JPH0337355A - Fuel injection timing controller of engine - Google Patents

Abstract

PURPOSE:To improve the ignitability during lean burn operation by delaying fuel injection start timing as a set air fuel ratio is lean, in the case that fuel injection is controlled to have the air fuel ratio which is set to the lean side rather than a theoretical air-fuel ratio. CONSTITUTION:In a control unit 1 composed of a microcomputer ans the like, detection signals are inputted from various means which detect engine operation condition, such as an air flow meter 2, a throttle sensor 3, an idle switch 4, a crank shaft sensor 5, and a linear O2 sensor 6, and the like. After specified calculation operation is performed by the respective signals, a specified control signal is outputted to an injector 7. In this case, in the control unit 1, fuel injection is controlled so that it is at the air-fuel ratio set to a lean side rather than a theoretical air-fuel ratio. According to the air-fuel ratio, fuel injection start timing is delayed as it is lean so as to control the injector 7.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) This invention relates to a fuel injection timing control device for an engine, and more particularly, to a fuel injection timing control device for controlling engine fuel injection timing so that the air-fuel ratio is set leaner than the stoichiometric air-fuel ratio according to engine operating conditions. This invention relates to a technology for controlling fuel injection start timing in an electronically controlled engine that controls injection amount.

(Prior art) In an electronically controlled engine, various sensors detect the engine operating state, and when the operating state satisfies predetermined conditions,
A technique is known that controls the fuel injection amount so that the air-fuel ratio is set leaner than the stoichiometric air-fuel ratio depending on the operating state. Controlling the fuel injection amount so that the air-fuel ratio is leaner than the stoichiometric air-fuel ratio is called lean burn control.

Japanese Unexamined Patent Publication No. 60-209644 discloses, in an electronically controlled engine that performs lean burn control, control that changes the fuel injection start timing using the engine rotation speed and intake air amount as parameters while lean burn control is being executed. The technology has been disclosed. In this conventional technology, N during lean burn control.

In order to balance the contradictory characteristics of reducing the amount of X emissions and suppressing fluctuations in engine torque, an appropriate fuel injection start timing is determined using the engine speed and intake air amount as parameters.

(Problem to be solved by the invention) When performing lean burn control, the amount of fuel injected for the same amount of intake air is smaller than when controlling using the stoichiometric air-fuel ratio. If the start timing is the same as the stoichiometric air-fuel ratio control, the air-fuel mixture around the spark plug will be thinner due to the smaller fuel injection amount, resulting in poor ignition performance and lower fuel efficiency. Therefore, if the injection start timing is set late in accordance with the combustion characteristics during lean burn control, there is a problem that the time for vaporization and atomization of the fuel is not sufficient during stoichiometric air-fuel ratio control, and the amount of HC emissions increases.

This invention has been made in view of the above-mentioned conventional problems, and its purpose is to provide a fuel injection timing control device for an engine that can set an appropriate fuel injection start timing according to a set air-fuel ratio. be.

(Means for Solving the Problems) Therefore, in the present invention, in an engine that controls the fuel injection amount so that the air-fuel ratio is set leaner than the stoichiometric air-fuel ratio according to the operating state of the engine, the set air-fuel ratio is Accordingly, the leaner the engine is, the later the fuel injection start timing is controlled.

(Function) The closer the set air-fuel ratio is to the stoichiometric air-fuel ratio, the earlier the fuel injection start timing becomes, allowing sufficient time for vaporization and atomization of a large amount of fuel.Also, the leaner the set air-fuel ratio is than the stoichiometric air-fuel ratio, the faster the fuel injection starts. The start time is delayed, a relatively rich air-fuel mixture can be retained around the spark plug, and ignition performance is improved even with a small amount of fuel.

(Embodiment) FIG. 3 shows a schematic configuration of an engine control system to which the present invention is applied. As is well known, a control unit 1 using a microcomputer etc. receives intake air amount information from an air flow meter 2, throttle valve opening information from a throttle sensor 3, throttle fully closed signal from an idle switch 4, and crank angle. Crank angle and engine rotation speed information is supplied from the sensor 5, and air-fuel ratio (A/F) information is supplied from the linear 02 sensor 6. In addition, various sensors (not shown) supply information such as supply air temperature information and cooling water temperature information. Various engine status information is provided. control unit 1
executes predetermined arithmetic processing prescribed by the program based on this manual information, and controls fuel supply by the injector 7.

FIG. 2(A) shows air-fuel ratio control characteristics in an apparatus according to an embodiment of the present invention. As shown in the figure, the target value of the air-fuel ratio is basically mapped in advance using engine speed information and engine load as parameters, and this control map is used to determine the air-fuel ratio detected by the linear 02 sensor. Feedback control is performed so that the value becomes equal to the target value. In other words, this control changes the air-fuel ratio of the air-fuel mixture supplied to the engine depending on the operating state of the engine.

FIG. 2(B) shows the characteristics of the beam near 02 sensor 6. As shown in the figure, this sensor 6 generates a linear output that corresponds approximately proportionally to the actual air-fuel ratio within a certain range.

FIG. 1 shows the procedure of a fuel injection timing control routine, which is the main part of the present invention. The control unit 1 repeatedly executes this routine at sufficiently short cycles.

In the first step 101, the basic timing TO is determined from a map using the engine speed and load as parameters.

FIG. 2(C) shows an example of this TO map. ■
is idle zone, ■ is low-medium rotation, low-medium load zone, ■
is a high rotation, high load zone. The basic timing TO is that zone (2) is the fastest, zone (2) is the slowest, and zone (2) is an intermediate timing. In this way, the basic timing To is set in three stages.

In the next step 102, the target air-fuel ratio in the air-fuel ratio control routine for controlling the air-fuel ratio as described above is set to the stoichiometric air-fuel ratio (
14, 7) to determine whether it is lean. If the target air-fuel ratio is not leaner than the stoichiometric air-fuel ratio, the basic timing TO is set in the register Tl (step 103).

Furthermore, if the target air-fuel ratio is leaner than the stoichiometric air-fuel ratio (during the lean burn control described above), the timing correction value At is determined from a predetermined map using the target air-fuel ratio at that time as a parameter, and To + and dt are set in the register Tl. do. An example of a map of this timing correction value at is shown in FIG. 2(D). In this way, the leaner the target air-fuel ratio, the larger the correction value At. The larger the timing correction value at, the greater the amount of delay from the basic timing TO.

In other words, the leaner the target air-fuel ratio is, the later the corrected timing Tl-TO+lt becomes. The above is the process of step 104.

Next, it is determined whether or not to perform acceleration correction of the injection timing based on the operating condition (step 105). If acceleration correction is not performed, the timing Tl set in step 104 or step 105 described above is applied to the fuel injection control routine. Set (step 107). Note that when performing acceleration correction, step 106 is executed and the timing Tl set in step 104 or 103 is
The acceleration is corrected according to a predetermined algorithm, and the acceleration-corrected timing Tl is calculated in step 107.
This will set the fuel injection control routine.

Next, the timing Tl set in step 107 is B
It is determined whether the temperature is before TDC 270°C (step 108), and if it is after BTDC 270°C, the fuel injection control routine is performed using the timing T1 set in step 107 and another fuel injection amount control routine. The injector 7 operates in accordance with the injection time determined by the injector 7 and injects a specified amount of fuel at a specified timing. On the other hand, if it is before BTDC270°C, the process proceeds to step 109, and the timing Tl is before BTDC270°C.
The fuel injection control routine injects the amount of fuel specified by the injection timing BTDC270''CA.In other words, in steps 108 to 109, the fuel injection timing Tl is reset to 0°C A during the initial opening operation of the exhaust valve.
prevent the process from being excessively accelerated.

(Effects of the Invention) As described in detail above, in the fuel injection timing control device for an engine according to the present invention, during lean burn control, the leaner the air-fuel ratio is, the more the fuel injection start timing is determined. The closer the set air-fuel ratio is to the stoichiometric air-fuel ratio, the earlier the injection start timing will be, allowing sufficient time for vaporizing and atomizing a large amount of fuel.
The leaner the set air-fuel ratio is, the later the injection start timing becomes, allowing a small amount of fuel to gather around the spark plug. As a result, ignition performance during lean burn is improved, fuel efficiency is improved, and the amount of HC discharged during control under conditions close to the stoichiometric air-fuel ratio can be kept low.

[Brief explanation of drawings]

FIG. 1 is a flowchart of a fuel injection timing control routine in an engine fuel injection timing control device according to an embodiment of the present invention, FIG. 2 is an operational characteristic diagram of the same device, and FIG. 3 is a schematic configuration diagram of the same device. . 1... Control unit 2... Air flow meter 3... Throttle sensor 4... Idle switch 5... Crank angle sensor 6... ...Linear 02 sensor 7...Injector 2nd figure (S/I+) A/F (Lean)

Claims (1)

[Claims] In an engine that controls the fuel injection amount so that the air-fuel ratio is set leaner than the stoichiometric air-fuel ratio according to the engine operating state, the leaner the set air-fuel ratio, the later the fuel injection start timing is delayed. 1. A fuel injection timing control device for an engine, characterized in that the fuel injection timing control device controls the fuel injection timing so as to perform control.