Background of the Invention:
[0001] The present invention relates to a fuel injection controlling method for an internal
combustion engine, and more particularly to a fuel injection controlling method for
an internal combustion engine for automobiles using a hot wire air flow meter wherein
the rate of fuel injection ¡ can be adjusted during acceleration.
[0002] Conventional acceleration adjustment in fuel injection devices of the internal combustion
engine for automobiles has been provided the valve opening pulse generating means
for the fuel increment independently of the basic valve opening pulse for causing
the injectors to inject fuel normally during the normal condition, and the valve opening
pulse for the fuel increment is determined the duration dependent on the water temperature
of the internal combustion engine. (Japanese Patent Laid Open Publication No. 5841/
1984).
[0003] However, the above acceleration adjustment in fuel injection devices has not provided
fine adjustment of the fuel increment pulse depending on the state of a running engine
excepting the water temperature.
[0004] The above electronic fuel injector (MPI system) employs a vane air flow meter. Therefore,
it can not abruptly increase the rate of air intake into an engine during acceleration.
From this reason, a relatively rich mixture is supplied at the beginning of acceleration.
[0005] However, because an inherent delay exists in air intake into the engine, it has been
impossible to achieve abrupt acceleration. On the rapid acceleration from idling to
the fully open state under no load, the speeded up revolution time (To) is about 200
ms (confer Fig. 4). i
[0006] Besides, a hot wire air flow meter employed in the air flow meter requires fine adjustment
during acceleration, because it includes no member interrupting air intake as seen
in the vane type air flow meter; hence, it causes an instantaneous flow of air into
the engine.
[0007] The hot wire air flow meter which detects the volume of air is advantageous in that
it allows air to be supplied to the engine more rapidly during acceleration because
it has no throttle component. It does, however, have the problem of delayed fuel feed,
that is, a lag in response time. This delay in fuel feed response time requires fine
adjustment based on acceleration and other parameters.
Summary of the Invention:
[0008] An object of the present invention is to provide a fuel injection controlling method
for an internal combustion engine wherein optimal acceleration characteristics can
be obtained.
[0009] Another object of the present invention is to provide a fuel injection controlling
method for an internal combustion engine wherein fuel increment depending on the state
of a running engine excepting the water temperature can be adjusted.
[0010] Another object of the present invention is to provide a fuel injection controlling
method for an internal com- bustion engine wherein delayed fuel feed can be adjusted.
[0011] Another object of the present invention is to provide a fuel injection controlling
method for an internal combustion engine wherein acceleration matching between the
state after deceleration and the state after normal becomes possible.
[0012] Another object of the present invention is to provide a fuel injection controlling
method for an internal combustion engine wherein speed up revolution time of acceleration
from idling to the fully open state under no load can be shortened.
[0013] Another object of the present invention is to provide a fuel injection controlling
method for an internal combustion engine wherein inadequate acceleration during rapid
acceleration uhich is to be effected after fuel reduction for deceleration can be
improved.
[0014] The present invention is to provide a fuel injection control method for internal
combustion engines including the steps of: controlling the opening time of fuel injector
in accordance with the control content previously programmed based on various operational
parameters including air intake volume, the number of revolutions and temperature
of the engine; measuring the air intake volume by a hot wire air flow meter; generating
a signal of an idle switch for detecting a closed state of a throttle valve adapted
to control the intake air amount; and generating a valve opening pulse for fuel increment
independent of a basic valve opening pulse which causes the injector to inject fuel
normally during the normal condition; and is characterized in that the duration of
the valve opening pulse for a fuel increment is controlled dependent on at least one
of selected from variations in the air intake volume per unit time, a closing signal
for the throttle valve, a signal indicating the number of revolutions of the internal
combustion engine, etc., and independent of the duration of the basic valve opening
pulse.
[0015] It is possible to obtain optimum acceleration by varying the adjustment depending
on conditions for interrupt adjustment during acceleration. Further, by applying the
judgement of conditions for adjustment after fuel reduction for deceleration, it has
become possible to acceleration matching between the state after deceleration and
the state after normal operation.
Brief Description of the Drawings:
[0016]
Fig. 1 is an engine system view for embodying the present invention.
Fig. 2 is a block diagram view showing the relationship between input and output described
in Fig. 1.
Fig. 3 is an explanatory view of engine injection timing.
Fig. 4 is an explanatory graph of experimental results of speed up revolution times
respectively according to both the present invention and the prior art.
Fig. 5 is an explanatory flow chart sheet for realizing the acceleration adjusting
method of the present invention.
Detailed Description of the Preferred Embodiments:
[0017] One embodiment of the present invention will be described. Fig. 1 shows an engine
system to which the present invention is applied. An engine 1 has intake pipes 2 which
are provided with the fuel injection valves (injectors) 3 corresponding to the number
of cylinders. These intake pipes 2 are brought into a single pipe at a collector 4
in the upstream side, and have a throttle valve 5 for determining the amount of intake
for the engine further upstream.
[0018] Such an amount of intake for the engine 1 is measured by a hot wire air flow meter
6 provided still further upstream. Engine revolutions are counted by a revolution
sensor 13. In addition to the above, a control unit CU 12 also receives a signal 11
from engine temperature, an exhaust gas signal from an oxygen concentration measuring
sensor 10, and a signal from an idle switch li, etc.
[0019] Fuel is supplied to the engine 1 by opening a valve on each of the fuel injector
3, and the amount of fuel is measured based on valve opening time. Fuel is pressurized
and regulated by a fuel pump 8 and a regulator 9.
[0020] Fig. 2 is a block diagram showing the relationship between input and output depicted
in Fig. 1. With respect to a control unit CU, the left side includes sensors and the
right side includes actuators.
[0021] In the control unit CU, wave shaping circuits and AD converters are arranged on the
left side, an I/O LSI section for implementing therein exchange of input/output and
arithmetic processing and a CPU for giving instructions to the I/O LSI section are
at the center, and a circuit for driving the output actuators on the right side.
[0022] Next, injection timing, for example in a 4-cylinder, 4-cycle engine, will be described
with reference to Fig. 3. In the 4-cylinder, 4-cycle engine, fuel is usually injected
once per revolution, i.e., at the timing of A and C, for all four cylinders.
[0023] The sections A and C are respectively the basic valve opening pulses for causing
the injector to inject fuel normally during the normal condition.
[0024] A fuel increment pulse (interrupt pulse) described in the present invention is a
pulse shown in the section of B which is generated immediately upon detection of acceleration,
so as to inject fuel at that time.
[0025] In the present invention, acceleration may be detected based on, for example, an
ON → OFF signal of the idle switch 14 or a closing signal of the idle switch 14 indicating
that a throttle valve 5 has been opened from an idle state, and the rate of variation
(AQa) of the air intake volume Qa per unit time. The magnitude of acceleration can
be detected based on the value (AQa/Qa) of the rate of variation of the air intake
volume Qa during a predetermined time (Δt).
[0026] Table 1 shows an example of setting the fuel increment pulse (interrupt pulse) to
a running vehicle in response to the magnitude of acceleration.

[0027] By way of example, the process after acceleration is divided depending on the condition
before acceleration. More specifically, after reducing fuel feed during deceleration,
a large amount of fuel must be supplied to compensate for drying-up in the intake
system during fuel reduction. Also after the normal condition, adjusting acceleration
requires changes to correspond to the fully closed state of the throttle valve and
other states thereof.
[0028] Further, acceleration is detected as a combination of the rate of variation (AQa)
in the air intake volume per unit time and the idle switch setting. In the Table 1,
the "after idling" indicates an interrupt pulse based on detection of acceleration
using the idle switch.
[0029] The reason for detecting acceleration based on both the idle switch and the rate
of variation (AQa) in the air intake volume per unit time is in that detection with
the idle switch always occurs earlier than detection with the rate of variation (AQa)
in the air intake volume per unit time. Experiments have shown that this is attributable
to a delay in the intake system accompanying detection of the rate of variation (AQa)
in the air intake volume per unit time. Though this delay is relatively short, it
is still longer than that accompanying the opening of the throttle valve.
[0030] Description will now be made by referring to typical examples of the respective cases.
The interrupt pulse based on the rate of variation (AQa) in the air intake volume
per unit time after fuel cutdown for deceleration will be described.
[0031] First, after fuel reduction for deceleration, the process is divided into slow acceleration
(under light load. 5%<A
Qa<37.5%) and rapid acceleration (ΔQa≧37.5%). For slow acceleration, an interrupt pulse
of 3 ms is generated; for rapid acceleration, interrupt pulses of 9 ms are generated,
(one for each detected acceleration rate).
[0032] The magnitudes of the above interrupt pulses are set preferably to have about 1.5-5
ms duration for slow acceleration and to have about 6-12 ms duration for rapid acceleration,
respectively.
[0033] An interrupt pulse based on the idle switch is set to , have, by way of example,
a relatively long duration of 9 ms. The magnitude of the above interrupt pulse by
the after idling is set preferably to have about 6-12 ms duration.
[0034] An interrupt pulse based on the rate of variation (AQa) in the air take volume per
unit time in normal condition is set to have a 3 ms duration for slow acceleration
(5%<AQa< 10%) and is set to have a 6 ms duration for rapid acceleration (ΔQa≧10%)
respectively, and the fuel is injected. The magnitutes of the above interrupt pulses
are set preferably to have about 1.5-5 ms duration for slow acceleration and to have
above 4-8 ms duration for rapid acceleration, respectively.
[0035] After the normal condition the idle switch is turned on, because the intake pipe
does not dry as much as before, an interrupt pulse based on the idle switch may be
set to a shorter duration, e.g., 3 ms, than that during deceleration. The magnitude
of the above interrupt pulse is set preferably to have 1.5-5 ms duration.
[0036] Moreover, in acceleration from the state where the idle switch is turned off, i.e.,
the throttle valve is in an open state, better conditions exist in comparison with
acceleration from a closed state of the throttle valve, in that the mixture in the
intake pipe is more uniform, whereby acceleration adjustment based on the idle switch
is not required.
[0037] Fig. 4 shows the experimental results obtained from application of the above-mentioned
adjustment. The graph of Fig. 4 represents an example of rapid acceleration from idling
to the fully open state under no load. It is evident from Fig. 4 that, as a result
of adjusting with the additional interrupt pulses during acceleration, revolution
time is speeded up from To of about 200 ms in the prior art to T of about 120 ms in
the present invention.
[0038] Fig. 5 shows a flow chart sheet for realizing the adjustment described in connection
with Table 1..First, in acceleration after the normal condition, the process flow
passes the right-hand loop. When the rate of variation of the air take volume per
unit time (AQa) is smaller than A1, no interrupt pulse is generated; when AQa is greater
than A1, an interrupt pulse TA1 is issued. Note that, although inherently a decision
must be made based on the inequality of A'
1 > ΔQa > A"
1 so that the additional pulse may be divided into interrupt pulses TA1' (of 6 ms in
Table 1) and TA1" (of 3 ms in Table 1), this process has been omitted from the flow
chart in all the following associated flow.
[0039] Next, in the central loop representing acceleration from idling, an interrupt pulse
TA2 (3 ms) due to the condition after idling is set and thereafter an interrupt pulse
TA3, also herein inherently divided into two types.-interrupt pulses TA3', 3 ms in
Table 1, and TA3", 6 ms in Table 1 - is set based on ΔQa.
[0040] The left-hand loop represents acceleration from the decelerated state. In this case,
an interrupt pulse TA4 (9 ms) is issued due to the state after idling and acceleration
is then determined on the basis of AQa. If A5 > AQa > A6, an interrupt pulse TA6 (3
ms) is issued and adjustment is completed therewith.
[0041] In all these adjustments the interrupt pulse based on ΔQa is generated only once
for each acceleration; therefore, tests on a running engine have revealed the problem
of inadequate acceleration during rapid acceleration which is to be effected after
fuel reduction for deceleration.
[0042] The present invention is to overcome this problem. Namely, when AQa > A5, an interrupt
pulse TA5 is set.
[0043] The fact that the pulse TAS has been issued is stored in memory, thus making it possible
to repeat the adjustment with the interrupt pulse TA5 based on ΔQa > A5 only on the
above condition.
Claim 1. A fuel injection control method for internal combustion engines including
the steps of:
- controlling the opening time of fuel injector in accordance with the control content
previously programmed based on various operational parameters including air intake
volume, the number of revolutions and temperature of the engine;
- measuring the air intake volume by a hot wire air flow meter; i
- generating a signal of an idle switch for detecting a closed state of a throttle
valve adapted to control the intake air amount; and
- generating a valve opening pulse for fuel increment independent of a basic valve
opening pulse which causes the injector to inject fuel normally during the normal
condition; characterized in that
the duration of said valve opening pulse for fuel increment is controlled dependent
on at least one of parameters selected from variations in the air intake volume per
unit time, a closing signal for the throttle valve, a signal indicating the number
of revolutions of the internal combustion engine, etc., and independent of the duration
of said basic valve opening pulse.
Claim 2 A fuel injection control method for internal combustion engines according
to claim 1, characterized in that said valve opening pulse for fuel increment is generated
immediately upon a detected acceleration so as to inject the fuel at that time.
Claim 3 A fuel injection control method for internal combustion engines according
to claim 2, characterized in that the acceleration is detected based on the signal
representing the closed state of the idle switch or based on the rate of variation
of the air intake volume.
Claim 4 A fuel injection control method for internal combustion engines according
to claim 2, characterized in that after fuel reduction for acceleration, said valve
opening pulse for fuel increment is different at slow acceleration condition and at
rapid acceleration condition respectively.
Claim 5 A fuel injection control method for internal combustion engines according
to claim 4, characterized in that at the slow acceleration condition, the amount of
injected fuel is increased by said valve opening pulse for fuel increment generated
upon the acceleration detectea on the basis of the idle switch and upon the acceleration
detected on the basis of the rate of variation in the air intake volume per unit time.
Claim 6. A fuel injection control method for internal combustion engines according
to claim 4, characterized in that at rapid acceleration condition, the amount of injected
fuel is increased by said valve opening pulse for fuel increment generated upon the
acceleration detected on the basis of the idle switch and upon the acceleration detected
on the basis of the rate of variation in the air intake volume per unit time.
Claim 7. A fuel injection control method for internal combustion engines according
to claim 2, characterized in that at off condition of the idle switch in the normal
condition, the fuel is increased by said valve opening pulse for fuel increment generated
from the acceleration detected on the basis of the rate of variation in the air intake
volume per unit.
Claim 8. A fuel injection controlling method for an internal combustion engine according
to claim 2, characterized in that on "on" condition of the idle switch in the normal
condition, the fuel is increased by said valve opening pulse for a fuel increment
generated from the acceleration detecting being based on the idle switch and generated
from the acceleration detecting being based on the rate of variation in the air intake
volume per unit time.