Method of controlling fuel injection apparatus for internal combustion engines

The present invention is a method of controlling a fuel injection apparatus for an internal combustion engine, and is capable of preventing the breakage of a component which is exposed to high-temperatures, such as an exhaust manifold. To this end, a first set temperature and a second set temperature, higher than the first set temperature, are set in advance, and a temperature of exhaust gas from an internal combustion engine (1) is detected. The number of occasions at which the temperature of the exhaust gas exceeds the first set temperature and the lengths of time during which the temperature of the exhaust gas has exceeded the second set temperature are totaled respectively, and either when the total number of occasions exceeds a predetermined number of occasions or when the total of the lengths of time exceeds a predetermined length, at least one of the following actions are taken: giving an alarm, reducing a fuel injection rate and changing the injection timing.

TECHNICAL FIELD 
The present invention relates to a method of controlling a fuel injection 
apparatus for an internal combustion engine, and particularly to a method 
of controlling a fuel injection apparatus for an internal combustion 
engine which prevents the breakage of an exhaust manifold and the like as 
a result of high-temperatures. 
BACKGROUND ART 
Conventionally, various kinds of methods of controlling fuel injection 
apparatuses for internal combustion engines have been proposed. Of these 
methods, a method of controlling a fuel injection apparatus, by detecting 
a temperature of the exhaust gas with a temperature sensor, is disclosed 
in Japanese Patent Application Laid-open No. 3-505115. According to this 
method, one terminal end of a thermometer extends into an exhaust 
manifold. A temperature sensor is connected thereto by being embedded in 
an electronic unit type of a control unit. The control unit converts an 
extremely weak electric signal from the temperature sensor into a pulse 
width modulated output signal, and outputs the signal to an electronic 
fuel injection apparatus. The output signal has a duty cycle, which 
increases as the temperature of the exhaust gas increases when the 
increase exceeds a certain level. 
The structure described above relates to a control that provides a cooling 
medium only when there is an actual need for cooling. However, many 
internal combustion engines, which are used in construction machinery or 
the like, are often used at full power, and the temperature of the exhaust 
gas frequently increases. Especially in a location with an atmosphere of 
high temperature, this tendency becomes more noticeable. The exhaust 
manifolds of the internal combustion engines used in such a place often 
break. As a result, the construction machinery is stopped, and the 
operation is stopped, thereby causing a disadvantage that a great loss 
occurs due to the delayed completion of the construction or the like. 
DISCLOSURE OF THE INVENTION 
The present invention is made to eliminate the above-described 
disadvantages of the conventional art, and its object is to provide an 
improvement of a method of controlling a fuel injection apparatus for an 
internal combustion engine that is capable of preventing the breakage of a 
component exposed to high-temperatures, such as an exhaust manifold, and 
which gives an alarm in order to keep the operation going. 
A method of controlling a fuel injection apparatus for an internal 
combustion engine relating to the present invention is characterized by 
including the steps of: 
previously setting a first set temperature and a second set temperature, 
which is higher than the first set temperature, 
detecting a temperature of the exhaust gas discharged from the internal 
combustion engine, 
respectively totaling the number of occasions at which the temperature of 
the exhaust gas exceeds the first set temperature, and the lengths of time 
during which the temperature of the exhaust gas has exceeded the second 
set temperature, and 
either when the total number of occasions exceeds a predetermined number of 
occasions, or when the total of the length of time exceeds a predetermined 
length, taking at least one of the following actions: giving an alarm, 
reducing a fuel injection rate, and changing the fuel injection timing. 
According to the structure described above, when the number of occasions, 
at which the temperature of the exhaust gas exceeds the first set 
temperature, exceeds a predetermined value, or when the total of the 
lengths of time, during which the temperature of the exhaust gas has 
exceeded the second set temperature, exceeds a predetermined value, the 
fuel injection rate is restricted, for example, with an alarm being given; 
therefore, unexpected breakage of the exhaust manifold or the like, which 
is caused by high-temperatures of the exhaust gas can be prevented. In 
addition, after an alarm is given, an operation can be carried out even if 
the fuel injection rate is restricted; therefore, there is less delay in 
completion of the construction. The breakage of an exhaust manifold or the 
like can be also prevented by changing the injection timing.

BEST MODE FOR CARRYING OUT THE INVENTION 
A preferred embodiment of a method of controlling a fuel injection 
apparatus of internal combustion engines according to the present 
invention will be particularly described below with reference to the 
attached drawings. 
In FIG. 1, a fuel injection apparatus 2 such as an electronic governor, 
which supplies each cylinder with fuel, is attached to an internal 
combustion engine 1. The fuel injection apparatus 2 is connected to a 
control apparatus 3 such as a controller, and receives a command of the 
fuel injection rate which the internal combustion engine 1 supplies to 
each cylinder. A temperature sensor 5, which is attached to an exhaust 
manifold 4 of the internal combustion engine 1, is connected to the 
control apparatus 3. The temperature sensor 5 measures the temperature of 
the exhaust manifold 4, and outputs the measured value to the control 
apparatus 3. The fuel injection apparatus 2 includes an electromagnetic 
flow control valve 2a, which controls the fuel injection rate, and a 
solenoid valve 2b, which regulates the fuel injection timing, and each 
valve is actuated by a respective command from the control apparatus 3. It 
should be mentioned that the fuel injection apparatus 2 can include either 
the valve 2a or the valve 2b, which is actuated by a command from the 
control apparatus 3. 
The operation of the structure described above will be explained. When an 
operation is carried out with construction machinery or the like, an 
operator usually presses the accelerator pedal fully, and an operation is 
frequently carried out at full power. As a result, the temperature of the 
exhaust gas rises and changes, for example, as in FIG. 2. In FIG. 2, a 
temperature T of an exhaust gas is shown by the axis of ordinate, and a 
time S is shown by the axis of abscissa. For the exhaust gas temperature 
T, a first set temperature Ta, and a second set temperature Th which is 
higher than the first set temperature Ta are set. The first set 
temperature Ta is set at a temperature which causes thermal fatigue, and 
the second set temperature Th is set at a temperature which causes 
breakage by oxidation. 
As for thermal fatigue, the number of occasions at which the temperature of 
the exhaust gas exceeds the first set temperature Ta is memorized and 
recorded. At each occation when the temperature T of the exhaust gas 
exceeds the first set temperature Ta, then falls to a point less than the 
first set temperature Ta, and then exceeds the first set temperature Ta 
once again, the time period during which the temperature is below the 
first set temperature Ta is measured. When the measured time period does 
not exceed a predetermined time period Sa, the measured time period is not 
recorded as one of the number of occasions even if the temperature exceeds 
the first set temperature Ta once again. A time period which does not 
exceed the predetermined time period Sa is shown by .DELTA.Sn. 
As for the breakage by oxidation, the lengths of a time period, during 
which the temperature has exceeded the second set temperature Th, is 
memorized in the control device 3 and is recorded. However, the length of 
a time period, during which the temperature of the exhaust gas has 
exceeded the second set temperature Th, is recorded only when that length 
of the time period exceeds the length of a predetermined time period Sh 
(Shn in FIG. 2, n=1, 2); and when the length of the time period does not 
exceed the length of the predetermined time period Sh (for example, when 
the length of the measured time period is .DELTA.Shn in FIG. 2), the 
length of the measured time period is not recorded. 
Next, the operation will be explained with reference to the flow chart in 
FIG. 3. 
In Step 1, the temperature T of the exhaust gas is measured by the 
temperature sensor 5. In Step 2, it is determined whether the temperature 
T of the exhaust gas exceeds the first set temperature Ta. When the 
temperature T of the exhaust gas does not exceed the first set temperature 
Ta, the flow returns to Step 1 and the temperature T of the exhaust gas is 
measured continuously. On the other hand, when the temperature T of the 
exhaust gas exceeds the first set temperature Ta, the flow proceeds to 
Step 3, and the control apparatus 3 starts measuring the time S. Next, the 
flow proceeds to Step 4, and it is determined whether or not the 
temperature T of the exhaust gas exceeds the second set temperature Th. 
When the temperature T of the exhaust gas does not exceed the second set 
temperature Th, the flow proceeds to Step 5. 
In Step 5, it is determined whether the temperature T of the exhaust gas 
falls below the first set temperature Ta. When the temperature T of the 
exhaust gas does not fall below the first set temperature Ta, the flow 
returns to step 1, and the temperature T of the exhaust gas and the length 
of time are continued to be measured. On the other hand, when the 
temperature T of the exhaust gas falls below the first set temperature Ta, 
the flow proceeds to Step 6, and it is determined whether the length of 
the time period during which the temperature T of the exhaust gas is below 
the first set temperature Ta exceeds the length of the predetermined time 
period Sa. When the length of the time period does not exceed the length 
of the predetermined time period Sa, the flow returns to Step 1 without 
recording the length of that time period as one of the number of 
occasions, and the temperature T of the exhaust gas is measured. On the 
other hand, when the length of the time period exceeds the length of the 
predetermined time period Sa, the flow proceeds to Step 7, and the length 
of the time period is recorded as one of the number of occasions to obtain 
a total number of occasions Sn. 
In Step 8, it is determined whether the number of occasions, at which the 
temperature T of the exhaust gas exceeds the first set temperature Ta, 
exceeds a predetermined total number of occasions .SIGMA. Sn. When the 
number of occasions exceeds the predetermined total number of occasions 
.SIGMA. Sn, one of the following actions is taken in Step 9: giving an 
alarm, reducing a fuel injection rate, and changing the injection timing. 
Incidentally, it is preferable to combine the action of giving an alarm 
with the action of reducing a fuel injection rate or with the action of 
changing the injection timing. When the number of occasions does not 
exceed the predetermined total number of occasions .SIGMA. Sn in Step 8, 
the flow returns to Step 1, and the temperature T of the exhaust gas is 
measured. 
When the temperature T of the exhaust gas exceeds the second set 
temperature Th in Step 4, the flow proceeds to Step 10, and the control 
apparatus 3 starts measuring the length of the time period during which 
the temperature T of the exhaust gas has exceeded the second set 
temperature Th. Next, the flow proceeds to Step 11, and it is determined 
whether the temperature T of the exhaust gas falls below the second set 
temperature Th. When the temperature T of the exhaust gas does not fall 
below the second set temperature Th, the action in Step 11 is repeated to 
measure the temperature T of the exhaust gas and to continue to measure 
the length of the time period. When the temperature T of the exhaust gas 
falls below the second set temperature Th, the flow proceeds to Step 12, 
and it is determined whether the length of the measured time period 
exceeds the length of a predetermined time period Sh. When the length of 
the measured time period does not exceed the length of the predetermined 
time period Sh (when the length of the measured time period is .DELTA.Shn 
in FIG. 2), the length of that measured time period is not recorded, and 
the flow returns to Step 1 to measure the temperature T of the exhaust 
gas. On the other hand, when the length of measured time period exceeds 
the length of the predetermined time period Sh, the flow proceeds to Step 
13, and the length of that measured time Shn period (n=1, 2 . . . ) is 
recorded to obtain the total of the recorded lengths of time (Sh1+Sh2 . . 
. ). 
In Step 14, it is determined whether the total of the recorded lengths of 
time (Sh1+Sh2 . . . ) exceeds a predetermined total length of time .SIGMA. 
Shn. When the total of the recorded lengths of time exceeds the 
predetermined total length of time .SIGMA. Shn, at least one of the 
following actions is taken in Step 15 as in Step 9: giving an alarm, 
reducing a fuel injection rate, and changing the fuel injection timing. 
When the total of the recorded lengths of time does not exceed the 
predetermined total length of time (.SIGMA. Shn) in Step 15, the flow 
returns to Step 1 to measure the temperature T of the exhaust gas. 
INDUSTRIAL AVAILABILITY 
The present invention is useful as a method of controlling a fuel injection 
apparatus for internal combustion engines, which prevents an unexpected 
breakage of an exhaust manifold or the like, so that the construction 
machinery is not stopped by a breakdown, since a fuel injection rate is 
restricted and an alarm is given when the number of occasions at which the 
temperature of the exhaust gas exceeds a set temperature exceeds a 
predetermined number of occasions, or when the total length of time during 
which the temperature of the exhaust gas has exceeded a set temperature 
exceeds a predetermined length.