JPH0252102B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a method for controlling fuel supply during high-load operation of an internal combustion engine, and in particular to a method for controlling the fuel supply of an internal combustion engine during high-load operation under low atmospheric pressure conditions such as at high altitudes. The present invention relates to a fuel supply control method that achieves

Technical background of the invention and its problems During high-load operation of the engine, where the absolute pressure in the intake pipe, which indicates the load state of the engine, is above a predetermined determination value, the air-fuel mixture to the engine is enriched to obtain high output, and the mixture is placed in the exhaust passage. A fuel supply control method that prevents an excessive rise in the temperature of the catalyst bed of an exhaust purification device using a catalyst system, etc.
No. 57-161413.

In such a fuel supply control method, when the engine is operated under low atmospheric pressure conditions such as at high altitudes, the absolute pressure in the intake pipe during high-load operation when the throttle valve is fully opened due to the decrease in atmospheric pressure also decreases. Therefore, if the predetermined judgment value is set under standard atmospheric pressure conditions such as when driving on flat ground, the absolute pressure in the intake pipe will decrease even though the engine is in an operating state that should enrich the air-fuel mixture during high-load operation during high-altitude driving. If the value falls below the predetermined determination value, the mixture will not be enriched, which will adversely affect driving performance. Furthermore, if the air-fuel mixture is not enriched when the engine is operating under a high load during high-altitude operation, the temperature of the catalyst bed of the exhaust gas purification device will rise excessively, and the life of the catalyst bed will be adversely affected.

SUMMARY OF THE INVENTION The present invention has been made to avoid such inconveniences, and is a fuel supply control method for an internal combustion engine equipped with an intake passage and a throttle valve disposed in the middle of the passage, in which atmospheric pressure is detected, The engine rotational speed is detected, and a pressure discrimination value on the downstream side of the throttle valve in the intake passage is determined according to the detected atmospheric pressure value, and the detected engine rotational value is further increased based on the intake passage pressure discrimination value. to be set to a value on the lower load side depending on the
The downstream pressure of the throttle valve in the intake passage is detected, the detected intake passage pressure value is compared with the intake passage pressure discrimination value, and the intake passage pressure detection value is determined as the intake passage pressure discrimination value. The present invention provides a fuel supply control method during high-load operation of an internal combustion engine, which is characterized by increasing the amount of fuel supplied to the engine when the value is on the high-load side.

Embodiments of the Invention Examples of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is an overall configuration diagram of a fuel supply control device for an internal combustion engine to which the method of the present invention is applied. Reference numeral 1 indicates, for example, a four-cylinder internal combustion engine, an intake pipe 2 is connected to the engine 1, and the intake pipe 2 is A throttle valve 3 is provided in the middle of the pipe 2. A throttle valve opening sensor 4 is connected to the throttle valve 3, which converts the opening of the throttle valve into an electrical signal and controls the electronic control unit (hereinafter referred to as "ECU").
It is set to be sent to 5th.

A fuel injection valve 6 is provided in the intake pipe 2 between the engine 1 and the throttle valve 3. This fuel injection valve 6 is provided for each cylinder slightly upstream of an intake valve (not shown) in the intake pipe 2, and each injection valve is connected to a fuel pump (not shown) and is connected to an ECU 5.
The valve opening time of the fuel injection valve is controlled by a signal from the ECU 5.

On the other hand, an absolute pressure sensor 8 is provided immediately downstream of the throttle valve 3 via a pipe 7, and the absolute pressure signal exchanged into an electrical signal by the absolute pressure sensor 8 is sent to the ECU 5.

The engine body 1 is provided with an engine water temperature sensor 10, which is made of a thermistor or the like, is inserted into the circumferential wall of the engine cylinder filled with cooling water, and supplies its detected water temperature signal to the ECU 5.

An engine rotation speed sensor (hereinafter referred to as "Ne sensor") 11 is installed around the camshaft or crankshaft (not shown) of the engine.
It outputs one pulse at a predetermined crank angle position every 180° rotation, and this pulse is sent to the ECU 5. A three-way catalyst 14 is arranged in the exhaust pipe 13 of the engine 1, and performs a purifying action on HC, CO, and NOx components in the exhaust gas. An O ₂ sensor 15 is inserted into the exhaust pipe 13 on the upstream side of the three-way catalyst 14, and this sensor 15 detects the oxygen concentration in the exhaust gas and supplies the detected value signal to the ECU 5.

Furthermore, a _PA sensor 16 that detects atmospheric pressure is connected to the ECU 5, and the ECU 5 is supplied with a detection signal from the atmospheric pressure sensor 16.

The ECU 5 determines engine operating conditions such as high-load operating conditions based on the various engine parameter signals described above, and the fuel injection valve 6 is determined according to the determined engine operating condition by the following calculation formula.
Calculate the fuel injection time T _OUT .

T _OUT = Ti × K _WOT × Ko ₂ × K ₁ + K ₂ Here, Ti indicates the basic fuel injection time, and this basic fuel injection time Ti is set according to the intake pipe absolute pressure P _BA and the engine speed Ne. . K _WOT is a enrichment coefficient during high load operation according to the present invention, and its details will be described later. KO ₂ detects _O2 sensor 15 when the engine is in the closed loop operating region
This is a correction coefficient that is set according to the oxygen concentration in exhaust gas detected by the system, and is set to a value of 1.0, for example, when the engine is in an open loop region such as a high load operation region. K ₁ and K ₂ are the various sensors mentioned above, namely, the throttle valve opening sensor 4, the intake pipe absolute pressure sensor 8, and the engine water temperature sensor 1.
0, other correction coefficients or correction values calculated according to the engine parameter signals from the Ne sensor 11 and the atmospheric pressure sensor 16, and depending on the engine operating state, starting characteristics, exhaust gas characteristics, fuel efficiency characteristics,
It is calculated based on a predetermined calculation formula so that various characteristics such as engine acceleration characteristics are optimized.

The ECU 5 supplies the fuel injection valve 6 with a drive signal to open the fuel injection valve 6 based on the fuel injection time T _OUT determined as described above.

FIG. 2 is a diagram showing the circuit configuration inside the ECU 5 shown in FIG. 1. The engine rotation speed signal from the Ne sensor 11 shown in FIG. (hereinafter referred to as "CPU") 503 and Me
It is also supplied to counter 502. Me counter 5
02 counts the time interval from when the previous predetermined position signal was input from the Ne sensor 11 to when the current predetermined position signal was input, and the counted value Me is proportional to the reciprocal of the engine rotation speed Ne. Me counter 50
2 transmits this count value Me via the data bus 510.
Supplied to CPU 503.

After the respective output signals from various sensors such as the throttle valve opening sensor 4, intake pipe absolute pressure P _BA sensor 8, and atmospheric pressure P _A sensor 16 shown in FIG. , A/D converter 50 sequentially by multiplexer 505
6. The A/D converter 506 sequentially converts the output signals from the aforementioned sensors into digital signals and supplies the digital signals to the CPU 503 via the data bus 510.

The CPU 503 further includes a read-only memory (hereinafter referred to as "ROM") 507 and a random access memory (RAM) via a data bus 510.
508 and the drive circuit 509,
The RAM 508 temporarily stores the calculation results of the CPU 503, and the ROM 507 stores the control program executed by the CPU 503, the basic injection time Ti map of the fuel injection valve 6, the reference value for determining the absolute pressure in the intake pipe, etc., which will be described later. There is. CPU503 is ROM507
According to the control program stored in the control program, first, the basic injection time Ti value is read out from the basic injection time Ti map according to each detected value of engine speed Ne and intake pipe absolute pressure P _BA , and then the various engine parameters mentioned above are read out. Correction coefficient values K ₁ , K ₂ , according to the signal
Set KO ₂ and the enrichment coefficient K _WOT during high load operation.

The CPU 503 calculates the fuel injection time of the fuel injection valve 6 by applying the set correction coefficient K _WOT etc. to the above calculation formula.
The drive circuit 509 calculates T _OUT and supplies a control signal based on this calculated value to the drive circuit 509 via the data bus 510, which drives the fuel injection valve 6 to open while the control signal is being input. A signal is supplied to the injection valve 6.

FIG. 3 is a flowchart for setting the enrichment coefficient K _WOT during high load operation, which is executed by the CPU 503 every time a pulse of the TDC signal is generated.

First, it is determined whether the engine rotational speed Ne is higher than a predetermined rotational speed Nz (for example, 4000 rpm), that is, whether the engine is in a high rotational operating range (step 1).

If the determination result of step 1 is negative (No),
That is, when the engine is in the low-speed operation region, the first intake pipe absolute pressure determination reference value P _BAWOT1i corresponding to the detected atmospheric pressure value P _A is read from the ROM 507 (step 2). Figure 4 is a table showing the relationship between the absolute pressure discrimination reference value P _BAWOT1i in the first intake pipe and the atmospheric pressure P _A , where the detected atmospheric pressure value P _A is the value P _A1 (for example, 650 mmHg).
In the following cases, the value P _BAWOT11 (e.g. 610mmHg) is used as the discrimination reference value, and the value P _A1 to P _A2 (e.g. 720mmHg) is used as the discrimination reference value.
Hg) when the value P _BAWOT12 (e.g. 660
mmHg) is greater than or equal to the value P _A2 , the value P _BAWOT13 (for example, 705 mmHg) is read out.

Next, it is determined whether or not the intake pipe absolute pressure detection value P _BA is larger than the first determination reference value P _BAWOT1i read out in step 2 (step 3). Figure 5 is a graph explaining the engine high load operating region. For example, when the atmospheric pressure P _A is the standard atmospheric pressure of 760 mmHg, the value P _BAWOT13 is used as the reference value for determining the absolute pressure in the first intake pipe as described above. When the intake pipe absolute pressure P _BA is equal to or higher than this determination reference value P _BAWOT13 , it is determined that the engine is in a high load operating region. Similarly, for example, atmospheric pressure P _A is 680 mmHg and
When the value is 640mmHg, each value is used as the discrimination reference value.
P _BAWOT12 and P _BAWOT11 are set, and the absolute pressure in the intake pipe is
The regions in which P _BA is greater than or equal to each discrimination reference value are the respective high-load operation regions.

If the determination result in step 3 is negative (No),
It is determined that the engine is not in the high load operating range, and the coefficient variable value X _WOTP is set to the value 1.0 (step 4).
On the other hand, if the determination result in step 3 is affirmative (Yes), it is determined that the engine is in a high load operating range, and the process proceeds to step 5, where a coefficient variable value X _WOTP is set in accordance with the detected atmospheric pressure value _PA . Figure 6 is the coefficient variable value
X A table diagram showing the relationship between _WOTPi and atmospheric pressure P _A. Same atmospheric pressure discrimination values P _A1 and P _A2 as in Figure 4.
For the coefficient variable value, there are three stages, i.e., the value
X _WOTP1 (e.g. value 1.1), value X _WOTP2 (e.g. value 1.15),
The value X _WOTP3 (for example, the value 1.2) is set. A value X _WOTPi corresponding to the detected atmospheric pressure value P _A is read from the table set in this manner, and the read value X _WOTPi is set as the coefficient variable value X _WOTP .

If the throttle valve 3 is opened beyond the predetermined opening value, the driver intends to accelerate the engine, and in this case, it is determined in step 3 that the engine is not in a high-load operating state. Even in such cases, it is desirable to enrich the air-fuel mixture to obtain high output. Therefore, the process proceeds to step 6, where a throttle valve opening determination value θ _WOTpi and a reference value θ _WOT1i , which will be described later, are read from the ROM 507 in accordance with the atmospheric pressure _PA . Figure 7 is a table showing the relationship between the throttle valve opening discrimination value θ _WOTpi and the atmospheric pressure P _A. When the detected atmospheric pressure value P _A is less than the value P _A1 (650 mmHg), the discrimination value is set to the value θ _WOTpi (for example, 70 mmHg).゜) is between the value P _A1 and the value P _A2 (720 mmHg), the value θ _WOTp2
(for example, 60°) is greater than or equal to the value P _A2 , the value θ _WOTp3
(for example, 50°) are read out respectively.

Figure 8 is a table diagram showing the relationship between the reference value θ _WOT1i and atmospheric pressure P _A , which is the same atmospheric pressure discrimination value as in Figure 7.
There are three standard values for P _A1 and P _A2 , namely θ _WOT11 (e.g. 75°), θ _WOT12 (e.g. 65°), θ _WO
T13 (eg 55°) is set.

Next, it is determined whether the valve opening value _θTH of the throttle valve 3 is larger than the determination value _θWOTpi read out in step 6 (step 7). In FIG. 5, each throttle valve opening discrimination value θ _WOTpi set when the atmospheric pressure is 760 mmHg, 680 mmHg, and 640 mmHg is illustrated by a thick solid line, and the valve opening θ _TH of the throttle valve 3 is shown as an example.
indicates that the region where is larger than these discriminant values θ _WOTpi is the throttle valve fully open operation region under each atmospheric pressure condition. The reason why the throttle valve opening determination value θ _WOTpi is set to a large value as the atmospheric pressure P _A decreases is as follows. In other words, when the engine is operated under low atmospheric pressure conditions such as at high altitudes, the weight flow rate of intake air taken in one intake stroke is lower than when operating on flat ground, so it is difficult to obtain the same output as when operating on flat ground. It is necessary to press the throttle valve even further. For this reason, when driving at high altitudes, the engine is in the throttle valve fully open operating range and the air-fuel mixture is enriched more frequently, resulting in deterioration of exhaust gas characteristics such as carbon monoxide (CO). Therefore, by setting the throttle valve opening discrimination value θ _WOTpi to a larger value as the atmospheric pressure P _A decreases and expanding the operating range in which closed-loop control is performed during high-altitude driving, exhaust gas characteristics and driving performance can be improved. The aim is to achieve optimization.

If the determination result in step 7 is negative (No),
It is determined that the engine is not in the throttle valve fully open operation range, and the coefficient variable value X _WOT 〓 is set to the value 1.0 (Step 8). On the other hand, if the determination result in step 7 is affirmative (Yes), it is determined that the engine is in the throttle valve fully open operation range, and the process proceeds to step 9, where the coefficient variable value X _WOT , which will be described later, corresponds to the detected atmospheric pressure value _P 〓 _i
Read from ROM507.

Figure 9 is a table diagram showing the relationship between the coefficient variable value X _WOT 〓 _i and the atmospheric pressure P _A. When the detected atmospheric pressure value P _A is less than the value P _A1 , the value X _WOT 〓 ₁ (for example, the value
1.1) is between the value P _A1 and the value P _A2 , the value
When X _WOT 〓 ₂ (for example, the value 1.15) is greater than or equal to the value P _A2 , the value X _WOT 〓 ₃ (for example, the value 1.2) is read out. The reason why the _coefficient variable _value This is due to the fact that there is no risk of excessive rise in bed temperature, and it is necessary to improve exhaust gas characteristics during high-altitude operation, especially to suppress carbon monoxide (CO) emissions. X _WOT 〓 By setting _{the i} value in this way, together with setting the discriminant value θ _WOTpi according to the atmospheric pressure P _A in step 6, the exhaust gas characteristics and driving performance during high-altitude driving can be further optimized. I can do it.

X _WOT read out in step 9 = _i value is the discriminant value θ _WOTpi and reference value θ _WOT1i read out in step 6
This is also applied to the coefficient variable value X _{WOT =} -throttle valve opening θ _TH table shown in FIG _. That is, the coefficient variable value X _WOT 〓 gradually increases from the value 1.0 to the value X _WOT 〓 _i read in step 9 as the throttle valve opening detection value θ _TH increases from the discrimination value θ _WOTpi to the reference value θ _WOT1i . , after reaching the reference value θ _WOT1i , it takes a value equal to the read value X _WOT 〓 _i . The reason why the air-fuel mixture is gradually enriched according to _the throttle valve opening value θ _TH is that the air-fuel ratio This is because it is necessary to smooth the transition between the throttle valve fully open operating range and other ranges so that an operating shock does not occur due to a sudden change in the throttle valve.

Next, it is determined whether the coefficient variable value X _WOTP set in step 4 or 5 is greater than the coefficient variable value X _WOT 〓 determined in step 8 or 10 (step 11), and the larger coefficient variable value is determined. The enrichment coefficient
Let be the value of K _WOT . That is, if the determination result in step ₁₁ is affirmative (Yes), the _coefficient variable _value The conversion coefficient value is set to K _WOT (Step 13).

If the answer to the determination in step 1 is affirmative (Yes), that is, if it is determined that the engine is being operated at a high rotational speed higher than the predetermined rotational speed Nz, the _engine The second intake pipe absolute pressure determination reference value P _BAWOT2i is read from the ROM 507 (step 14). Figure 11 is a table diagram showing the relationship between the absolute pressure discrimination reference value P _BAWOT2i in the second intake pipe and the atmospheric pressure P _A , and as in the case of Figure 4, for the same atmospheric pressure discrimination values P _A1 and P _A2 . There are three levels of discrimination standard value, namely, discrimination standard value P _BAWOT21 (e.g.
450mmHg), P _BAWOT22 (e.g. 520mmHg), P _BAWOT23
(for example, 600mmHg). A value P _BAWOT2i corresponding to the detected atmospheric pressure value P _A is read out from the table set in this manner. Furthermore, this read value
P _BAWOT2i is set to a value smaller than the first discrimination reference value P _BAWOT1i corresponding to the same atmospheric pressure (the fifth
figure).

Next, the intake pipe absolute pressure detection value P _BA is
It is determined whether or not the second determination reference value P _BAWOT2i read out in step 14 is greater than the second determination reference value P BAWOT2i (step 15). step
If the determination result in step 15 is negative (No), it is determined that the engine is not in the high load operation range, and the enrichment coefficient is
Set the value of K _WOT directly to the value 1.0 (step 16).
On the other hand, if the determination result in step 15 is affirmative (Yes), it is determined that the engine is in the high-load operating range, and the process proceeds to step 17, in which, as in step 5, the coefficient variable value is determined according to the detected atmospheric pressure value P _A. X _WOTPi is read from the table shown in FIG. 6, and the read value X _WOTPi is set as the enrichment coefficient value K _W (step 18).

In addition, in the engine high speed operation region, the second intake pipe absolute pressure discrimination reference value P _BAWOT2i is set to a smaller value than the first discrimination reference value P _BAWOT1i corresponding to the same atmospheric pressure, so the throttle valve is operated at full throttle. The area is approximately included in the high load operation area. Therefore, in the high-speed operating range, there is no need to provide a step (steps 6 to 10) for determining whether or not the engine is in the fully open throttle valve operating range and enriching the air-fuel mixture when the engine is in that range.

Further, the first and second intake pipe absolute pressure discrimination values
P _BAWOT1i , P _BAWOT2i , atmospheric pressure reference values shown in Figure 4, etc.
P _A1 and P _A2 are set to different values when entering and exiting the engine's high-load operating range or throttle valve fully open operating range, and are provided with hysteresis characteristics to stabilize fuel supply control. Good too.

Effects of the Invention As detailed above, according to the fuel supply control method of the present invention during high-load operation of an internal combustion engine, atmospheric pressure is detected, engine rotation speed is detected, and the detected atmospheric pressure is In addition, the intake passage pressure discrimination value is determined to be set to a value on the lower load side as the detected engine rotational value increases, and the intake passage pressure discrimination value is detecting the downstream pressure of the throttle valve in the
The detected intake passage pressure value is compared with the intake passage pressure discrimination value, and when the intake passage pressure detection value is on the higher load side than the intake passage pressure discrimination value, the intake passage pressure is supplied to the engine. Since the amount of fuel is increased, even when the engine is operated under low atmospheric pressure conditions such as at high altitudes, it is possible to obtain the same driving performance as when driving on flat ground, and the exhaust purification system can be used throughout the entire engine speed range. It is possible to prevent the temperature from rising excessively.

[Brief explanation of the drawing]

Fig. 1 is an overall configuration diagram of a fuel supply control device to which the present invention is applied, Fig. 2 is a circuit diagram showing the internal configuration of the electronic control unit (ECU) of Fig. 1, and Fig. 3 is a high load according to the present invention. Flowchart showing the procedure for setting the enrichment coefficient value K _WOT during operation,
Fig. 4 is a table diagram showing the relationship between atmospheric pressure P _A and the first intake pipe absolute pressure discrimination reference value P _BAWOT1i applied during low speed operation, Fig. 5 is a graph showing the high load operation region, and Fig. 6 is a graph showing the high load operation region. The figure shows atmospheric pressure P _A and coefficient variable values.
_Figure 7 is a table diagram showing the relationship between atmospheric pressure P _A and throttle valve opening determination value θ _WOTpi , and Figure 8 is a table diagram showing the relationship between atmospheric pressure P _A and reference value θ _WOT1i . Figure 9 is a table diagram showing the relationship between atmospheric pressure P _A and coefficient variable value X _WOT 〓 _i . Figure 10 is a table diagram showing the relationship between throttle valve opening θ _TH and coefficient variable value X _WOT 〓 FIG. 11 is a table diagram showing the relationship between the atmospheric pressure P _A and the second intake pipe absolute pressure discrimination reference value P _BAWOT2i applied during high-speed operation. 1...Internal combustion engine, 2...Intake passage, 3...
Throttle valve, 4...Throttle valve opening sensor,
5...Electronic control unit, 6...Fuel injection valve, 14...Three-way catalyst, 16...Atmospheric pressure sensor.

Claims (1)

[Claims] 1. In a fuel supply control method for an internal combustion engine that includes an intake passage and a throttle valve disposed in the middle of the passage, atmospheric pressure is detected, engine rotational speed is detected, and the intake passage is controlled according to the detected atmospheric pressure value. The throttle valve downstream pressure discrimination value is determined, and the intake passage pressure discrimination value is further determined to be set to a value on the lower load side as the detected engine rotational value increases. , detecting the pressure downstream of the throttle valve in the intake passage, comparing the detected intake passage pressure value with the intake passage pressure discrimination value, and determining whether the detected intake passage pressure value is the intake passage pressure; 1. A fuel supply control method during high-load operation of an internal combustion engine, characterized by increasing the amount of fuel supplied to the engine when the value is on the high-load side of the discrimination value.