Patent Application
20070105691
The invention relates generally to a method of operating an electronic control unit of an automated mechanical transmission and more particularly to a method which simulates and provides a control signal indicating throttle kickdown.
In virtually all vehicles equipped with automatic transmissions, the action by the vehicle operator of depressing the accelerator pedal to the floor is interpreted by either the mechanical or electronic controls of the prime mover and transmission as a “kickdown” or “kickdown shift”: a desire to increase the speed and power of the prime mover and engage a lower gear in order to pass another vehicle or climb a grade. Depending upon the type of vehicle and transmission, such systems typically include mechanical linkages to the fuel or other engine systems and the transmission in the case of full mechanical systems and position sensors or switches wherein control of the engine and transmission are achieved through electronic, i.e., computer and software means in, for example, drive by wire systems.
In the latter case, switches activated by fully or substantially fully depressed accelerator or throttle pedals may be prone to failure but certainly require additional materials, wiring, engineering and design. Elimination of an on/off throttle position sensor therefore represents a reduction in engineering and component costs as well as an improvement in reliability.
A method of operating an automated mechanical transmission includes a throttle position sensor and electronic control unit including software which provides a simulated signal in response to various full throttle positions and travel. Various time and positioned dependent relationships are sensed by a throttle position sensor and interpreted as a throttle kickdown by the electronic control unit which generates a kickdown signal. For example, in its least complex configuration, sensed travel beyond a predetermined threshold of 90% or 95% of full throttle pedal travel is interpreted as a kickdown request. A second criteria which may be combined with the above approach is to sense the speed of displacement (dT/dt) of the throttle pedal. Displacement speed above a predetermined threshold combined with 90% or 95% throttle displacement will generate a kickdown command. A third criteria is whether the throttle pedal maintains its 90% or 95% (or greater) position for a predetermined time period, e.g. 3, 5 or 10 seconds, or longer. A fourth criteria is whether the throttle pedal has been released such that it is below 10% of full travel and then satisfies other, above-recited criteria.
Thus, it is an object of the present invention to provide a throttle position sensor and software which simulates, by providing an output, when a driver has commanded a kickdown.
It is a still further object of the present invention to provide a sensor and software which simulates a driver kickdown command without utilizing a full travel two position, i.e., on-off sensor.
It is a still further object of the present invention to provide a proportional throttle sensor and electronic control unit which provides a kickdown signal to associated transmission control equipment.
It is a still further object of the present invention to provide a proportional throttle sensor and software which provides a kickdown signal to associated electronic equipment in response to various kickdown actions by the vehicle operator.
Further objects and advantages of the present invention will become apparent by reference to the following description of the preferred embodiment and appended drawings wherein like reference numbers refer to the same components, elements or features.
Referring now to
The combination 10 also includes a microprocessor or electronic control unit (ECU) 20 which receives signals and data from various controls and sensors and controls the overall operation of the engine 12, the master friction clutch 14 and the various sections of the transmission 16. Specifically, the electronic control unit 20 is provided with data or input from the driver through sensors 22 such as the state of the ignition system, whether the transmission is to operate in automatic or manual mode and, in the latter case, provides commands regarding upshifts and downshifts. Additionally, specific driver input is provided by the throttle or accelerator pedal 24 which is coupled to and translates a linear and proportional or modulating throttle position transducer or sensor 26 which provides real time data to the electronic control unit 20 regarding the current position of the accelerator pedal 24. The output of the sensor 26 may be a variable voltage, or coded signal or any other data stream compatible with and readily detected and read by the electronic control unit 20. The current position signal from the throttle position sensor 26 may also be differentiated in the electronic control unit 20 to provide a speed of motion signal, i.e., derivative signals dT/dt, that is the change of position of the accelerator or throttle pedal 24 per unit of time.
Additionally, the electronic control unit 20 will typically receive a signal from an engine output shaft speed sensor 28 indicating the current rotational speed of the engine output shaft. An input shaft speed sensor 32 provides real time data to the electronic control unit 20 regarding the speed of rotation of the input shaft of the transmission 16. Similarly, a transmission output shaft speed sensor 34 provides real time data regarding the rotational speed of the output shaft 18 of the transmission 16.
Certain aspects and components of the engine 12, clutch 14 and transmission 16 are under control of the electronic control unit 20. For example, a fuel control assembly 42 adjusts the flow of fuel to the engine 12 in accordance with the position of the throttle 24 as indicated by the throttle position sensor 26 as well as various software, subroutines and algorithms which control overall operation of the engine 12, the master friction clutch 14 and the transmission 16. For example, during a gear change, fuel to the engine 12 may be reduced momentarily by the fuel control assembly 42 in order to assist synchronization of the engine output shaft and transmission input shaft in the newly selected gear. A clutch operator 44 receives an output signal from the electronic control unit 20 and engages and disengages the master friction clutch 14. A shift operator and sensor assembly 46 includes a plurality of pneumatic, hydraulic or electric operators and associated linear translation sensors which first of all, engage and disengage various gear ratios in the various sections of the transmission 16 and provide data regarding the positions of such actuators to the electronic control unit 20, respectively.
As noted above, rapid depression of the accelerator pedal 24 of essentially any vehicle equipped with an automatic transmission is interpreted by the transmission and associated components as a desire to rapidly accelerate the vehicle by increasing the speed of the engine 12 and downshifting the transmission 16. The throttle position sensor 26, as noted, provides a real time signal regarding the current position of the accelerator pedal 24. Within the electronic control unit 20, this position may be read as an actual measured distance, may be read and utilized as a percentage of travel from zero to one hundred percent, for example, or may be coded into any numerical or alphabetic data chain which is readily recognized and utilized by other components within the electronic control unit 20 to signify the actual position of the throttle pedal 24.
Referring now to
Turning first to Graph A, this represents a kickdown signal which is generated solely by full or substantially full displacement of the accelerator or throttle pedal 24. In order to ensure that a kickdown is commanded when the driver so intends, 95% travel of the accelerator pedal 24 and throttle position sensor 26 has been selected as the threshold for a throttle position only kickdown. Clearly, this 95% threshold can be adjusted to, for example 90% to accommodate and achieve slightly different design and operating parameters. Higher values raise the probability that they may not be exceeded due to linkage misadjustment, component wear or foreign objects lodged behind the throttle pedal 24, thus impeding an intended kickdown. Lower values such as below 90% may cause a kickdown signal and associated activity to occur with less throttle travel than is generally desirable. It will be noted that Graph A is in the high or logic 1 position which requests a kickdown only during and always during periods that the position of the throttle 24 exceeds the 95% kickdown threshold.
Given certain vehicle component complements and diverse design and operating goals, it may be desirable to sense operating parameters in addition to just the position of the throttle 24 to affect or control the kickdown decision. Graph B illustrates such a first alternate operating mode. Here, both the 95% kickdown position threshold and speed of motion of the accelerator pedal 24 beyond a predetermined threshold must be satisfied in order for the electronic control unit 20 to generate a kickdown command. To the left in the throttle position graph is a steep gradient which, in combination with the 95% kickdown position threshold causes the electronic control unit 20 to generate a kickdown command as illustrated by the logic diagram which moves from zero or low to one or high when a sufficiently steep throttle position gradient (derivative) and the 95% kickdown position threshold are both exceeded. By way of comparison, note in the middle of the throttle position graph where a shallow gradient coupled with a throttle position exceeding the 95% kickdown threshold does not generate a kickdown signal from the electronic control unit 20.
Another control alternative is illustrated in Graph C where the 95% accelerator pedal kickdown position threshold is combined with a timer or delay function which senses how long the accelerator pedal 24 has been depressed beyond the kickdown position threshold. The time tmin is a short interval of time such as 2, 3, 5, 8, 10, 12 or 15 seconds or more or less which may be empirically or experimentally chosen and during which the accelerator pedal 24 must be maintained beyond the kickdown threshold in order to generate a kickdown signal. When the kickdown position threshold has been exceeded for a predetermined time, i.e., 3, 5 or 10 second timer has timed out, a kickdown signal is generated by the electronic control unit 20.
It is also possible to combine the position, gradient (derivative) and timer or delay functions. This is represented in Graph D of
A final Graph E presents an operating condition wherein the three requirements of curve D, throttle position beyond the threshold, gradient or derivative greater than a reference value throttle position beyond the threshold exceeding a reference or predetermined time period are combined with a reset threshold. The reset threshold senses whether the accelerator pedal 26 has been fully or substantially fully released and is, at least momentarily, in a substantially undepressed or unactivated state. Once again for purposes of ensuring good data, the reset threshold is not set at 0% travel but is a value between 5 and 15% and preferably about 10%. Thus, only when the throttle pedal 24 has been released or substantially released and then followed by a gradient or derivative beyond the threshold, a final position beyond the kickdown threshold and a final position beyond the kickdown threshold which is maintained at least for the minimum time period will a kickdown signal be generated by the electronic control unit.
Referring now to
Returning to the decision point 54, if the throttle reset function has not been enabled, which applies to Graphs A, B, C and D, the decision point 54 is exited at NO and the program moves to a decision point 62. Likewise, if the throttle position has fallen below the minimum throttle position, the decision point 56 is exited at YES. In both instances, the program 50 enters a decision point 62 which inquires whether the gradient function is enabled. This function appears in the Graphs B and D. If the gradient function is enabled, the program moves to a decision point 64 which inquires whether the gradient or derivative dT/dt is greater than the gradient or derivative reference value. If it is not, the decision point 64 is exited at NO and the program 50 returns to its end point 58. If the gradient or derivative is larger than the reference value, the decision point 64 is exited YES and the program 50 moves to a decision point 66. Similarly, if the gradient function is not enabled, the decision point 62 is exited at NO and the program 50 also moves to the decision point 66.
The decision point 66 inquires whether the throttle position has exceeded the maximum throttle value, 95% of the throttle travel as illustrated in
The entire process in the program 50 is illustrated in Graph E. If the throttle reset function is not enabled, the gradient function is not enabled and the throttle position and timer function are utilized, the operation is presented in Graph C. If the throttle reset function is not enabled but the gradient function and the throttle position are utilized, this is represented by Graph B. If the throttle reset function and the gradient function are not enabled but the throttle position is utilized with the enabled timer function, this operational mode is presented in Graph C. If all of the optional functions are disabled, that is, the throttle reset function, the gradient function and the timer function, the throttle position exceeding the kickdown threshold generates a kickdown signal and this is presented in Graph A.
Upon the generation of a kickdown signal or command by satisfying one of the sets of conditions presented in Graphs A, B, C, D or E of
It will also be appreciated that an electronically generated or simulated kickdown signal or command for an automated mechanical transmission provides numerous benefits. First of all, this configuration eliminates a mechanically actuated switch which may be prone to failure. More importantly, however, the data from the throttle position sensor 26 may be utilized through the electronic control unit 20 to institute or command downshifts based upon several operating conditions as well as diverse values of such operating conditions as illustrated in
The foregoing disclosure is the best mode devised by the inventor for practicing this invention. It is apparent, however, that methods incorporating modifications and variations will be obvious to one skilled in the art of motor vehicle clutches and lubrication thereof. Inasmuch as the foregoing disclosure is intended to enable one skilled in the pertinent art to practice the instant invention, it should not be construed to be limited thereby but should be construed to include such aforementioned obvious variations and be limited only by the spirit and scope of the following claims.
