JPH0362894B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for controlling the amount of fuel supplied to an internal combustion engine in accordance with operating state parameters of the engine. [Prior art] The rotational speed of the engine and the pressure inside the intake pipe are detected, the basic injection pulse width of the fuel injection valve or the fuel supply amount control valve in the carburetor is determined according to these detected values, and the engine temperature, for example, the cooling A fuel supply amount control method that detects water temperature, corrects the basic injection pulse width according to this detected value, and adjusts the amount of fuel actually supplied according to the corrected injection pulse width is a good method. Are known. 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, the rotational state of the engine is unstable, except when the engine is completely warmed up, even if the above-mentioned warm-up increase correction is performed. Immediately after the engine is started, unless the engine is completely warmed up, the circulating oil is cold, so the lubrication effect is insufficient, and the wall temperature of the combustion chamber is low, making it difficult to achieve sufficient combustion. During the unstable period from such an unstable rotational state to a stable rotational state, it is necessary to make the air-fuel ratio of the engine richer. This is the reason why, in addition to the warm-up increase correction, the increase correction after startup is required. In the conventional increase correction after starting, the amount is gradually decreased from the initial value at the end of starting (see Japanese Patent Laid-Open No. 57-46031). [Problem to be solved by the invention] However, the above-mentioned conventional type
46031), it is difficult to select an appropriate value for the temperature after all starts due to the combination of the initial value and the gradual reduction rate. Either or both of these are selected so that the rich period is longer. As a result, there was a problem in that HC and CO emissions increased. Therefore, the object of the present invention is to increase the amount after starting.
The purpose is to prevent an increase in HC and CO emissions. [Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention detects the engine temperature, and also detects whether or not the starting of the engine has been completed, and detects whether or not the engine temperature has changed after the engine has started. The reason is that the amount of fuel supplied to the engine is increased during the period until the temperature rises by a predetermined value from the temperature at the end. [Operation] According to the above-mentioned means, the starting point of the post-starting fuel increase period is set as the starting point, and the ending point is set as the point in time when the engine temperature rises by a predetermined temperature from the engine temperature at the end of starting. In other words, the present invention focuses on the fact that there is a strong correlation between the period during which the rotational state of the engine is unstable and the engine temperature rise value, and increases the amount after starting when a predetermined engine temperature rise value is obtained. I decided to cancel it. [Example] 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 take-out port 24 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.
a 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 combusted 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 the crankshaft (not shown) rotates 30° and 360°, respectively. , the pulse signal for each 360° crank angle is line 46.
are sent to the control circuit 28 via the respective channels. 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, where it undergoes A/D conversion selected according to 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 having a duration corresponding to the injection pulse width TAU sent from 62 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 is transferred 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 receives a pulse signal every 30° crank angle from the crank angle sensor 40, executes the interrupt processing routine shown in FIG. 3, and determines 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 △C between the value C' ₃₀ read during the previous crank angle 30° interrupt processing and the current value C ₃₀ is calculated from △C = C ₃₀ - C' ₃₀ .
In the next step 82, the reciprocal of the difference ΔC is calculated to obtain the rotational 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.
After executing the corresponding 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 drop 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 PM
and is set to a constant value regardless of the rotation speed NE. The binary data representing the calculated injection pulse width TAU is stored in the RAM 68 in the next step 89.
is stored in a predetermined location. 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 f(THW) of the cooling water temperature 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 extremely easy to map the warm-up increase coefficient FWL, and also reducing the number of steps in the program. . 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 FWL. At step 94, the rotation speed NE is determined from RAM68.
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. ROM70
Inside is the basic injection pulse width TP (msc) for the rotational speed NE and intake pipe pressure PM as shown in the table below.
Maps are prepared in advance, and the steps
In 95, TP is obtained from the input data NE and PM using this map.

〔Effect of the invention〕

As explained above, according to the present invention, focusing on the fact that the period of unstable rotation after startup is strongly related to the increase in engine temperature, the increase in fuel consumption after startup is discontinued when the engine temperature rises to a predetermined temperature. can prevent an increase in

[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)

[Scope of Claims] 1. A method for detecting the operating state of an internal combustion engine and controlling the amount of fuel supplied to the engine according to the detected operating state, wherein the temperature of the engine is detected, and The internal combustion engine is characterized in that the amount of fuel supplied to the engine is increased during a period after the engine temperature reaches a predetermined temperature rise from the temperature at the end of the engine engine after the engine temperature has started. fuel supply amount control method. 2. The fuel according to claim 1, wherein the amount increasing process is performed during a period until the engine temperature rises by a predetermined temperature from the temperature at the end of starting after starting, using an increasing value that is kept constant during the period. Supply amount control method. 3. Claim 1, wherein the increase processing for the period after the end of the start until the engine temperature rises by a predetermined temperature from the temperature at the end of the start is performed using an increase value that is gradually decreased as time passes. The fuel supply amount control method described. 4. A patent in which the amount increase process is performed during the period until the engine temperature rises by a predetermined temperature from the temperature at the end of startup after the end of startup, using an increase value that is gradually decreased in accordance with the total number of revolutions of the engine after the end of startup. A fuel supply amount control method according to claim 1. 5. Claim No. 5, wherein the amount increasing process is performed during the period after the end of the start until the engine temperature rises by a predetermined temperature from the temperature at the end of the start, using an increase value that is gradually decreased in accordance with the rise in the engine temperature. The fuel supply amount control method according to item 1.