BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:
FIG. 1 is a functional block diagram of a vehicle including an automatic clutch-to-clutch transmission and an internal mode switch;
FIG. 2 is a diagram illustrating the placement of conductive tracks in an internal mode switch according to the present invention;
FIG. 3 is a table illustrating the bit patterns for valid, transitional, and illegal states according to the present invention;
FIG. 4 is a table illustrating the bit patterns for positive range states according to the present invention; and
FIG. 5 is a table illustrating the bit patterns and fault detection method according to the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements. 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 executes one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality.
Referring now to FIG. 1, a vehicle is shown generally at 10. The vehicle includes an engine 12 that drives a transmission 14 through a torque converter 16. Air is drawn into the engine 12 through a throttle 18. The air is mixed with fuel and combusted within cylinders (not shown) of the engine 12 to produce drive torque. The torque converter 16 supplies the engine torque to the transmission via an input shaft 20. The transmission 14 in the exemplary embodiment is a multi-speed automatic clutch-to-clutch transmission that drives an output shaft 22 based on engine torque.
The output shaft 22 drives a driveline 24 of the vehicle 10. The speed and torque relationships between the engine 12 and the driveline 24 are controlled by hydraulically operated clutches C1, C2, C3, C4, and C5 of the transmission 14. Pressurized fluid is provided to the clutches from a regulated hydraulic pressure source 28. The clutches C1, C2, C3, C4, and C5 are coupled to the hydraulic pressure source via control valves 30, which regulate clutch pressure by supplying or discharging fluid to/from the clutches C1, C2, C3, C4, and C5.
A range selection device 26 enables an operator to set the transmission 14 at a desired operating range including, but not limited to, park, reverse, neutral, and one or more forward drive positions. The range selection device 26 is connected to an internal mode switch 27. An internal mode switch 27 generates mode signals. The mode signals indicate a bit encoding corresponding to states of four circuits of the internal mode switch 27. As can be appreciated, the internal mode switch 27 can include any number (N) of circuits and the mode signals can indicate a bit encoding corresponding to states for N circuits of the internal mode switch 27. A control module 40 receives the mode signals and interprets the mode signals as an IMS state according to a bit pattern of the present invention. The IMS state can be a transitional state, a range state, and an illegal state. Based on the interpreted IMS state, the control module determines the intended range and controls engine operation and transmission shift patterns based on the range. Further, the control module 40 can detect a fault in the switch 27 based on the bit pattern.
Referring now to FIG. 2, the diagram illustrates an exemplary placement of conductive tracks in an IMS 27 such that a bit pattern according to the present invention can be produced. Horizontal lines of the diagram correspond to tracks A, B, C, and P. The placement of conductive tracks is illustrated by darkened lines 50-80. Vertical lines of the diagram correspond to positive IMS states: park, reverse, neutral, drive 6, drive 4, drive 3, and drive 2. The area between the positive IMS states is considered transitional states. Placement of the conductive tracks 50-80 should be such that all circuits are closed when the IMS 27 is in a transitional state. In the alternative (not shown), placement of the conductive tracks can be such that all circuits are open when the IMS 27 is in a transitional state.
Referring now to FIG. 3, a table illustrates bit patterns and their mapping to an IMS state according to the present invention. Each bit pattern includes bits A, B, C, and P which correspond to circuit A, circuit B, circuit C, and circuit P of the IMS respectively. The bit 0 indicates the circuit is closed to common. The bit 1 indicates the circuit is open to common. In an alternative embodiment, the bits can be inverted. In column 100, bit patterns are shown in ABCP format. In column 110, an IMS state that corresponds to the bit pattern is shown. IMS states can be, transitional, illegal, park, neutral, reverse, D2, D3, D4, and D6. According to the bit pattern mapping, a single transitional state is created between all positive IMS states. Thus creating eight (8) illegal bit patterns for diagnosing single point failures. The table of FIG. 4 illustrates the bit patterns that correspond to operating ranges of the transmission as requested by the operator via the range selection device. The controller determines the range based on these bit patterns.
Referring now to FIG. 5, a chart illustrates all single point failures that can be diagnosed with the bit pattern containing four bits. Column 200 lists the single point failures that can occur for circuits A, B, C and P where each circuit is either open or shorted. Row 210 lists the mechanical positions of the IMS. Mechanical positions can be: positive range states including park, reverse, neutral, drive 6, driver 4, drive 3, drive 2, and transitional states including park to reverse, reverse to neutral, neutral to drive 6, drive 6 to drive 4, drive 4 to drive 3, and drive 3 to drive 2. Shaded cells, for example cell 220, indicate failures that can be diagnosed given the current bit pattern. As can be appreciated, an IMS 27 with more or fewer tracks can similarly diagnose single point failures, so long as the bit pattern includes a single transitional state between each positive range state.
Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the present invention can be implemented in a variety of forms. Therefore, while this invention has been described in connection with particular examples thereof, the true scope of the invention should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, specification, and the following claims.
Patent Application
20080065299
