FIELD OF THE INVENTION The present invention relates to an improved stator for an axial field rotary energy device operating as a motor or a generator as described in U.S. Pat. No. 7,109,625 to Jore et al.
BACKGROUND OF THE INVENTION The size of machines that may be produced with a one-piece printed circuit board (PCB) stator is limited by the capability of the processing equipment found in a PCB manufacturing facility. High volume facilities have a maximum size PCB panel that can be processed on automated equipment. Certain lower volume facilities routinely process larger PCB panel sizes than the high volume manufacturers but there is a higher cost due to more labor and higher material costs. In order to cost effectively produce large axial field rotary machines that incorporate a PCB stator, a segmented PCB stator is shown and described. The segments allow a much larger diameter machine than is possible with single piece PCB stator designs. Further, the segments may be produced in high volume manufacturing facilities that provide the best cost.
SUMMARY OF INVENTION The present invention provides an axial rotary energy device which is arranged in a multi-phase electric current configuration. The device includes a rotor having a plurality of permanent magnet poles secured thereto and further includes a segmented stator assembly having a plurality of segments arranged in an annular array. Each stator segment is constructed by stacking a plurality of printed circuit board power conductor layers together with a plurality of much larger diameter machine than is possible with single piece PCB stator designs. Further, the segments may be produced in high volume manufacturing facilities that provide the best cost.
SUMMARY OF INVENTION The present invention provides an axial rotary energy device which is arranged in a multi-phase electric current configuration. The device includes a rotor having a plurality of permanent magnet poles secured thereto and further includes a segmented stator assembly having a plurality of segments arranged in an annular array. Each stator segment is constructed by stacking a plurality of printed circuit board power conductor layers together with a plurality of printed circuit board series layers. Each stator segment having at least one working power conductor layer for each phase of the electric current and at least one series conductor layer associated with one power conductor layer. Each power conductor layer and series conductor layer having radial conductors extending from an inner diameter via to an outer diameter via. The vias are provided for electrically connecting selected ones of the radial conductors of the series conductor layer to selected ones of the radial conductors of the power conductor layer. Each power conductor layer includes a pair of positive and negative terminal vias for one phase of the electric current connected to selected outer vias of the power conductor layer. A daughter printed circuit board is used for electrically connecting two adjacent segments together. Each daughter printed circuit board having a first portion electrically connected to a negative terminal via located in one segment and a second portion electrically connected to a positive terminal via located in an adjacent segment. A current conductor is provided on the daughter printed circuit board for electrically connecting the negative terminal via and the positive terminal via together.
BRIEF DESCRIPTION OF THE DRAWINGS In order that the invention may be clearly understood and readily carried into effect, a preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings wherein:
FIG. 1 is an exploded assembly view with parts broken away of an axial field device utilizing the present invention;
FIG. 2 is a cross-sectional view taken along the line 2-2 in FIG. 1 showing a first embodiment of the present invention;
FIG. 3 is a schematic view showing the electrical circuit for one phase of the axial field device through selected stator segments and daughter printed circuit boards;
FIG. 4 is a detail view of one segment of a power layer of a stator board for phase A according to the first embodiment of the present invention;
FIG. 5 is a detail view of one segment of a series layer of a stator board for phase A according to the first embodiment of the present invention;
FIG. 6 is a detail view of one segment of a power layer of a stator board for phase B according to the first embodiment of the present invention;
FIG. 7 is a detail view of one segment of a series layer of a stator board for phase B according to the first embodiment of the present invention;
FIG. 8 is a detail view of one segment of a power layer of a stator board for phase C according to the first embodiment of the present invention;
FIG. 9 is a detail view of one segment of a series layer of a stator board for phase C according to the first embodiment of the present invention;
FIG. 10 is a diagram showing one arrangement of the stacking of power layers and series layers for phases A, B and C;
FIG. 11 is a diagram showing another arrangement of the staking of power layers and series layers for phases A, B and C;
FIG. 12 is a detail view of one segment of a power layer of a stator board according to a second embodiment of the present invention;
FIG. 13 is a detail view of one segment of a power layer of a stator board according to a third embodiment of the present invention;
FIG. 14 is a plan view of a stator board showing the arrangement of stator segments and daughter printed circuit boards according to the first embodiment of the present invention;
FIG. 15 shows a daughter printed circuit board for the A phase;
FIG. 16 shows a daughter printed circuit board for the B phase;
FIG. 17 shows a daughter printed circuit board for the C phase;
FIG. 18 shows a daughter printed circuit board for the A, B, and C phases electrically isolated;
FIG. 19 is a cross sectional view taken along the line 2-2 in FIG. 1 showing a fourth embodiment of the present invention; and
FIG. 20 is a perspective sectional view taken along the line 20-20 in FIG. 14.
DESCRIPTION OF A PREFERRED EMBODIMENT An axial gap device 10 according to the present invention is shown in FIG. 1 with a housing 12A having a number of terminal covers 14, a pair of bearings 16, a drive shaft 18, a pair of rotors 20A and 20B each having an annular array of permanent magnets 22 that alternate polarity around the array, another housing 12B, and a segmented stator assembly 24. The segmented stator assembly 24 is comprised of a pair of clamp rings 26A and 26B, a number of fasteners such as bolts 28, a plurality of terminal lugs 30, and a plurality of stator segments 32. The stator segments 32 are comprised of multiple layer printed circuit boards that are shaped to fit together to form an annular array of stator segments 32. The multiple layers of conductive material in each stator segment 32 provide a number of turns for each electrical phase of the axial gap device 10.
FIG. 2 illustrates how the clamp rings 26A and 26B and bolts 28 fasten onto either side of the inward edge of the stator segments 32. The outer edge of the stator segments 32 are held in place by the clamping force of the housings 12A and 12B. The clamp rings 26A and 26B and the housings 12A and 12B suspend the stator assembly 24 in the air gap between the permanent magnets 22 mounted on the rotors 20A and 20B. As shown in FIG. 1, each stator segment 32 has a plurality of terminal lugs 30. The terminal lugs 30 are made of an electrically conductive material such as copper. The number of lugs on each segment depends upon the number of electrical phases in the machine. There is a positive and a negative terminal lug 30 for each phase. The illustrated device has three electrical phases and so each stator segment 32 has six terminal lugs 30. FIG. 2 shows how each terminal lug 30 passes through a lug opening 34 in the housing 12A to electrically connect the stator segment 32 to a daughter printed circuit board 36. An insulating material may be placed around the lug 30 where it passes through the lug opening 34 to prevent the lug 30 from making electrical contact with the housing 12A. The terminal lugs 30 are attached to the stator segments 32 and to the daughter printed circuit boards 36 by soldering or by fastening with some other means, such as a threaded nut over a threaded portion of a terminal lug 30. The multiple layer daughter printed circuit boards 36 electrically connect each phase in one stator segment 32 to each corresponding phase in an adjoining stator segment 32.
FIG. 3 diagrammatically shows the electrical circuit for one phase of the axial gap device 10 through selected stator segments 32 and daughter printed circuit boards 36. An electrical current enters a stator segment 32 through a positive terminal lug 30 for the particular phase. The current flows through a first working turn 38 (a working turn is the torque producing portion of the circuit within the magnetic gap of the axial field device 10), then into an inner turn 40, then into a second working turn 42, then into an outer end turn 44, and then into third working turn 46, and so on until the electrical current has passed through all of the turns for the particular phase in the stator segment 32. The first and third working turns 38 and 46 are associated with one magnetic pole and so the axial field device 10 shown is said to have two turns. The electrical circuit of the diagram in FIG. 3 is shown with two working turns however the number of working turns may be any number depending upon the performance requirement of the axial field device 10 and limited only by the physical space available for working turns in the stator segment 32. Also illustrated in FIG. 3 is the relationship between the number of stator segments 32 in the axial field device 10 to the number of magnet poles of magnets 22. In the preferred embodiment, there will be two magnet poles for every stator segment 32.
Continuing in FIG. 3, electrical current flows from the last working turn into the negative terminal lug 30 and the into the daughter printed circuit board 36 which conducts the electrical current from the negative terminal lug 30 of the first stator segment 32 to the positive terminal lug 30 of a second stator segment 32. The electrical current then flows through all of the turns for the particular phase in the second stator segment 32 and then out through the negative terminal lug 30 of the second stator segment to a second daughter printed circuit board 36. The electrical current is conducted through the entire segment array in the same manner.
FIG. 4 shows a pattern etched into one layer of conductive material in one of the stator power segments 32A. The pattern has a variety of conductive paths that relate to three electrical phases of the axial field device 10. The pattern has A+, B+, C+, A−, B−, and C− terminal lugs 30. Each of the terminal lugs 30 terminate in a terminal pad 48. Each of the terminal pads 48 have a plurality of terminal via 50 electrically connected to a respective terminal pad 48. A terminal conductor 52 electrically connects a terminal pad 48 to an outer via pad 54 having a plurality of outer vias 56. The pattern shown in FIG. 4 is called a power layer for electrical phase A since it is on this layer that the electrical connection is made to the stator segment 32 for phase A. The terminal conductors 52 of the power layer are continuous with terminal pads A+and A−. Terminal pads 48 for B+, C+, B−, and C− are in contact with the corresponding terminal lugs 30 but the pads are not connected to terminal conductors 52 on this layer.
In FIG. 4, arrows show the direction of an electrical current to illustrate the relationships of the conductors of the power layer for phase A. The arrows are for reference only since the axial field device operates as a brushless DC or synchronous AC motor or generator. The current is shown to begin at the terminal pad 48 A+ and flow through the terminal conductor 52 to the outer via pad 54. The outer via pad 54 is continuous with a first working conductor 38 on the power layer for phase A. The first working conductor 38 connects the electrical current to the inner via pad 58. As shown in FIG. 4, the first working conductor 38 is substantially within the flux of the permanent magnets 22. Electrical current flowing through the first working conductor 38 will create the Lorenz force that acts between the flowing current and the magnetic flux. The outer via pad 54 has a number of outer vias 56 which are plated through holes that electrically connect the outer via pad 54 on the power layer for phase A to the corresponding outer via pads 54 on all of the other conductive layers of the stator segment 32. The inner via pad 58 also has a number of inner vias 60 that electrically connect the inner via pad 58 on the phase A power layer to the corresponding inner via pads 58 on all of the other conductive layers of the stator segment 32.
As seen in FIGS. 4 through 9, the outer via pad 54 is continuous with the first working conductor 38 on each of the conductive layers. Therefore, the outer vias 56 and the inner vias 60 connect all of the working conductors together so that the electrical current flowing through the first working conductor 38 on the power layer for phase A is in parallel with the corresponding working conductors 38 on all of the layers of the stator segment. This is the same for all of the working conductors for all of the phases of the stator segment.
Continuing in FIG. 4, the electrical current flows from the inner via pad 58 to the first inner end turn 40. From the first inner end turn 40, the electrical current flows to an inner via pad 58 which is connected to a second working conductor 42. The second working conductor 42 carries the electrical current to an outer via pad 54. The circuit appears to end at the outer via pad 54 but as previously described, the inner and outer vias 60 and 56 connect all of the second working conductors 42 on all of the layers of conductive material in parallel. The next pattern to be described shows how the circuit for phase A is continued.
FIG. 5 shows a pattern etched into another conductive layer of the stator series segment 32B. The pattern shown in FIG. 5 is called a series layer for electrical phase A since it contains the outer end turns that electrically connect the working turns for phase A in series. From the outer via pad 54 at the end of the second working conductor 42, the electrical current flows into the first outer end turn 44. The electrical current then flows to an outer via pad 54 with outer vias 56 and then to a third working conductor 62. From the third working conductor 62, the electrical current flows into an inner via pad 58 with inner vias 60. The third working conductors 62 on all layers of conductive material of the stator segment are electrically connected in parallel by the outer vias 56 and the inner vias 60. The electrical current continues from the inner via pad 58 to a second inner end turn 64 and then to an inner via pad 58 and then to a fourth working conductor 66. The electrical current continues on through the working conductors, outer via pads, outer end turns, inner via pads and inner end turns as shown in FIG. 5 until reaching a tenth working conductor 68. From the tenth working conductor 68, the electrical current flows to an outer via pad 54 with outer vias 56. The circuit appears to end at the outer via pad 54 but as previously described, the inner and outer vias 60 and 56 connect all of the tenth working conductors 68 on all of the layers of conductive material in parallel. Referring again to FIG. 4, the electrical current moves from the outer via pad 54 associated with the tenth working conductor to a terminal conductor 52 and then to an A− terminal pad 48.
The patterns and electrical current flow is similar for the power and series layers for. phase B and phase C. FIG. 6 shows a pattern etched into another layer of conductive material of the stator power segment 32A that is a power layer for phase B. FIG. 7 shows a pattern on another layer that is a stator series segment 32B for phase B. FIG. 8 shows a pattern on a stator power segment 32A for phase C. And FIG. 9 shows a pattern on a stator series segment 32B.
The multiple layer stator segments 32 of the annular array comprising the entire stator are constructed by stacking the individual stator power segments 32A and stator series segments 32B for the A, B and C phases one on top the other with a substitute dielectric layer 33 provided between each layer. The stacking order of the stator power segments 32A and the stator series segments 32B for phases A, B and C is selectable. There may be duplicates of each layer type in the stator segment. There may be a greater number of series layers than power layers in the stator segment. The order of the layers is preferably selected to provide an even distribution of electrical current throughout different layers of the stator segment and particularly so that there is an even distribution of electrical current through the axial length of the inner and outer vias. The main benefit of the even distribution of the electrical current is to optimize the thermal dissipation of the stator segment 32. The durability of each stator segment 32 is enhanced by reducing the thermal stress that can cause delamination of the layers and cracking in the walls of the vias.
As a non-limiting example, a stator segment with eighteen layers might have two power layers for phase A, four series layers for phase A, two power layers for phase B, four series layers for phase B, two power layers for phase C, and four series layers for phase C. FIG. 10 shows one possible stacking arrangement of the layers that provides an even distribution of the electrical current. FIG. 11 shows another possible stacking arrangement of the layers that provides an even distribution of the electrical current and added isolation of the phases for medium and high voltages.
FIG. 12 shows another embodiment of the stator segment 32. In this embodiment, a pattern etched into a conductive layer of a stator power segment 32A′ includes the terminal conductors 52 for phases A, B, and C. In this embodiment, the power layers for phases A, B, and C as described above would be identical. The main benefit of this embodiment is that there are more terminal conductors 52 in parallel for each phase. However, the inner end turns that were present on the power layers of 32A shown in FIGS. 4, 6, and 8 are absent in this embodiment. With this stator power segment 32A′, it is necessary to use the three stator series segments 32B for the phases A, B and C as shown in FIGS. 5, 7 and 9.
FIG. 13 illustrates another embodiment of the stator segment where the inner end turns are present on a stator power segment 32A″ that contains terminal conductors 52 for phases A, B, and C. This pattern would then be a power layer for phase A and the power layers in this embodiment therefore are not identical. The power layer for phase B would contain the inner end turns for phase B and the power layer for phase C would contain the inner end turns for phase C. With this stator segment 32A″ it is again necessary to use the three stator series segments 32B for the phases A, B and C as shown in FIGS. 5, 7 and 9.
FIG. 14 illustrates the arrangement of stator segments 32 and daughter printed circuit boards 36 in one embodiment of a stator assembly. The stator assembly has phase conductor wires 70 for phases A, B, and C; an inner clamp ring 26A; bolts 28; and a plurality of daughter printed circuit boards 36 attached to an array of stator segments 32. The stator assembly 24 includes six terminal lugs 30 which are connected to the six phase conductor wires 70 as shown. The phase conductor wires 70 may be arranged as shown or may be configured for a wye or delta connection with the stator assembly 24 as is well known in the art.
The daughter printed circuit boards 36 are used to electrically connect adjacent stator segments 32 together. As shown in FIG. 20, the daughter boards 36 are arranged so that three terminal lugs 30 (A−, B− and C−) of a daughter printed circuit board 36 are positioned over the corresponding terminal lugs 30 of one stator segment 32 and three terminal lugs 30 (A+, B+ and C+) of the same daughter printed circuit board 36 are positioned over the corresponding terminal lugs 30 of the adjacent stator segment 32.
FIGS. 15 through 17 show the electrical current path on each of the layers of conductive material in the daughter printed circuit boards 36. FIG. 15 shows a pattern etched into a daughter printed circuit board 36 with terminal vias 50 for A− and A+ having an electrical current path between them. The terminal vias 50 for B−, C−, B+, and C+ are isolated from the terminal vias 50 for A− and A+. The terminal lugs 30 have terminal pads 48 with vias 50 that electrically connect the terminal pads 48 to the corresponding terminal pads 48 on all of the other layers of conductive material of the daughter printed circuit boards 36. In FIG. 15, the electrical current for phase A flows from the A−terminal pad 48 through the daughter printed circuit board 36 to the A+ terminal pad 48. In FIG. 16, the electrical current for phase B flows from the B− terminal pad 48 through the daughter printed circuit board 36 to a B+ terminal pad 48. In FIG. 17, the electrical current for phase C flows from C− terminal pad 48 through the daughter printed circuit board 36 to a C+ terminal pad 48. FIG. 18 shows daughter printed circuit board 36 which has all of the terminal pads 48 for the A−, B−, C−, A+, B+, and C+ isolated from one another. In a preferred embodiment, the daughter printed circuit boards 36 shown in FIGS. 15-17 are stacked one upon the other with a dielectric substrate layer in between them. The daughter printed circuit board 36 shown in FIG. 18 is preferably placed on the first and the last layer of the daughter printed circuit board stack in order to electrically isolate the phases on the exterior surfaces the daughter printed circuit boards 36.
FIG. 19 shows another embodiment of the invention which has a stator assembly 24 with two arrays of stator segments 32. The stator segments are electrically connected in parallel by the terminal lugs 30. An outer spacer 74 and an inner spacer 76 keep the stator segments apart to allow for electrical isolation and thermal dissipation. Also shown in FIG. 19 is an arrangement of two stacks of daughter printed circuit boards 36 mounted in parallel across each set of terminal lugs 30. As should be understood by this example, there can by more than two arrays of stator segments 32 within the stator assembly 24. Also it should be understood that there may by more than two stacks of daughter printed circuit boards 36 mounted in parallel across each set of terminal lugs 30. The benefit of having arrays of stator segments 32 and stacks of daughter printed circuit boards 36 mounted in parallel is to reduce the electrical resistance of the circuit.
While the fundamental novel features of the invention have been shown and described, it should be understood that various substitutions, modifications, and variations may be made by those skilled in the arts, without departing from the spirit or scope of the invention. Accordingly, all such modifications or variations are included in the scope of the invention as defined by the following claims:
