Throttle valve position signal correcting apparatus

An apparatus for correcting a throttle valve position signal indicative of a sensed position of a throttle valve provided for controlling the amount of air permitted to enter engine cylinders. The sensed throttle valve position value sensed at an engine idling condition is set for an idle position value. A first error of the idle position value from a first reference value corresponding to a throttle valve idle position designed for an air conditioning unit being not operating. The first error is used to correct a sensed throttle valve position when the air conditioning unit is not operating. A second error of the idle position value from a second reference value corresponding to a throttle valve idle position desired for the air conditioning unit being operating. The second error is used to correct a sensed throttle valve position when the air conditioning unit is operating.

BACKGROUND OF THE INVENTION 
This invention relates to a throttle valve position signal correcting 
apparatus for use with an automotive vehicle having an automatic 
transmission and an internal combustion engine from which a drive is 
transmitted to the automatic transmission. 
Throttle valve position sensors have been used to sense a position of an 
throttle valve provided for controlling the amount of air permitted to 
enter to engine cylinder. The sensed throttle valve position is used to 
control the engine and transmission. For example, Japanese Utility Model 
Kokai No. 1-144451 discloses a conventional apparatus for correcting the 
throttle valve position signal to absorb throttle sensor characteristic 
variations and errors occurring when the throttle valve is assembled in 
the engine. The conventional apparatus is arranged to use a value of the 
throttle valve position signal sensed when the engine speed remains in a 
predetermined range for a time longer than a predetermined value to 
correct the throttle valve position signal. However, the conventional 
apparatus fails to provide an appropriate correction when an accessory 
such as an air conditioning unit or the like operable on power from the 
engine. When the air conditioning unit is operating, a fast idle unit 
operates to hold the throttle valve at a fast idle (somewhat open) 
position so as to increase the engine idling speed at engine idle 
conditions. For this reason, the throttle valve position signal value 
sensed when the engine is judged to be idling with the air conditioning 
unit being operating is different from the throttle valve position signal 
value sensed when the engine is judged to be idling with the air 
conditioning unit being not operating. If the throttle valve position 
signal is corrected with the air conditioning unit being operating, the 
corrected throttle valve position signal indicates a throttle valve 
position smaller than the actual throttle valve position. Consequently, 
the corrected throttle valve position is not suitable for transmission 
position change and line pressure controls. 
SUMMARY OF THE INVENTION 
Therefore, a main object of the invention is to provide an improved 
throttle valve position signal correcting apparatus which can provide an 
accurate throttle valve position signal correction irrelevant of whether 
or not fast idle control is performed. 
There is provided, in accordance with the invention, a throttle valve 
position signal correcting apparatus for use with an automotive vehicle 
including a transmission, an internal combustion engine having engine 
cylinders, a throttle valve located within an engine induction passage for 
controlling the amount of air permitted to enter the engine cylinders, a 
throttle position sensor sensitive to a position of the throttle valve for 
producing a signal indicative of a sensed throttle valve position, and at 
least one accessory operable on power from the engine. The apparatus 
comprises first means for producing an engine idling signal when the 
engine is idling, second means for producing an accessory operation signal 
when the accessory is operating, third means responsive to the engine 
idling signal for setting the sensed throttle valve position for an idle 
position value, fourth means for calculating a first error of the idle 
position value from a first reference value in the absence of the 
accessory operation signal, the first reference value corresponding to a 
throttle valve idle position designed for the accessory being not 
operating, the fourth means including means for calculating a second error 
of the idle position value from a second reference value in the presence 
of the accessory operation signal, the second reference value 
corresponding to a throttle valve idle position designed for the accessory 
being operating, and fifth means for correcting a sensed throttle valve 
position based upon the calculated first error in the absence of the 
accessory operation signal, the fifth means including means for correcting 
a sensed throttle valve position based upon the calculated second error in 
the presence of the accessory operation signal. 
In another aspect of the invention, the throttle valve position signal 
correcting apparatus comprises first means for producing an engine idling 
signal when the engine is idling, second means for producing an accessory 
operation signal when the accessory is operating, third means responsive 
to the engine idling signal for setting the sensed throttle valve position 
for an idle position value, fourth means responsive to the accessory 
operating signal for preventing the throttle valve to close over a fast 
idle position advanced with respect to an idle position, fifth means for 
calculating a first error of the idle position value from a first 
reference value in the absence of the accessory operation signal, the 
first reference value corresponding to a designed value of the throttle 
valve idle position, the fifth means including means for calculating a 
second error of the idle position value from a second reference value in 
the presence of the accessory operation signal, the second reference value 
corresponding to a designed value of the throttle value idle position, and 
sixth means for correcting a sensed throttle valve position based upon the 
calculated first error in the absence of the accessory operation signal, 
the sixth means including means for correcting a sensed throttle valve 
position based upon the calculated second error in the presence of the 
accessory operation signal.

DETAILED DESCRIPTION OF THE INVENTION 
With reference to the drawings, and in particular to FIG. 1, there is shown 
one emboidment of a throttle position signal processing apparatus made in 
accordance with the invention applicable to an automotive vehicle 
installed with an internal combustion engine 10, an automatic transmission 
12, and an accessory such as an air conditioning unit 14. The engine 10 
includes a throttle valve (not shown) provided for movement within an 
engine induction passage to control the amount of air permitted to enter 
the engine cylinders. The throttle valve is associated with an accelerator 
pedal. The degree of rotation of the throttle valve is manually controlled 
by the operator of the automotive vehicle. The drive from the engine 10 is 
transmitted to the driving wheels (not shown) through the automatic 
transmission 12. The numeral 16 designates a fast idle unit which operates 
to open the throttle valve, independently from the accelerator pedal, in 
response to operation of the air conditioning unit 14. The fast idle unit 
16 prevents the throttle valve to close over a fast idle position advanced 
with respect to an idle position. 
The numeral 20 designates a control unit which corrects a throttle valve 
position signal fed thereto from a throttle valve position sensor 22 based 
upon inputs fed thereto from various sensors including an engine speed 
sensor 24, an air conditioner switch 26, and a selected position switch 
28. The throttle valve position sensor 22 preferably is a potentiometer 
electrically connected in a voltage divider circuit for supplying a DC 
voltage proportional to throttle valve position. The throttle valve 
position signal (DC voltage) is fed from the throttle valve position 
sensor 22 to the control unit 20. Preferably, the engine speed sensor 24 
employs a counter which counts a series of crankshaft position electrical 
pulses of a repetition rate directly proportional to engine speed and 
produces an engine speed signal indicative of the speed of rotation of the 
engine. The engine speed signal is fed from the engine speed sensor 24 to 
the control unit 20. The air conditioner switch 26 closes to supply 
current from the engine battery to the fast idle unit 16 and also to the 
control unit 20 when the air conditioning unit 14 is operating. The 
selected position switch 28 produces a selected position signal (SP) 
indicative of an selected position of the automatic transmission 12. The 
selected position signal is fed from the selected position switch 28 to 
the control unit 20. 
The control unit 20 employs a digital computer which includes a central 
processing unit (CPU), a random access memory (RAM), a read only memory 
(ROM), and an input/output control unit (I/O). The central processing unit 
communicates with the rest of the computer via data bus. The input/output 
control unit includes an analog-to-digital converter which receives analog 
signals from various sensors and converts them into digital form for 
application to the central processing unit. The read only memory contains 
the program for operating the central processing unit. 
FIG. 2 is a flow diagram showing the programming of the digital computer as 
it is used to calculate an idle position value K. The computer program is 
entered at the point 202 in response to a command for correcting the 
throttle valve position signal. At the point 204 in the program, the 
various sensor signals are, one by one, read into the computer memory. At 
the point 206 in the program, a determination is made as to whether or not 
the "neutral" position N is selected. If the answer to this question is 
"yes", then the program proceeds to the point 210. Otherwise, the program 
proceeds another determination step at the point 108. This determination 
is as to whether or not the "park" position P is selected. If the answer 
to this question is "no", then the program is returned to the point 204. 
Otherwise, the program proceeds to the point 210. 
At the point 210 in the program, a determination is made as to whether or 
not the sensed engine speed N is greater than a predetermined lower limit 
E1. If the answer to this question is "no", then the program is returned 
to the point 204. Othewise, the program proceeds to another determination 
step at the point 212. This determination is as to whether or not the 
sensed engine speed N is less than a predetermined upper limit E2. If the 
answer to this question is "no", then the program is returned to the point 
204. Otherwise, it means that the sensed engine speed N is within a 
predetermined engine idling speed range defined by the lower and upper 
limits E1 and E2 and the program proceeds to the point 214. 
At the point 214 in the program, a determination is made as to whether or 
not the period of time during which the sensed engine speed N remains 
within the engine idling speed range exceeds a predetermined value t. If 
the answer to this question is "no", then the program is returned to the 
point 204. Otherwise, it means that the engine 10 is idling and the 
program proceeds to another determination step at the point 218. This 
determination is as to whether or not the sensed throttle valve position 
THR is equal to an idle position value K. An initial value, stored 
previously in the computer memory, is used as the idle position value in 
the first cycle of execution of this program. If the answer to the 
question is "yes", then the program is returned to the point 204. 
Otherwise, the program proceeds to another determination step at the point 
218. This determination is as to whether or not the sensed throttle valve 
position THR is greater than the idle position value K. If the answer to 
this question is "yes", then the program proceeds to the point 220 where a 
predetermined value n is added to the idle position value K. The added 
value is stored to update the idle position value K. Following this, the 
program is returned to the point 204. If the answer to the question 
inputted at the point 218 is "no", then the program proceeds to the point 
222 where the predetermined value n is subtracted from the idle position 
value K. The subtracted value is stored to update the idle position value 
K. Following this, the program is returned to the point 204. 
As can be seen from FIG. 2, the idle position value K is brought closer to 
the sensed throttle valve position value THR in each cycle of execution of 
the program when the automatic transmission 12 is in "neutral" or "park" 
position and when the sensed engine speed remains within a predetermined 
idling speed range for a time greater than a predetermined time t. Thus, 
the idle position value K is equal to the throttle valve position sensed 
during engine idling. 
FIG. 3 is a flow diagram of the programming of the digital computer as it 
is used to correct the throttle valve position signal. The computer 
program is entered at the point 302. At the point 304 in the program, the 
throttle valve position signal is read into the computer memory. At the 
point 306 in the program, the determination is made as to whether or not 
the air conditioning unit 14 is operating. This determination is made 
based upon the signal fed from the air conditioner switch 26. If the 
answer to this question is "no", then the program proceeds to the point 
308 where a first reference value K1 is subtracted from the idle position 
value K calculated during the program of FIG. 2 to provide a first error 
.DELTA.K. The first reference value K1 corresponds to an idle (or 
fully-closed) throttle valve position designed for the fast idle unit 16 
being not operating. The program then proceeds to the point 312. If the 
answer to the question inputted at the point 306 is "yes", then the 
program proceeds to the point 310 where a second reference value K2 is 
subtracted from the idle position value K calculated during the execution 
of the program of FIG. 2 to provide a second error .DELTA.K. The second 
reference value K2 corresponds to an idle (or fast idle) throttle valve 
position designed for the fast idle unit 16 being operating. The program 
then proceeds to the point 312. 
At the point 312 in the program, the central processing unit corrects the 
sensed throttle valve position by subtracting the first error .DELTA.K 
from the sensed throttle valve position THR to provide a difference THA 
when the fast idle unit 16 is not operating) or by subtracting the second 
error .DELTA.K from the sensed throttle valve position THR to provide a 
difference THA when the fast idle unit 16 is operating. The program then 
proceeds to the point 314 where the calculated difference THA is used to 
calculate a throttle valve position value, which is used to control the 
gear position change of the automatic transmission 12, from a relationship 
programmed into the computer. Following this, the program proceeds to the 
end point 316. 
It is to be understood that the difference THA calculated when the air 
conditioning unit 14 is not operating is equal to the difference THA 
calculated when the air conditioning unit 14 is operating. It is, 
therefore, possible to provide an accurate throttle valve position signal 
correction irrelevant of whether or not the air conditioning unit 16 is 
operating, that is, irrelevant of whether the fast idle unit 16 is 
operating. If an additional accessory is employed in the automotive 
vehicle, the throttle valve position signal may be corrected in a similar 
manner with an initial value of the idle position value K being set at an 
appropriate value for the additional accessory.