waxy matrix 706 hardens again, thus protecting the actuator.

[0051] Figure 7A shows an overall view of an actuator 702A having a waxy matrix 706; Figure 7B shows an overall view of an extrusion push type actuator 702B having a waxy matrix 706; Figure 7C shows an overall view of a diaphragm type actuator 702C having a waxy matrix 706; Figure 7D shows an overall view of a plunger piston type actuator 702D having a waxy matrix 706 (collectively referred to as “(one or more) actuators 702”). In an exemplary embodiment, the waxy matrix 706 is a key element of the thermal actuator, acting as a waxy matrix when heated such that the actuator is turned on or off. The heated waxy matrix 706 squeezes an elastic bag 708 ( Figure 7B ) or a membrane 712 ( Figure 7C ) of the actuator 702, and moves a piston 710. Alternatively, the heated waxy matrix squeezes and moves the piston 710. In an exemplary embodiment, the PPTC heater 700 is insulated from parylene by chemical vapor deposition (CVD) or other coatings to avoid short circuits, since the heating element of the actuator 702 is generally composed of metal particles in the waxy matrix.

[0052] In an exemplary embodiment, the PPTC heater 700, as well as any other PPTC heaters 100, 200, 400, 500, and 600, are self-regulating heaters, and the self-regulated temperature depends on the specific application. In the exemplary embodiment, the PPTC heater 700 has a self-regulating temperature of approximately 125°C. The self-regulating temperature is thus the upper limit temperature for the PPTC heater. Therefore, although the temperature of the PPTC heater 700 can rise to approximately 125°C, it will not exceed this temperature. If the temperature is higher than 125°C, its heating power will be reduced to prevent overheating of the actuator. Therefore, in the case where the PPTC heater is combined with the actuator, as Figure 7A - 7D shown, the temperature of the PPTC heater rises to approximately 125°C, the associated wax in the actuator completely melts, causing the actuator valve to move, and thereafter the temperature of the PPTC heater will not exceed 125°C.

[0053] Figure 8 is a side plan view of the heater body of the PPTC heater according to an exemplary embodiment. Recall that the PPTC heaters disclosed herein include a heater body made of a PPTC material (see, for example, Figure 1A - 1C the heater body 104 in ), where the PPTC material consists of a polymer matrix composed of 1) conductive fillers (such as carbon and / or graphene) and 2) a semi-crystalline polymer. As Figure 8 shown, the heater body 804 consists of a PPTC polymer matrix 802 composed of conductive fillers 806 disposed within a polymer 808, and the polymer matrix is sandwiched between two metal foils 810. In the exemplary embodiment, the metal foils 810 each include nodules (bumps) on the side that abuts the PPTC polymer matrix 802, which strengthens the connection between the foil and the matrix.

[0054] The heater body 804 can be manufactured such that the PPTC heater including the heater body has a predefined self-regulating temperature. In the exemplary embodiment, the self-regulating temperature is 125°C, but the PPTC heater, specifically the heater body containing a polymer matrix composed of conductive fillers and a polymer, can be designed to meet a variety of consumer temperature preferences. Specifically, the types of the conductive fillers and the polymer, as well as their respective percentage combinations, can be adjusted to achieve a certain self-regulating temperature profile. Therefore, there are many different materials that can be used for the conductive fillers 806 and the polymer 808 that make up the PPTC polymer matrix 802.

[0055] In an exemplary embodiment, the polymer 808 includes a semi-crystalline polymer, such as polyethylene, polyvinylidene fluoride, ethylene tetrafluoroethylene, ethylene-vinyl acetate, ethylene and acrylic acid copolymer, ethylene butyl acrylate copolymer, perfluoroalkoxy, or certain combinations of one or more of these materials. Additionally, in an exemplary embodiment, the volume percentage of the polymer 808 in the PPTC polymer matrix 802 and the conductive filler 806 is between 50% and 99%, preferably between 60% and 95%. Thus, for example, at one end of this range, the polymer matrix can be composed of 50% polymer and 50% conductive filler. At the other end of this range, the polymer matrix can be composed of 99% polymer and 1% conductive filler. Preferably, the polymer matrix can be composed of 60% polymer and 40% conductive filler at one end, and 95% polymer and 5% conductive filler at the other end, and there are many other combinations between these preferences that can produce a preferred self-regulating temperature profile.

[0056] In an exemplary embodiment, the conductive filler 806 of the polymer matrix consists of carbon, graphene, carbon and graphene, conductive ceramics, carbon nanotubes, carbon with carbon nanotubes, or graphene with carbon nanotubes. In an exemplary embodiment, the conductive filler 806 of the PPTC polymer matrix 802 is made of carbon with a primary particle size between 10 nm and 100 nm, and its dibutyl phthalate (DBP) value is between 5 cm 3 / 100 g and 500 cm 3 / 100 g. Preferably, the DBP value ranges between 8 cm 3 / 100 g and 200 cm 3 / 100 g. Additionally, in an exemplary embodiment, the carbon content is between 20% and 65%, preferably between 25% and 30%.

[0057] In an exemplary embodiment, the conductive filler 806 of the PPTC polymer matrix 802 is made of graphene, where the graphene is prepared by mechanical or chemical methods, and the number of graphene layers ranges from one layer to hundreds of layers, preferably between one layer and thirty layers. In an exemplary embodiment, the thickness of each graphene layer is less than 20 nm, preferably between 0.34 nm and 10.2 nm. Additionally, in an exemplary embodiment, the graphene particle size ranges between 0.1 μm and 100 μm, preferably between 5 μm and 30 μm. The graphene content is between 1% and 50%, preferably between 4% and 30%.

[0058] In an exemplary embodiment, the conductive filler 806 of the PPTC polymer matrix 802 is made of carbon or conductive ceramics, where the carbon primary particle size is between 10 nm and 100 nm, and the DBP value is between 5 cm 3 / 100 g and 500 cm3 between 8 cm 3 / 100 g and 200 cm 3 / 100 g. The ratio of carbon or conductive ceramic to graphene can be between 0% / 100% (no carbon / conductive ceramic, 100% graphene) and 100% / 0% (100% carbon or conductive ceramic, no graphene), and any value therebetween. In a preferred embodiment, the ratio of carbon or conductive ceramic to graphene will be between 1% and 90%, preferably between 30% and 60%.

[0059] In an exemplary embodiment, the conductive filler 806 of the PPTC polymer matrix 802 is made of carbon nanotubes (CNT) or graphene with carbon, the carbon primary particle size is between 10 nm and 100 nm, and the DBP value is between 5 cm 3 / 100 g and 500 cm 3 / 100 g, preferably the DBP value ranges from 8 cm 3 / 100 g and 200 cm 3 / 100 g. In an exemplary embodiment, the nanotube length of the conductive filler 806 is between 10 nm and 10 μm, the diameter is between 2 nm and 50 nm, and the length / diameter of the CNT is between 5 and 5000, preferably between 100 and 1000. In an exemplary embodiment, the ratio of carbon to graphene or carbon to nanotubes is between 1% and 90%, preferably between 30% and 60%.

[0060] Furthermore, in an exemplary embodiment, the polymer 808 of the PPTC polymer matrix 802 or the conductive filler 806 or both are added with the following materials, including but not limited to antioxidants, dispersants, coupling agents, crosslinking agents, arc inhibitors, etc. Thus, the heater body 804 can be made of a variety of materials, and Figure 8 the heater body can be part of any PPTC heater disclosed and described herein.

[0061] Figure 9A - 9C and Figure 10A - 10C Two test examples of a PPTC heater using an annular shape (such as Figure 1A - 1C the PPTC heater 100) are provided according to an exemplary embodiment. The first test example ( Figure 9A - 9C ) tests a PPTC heater having a horizontal gap between two internal electrodes, such as Figure 1A - 1C shown, while the second test example ( Figure 10A - 10C ) tests a PPTC heater having a vertical gap between two internal electrodes, such as Figure 2A - 2C shown.

[0062] Figure 9A shows a test circuit where 12V is supplied to the circuit, the maximum current is 20A, and the room temperature is -40°C. The current and voltage are both measured across the PPTC heater. Additionally, the PPTC heater is characterized by an initial resistance of 0.38 Ω, the height of the PPTC heater is 9.7 mm (e.g., Figure 1A electrode 106 + gap 116 + electrode 102 in Figure 1B ), the thickness of the PPTC heater is 0.55 mm (e.g., Figure 1C electrode 102 + thickness 120 + electrode 118 in 2 ), the diameter of the annular-shaped PPTC heater is 9.5 mm, where the gap is approximately 0.4 mm (see, e.g., Figure 1C where the space between wires 108 and 110 is the gap), and the area of the PPTC heater (i.e., the area of the circle formed by the annular shape of the PPTC heater) is 2.5 cm Figure 1C electrode 118 in

[0063] Figure 9B is a plot of the temperature (°C) versus time (min) for the PPTC heater. The temperature starts at -40°C (room temperature) and then rapidly rises to approximately 120°C. This 120°C temperature is maintained for the duration of the test (100 minutes). Figure 9C is a plot of the resistance (Ω) versus temperature (°C) for the PPTC heater. As the temperature increases, the resistance of the PPTC heater remains rather low, and then, after the temperature reaches approximately 100°C, the resistance increases somewhat. Once the temperature reaches approximately 125°C, the resistance rises rapidly. Additionally, the temperature does not increase significantly above 125°C, indicating that the PPTC heater is self-regulating at approximately 125°C.

[0064] Figure 10A - 10C is characterized by a second test example for the PPTC heater according to an exemplary embodiment; Figure 10A shows a test circuit where 12V is supplied to the circuit, the maximum current is 20A, and the room temperature is -40°C. The current and voltage are both measured across the PPTC heater. Additionally, the PPTC heater is characterized by an initial resistance of 2.27 Ω, the height of the PPTC heater is 8.6 cm (e.g., Figure 2A electrode 206 + gap 216 + electrode 202 in Figure 2B(electrode 202 + thickness 220 + electrode 218) in it, the diameter of the annular-shaped PPTC heater is 1.2 cm, where the gap is approximately 0.4 mm (for example, see Figure 2C ), and the area of the PPTC heater is 2.5 cm 2 . In addition, there are two vertical electrodes on the inner surface (for example, Figure 2C electrodes 202 and 206 in Figure 2C ), and there is a full-size electrode on the outer surface of the PPTC heater (for example,

[0065] Figure 10B electrode 218 in Figure 10C is a graph plotting the temperature (°C) versus time (min) for the PPTC heater. The temperature starts at -40 °C (room temperature) and then rapidly rises to approximately 120 °C. This 120 °C temperature is maintained for the duration of the test (100 minutes). Figure 9C is a graph plotting the resistance (Ω) versus temperature (°C) for the PPTC heater. As the temperature increases, the resistance of the PPTC heater remains quite low (even lower than

[0066] Figure 11A Example 1 of Figure 11B and Figure 8 are representative diagrams showing the effect of the bending process of the PPTC material for the PPTC heater according to an exemplary embodiment, such as any PPTC heater disclosed herein, particularly a heater body containing a PPTC polymer matrix. Recall Figure 11A that the heater body 804 of any PPTC heater shown and described herein is composed of a PPTC polymer matrix 802. The PPTC polymer matrix 802 is composed of both a conductive material (filler) 806 and a polymer 808, and the PPTC polymer matrix is sandwiched between two metal foils 810. Similarly, in

[0067] In an exemplary embodiment, based on its material composition, the PPTC polymer matrix 1102 can be bent within the elastoplastic range, that is to say, it seems that both elastic and plastic deformations occur, although the plastic deformation is very small. The imaginary neutral line 1120 indicates that the PPTC polymer matrix 1102 has good bendability. Recall that the metal foil 1110 can include nodules disposed on a side adjacent to the PPTC polymer matrix 1102 to improve the connection between the two interfaces. In some embodiments, the modulus of the metal foil 1110 is high enough to move within the elastic range during bending. However, bending causes tension in the outer metal foil 1110 and half of the PPTC polymer matrix 1102, while compression in the inner metal foil and the other half of the PPTC polymer matrix 1102. Additionally, there is an imaginary neutral line 1120 between one half of the PPTC polymer matrix 1102 and the other half of the PTC polymer matrix 1102.

[0068] Heating the PPTC heater during the bending operation is not necessary. In one embodiment, during the bending operation, some heat is applied to the PPTC heater. However, the heating temperature is maintained below the melting temperature of the semi-crystalline polymer. Otherwise, the properties of the conductive particles in the PPTC polymer matrix will change, possibly interrupting the manufacturing process of the PPTC heater. Once the heater body 1104 assumes the desired annular shape after bending, an annealing process can be employed to relieve the bending stress.

[0069] Figure 11B is a graph showing the stress-strain characteristics of the Figure 11A PPTC heater body 1104 according to an exemplary embodiment. For both the outer metal foil 1110 (σ foil ) and the PPTC polymer matrix 1102 (σ pPTC ), the stress given by σ is shown. For the outer metal foil 1110 (E foil ) and the PPTC polymer matrix 1102 (E pPTC ), the elastic modulus given by E is additionally given. From this information, the strain ε for each material can be calculated using the formula σ = Eε.

[0070] Figure 12is a flowchart showing process steps for manufacturing a PPTC heater (such as any one of PPTC heaters 100, 200, 400, 500, and 600) according to an exemplary embodiment. The manufacturing process starts with a polymer and conductive filler mixing operation (block 1202) as these constitute the polymer matrix described above. Then, a hot melt extrusion process is performed on the polymer matrix (block 1204). Hot melt extrusion (HME) is a process that applies heat and pressure to melt the polymer and force it through an orifice in a continuous process. This enables the polymer matrix to assume a predefined uniform shape and density. Then, the polymer matrix is extruded into a sheet (block 1206). Then, the extruded sheet of the polymer matrix is laminated with metal foils on both sides (block 1208), forming a sandwich with the polymer matrix located therebetween and the metal foils (electrodes), as described in the aforementioned PPTC heaters.

[0071] After the metal foil lamination, a PPTC cross-linking operation is performed on the polymer matrix (block 1210). In polymer chemistry, cross-linking uses cross-linking to promote changes in the physical properties of the polymer. Here, the polymer matrix is cross-linked to produce a PPTC with desired properties. In an exemplary embodiment, PPTC cross-linking is achieved by electron beam, gamma radiation, or chemical cross-linking. Then, a foil-PPTC-foil sandwich sheet is formed (block 1212). Then, the sandwich sheet is etched on one side (where N = 1) or on both sides (if N = 3) to the designed chip size (block 1214). Then, the sandwich sheet is cut into individual chips based on the etching (block 1216), where each chip is a sandwich of metal foil-PPTC-metal foil, as desired for a PPTC heater.

[0072] Next, the individual chips are each bent to form an annular shape with a specified diameter (block 1218). Although the embodiments described herein are circular for mounting above a cylindrical actuator, the individual chips may alternatively be bent into other shapes suitable for the desired application. For example, the chip can be bent to form a rectangular shape for coupling with an actuator or other device having a shape similar to a cube or rectangular cube. Or, the chip can be bent into other geometric shapes suitable for coupling with an actuator, which can be a triangle, pyramid, prism, trapezoid, hexagon, octagon, pentagon, or any one of a variety of other geometric shapes. Or, the chip can be bent into an oval shape suitable for coupling to an actuator or other device having a non-geometric shape. In an exemplary embodiment, the shape of the PPTC heater is bent at this stage to conform to the shape of the device to be heated.

[0073] After bending the chips into the desired shape, wire assembly is performed, where wires (e.g.,Figure 1A The wires 108 and 110) are attached to the sandwiched chip (frame 1220). Then, an annealing process is performed in which the sandwiched chip is heated and slowly cooled to eliminate internal stress and toughen the material. Then, the sandwiched chip is coated with a suitable material to protect the device or add other functions to the device (frame 1222). For example, in one embodiment, a temperature-sensitive coating is added to cause the device to change color at different temperatures. Then, an R test of the device is performed (frame 1226) and the device is encapsulated in a suitable encapsulation material (frame 1228). The PPTC heater manufacturing process steps are thus completed.

[0074] Figure 12 One or more of the PPTC processing steps in can be performed in an order other than the order shown. For example, the operation of block 1224 can be performed before the operation of block 1218. Those of ordinary skill in the art will recognize that there are many ways in which these manufacturing operations can be performed.

[0075] As used herein, an element or step recited in the singular and preceded by the word "a" or "an" should be understood as not excluding a plurality of elements or steps, unless such exclusion is explicitly recited. In addition, a reference to "one embodiment" of the present disclosure is not intended to be construed as excluding the existence of additional embodiments that also incorporate the recited features.

[0076] Although the present disclosure refers to certain embodiments, many modifications, substitutions, and changes to the described embodiments are possible without departing from the scope and field of the present disclosure as defined in the appended claims. Accordingly, it is intended that the present disclosure not be limited to the described embodiments, but rather have the full scope defined by the language of the following claims and their equivalents.

Claims

1. A polymer positive temperature coefficient (PPTC) heater, comprising: A heater body, which includes a conductive filler and a semi-crystalline polymer, and the heater body is configured as a rectangular sheet having a first thickness; A first electrode, which is disposed on a first side of the heater body, wherein the first electrode is coupled to a first wire; A second electrode, which is disposed on the first side of the heater body and spaced apart from the first electrode to define a gap therebetween, the gap exposing the heater body and having a second thickness greater than the first thickness, wherein the second electrode is coupled to a second wire, and wherein the gap extends in a direction parallel to the first wire and the second wire; And A third electrode, which is disposed on a second side of the heater body opposite to the first side; Wherein, the heater body, the first electrode, the second electrode and the third electrode are formed in an annular shape, and the first electrode and the second electrode are disposed on an inner surface of the annular shape.

2. The PPTC heater according to claim 1, wherein, The heater body has a self-regulating temperature of 125 °C.

3. A polymer positive temperature coefficient (PPTC) heater, comprising: A heater body, which includes a conductive filler and a semi-crystalline polymer, and the heater body is configured as a rectangular sheet having a first thickness; A first electrode, which is disposed on a first side of the heater body, wherein the first electrode is coupled to a first wire; A second electrode, which is disposed on the first side of the heater body and spaced apart from the first electrode to define a gap therebetween, the gap exposing the heater body and having a second thickness greater than the first thickness, wherein the second electrode is coupled to a second wire, and wherein the gap extends in a direction perpendicular to the first wire and the second wire; And A third electrode, which is disposed on a second side of the heater body opposite to the first side; Wherein, the heater body, the first electrode, the second electrode and the third electrode are formed in an annular shape, and the first electrode and the second electrode are disposed on an inner surface of the annular shape.

4. The PPTC heater according to claim 3, wherein, The first thickness is 10 mils, and the second thickness is 50 mils.

5. The PPTC heater according to claim 3, wherein, The heater body has a self-regulating temperature of 125 °C.

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