Non-adjustable throttle position indicator

The need for an accurate measure of the throttle position exists so the electronic engine controller is employed: to continuously check the position of the throttle, to memorize the lowest throttle position reading from the throttle pot, and to define this position as closed throttle. The reading is then updated to compensate for wear in the throttle blade linkages or in the potentiometric device or due to temperature or other conditions. The electronic engine controller will read and retain the lowest measured value of the potentiometric voltage output. This value will then be stored in memory and identified as the closed throttle output until it is necessary to redefine it.

BACKGROUND AND SUMMARY OF THE INVENTION 
Accurate measurement of throttle position is important when using engine 
control means for automotive applications. Past designs of throttle 
position indicators include two-position throttle switches and various 
potentiometric devices. 
The two-position throttle switch provides an electrical signal to the 
engine control means when the throttle is in one of two positions: 
typically closed and wide open. These switches require service after a 
period of use as exposure to an automotive environment may cause the 
deterioration of the materials in the switch. Service or replacement of 
the switch would eventually be necessary in order to provide the 
electronic engine controls with an accurate indication of the throttle 
position. 
Another throttle position indicator which has been used is a potentiometric 
device. This is also known as a throttle pot. The throttle pots are 
mounted on the exterior of the throttle body or carburetor and are 
connected to the throttle blade linkage in such a fashion so as to deflect 
the wiper arm of the throttle pot in proportion to the movement of the 
throttle blade. The potentiometric location of the closed throttle 
position and the wide open throttle position is established during the 
assembly process. This is done by mechanically mounting the throttle pot 
with the wiper arm in a pre-established location with respect to the fully 
closed position of the throttle blade. The throttle pot then provides 
readings to the engine control means, all referenced to the mechanically 
set base line, which is usually the closed throttle position. The accuracy 
of the adjustable throttle pot is in direct proportion to the skill of the 
assembler and to the integrity of the mechanical fastening means holding 
the throttle pot to the throttle body. Eventually, the adjustable throttle 
pot may need service to account for wear in the throttle blade linkage and 
possible deterioration of the potentiometer. 
The subject invention seeks to eliminate the need for mechanical adjustment 
of the throttle pot during the assembly process and also seeks to 
eliminate the need for service adjustments on the adjustable throttle pot 
due to throttle body linkage wear. 
This is accomplished by using a conventional throttle potentiometer with a 
modified mounting mechanism which is nonadjustable. In other words, the 
assembler will need only to affix the throttle pot to the throttle body at 
the designated location and insert the appropriate mounting devices, such 
as screws, through fixed guiding means. The assembly can then be completed 
without the need of any adjustments or decisions to be made by the 
assembler. 
The need for an accurate measure of the throttle position still exists so 
the engine control means is now employed: to continuously check the 
position of the throttle, to memorize the lowest throttle position reading 
from the throttle pot, and to define this position as closed throttle. The 
reading is then updated to compensate for wear in the throttle blade 
linkages or in the potentiometric device or due to temperature or other 
conditions. The engine control means will read and retain the lowest 
measured value of the potentiometric voltage output. This value will then 
be stored in memory and identified as the closed throttle output until it 
is necessary to redefine it. 
Additional features of measuring the throttle position in the 
above-described manner include: the prohibition of false readings due to 
low cranking voltages; the establishment of a default value upon the reset 
of memory (usually due to the disconnection of the battery); the ability 
to reset (a default condition) if no closed throttle indication occurs 
between two sequential cranking events.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIG. 1 which illustrates the structure involved with the 
Non-Adjustable Throttle Position Indicator, the structure shown in FIG. 1 
is merely an exemplar of what an automotive engineer uses to practice the 
methods described in FIG. 2. 
Other exemplars are included in U.S. Pat. No. 4,335,689 by Abe et al. dated 
June 22, 1982 entitled "Electronic Type Air/Fuel Ratio Control System"; 
U.S. Pat. No. 4,508,078 by Takeuchi et al. dated Apr. 2, 1985, entitled 
"Electrically Operated Engine Throttle Valve Acuating Device"; and U.S. 
Pat. No. 4,492,211 by Shimomura et al. dated Jan. 8, 1985, entitled 
"Air-To-Fuel Ratio Control System For Internal Combustion Engine". These 
patents are hereby incorporated by reference. 
In a vehicle with an engine (not shown) employing a throttle means 6 to 
control the flow of fuel to the engine, thereby controlling its speed and 
thusly the power of the vehicle, the throttle means 6 is connected to a 
throttle position indicator 8. 
Throttle position indicator 8, in this particular embodiment, comprises a 
potentiometer 10 with a wiper arm 11. Action of the throttle means 6 
results in correlative action of the wiper arm 11 thereby indicating an 
electrical signal coming out from the indicator 8. As the throttle means 6 
changes its angular position, so does the position of the wiper arm 11 
change thereby producing a different electrical signal. In the particular 
embodiment shown the electrical signal consists of a resistance reading 
typical of a potentiometer. 
Also shown in FIG. 1 is engine control means 15 to which throttle position 
indicator 8 is connected. Within the engine control means 15, there exists 
monitoring means 14, memory 16, memory 17 and computer means 18. 
Various engine parameter inputs from other types of indicators and sensors 
analogous to the throttle position indicator 8 present their signals to 
the monitoring means 14 which is designed to condition the signals from 
the various engine parameter sensors (not shown) and place them in a 
condition to be used by the other parts of the engine control means 15. 
The various engine parameter signals, along with the throttle position 
indicator signal, after being buffered in monitoring means 14, are 
presented to the memory 16 for short term storage. The values are called 
up by the computer means 18 and used along with default values if 
necessary and in transfer functions both stored in memory 17, where 
required by the computer means 18. 
The computer means 18 uses the control method illustrated in FIG. 2 to 
analyze the data from the various engine parameters, including the 
throttle position indicator and to make decisions based on the data values 
and to send information back to the transducers for each parameter through 
the memory 16 and monitoring means 14. 
This control method eliminates the need to mechanically adjust the throttle 
position indicator 8 at a "zero" or reference location corresponding to a 
particular position of the throttle means 6. 
The control method determines the reference position. The use of this 
method prevents the need to re-adjust the throttle position indicator 8 as 
it wears. Wear and temperature changes cause the electrical signal output 
of the indicator 8 to change. Since the method constantly hunts and 
redefines the reference location of wide open throttle or closed throttle 
(a design choice), the system is less affected by the environment and 
wear. 
Referring to FIG. 2 which outlines the method described herein and how it 
interfaces with the structure of the engine control means, the throttle 
means and the nonadjustable throttle position indicator, a variable MINTHR 
is initialized to a predetermined default value in 20. MINTHR represents 
the minimum throttle angle position of the throttle means and in the 
preferred embodiment is a voltage level. 
The default value of MINTHR is started from a predetermined value which is 
stored in the memory 17 of the engine control means 15. This value is 
artificially high and is only utilized in the initialization block 20 when 
the vehicle's battery is disconnected or the vehicle's throttle position 
indicator is changed. Otherwise, the variable MINTHR does not need 
initialization and has a value equal to that determined when the vehicle 
was last in use; it is stored in memory 16 of the engine control means 15. 
The rest of the throttle position indicator system and method is employed 
after the initialization or after the vehicle is restarted as determined 
by a schedule of events and interrupts in the engine control means 15. 
After initialization of MINTHR or upon command or interrupt from the 
control system, the actual throttle position THR is sensed by monitoring a 
voltage presented by the nonadjustable throttle position indicator 8 which 
is mounted to the linkage of the throttle means 6. A movement of the 
throttle means 6 or blade due to the linkage with the wiper arm 11 of the 
throttle position indicator 8, creates a signal from the throttle position 
indicator 8 which is proportional to the position of the throttle means 6. 
This signal is usually a voltage level and can be stored in the engine 
control means 15 or other computer means for later use. 
Once the THR signal is read in block 22, a determination is made by the 
engine control means 15 to check whether the vehicle is at idle. This is 
done in block 28. It can be seen that at this point the minimum throttle 
position MINTHR can be equal to one of two different values: the default 
value from memory 17 or the previously stored value for MINTHR in memory 
16. 
Once the determination is made that the vehicle is or is not at idle in 
block 28, the engine control means 15 sets an idle flag if the vehicle is 
at idle in block 30 or resets an idle flag in block 32 if the vehicle is 
not at idle. The idle flag represents a connection to the other segments 
of the engine control means and provides the condition of the idle flag to 
other segments of the control means as needed, as well as a connection to 
sample various other parameters such as the vehicle speed, engine RPM, the 
condition of the brake switch, and the manifold absolute pressure (MAP), 
etc. The subject throttle position indicator and method utilizes these 
other factors along with the signals from the throttle pot and the 
decisions described herein to decide whether the vehicle is in a true idle 
condition. For example, idle is a condition determined when several 
factors exist. One of those factors is the condition when the throttle 
position THR is less than or equal to the minimum throttle position, 
MINTHR, plus a variable lambda where lambda is a function of the various 
hystereses involved in all of the components of the system. 
Returning now to block 30, which represents the condition where the vehicle 
is at idle and a value for MINTHR has been stored, we proceed to block 34 
for another comparison. The subject comparison determines whether the 
minimum throttle position MINTHR needs updating. This is done by comparing 
the actual throttle position THR with the minimum throttle position 
MINTHR. If THR is less than MINTHR for an appropriate time period T=t, 
then the minimum throttle needs updating and proceeds to block 36. 
Block 36 takes advantage of a previously determined throttle position 
decrement amount. This decrement amount is employed if and only if the 
value of MINTHR after decrementing is greater than zero. This is done to 
keep the value of MINTHR from slipping below zero. 
Following a reset of the idle flag in block 32, a form of fine adjustment 
to MINTHR can take place. It is a positive pressure feature described in 
blocks 38 and 39 which will take advantage of a predetermined increment 
amount of throttle position. Since an increment is not always needed, a 
decision is made in block 38 whether to increment MINTHR. An example of 
the type of analysis performed in block 38 is to apply the increment 
amount to the minimum throttle position MINTHR once every time the vehicle 
has a rapid deceleration. The increment is performed in block 39 if 
needed. This positive pressure on the MINTHR value is necessary due to the 
hysteresis of the potentiometer or of any linkages in the throttle means 
and helps to deal with the situation where idle may not always occur at 
the same physical location of the throttle blade. The predetermined 
default value for minimum acceptable throttle position acts as an upper 
limit for the positive pressure. 
Regardless of whether the MINTHR value has passed through blocks 34, 36 or 
38, it will then proceed to bubble 40 releasing the engine control means 
15 to perform other tasks and to return to resense the actual throttle 
position THR when next scheduled or upon demand or interrupt as required 
by other factors. The return path will be similar to that shown in FIG. 2 
as 42 and will begin with block 22 to read the throttle position THR 
unless an event, such as the disconnection of the battery or throttle 
position indicator 8 has occurred. In which case, the initialization block 
20 will be selected by the engine control means 15 as the starting point 
of the throttle position indication system and method described herein. 
When it is time to resense the throttle position THR, the method follows 
path 42 and is repeated beginning with block 22. 
While the present invention has been disclosed in connection with the 
preferred embodiment thereof, it should be understood that there may be 
other embodiments which fall within the spirit and scope of the invention 
and that the invention is susceptible to modification, variation and 
change without departing from the proper scope or fair meaning of the 
following claims.