JPH0531644B2 - - 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.

However, according to the conventional technique for increasing the delay amount as described above, the following disadvantages occur.

(1) As the load increases and the combustion chamber temperature increases, knocking becomes more likely, so it is undesirable from the viewpoint of engine durability not to increase the amount at all during the delay.

(2) When the air-fuel ratio is quite lean, the exhaust temperature rises quickly and the delay in increasing the amount of fuel can only be delayed for a very short time, so there is little effect on improving fuel efficiency.

(3) Since the air-fuel ratio remains lean during the delay,
Sufficient output cannot be obtained and acceleration feeling is poor.

In order to eliminate the above-mentioned disadvantages, the present applicant has proposed that when a high load condition occurs, the amount of fuel is increased immediately without delay until the output increase value becomes the output air-fuel ratio, but when the output increase value is exceeded, the fuel amount is increased immediately under high load. Prior to the present application, a technique was proposed in which the amount of fuel is gradually increased until the fuel amount is increased to a certain amount.

Problems to be Solved by the Invention However, according to the above-mentioned prior art, the fuel increase is delayed regardless of the engine temperature, so when the engine temperature is high, the fuel amount is too small and knocking occurs immediately after the fuel increase starts. However, there were problems with the durability of the engine. Furthermore, since the control to suppress the occurrence of knocking by installing a knocking sensor retards the ignition angle, an increase in exhaust gas temperature cannot be avoided. Furthermore, if sufficient fuel is supplied immediately after the start of fuel increase to prevent knocking even at high engine temperatures, the initial objective of improving the fuel consumption rate, etc., will not be achieved at all.

Means for Solving the Problems The structure of the present invention that solves the above problems will be explained with reference to FIG. a state detecting means b; a target fuel amount increasing means c for increasing the target fuel amount in accordance with the load increase when the high load state detecting means b determines that the load is high; and a fuel amount supplied to the engine a. is the target fuel amount increasing means c
an increase delay means d for delaying the operation of increasing the amount of fuel up to the target fuel amount increased by a predetermined time; an engine temperature detection means e for detecting the engine temperature; means d
The present invention is characterized by comprising a delay amount changing means f for changing the delay amount of.

Effect The fuel increase value (setting value) at the start of high load fuel increase is changed according to the engine temperature, so if the set value is increased when the engine temperature is high, the amount of fuel increased immediately after the high load fuel increase starts will increase. Become. Therefore, a sufficient amount of fuel to prevent knocking will be supplied immediately after the start of a high load increase. This also shortens the delay time for high load increases.
In addition, when the engine is at low temperature (at room temperature), the above-mentioned set value is made equal to the output increase value, and the increase immediately after the start of high load increase is controlled to be close to the output increase value, and the delay time is lengthened. By maintaining the fuel ratio near the output air-fuel ratio for as long as possible, it is possible to improve fuel efficiency and increase output.

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 accelerator 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, at a 360° crank angle, and the rotation angle sensor 30 outputs a pulse signal.
A pulse signal can be output every 30° crank 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 Kotp 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 amount Q is stored at a predetermined location in the RAM 42, together with input data representing the cooling water temperature THW and the intake air temperature THA, each time the conversion by the A/D converter 58 is completed. 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, that is, a pulse signal every 30 degrees of crank angle, is applied.

In the next step 101, a set value Kpw of the high load increase value Kotp is calculated. This set value Kpw changes depending on the cooling water temperature THW, and a method for calculating it will be explained in detail later with reference to FIG. 11 or 12.

In the next step 102, the set value Kpw obtained in step 101 is compared with the high load increase value Kotp, and
If is less than Kpw (Kotp≦Kpw), step
Proceeding to step 103, the injection pulse width τ is calculated using Kotp without regulating Kotp using the upper limit G. That is, in this case, the high load increase will be performed immediately without any delay. The calculation method of τ in step 103 is Q/N,
Kotp, correction coefficient β due to cooling water temperature THW, etc.
The injection pulse width τ is calculated from the following equation using other correction coefficients α.

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

If it is determined in step 102 that Kotp>Kpw, the processes in steps 104 to 108 are performed, and the upper limit G of the high load increase value Kotp is set to the rotation speed N.
Ask accordingly. Steps 104 to 108 are for calculating the upper limit value G of the relationship as shown in FIG.

In the next step 109, the count value is incremented every 4 msec in the processing routine of Fig. 5.
A new upper limit value G is determined from Ctd and the upper limit value G determined in steps 403 to 407 using the following equation.

G=G×Ctd×24/1000 Through this process, G increases by 6% per second (provided that N is constant).

In addition, in the 4 msec interrupt processing routine in Fig. 5, 200 increments Ctd by 1, and steps 201 and 202 increment Ctd.
This is a step to regulate Ctd to be less than "2000".

In step 110 of Fig. 4, the G calculated as described above is also the high load increase value calculated in the previous routine.
Add it to K'otp to get the final upper limit G. Next, in steps 111 and 112, processing is performed to regulate the high load increase value Kotp to be below the upper limit value G determined as described above. Using Kotp regulated in this way, τ is calculated in step 103.

As mentioned above, when Kotp exceeds Kpw, Kotp is regulated to be below the upper limit value G that increases gradually, and therefore Kotp gradually increases and the high load increase is delayed. becomes. In addition, the upper limit value G is controlled according to the rotational speed N so that when N is large, G becomes large, so the increase rate at high loads changes as described above according to N, and the actual exhaust gas temperature It is possible to perform an optimal high load increase commensurate with the increase. Also, if the high load increase value Kotp is less than the set value Kpw, the Kotp
Since the amount is increased by the value of , the period during which the output air-fuel ratio is kept leaner than the output air-fuel ratio at room temperature is shorter, and an increase in output can be expected immediately after the load increases. Furthermore, as will be explained later, the set value Kpw changes according to the cooling water temperature THW, increasing when THW is high. This will be done immediately. As a result, the occurrence of knocking can be reliably suppressed.

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 TRD 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 Kotp to Kotp.
By setting = 0.0, the amount is not increased.

If Q/N≧TRD, first proceed to step 307 to obtain Kotp ₃ . This Kotp ₃ is obtained from Kotp ₂ according to Q/N as shown in Fig. 9 and the TRD mentioned above, and Kotp ₃ = Kotp ₂ - TRD/3 = Q/N/3 - TRD/3. Calculated from the formula. Next, in steps 308 to 311, Kotp ₁ of the relationship shown in FIG. 8 according to N is determined.
is required. Next, in step 313, the high load increase value Kotp is determined from Kotp=Kotp ₁ ×Kotp ₃ . In this way, in steps 307 to 313, N
A high load increase value Kotp corresponding to the operating state at that time is determined from and Q/N. In addition to the processing routine shown in Figure 6, the method for calculating Kotp is as follows:
You can obtain it directly from a two-dimensional table with N, or
Various other methods are also possible.

Figure 11 shows the steps of the processing routine in Figure 4.
101 shows an example of a method for calculating Kpw.

First, in step 400, the cooling water temperature is
Determine whether THW is below 105℃.
If THW≦105°C, it is determined that the temperature is normal, and the process proceeds to step 401, where an increase value corresponding to the output air-fuel ratio, 13% in this embodiment, is substituted for the set value Kpw. As a result, the fuel increase immediately after the start of the high load increase is controlled to be near the output increase value, thereby increasing the delay time, and as a result, the air-fuel ratio can be maintained near the output air-fuel ratio for as long as possible. This makes it possible to improve fuel efficiency and increase output at room temperature. On the other hand, if THW > 105℃, it is determined that the temperature is high and the process proceeds to step 402.
For example, if Kpw has a value much larger than the output increase value,
Substitute Kpw=30%. As a result, the amount of fuel increases immediately after the start of the high load increase, and the air-fuel ratio becomes significantly richer immediately after the start of the increase, so that knocking can be prevented from occurring.

Figure 12 shows the steps of the processing routine in Figure 4.
101 represents another example of the calculation method of Kpw.

In this example, if THW is 100°C or less, Kpw = 13% in step 501, and if THW is 120°C or more, Kpw = 30% in step 503, and 100°C <
If THW<120℃, step 504 will set 13% and 30%.
Kpw is set equal to the linearly interpolated value.
By controlling Kpw as shown in FIG. 12, high load increase control can be performed with higher accuracy.

In addition, in the example described above, Kpw is the cooling water temperature.
Although it is changed according to THW, it may be changed according to other parameters representing engine temperature such as oil temperature and cylinder block temperature.

Effects of the Invention Since the set value at the start of high load increase is changed according to the engine temperature, it is possible to prevent knocking when the engine is at high temperature, and also to improve fuel efficiency and increase output when the engine is at low temperature. 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 as 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 a second control circuit, and FIGS. 4 to 6 are control diagrams of FIG. 3. A flowchart showing a part of the program of the microcomputer of the circuit, Fig. 7 is a characteristic diagram showing the high load increase range, Fig. 8 is a characteristic diagram of N-Kotp ₁ , and Fig. 9 is a characteristic diagram of Q/N-Kotp _2. 10 is an NG characteristic diagram, and FIGS. 11 and 12 are flowcharts showing part of the program of the microcomputer of the control circuit of FIG. 3. 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 determining whether or not the engine is in a high load state; and when the high load state detection means determines that the engine is under high load, a target is set according to the increase in load. a target fuel amount increasing means for increasing the amount of fuel; an increase delay means for delaying the operation of increasing the amount of fuel supplied to the engine to the target fuel amount increased by the target fuel amount increasing means for a predetermined time; and increasing the engine temperature. A fuel for an internal combustion engine, comprising: an engine temperature detection means for detecting the engine temperature; and a delay amount changing means for changing the delay amount of the increase delay means in accordance with the engine temperature detected by the engine temperature detection means. Injection amount control device.