JPH0362893B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for controlling the amount of fuel supplied to an internal combustion engine depending on operating state parameters of the engine. It detects the engine rotational speed and intake pipe pressure, determines the basic injection pulse width of the fuel injection valve or fuel supply amount control valve in the carburetor according to these detected values, and also detects the engine temperature, for example, the cooling water temperature. A fuel supply amount control method is well known in which the basic injection pulse width is corrected according to this detected value, and the amount of fuel actually supplied is adjusted according to the corrected injection pulse width. The purpose of increasing the injection pulse width (warm-up increase correction) in accordance with the engine temperature is to improve the operating characteristics by increasing the amount of fuel in accordance with the extent to which the engine is cold. However, immediately after the engine is started, it is insufficient to perform such warm-up increase correction, and it is necessary to perform a special increase correction immediately after the engine is started. That is,
Immediately after starting, the lubricating oil is cold, so the lubrication effect is insufficient, and the wall temperature of the combustion chamber is low, so sufficient combustion is difficult. It requires correction. If the above-mentioned post-start increase correction is always performed after starting the engine, the following problems will occur. In other words, there is no problem if the engine is started when it is cold, but if the engine is restarted after it has warmed up to some extent and the increase correction is performed after starting, the air-fuel ratio becomes unnecessarily rich and the exhaust gas Gas purification characteristics are significantly deteriorated, and fuel efficiency is correspondingly deteriorated. Therefore, the present invention solves the above problems of the prior art, and an object of the present invention is to prevent the air-fuel ratio from becoming excessively rich when the engine is restarted after warming up. . The features of the invention that achieve this object include detecting the operating state of the internal combustion engine and determining the amount of fuel to be supplied to the engine according to the detected operating state, while detecting the temperature of the engine and determining the amount of fuel to be supplied to the engine according to the detected operating state. In the fuel supply amount control method, the determined fuel amount is increased during a period after the engine start has ended until the engine temperature rises by a predetermined temperature from the temperature at the end of the start. The above-mentioned increase processing is not performed when the engine temperature exceeds a predetermined value. The present invention will be explained in detail below with reference to the drawings. FIG. 1 schematically shows an example of an electronically controlled fuel injection type internal combustion engine as an embodiment of the present invention. In the figure, 10 represents the engine body, 12 represents an intake passage, 14 represents a combustion chamber, and 16 represents an exhaust passage. The flow rate of intake air taken in through an air cleaner (not shown) is controlled by a throttle valve 18 that is linked to an accelerator pedal (not shown). Intake air that has passed through the throttle valve 18 is guided into the combustion chamber 14 via a surge tank 20 and an intake valve 22. In the intake passage downstream of the throttle valve 18, for example in the surge tank 20, there is a pressure takeout port 2 that communicates with a pressure sensor 24 that detects the absolute pressure inside the intake pipe and generates a voltage corresponding to the detected value.
4a is open. The output voltage of this pressure sensor 24 is sent to a control circuit 28 via line 26. The fuel injection valve 30 is actually provided for each cylinder, and is controlled to open and close in response to electrical drive pulses sent from the control circuit 28 via a line 32, and sent from a fuel supply system (not shown). Pressurized fuel is intermittently injected into the intake passage 12 near the intake valve 22. The exhaust gas after being burned in the combustion chamber 14 is discharged into the atmosphere via the exhaust valve 34 and the exhaust passage 16, and further via the catalytic converter 36. Crank angle sensors 40 and 42 provided in the distributor 38 output pulse signals each time a crankshaft (not shown) rotates by 30° and 360°, and the pulse signal for each 30° crank angle is shown by a line 44. The pulse signal for every 360° crank angle is line 4.
6 to the control circuit 28, respectively. The engine cylinder block is equipped with a water temperature sensor 48 for detecting the coolant temperature, the output voltage of which is representative of the detected coolant temperature is fed to the control circuit 28 via line 50. Control circuit 28 may also be fed a starting signal from starter switch 52 via line 54 . This trigger signal is used in one embodiment of the invention, but other alternative signals may be used as described below. FIG. 2 is a block diagram showing an example of the configuration of the control circuit 28 shown in FIG. In the figure, the pressure sensor 24, crank angle sensors 40 and 42, starter switch 52, and fuel injection valve 30 provided for each cylinder are each represented by blocks. As shown in the figure, the water temperature sensor 48 is composed of a thermistor, and a series connection circuit of the thermistor and a fixed resistor is inserted between the constant voltage source and the ground. The output voltage of the water temperature sensor 48 is taken out from the non-grounded terminal of the thermistor. The output voltages of the pressure sensor 24 and water temperature sensor 48 are output from an A/D with an analog multiplexer function.
The signal is sent to a converter 60, selected and A/D converted in accordance with an instruction signal from a microprocessor (MPU) 62, and becomes a binary signal. A pulse signal every 30 degrees of crank angle from the crank angle sensor 40 is transmitted to an input/output circuit (I/O circuit) 64.
is sent to the MPU62 via the crank angle 30°
It serves as an interrupt request signal for the interrupt processing routine and also serves as an increment clock for a timing counter provided in the I/O circuit 64. A pulse signal for each 360° crank angle from the crank angle sensor 42 serves as a reset signal for the timing counter.
The injection start timing signal obtained from this timing counter is sent to the MPU 62 and becomes an interrupt request signal for the injection processing interrupt routine. 1 of “1” and “0” from starter switch 52
The bit start signal is sent to I/O circuit 64. The input/output circuit (I/O circuit) 66 includes an MPU
A drive circuit is provided which receives a 1-bit injection pulse signal sent from the injection pulse width TAU and converts it into a drive signal. A drive signal from this drive circuit is sent to the fuel injection valve 30 to energize it. As a result, the amount of fuel corresponding to the pulse width TAU is injected. A/D converter 60 and I/O circuits 64 and 6
6 is the main component of the microcomputer
MPU62, random access memory (RAM)
68 and a read-only memory (ROM) 70 via a bus 72.
Data transfer takes place via. In the ROM 70, a main processing routine program, an interrupt processing routine program for every 30 degrees of crank angle, and other programs are stored in advance, as well as various data, tables, etc. necessary for these arithmetic operations. Next, the operation of the above-mentioned microcomputer will be explained using the flowcharts of FIGS. 3 and 4. First, the process for obtaining data representing the rotational speed NE will be explained with reference to FIG. MPU
62 executes the interrupt processing routine shown in FIG. 3 when a pulse signal every 30° crank angle is sent from the crank angle sensor 40 to determine the engine rotational speed NE.
Form data representing . That is, first step
At step 80, the value of the free run counter provided in the MPU 62 is read and the value is set as _C30 . Next, in step 81, the difference ΔC between the value _{C' 30 read during the previous crank angle 30° interrupt processing and the current value C 30 is calculated from ΔC = C 30 - C' 30 , and in} the next step 82, Calculate the reciprocal of the difference ΔC to obtain the rotation speed NE. That is, the calculation NE←A/ΔC is performed. However, A is a constant. The NE thus obtained is stored at a predetermined location in the RAM 68. In the next step 83, the calculation process C' ₃₀ ←C ₃₀ is performed so that the current counter value C ₃₀ is used as the previous read value in the next interrupt processing. Thereafter, after executing necessary processing, this interrupt processing routine is terminated and the process returns to the main processing routine. The data representing the intake pipe internal pressure PM and the cooling water temperature THW are obtained from the A/D converter 60.
When the MPU 62 executes interrupt processing in response to a D conversion completion interrupt, the data are taken into the computer and stored in the RAM 68. On the other hand, the MPU 62 executes the process shown in FIG. 4 during the main processing routine. First, in step 84, data on the rotational speed NE and cooling water temperature THW are read from the RAM 68. next step
At step 85, it is determined whether or not the engine starting has been completed by checking whether the rotational speed NE is 500 rpm or more. If “NO”, i.e.
If NE < 500 rpm and the engine is starting, proceed to step 86 and check the cooling water temperature at that time.
Remember THW as THW _st . Next, in step 87, a constant B is given to the additional increase value β used in step 93, which will be described later. next step
At 88, the basic injection pulse width is set to a constant value C, multiplied by a correction coefficient α based on the cooling water temperature, etc., and the product obtained by adding the invalid injection time TV of the fuel injection valve is given as the fuel injection pulse width TAU. That is,
Perform the calculation TAU←C・α+TV. in this way,
At startup, the basic injection pulse width is the intake pipe pressure.
It is set to a constant value regardless of PM and rotation speed NE. 2 representing the calculated injection pulse width TAU
The digital data is stored in RAM 6 in the next step 89.
8 is stored in a predetermined position. If NE<500rpm, the above process is repeated, and therefore
THW _st always contains the latest cooling water temperature THW at the time of startup. When NE≧500rpm, that is, when the engine is in a complete explosion state, the program continues from step 85.
Go to 90. In step 90, a process is performed to obtain a warm-up increase coefficient FWL from input data representing the cooling water temperature THW. The warm-up increase coefficient FWL is expressed in the form of a map as a function of the cooling water temperature THW (THW).
It is stored in ROM70. In particular, in this embodiment, a map of FWL is formed at equal intervals regarding the A/D converted value of the output voltage of the water temperature sensor 48. That is, as shown in Fig. 5, the cooling water temperature THW
The output voltage VTHW of the water temperature sensor 48 is not spaced at equal intervals, but is spaced at equal intervals with respect to the output voltage _VTHW of the water temperature sensor 48. THW−
Configuring the FWL map in this way simplifies the formula used for interpolation calculations, making it easier to map the warm-up increase coefficient TWL, and also reducing the number of steps in the program. In the next step 91, it is determined whether the current cooling water temperature THW is equal to or higher than a predetermined temperature G (for example, G=60 to 70°C). If THW≧G, it is assumed that warm-up has been completed, and the process proceeds to step 94, where no fuel increase process is performed after startup. If THW<G, it is assumed that the engine is cold and the process proceeds to step 92.
Therefore, if the engine is restarted after warming up,
The processes of steps 92 and 93 are not executed, and as a result, the post-startup fuel increase process is not performed. In the next step 92, the current cooling water temperature THW is
It is determined whether the temperature THW _st +A, which is higher than THW _st by a predetermined temperature A (=2 to 10° C.), has been exceeded. As mentioned before, THW _st is the cooling water temperature at the time of startup only and every time the main processing routine is executed.
Since the cooling water temperature is updated to THW, after the start, the cooling water temperature will remain approximately equal to the temperature at the end of the start. Therefore, in step 92, it is determined whether or not the cooling water temperature THW has risen above the predetermined temperature A from the cooling water temperature at the end of starting. “NO”
In this case, the program proceeds to step 93, where the warm-up increase coefficient FWL determined in step 90 is increased by the additional increase value β, and then the program proceeds to step 94.
On the other hand, if it is determined as “YES” in step 92,
That is, if the cooling water temperature THW has risen above the predetermined temperature A since the end of the start, the process proceeds to step 94 without adding the additional increase value β to TWL. At step 94, the rotation speed NE,
Import intake pipe internal pressure PM data. step
In 95, the basic injection pulse width TP is obtained by performing interpolation calculation using a map from the captured rotational speed NE and intake pipe internal pressure PM. ROM7
0 indicates the basic injection pulse width TP for the rotational speed NE and intake pipe pressure PM as shown in the table below.
(msec) map is prepared in advance,
In step 95, TP is determined from the input data NE and PM using this map.

[Table] Next, in step 96, the final fuel injection pulse width TAU is calculated from the basic injection pulse width, the warm-up increase coefficient FWL, other correction coefficients γ, and the invalid injection time TV of the injection valve 30 according to the following formula. It is calculated as follows. TAU←TP・FWL・γ+TV Next, in step 89 mentioned above, this TAU
Binary data representing the value is stored in the RAM 68, and the calculation process of the injection pulse width in the main processing routine is completed. Various methods are known for creating an injection pulse signal having a duration corresponding to TAU from the injection pulse width TAU calculated in this manner. For example, when the injection start timing signal occurs, the injection pulse signal is inverted to "1" and the value of the free run counter mentioned above at that time is known.
The value of this counter after TAU has elapsed is set in the compare register. When the value of the free run counter becomes equal to the set value of the compare register, an interrupt is generated and the injection pulse signal is set to “0”.
, thereby forming an injection pulse signal of a duration corresponding to TAU. The injection start timing signal is generated every time this interrupt processing routine is executed a predetermined number of times in the interrupt processing routine every 30 degrees of crank angle, a part of which is shown in FIG. Next, the effects of the embodiments described above will be explained. First, we will discuss the case where the engine is started from a cold state. In this case, as shown by the solid line in Figure 6, the warm-up increase coefficient starts from the end of startup.
FWL is additionally increased by a constant value B,
As a result, the amount of fuel supplied to the engine is increased accordingly. This post-start increase process is performed until the cooling water temperature THW rises by a certain temperature A from the point at which the start ends, and is not performed thereafter. In this way, the fuel increase process after starting is performed while the cooling water temperature rises by a predetermined temperature, so no matter what the operating condition is after starting, the increase in engine temperature Therefore, it is possible to perform the optimum amount increase process after starting. On the other hand, when the engine is restarted after being completely warmed up, the cooling water temperature THW is higher than G, so the warm-up increase coefficient FWL is not additionally increased. That is, the post-start increase process is not performed in this case. Therefore, when the engine is restarted after warming up, the air-fuel ratio will not become unnecessarily rich, and the exhaust gas purification characteristics will not deteriorate and the fuel efficiency will not deteriorate. In the processing routine shown in FIG. 4, whether or not the engine has finished starting is determined based on whether the rotational speed NE is 500 rpm or more. This is determined based on the starting signal from the starter switch 52. It's okay.
That is, steps 100 and 101 shown in FIG. 7 may be performed instead of steps 84 and 85 in FIG. 4. In step 100, only the data of the cooling water temperature THW is taken in, and in step 101, the starting signal is checked to determine whether or not the starter switch 52 is off. If “NO”, go to step 86;
If “YES”, proceed to step 90. In addition, in the above-mentioned embodiment, the additional increase value β was always maintained equal to the constant value B, but the additional increase value β can be adjusted as time passes after starting or according to the total number of revolutions of the engine after starting. It may be decreased gradually. That is, as shown in step 102 of FIG. 8, if the additional increase value β is decreased by a constant value D during the time interrupt processing routine that is executed at regular intervals, β will be reduced by the time elapsed after starting. gradually decreases with Furthermore, as shown in step 103 in FIG. 9, if the additional increase value β is decreased by a constant value E during the angle interrupt processing routine that is executed every time the engine rotates by a predetermined crank angle, β can be reduced. It gradually decreases depending on the total engine speed after starting. Furthermore, as shown in step 104 in FIG. 10, the additional increase value β is set to β←B-
If it is determined from F・(THW−THW _SH ), the additional increase value β will be determined according to the increase in cooling water temperature
can be gradually reduced. However, in the above formula, F is a constant. The chain line in FIG. 6 shows the case where the additional increase value β is controlled to gradually decrease as time passes, the rotational speed increases, and the cooling water temperature rises as described above. In the embodiments described above, the engine temperature is detected using the cooling water temperature, but it is clear that the engine temperature may be recognized by detecting the lubricating oil temperature or the engine block temperature. As explained in detail above, according to the present invention, when the engine temperature is higher than a predetermined temperature, the fuel increase process is not performed after starting, so that the air-fuel ratio becomes unnecessarily rich when restarting after warming up. There is no fear, and as a result, it is possible to improve exhaust gas purification characteristics and improve fuel efficiency.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an embodiment of the present invention, FIG. 2 is a block diagram of the control circuit shown in FIG. Fig. 5 is a characteristic diagram of an equally spaced map of the warm-up increase coefficient FWL with respect to the output voltage V _THW of the water temperature sensor, and Fig. 6 explains the operation of the present invention, and shows the relationship of the warm-up increase coefficient FWL with respect to the cooling water temperature THW. Characteristic diagrams showing Fig. 7, Fig. 8,
9 and 10 are flowcharts of part of the microcomputer's interrupt processing program. 12...Intake passage, 18...Throttle valve, 2
4...Pressure sensor, 28...Control circuit, 30...
Fuel injection valve, 40, 42... crank angle sensor,
48...Water temperature sensor, 52...Starter switch, 60...A/D converter, 62...MPU, 6
4, 66...I/O circuit, 68...RAM, 70
……ROM.

Claims (1)

[Claims] 1. Detecting the operating state of the internal combustion engine, determining the amount of fuel to be supplied to the engine according to the detected operating state,
On the other hand, the temperature of the engine is detected, it is detected whether or not the starting of the engine is completed, and the period after the completion of starting until the engine temperature rises by a predetermined temperature from the temperature at the end of starting is determined by the amount of fuel determined above. 1. A fuel supply amount control method for an internal combustion engine, characterized in that, in the fuel supply amount control method, the amount increase process is not performed when the engine temperature exceeds a predetermined value.