In conventional aircraft engines, engine controllers, such as full authority digital engine controllers (FADECs), control certain operating characteristics of the engines to enhance the engines' performance. For example, FADECs typically include a digital computer, known as an electronic engine control unit (ECU) and a variety of sensors that measure, for example, various environmental and engine conditions such as engine temperature, engine fluid pressures, air temperature, and air density. During operation of the engine, the ECU receives data signals from the sensors and calculates engine operating parameters based upon the data signals. Based upon the engine operating parameters, the FADEC controls certain engine components, such as the engine's fuel injection system and ignition timing, to adjust the engine's fuel usage and optimize the engine's performance.
For example, as each aircraft engine cylinder assembly receives a fuel and air mixture, a spark plug associated with each aircraft engine cylinder assembly ignites the fuel and air mixture. Under normal operating conditions, the spark plug initiates combustion of the fuel and air mixture when an associated crankshaft positions a piston of the cylinder assembly within about 15 to 40 degrees before a top dead center (TDC) position, the point of maximum compression of the fuel and air mixture. Ignition of the fuel and air mixture at a time prior to the piston reaching the TDC position maximizes the pressure required to displace the piston within a cylinder assembly housing to drive the crankshaft.
In order to cause or adjust the ignition of the fuel and air mixture at a time before the piston reaches a TDC position, the ECU must identify the rotational position or angle of the crankshaft along with the crankshaft's angular velocity. Accordingly, conventional aircraft engines utilize a detection system to detect the positioning and speed of the crankshaft. For example, in a conventional aircraft engine, the crankshaft includes a gear reduction assembly located at a rear portion of engine (i.e., the portion opposing the propeller) and a sensor positioned in proximity to the gear reduction assembly. The gear reduction assembly turns at a rate that is half of the angular velocity of the crankshaft. Accordingly, the sensor detects the half-rate rotation of the gear reduction assembly and provides an output signal, indicative of the crankshaft position and angular velocity, to the ECU. The ECU utilizes the output signal to approximate the position of each cylinder within each cylinder assembly and to adjust the spark timing for the cylinder.
The use of conventional detection systems to detect the rotational position or and angular velocity of the crankshaft suffers from a variety of deficiencies. For example, when using a sensor to measure the half-rate rotation of the gear reduction assembly the output from the sensor is a relatively low-resolution output. Accordingly, the sensor provides the ECU with a relatively imprecise indication of the angular positioning and velocity of the crankshaft. This imprecision can compromise the ability for the ECU to detect the position of each cylinder within each cylinder assembly and to adjust the spark timing for the cylinder assembly accordingly. Furthermore, space limitations around the rear portion of conventional aircraft engines can limit the ability to position one or more sensors around the gear reduction assembly and thus inhibit the ability to obtain not only accurate but redundant readings of aircraft engine crankshaft position and angular velocity.
By contrast, embodiments of the present invention provide an aircraft engine crankshaft detection system. The crankshaft detection system includes a pickup element mounted to an end of a crankshaft and disposed within a rear portion of the aircraft engine's crankcase. The crankshaft detection system also includes pickup element sensor secured to a mounting location formed in the rear portion of the aircraft engine's crankcase and disposed in proximity to the pickup element. As the crankshaft rotates the pickup element relative to the pickup element sensor, the pickup element causes the pickup element sensor to generate a signal indicative of the angular velocity and rotational position of the crankshaft. A controller, such as a FADEC, receives the signal and detects a position of each piston in each cylinder assembly of the aircraft engine based upon the signal. In order to optimize engine performance, the controller controls a spark event associated with each the cylinder assembly of the engine such that ignition of the fuel and air mixture occurs within each cylinder assembly at a time prior to each piston of each cylinder assembly reaching a top dead center position.
In one arrangement, an aircraft engine assembly includes a crankcase assembly and a detection system. The crankcase assembly includes a crankcase housing and a crankshaft disposed within the crankcase housing. The crankshaft has a first end disposed in proximity to a propeller-mounting portion of the aircraft engine assembly and a second end disposed in proximity to a rear portion of the aircraft engine assembly where the second end opposes the first end. The detection system includes a pickup element mounted to the second end of the crankshaft, the pickup element operable to rotate at the angular velocity as the crankshaft. The detection system also includes a pickup element sensor disposed in proximity to the pickup element. The pickup element sensor is operable to generate a pickup element signal in response to rotation of the pickup element relative to the pickup element sensor. The pickup element signal indicates an angular velocity of the crankshaft and a rotational position of the crankshaft within the crankcase housing. A controller utilizes the pickup element signal to control spark timing of the cylinder assemblies of the aircraft engine.
In one arrangement, a crankshaft detection system for an aircraft engine includes a pickup element mounted to an end of a crankshaft and a pickup element sensor disposed in proximity to the pickup element. The end of the crankshaft is disposed in proximity to a rear portion of the aircraft engine and opposes a propeller-mounting portion of the aircraft engine. The pickup element is operable to rotate at the angular velocity as the crankshaft. The pickup element sensor is operable to generate a pickup element signal in response to rotation of the pickup element relative to the pickup element sensor. The pickup element signal indicates an angular velocity of the crankshaft and a rotational position of the crankshaft within a crankcase housing.
The foregoing and other objects, features and advantages will be apparent from the following description of particular embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of various embodiments of the invention.
Embodiments of the present invention provide an aircraft engine crankshaft detection system. The crankshaft detection system includes a pickup element mounted to an end of a crankshaft and disposed within a rear portion of the aircraft engine's crankcase. The crankshaft detection system also includes pickup element sensor secured to a mounting location formed in the rear portion of the aircraft engine's crankcase and disposed in proximity to the pickup element. As the crankshaft rotates the pickup element relative to the pickup element sensor, the pickup element causes the pickup element sensor to generate a signal indicative of the angular velocity and rotational position of the crankshaft. A controller, such as a FADEC, receives the signal and detects a position of each piston in each cylinder assembly of the aircraft engine based upon the signal. In order to optimize engine performance, the controller controls a spark event associated with each the cylinder assembly of the engine such that ignition of the fuel and air mixture occurs within each cylinder assembly at a time prior to each piston of each cylinder assembly reaching a top dead center position.
The fuel delivery system 18 is configured to provide fuel from a fuel source to each of the cylinder assemblies 16. The fuel delivery system 18 includes a fuel pump (not shown), fuel rails 26-1, 26-2, and fuel injectors 28 configured to provide fuel from a fuel source to each of the cylinder assemblies 16. In use, each cylinder assembly 16 receives fuel via the fuel delivery system 18. The primary spark plug 22 ignites a fuel air mixture contained within each cylinder housing 20 thereby causing the piston and connecting rod disposed within each cylinder housing 20 to reciprocate therein. The reciprocating motion of the piston and connecting rod rotates the crankshaft which, in turn, rotates other components associated with the aircraft engine 10.
The aircraft engine control system 12 is configured to control the performance of the aircraft engine 10 during operation. While the engine controller 12 can be configured in a variety of ways, in one arrangement the engine controller 12 is configured as a Full Authority Digital Engine Controller (FADEC). The FADEC 32 includes a variety of sensors that measure various environmental and engine conditions such as engine temperature, engine fluid pressures, air temperature, and air density. The FADEC 32 also includes an electronic engine control unit (ECU) 34, such as a processor and a memory, which receives various data signals from the sensors and calculates engine operating parameters based upon the data signals. Based upon the engine operating parameters, the FADEC 32 optimizes the performance of the aircraft engine 10 by adjusting the aircraft engine's fuel metering system to control the flow of fuel to the cylinder assemblies 16, and optimizes spark timing.
While the aircraft engine 10 can include a variety of devices to measure various operating parameters associated with the aircraft engine 10 and to provide representative data signals to the engine controller 12, in one arrangement, the aircraft engine 10 also includes a crankshaft detection system 30, as illustrated in
As indicated in
The pickup element sensor 56 is configured to detect rotation of the pickup element 54, generate a pickup element signal in response to rotation of the pickup element 54, and to transmit the pickup element signal to the ECU 34. As indicated in
A variety of types of sensors can be utilized as the pickup element sensor 56. In one arrangement, the pickup element sensor 56 is configured as a variable reluctance sensor having a magnetic pole and a wire coil wrapped about the pole. As will be described in detail below, the variable reluctance sensor operates in conjunction with the pickup element 54 to generate the pickup element signal for transmission to the ECU 34.
The crankshaft 80 extends along the length of the crankcase housing 14 from the front portion 42 of the engine 10 to the rear portion of the engine 10. With particular reference to
As shown in
As the ECU 34 receives the pickup element signal 69 from the pickup element sensor 56, the ECU 34 examines the pickup element signal 69 to detect the angular velocity and the rotational positioning of the crankshaft 80. For example, each small pulse 70 corresponds to a pass of one of the trigger teeth 61 past the pickup element sensor 56 and the elongated pulse 72 corresponds to a pass of the indicator teeth 63-1, 63-2 past the pickup element sensor 56. As a result, based on the number of small pulses 70 away from the last elongated pulse 72 the ECU 34 had received, the ECU 34 can detect the current rotational position of the crankshaft 80 within the crankcase 14. Additionally, based upon the number of elongated pulses 72 detected in a particular period of time, the ECU 34 can detect the angular velocity of the crankshaft 80.
The rotational position of the crankshaft 80 and the angular velocity of the crankshaft 80 provide to the ECU 34 an indication of a position of each piston in each cylinder assembly 16, relative to a TDC position. Accordingly, based on the pickup element signal 69, the ECU 34 controls a spark event associated with the cylinder assemblies 16 such that ignition of the fuel and air mixture within each cylinder assembly 16 occurs at a time prior to each respective piston reaching a TDC position, thereby optimizing engine performance.
While the pickup element 54 and the pickup element sensor 56 can be arranged in a variety of ways, in one arrangement the pickup element 54 and pickup element sensor 56 are oriented relative to each other to minimize measurement imprecision caused by lateral translation or wavering 82 of the end of the crankshaft 80. For example, as illustrated in
As indicated above, the first detection assembly 50 provides a pickup element signal to the controller 12. Based upon the pickup element signal, the controller 12 detects the position of the pistons within the cylinder assembly housings. However, as indicated above, the engine 10 is a four-stroke engine. In a four-stroke engine, during operation, the piston approaches a TDC position twice during an operational cycle of the engine 10: once during a compression stroke when the piston compresses the fluid and air mixture within the cylinder assembly 16 and once during an exhaust stroke as the piston causes the gaseous byproduct of the combusted fuel and air mixture to be exhausted from the cylinder assembly 16. Accordingly, with the above described crankshaft detection assembly 50, the controller 12 controls a spark event associated the cylinder assemblies 16 such that the spark event occurs at a time prior to each respective piston reaching a TDC position, both during the compression stroke and during the exhaust stroke. However, the spark event occurring during the exhaust stroke is unnecessary.
During the operation of the engine 10, rotation of a camshaft controls the position of the intake and exhaust valves. Accordingly, the rotational position of the camshaft within the aircraft engine 10 indicates where each cylinder assembly is in the engine's firing process. For example, with reference to
With reference to
The camshaft gear sensor 92 is configured to detect rotation of the camshaft gear 90, generate a camshaft gear signal in response to rotation of the pickup element 54, and to transmit the camshaft gear signal to the ECU 34. As indicated in
With reference to
As illustrated in
While various embodiments of the invention have been particularly shown and described, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
For example, as described above, in one arrangement, the crankshaft detection system 30 includes a camshaft detection assembly 52 that detects the rotational position of the camshaft within the crankcase housing 14. As such, the camshaft detection assembly 52 provides a camshaft gear signal to the controller 12 indicative of the rotational position of the camshaft. Such description is by way of example only. In one arrangement, with reference to
For example, the camshaft gear 90′ includes a base 97′ and rotation indicators 98′, such as a series of openings formed through the camshaft gear 90′. As shown in
As the ECU 34 receives the camshaft gear signal 160 from the camshaft gear sensor 92, the ECU 34 examines the camshaft gear signal 160 to detect the angular velocity of the crankshaft 80 and the rotational positioning of the camshaft 150. For example, each small pulse 170 corresponds to a pass of one of the trigger openings 152 past the camshaft gear sensor 92 and the elongated pulse 172 corresponds to a pass of the indicator openings 154-1, 154-2 past the camshaft gear sensor 92. As a result, based on the number of small pulses 170 away from the last elongated pulse 172 the ECU 34 had received, the ECU 34 can detect the current rotational position of the camshaft 150, indicative of relative positions of the pistons within their respective cylinder assemblies. Additionally, based upon the number of elongated pulses 172 detected in a particular period of time, the ECU 34 can detect the angular velocity of the crankshaft 80. The camshaft gear 90′ and camshaft gear sensor 92, therefore, provide information about the angular velocity of the crankshaft 80 and the rotational positioning of the camshaft 150 independent from the information provided by the pickup element 54 and the pickup element sensor 56. Accordingly, in this arrangement, the camshaft gear 90′ and camshaft gear sensor 92 can operate either independently from, or as a redundant back-up to, the pickup element 54 and a pickup element sensor 56.