JPS5825525A - Electronically controlled fuel injection method - Google Patents

Abstract

PURPOSE:To ensure a prescribed feed quantity of fuel at a high load and the like, by injecting the fuel from a main fuel injection valve and starting fuel injection valve when a flow of fuel injection after starting exceeds a maximum flow of fuel injection of the main fuel injection valve. CONSTITUTION:A pump 42 feeds fuel from a fuel tank 43 to a main fuel injection valve 41 througi a fuel passage 44. A starting fuel injection valve 46, injecting excess fuel at a cold temperature start, is provided to a surge tank 4 and connected to the fuel passage 44. An electronic control unit 40 controls the main fuel injection valve 41, starting fuel injection valve 46, bypass flow control valve 22, exhaust gas recirculation (EGR) control valve 24, ignition coil 45, etc. When a flow of fuel injection after starting exceeds a maximum flow of fuel injection of the main fuel injection valve 41, fuel is injected from the both fuel injection valves 41, 46.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronically controlled fuel injection method for an engine that can expand the range of fuel injection flow rates.

In an electronically controlled fuel injection engine, a main fuel injection valve is provided for each cylinder, and the fuel injection valve is operated by a voltage signal from a CPU (central processing unit) to perform predetermined air-fuel ratio control. FIG. 1 shows the limits of the injection time of the fuel injection valve.

Sl is a synchronization signal generated by the crank angle sensor every time the crankshaft rotates 360 degrees, and S2 is an injection signal sent to the fuel injection valve. During the period when the injection signal S2 is at a low level, the fuel injection valve is opened and fuel is injected into the intake system, and during the period when the injection signal S2 is at a high level, the fuel injection valve is closed and fuel injection to the intake system is stopped. The fuel is injected in synchronization with the crank angle. In such a fuel injection valve, the minimum injection time τmin is limited due to the mechanical movement of the valve body of the fuel injection valve, and if the injection time is less than the minimum injection time τmin, fuel injection becomes irregular and metering becomes impossible. , and the maximum injection time τmax is such that a predetermined rest time τS (τS is constant regardless of the engine rotation speed) is provided between the fuel injection times, and the interval of the injection signal S1 is set as the engine rotation speed increases. Therefore, there is a limit to the control range of the fuel injection flow rate. Figure 2 shows the maximum values Qmax a, Qmaxb, and minimum value Q of the fuel injection amount per injection of fuel injection valves A and B.
Indicates mina and Qminb.

The nozzle diameter of fuel injection valve B is larger than the nozzle diameter of fuel injection valve A, and even if the nozzle diameter is changed, the maximum values Qmax a, Qmax b' and the minimum values Qmin a, Qminb of the fuel injection amount are the injection time rmax ,
Significantly limited by tmin. Figure 3 shows the air-fuel ratio control range according to the injection time τmax and 1 min, the horizontal axis is the engine rotation speed, the vertical axis is the air filling efficiency in the combustion chamber, and the control limit is determined using the air-fuel ratio A/F as a parameter. Illustrated. For example, with respect to the control limit by 1min, the minimum fuel efficiency for A/F=14.7 is about 12% regardless of the engine speed, and the fuel injection amount must be reduced due to the minimum fuel injection time τmin. It can be seen that it is impossible to maintain A/F=14.7 or more with a filling efficiency of 12% or less. Also, τma
For example, the maximum photonic efficiency curve for A/F = 10 is shown for the control limit due to x, and it is not possible to increase the injection amount due to the maximum fuel injection time τmax,
In the range above the curve, it is impossible to maintain A/F=10 or less.

An object of the present invention is to provide an electronically controlled fuel injection method that can expand the restricted range of fuel injection flow rate and expand the control range of air-fuel ratio despite the limitations on the maximum and minimum injection times of the main fuel injection valve. The goal is to provide the following.

In order to achieve this object, according to the electronically controlled fuel injection method of the present invention, starting fuel is conventionally provided separately from the main fuel injection valve, exclusively for injecting an increased amount of fuel at the time of cold starting. Focusing on the injection valves, if the fuel injection flow rate after startup exceeds the maximum fuel injection flow rate of the main fuel injection valve, fuel is injected from the main fuel injection valve and the starting fuel injection valve.

The present invention will be described in detail with reference to FIG. 4 and subsequent figures.

Air taken in from the air cleaner 1 is sent to the combustion chamber 8 of the engine 7 through an intake passage 12 that includes an air flow meter 2, a throttle valve 3, a surge tank 4, an intake boat 5, and an intake valve 6. The throttle valve 6 is linked to an accelerator pedal 13 in the driver's cab. The combustion chamber 8 is divided by a cylinder head 9, a cylinder block 10, and a piston 11, and the exhaust gases formed by the combustion of the mixture are passed through an exhaust valve 15, an exhaust bow 16, an exhaust manifold 17, and an exhaust pipe 18. released into the atmosphere. The bypass passage 21 connects the upstream of the re-valve 3 and the surge tank 4, and the bypass flow control valve 22 is operated by an electric control valve such as a pulse motor or an electromagnetic valve to control the flow cross-sectional area of the bypass passage 21. . An exhaust gas recirculation (EGR) passage 23 connects the exhaust manifold 17 and the surge tank 4, and an on-off valve type exhaust gas recirculation (BGR) control valve 24 opens and closes the EGR passage 23 in response to electrical pulses. . The intake air temperature riser 28 is provided in the air flow meter 2 to detect the intake air temperature, and the throttle position sensor 29 detects whether or not the throttle valve 3 is at an idling opening.

The water temperature sensor 30 is attached to the cylinder block 10 to detect the cooling water temperature, that is, the engine temperature, and the air-fuel ratio sensor 31, known as an oxygen concentration sensor, is attached to the collecting part of the exhaust manifold 17 to detect the oxygen concentration in the collecting part. The crank angle sensor 32 detects the crank angle of the crankshaft from the rotation of the shaft 34 of the power distributor 33 coupled to the crankshaft (not shown) of the engine body 7, and the vehicle speed sensor 35 detects the crank angle of the crankshaft from the rotation of the shaft 34 of the power distributor 33 coupled to the crankshaft (not shown) of the engine body 7. Detects the rotation speed of the shaft. These sensors 2 , 28 , 29 , 30 , 31 , 32 , 3
5 and the voltage of the storage battery 37 are sent to the electronic control section 40.

The main fuel injection valve 41 is provided near the intake boat 5 in correspondence with the cylinder, and the pump 42 sends fuel from the fuel tank 43 to the main fuel injection valve 41 through a fuel passage 44. Furthermore, a starting fuel injection valve 46 that injects an increased amount of fuel during cold starting is provided in the surge tank 4 and connected to the fuel passage 44 .

The electronic control unit 40 calculates the fuel injection amount using input signals from each sensor as parameters, and sends an electric pulse having a pulse width corresponding to the calculated fuel injection amount to the main fuel injection valve 41.

The electronic control unit 40 also controls the bypass flow control valve 22, EG
It controls the R control valve 24, the solenoid valve 47 (FIG. 5) of the hydraulic control circuit of the automatic transmission, the ignition coil 45, and the starting fuel injection valve 46. The secondary side of the ignition coil 45 is connected to the power distributor 33.

FIG. 5 shows details of the electronic control section 40.

CPU (Central Processing Unit) 4 consisting of a microprocessor
8. ROM (read only memory) 49, RAM (random access memory) 50, another RAM that can be supplied with power from the auxiliary power supply and retain memory even when the engine is stopped 51, A/DC (analog/digital) converter with multiplexer 52 , buffered Ilo (input/output) devices 53 are connected to each other via a bus 54. RAM 51 may be non-volatile memory. air flow meter 2,
Intake temperature sensor 28, water temperature sensor 30, air-fuel ratio sensor 3
1 and the output of the storage battery 37 are sent to the A/D converter 52. Further, the outputs of the throttle position sensor f29 and the crank angle sensor 32 are sent to the I10 device 53, and are sent to the bypass flow control valve 22, EGR control valve 24, main fuel injection valve 41, ignition coil 45, starting fuel injection valve 46, and The solenoid valve 47 receives input from the CPU 48 via the I10 device 53.

FIG. 6 is a flowchart of five actual examples. Step 61
Now, calculate the effective injection time τe.

τe=K・〜−−=〜・・・・・・・・・・・・(1
) Ne-U where K is a constant, Ne is the engine rotation speed, and U is the output voltage of the air flow meter 2. The larger the intake air flow rate is, the smaller U is. In step 62, the actual injection time τi
Calculate.

τi = τex α×τ■ ...1...Φken-(2) However, α is a correction coefficient related to the air-fuel ratio feedback signal, cooling water temperature, etc., and τV is the invalid injection time. The fuel injection amount at can be considered to be zero.

In step 63, τmax is calculated.

60000 (3) Ne τS is the pause time defined in Figure 1, and the units of Ne are r, p, m, and te, so the molecule is 60 x 1000
It becomes. In step 64, it is determined whether τi>τmax, and if the determination result is positive, the process proceeds to step 65, and if not, the process proceeds to step 67. τi>τmax means that the fuel injection flow rate after the initial operation exceeds the fuel injection flow rate of the main fuel injection valve 41.

In step 65, the starting fuel injection valve 46 is energized, and fuel is injected from the starting fuel injection valve 46.

In the starting fuel injection valve 46 of the embodiment, there is no downtime for each injection, and if the condition τi>τmax is satisfied in the next fuel injection in the main fuel injection valve 41, the starting fuel injection valve 46 is kept energized continuously and injects fuel without interruption. Step 66
Now, the fuel injection time τi of the main fuel injection valve 41 is calculated again from the following equation (4). The recalculated τi is (
4) As shown in the equation, the time corresponding to the amount of twisting material injected from the starting fuel injection valve 46 is subtracted from τi calculated in step 62.

r i-,, m---r to n/Ne-, ,,,,,,
(4) where m is the flow coefficient of the main fuel injection valve 41, n is the flow coefficient of the starting fuel injection valve 46, and n/Ne is the amount of fuel injected from the starting fuel injection valve 46 per crankshaft rotation. be equivalent to. In step 67, the starting fuel injection valve 4
6 is kept closed. Therefore, when τi≦τmax, fuel injection from the starting fuel injection valve 46 is not performed. In step 68, a pulse signal is sent to the main fuel injection valve 41 to open the main fuel injection valve 41 for an injection time τi. The fuel injection time of the main fuel injection valve 41 is the fuel injection time τi determined by equation (2) when the fuel injection flow rate is less than or equal to the maximum fuel injection flow rate of the main fuel injection valve 41, and the fuel injection flow rate is the main fuel injection flow rate. If the maximum fuel injection flow rate of the injection valve 41 is exceeded, the fuel injection time τI is determined by equation (4). When τi≦τmax, fuel is injected only from the main fuel injection valve 41.

As described above, according to the present invention, when the fuel injection flow rate exceeds the maximum fuel injection flow rate of the main fuel injection valve, fuel is injected from the main fuel injection valve and the starting fuel injection valve, so that the intake system It is possible to increase the maximum value of the fuel supply flow rate at high speeds and high loads, and it is possible to secure the specified fuel supply flow rate even at high speeds and high loads, increasing output and reducing exhaust gas temperature due to rich mixture vaporization when the catalyst is overheated. can be achieved. Furthermore, as a result of using the main fuel injection valve and the starting fuel injection valve together, it is possible to use the main fuel injection valve with a small nozzle diameter, that is, a small minimum fuel injection amount, and the minimum value of the fuel supply flow rate in the intake system. This makes it possible to improve fuel efficiency under low load and idling conditions, and to suppress the release of harmful components.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the limit of the injection time of the main fuel injection valve;
FIG. 2 is a graph showing the limit of the fuel injection amount of the main fuel injection valve, FIG. 3 is a graph showing the control limit of the air-fuel ratio related to charging efficiency, and FIG. 5 is a block diagram of the electronic control section in FIG. 4, and FIG. 6 is a flow chart of an embodiment of the present invention. 8... Combustion chamber, 40... Electronic control unit, 41... Main fuel injection valve, 46... Starting fuel injection valve.

Claims (1)

[Claims] In an electronically controlled fuel injection method for an engine whose intake system includes a main fuel injection valve that injects fuel corresponding to each cylinder and a starting fuel injection valve that injects an increased amount of fuel when starting at a low temperature, An electronically controlled fuel injection method, characterized in that when the fuel injection flow rate exceeds the maximum fuel injection flow rate of the main fuel injection valve, fuel is injected from the main fuel injection valve and the starting fuel injection valve.