Patent Application
20080230024
The present invention relates to engine control and, more particularly, to camshaft position detection.
A camshaft actuates intake and exhaust valves of an internal combustion engine. In a dual overhead camshaft configuration, the engine includes an exhaust camshaft and an intake camshaft for each bank of cylinders. Rotation of the camshafts actuates the intake and exhaust valves. Position and timing between a crankshaft and the camshaft is critical for proper synchronization of spark and fuel.
An engine control system may include one or more camshaft phasing devices (cam phasers). For example, the cam phaser may create a continuously variable rotational offset between the exhaust camshaft and the intake camshaft and/or the crankshaft. Typically, cam phasers receive position and timing information from camshaft position sensors. The camshaft position sensor typically includes a variable reluctance or Hall Effect sensor that senses the passage of a tooth, tab, and/or slot on a target data wheel coupled to the camshaft.
The position sensor sends a signal to a control module. The control module develops an offset signal to control the cam phasers coupled to the camshafts. For example, the control module may be an engine control module. Alternatively, the control module may be a stand-alone controller or combined with other onboard controllers. The control module includes a processor and memory such as random access memory (RAM), read only memory (ROM) or other suitable electronic storage. Conventionally, internal combustion engines include one cam position sensor for each cam phaser. For example, in a dual-overhead cam arrangement, two cam position sensors are required to control the two cam phasers.
A camshaft (cam) phaser control system for an engine includes a first camshaft having a first target wheel. A second camshaft has a second target wheel. A cam position sensor detects said first and second target wheels and generates camshaft position data based on said first and second target wheels.
Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.
The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. As used herein, the term module refers to an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that execute one or more software or firmware programs, a combinational logic circuit, or any other suitable components that provide the described functionality. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements.
Referring now to
An intake valve 22 selectively opens and closes to enable the air/fuel mixture to enter the cylinder 18. The intake valve position is regulated by an intake camshaft 24. A piston (not shown) compresses the air/fuel mixture within the cylinder 18. A spark plug 26 initiates combustion of the air/fuel mixture, driving the piston in the cylinder 18. The piston drives a crankshaft (not shown) to produce drive torque. Combustion exhaust within the cylinder 18 is forced out an exhaust port when an exhaust valve 28 is in an open position. The exhaust valve position is regulated by an exhaust camshaft 30. The exhaust is treated in an exhaust system and is released to the atmosphere. Although single intake and exhaust valves 22, 28 are illustrated, it is appreciated that the engine 12 can include multiple intake and exhaust valves 22, 28 per cylinder 18.
The engine system 10 further includes an intake camshaft (cam) phaser 32 and an exhaust cam phaser 34 that respectively regulate the rotational timing and/or lift of the intake and exhaust camshafts 24, 30. More specifically, the timing of the intake and exhaust camshafts 24, 30 can be retarded or advanced with respect to each other or with respect to a location of the piston within the cylinder 18 or crankshaft position. The intake cam phaser 32 and the exhaust cam phaser 34 regulate the intake and exhaust cam shafts 24, 30 based on signals output from a cam position sensor 36. The cam position sensor 36 can include, but is not limited to, a variable reluctance or Hall Effect sensor. The cam position sensor 36 transmits output signals indicating rotational position of the intake or exhaust camshafts 24, 30 when the cam position sensor 36 senses the passage of a spaced position marker (e.g. tooth, tab, and/or slot) on a disc or target wheel (not shown) coupled to the intake or exhaust camshafts 24, 30.
A control module 40 operates the engine based on the engine cam phaser control system of the present invention. The control module 40 generates control signals to regulate engine components in response to engine operating conditions. The control module 40 generates a throttle control signal based on a position of an accelerator pedal (not shown) and a throttle position signal generated by a throttle position sensor (TPS) 42. A throttle actuator adjusts the throttle position based on the throttle control signal. The throttle actuator can include a motor or a stepper motor, which provides limited and/or coarse control of the throttle position. The control module 40 also regulates the fuel injection system 20 and the cam shaft phasers 32, 34. The control module 40 determines the positioning and timing (e.g. phase) between the intake or exhaust camshafts 24, 30 and the crankshaft based on the output of the cam position sensor 36 and other sensors.
An intake air temperature (IAT) sensor 44 is responsive to a temperature of the intake air flow and generates an intake air temperature signal. A mass airflow (MAF) sensor 46 is responsive to the mass of the intake air flow and generates a MAF signal. A manifold absolute pressure (MAP) sensor 48 is responsive to the pressure within the intake manifold 14 and generates a MAP signal. An engine coolant temperature sensor 50 is responsive to a coolant temperature and generates an engine temperature signal. An engine speed sensor 52 is responsive to a rotational speed of the engine 12 and generates an engine speed signal. Each of the signals generated by the sensors is received by the control module 40.
Referring now to
Referring now to
The cam position sensor 36 is located in a position to detect target wheel teeth 124, 126 on both of the target wheels 112, 114. The cam position sensor 36 transmits an output signal S3 to the control module 40 indicating that one of the teeth 124 or 126 has passed by the cam position sensor 36. The control module 40 generates offset signals S4-1 or S4-2 based in part on the output signal S3. The cam phasers 32, 34 rotationally offset the camshafts 24, 30 relative to the crankshaft based on receiving the offset signals S4-1, S4-2, respectively.
The present implementation includes the cam position sensor 36 positioned adjacent to both the cam position target wheels 112, 114. Several configurations are contemplated to achieve the positional relationship of cam position sensor 36 relative to the cam position target wheels 112, 114 including, but not limited to, positioning the camshafts 24, 30 in close proximity, increasing the diameter of the cam position target wheels 112, 114, and/or increasing the size of the cam position sensor 36. The cam position sensor 36 uses a magnetic field to generate the output signal S3. As the target wheel teeth 124, 126 of the cam position target wheels 112, 114 pass the cam position sensor 36, the target wheel teeth 124, 126 cause a disturbance in the magnetic field. The cam position sensor 36 generates the output signal S3 based on the disturbance in the magnetic field.
In various embodiments, the cam phaser control system may include a flux deflector (not shown). The flux deflector includes a magnetically conductive metal (e.g. steel) that redirects the magnetic field of the cam position sensor 36.
In various embodiments, each of the cam position target wheels 112, 114 may include a plurality of the target wheel teeth 124, 126, respectively. In the present implementation, the cam position sensor 36 detects a single tooth 124, 126 of one of the cam position target wheels 112, 114 at an instance in time. In the present implementation, positioning of the cam position target wheels 112, 114 allows for one of the target wheel teeth 124, 126 to be in a detectable proximity to the cam position sensor 36 at the instance in time. The cam position sensor 36 may be positioned to detect the cam position target wheels 112,114 in either the axial or radial direction.
Referring now to
Referring now to
In the present implementation, each of the cam position target wheels 112, 114 possess distinct teeth, tabs, and/or slots of various sizes. In other words, the intake cam position target wheel 112 possess target wheel teeth 124 that are sized differently than the target wheel teeth 126 of the exhaust cam position target wheel 114. Consequently, a pulse width corresponding to a difference between the time t1 and time t2 (e.g. PW1) varies from a pulse width corresponding to a difference between a time t3 and a time t4 (e.g. PW2). The PW1 and PW2 represent periods of time (i.e. detection periods) that the teeth 124, 126, respectively, are detected by the cam position sensor 36. The control module 40 can determine whether the cam position target wheel 112 or 114 has passed the position sensor 36 based on known values or PW1 or PW2, respectively. The control module 40 then generates optimum offset values for the cam phasers 32, 34 based on PW1, PW2, respectively.
In various embodiments, the control module 40 may determine whether the cam position target wheel 112 or 114 has passed the cam position sensor 36 by comparing a detection period to a time threshold. For example, if the detection period exceeds the time threshold, the control module 40 may determine that the cam position target wheel 114 passed the cam position sensor 36. However, if the detection period falls below the time threshold, the control module 40 may determine that the cam position target wheel 112 passed the cam position sensor 36.
Referring now to
In step 508, the control module 40 stores a first time corresponding to the rise in the output signal Vs in memory (e.g. non-volatile memory). In step 510, the cam position sensor 36 drops the output voltage Vs to a low voltage level when the trailing edge 124b or 126b associated with the detected leading edge in step 502 is detected by the cam position sensor 36. In step 512, the control module 40 stores a second time corresponding to the drop in the output voltage Vs. In step 514, the control module 40 determines the identity of the detected target wheel e.g. target wheel 112 or 114) based on a time difference (e.g. PW1 or PW2) between the second time and the first time. In step 516, the control module 40 generates an offset signal (e.g. the offset signal S4-1 or S4-2) based on the time difference.
In step 518, the control module 40 transmits the offset signal to either the cam phaser 32 or 34 corresponding to the detected leading and trailing edges. In step 520, the cam phaser 32 or 34 adjusts the angular offset between the intake camshaft 24 or exhaust camshaft 30, respectively, and the crankshaft. In step 522, the method 500 ends.
Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the present disclosure can be implemented in a variety of forms. Therefore, while this disclosure has been described in connection with particular examples thereof, the true scope of the disclosure should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, the specification and the following claims.
