Note: Descriptions are shown in the official language in which they were submitted.
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Title of the Invention
FUEL INJECTION QUANTITY CONTROL SYSTEM FOR
STARTING A TWO-CYCLE ENGINE
Background of the Invention
(1 ) Field of the Invention
The present invention relates to a system of controlling the fuel injection
quantity for starting a two-cycle engine, and particularly to a fuel injection
quantity control system which can effectively start a two-cycle engine such as
a s"o..."~ 'e engine to be used in cold climate conditions. After a failure in
starting the engine, the system optimizes a fuel injection quantity for securelyrestarting the engine.
(2) Description of the Related Art
Two-cycle engines for motorcycles and sl1o..,l, bi'vsl particularly those
used in cold climate conditions frequently employ a fuel supply system of
electronically controlled fuel injection type using a fuel injection valve. (Refer
to, for example, Japanese Unexamined Patent Publication No. 63-255543.)
This sort of system provides the intake manifold of each cylinder with a fuel
injection valve to simultaneously inject fuel to all cylinders.
The fuel injection quantity control system of electronically controlled fuel
injection type sets a slightly larger fuel injection quantity in starting a two-cycle
engine than in normally driving the engine, thereby easily starting the engine.
When an ignition switch is turned to a start position for cranking the
engine, the system controls the fuel injection valve to inject fuel in a quantity (a
fuel injection pulse width) expressed with the following equation:
TILN = TlLNTwK x KLN x KLT
where TILN is a fuel injection pulse width for starting the engine, TILNTwK a
basic fuel injection quantity for starting the engine, KLN a rotational speed
factor, and KLT a time factor.
The basic fuel injection quantity TILNTwK which differs depending on
engine temperature is stored in advance in a memory. The rotational speed
factor KLN changes depending on cranking speed. The time factor KLT
changes depending on cranking time.
As shown in Fig. 9, the time factor KLT is updated at a predetermined
interval of time (for example, 65 ms) by subtracting a predetermined value
LT from a last time factor KLT (1 at first).
Namely, the time factor KLT is successively updated accor~ing to KLT =
KLT - ~KLT and decl~asecl according to elapsing time as shown in Fig. 10.
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Figure 11 shows the problem of the above-mentioned fuel injection
quantity control system for starting a two-cycle engine. In the figure, the
engine was started and once driven to a complete combustion state.
Thereafter, due to a certain reason, a speed N of the engine dropped, and the
engine stalled. The engine was then restarted. In cold conditions, however,
the engine speed N hardly rose to fail restarting.
The reason of this failure is because the time factor KLT is newly set for
every starting operation, thereby setting a large time factor in correcting a fuel
injection quantity for restarting the engine. As a result, excessive fuel is
injected to the engine. Namely, the actual fuel injection quantity exceeds the
required fuel injection quantity of the engine, thereby setting an air-fuel ratio to
be too dense.
Summary of the Invention
In view of the problem of the conventional system, an object of the
invention is to securely restart an engine after a failure in starting the engine
by optimizing a correction factor of the fuel injection quantity according to
cranking time in such a way that the actual fuel injection quantity may not
exceed the required fuel injection quantity of the engine, and that an air-fuel
ratio may not be too dense.
To achieve the object, the invention provides, as shown in Fig. 1, a fuel
injection quantity control system for starting a two-cycle engine, comprising:
a fuel injection valve;
an engine operation detecting means including a start detecting means
for detecting the start of the engine according to the cranking operation of theengine, a cranking time detecting means for detecting cranking time, and an
engine temperature detecting means for detecting the engine temperature;
a basic injection quantity setting means for setting the basic fuel
injection quantity for starting the engine according to the engine temperature;
a time factor setting means for updating and setting, at predetermined
intervals, a time factor to be suitable for the cranking time by subtracting a
predetermined subtrahend from a last time factor;
a first subtrahend setting means for setting a first subtrahend to be
applied to the time factor;
a second subtrahend setting means for setting a second subtrahend
which is larger than the first subtrahend and to be applied to the time factor;
a start judging means for judging, when an engine start is detected,
whether it is a first engine start, or a second or later one;
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a selecting means for selecting the first subtrahend setting means when
the start judging means provides a signal indicating the first engine start, or
the second subtrahend setting means when the start judging means provides
a signal indicating the second or later engine start; and
an initial injection quantity calculating means for calculating an initial
fuel injection quantity according to the basic injection quantity provided by the
basic injection quantity setting means and a time factor prepared in the time
factor setting means, the time factor setting means preparing the time factor
according to a subtrahend which is provided by the selected one of the
subtrahend setting means.
In this way, the present invention employs two subtrahend setting
means for setting a subtrahend to be applied to a time factor for correcting thebasic fuel injection quantity according to a cranking time. In restarting the
engine, the invention selects one of the subtrahend setting means which
provides a larger subtrahend than the other which is used for starting the
engine for the first time. Based on the basic fuel injection quantity and the
time factor determined according to the subtrahend, the invention calculates a
fuel injection quantity for restarting the engine.
As mentioned above, the invention employs two subtrahend setting
means. To restart the engine, the invention corrects the basic fuel injection
quantity according to a subtrahend provided by one of the subtrahend setting
means which is larger than that provided by the other which is used for a first
engine starting operation. Even if the engine stalls due to a certain reason
after it started and reached a complete combustion state, the invention can
restart the engine with an actual fuel injection quantity not exceeding a
required fuel injection quantity and with an air-fuel ratio being not too dense. As a result, the invention can surely restart the engine, thereby
improving starting performance.
A fuel injection quantity for starting an engine is calculated by finding
TILN with a basic fuel injection quantity TILNTwK and a time factor KLT
according to the following equation:
TILN = TlLNTwK x KLT
The fuel injection quantity may be calculated not only by correcting the
basic fuel injection quantity TILNTwK with the time factor KLT but also by
correcting the basic fuel injection quantity with a rotational speed factor KLN
set by a rotational speed factor setting means according to a cranking speed.
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In this case, the fuel injection quantity for starting
an engine is calculated by finding TILN with the basic fuel
injection quantity Tl~NT~ time factor KLT' and rotational speed
factor KLN according to the following equation:
T -- T X K X K
ILN ILNTIIK LT LN
It is preferable to set the second subtrahend to be
applied to the time factor according to a period of time from
an engine stalling in a first start to restarting.
In this case, the second subtrahend ~KLT2 to be applied
to the time factor is calculated with a time period ~Tx from an
engine stalling at a first start to restarting according to the
following equation:
~KLT2 = (1/~TX) X K
where K is a matching value.
In this way, the second subtrahend to be applied to the
time factor is set according to the period of time from an
engine stalling in a first start to restarting, thereby
optimizing the subtrahend and fuel injection quantity which
will properly match a required fuel injection quantity.
The present invention will be explained in detail with
reference to embodiments and drawings. The embodiments will
help understand the invention more precisely. The invention,
however, is not limited to the embodiments but freely
modifiable within a scope of claims.
Brief Description of the Drawings
Fig. 1 is a functional block diagram showing an
arrangement of the invention;
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Fig. 2 is a system diagram showing an embodiment of the
invention;
Fig. 3 is a flowchart showing fuel injection quantity
control processes for starting an engine;
Fig. 4 is characteristic diagrams showing basic fuel
injection quantities for starting an engine, rotational speed
factors, and time factors;
Fig. 5 is a flowchart showing time factor setting
processes;
Fig. 6 is a time chart explaining effect of the time
factor setting processes (this Figure appears on the second
drawings page);
Fig. 7 is a time chart explaining time factor setting
control according to another embodiment (this Figure appears
on the second drawings page);
Fig. 8 is a flowchart showing the time factor setting
processes according to the another embodiment;
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Fig. 9 is a characteristic diagram showing a time factor setting
technique according to a prior art;
Fig. 10 is a time chart showing the time factor setting technique
according to the prior art; and
Fig. 11 is a time chart explaining the problem of the prior art.
Description of the Preferred Embodiments
Figure 2 shows a control system of a two-cycle engine employing an
electronically controlled fuel infection system according to an embodiment of
the invention. Intake air passes an air cleaner (not shown), a throttle valve 12interlocked with an accelerator, and an intake manifold 13, and enters the
engine 11.
The intake manifold 13 has a branch where a fuel injection valve 14 is
arranged for each cylinder. The fuel injection valve 14 is a solenoid type fuel
injection valve having a solenoid. When the solenoid is energized, the valve
opens, and when it is de-energized, the valve closes. A control unit 15
provides the solenoid with a driving pulse signal to open the valve. While the
valve is open, fuel which is pressurized by a fuel pump (not shown) and
adjusted to a predetermined pressure by a pressure regulator is injected into
the engine 11.
The control unit 15 receives output signals from various sensors serving
as engine operation detecting means, processes the input data with a built-in
~ic~uco~p-Jter, determines a fuel injection quantity (an injection time) Ti as
well as injection timing, and provides the valve 14 with the driving pulse
signal. The control unit 15 provides an ignition device 22 with an operation
control signal to control ignition timing. The microcomputer involves a central
pluces~ing unit, an input/output processor, memories, etc.
The sensors include an ignition switch 21 serving as a start detecting
means for detecting an engine start according to cranking operation of the
engine. An output signal of the ignition switch 21 is received by the control
unit 15. According to the output signal of the ignition switch 21, a timer
incorporated in the control unit 15 detects a cranking time, i.e., a period of time
during which the ignition switch is at a start position.
The sensors also include an airflow meter 16, which provides a signal
representing an intake airflow rate Q. A distributor (not shown) incorporates
an engine crank angle sensor 17 for outputting a reference signal every 120
degrees. By measuring a period of the reference signal, an engine speed can
be detected.
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The throttle valve 12 has a throttle sensor 18 of potentiometer type for
outputting a signal representing an aperture c~. The engine 11 has a water
jacket having a water temperature sensor 19. The sensor 19 serves as an
engine temperature detecting means and outputs a signal representing a
cooling water temperature Tw. The control unit 15 receives a voltage from a
power source battery 20 and detects a power source voltage VB.
Fuel injection control for starting an engine carried out by the
microcomputer of the control unit 15 will be explained with reference to a
flowchart of Fig. 3.
In Step 1 (indicated as S1 in the figure), the judging means of the
control unit 15 judges whether or not it is an engine starting operation
(whether or not the ignition switch is at the start position).
If it is the engine start, the flow proceeds to Step 2 in which the water
temperature sensor 19 detects a cooling water temperature Tw as an engine
temperature, and according to the detected temperature, a retrieving means of
the control unit 15 retrieves a basic fuel injection quantity TILNTwK stored in
advance in a ROM as shown in Fig. 4A.
Step 3 finds an engine speed N, and according to which, the retrieving
means of the control unit 15 retrieves a rotational speed factor KLN stored in
advance in the ROM as shown in Fig. 4B.
Step 4 finds a time factor KLT according to a table map of time factors
KLT stored in advance in the ROM according to a cranking time T as shown in
Fig. 4C, and a subtrahend provided by a subtrahend setting means to be
explained later.
Step 5 calculates a fuel injection pulse width TILN according to the
above-mentioned equation and controls the fuel injection valve 14 according
to the calculated pulse width.
If it is not the engine starting operation, the flow advances from Step 1
to Step 6 to normally control Ti.
The control unit 15 incorporates, as software, a time factor setting
means for updating and setting, at predetermined intervals, a time factor to be
suitable for a cranking time by subtracting a predetermined subtrahend from a
last time factor; a first subtrahend setting means for setting a first subtrahend to
be applied to the time factor; a second subtrahend setting means for setting a
second subtrahend which is larger than the first subtrahend and to be applied
to the time factor; a start judging means for judging, when the engine 11 is
started, whether it is a first engine start or a second or later one; and a
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selecting means for selecting the first subtrahend setting means when the start
judging means provides a signal indicating the first engine start, or the secondsubtrahend setting means when the start judging meas provides a signal
indicating the second or later engine start.
Operations of these means will be explained with reference to a time
factor setting routine of Fig. 5.
Step 11 judges whether or not the engine 11 is started for the second
time or afterward by judging whether or not the engine 11 is in a complete
combustion state. This step judges whether or not a rotational speed of the
engine 11 has once exceeded a set rotational speed before starting the
engine 11.
If the speed of the engine 11 has once exceeded the set speed, it is
judged to be a second or later engine starting operation to execute Step 12,
which sets a flag (F) to 1 and proceeds to Step 13. If the speed of the engine
11 has not exceeded the set rotational speed, it is judged to be a first engine
starting operation, and the flow directly proceeds to Step 13.
Step 13 judges whether or not the engine is in a stalled state (the
engine is not operating). If the engine is in the stalled state, Step 14 sets the
time factor KLT to an initial value 1, and proceeds to Step 15, which judges
whether or not the flag (F) is 1. If the flag (F) is not 1, the flow proceeds to Step
16. Step 16 selects a first subtrahend AKLT1 as a subtrahend ~KLT to be
applied to the time factor and goes to RETURN. If the flag (F) is 1, Step 17
selects a second subtrahend ~KLT2 which is larger than the first subtrahend
~KLT1~ as the subtrahend ~KLT to be applied to the time factor and goes to
RETURN.
If Step 13 judges that the engine is operating, Step 18 successively
updates and sets KLT according to the time factor KLT read out of the table
map of time factors KLT stored in advance in the ROM as shown in Fig. 4C,
and according to the first subtrahend AKLT1 or the second subtrahend AKLT2.
Namely, at a predetermined interval of time (for example, 65 ms), the
subtrahend ~LT (~KLT1 or ~KLT2) is subtracted from a last value KLT (initially
1), thereby updating and setting KLT.
Namely, KLT= KLT-~KLTis calculated to successively update and set
KLT. Thereafter, the process goes to RETURN.
In Fig. 3, Step 2 corresponds to the basic injection quantity setting
means, Step 3 to the rotational speed factor setting means, Step 4 to the time
factor setting means, and Step 5 to the initial injection quantity calculating
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means. In Fig. 5, Step 11 corresponds to the start judging means, Step 15 to
the selecting means, Step 16 to the first subtrahend setting meas, Step 17 to
the second subtrahend setting means, and Step 18 to the time factor setting
means.
For starting the engine 11, the above arrangement has the two
subtrahend setting means for setting a subtrahend to be applied to a time
factor for correcting a basic fuel injection quantity according to a cranking time.
To restart the engine, the embodiment selects one of the subtrahend setting
means which provides a larger subtrahend than the other which is used for
starting the engine for the first time. According to the basic fuel injection
quantity and a time factor to be set according to the selected subtrahend, an
actual fuel injection quantity for restarting the engine is calculated.
In this way, the two subtrahend setting means are provided. To restart
the engine, the subtrahend setting means which provides the larger
subtrahend than the other used for a first engine starting operation is
employed to correct the basic fuel injection quantity. If the engine 11 stalls
due to a certain reason after it started and reached a complete combustion
state, the engine must be restarted. In this case, an actual fuel injection
quantity will never exceed a required fuel injection quantity of the engine, andan air-fuel ratio will never be too dense.
As a result, the restarting operation can surely drive the engine as
shown in Fig. 6, thereby improving starting performance.
The above embodiment finds the fuel injection quantity for starting the
engine by correcting the basic fuel injection quantity with the time factor as
well as with the rotational speed factor which is set by the rotational speed
factor setting means according to a cranking speed. The fuel injection
quantity for starting the engine may be calculated by finding TlLN with the
basic fuel injection quantity TILNTwK and time factor KLT according to the
following equation:
TILN = TlLNTwK x KLT
Another embodiment of the invention will be explained.
This embodiment determines a second subtrahend ~KLT2 according to
a period of time from an engine stalling in a first engine starting operation torestarting, i.e., an engine stall period ~Tx.
In this case, the second subtrahend ~KLT2 corresponding to the time
period from an engine stalling in a first engine starting operation to restarting
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(the engine stall period) ~TX shown in Fig. 7 is calculated according to the
following equation:
~ KLT2 = (1/~TX) x K
where K is a matching value.
A routine of this embodiment for setting the time factor is shown in a
flowchart of Fig. 8. Steps 21 to 26, and 30 of this el"Lodi",er,l correspond to
Steps 11 to 16, and 18 of Fig. 5. Steps 25 and 28 are peculiar to this
embodiment.
Step 25 judges whether or not the flag (F) is 1. If the flag (F) is not 1,
Step 26 selects the first subtrahend ~KLT1 as the ~KLT. If the flag (F) is 1,
Step 27 counts ~TX with a timer incorporated in the control unit 15, and Step
28 calculates ~KLT2 = (1/~TX) x K to set the second subtrahend ~KLT2
This embodiment increases the second subtrahend ~KLT2 when the
engine stall period ~TX is short, and decreases the second subtrahend ~KLT2
when the engine stall period ~TX is long, thereby optimally adjusting the
second subtrahend ~KLT2 according to the engine stall period ~Tx. This
arrangement provides an optimum fuel injection quantity matching with a
required fuel injection quantity, thereby securely restarting the engine.
The fuel injection quantity control system according to the embodiments
of the invention is particularly applicable for starting two-cycle engines such
as snowmobiles which are used in cold climate conditions. snowmobiles, etc.
will benefit greatly from such an invention by being able to operate safely and
continuously on snowy road conditions.
