JPS6065249A - Fuel injection method of internal-combustion engine - Google Patents

Abstract

PURPOSE:To prevent breathing by performing asynchronous injection one time upon opening of intake restriction valve from idling position during stoppage of synchronous injection while performing synchronous fuel injection for predetermined interval thereby bringing the air/fuel ratio of each cylinder to be approximately same. CONSTITUTION:When performing fuel injection, an electronic control circuit 54 will decide whether an intake restriction valve is at the idling position. If FFC has been set, the fuel injection valve is opened for time interval T2 to execute asynchronous fuel injection. Then the basic fuel injection time is operated from the pressure of suction pipe and the engine rotation while increment time D is added to the fuel injection time TAU to perform increment synchronous fuel injection. Consequently, the air/fuel ratio for each cylinder is brought to be same approximately resulting in prevention of breathing.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuel injection method for an internal combustion engine, and more particularly to a fuel injection method that performs synchronous fuel injection and stops the synchronous fuel injection under predetermined operating conditions.

[Prior art]

Conventionally, the basic fuel injection amount is determined based on the engine load (intake pipe pressure or intake air amount per engine rotation) and the engine speed, and basic fuel injection is performed using various correction coefficients such as intake air temperature and engine cooling water temperature. A synchronous fuel injection method is known in which the amount of fuel is corrected to determine the amount of fuel to be injected, the fuel injection valve is opened at every predetermined crank angle, and an amount of fuel corresponding to the amount of fuel is injected during the engine intake stroke. In this fuel injection method, from the viewpoint of improving fuel efficiency, during deceleration, that is, when the intake throttle valve is in the idle position (fully closed) and the engine speed is a predetermined value (for example, 2.50 Or
pm) or above, a so-called fuel cut is performed to stop synchronous fuel injection.

When accelerating again after such a fuel cut, acceleration performance will deteriorate unless fuel injection is restarted immediately. An idle switch is installed to maintain acceleration, and when the idle switch changes from on to off, that is, when the intake throttle valve opens from the idle position, asynchronous fuel injection is performed regardless of synchronous fuel injection to maintain acceleration. There is.

However, during fuel cut, the fuel that had adhered to the inner wall of the intake manifold evaporates, so the fuel injected during asynchronous fuel injection adheres to the inner wall of the intake manifold, resulting in less fuel being supplied to the combustion chamber. A problem arises in that the fuel ratio becomes Le// and the output decreases during acceleration (so-called breathing).This breathing occurs over a relatively long period of time when one fuel injector is installed upstream of the intake throttle valve. The air-fuel mixture is introduced into the combustion chamber through the intake passage (this is especially noticeable in so-called single-point injector internal combustion engines.To solve the above problem, asynchronous fuel injection is performed several times within a certain period of time to inject fuel onto the inner wall of the intake manifold. However, since the asynchronous fuel injection timing and the intake stroke of the engine do not necessarily match, depending on the operating conditions, the cylinder with a rich air-fuel ratio and the air-fuel ratio This results in problems such as lean cylinders, fluctuations in engine rotation, and deterioration of exhaust gas purification characteristics.

[Purpose of the invention]

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a fuel injection method for an internal combustion engine that allows an optimum air-fuel ratio to be obtained when fuel injection due to acceleration is restored after a fuel cut. purpose.

[Structure of the invention]

To achieve the above object, the present invention provides a conventional fuel injection method for an internal combustion engine in which asynchronous injection is performed once when an intake throttle valve is opened from an idle position while synchronous fuel injection is stopped, and the basic fuel injection amount is In this system, synchronous fuel injection is performed for a predetermined period of time, with the fuel injection amount being increased from the amount based on the fuel injection amount. This predetermined period is determined by time or the number of injections. According to the present invention, fuel is deposited on the inner wall of the intake manifold and supplied to the combustion chamber by asynchronous fuel injection, and then fuel is supplied to the combustion chamber by increased synchronous fuel injection that coincides with the engine intake stroke.

〔Effect of the invention〕

Therefore, according to the present invention, a unique effect can be obtained in that the fuel ratio of each cylinder can be made substantially the same to prevent suffocation.

[Embodiments of the invention]

Next, an example of an internal combustion engine to which the present invention is applied will be explained with reference to FIG.

Air cleaner 2 is connected to throttle body 6 via inlet vibe 4. One fuel injection valve 8 is installed on the upstream side of the throttle body 6, and on the downstream side of the fuel injection valve 8, there is an intake valve that adjusts the amount of air-fuel mixture sucked into the combustion chamber of the engine in conjunction with the accelerator pedal. A throttle valve 10 is arranged. A throttle switch 12 is attached to the intake throttle valve 10, which is turned on when the intake throttle valve 10 is at the idle position and turned off when the intake throttle box 10 is opened from the idle position. Further, on the downstream side of the intake throttle box 10, a throttle body 6 that detects the pressure of the intake pipe is provided.
is connected to an intake manifold 16 having branch pipes connected to each cylinder of the engine, and an intake temperature sensor 18 is attached to the intake manifold 16 to measure the intake air temperature from the temperature of the air-fuel mixture passing through the intake manifold. ing. The upstream bottom portion 16H of the intake manifold 16 is provided with a riser portion 20 through which engine cooling water is circulated to heat the air-fuel mixture.

Reference numeral 22 designates a well-known engine body, in which a combustion chamber 28 is formed by the bottom surface of a piston 24 and the inner wall of a cylinder 26, and an air-fuel mixture sucked in through an intake valve 30 is ignited by a spark plug 32. A quarter jacket 34 is formed around the cylinder 26 , and engine cooling water temperature is circulated through this water jacket 34 .
etc. are cooled. An engine cooling water temperature sensor 38 is attached to the cylinder block 36 to detect the temperature of the engine cooling water in the water jacket 34. An exhaust manifold 42 is connected to an exhaust port (not shown) of the cylinder head 40, and an exhaust manifold 42 is connected to the downstream side of the exhaust manifold 42. 0, which detects the residual oxygen concentration in the exhaust gas on the side
A sensor 44 is attached. Further, the exhaust manifold 42 is connected to an exhaust pipe 48 via a catalyst conduit 46 filled with a three-way catalyst.

Spark plug 32 is connected to control circuit 54 via distributor 50 and igniter 52 . The distributor 50 includes an engine rotation angle sensor 56 and a cylinder discrimination sensor 5s, each of which includes a signal rotor fixed to the distributor shaft and a pickup fixed to the distributor nose.
The mounting ff is leaking. This cylinder discrimination sensor 58 has 6
In the case of a cylinder engine, the Guistrybukeshaft car 1
For every revolution, the engine rotates twice (720'
CA) at the reference position (for example, top dead center of a specific cylinder)
The engine rotation angle sensor 56 outputs one pulse every 30 degrees CA, for example.

The control circuit 54 includes a central processing unit (C)'[1] 60 equipped with an arithmetic logic unit and registers, a read-only memory (ROM) 62 that stores control programs, etc., a random access memory (RAM) 64, and a backup RAM ( B
2
' Contains A, TE. A cylinder discrimination signal from the cylinder discrimination sensor 58, an engine rotation speed signal from the engine rotation angle sensor 56, and an idle signal from the throttle switch 12 are input to the l1068, and the fuel injection valve 8 is inputted via a drive circuit (not shown). A fuel injection signal for controlling the igniter 52 and an ignition signal for controlling the igniter 52 are output.

The ADC 70 also includes an intake pipe pressure signal from the pressure sensor 14, an intake temperature signal from the intake temperature sensor 18, a water temperature signal from the water temperature sensor 38, and 0. Air-fuel ratio signals from the sensor 44 are input, and these signals are sequentially converted into digital signals according to instructions from the CPU 60. ROM6 above
2 includes a control program shown in the following processing routine, and a count value N for 1n during which the increased amount synchronous fuel injection is executed.
, fuel cut rotation speed, etc. are stored in advance.

Next, an embodiment in which the present invention is applied to the engine as described above will be described in detail. FIG. 3 shows the main routine of this embodiment. First, in step 100, it is determined whether or not the fuel is being cut. If the fuel is being cut, the flag FFcy is reset in step 102. If the fuel is not being cut, that is, the synchronization is performed. When fuel injection is being performed, the flag FFC is set in step 101.
Set.

FIG. 4 shows a routine for executing asynchronous fuel injection. In step 103, it is determined whether the throttle switch is on, that is, whether the intake throttle valve 10 is in the idle position.

When the throttle switch is on, step 104 is NO), (5HI J-L+SU L II J-”
/l When the PRO 1 sotol switch is off, it is determined in step 105 whether the flag FLL has been reset. If the 7-lag FLL has been reset, and the throttle switch is in the OFF state, the process returns directly. If the flag FLL is set, that is, when the throttle switch changes from on to off, the flag is reset in step 106. FLL is reset, and in step 107 it is determined whether the flag F'FC, which is reset during the 7-well cut, is set. When the flag Ii''FC is set, that is, when synchronous fuel injection is being performed, time T is reached in step 108.

In other words, during the 7 fuel cut, in step 109, the count value C0UNT corresponding to the number of injections for executing the increased amount synchronous fuel injection is set to N (for example, 2
), in step 110, the fuel injection tank is opened for a period of time Ts (for example, 5m5ec) to execute asynchronous fuel injection.

FIG. 5 shows a control routine for increasing synchronous fuel injection. First, in step 111, a count value COUNT is set in the A register of the arithmetic logic unit, and in step 11
In step 2, it is determined whether the value of the A register is O or not. If the value of the A register is 00, the increase time is set to O in step 113 and the process proceeds to step 117. If the value of the A register is not 0, the value of the A register is decremented by l in step 114 and the process proceeds to step 115. The value of the A register is loaded into the count value CO[JNT, and in step 116 the increase time is set to T (for example, 4 ms), and then in step 117
Proceed to.

In step 117, basic fuel injection is performed for the basic fuel injection amount based on the intake pipe pressure and engine speed.

In addition to calculating the time, the basic fuel injection time is corrected using various correction coefficients to obtain the fuel injection time TAU, and the increase time is added to this fuel injection time TAU. Step 118
Then, the fuel injection valve is opened for a time corresponding to this added time to perform increased synchronous fuel injection.

As a result of the above, when the throttle switch is turned from on to off during fuel injection, time T! After the asynchronous fuel injection for the time Tsl is executed, the normal synchronous fuel injection is executed, and when the throttle switch is turned from on to off during the fuel cut, the asynchronous fuel injection for the time Tsl is executed, and then the tray corresponding to the increase time is executed. Increased amount synchronous fuel injection in which the amount of fuel is increased is performed a predetermined number of times (twice in the above example), and then normal synchronous fuel injection is performed.

7 Let the timing of asynchronous fuel injection and synchronous fuel injection when the throttle switch changes from on to off during fuel cut be the time 'rl (i In5eC.

The time period is shown in Fig. 6 as 4 m5ec.

In addition, although the example in which the increased amount synchronous fuel injection is executed a predetermined number of times has been described above, the predetermined period of time (for example, 1() +n
5ec) Increased synchronous fuel injection may be performed.

In the above, an example in which the present invention is applied to a single-point injector type engine has been described, but the present invention is not limited to this. A fuel injection valve is attached to the intake manifold for each cylinder, and the intake stroke of each cylinder is It is also possible to apply it to an independent injection type engine that injects fuel. With this independent injection engine, if the time during the fuel cut is particularly long, there will be a single point in during the fuel cut. As with the Ekta engine, the fuel adhering to the inner wall of the intake manifold evaporates.
The same problem as above arises. In addition, although the above description has been made regarding an engine in which the basic fuel injection amount is determined based on the intake pipe pressure and the engine rotation speed, the present invention is applicable to an engine in which the basic fuel injection amount is determined based on the intake air amount per engine rotation and the engine rotation speed. can also be applied.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an example of an engine to which the present invention is applied, FIG. 2 is a block diagram showing an example of the control circuit of FIG. 1, and FIG. 3 is a main routine of an embodiment of the present invention. Flow chart, FIG. 4 is a flow chart showing the joint JtJ+fuel injection control routine of the above embodiment, FIG. 5 is a flow chart showing the synchronous fuel injection control routine of the above embodiment, and FIG. 6 is a flow chart showing the asynchronous fuel injection control routine of the above embodiment. It is a diagram showing an example of timing of synchronous fuel injection. 8...Fuel injection valve, lO...Intake throttle valve, 54...Control circuit. Agent Tatsuyuki Unuma (and 1 other person) Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] (1) Synchronous fuel injection is performed in which fuel is injected at every predetermined crank angle based on the basic fuel injection amount determined by the engine load and engine speed, and the intake throttle valve is in the idle position and the engine speed is above a predetermined value. In the fuel injection method for an internal combustion engine, in which the synchronous fuel injection is stopped when the synchronous fuel injection is stopped and the intake throttle valve is opened from the idle position, the asynchronous injection is performed once and based on the basic fuel injection amount. 1. A fuel injection method for an internal combustion engine, characterized in that synchronous fuel injection is performed for a predetermined period with an increased fuel injection amount.