Patent Application
20150069868
The subject matter disclosed herein relates generally to the design and operation of combustion engines for powered equipment. More particularly, the subject matter disclosed herein relates to the design and operation of an engine flywheel of a combustion engine.
Many combustion engines for small powered equipment include an engine flywheel to moderate speed fluctuations in the engine. Specifically, the flywheel can be designed to be able to develop an inertia large enough such that quick spurts by the engine or sudden loads (e.g., a lawnmower hitting a clump of weeds) are evened out. Because of this large inertia, however, it can be difficult to quickly slow and/or stop the operation of the engine because of the time needed to dissipate the energy stored in the flywheel. To speed this slowdown, in particular to meet regulations regarding maximum stopping times (e.g., blade stop time for a lawnmower), a brake can be configured to act directly on the engine flywheel to actively dissipate the stored energy. In such systems, the energy of the spinning flywheel is generally lost (e.g., dissipated as heat) upon braking.
In some contrasting configurations, such as portable generators and alternators for some small motor vehicle engines (e.g., motorcycles, scooters), similarly-structured combustion engines can provide high power generation from the rotation of a rotor/flywheel by converting the mechanical energy of the flywheel into electrical energy. Further, because these engine-generators generally don't have any need to stop quickly, these systems generally don't rely on a brake mechanism to slow the operation of the engine, and thus much of the energy stored in the flywheel can be effectively recaptured as electrical power over time.
Although the powered equipment and dedicated engine-generators are designed to serve much different purposes, it would be desirable for advantageous aspects of both types of systems to be integrated together. For example, in a lawnmower, instead of dissipating all of the energy stored in the flywheel during braking, it would be advantageous to recapture at least some of that stored energy and convert it to electricity in a manner similar to an engine-generator. It is undesirable, however, to apply a brake to the component to which magnets are mounted for power generation because the braking can cause heat to build up, the component to deflect, and any adhesives to be stressed. These factors can diminish the ability of the electrical generation components of the system to operate as intended, and such factors can further cause the electrical generation system to fail prematurely.
As a result, it would be desirable for an engine flywheel to be able to integrate electric power generation with rapid engine braking without each of the two operations impeding the operation of the other.
In accordance with this disclosure, systems and methods for using an engine flywheel both for electric power output and for braking of powered equipment are provided. In one aspect, an engine flywheel is provided. The engine flywheel can include a first rotor element configured to be coupled to a drive shaft for rotation with the drive shaft, one or more magnets carried by the first rotor element, the one or more magnets being configured for positioning with respect to a stator to generate electrical current upon rotation of the first rotor element, and a second rotor element configured to be coupled to the drive shaft for rotation with the drive shaft, the second rotor element comprising a braking surface configured for engagement with a braking element to slow the rotation of the second rotor element.
In another aspect, a combined electric generation and engine braking system can include a drive shaft rotatable about a center axis, a first rotor element coupled to the drive shaft for rotation with the drive shaft, one or more magnets carried by the first rotor element, a stator positioned at or near the first rotor element and configured to generate electrical current upon rotation of the first rotor element, a second rotor element coupled to the drive shaft for rotation with the drive shaft, the second rotor element comprising a braking surface, and a braking element positioned at or near the second rotor element and configured to selectively engage the braking surface of the second rotor element to slow the rotation of the second rotor element.
In yet another aspect, a method for electric generation and engine braking is provided. The method can include rotating a flywheel assembly about a center axis of a drive shaft connected to the flywheel assembly, the flywheel assembly comprising a first rotor element coupled to the drive shaft, one or more magnets carried by the first rotor element, and a second rotor element comprising a braking surface. For example, rotating the flywheel assembly about the center axis of the drive shaft can involve rotating the one or more magnets past a stator positioned at or near the first rotor element to generate electrical current. The method can further include a step of selectively engaging a braking element with the braking surface of the second rotor element to slow the rotation of the flywheel assembly.
Although some of the aspects of the subject matter disclosed herein have been stated hereinabove, and which are achieved in whole or in part by the presently disclosed subject matter, other aspects will become evident as the description proceeds when taken in connection with the accompanying drawings as best described hereinbelow.
The features and advantages of the present subject matter will be more readily understood from the following detailed description which should be read in conjunction with the accompanying drawings that are given merely by way of explanatory and non-limiting example, and in which:
The present subject matter provides systems, devices, and methods for using an engine flywheel both for electric power output and for braking of powered equipment. In one aspect, the present subject matter provides an engine flywheel that does not suffer from the drawbacks discussed above that can be associated with combining electrical generation and braking into a single component.
Specifically, referring to
Similarly, second rotor element 140 can include a second disc portion 141 configured for positioning about drive shaft DS (e.g., coupled to drive shaft DS by way of hub portion 110) and a second ring portion 142 extending from an outer edge of second disc portion 141. As shown in
Alternatively, as shown in
In any configuration, the division of engine flywheel 100 into multiple rotor elements (e.g., first rotor element 120 and second rotor element 140) can allow the different elements to serve different functions. Specifically, for example, first rotor element 120 can be configured to be a component of an electrical generation system. In this regard, first rotor element 120 can include a mounting surface 123 to which one or more magnets 125 can be attached. For example, as shown in
In contrast, second rotor element 140 can be configured to be a component in an engine braking system. In this regard, second rotor element 140 can include a braking surface 143 configured for engagement with a braking element 150 to slow the rotation of second rotor element 140 (and thereby to correspondingly slow the rotation of engine flywheel 100). For example, as shown in
Those having skill in the art should recognize that isolating the electrical generation function and the braking function to the first rotor element 120 and the second rotor element 140, respectively, can be helpful to avert the problems that can result from both functions being applied to the same component. Specifically, because braking surface 143 can be positioned away from mounting surface 123 to which the one or more magnets 125 can be coupled, it can be less likely that braking will cause heat to build up at mounting surface 123 since first ring portion 122 can be separated from second ring portion 142 by an air gap. In addition, first ring portion 122 can be shielded from any deflection caused by engagement of braking element 150, and it will thereby be less likely that any stresses be developed on the adhesives used to mount the one or more magnets 125 to mounting surface 123. As a result, it is believed that the systems, devices, and methods described herein can be effectively used both for electric power output and for braking of powered equipment.
The present subject matter can be embodied in other forms without departure from the spirit and essential characteristics thereof. The embodiments described therefore are to be considered in all respects as illustrative and not restrictive. Although the present subject matter has been described in terms of certain preferred embodiments, other embodiments that are apparent to those of ordinary skill in the art are also within the scope of the present subject matter.
