Abstrict An air flow meter which can decrease the error due to the backflow.
Throttle valve 17 which opens and shuts the air intake passage is
installed in the air intake passage of the internal combustion engine.
The first sensor part 161 is installed in the air intake passage
in the upstream of throttle valve 17. Further, the second sensor
part 141 is installed in the air intake passage in the downstream
of throttle valve 17. Pulsation compensating means 671 corrects
the pulsation of the air flow rate signal detected by the first
sensor part by using the output signals of the first and the second
sensor parts 161 141 based on each cylinder of the internal combustion
engine.
Claims What is claimed is:
1. An air flow meter comprising: a throttle valve installed inside
an intake passage of an internal combustion engine and used for
opening and closing an intake passage; a first air flow rate detecting
means installed in an intake passage located in the upstream of
said throttle valve; a second air flow rate detecting means installed
in an intake passage located at the downstream of said throttle
valve; and a pulsation compensating means for compensating a pulsation
in an air flow rate signal of said first air flow rate detecting
means based on output signals from said first and second air flow
rate detecting means corresponding individual cylinders of said
internal combustion engine.
2. An air flow meter of claim 1 wherein said pulsation compensating
means determines a response compensatory signal Qfd by compensating
a response delay of air flow rate signal Qf detected by said first
air flow rate detecting means; determines a deviation signal dQfdb
by subtracting an air flow rate signal Qd detected by said second
air flow rate detecting means from said response compensatory signal
Qfd; and determines an air flow rate signal Qref compensated for
pulsation effect by subtracting said deviation signal dQfdb from
an air flow rate signal Qf detected by said first air flow rate
detecting means.
3. An air flow meter of claim 1 further comprising a throttle
valve opening compensating means for compensating a deviated flow
changing due to throttle valve opening, wherein a deviated flow
changing due to throttle opening in an air flow rate signal compensated
by said pulsation compensating means is corrected based on a compensation
value for deviated flow due to throttle opening obtained by said
throttle opening compensating means.
4. An air flow meter of claim 1 wherein at least one or more of
said first and second air flow rate detecting means for a throttle
valve are integrated with a body of said throttle valve.
5. An air flow meter of claim 1 wherein said first and second
air flow rate detecting means for a throttle valve are air flow
rate detecting means using a heating resistance, and at least one
or more are sensors enable to detect a counter flow.
6. An air flow meter of claim 1 wherein either of said plural
first and second air flow rate detecting means for a throttle valve
is detachable to said throttle body, which is installed at manufacturing
process and used for adjusting a characteristic.
7. An air flow meter comprising: a throttle valve installed inside
an intake passage of an internal combustion engine and used for
opening and closing an intake passage; a first air flow rate detecting
means installed in an intake passage located in the upstream of
said throttle valve; a second air flow rate detecting means installed
in an intake passage located at the downstream of said throttle
valve; and a throttle diagnostic processing means for making a diagnosis
of an operation of said throttle valve with respect to an throttle
opening reference, and an output signal from signals from said first
and second air flow rate detecting means based on individual cylinders
of said internal combustion engine and said throttle opening reference.
8. An air flow meter of claim 7 wherein said throttle diagnostic
processing means detects an abnormal throttle state if a time duration
while a deviation signal dQfdb between an air flow rate signal Qf
detected by said first air flow rate detecting means and an air
flow rate signal Qd detected by said second air flow rate detecting
means continues to deviate outside levels sH and sL is judged to
be larger than a designated value.
9. An air flow meter of claim 7 wherein at least one or more of
said first and second air flow rate detecting means for a throttle
valve are integrated with a body of said throttle valve.
10. An air flow meter comprising: a throttle valve installed inside
an intake passage of an internal combustion engine and used for
opening and closing an intake passage; a first air flow rate detecting
means installed in an intake passage located in the upstream of
said throttle valve; a second air flow rate detecting means installed
in an intake passage located at the downstream of said throttle
valve; and a calculating means for estimating an air flow rate corresponding
to a single cylinder based on a difference between output signals
from said first and second air flow rate detecting means.
11. An air flow meter of claim 10 wherein the first air flow rate
detecting means is of a thermal type effective in detecting a static
characteristic, and the second air flow meter is of a thermal type
effective in detecting a counter flow.
12. An air flow meter of claim 11 wherein the first air flow rate
detecting means is a low-speed detecting means, and the second air
flow rate detecting means is a high-speed detecting means.
13. An air flow meter of claim 7 wherein the first air flow rate
detecting means is of a thermal type effective in detecting a static
characteristic, and the second air flow meter is of a thermal type
effective in detecting a counter flow.
14. An air flow meter of claim 13 wherein the first air flow rate
detecting means is a low-speed detecting means, and the second air
flow rate detecting means is a high-speed detecting means.
15. An air flow meter of claim 1 wherein the first air flow rate
detecting means is of a thermal type effective in detecting a static
characteristic, and the second air flow meter is of a thermal type
effective in detecting a counter flow.
16. An air flow meter of claim 15 wherein the first air flow rate
detecting means is a low-speed detecting means, and the second air
flow rate detecting means is a high-speed detecting means.
Description BACKGROUND OF THE INVENTION
The present invention relates to an air flow meter for measuring
an air flow rate, and specifically to an air flow meter so configured
as to be integrated with a throttle for controlling an air-intake
of the internal combustion engine.
Conventionally, as for the air flow meter for measuring the air-intake
of the internal combustion engine such as automotive engine, thermal
type air flow meters are commonly used because they can detects
mass-flow rate directly. The heating resistance used here includes
a platinum wire winded around a bobbin and coated with glass and
a thin-film resistance formed on the ceramic substrate or a silicon
substrate. As for the method for measuring the flow rate, there
are several well known methods including a method in which the current
supplied in the heating resistance for heating the heating resistance
at a constant temperature is measured directly and a method in which
temperature detecting resistances are placed at upstream side and
downstream side of the heating resistance and a temperature difference
between those temperature detecting resistances is measured.
As for the method for controlling the inlet air flow, a method
for opening and closing an air intake passage by using a throttle
valve. Specifically, electronic control throttle systems for controlling
electrically the throttle valve by using a motor are generally used
due to its excellent control performance.
There is such a problem that the control accuracy is reduced in
case of applying a conventional heating-resistance type air flow
meter to four or less cylinder automotive engines and for the lower
engine speed operation or the overloaded operation in which the
pulsation in the intake air flow arises and its amplitude is large
and counter flow is formed partially. In order to solve this problem,
there is such a solution that plural heating-resistance type air
flow meters are placed at the upstream side of the throttle and
the counter flow is detected by measuring the phase signal s from
those air flow meters, and the control error may be reduced resultantly
as disclosed, for example, in Japanese Patent Publication No. 2855401.
In addition, there is another solution, as disclosed in Japanese
Patent Application Laid-Open Number 6-288291 (1994) and Japanese
Patent Application Laid-Open No. 8-218934 (1996) in which the control
error including the pulsation effect in the air flow rate measured
by the heat-resistance type air flow meter placed at the upstream
of the throttle is compensated by referring to the output from the
pressure sensor placed at the downstream of the throttle, and the
control error may be reduced resultantly.
In attempting to integrating the throttle apparatus and the air
flow meter, there arises another problem in which the measurement
error for the air flow rate increases due to the changes in the
throttle valve opening. In order to solve this problem, there is
such a known solution as disclosed, for example, in Japanese Patent
Application Laid-Open No. 9-53482 (1997) in which the measurement
error may be reduced by optimizing the configuration and layout
of the air flow meter in relative to the throttle valve.
However, there is a first problem that the error due to the backflow
is not decreased sufficiently because the error due to the backflow
increases in the internal combustion engine using variable valve
mechanism, in the methods described in Japanese Patent No.2855401
Japanese Patent Application Laid-Open No.6-288291 and Japanese Patent
Application Laid-Open No. 8-218934.
Further, there is a second problem that the measurement error to
the change of opening of the throttle valve is not decreased sufficiently
in the methods described in Japanese Patent Application Laid-Open
No.9-53482.
Further, there is a second problem that the operational state of
the throttle device has not been diagnosed when the electronically
controlled throttle is used in the conventional air flow meter.
Further, there is a fourth problem that when there are a lot of
engine cylinders in the conventional air flow meter, it is not possible
to detect directly the mass air flow rate and to detect the air
flow rate every cylinder.
SUMMARY OF THE INVENTION
A first object of the present invention is to provide an air flow
meter which can decrease the error due to the backflow.
A second object of the present invention is to provide an air flow
meter which can decrease the measurement error to the change of
opening of the throttle valve.
A third object of the present invention is to provide an air flow
meter which can diagnose the operational state of the throttle device.
A fourth object of the present invention is to provide an air flow
meter which can detect the air flow rate every cylinder. (1) To
achieve the above first object, the present invention takes the
following configuration.
An air flow meter comprising a throttle valve installed inside
an intake passage of an internal combustion engine and used for
opening and closing an intake passage; a first air flow rate detecting
means installed in an intake passage located in the upstream of
said throttle valve; a second air flow rate detecting means installed
in an intake passage located at the downstream of said throttle
valve; and a pulsation compensating means for compensating a pulsation
in an air flow rate signal of said first air flow rate detecting
means based on output signals from said first and second air flow
rate detecting means corresponding individual cylinders of said
internal combustion engine.
The error due to the backflow can be decreased by this configuration.
(2) Preferably, in above-mentioned (1), said pulsation compensating
means determines a response compensatory signal Qfd by compensating
a response delay of air flow rate signal Qf detected by said first
air flow rate detecting means; determines a deviation signal dQfdb
by subtracting an air flow rate signal Qd detected by said second
air flow rate detecting means from said response compensatory signal
Qfd; and determines an air flow rate signal Qref compensated for
pulsation effect by subtracting said deviation signal dQfdb from
an air flow rate signal Qf detected by said first air flow rate
detecting means. (3) To achieve the second object, preferably in
the above-mentioned (1), the air flow meter further comprises; a
throttle valve opening compensating means for compensating a deviated
flow changing due to throttle valve opening, wherein a deviated
flow changing due to throttle opening in an air flow rate signal
compensated by said pulsation compensating means is corrected based
on a compensation value for deviated flow due to throttle opening
obtained by said throttle opening compensating means.
The measurement error to the opening change of the throttle valve
can be decreased by this configuration. (4) Preferably, in the above-mentioned
(1), at least one or more of said first and second air flow rate
detecting means for a throttle valve are integrated with a body
of said throttle valve. (5) Preferably, in the above-mentioned (1),
said first and second air flow rate detecting means for a throttle
valve are air flow rate detecting means using a heating resistance,
and at least one or more are sensors enable to detect a counter
flow. (6) Preferably, in the above-mentioned (1), either of said
plural first and second air flow rate detecting means for a throttle
valve is detachable to said throttle body, which is installed at
manufacturing process and used for adjusting a characteristic. (7)
To achieve the third above-mentioned object, the present invention
takes the following configuration: An air flow meter comprising
a throttle valve installed inside an intake passage of an internal
combustion engine and used for opening and closing an intake passage;
a first air flow rate detecting means installed in an intake passage
located in the upstream of said throttle valve; a second air flow
rate detecting means installed in an intake passage located at the
downstream of said throttle valve; and a calculating means for estimating
an air flow rate corresponding to a single cylinder based on an
difference between output signals from said first and second air
flow rate detecting means. (8) Preferably, in the above-mentioned
(7), said throttle diagnostic processing means detects an abnormal
throttle state if a time duration while a deviation signal dQfdb
between an air flow rate signal Qf detected by said first air flow
rate detecting means and an air flow rate signal Qd detected by
said second air flow rate detecting means continues to deviate outside
levels sH and sL is judged to be larger than a designated value.
(9) Preferably, in the above-mentioned (7), at least one or more
of said first and second air flow rate detecting means for a throttle
valve are integrated with a body of said throttle valve. (10) To
achieve the fourth above-mentioned object, the present invention
takes the following configuration.
An air flow meter comprising: a throttle valve installed inside
an intake passage of an internal combustion engine and used for
opening and closing an intake passage; a first air flow rate detecting
means installed in an intake passage located in the upstream of
said throttle valve; a second air flow rate detecting means installed
in an intake passage located at the downstream of said throttle
valve; and a calculating means for estimating an air flow rate corresponding
to a single cylinder based on a difference between output signals
from said first and second air flow rate detecting means.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a system configuration view showing the whole configuration
of an internal combustion engine which has the air flow meter according
to the first embodiment of the present invention.
FIG. 2 is a system configuration view showing the configuration
of the air flow meter according to the first embodiment of the present
invention.
FIG. 3 is a circuit diagram showing the configuration of the first
air flow meter according to the first embodiment of the present
invention.
FIG. 4 is a circuit diagram showing the configuration of the second
air flow meter according to the first embodiment of the present
invention.
FIG. 5 is a block diagram showing the configuration of the air
flow rate correction means in the throttle-integrated air flow meter
according to the first embodiment of the present invention.
FIG. 6 is a flow chart showing the operation of the pulsation compensating
means in the throttle-integrated air flow meter according to the
first embodiment of the present invention.
FIG. 7 is a waveform view showing the operation of the pulsation
compensating means in the throttle-integrated air flow meter according
to the first embodiment of the present invention.
FIG. 8 is an illustration showing the operation of the throttle
opening compensating means in the throttle-integrated air flow meter
according to the first embodiment of the present invention.
FIG. 9 is an illustration showing the operation of the throttle
diagnosis processing means in the throttle-integrated air flow meter
according to the first embodiment of the present invention.
FIG. 10 is a waveform view showing the operation of the throttle
diagnosis processing means in the throttle-integrated air flow meter
according to the first embodiment of the present invention.
FIG. 11 is a system configuration view showing the whole configuration
of an internal combustion engine which has the air flow meter according
to the second embodiment of the present invention.
FIG. 12 is a flowchart showing the operation of a control unit
in the throttle-integrated air flow meter according to the second
embodiment of the present invention.
FIG. 13 is a flowchart showing the operation of a control unit
in the throttle-integrated air flow meter according to the second
embodiment of the present invention.
FIG. 14 is a system configuration view showing the whole configuration
of an internal combustion engine which has the air flow meter according
to the third embodiment of the present invention.
FIG. 15 is a system configuration view showing the whole configuration
of an internal combustion engine which has the air flow meter according
to the fourth embodiment of the present invention.
FIG. 16 is a system configuration view showing the whole configuration
of an internal combustion engine which has the air flow meter according
to the fifth embodiment of the present invention.
FIG. 17 is a system configuration view showing the whole configuration
of an internal combustion engine which has the air flow meter according
to the sixth embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Hereafter, the configuration and the operation of the air flow
meter according to the first embodiment of the present invention
will be explained by using FIG. 1-FIG. 10.
First, the whole configuration of the internal combustion engine
provided with the air flowmeter according to this embodiment will
be explained by using FIG. 1 first.
FIG. 1 is a system configuration view showing the whole configuration
of an internal combustion engine which has the air flow meter according
to the first embodiment of the present invention.
Engine 1 has a crank chain comprising con'rod 4 and crank shaft
5. Combustion chamber 3 is formed with piston 2 connected to the
crank chain and engine head 8 of engine 1. Combustion chamber 3
is sealed up with intake valve 10 installed in engine head 8 exhaust
valve 11 and sparking plug 12. Intake valve 10 and exhaust valve
11 are operated by variable valve mechanism 40 and 41. Engine 1
inhales air necessary for combustion into combustion chamber 3 by
the operation of throttle valve 17 and the reciprocating motion
of piston 2. The dust and foreign particles included in air inhaled
into engine 1 are removed in air cleaner 15. The amount of intake
air used for the calculation of fuel injection amount is measured
by sensor part 161141 of the air flow meter in throttle-integrated
air flow meter 20. Sensor part 161 is arranged on the upstream side
of throttle valve 17 and sensor part 141 is arranged on the downstream
side of throttle valve 17. Because the combustion chamber 3 and
intake port 19 in the downstream of throttle valve 17 becomes a
negative pressure lower than the atmospheric pressure when the opening
of throttle valve 17 is small, the change of the amount of the intake
air due to the pressure in the intake pipe is always measured and
reflected to the control of engine 1. Control unit (CU) 60 by which
engine 1 is controlled detects the operating state of engine 1 based
on the signals from various sensors, controls the operation of variable
valve mechanism 40 41 installed in engine 1 and also controls
the fuel amount injected from fuel injection valve 13 and the fuel
injection timing are controlled.
The manipulated variable of accelerator pedal 71 operated by driver
70 for the vehicle where engine 1 is installed is converted into
the electric signal by potentiometer 72 and input to control unit
60. Additionally input to control unit 60 as a signal which detects
the operating state, an engine revolution speed from the crank angle
sensors 6 7 installed in crank shaft 5 for instance, an air flow
rate signal from sensor part 161141 in throttle-integrated flow
meter 20 an air/fuel ratio signal from air/fuel ratio sensor installed
in exhaust pipe 23 an exhaust gas temperature signal from temperature
sensor 25 which detects the temperature of exhaust catalyst 26
an in-cylinder pressure signal of pressure sensor 21 which detects
the pressure in combustion chamber 3 and a knocking signal from
knocking sensor 22 by which the knocking are detected. Control unit
60 outputs a control signal to the signal of the input operating
state, controls motor 18 which actuates throttle valve 17 and variable
valve mechanism 40 by which intake valve 10 are actuated, and adjusts
the amount of the air inhaled into engine 1. Control unit 60 outputs
a control signal to fuel injection valve 13 according to the operating
state, and adjusts the fuel injection amount and the fuel injection
timing.
Next, the configuration of the air flow meter according to this
embodiment will be explained by using FIG. 2.
FIG. 2 is a system configuration view showing the configuration
of the air flow meter according to the first embodiment of the present
invention.
Throttle valve 17 is driven by motor 18. The first sensor part
161 which includes heat resistor 161a is installed in the upstream
of throttle valve 17. The second sensor part 141 which includes
heat resistor 141a is installed in the downstream of throttle valve
17. The first sensor part 161 and the second sensor part 141 are
integrated with throttle valve 17 and motor 18 to form throttle-integrated
air flow meter 20.
control unit 60 is provided with sensor actuator driving means
(S-Act Drv) 66 air flow rate correction means (Q-CMP) 67 and engine
control unit (ECU) 65. First sensor drive circuit (first-S Drv)
662 by which the first sensor part 161 is driven, second sensor
drive circuit (2st-S Drv) 663 by which the second sensor part 141
are driven, and throttle drive circuit (TH Drv) 661 which drives
throttle valve 17 are provided in sensor actuator driving means
66. First sensor drive circuit 662 second sensor drive circuit
663 and throttle drive circuit 661 may be provided in throttle-integrated
air flow meter 2 besides control unit 60. An output Vin1 Vin2 of
each of sensor drive circuit 662 663 and an output .theta.TH of
throttle drive circuit 661 are input to air flow rate correction
means 67. Air flow rate correction means 67 corrects the error of
the measured air flow rate, and outputs the corrected signal of
the air flow rate Qref to engine control unit 65. Engine control
unit 65 controls the engine based on the air flow rate Qref output
from the air flow rate correction means 67 the output .theta.TH
of throttle drive circuit 661 etc.
Next, the configuration of the first air flow meter according to
this embodiment will be explained by using FIG. 3.
FIG. 3 is a circuit diagram showing the configuration of the first
air flow meter according to the first embodiment of the present
invention.
First sensor part 161 includes temperature compensating resistor
161b besides heat resistor 161a shown in FIG. 2. First sensor drive
circuit 662 has resistors R1 R2 error amplifier AMP1 preamplifier
P-AMP1 and transistor TR1. Heat resistor 161a, temperature compensating
resistor 161b, and resistors R1 and R2 compose a bridge circuit.
First sensor part 161 and first sensor drive circuit 662 compose
first air flow meter 16 described later in FIG. 5.
Error amplifier AMP1 controls transistor TR1 so as to balance the
bridge circuit, and controls so that the temperature of heat resistor
161a can become higher by a constant temperature than that of temperature
compensating resistor 161b. Here, because the electric current which
flows to heat resistor 161a changes so that the bridge circuit can
be balanced when the temperature of the heating resistor 161a deprived
of heat by intake air A1 changes, and thus the temperature of heating
resistor 161a is kept to a constant temperature, it becomes possible
to measure the intake air amount by using the electric current which
flows to heat resistor 161a. The electric current which flows to
heat resistor 161a is amplified by preamplifier P-AMP1 and output
as first sensor output Vin1. Because temperature compensating resistor
161b detects the temperature of the intake air, the error due to
the temperature of the intake air can be corrected.
Here, the resistor formed by winding the platinum line around the
bobbin and then by coating it with the glass, or the thin film resistor
body formed on a ceramic substrate or a silicon substrate is used
as heat resistor 161a, for example. That is, the heat capacity is
a comparatively large. Therefore, and an excellent resistor in the
detection of the static characteristic is obtained although unsuitable
to the measurement of the flow direction and the measurement which
needs a high-speed response.
Next, the configuration of the second air flow meter according
to this embodiment will be explained by using FIG. 4.
FIG. 4 is a circuit diagram showing the configuration of the second
air flow meter according to the first embodiment of the present
invention.
Second sensor part 141 includes temperature compensating resistor
141b and temperature detection resistors 141d, 141e, 141f, 141g
besides heat resistor 141a shown in FIG. 2. Second sensor drive
circuit 663 has resistors R1 R2 error amplifier AMP1 error amplifier
AMP2 and transistor TR1. Heat resistor 141a, temperature compensating
resistor 141b, and resistors R1 and R2 compose a bridge circuit.
Second sensor part 141 and second sensor drive circuit 664 compose
second air flow meter 14 described later in FIG. 5.
Error amplifier AMP1 controls transistor TR1 so as to balance the
bridge circuit, and controls so that the temperature of heat resistor
141a can become higher by a constant temperature than that of temperature
compensating resistor 141b. Here, the electric current which flows
to heat resistor 141a changes so that the bridge circuit can be
balanced when the temperature of the heating resistor 141a deprived
of heat by intake air A2 changes, and thus the temperature of heating
resistor 141a is kept to a constant temperature. Because temperature
compensating resistor 161b detects the temperature of the intake
air, the error due to the temperature of the intake air can be corrected.
Temperature detection resistors 141d and 141e are arranged on the
upstream side of air stream A2 with respect to heat resistor 141a,
and temperature detection resistors 141f and 141g are arranged on
the downstream side of air stream A2 with respect to heat resistors
141a. Temperature detection resistor 141d, 141e and temperature
detection resistors 141f and 141g compose a bridge circuit. When
the flow direction of air stream A2 is in a direction shown by arrow
A2 that is, air stream is a forward flow in which air is inhaled
from an air cleaner to the engine, the temperature of temperature
detection resistors 141d and 141e becomes lower than that of temperature
detection resistors 141f and 141g, and error amplifier AMP2 outputs
a positive output. The absolute value of the output corresponds
to the flowing air amount. On the other hand, the temperature of
temperature detection resistors 141f and 141g become lower than
the that of temperature detection resistors 141d and 141e when the
flow direction of air stream A2 is opposite to the direction of
arrow A2 that is, the air flows backward from the engine to the
air cleaner, and error amplifier AMP2 outputs a negative output.
The absolute value of the output corresponds to the flowing air
amount. When the flow of the intake air is a following current,
output Vin2 of error amplifier AMP2 becomes a positive output, and
when flowing backward, it becomes a negative output. It is, therefore,
possible to measure the amount of the intake air which includes
the pulsation of the intake air.
Heat resistor 141a is one that the thin film or thick film of the
polysilicon resistance body, and platinum or tungsten as a heating
unit are formed on the base such as the flat glass, the ceramic,
and silicon for instance. Therefore, heat resistor 141a has small
heat capacity, and improved response. Further, the detection of
the two way flow which includes the backflow becomes possible by
using temperature detection resistors 141d, 141e, 141f, and 141g.
This method may cause the error easily in the static characteristic
due to the pulsation influence if high-speed sampling etc. are not
carried out when the air flow rate is leveled while the change of
the flow can be detected easily.
First air flow meter 16 which is effective in the detection of
the static characteristic is arranged on the upstream side of throttle
valve 17 and second air flow meter 14 effective in the transition
characteristic which can detect the backflow is arranged on the
downstream side in this embodiment as explained above. Accordingly,
the measuring accuracy can be improved overall by using effectively
two kinds of different air flow meters.
Next, the configuration of the air flow rate correction means in
the throttle-integrated air flow meter according to this embodiment
will be explained by using FIG. 5.
FIG. 5 is a block diagram showing the configuration of the air
flow rate correction means in the throttle-integrated air flow meter
according to the first embodiment of the present invention.
Air flow rate correction means (Q-CMP) 67 comprises: pulsation
compensating means (P-CMP) 671 throttle opening compensating means
(.theta.TH-CMP) 672 and throttle diagnosis processing means (TH-DAG)
673. Air flow rate correction means 67 inputs output Vin1 of the
first air flow meter 16 output Vin2 of the second air flow meter
14 throttle opening .theta.TH output from throttle drive circuit
661 shown in FIG. 2 engine revolution speed Ne and crank angle
.theta.TH output from the crank angle sensors 6 7 shown in FIG.
1 and cam phase .phi.c. Air flow rate correction means 67 outputs
corrected air flow rate Qref and diagnosis result TAdag of the throttle
to the engine control unit 65 based on these input signals.
Next, the operation of pulsation compensating means 671 in the
throttle-integrated air flow meter according to this embodiment
will be explained by using FIG. 6 and FIG. 7.
FIG. 6 is a flow chart showing the operation of the pulsation compensating
means in the throttle-integrated air flow meter according to the
first embodiment of the present invention. FIG. 7 is a waveform
view showing the operation of the pulsation compensating means in
the throttle-integrated air flow meter according to the first embodiment
of the present invention. in FIG. 7(A)-FIG. 7(D), the axis of ordinate
designates air flow rate Q, and the axis of abscissa time T.
Pulsation compensating means 671 makes compensation the air flow
which includes the backflow when pulsating, and it is used to measure
the air stream especially inhaled into each cylinder of the engine
accurately. It is used to reduce the error when the backflow is
generated by the variable valve operation etc. The characteristic
when pulsing including the backflow can be improved in combining
two or more sensors with a different response.
Pulsation compensating means 671 takes output Vin1 of the first
air flow meter 16 and output Vin2 of the second air flow meter 14
in step s10.
Next in step s20 pulsation compensating means 671 converts output
Vin1 of first air flow meter 16 and Output Vin2 of second air flow
meter 14 into air flow rate Qf and Qb respectively. The conversion
from output Vin of the air flow meter to air flow rate Q is carried
out by using the map etc. memorized beforehand for the relation
between both.
Next, pulsation compensating means 671 compensates the response
of the signal of air flow rate Qf measured by first air flow meter
16 in step s30.
Here, actual air flow rate QTR is a pulsation flow in which the
positive flow rate and the negative flow rate alternately appear
as shown in FIG. 7(A). On the other hand, the backflow (negative
flow rate) can not be detected from air flow rate Qf detected by
the first air flow meter 16 as shown in FIG. 7(A), and it has the
response delay. This is because first air flow meter 16 is unsuitable
for the measurement of the flow direction, have not high speed response,
but the delay of the response, although it has comparatively large
heat capacity as mentioned above, and is excellent in the detection
of the static characteristic.
Then, in step s30 pulsation compensating means 671 compensates
the response delay of the signal of air flow rate Qf measured by
first air flow meter 16 and obtains response compensatory signal
Qfd in which the response delay is recovered. The compensating operation
of the response delay is performed for instance as follows. Assumed
that the values obtained by sampling air flow rate Qf at fixed interval
time are Qf(t1), Qf(t2), Qf(t3), . . . . Qfd(t1)=(Qf(t1)-Qf(t2).times.k1+Qf(t1)).
Here, k1 is an arbitrary constant. The compensating operation of
the response delay may be carried out by using another method.
Response compensatory signal Qfd is a signal that the backflow
part (negative part) of actual flow rate QTR becomes positive as
shown in FIG. 7(A).
Next, pulsation compensating means 671 calculates the deviation
in step s40. The level of the following current and the backflow
is influenced by the flow rate dependency etc. of the sensor, and
mean value shifts somewhat, although output Qb of the second air
flow meter 14 keeps the phase relation of the backflow to actual
flow rate good as shown in FIG. 7(B). Especially, in the downstream
of the throttle, the waveform changes easily due to the backflow.
In the deviation operation in step s40 difference (Qfd-Qb) between
output Qb of the second air flow meter 14 and response compensatory
signal Qfd obtained in step s30 is calculated to obtain pulsation
correction signal dQfdb. Pulsation correction signal dQfdb is a
signal to emphasize only the error when flowing backward as shown
in FIG. 7(C).
Next, pulsation compensating means 671 performs the correction
operation in step s50. The difference between output Qf of the first
air flow meter 16 and pulsation correction signal dQfdb is obtained
by the correction operation. Fixed coefficient k2 is multiplied
by pulsation correction signal dQfdb at that time, and air flow
rate Qref corrected is obtained as difference (Qf-k2.multidot.dQfdb).
As a result, the backflow error can be decreased from the signal
including the backflow error.
The intake air of each of cylinders can be measured accurately
by carrying out the operation processing of the above steps s10-s50
at once every sampling time.
A similar effect can be achieved even if the correction is made
by paying attention to the backflow phase relation of output Qb
of air flow meter 14 although the pulsation correction is made
by using the difference of two flow meters in the above-mentioned
description. In this, the polarity of signal Qfd in which the response
delay is recovered is reversed for the period of output Qb of air
flow meter 14 being at the backflow phase (For instance, during
time t1-t2 of FIG. 7(B)) (to obtain air flow rate Qref' corrected
by reversing the polarity of pulsation signal Qfd-p of FIG. 7(A)).
For example, the polarity of signal Qfd in which the response delay
is recovered and the polarity of pulsation signal Qfd-p of FIG.
7(A) are reversed for the period of output Qb of air flow meter
14 being at the backflow phase, for instance, during time t1-t2
of FIG. 7(B) to obtain air flow rate Qref' corrected. The influence
on the content of the correction of the air flow rate can be reduced
according to this method even if the direct current level of air
flow meter 14 changes.
In pulsation compensating means 671 as explained above, the error
for the pulsation included in the output of the first air flow meter
16 can be corrected by using the output of the second air flow meter
14 to obtain air flow rate signal Qref corrected for the pulsation.
Next, the operation of throttle opening compensating means 672
in the throttle-integrated air flow meter according to this embodiment
will be explained by using FIG. 8.
FIG. 8 is an illustration of the operation of the throttle opening
compensating means in the throttle-integrated air flow meter according
to the first embodiment of the present invention.
If throttle valve 17 and sensor part 161 of the air flow meter
are integrated in configuration as shown in FIG. 2 Air flow meters
16 and 14 come to be influenced easily by the difference of the
throttle opening because they are arranged in the neighborhood of
throttle valve 17. Flow velocity is almost constant in the vicinity
of throttle opening fully opened except the vicinity of the wall
of the throttle body. However, When the throttle valve is shut,
the air flows only from the space between the throttle valve and
the throttle body. Therefore, the flow velocity in the vicinity
of the center of the throttle body is small, it is large near the
flow of air on the both sides. Further, the flow velocity becomes
small in the vicinity of the wall of the throttle body. The error
comes to cause in the measurement result of the air flow rate by
the air flow meter when the flow velocity changes according to the
throttle opening even if the amount of the intake air is constant.
Then, throttle opening compensating means 672 shown in FIG. 5 compensates
the error by the throttle opening by using the correction values
of the throttle current transformation shown in FIG. 8. FIG. 8 shows
the relationship between throttle opening .theta.TH and correction
values kTH of the error due to the throttle valve current transformation.
The error due to the current transformation of the throttle opening
shows the tendency to grow in the middle of the throttle opening
compared with the full close and the full open of the throttle opening.
Further, because the error due to the throttle opening changes depending
on the condition of the engine speed, throttle opening compensating
means 672 has a map by which throttle current transformation correction
value kTH is obtained from throttle opening .theta.TH and engine
revolution speed N (N1N2N3) as shown in FIG. 8. Throttle opening
compensating means 672 can obtain throttle current transformation
correction value kTH according to throttle opening .theta.TH and
engine revolution speed N by using the map shown in FIG. 8. Air
flow rate correction means 67 can output air flow rate Qref corrected
by multiplying the correction value obtained by throttle opening
compensating means 672 by the corrected air flow rate obtained by
pulsation compensating means 671.
The correction data shown in FIG. 8 can be obtained by learning
and measuring automatically so that the difference of two air flow
meters may become constant under a constant condition, and storing
the data. It is possible to decrease the current transformation
error anytime by executing this every time at the engine starting
etc.
Air flow meter 14 in the throttle downstream can be assumed to
be a detachable structure when the current transformation error
is corrected only when adjusting the air flow meter before shipping.
the current transformation error be memorized as correction data
with the error when pulsing mentioned above. Thereby, the correction
becomes enable. The manufacturing cost increases if the air flow
meters are arranged in the top and the bottom of the throttle valve
because the number of heat resistors increases. However, the manufacturing
cost is decreased by installing air flow meter 14 detachable only
when adjusting. Further, the accuracy of measurement of the air
flow rate can be improved by correcting the current transformation
error.
The current transformation error can be decreased by using the
throttle opening compensating means in this embodiment as explained
above.
Next, the operation of throttle diagnosis processing means 673
in the throttle-integrated air flow meter according to this embodiment
will be explained by using FIG. 9 and FIG. 10.
FIG. 9 is a flow chart showing the operation of the throttle diagnosis
processing means in the throttle-integrated air flow meter according
to the first embodiment of the present invention. FIG. 10 is a waveform
view illustrating the operation of the throttle diagnosis processing
means in the throttle-integrated air flow meter according to the
first embodiment of the present invention. In FIG. 10(A)-FIG. 10(D),
the axis of abscissas designates time T. The ordinate of FIG. 10(A)
designates throttle opening instruction Tn, the ordinate of FIG.
10(B) designates air flow rate Q, the ordinate of FIG. 10(C) designates
deviation signal dQfb, and FIG. 10(D) diagnosis signal width signal
Tdn.
Throttle diagnosis processing means 673 judges the operation condition
to the throttle opening instruction from the comparison of signals
of air flow meters 14 16 arranged at the top and bottom of throttle
valve 17 and 16 at the switching action, and does the operation
diagnosis of throttle valve 17 without a throttle opening sensor
etc.
Throttle diagnosis processing means 673 outputs throttle opening
instruction value Tn instep s20 of FIG. 9. Throttle opening instruction
value Tn switches time T which indicates the throttle opening as
shown in FIG. 10(A) to plural stages like T1 T2 . . . . The processing
in steps s20-s30 are executed one by one for the instruction value
when throttle opening instruction value T1 is output first. When
the diagnosis processing to throttle opening instruction value T1
ends, the following throttle opening instruction value T2 is output
in step s20 and the processing is executed one by one for the instruction
value. When the diagnosis processing to throttle opening instruction
value T1 ends, the processing to the following throttle opening
instruction value T3 is executed. The processing is executed one
by one for two or more throttle opening instruction values Tn in
a similar way.
In step s21 next, throttle diagnosis processing means 673 detects
output signal Vin1 and Vin2 of the first and the second air flow
meters, respectively.
Next, in step s22 throttle diagnosis processing means 673 converts
detected output signals Vin1 and Vin2 into air flow rate Qf and
Qb, respectively. When air flow rate Qf changes, for example, into
the air flow rate as shown in FIG. 10(B) for throttle opening instruction
T1 the air flow rate in the downstream of the throttle valve changes
like air flow rate Qb of FIG. 10(B) when the throttle valve works
normally. On the other hand, the air flow rate in the downstream
of the throttle valve changes like air flow rate Qb' of FIG. 10(B)
if the response delay etc. occurs when the throttle valve opens.
Next, throttle diagnosis processing means 673 calculates deviation
dQfb(=Qf-Qb) of the air flow rate within the instruction time T1
in step s23. Deviation dQfb changes as shown in FIG. 10(C) when
the opening of the throttle valve is normal. On the other hand,
because the increase in the air flow rate in the downstream of the
throttle valve is delayed when the opening of the throttle valve
is abnormal, deviation dQfb changes remarkably compared with the
above normal case as shown in FIG. 10(C).
Next, in step s24 throttle diagnosis processing means 673 compares
deviation dQfb of the air flow rate with a constant diagnosis level
sH, and outputs the width of the part at the level higher than the
diagnosis level sH as diagnosis signal width signal Td1 as shown
in FIG. 10(D). Diagnosis signal width signal Td1' under abnormal
circumstances is output when the response delay occurs in the throttle
valve. Similarly, a negative diagnosis level sL is provided, and
diagnosis signal width signal Td1 is obtained similarly by using
this diagnosis level sL.
Next, in step s25 throttle diagnosis processing means 673 judges
whether diagnosis signal width signal Td1 is larger than throttle
opening instruction T1 in step s20. The state when diagnosis signal
width signal Td1 is larger than throttle opening instruction T1
shows that the throttle valve does not open for instance due to
the breakdown of the motor etc. at all. Throttle diagnosis processing
means 673 judges as abnormal judgment A in step s26 at this time.
Abnormal judgment A means a breakdown such as motors.
On the other hand, when diagnosis signal width signal Td1 is not
larger than throttle opening instruction T1 throttle diagnosis
processing means 673 calculates ratio t1r(=Td1/T1) of diagnosis
signal width signal Td1 and throttle opening instruction T1 in step
s27.
Next, in step s28 throttle diagnosis processing means 673 judges
whether ratio t1r is smaller than fixed reference level Ts. In the
small situation, throttle diagnosis processing means 673 determines
that the throttle valve works normally because the difference of
the air streams in the upstream and the downstream of the throttle
valve is little in step s29.
On the other hand, when ratio t1r is not smaller than fixed reference
level Ts, throttle diagnosis processing means 673 judges as abnormal
judgment B of the throttle valve vein step s30. Abnormal judgment
B means that the response gain of the control unit is bad, the throttle
valve does not work with good response.
The accuracy of an abnormal judgment can be improved by outputting
two or more throttle opening instruction values Tn, and understanding
the operational state under different conditions in step s20 because
the abnormality of system including the air flow meter may occur
despite normal appearance.
As mentioned above, the operation diagnosis of the throttle becomes
possible even if the throttle opening signal is not used, and the
safety of the system improves in this embodiment. There is an effect
that the accuracy of the measurement can be improved even when pulsing
including the current transformation and the backflow of the throttle.
This method is also applied to the diagnosis of the variable valve.
In this embodiment as explained above, the corrected air flow rate
signal for the pulsation can be obtained by installing the air flow
meter in the upstream and the downstream of the throttle valve respectively,
and correcting the error for the pulsation included in the output
of the first air flow meter by the output of the second air flow
meter in the air flow rate correction means. Further, the current
transformation error can be decreased. In addition, the operation
diagnosis of the throttle becomes possible even if the throttle
opening signal is not used, and the safety of the system is improved.
Next, the configuration and operation of the air flow meter according
to the second embodiment of the present invention will be explained
by using FIG. 11-FIG. 13.
First, the whole configuration of internal combustion engine which
installs the air flow meter according to this embodiment will be
explained by using FIG. 11.
FIG. 11 is a system configuration view showing the whole of internal
combustion engine which installs the air flow meter according to
the second embodiment of the present invention. The same sign as
FIG. 1 designates the same part.
The engine 1A in this embodiment has more than four cylinders,
and eight cylinders or two banks of four cylinders in the example
shown in Figure. It is possible to distinguish the signal of each
cylinder by installing the air flow meter in the upstream and the
downstream of the throttle valve in this embodiment.
The throttle-integrated air flow meter 20A including throttle valve
17 motor 18 and first sensor part 161 is installed in intake port
19. The first sensor part 161 is arranged in the upstream of throttle
valve 17. The throttle-integrated air flow meter 20A is connected
to control unit 60A, sensor actuator driving means 66 air flow
rate correction means 67 and engine control unit 65 are provided
in control unit 60A as shown in FIG. 2.
First sensor drive circuit 662 which drives the first sensor part
161 and throttle drive circuit 661 which drives and throttle valve
17 are provided in sensor actuator driving means 66. In addition,
second sensor parts 141A and 141B are installed on the downstream
side of the throttle valve, and in the downstream of the branch
connection of two parts of four cylinders and the upstream side
of the branch connection of each of the cylinders. Second sensor
drive circuit which drives second sensor parts 141A and 141B respectively
is installed in sensor actuator driving means 66 of control unit
60A.
The judgment of the signal of each cylinder becomes possible by
at least one air flow meter although two air flow meters are provided
on the downstream side of the throttle valve in the above-mentioned
explanation.
Next, the operation of control unit in the throttle-integrated
air flow meter according to this embodiment will be explained by
using FIG. 12 and FIG. 13.
FIG. 12 is a flow chart showing the operation of control unit in
the throttle-integrated air flow meter according to the second embodiment
of the present invention. FIG. 13 is a waveform diagram showing
the operation of control unit in the throttle-integrated air flow
meter according to the second embodiment of the present invention.
In step s40 of FIG. 12 control unit 60A detects output signals
Vin1 Vin2 and Vin3 of first and second air flow meter which includes
the first sensor part 161 and the second sensor parts 141A, 141B,
respectively.
Next, in step s42 control unit 60A converts detected output signals
Vin1 Vin2 and Vin3 into air flow rate Qf, Qb1 and Qb2 respectively.
Air flow rate Qf is as shown in FIG. 13(A). Here, certain backflow
can not be detected in the first air flow meter because the waveform
may be synthesized in the upstream of the throttle even when the
backflow is caused in each cylinder by the interference of four
cylinders and four cylinders of the downstream side. On the other
hand, air flow rate Qb1 and Qb2 are as shown in FIG. 13(B) and FIG.
13(C), respectively.
Next, control unit 60A calculates difference dQfb1(=Qf-Qb1) between
output Qb1 of one bank and output Qf of the first air flow meter
in step s44. As a result, the flow rate which includes the backflow
of one cylinder (1cylind) of the other bank can be detected.
In addition, difference (Qb2-dQfb1) of the measurement with the
air flow meter on the upstream side can be obtained by comparing
difference dQfb1(=Qf-Qb1) with output Qb2 of the other bank, or
taking the difference for instance. That is, although the air flow
rate which flows from one bank to the other bank cannot be measured
in the air flow meter of the upstream, it becomes possible to obtain
as difference (Qb2-dQfb1) in this embodiment. In addition, the accuracy
of the discretion signal to each cylinder can be improved by making
the error correction by using this difference signal.
Especially, the thermal type air flow meter has the feature that
the mass flow rate can be achieved directly even if neither a lot
of calculation nor maps, etc. are used. Therefore, there is a feature
of obtaining the air flow rate classified into the cylinders in
a multi-function engine by carrying out brief calculation. Accordingly,
the control of a car engine can be optimized, and exhaust gas from
the engine can be decreased.
The signal of each cylinder in the engine more than four cylinders
can be distinguished according to this embodiment as explained above.
Next, the whole configuration of an internal combustion engine
which installs the air flow meter according to the third embodiment
of the present invention will be explained by using FIG. 14.
FIG. 14 is a system configuration view showing the whole configuration
of an internal combustion engine which has the air flow meter according
to the third embodiment of the present. The same sign as FIG. 1
designates the same part.
Throttle-integrated air flow meter 20B comprising throttle valve
17 motor 18 and second sensor part 141 is installed in intake
port 19. The second sensor part 141 is arranged in the downstream
of throttle valve 17. Throttle-integrated air flow meter 20B is
connected to control unit 60B, sensor actuator driving means 66
air flow rate correction means 67 and engine control unit 65 are
installed in control unit 60B as shown in FIG. 2. First sensor drive
circuit 663 which drives second sensor part 141 and throttle drive
circuit 661 which drives throttle valve 17 is provided in sensor
actuator driving means 66. Throttle-integrated flow meter 20B is
arranged just before the branch part of the cylinders of the engine.
In addition, second sensor part 161 is arranged in the upstream
of throttle valve 17 and immediately after the air cleaner where
the pulsation influence is comparatively small. First sensor drive
circuit which drives first sensor part 161 is installed in sensor
actuator driving means 66 of control unit 60B.
It becomes possible to utilize the feature of each air flow meter
more effectively according to the configuration like this. It becomes
possible to detect suitably and correct the influence of the change
in flow rate of each cylinder by arranging the air flow meter just
before the cylinder.
Next, the whole configuration of an internal combustion engine
which installs the air flow meter according to the fourth embodiment
of the present invention will be explained by using FIG. 15.
FIG. 15 is a system configuration view showing the whole configuration
of an internal combustion engine which has the air flow meter according
to the fourth embodiment of the present. The same sign as FIG. 1
designates the same part.
In this embodiment, throttle-integrated flow meter 20 has the configuration
that sensor drive 66b is integrated in the throttle body shown in
FIG. 2 together with as actuators such as motors and sensors. The
same effect as each of the embodiments mentioned above can be achieved
even in this case though the positions of connecting wires are different.
Further, because the sensor with the minimum function is mounted,
the individual adjustment of the sensor can be easily done.
Next, the whole configuration of an internal combustion engine
which installs the air flow meter according to the fifth embodiment
of the present invention will be explained by using FIG. 16.
FIG. 16 is a system configuration view showing the whole configuration
of an internal combustion engine which has the air flow meter according
to the fifth embodiment of the present. The same sign as FIG. 1
designates the same part.
In this embodiment, engine controller 65 is provided outside, only
the part that controls the throttle and converts into the air flow
rate based on signals of sensors is integrated with throttle-integrated
flow meter 20.
In the configuration shown in FIG. 2 it might be influenced by
the turbulence of the noise etc. because the connection between
throttle-integrated flow meter 20 and controller 60 is made in general
with the wire harness etc. On the other hand, Because this embodiment
takes a strong configuration for the turbulence of the noise etc.,
it becomes possible to read an analog signal from the sensor with
a high degree of accuracy by the high-speed sampling. Further, it
is possible to transmit correctly the value converted into the air
flow rate once to engine controller 65 by using the digital communication
means. As mentioned above, it becomes possible to decrease the noise
etc. and to measure the air flow rate with a high degree of accuracy
according to this embodiment.
Next, the whole configuration of an internal combustion engine
which installs the air flow meter according to the sixth embodiment
of the present invention will be explained by using FIG. 17.
FIG. 17 is a system configuration view showing the whole configuration
of an internal combustion engine which has the air flow meter according
to the sixth embodiment of the present. The same sign as FIG. 1
designates the same part.
In this embodiment, the components including controller 60 are
integrated with throttle-integrated flow meter 20. The external
wiring (wire harness) between sensor and controller 65 needed in
the example of showing to FIG. 2 can be omitted by taking the configuration
like this. The communication delay by wire harness when the digital
communication means is used and the noise between devices, etc.
can be decreased by taking the configuration according to this embodiment.
Further, it becomes difficult to provide an electromagnetic noise
to the outside by integrating the whole and shielding it, and to
receive the influence from the outside. In addition, the manufacturing
cost can be decreased by not distributing the controllers, and integrating
them as a whole. Further, the part maker can support easily even
when something wrong is caused because the component-reduced configuration
includes the main components of the air intake system, and the quality
management can be done easily.
The error due to the backflow can be decreased according to the
present invention.
Further, the measurement error to the change of the opening of
the throttle valve can be decreased according to the present invention.
In addition, the operational state of the throttle device can be
diagnosed according to the present invention.
Further, the air flow rate of each of the cylinders can be detected
according to the present invention. |