Patent Application
20150330295
This invention relates to engine accessories, and more particularly controlling superchargers and other belt-driven engine accessories.
In an internal combustion engine, air boosting devices such as turbochargers and superchargers are used for forced induction of air into the engine. They compress the air flowing into the engine, which allows the engine to deliver more air into a cylinder. This in turn, allows the cylinder to receive more fuel, and the increases air and fuel results in more power from each combustion event in the cylinder.
A turbocharger is powered by a turbine, which is driven by the engine's exhaust. A supercharger is powered mechanically by belt-drive or chain-drive from the engine's crankshaft. For example, a supercharger can be driven by an accessory belt, which wraps around a pulley that is connected to a drive gear. The drive gear, in turn, rotates the compressor gear. A rotor draws air in, compresses the air into a smaller space and discharges it into the intake manifold.
Other engine accessories can also be driven by an engine's front accessory belt. Examples of these devices are alternators, water pumps, cooling fan, air conditioning compressors, and power steering pumps.
A more complete understanding of the present embodiments and advantages thereof may be acquired by referring to the following description taken in conjunction with the accompanying drawings, in which like reference numbers indicate like features, and wherein:
The following invention is directed to coupling a planetary gear set with an electric generator for the purpose of controlling a supercharger or other “belt-driven” accessory of an engine. Typical applications are expected to be for automotive vehicles having internal combustion engines, motors, or hybrid systems. The term “engine” is used herein in a broad sense to include various machines capable of rotating a belt to drive an accessory device. Examples of “accessory devices” are water pumps, radiator fans, alternators, superchargers and other air boosting devices, power steering pumps, and air conditioning compressors. In further embodiments, the planetary gear set may be coupled with both an electric generator and an electric motor.
In today's vehicles, these accessories are driven by the engine's “front belt”, which may be also referred to as an “accessory belt”, “serpentine belt” or “fan belt”. These terms refer to various belts that wind around the engine's crankshaft pulley and one or more additional pulleys. As the engine's crankshaft turns, the belt drives one or more of the above-described engine accessories. In some vehicles, different belts drive different accessories. In other vehicles, a single serpentine belt winds around to drive multiple accessories.
As explained below, the planetary gear set, coupled to a generator, is used in a manner that provides continuously variable operating speeds for the engine accessory. More specifically, the generator is activated with a variable current (excitation current), which in turn varies the speed ratio of the planetary gear set. The planetary gear set thereby operates as a continuously variable transmission that controls the input speed of the accessory.
For purposes of example, this description is in terms of a belt-driven supercharger 14. Thus, belt 11 is connected to a pulley 12 associated with the supercharger 14. The supercharger's pulley 12 is connected to a planetary gear set 13, which transmits the driving force of the belt to the supercharger 14. The supercharger 14 is thereby powered, and delivers compressed air to the combustion chambers of the engine cylinders.
Supercharger 14 may be any one of various types of superchargers, and in the example of this description, is a roots type supercharger. Examples of other types of superchargers are centrifugal and turn screw superchargers.
The planetary gear set 13 is interposed between the pulley 12 and the supercharger 14. As explained herein, planetary gear set 13 provides continuously variable control of the engine-to-supercharger speed ratio. The operating speed of the supercharger 14 can be controlled by controlling the planetary gear set 13. The drive speed of the supercharger is independent of the engine speed.
However, as indicated above, it should be understood that the same concepts apply to controlling the operating speed of other belt-driven engine accessories. For other accessories, the planetary gear set 13 would be interposed between that accessory and the pulley associated with that accessory.
Not referring to
To eliminate the bypass losses of fixed gear superchargers, efforts have been made to modify the supercharger-to-belt connection with some sort of variable transmissions. For example, one approach is to directly vary the pulley ratio of the supercharger pulley.
Referring again to
The basic components of a planetary gear set are a central sun gear 32, a planet carrier 31 and its planet gear(s) 31a, and an annulus (ring) gear 33. The planet carrier 31 holds one or more planet gears 31a, which are peripheral to and meshed with the sun gear 32. The annulus (ring) gear 33 is an outer ring with inward-facing teeth that mesh with the planet gear(s) 31a.
In operation, the carrier 31 rotates to carry the planet gear(s) 31a around the sun gear 32. The ring (outer) gear 33 meshes with the planet gear(s). The planet and sun gears mesh so that their pitch circles roll without slip.
In the configuration of
Thus, input rotation from the engine is provided to the planetary gear carrier 31. Output rotation to the supercharger 14 is produced from the sun gear 31. As explained below, gear speed ratio control is provided by using generator 36 to load the ring gear 33.
Generator 36 is of the type that receives an excitation current. The speed ratio of the engine 10 to supercharger 14 can be continuously varied by controlling the excitation current to the generator 36. The variation in excitation current causes variation in the gear speed ratio of the planetary gear set. The amount of variation depends on the layout of the planetary gear set 13, but an example of a range of gear speed ratios is 0:1 to 10:1.
Generator 36 controls the rotational speed of the ring gear 33. If no excitation is applied to the generator 36, the ring gear 33 is not loaded and rotates in response to the rotation of the carrier via the planetary gears. The sun gear, which is connected to the input shaft of the supercharger is at or near a standstill. However, if an excitation current is applied to the generator, the ring gear 33 slows causing rotational speed and power from the planet gear carrier to be transferred to the sun gear. This causes the sun gear and supercharger to rotate. By modulating the excitation of the generator 36, the speed of the ring gear and, thus, the speed of the sun gear 32 and supercharger 14 can be controlled proportionally to the amount of excitation current applied to the generator 36.
The same concepts apply to accessories other than a supercharger. The sun gear 32 is attached to a drive shaft or similar input mechanism of the accessory. Operating speed control of these accessories can be controlled by controlling the excitation current to the generator 36.
Referring again to
The inputs to control unit 38 depends on the accessory being controlled. For controlling a supercharger, the inputs typically include engine operating conditions, such as engine load. In general, the lower the engine load, the less boost air is required, and the slower the operating speed of the supercharger. Other inputs for other accessories might include passenger input for air conditioning, engine temperature for a fan or water pump, etc. These inputs are collectively and generally referred to herein as “engine operating conditions”.
To exploit the electrical energy provided by the generator, a small electric motor can be connected to the supercharger (via the sun gear) to assist in driving the supercharger (or other accessory). In
The motor, solely powered by the generator, reduces the reaction load from the accessory and minimizes the size required for the motor/generator combination 41. The power supplied to the accessory by the motor, by reducing the reaction load through the planetary gear set, results in reduced power requirements from the generator on the ring gear. Additionally, the use of a motor ensures that the generated power from the generator can be consumed.
Referring again to
