JPH0534494B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a fuel injection amount control device that increases the amount of fuel when an internal combustion engine is under high load.

Prior Art Most current internal combustion engines control the air-fuel ratio to be rich (richer than the output air-fuel ratio) by increasing the amount of fuel during high-load operation, thereby suppressing the temperature rise in the exhaust gas flow. There is. Particularly in turbocharged engines, it is necessary to significantly lower the exhaust temperature due to durability issues, so there is a tendency to increase the amount of fuel and make the air-fuel ratio richer.

Naturally, when such a high load increase is performed, the fuel consumption rate worsens, but in order to improve this, the operating conditions for the high load increase are divided into areas, and from the time when the load reaches a high load, the fuel consumption rate is deteriorated. A technique is known in which the amount is increased after a predetermined delay time has elapsed (Japanese Unexamined Patent Publication No. 58-51241). This technology focuses on the fact that even when the load increases, there is some time leeway until the exhaust gas temperature rises.

Problems to be Solved by the Invention However, according to the conventional technique for increasing the delay amount as described above, the following disadvantages occur.

Since the amount of fuel is suddenly increased after the delay time has elapsed, the occurrence of torque shock is unavoidable. Even if the amount of fuel is averaged over time, it is possible to alleviate torque shock, but if the increase in fuel amount is large, the occurrence of torque shock cannot be prevented.

If the load is increased more slowly, the amount of fuel will also be increased more slowly, but if the increase is delayed or averaged over time in this case, the acceleration feeling will be impaired.

The present invention was developed in view of the above problems, and it reliably suppresses the occurrence of torque shock when the load suddenly shifts to a high load state, and also suppresses acceleration feeling when the load shifts gradually to a high load state. It is an object of the present invention to provide a fuel injection amount control device for an internal combustion engine that can improve fuel efficiency without causing any damage.

Means for Solving the Problems The basic configuration of the present invention will be explained with reference to FIG. , a fuel increase value calculation means c which calculates a fuel increase value according to the operating state of the engine when the high load detection means b determines that the engine is in a high load state, and a fuel increase value calculation means c which calculates the basic fuel injection amount. A fuel increasing means d gradually increases the amount of fuel to be injected to an increased amount of fuel up to the fuel increasing value calculated in d, and a predetermined maximum time increase rate over time of the increased amount of fuel injected increased by the fuel increasing means d. an increase rate limiting means e that limits the temporal increase rate of the increased fuel injection amount increased by the fuel increase means d to a maximum increase rate when the increase rate is greater than the increase rate;
It is characterized by having the following.

Effect: Since the fuel injection amount is gradually increased from the moment the load reaches a high load state to the predetermined increase value,
Since the air-fuel ratio is controlled in the rich direction in accordance with the rise in engine combustion chamber temperature, the occurrence of knocking can be suppressed, and the air-fuel ratio can be kept on the lean side for a long time until the amount is increased to a predetermined increase value. Further, as the load increases, the air-fuel ratio starts to become richer, so the period during which the air-fuel ratio is close to the output air-fuel ratio becomes longer, and a high output can be obtained during that period. Furthermore, since the air-fuel ratio becomes richer as the exhaust gas temperature rises, the air-fuel ratio can be controlled to the lean side for a longer period of time even when the exhaust gas temperature rises.

Example The present invention will be explained in detail below with reference to Examples.

FIG. 2 schematically shows an electronically controlled fuel injection type internal combustion engine in which the engine load is determined from the intake air flow rate Q and the rotational speed N as an embodiment of the present invention. In the same figure, 10 is an intake passage 1
An air flow sensor 14 of the above-mentioned type is provided at 2 and generates a voltage according to the intake air flow rate Q, and 14 is also provided at the intake passage 12 and measures the intake air temperature THA.
This is an intake air temperature sensor that generates a voltage depending on the temperature. A throttle valve 16 that operates in conjunction with an access pedal (not shown) is provided in the intake passage 12 downstream of the air flow sensor 10 and the intake temperature sensor 14, and a fuel injection valve 18 is provided in the intake manifold downstream of the throttle valve 16.

The cylinder block 20 of the engine has a cooling water temperature
A water temperature sensor 22 is provided that generates a voltage according to THW.

Detected voltages from the air flow sensor 10, intake temperature sensor 14, and water temperature sensor 22 are sent to a control circuit 24.

The cylinder discrimination sensor 2 is installed in the distributor 26.
8 and a rotation angle sensor 30 are provided. The cylinder discrimination sensor 28 outputs a pulse signal at every predetermined angular position before the top dead center of the reference cylinder, for example every 360° crank angle, and the rotation angle sensor 30 outputs a pulse signal.
A pulse signal is output at every 30° angle. These pulse signals are sent to the control circuit 24.

On the other hand, the control circuit 24 applies a drive pulse to the fuel injection valve 18, which causes the fuel injection valve 18 to inject pressurized fuel sent from a fuel supply system (not shown) into the intake passage near the combustion chamber 34. Sprays intermittently.

FIG. 3 shows the circuit configuration of the control circuit 24 shown in FIG. As is clear from the figure, the control circuit 24 is equipped with a microcomputer, and this microcomputer is a central processing unit (CPU).
40, random access memory (RAM) 42,
read-only memory (ROM) 44, first and second input/output ports 46 and 48, output port 50,
It mainly consists of a clock generation circuit 52 and a bus 54 that interconnects these circuits and transfers data.

The detected voltages from the air flow sensor 10, intake air temperature sensor 14, and water temperature sensor 22 are sequentially selected by a multiplexer 56, converted to a binary signal by an analog/digital (A/D) converter 58, and then output to the first input. It is applied to the microcomputer via output port 46.

The pulse signals from the cylinder discrimination sensor 28 and the rotation angle sensor 30 are waveform-shaped in the shaping circuit 60 and then applied to the microcomputer via the second input/output port 48.

When an injection pulse signal is output from the microcomputer to the drive circuit 62 via the output port 50, this is converted into a drive pulse and the fuel injection valve 18 is converted into a drive pulse.
is energized and fuel injection is performed.

Next, an example of the operation of the microcomputer will be explained using the flowcharts shown in FIGS. 4 to 6.

FIG. 4 shows a routine for calculating the fuel injection pulse width τ, which is executed during the main routine.

First, in step 100, a high load increase value K _OTP is calculated from N and Q/N. This calculation method is shown in FIG. 6 and will be described later. Input data representing the intake air flow rate Q is input to the A/D together with input data representing the cooling water temperature THW and the intake air temperature THA.
Each time the conversion by the converter 58 is completed, it is stored in a predetermined location in the RAM 42. At this time, the intake air amount Q/N per unit rotation corresponding to the engine load is calculated from the rotational speed N and the intake air flow rate Q.
It is stored in RAM42. Note that the rotation speed N is
It is determined by a well-known method of measuring the time interval at which a pulse signal from the rotation angle sensor 30, ie, a pulse signal every 30 degrees of crank angle, is applied.

In the next steps 101 and 102, the high load increase value
The upper limit G of K _OTP is calculated. First step 101
Then, in the processing routine of FIG. 5, G is made equal to the value C _td ×80/1000, which is obtained by multiplying the count value C _td incremented every 4 msec by 80/1000. Through this process, G increases by 20% per second. Next, in step 102, this G is added to the high load increase value K' _OTP calculated in the previous routine to obtain the final upper limit G.

In the 4 msec interrupt processing routine in Figure 5, 200 is the step to increment C _td by "1", and 201 and 202 are the steps to increment C td by "1".
This is a step to regulate C _td to be less than "2000".

In steps 103 and 104 in FIG. 4, processing is performed to regulate the high load increase value K _OTP to be below the upper limit value G determined as described above.

Next, in step 105, Q/N, K _OTP regulated below the upper limit G as described above, and cooling water temperature THW are determined.
The injection pulse width τ is calculated from the following equation using the correction coefficient β based on the above equation and other correction coefficients α.

τ=Q/N×α×(1+β+K _OTP ) The calculated injection pulse width τ is temporarily stored in the RAM 42, and after being converted into an injection pulse signal by an injection control routine executed at each predetermined crank angle position, Drive circuit 62 via output port 50
is output to.

Figure 6 shows step 100 of the processing routine in Figure 4.
The processing details are shown in detail. Step 300~
In 304, a function TRD regarding N and Q/N as shown in FIG. 7 is determined. This function TPD represents the boundary of whether or not to perform a high load increase.
If Q/N is more than TRD, increase the load with high load,
Not performed if Q/N is smaller. The next step 305 is to make this determination, and Q/N<
For TRD, proceed to step 306 and set K _OTP to K _OTP =
Setting it to 0.0 will not increase the amount.

If Q/N≧TRD, first proceed to step 307 to find K _OTP3 . This K _OTP3 is obtained from K _OTP2 according to Q/N as shown in Fig. 9 and the above-mentioned TRD, and K _OTP3 = K _OTP2 - TRD/3 = Q/N/3 - TRD/3. Calculated from the formula. Next, in steps 308 to 311, K _OTP1 having the relationship shown in FIG. 8 according to N is determined. Then step
313, the high load increase value K _OTP is K _OTP = K _OTP1 ×
Determined from K _OTP3 . In this way, step 307
~313, a high load increase value K _OTP corresponding to the operating state at that time is determined from N and Q/N. this
In addition to the processing routine shown in FIG. 6, K _OTP may be determined directly from a two-dimensional table of N and Q/N, and various other methods may be considered.

FIG. 10 shows a comparison between the operation of the first embodiment described above and the prior art, with the broken line representing the prior art and the solid line representing this embodiment.

As shown in _A1 in the same figure, when Q/N increases,
In the prior art, after the delay of _A2 , _KOTP was increased stepwise as shown in _A3 . On the other hand, in this example, as Q/N increases, A ₄
As shown in Figure 6, K _OTP is determined by the processing routine in Figure 6, and this is further regulated by the upper limit G as shown in _A5 , so the high load increase value K _OTP that is finally obtained is
As shown in _A5 , is gradually increased without delay as Q/N increases. As K _OTP is gradually increased in accordance with the rise in combustion chamber temperature, the air-fuel ratio is also gradually controlled toward richness as shown in D ₁ in Figure D, and as a result, as shown in C ₁ in Figure C. As shown, the occurrence of knocking is significantly suppressed compared to the case of conventional technology _C2 . In addition, since the period of the output air-fuel ratio becomes longer, as shown in _B1 of B in the same figure,
The shaft torque is significantly larger than the conventional _B2 .
Furthermore, as the air-fuel ratio gradually becomes richer as the exhaust temperature rises, as shown in B ₃ , the exhaust temperature is controlled to be lower than that of the conventional technology B ₄ , while maintaining the air-fuel ratio on the lean side for a longer period of time. It is possible to achieve both a reduction in fuel consumption and an improvement in fuel efficiency.

FIG. 11 shows a routine for calculating the fuel injection pulse width τ in the second embodiment of the present invention.

In this processing routine, the upper limit value G is changed according to the rotational speed N of the engine.

First, in step 400, a high load increase value K _OTP is determined in the same manner as step 100 in FIG. 4, that is, in accordance with the processing routine in FIG. In the next step 401,
The high load increase value K _OTP obtained in step 400 is the output increase value that can obtain the maximum output of the engine (in this case, 13
%) or less. If K _OTP is less than the output increase value (K _OTP ≦13%), the process directly proceeds to step 402, and the injection pulse width is calculated without regulating K _OTP by the upper limit value. This step 402 has exactly the same processing content as step 105 in FIG.

If K _OTP exceeds the output increase value, step
The processes 403 to 407 are performed to obtain the upper limit value G according to the rotational speed N. Steps 403 to 407 are for calculating G according to N in the relationship shown in FIG.

In the next step 408, the processing routine shown in FIG.
Count value C _td incremented every 4 msec
A new upper limit value G is determined from the upper limit value G determined in steps 403 to 407 using the following equation.

G=G×C _td ×24/1000 Through this process, G increases by 6% per second (provided that N is constant). The processing contents of subsequent steps 409 to 411 are the steps in Fig. 4.
The content is exactly the same as 102-104.

In this way, in this embodiment, the upper limit G is set to the rotational speed N
Since G is controlled to increase when N is large according to Can be increased. In addition, when the high load increase value K _OTP is less than the output increase value, the output increases immediately at the value of that K _OTP .
The period during which the air-fuel ratio is kept leaner than the output air-fuel ratio is shorter, and an increase in output can be expected immediately after the load increases.

FIGS. 13 and 14 show a processing routine of a third embodiment of the present invention.

FIG. 13 shows a part of a processing routine that is executed every predetermined crank angle, for example every 120° crank angle, and in step 500, the upper limit G of the high load increase value K _OTP is increased by 0.5%. In contrast to the previously described embodiment in which G was increased according to time, in this embodiment G is increased at every predetermined crank angle.

FIG. 14 shows a routine for calculating the injection pulse width τ.

At step 600, step 100 in FIG.
K _OTP is calculated in the same way as step 400 in FIG.
In the next steps 601 and 602, the steps shown in FIG.
Exactly the same processing as 103 and 104 is performed to regulate K _OTP to below G. In step 603, the thus regulated K _OTP is entered into the upper limit value G in preparation for calculation of the next upper limit value G. In the next step 604, the steps shown in FIG.
Similarly to 105, the injection pulse width τ is determined.

As in this embodiment, the high load increase value K _OTP may be increased in synchronization with the rotation of the engine crankshaft.

Effects of the Invention As explained above, according to the present invention, when the load suddenly becomes high, the temporal increase rate of the increased fuel injection amount is regulated to a predetermined maximum increase rate, thereby preventing the occurrence of torque shock. When the load gradually shifts to high, the amount of fuel is increased at the same rate of change over time, so the acceleration feeling is not impaired. Furthermore, in both cases, since the fuel amount starts to increase when the load starts to increase, the air-fuel ratio is controlled in the rich direction as the engine combustion chamber temperature rises, suppressing the occurrence of knocking, which improves durability. This is preferable, and since the air-fuel ratio can be maintained on the lean side for a long time until the amount is increased to a predetermined increase value, fuel efficiency is significantly improved. Further, as the load increases, the air-fuel ratio starts to become richer, so the period during which the air-fuel ratio is close to the output air-fuel ratio becomes longer, and during this period a high output is obtained, improving acceleration feeling. Furthermore, since the air-fuel ratio becomes richer as the exhaust temperature rises, the air-fuel ratio can be controlled leaner for a longer period of time even when the exhaust temperature rises, leading to improved fuel efficiency in this sense as well.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the present invention, FIG. 2 is a schematic diagram of an embodiment of the present invention, FIG. 3 is a block diagram of the control circuit of FIG. 2, and FIGS. A flowchart showing a part of the program of the microcomputer of the control circuit, Fig. 7 is a characteristic diagram showing the high load increase range, Fig. 8 is a characteristic diagram of N-K _OTP1 , and Fig. 9 is a characteristic diagram of Q/N-K _OTP2 . FIG. 10 is an explanatory diagram of the effects of the above-mentioned embodiment. FIG. 11 is a flowchart showing a partial program of the microcomputer of the control circuit of FIG. 3. FIG. 12 is a characteristic diagram of NG. , FIGS. 13 and 14 are flowcharts showing part of the program of the microcomputer of the control circuit of FIG. 10...Air flow sensor, 14...Intake temperature sensor, 18...Fuel injection valve, 22...Water temperature sensor, 24
...Control circuit, 28...Cylinder discrimination sensor, 30...Rotation angle sensor.

Claims (1)

[Scope of Claims] 1. High load state detection means for detecting whether or not the engine is in a high load state requiring an increase in fuel amount; and when the high load detection means determines that the engine is in a high load state, a fuel increase value calculation means for calculating a fuel increase value according to the operating state of the engine; and a basic fuel injection amount that is gradually increased to the fuel increase value calculated by the fuel increase value calculation means to obtain an increased fuel injection amount. a fuel increasing means, and when the temporal increase rate of the increased fuel injection amount increased by the fuel increasing means is greater than a predetermined maximum increase rate, the increased fuel amount increased by the fuel increasing means; A fuel injection amount control device for an internal combustion engine, comprising: an increase rate limiting means for limiting a temporal increase rate of the injection amount to the maximum increase rate.