Patent Description:
However, as the commutators rotate under the brushes, the brushes experience wear, and eventually the brushes have to be replaced. The brushes are typically the limiting wear item in the machine which determines the amount of time that a starter-generator can be on an aircraft before the starter-generator has to be removed for overhaul. It is desirable to create starter-generators which will allow for a longer time between overhauls, but this requires finding an alternative to the switching function of the commutators and brushes.

One way of accomplishing this is to use electrical components, such as MOSFETs, to perform this switching function. Sensors can measure the rotational speed and position of the rotor, and electronics can use those measurements to know when to send signals to the MOSFETs for them to switch on or off. Using electronics to drive MOSFETs can replace the rotation based switching function of the brushes and commutators.

However, using such MOSFETs in this manner brings its own set of problems. One problem is where to house them, for these electronics take up more space than traditional commutators and brushes. Another problem is how to cool the MOSFETs, for these electronics generate more heat than the traditional commutators and brushes.

To address these issues, a brushless starter-generator with a separate box that houses the electronics can be utilized. However, there are potential downsides to this solution. For example, additional space has to be provided on the aircraft for the separate box.

Additionally, high-current capacity wires have to be run between the separate box and the starter-generator. These high-current capacity wires are thick and heavy. This results in additional weight and complicated assembly techniques. Neither of these items is desirable for aircraft applications. <CIT> discloses a brushless starter-generator system contained within a single housing, housing a brushless, rotating, machine kinetically connectable to a drive spline, and a power control unit coupled to the rotating machine, wherein the rotating machine is selected from the group consisting of a synchronous machine, a permanent magnet machine, and an induction machine.

Accordingly, a more advanced starter-generator is needed.

In view of the foregoing, a rotating machine assembly according to claim <NUM> is proposed. This assembly includes a rotating machine that has a cover that defines an outer surface of the rotating machine and a stator disposed within the cover. The stator is stationary with respect to the cover. The rotating machine also includes a shaft rotatably disposed at least partially within the cover so as to define a rotation axis.

The shaft includes a first end that is connectable to an aircraft engine and a second end that is opposite the first end. The rotating machine also includes a rotor attached to the shaft, the rotor being movable with respect to the stator and a power module including at least one MOSFET that periodically reverses an electrical current direction of the rotor. The power module includes the at least one MOSFET is disposed within the cover.

With reference to <FIG>, a rotating machine assembly <NUM> is shown. Without departing from the scope of the disclosure, the rotating machine assembly <NUM> could be an electric motor (e.g., a starter utilized on an aircraft to start the engine) or a generator that converts rotary motion to electrical energy. Alternatively, the rotating machine assembly <NUM> can be a combination starter-generator that is used to start the engine of an aircraft (i.e., startup mode) and also generate electricity for usage by the aircraft (i.e., generating mode).

As shown in <FIG>, the rotating machine assembly <NUM> includes a rotating machine <NUM>, a chassis <NUM> that defines an air tunnel <NUM>, a fan <NUM>, and a control enclosure <NUM> with a control module <NUM>. The rotating machine <NUM> includes a cover <NUM>, a stator <NUM>, and a shaft <NUM>. The shaft <NUM> includes a first end 28a and a second end 28b and defines a rotation axis <NUM>.

As shown in <FIG>, the rotating machine assembly can also include a shaft sensor <NUM> that can sense or measure a rotational speed and position of the shaft <NUM>, and hence a rotor <NUM>. The shaft sensor <NUM> can be of known technology. Further, the shaft sensor <NUM> can be disposed in a variety of locations without departing from the scope of the disclosure. Additionally, the shaft sensor <NUM> can be connected to the control module <NUM> by wired or wireless means to allow communication between the shaft sensor <NUM> and the control module <NUM>.

The rotating machine <NUM> also includes the rotor <NUM> that is connected to the shaft <NUM>. The rotating machine <NUM> also includes a power module <NUM> with at least one MOSFET <NUM>. As shown in <FIG>, the at least one MOSFET <NUM> is disposed on a circuit board <NUM>. The circuit board <NUM> may be a printed circuit board.

For convenience, this disclosure will refer to the printed circuit board(s) as merely a circuit board, but will be understood to include printed circuit boards. For clarity, the electrical wires to communicate electricity, whether for power purposes or for signal communication, between the power module <NUM>, the MOSFETs <NUM>, and the other various components has been omitted from the drawings.

With attention once again to <FIG>, the cover <NUM> defines an outer surface 24a of the rotating machine <NUM> and serves to contain the components together in an easily manipulatable package to aid in installation into the aircraft The cover <NUM> may be made of any number of materials, including, for example, sheet stock. As illustrated, the cover <NUM> may be attached to the chassis <NUM> with fasteners, but other means of attachment are contemplated. The cover <NUM> can be non-structural in nature. Further, the cover <NUM> defines a cylindrical shape in cross-section in a plane orthogonal to the rotation axis <NUM>.

For reference, this cylindrical shape of the present rotating machine <NUM> has an outer diameter that is equal to an outer diameter of a traditional rotating machine that uses brushes and commutators for rotation based switching. By having the same outer diameter as a traditional rotating machine, space is conserved and retrofitting of machine assemblies is simplified. Further, keeping the outer diameter of the present rotating machine <NUM> the same as a traditional starter-generator and not requiring a separate box with heavy wires connecting it to the rotating machine <NUM> will make it easier for installation of the present rotating machine assembly <NUM> into the aircraft.

The stator <NUM> is of known construction. The stator <NUM> is a stationary part of the rotating machine <NUM>, and thus is stationary with respect to the cover <NUM>. When the rotating machine assembly <NUM> is a generator, energy flows through the stator <NUM> to or from the rotor <NUM> as is known. When the rotating machine assembly <NUM> is a starter, the stator <NUM> provides a rotating magnetic field that drives the rotating armature, as is also known in the art. When the rotating machine assembly <NUM> is a generator, the stator <NUM> converts the rotating magnetic field to electric current. The stator <NUM> is disposed within the cover <NUM>.

The rotating machine <NUM> also includes the shaft <NUM> that is rotatably disposed at least partially within the cover <NUM>. As illustrated, the first end 28a of the shaft extends in a manner so as to not be contained within the cover <NUM>. The shaft <NUM> can be circular in cross-section in a plane orthogonal to the rotation axis <NUM>. The shaft <NUM> may be received within one or a plurality of bearings.

As shown in <FIG>, the first end 28a of the shaft <NUM> can include a plurality of splines so as to rotatably connect the rotating machine assembly <NUM> to an aircraft engine. It will be appreciated that means of connecting the rotating machine assembly <NUM> to the aircraft engine other than the splines could be utilized without departing from the scope of the disclosure. The second end 28b of the shaft <NUM> is opposite the first end 28a of the shaft <NUM>, along the rotation axis <NUM>.

The rotating machine <NUM> also includes the rotor <NUM>, which is attached or coupled to the shaft <NUM> so that the shaft <NUM> and the rotor <NUM> rotate together. The rotor <NUM> is of known construction. Rotation of the rotor <NUM> is due to the interaction between the windings and magnetic fields which produces a torque around the rotation axis <NUM>. The rotor <NUM> is movable with respect to the stator <NUM>.

As shown in <FIG>, the power module <NUM> includes the at least one MOSFET <NUM>. However, as illustrated, multiple MOSFETs <NUM> could be utilized without departing from the scope of the disclosure. The MOSFET <NUM> is a metal-oxide-semiconductor field-effect transistor. In particular, the MOSFET <NUM> is a type of field-effect transistor (FET) that is fabricated by the controlled oxidation of silicon. The MOSFET <NUM> has an insulated gate (not shown), whose voltage determines the conductivity of the device.

This ability to change conductivity with the amount of applied voltage can be used for amplifying or switching electronic signals. In terms of the present disclosure, the MOSFET <NUM> periodically reverses an electrical current direction of the rotor <NUM>, thereby taking the place of appropriate power switching electronics. For example, the MOSFET <NUM> takes the place of the electrical switching function of the commutators and brushes that are found in traditional rotating machine <NUM> assemblies. As illustrated, the power module <NUM> including the at least one MOSFET <NUM> is disposed within the cover <NUM>.

A traditional assembly includes brushes that make or break contact on electrical bars of the commutator. These electrical bars run parallel to the rotational axis, and as the shaft rotates, the brushes make or break electrical contact with these electrical bars of the commutator.

Thus, the electrical contact from the brushes to the commutator bars is a function of the shaft rotational position. This rotational switching function, which is a function of the shaft rotational position, is replaced by the MOSFETs <NUM> in the present disclosure. Thus, as the shaft <NUM> rotates, the control module <NUM>, in view of a signal from the shaft sensor <NUM>, tells the MOSFETs <NUM> to switch on or off depending on the rotational position of the shaft <NUM>.

The plurality of MOSFETs <NUM> can disposed on a plurality of printed circuit boards <NUM> that are circumferentially mounted to the chassis <NUM> so as to be between the air tunnel <NUM> and the cover <NUM> to radially surround the air tunnel <NUM>. As illustrated, there are six circuit boards <NUM> which each include a plurality of MOSFETs <NUM>.

Mounting the MOSFETs <NUM> in this way keeps the wasted space to a minimum while providing efficient ways of dissipating the heat generated into either the phase changer material or into the air flow. Further, a plurality of pads <NUM> can be respectively disposed between the plurality of printed circuit boards <NUM> and the chassis <NUM>. The pads <NUM> can have a generally rectangular shape and be of nominal thickness so as to be of sheet-like construction.

Further, the plurality of pads <NUM> are thermally conductive electrical insulators to electrically isolate the printed circuit boards <NUM> from the chassis <NUM>. The pads <NUM> can be very thin so as to be similar in thickness to a sheet of paper. Thus, as shown in the drawings, the pads <NUM> can appear to be merely an outer surface of the chassis <NUM>, but are in fact separate from the chassis <NUM>,.

The control module <NUM> is disposed within the control enclosure <NUM>. It is noted that the control module <NUM> is separate from and distinct from the power module <NUM>. Further, the control enclosure <NUM> is mounted on the cover <NUM> of the rotating machine <NUM> so as to be external to and attached to the rotating machine <NUM>. As illustrated, the control enclosure <NUM> had a rectangular box shape construction that is mounted to the outer diameter of the rotating machine <NUM>.

As will be understood, the power module <NUM> switches the power on and off with the MOSFETs <NUM>. However, the power module <NUM> itself does not know when to switch that power on and off. In contrast, the control module <NUM> receives an input from the shaft sensor <NUM>, so the control module <NUM> knows when the power should be switched on or off.

The control module <NUM> then sends a low power electrical signal to the power module <NUM>, and that low power electrical signal tells the power module <NUM> when to switch on or off. Stated another way, the power module <NUM> functions similar to electrical relays, and the control module <NUM> is telling the relays when to activate.

With reference to <FIG>, the chassis <NUM> is received in the cover <NUM> and is at least partially disposed adjacent the second end 28b of the shaft <NUM>. The chassis <NUM> can be made of any number of materials, including for example, aluminum. Aluminum offers good strength, light weight, and high thermal conductivity. The chassis <NUM> combines and performs several functions. For example, the chassis <NUM> serves as a heat sink.

Further, the chassis <NUM> can be a structural part to which all other parts of the power module <NUM> can be attached and can also provide an important part of the rotating machine assembly <NUM> interface with the aircraft. Notably, the chassis <NUM> can provide all attachment locations for every component in the power module <NUM>, as well as connections to the rest of the rotating machine <NUM> and to an air inlet hose (not shown). As the chassis <NUM> is a single component that performs many functions, the size of the rotating machine assembly <NUM> is kept to a minimum.

As shown in <FIG> and <FIG>, the chassis <NUM> can include a main body portion 14a and an inlet portion 14b disposed at opposite ends thereof. The inlet portion 14b and the first end 28a of the shaft <NUM> are disposed at opposite ends of the rotating machine assembly <NUM> such that the main body portion 14a is disposed therebetween. The main body portion 14a includes a shroud 14a' and defines a main body inner perimeter and a main body outer perimeter. The shroud 14a' can be used as a housing for the fan <NUM> and further direct the air that has traveled through the air tunnel <NUM>.

Further, the inlet portion 14b defines an inlet inner perimeter and an inlet outer perimeter. The main body outer perimeter is greater than the inlet outer perimeter and the main body inner perimeter. Due to the illustrated shape of the main body portion 14a, the shroud 14a', and the inlet portion 14b, it will be appreciated that the term perimeter could be replaced with the term diameter without departing from the scope of the disclosure.

This shape allows for the air to be efficiently passed through the air tunnel <NUM> and properly cool the MOSFETs <NUM> as will be described in more detail hereinafter. For example, the air tunnel <NUM> is in fluid communication with the rotor <NUM> so as to transfer heat away from the power module <NUM> including the at least one MOSFET <NUM> that are attached to the chassis <NUM>.

With attention to <FIG>, the fan <NUM> can be disposed at the second end 28b on the shaft <NUM>. Additionally, the fan <NUM> is fluidicly disposed between the inlet portion 14b of the chassis <NUM> and the rotor <NUM> to aid in cooling of the MOSFETs <NUM> as will be described hereinafter. As the fan <NUM> is rotationally linked to the shaft <NUM>, rotation of the shaft <NUM> results in rotation of the fan <NUM>. The fan <NUM> can include at least one blade that is shaped in a manner so as so pull air thorough the air tunnel <NUM>. The direction of the airflow due to the fan <NUM> can be from the inlet portion 14b toward the main body portion 14a.

With reference to FIGS. <NUM>-<NUM>, the rotating machine <NUM> is shown. The chassis <NUM> includes an inner wall <NUM> that defines the air tunnel <NUM>. The inner wall <NUM> further defines a circular cross-section in a plane orthogonal to the rotation axis <NUM>. The chassis <NUM> also includes an outer wall <NUM> that is radially exterior to the inner wall <NUM>,.

The outer wall <NUM> defines a hexagonal cross-section in a plane orthogonal to the rotation axis <NUM>. The chassis <NUM> also includes at least one sidewall <NUM> that extends between the inner wall <NUM> and the outer wall <NUM> to define a sidewall height and to connect the inner wall <NUM> and the outer wall <NUM> together.

The chassis <NUM>, and more particularly, the sidewall <NUM> defines at least one cavity <NUM>. Even more particularly, the inner wall <NUM>, the outer wall <NUM>, and the sidewall <NUM> cooperate to define the cavity <NUM>. The cavity <NUM> is radially disposed between the air tunnel <NUM> and the cover <NUM>. The inner wall <NUM>, the outer wall <NUM>, and the at least one sidewall <NUM> are integral so as to prevent fluid communication between the air tunnel <NUM> and the at least one cavity <NUM>.

It is noted that the chassis <NUM> can be created by additive manufacturing, also known as 3D printing, so that the inner wall <NUM>, the outer wall <NUM>, and the sidewall <NUM>, and as will be discussed in more detail hereinafter, the ribs <NUM> and fins <NUM>, are integrally formed together. This allows for the better heat transfer and reduces the risk associated with a removable inner wall, outer wall, and/or sidewall.

The power module <NUM> including the at least one MOSFET <NUM> is radially disposed between the at least one cavity <NUM> and the cover <NUM>. For convenience, the cavity <NUM> will be described as a single object. However, there can be six or more cavities <NUM> radially disposed about the air tunnel <NUM> to sufficiently thermally manage the six or more circuit boards <NUM> and plurality of MOSFETs <NUM> disposed on each circuit board <NUM>. These cavities may be identical in structure to the cavity <NUM> described herein. As illustrated, these cavities are fluidicly isolated from one another.

A phase change material <NUM> is disposed in the cavity <NUM>. In fact, the phase change material <NUM> can fill all voids in the cavity <NUM>. The cavity <NUM> can include at least one sealable port <NUM> through which the phase change material <NUM> is introduced into the cavity <NUM> with the port <NUM> being subsequently sealed to prevent leakage of the phase change material <NUM> from the cavity <NUM>. The phase change material <NUM> can be a waxy solid that melts at <NUM> degrees Celsius and has a heat storage capacity of <NUM> joules per gram so that a heat of fusion associated with the melting of the phase change material <NUM> absorbs heat from the at least one MOSFET <NUM>.

At <NUM> degrees Celsius, the phase change material <NUM> will melt, and the heat of fusion associated with this melting transition will absorb much of the extra heat produced by the MOSFETs <NUM> while holding the phase change material <NUM> temperature at <NUM> until the melting is complete.

Using phase change material <NUM> allows for longer or more rigorous startup mode cycles with less mass than would otherwise be needed with a solid aluminum heat sink. It will be appreciated that different phase change materials could be used in place of the described phase change material <NUM> without departing from the scope of this disclosure.

With continued attention to <FIG>, the cavity <NUM> includes a plurality of ribs <NUM> that extend between the inner wall <NUM> and the outer wall <NUM> to connect the inner wall <NUM> and the outer wall <NUM> together to define a rib height. Further, the cavity <NUM> can include a plurality of fins <NUM> that extend from the inner wall <NUM> toward the rotation axis <NUM> so as to define a fin height.

This extension of the fins <NUM> toward the rotation axis <NUM> can be in a radial manner so that air can pass in between the individual fins <NUM> as the air travels through the air tunnel <NUM> toward the fan <NUM>. Further, the rib height can be greater than the fin height and less than the sidewall height. Further still, the plurality of fins <NUM> are in fluid communication with the air tunnel <NUM>, whereas the ribs <NUM> are not.

The ribs <NUM> define a plurality of channels <NUM> that are in fluid communication with one another and directly contact the phase change material <NUM> that is disposed within the cavity <NUM>. Each of the plurality of ribs <NUM> includes an attached end <NUM> that extends from the at least one sidewall <NUM> toward the stator <NUM> and a free end <NUM> that is opposite the attached end <NUM>. A space between the free end <NUM> of each of the plurality of ribs <NUM> and the at least one sidewall <NUM> allows for fluid communication between the plurality of channels <NUM>.

A purpose of the phase change material <NUM> in the chamber is for the starting mode of the rotating machine <NUM>, so that the MOSFETs <NUM> do not overheat. During generating mode of the rotating machine <NUM>, the motor is spinning at a normal RPM, so the rotating fan <NUM> is pulling air through the rotating machine <NUM>. That airflow allows the heat that is produced by the MOSFETs <NUM> during the generating mode to be dissipated into the moving air through the fins <NUM> that are in the airflow. However, this does not work for the starting mode for two reasons.

One reason is that because the rotating machine <NUM> is spinning slowly during the startup mode, the fan <NUM> is also slowly rotating, which means that there is little to no airflow going over these fins <NUM> to dissipate the heat generated by the MOSFETs <NUM>. Another reason is that the MOSFETs <NUM> are producing more heat during the starting mode than during the generating mode. During starting mode, as the MOSFETs <NUM> are producing more heat and as the rotating machine <NUM> cannot dissipate this heat as there is little to no airflow, the MOSFETs <NUM> have been shown to overheat for certain startup mode sequences if the described rotating machine assembly <NUM> is not utilized.

The rib <NUM> can have multiple functions. For example, one function of the ribs <NUM> is for the starting mode and one is for the generating mode, During starting mode, the ribs <NUM> provide a path for the heat to quickly get to the center of the phase change material <NUM>, because the phase change material <NUM> has a low thermal conductivity, Because of this low thermal conductivity, if the ribs <NUM> were not there, the outside of the phase change material <NUM> would melt and increase its temperature above <NUM> degrees Celsius while the center of the phase change material <NUM> would still remain solid.

This would not efficiently keep the MOSFETs <NUM> cool during the various startup mode sequences. As shown, the ribs <NUM> connect the inner wall <NUM> and the outer wall <NUM>. Thus, the ribs <NUM> can transmit the heat from the MOSFETs <NUM> into the center of the cavity <NUM>, and hence, the center of phase change material <NUM> during startup mode. If the ribs <NUM> were not connected to the outer wall <NUM>, then the heat may not be effectively transmitted to the cavity <NUM>, and hence, the center of the phase change material <NUM>.

During generating mode, as there is airflow, the ribs <NUM> conduct the heat from the MOSFETs <NUM> to the internal wall of the chassis <NUM> and then the heat is dissipated into the airflow. As the phase change material <NUM> has a low thermal conductivity, the heat practically bypasses the phase change material <NUM> as it flows almost entirely through the fins <NUM> in the air tunnel <NUM>.

This is why the ribs <NUM> are connected to both the outer wall <NUM> and the inner wall <NUM> of the cavity <NUM>. Notably, both of these connections ensure that the heat is transferred from the MOSFETs <NUM> through the ribs <NUM> to the fins <NUM> that are in the air tunnel <NUM>. If the ribs <NUM> were not connected to both the outer wall <NUM> and the inner wall <NUM> of the chamber, then the heat would not be transmitted from the MOSFETs <NUM> to the fins <NUM> in the air tunnel <NUM>.

As described hereinbefore, numerous advantages are provided by the chassis <NUM>. For example, the chassis <NUM> provides a mounting connection for the air inlet hose (not shown) from the aircraft, the air tunnel <NUM> to guide the air from the air hose inlet to the fan <NUM>, fins <NUM> in the air tunnel <NUM> to further aid in heat transfer, and because it is arranged tightly against the fan <NUM>, it can serve as the shroud 14a'. Notably, the fins <NUM> that are in the air tunnel <NUM> provide a way to dissipate the heat generated by the MOSFETs <NUM> during the generating mode of the rotating machine assembly <NUM>, but not during the starting mode.

The integrated shroud 14a' allows for more efficient airflow with an optimized fan <NUM> which again improves the cooling of the rotating machine <NUM>. Having all these functions integrated into one part (i.e., the chassis <NUM>) reduces complexity and part count and eliminates interface problems which could occur with multiple parts that perform the same functions. Having this as one part also makes it easier to optimize the airflow as there are no fasteners or part interfaces which might disrupt the airflow. As will be appreciated, this is extremely desirable an aircraft.

Claim 1:
A rotating machine assembly (<NUM>), comprising:
a rotating machine (<NUM>) including
a cover (<NUM>) that defines an outer surface (24a) of the rotating machine;
a stator (<NUM>) disposed within the cover, the stator being stationary with respect to the cover;
a shaft (<NUM>) rotatably disposed at least partially within the cover so as to define a rotation axis (<NUM>), the shaft including a first end (28a) that is connectable to an aircraft engine and a second end (28b) that is opposite the first end;
a rotor (<NUM>) attached to the shaft, the rotor being movable with respect to the stator;
a power module (<NUM>) including at least one MOSFET (<NUM>) that periodically reverses an electrical current direction of the rotor, wherein the power module including the at least one MOSFET is disposed within the cover; and
a chassis (<NUM>) at least partially disposed adjacent the second end of the shaft, wherein the power module including the at least one MOSFET is attached to the chassis and the chassis defines an air tunnel (<NUM>) in fluid communication with the rotor so as to transfer heat away from the at least one MOSFET, characterized in that
the chassis includes an inner wall (<NUM>) and an outer wall (<NUM>) that is radially exterior to the inner wall (<NUM>) and further includes at least one sidewall (<NUM>) that connects the inner wall (<NUM>) and the outer wall (<NUM>) together, the chassis (<NUM>) defining at least one cavity (<NUM>) radially disposed between the air tunnel and the cover, the at least one cavity including a phase change material (<NUM>) disposed therein, wherein the inner wall (<NUM>), the outer wall (<NUM>) and the sidewall (<NUM>) cooperate to define the at least one cavity and the at least one cavity includes a plurality of ribs (<NUM>) that directly contact the phase change material, the plurality of ribs defining a plurality of channels (<NUM>) that are in fluid communication with one another, wherein each of the plurality of ribs include an attached end (<NUM>) that extends from the at least one sidewall toward the stator and a free end (<NUM>) that is opposite the attached end, and wherein a space between the free end of each of the plurality of ribs and the at least one sidewall allows for fluid communication between the plurality of channels.