JP2584746B2 - Fuel control system for electronic fuel injection engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fuel control device for an electronic fuel injection engine that changes a range of a restriction on a fuel injection amount in synchronization with a change in intake air charging efficiency.

(Prior Art) In such a fuel control device, a fuel injection amount (fuel injection time) is calculated in proportion to an air intake amount per one revolution of an engine, and fuel is injected based on the calculated amount. I have. In this case, an upper limit value is set for the fuel injection amount so that the calculated injection amount does not exceed the range. This restriction is applied to the case where the air intake amount is detected by an air flow meter, etc., to prevent erroneous detection of the intake amount due to the overshoot, etc., and to prevent the fuel from becoming excessively rich. To do that. Further, JP-A-55-9862
As in No. 4, the upper limit value of the fuel injection time width is changed according to the intake air intake amount or the engine speed.

On the other hand, there is a supercharged engine for the purpose of increasing the output of the engine. As such a supercharged engine, there is a turbocharged engine that performs supercharging by a turbocharger, or a variable intake engine that uses the inertia effect and the pulsation effect of intake air. In such a supercharged engine, for example, a turbocharged engine, a wastegate valve is provided to change a set value of the wastegate valve according to a cooling water temperature and a type of gasoline (high-octane, regular). By changing the supercharging pressure, the intake charging efficiency is made variable. In the variable intake engine (for example, JP-A-56-115819), the natural frequency of the intake path is switched by making the intake path longer in a low rotation range and shorter in the high rotation range. The aim is to maintain the intake air charging efficiency as high as possible over a wide rotation range.

(Problems to be Solved by the Invention) As described above, the fuel injection amount changes in accordance with the intake / intake air amount. Further, the amount of intake air greatly depends on the charging efficiency. Therefore, the original fuel injection amount is the intake air amount,
It should be determined in consideration of the number of rotations, filling efficiency, and the like.
However, in an engine in which the charging efficiency of the intake varies depending on the operating conditions as described above, the following problem occurs if the above-described limit value of the fuel injection amount is set ignoring the charging efficiency. I do. That is, for example, when the turbocharged engine is operated with low charging efficiency, the above-described limit value must be set low, but the limit value is set to a uniform value (this is originally set to Therefore, the fuel injection limit may not be effective. Because the limit value is set to a high value, for example, when the air flow meter overshoots and the fuel injection amount exceeds, the limit value does not work.

Further, in the variable intake engine, as shown in FIG. 11, there are two peaks of the charging efficiency. In this case, if a fixed limit value is set and the intake passage is varied, for example, if the control valve for changing the intake passage breaks down, the peak in FIG. The difference between the charging efficiency and the limit value becomes large in the rotation region where the peak disappears, and does not work as the restriction of the intake air amount similarly to the turbocharged engine described above.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems of the prior art, and has as its object to follow the change in intake charging efficiency in a variable intake engine, and to perform an intake restriction optimal for the charging efficiency. The point is to propose a fuel control device.

(Means for Solving the Problems) A fuel control device for an electronic fuel injection engine according to the present invention for realizing the above-described problems is based on the premise that the fuel control device has an intake passage having a variable shape. Fuel injection amount calculating means for calculating a fuel injection amount commensurate with the above, limiting means for limiting the fuel injection amount to a predetermined upper limit or less, and supplying fuel to the engine according to the fuel injection amount limited by the limiting means A variable fuel injection efficiency switching means for changing the natural frequency of the air intake passage by adjusting the shape of the air intake passage to change the air filling efficiency of the intake air supplied to the engine; Changing means for changing the upper limit value in accordance with switching of the charging efficiency.

(Operation) In the present invention having the above-described configuration, the fuel injection amount is adjusted to the intake air amount supplied to the engine and suppressed to a predetermined upper limit or less by the limiting means. On the other hand, when the intake charging efficiency is changed by the variable intake charging efficiency switching means according to a change in the operating conditions, the changing means changes the limit value according to the switching of the charging efficiency. Therefore, following the change in the intake charging efficiency, it is possible to perform the intake restriction optimal for the charging efficiency.

(Example) Hereinafter, an example according to the present invention will be described in detail with reference to the accompanying drawings.

<Concept of Basic Embodiment> FIG. 1 is a basic conceptual diagram of the embodiment. Fuel injection control system
102 controls the fuel injection amount of the fuel injection means 101, and performs limit control so that the injection amount falls within the range of the limit value 103. On the other hand, a supercharging means 105 is provided in the intake system, and the charging efficiency switching means 104 changes the charging efficiency of the supercharging means 105 and simultaneously changes / changes the value of the limit value 103 in accordance with the switching. .

The specific embodiments described below will be described with reference to an example applied to a so-called turbocharged engine and an example applied to a variable intake engine.

<Embodiment of Turbocharged Engine> FIG. 2 is a configuration diagram of an embodiment applied to a fuel control device and a turbocharged engine according to the present invention. Describing the main components in the figure, 2 is an intake air temperature sensor,
3 is an air flow meter, 4 is a turbocharger, 6 is a waste gate valve, 8 is a pressure responsive member connected to the waste gate valve 6, 9 is a linear solenoid, 12 is an intercooler, 10 is an injector, 11 is a throttle valve, and 20 is The control unit 24 is a manual switch.

It is well known that a wastegate valve 6 is generally provided to prevent a turbocharged engine from overcharging. FIG. 3 shows the control of the wastegate valve 6 in this embodiment. In FIG. 3, the linear solenoid 9 introduces air in response to a charging efficiency switching signal 21, and controls the pressure in the intake passage 22 through this opening to transmit the pressure to the pressure responsive member 8. When the pressure acting on the pressure responsive member 8 exceeds a predetermined value, the wastegate valve 6 is opened to bypass the exhaust gas, and the turbine speed is reduced to lower the supercharging rate. By the way, since the turbocharged engine is supercharged, the charging efficiency is affected by the temperature of the engine cooling water, the type of gasoline used, and the like. For example, when the engine is cold, the charging efficiency is reduced, and when using high-octane gasoline, knocking is unlikely to occur, so the charging efficiency is increased. Therefore, the charging efficiency should be changed in accordance with the change / change of these operating conditions, and if the charging efficiency changes, the actual intake air amount will change, so that the fuel injection amount also changes, and accordingly the fuel injection amount changes. Limits should also be changed.
Such control of the fuel injection amount and control of the limit value are performed by the control unit 20.

In the embodiment of FIG. 2, a description will be given by taking as an example a case where the change in the operating conditions described above is "changed between high-octane and regular gasoline". Since the gasoline used is of two types, high-octane and regular, the valve opening operation of the linear solenoid 9 in FIG. 3 is also of two types in this embodiment, fully open and fully closed. The control of the linear solenoid 9 according to the used gasoline is performed by the control unit 20 via the charging efficiency switching signal 21 according to the state of the manual switch 24. Since the signal 21 is an operation in which the linear solenoid 9 is only fully opened / fully closed (regular / high-octane), a binary signal of “1” / “0” is sufficient. If linear valve opening operation control of the linear solenoid 9 is performed according to a change in water temperature, the charging efficiency switching signal 21 may have a linear value.

The switching of the limit value of the fuel injection amount in accordance with the switching of the charging efficiency is performed as follows. FIG. 4 shows a state in which the limit values corresponding to the switching are stored in a ROM 25 in the control unit 20 in a map form. In addition, there are two types of limit values, an upper limit value and a lower limit value.
TP _max ). The map TP _max A is a high-octane specification map, and the TP _max B is a regular specification map. The value of what these values take is 6th
Shown in the figure.

<Example of Control of Turbocharged Engine> FIG. 5 shows a flowchart of control by the control unit 20 according to the embodiment. Step S1 is a part of the main routine, and reads correction values required for fuel calculation such as engine water temperature and intake air temperature. If an interrupt occurs in the main routine, the process proceeds to step S2 to determine whether the interrupt is for calculating the fuel injection amount. This will be determined by the rotation angle of the crankshaft. Next, in step S3, the engine speed N is acquired, and in step S4, the intake air amount is obtained from the air flow meter 3.
Know Q _a . In step S5, the fuel injection amount (pulse width TP) is calculated based on these values. In step S6, the logic value of the charging efficiency switching signal 21 is checked. As described above, if this signal 21 is "1", the linear solenoid 9 is fully closed, the pressure in the intake passage 22 is directly transmitted to the pressure responsive member 8, and the waste gate valve 6 opens earlier, Knocking does not occur even if regular gasoline is used. On the other hand, if the signal 21 is "0", the linear solenoid 9 is fully opened, and the pressure in the intake passage 22 is diluted with the atmosphere and transmitted to the pressure responsive member 8, so that the excess pressure is higher than when regular gasoline is used. It is controlled to supply pressure. At this time, in step S6, this signal 21 is checked. If "1" (regular), the process proceeds to step S7, and if "0" (high octane), the process proceeds to step S8. In step S7 or step S8, the upper limit value TP _max corresponding to the rotation speed at that time is read from the corresponding maps (FIG. 4). In step S9, this TP
_Max is compared with the TP calculated in step S5. As described above, TP _max becomes variable according to a change (change) in the filling efficiency.

If TP is larger than TP _{max in} step S9, TP is forcibly set to the value of TP _max in step S10. That is, limit control is performed.

In step S11, TP is further corrected in consideration of the correction value obtained in step S1. In step S12, this TP is set in a predetermined register in the control unit 20, and the process returns to the main routine. In the main routine, the driver is driven based on the value set in the register, and the injector 10 is driven. As a result, fuel corresponding to the pulse width of TP is injected.

<Effects of Turbocharged Engine Embodiment> As described above, when an attempt is made to inject fuel beyond the upper limit, the fuel injection amount is limited by the upper limit, and the upper limit is further changed / changed in the charging efficiency. Is changed according to the change / change, and as a result, an optimum upper limit value is set for the filling efficiency at that time. Therefore, for example, a limit is effectively applied to overshoot of the air flow meter 3 and the like. If the charging efficiency is made variable in response to a change in the water temperature, the valve opening operation of the linear solenoid 9 is also made linear according to the water temperature, and the map of TP _{max is set to} a map corresponding to the engine speed, the water temperature, etc. What should I do?

<Example of Application to Variable Intake Engine> FIG. 7 shows an embodiment in which the variable intake system is applied to a reciprocating engine. In the drawing, reference numeral 30 denotes a container for reducing the natural frequency of the intake passage 35 by changing the apparent passage length of the intake passage 35. Whether or not the container 30 communicates with the intake passage 35 is determined by the opening and closing operation of the communication valve 31. The opening and closing of the communication valve 31 is controlled by an actuator 33 driven by a filling rate switching signal 32.
It is performed by Whether the communication valve 31 has actually opened or closed can be confirmed by the logical value of the signal 34. FIG. 8 is a control flowchart of the opening and closing operation of the communication valve 31. By taking in the rotation speed N, and when the N is larger than a predetermined value N ₁ (see FIG. 10) (high-speed range), the valve is opened to increase the natural frequency,
In synchronization with the opening and closing operation of the intake valves of the engine to increase the charging efficiency, when the less than N ₁ (low speed range) by lowering the natural frequency and closed in synchronization postponed the opening and closing operation of the intake valves of the engine Increase filling efficiency.

FIG. 9 is a flowchart of control for changing TP _{max in accordance} with a change in filling efficiency. The steps shown in FIG. 9 replace step S6 in FIG. That is, the fifth
In the figure, Tp _max is switched according to the value of the charging efficiency switching signal 21, but in the embodiment of the variable intake, the TP _max is switched along with a signal 34 that reflects whether the communication valve 31 has actually opened or closed. . Incidentally, the value of the map of TP _max may be basically stored in the ROM 25 in the same manner as in the embodiment of the turbocharged engine, but the value is, for example, as shown in FIG.
The value of TP _max over the entire speed range 31 in a closed state, for example, the above-mentioned TP _max A, stores the value of TP _max over the entire speed range with open communication valve 31 in the ROM25 as TP _max B .
In this way, the communication valve 31 opens and closes according to the engine speed, and the charging efficiency becomes relatively gentle as shown in FIG. Therefore, in a state where the engine speed is gradually increased, the communication valve 31 is closed at the speed N1 and the filling efficiency is kept high accordingly, and the TP
_max also changes from the TP _max A to the TP _max B curve.

<Effects of the variable intake engine embodiment> The variable intake engine control device thus realized
The filling rate can be maximized both in the low-speed range and the high-speed range, and the TP _max is made variable in accordance with the filling efficiency changed in accordance with the rotation speed. Become. In particular, since the change of TP _max is controlled by the signal 35 for checking whether or not the communication valve 31 is actually connected, for example, even if the communication valve 31 fails, the filling efficiency is controlled by the valve.
31 will change, for example, according to a curve that remains open, and for limit control, the TP with the valve 31 open will also be used.
_{Since the} limit control is performed according to the curve of _max A, the difference between the filling efficiency and TP _max is small, so that the optimum limit control can be performed, and the deterioration of the emission does not occur.

In the above embodiment, the control of the natural frequency by the container 30 is performed, but the present invention can be applied to a method of changing the length of the intake path in various forms.

(Effects of the Invention) As described above, according to the present invention, it is possible to follow the change of the intake charging efficiency in the variable intake engine and perform the intake restriction optimal for the charging efficiency. Intake limit control can be reliably performed even for malfunctions.

[Brief description of the drawings]

Fig. 1 is a basic conceptual diagram of an embodiment to which the present invention is applied, Fig. 2 is a configuration diagram of an embodiment applied to a turbocharged engine, Fig. 3 is a diagram for explaining switching of charging efficiency in a turbocharged engine, FIG. 4 is a diagram for explaining how the limit values are stored in the ROM, FIG. 5 is a control flowchart according to the embodiment, and FIG. 6 is an engine speed N, injection pulse width TP, and limit value TP in the embodiment. diagram showing the relationship between _max, diagram of Fig. 7 embodiment in which the present invention is applied to the variable intake engine, Figure 8, Figure 9 is an extracted part of the control flowchart diagram, FIG. 10 FIG. 11 is a diagram illustrating a relationship between an engine speed, a charging efficiency, and TP _max in a variable intake engine. FIG. 11 is a diagram illustrating a relationship between an engine speed N, a charging efficiency, and a limit value TP _max in a conventional variable intake engine. is there. In the drawing, 1 ... air cleaner, 2 ... intake air temperature sensor, 3 ... air flow meter, 4 ... turbocharger, 6 ... waste gate valve, 7 ... catalyst, 8 ... pressure responsive member, 9
... Linear solenoid, 10 ... Injector, 11 ... Throttle valve, 12 ... Intercooler, 20 ... Control unit, 21, 32 ... Filling efficiency switching signal, 22, 23, 3
5… Intake passage, 24… Manual switch, 25… RO
M, 30 ... container, 31 ... communication valve, 33 ... actuator, 34 ... communication valve open / close signal.

Claims (1)

(57) [Claims] 1. A fuel control device for an electronic fuel injection engine having a variable shape intake passage, comprising: a fuel injection amount calculating means for calculating a fuel injection amount corresponding to an intake intake amount supplied to the engine; Limiting means for limiting the injection amount to a predetermined upper limit or less; fuel injection means for supplying fuel to the engine in accordance with the fuel injection amount limited by the limiting means; and adjusting the shape of the intake passage. Variable intake charging efficiency switching means for changing the charging efficiency of the intake air supplied to the engine by switching the natural frequency of the intake passage; and changing means for changing the upper limit value in accordance with the switching of the charging efficiency. A fuel control device for an electronic fuel injection engine, comprising: