JP2569457B2 - Fuel injection control device for internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fuel injection control device for an internal combustion engine,
The present invention relates to a fuel injection control device for an internal combustion engine that controls fuel injection timing during acceleration.

[Conventional technology]

Conventionally, a basic fuel injection time is calculated based on an engine speed and an engine load (intake pipe pressure or intake air amount per one engine revolution), and the basic fuel injection time is calculated based on an intake air temperature, an engine cooling water temperature, and the like. The fuel injection time (pulse width) is obtained by correcting the time, and the fuel is injected for each cylinder or each group of cylinders including two or more cylinders by opening the fuel injection valve for a time corresponding to the fuel injection time. Injection control devices are known. Further, in the internal combustion engine equipped with such a fuel injection control device, the fuel from the fuel injection valve to the intake valve is arranged so that all of the fuel injected from the fuel injection valve reaches the intake valve at the intake top dead center of the cylinder. The fuel injection is terminated before the intake top dead center in consideration of the flight time of the vehicle. In such an internal combustion engine, since all of the fuel injected at the intake top dead center reaches the vicinity of the intake valve, the fuel is effectively sucked into the combustion chamber during the intake stroke, and the maximum torque during steady operation is increased. As a result, the emission during steady operation is improved.

[Problems to be solved by the invention]

However, when the internal combustion engine equipped with such a conventional fuel injection control device is accelerated from a deceleration state, the amount of intake air sharply increases, so that the amount of fuel injection sharply increases, and substantially all of the injected fuel is supplied to the combustion chamber. To be inhaled. For this reason, as in the conventional case, in the fuel injection in consideration of the flight time of the fuel, the torque rapidly rises due to an increase in the fuel injection amount in the initial stage of acceleration, which may cause vibration of the vehicle which is a spring mass system. There was a problem.

[Means for solving the problem]

The present invention relates to a fuel injection control device for an internal combustion engine that calculates a fuel injection amount at a predetermined cycle in order to prevent vehicle vibration from occurring at the time of acceleration. A crank angle detecting means for outputting a crank angle signal, and controlling the fuel injection valve based on the crank angle signal so as to terminate the fuel injection at a predetermined timing before the intake top dead center based on the crank angle signal during steady operation, and accelerating the engine. And control means for controlling the fuel injection valve so that the fuel injection is terminated earlier than the predetermined time when is detected.

[Action]

In the present invention, during the steady operation, the fuel injection valve is controlled based on the crank angle signal so that the fuel injection ends at a predetermined timing before the intake top dead center. On the other hand, when the acceleration of the engine is detected, the fuel injection valve is controlled so that the fuel injection ends before the predetermined timing. As described above, by further advancing the fuel injection end timing, the fuel injection time is calculated based on the engine speed and the engine load before the fuel injection time calculation timing during the steady operation,
When the fuel injection time is slightly shortened, the fuel injection amount is slightly reduced. In addition, since the fuel injection is terminated much before the intake valve opens, the fuel adheres to the intake manifold wall or the like, and the fuel is gradually sucked in from the time the intake valve opens.

〔The invention's effect〕

Therefore, according to the present invention, it is possible to obtain an effect that it is possible to prevent a sudden increase in the fuel injection amount in the initial stage of acceleration and to prevent the occurrence of vehicle vibration during acceleration.

〔Example〕

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In this embodiment, after the fuel injection timing is advanced at the time of acceleration, the fuel injection end timing is gradually delayed until the fuel injection end timing at the time of steady operation according to the time, the engine speed or the number of fuel injections. is there. When fuel injection is terminated at the same time as during normal operation when the throttle valve is closed, fuel adheres to the intake manifold wall surface and the amount of fuel sucked into the combustion chamber decreases. When closed, fuel injection is started after the intake top dead center.

FIG. 2 is a schematic view of an in-line six-cylinder internal combustion engine (engine) provided with a fuel injection control device according to an embodiment of the present invention. An intake air temperature sensor 2 that detects an intake air temperature and outputs an intake air temperature signal is mounted downstream of an air cleaner (not shown). A throttle valve 4 is arranged downstream of the intake air temperature sensor. The throttle valve 4 interlocks with the throttle valve, turns on the throttle valve at an idle position (fully closed), outputs an idle signal, and turns off when the throttle valve opens. An idle switch 6 is attached. Slottle valve 4
A surge tank 8 is provided on the downstream side, and a pressure sensor 10 for detecting an intake pipe pressure downstream of the throttle valve and outputting an intake pipe pressure signal is attached to the surge tank 8. The surge tank 8 is connected to a combustion chamber 14 of the engine via an intake manifold 12. A fuel injection valve 16 is attached to the intake manifold 12 for each cylinder. The combustion chamber 14 of the engine is connected via an exhaust manifold to a catalytic converter (not shown) filled with a three-way catalyst. Further, a water temperature sensor 20 for detecting a cooling water temperature of the engine and outputting a water temperature signal is attached to the engine block. The tip of a spark plug 22 projects into the combustion chamber 14 of the engine,
Distributor 24 is connected to 22. The distributor 24 is provided with a cylinder discriminating sensor 26 and a crank angle sensor 28 each composed of a pickup fixed to a distributor housing and a signal rotor fixed to the distributor shaft. The cylinder discriminating sensor 26 outputs a cylinder discriminating signal to the control circuit 30 composed of a microcomputer or the like at each intake top dead center (720 ° C. A) of the first cylinder, for example.
28 outputs a crank angle signal to the control circuit 30 every 30 ° C., for example. And Distributor 24 is igniter 32
It is connected to the. Reference numeral 34 denotes an O ₂ sensor that detects the residual acidity in the exhaust gas and outputs an air-fuel ratio signal.

The control circuit 30 includes a central processing unit (CP) as shown in FIG.
U) 36, read-only memory (ROM) 38, random access memory (RAM) 40, back-up pram (BU-RAM) 42,
I / O port (I / O) 44, analog digital converter (A
DC) 46 and buses such as a data bus and a control bus for connecting them. I / O44 has
A cylinder discrimination signal, a crank angle signal, an air-fuel ratio signal, and an idle signal output from the idle switch 6 are input, and a fuel injection signal for controlling the opening and closing time of the fuel injection valve 16 via a drive circuit, and the igniter 32 is turned on and off. An ignition signal for controlling the time is output. The ADC 46 receives an intake pipe pressure signal, an intake temperature signal, and a water temperature signal and converts them into digital signals.

The above crank angle signal is output to the I / O44 via the waveform shaping circuit.
And a digital signal representing the engine speed is formed from the crank angle signal. The cylinder discrimination signal is input to the I / O 44 and converted into a digital signal in the same manner as described above. The cylinder discrimination signal is used together with the crank angle signal to form an interrupt request signal for calculating the basic fuel injection pulse width, a fuel injection start signal, a cylinder discrimination signal, and the like. An idle signal from the idle switch 6 is sent to a predetermined bit position of the I / O 44 and is temporarily stored. Also, I /
In O44, a well-known fuel injection control circuit including a presettable counter and a register is provided.
A fuel injection signal having the pulse width is formed from the binary data relating to the injection pulse width sent from 6, and the fuel injection signal is input to the fuel injection valve 16 to energize the injection valve. As a result, an amount of fuel corresponding to the pulse width of the fuel injection signal is injected in synchronization with the crank angle.

Further, the above-described in-line type six-cylinder engine has the first cylinder # 1
And the fifth cylinder # 5 as a first group, the third cylinder # 3 and the sixth cylinder # 6 as a second group, and the second cylinder # 2 and the fourth cylinder # 4 as a third group. Each time, fuel is injected in synchronization with the crank angle.

Next, a processing routine for controlling the above-described fuel injection control device will be described. FIG. 1 shows the main routine. First, at step 96, the cylinder pipe pressure PM and the engine speed NE are taken, and at step 98 the basic fuel injection pulse width is calculated and corrected by the engine coolant temperature and the like. The fuel injection pulse width τ [msec] is calculated. In the next step 100, it is determined whether or not the idle switch has been accelerated from the deceleration state by determining whether or not the idle switch has changed from on to off, and when the idle switch has changed from on to off, the fuel injection is performed in step 102. The constant α that determines the end time is α ₀ [msec] (for example, 1 to 50 msec). As the value α ₀ , the rise and vibration of the torque when the accelerator pedal is depressed are measured, and a value that is the smoothest and has a good acceleration response is selected. This value α ₀ is the time (msec) until the fuel injected from the fuel injection valve reaches the intake valve of the cylinder that first enters the intake stroke in each group (msec) and the time until the closed fuel injection valve is closed. It is a value greater than the value α ₁ at the time of steady operation, expressed as the sum of the time [msec].

In step 104, it is determined whether or not the idle switch is ON based on the idle signal. If the idle switch is ON, the fuel injection start crank angle θ ₁ stored in the ROM in advance is determined.
° C. For example, reading the value) in the 0 to 60 ° C. A ATDC at step 106, the fuel injection start crank angle theta ₁ is divided by 30 ° C. A is the generation interval of the crank angle signal at step 108, the integer part of the quotient Is the reference position θ. Then, in step 112, θ ₁
The fractional part of / 30 is defined as tθ. On the other hand, when the idle switch is off, the fuel injection start crank angle θ ₂ [° C. BTDC] during off-idle is calculated according to the following equation.

However, the constant alpha is idle Sui Tutsi from ON when changing off is adopted the value alpha ₀ of step 102, during normal operation the value alpha ₁ is employed, the steady operation from the time the idle Sui Tutsi changes from ON to OFF Α to shift
Value between ₀ and alpha ₁ and are employed. Also constants 1000, 60, 36
0 is for obtaining the advance of the crank angle per 1 [msec] from the engine speed NE.

At the following step 110, then converted into a value having a unit of the crank angle theta ₂ [° C. A ATDC] by subtracting the fuel injection start crank angle theta ₂ from the crank angle of the engine 2 rotates, in the same manner as described above in step 116 Starting fuel injection crank angle θ ₂
Is divided by 30 ° C. A and the integer part of the quotient is defined as the reference position θ, and the decimal part of the quotient is defined as tθ in step 118. In the next step 120, the decimal part tθ is converted into a time Tθ from the time between predetermined crank angles (for example, between 120 ° C and A).

FIG. 8 shows the relationship among the reference position θ, the time Tθ, the fuel injection pulse width τ, and the constant α obtained as described above.

In the next step 92, it is determined whether or not the decay timing of the constant α has been reached by determining whether a predetermined time has elapsed, whether the engine speed has increased by a predetermined speed, whether a predetermined crank angle has elapsed, or a predetermined number of injections has elapsed. In step 93, a predetermined value is subtracted from the constant α. At the following step 94, compares the value alpha ₁ during subtraction constants alpha and steady operation at step 93, the constant alpha is if the value alpha ₁ below, the value of the constant alpha and alpha ₁ at step 95 . As a result, the constant alpha is Surotsutoru valve from on next value alpha ₀ at the time of change off, the value alpha ₁ is gradually attenuated until the steady operation from this point.

Next, an interrupt request signal for each predetermined specific crank angle, that is, an interrupt request signal for every 30 ° C. and 720 ° C.
When an interrupt request signal for each A is input to the CPU 36, the CPU 36 executes the interrupt processing routine shown in FIGS.
Interrupt processing routine of FIG. 4 is for excisional the fuel injection end timing start timing fuel injection routine of FIG. 5 is for excisional the reference crank angle flag F _m.

Interrupt request signals for each 720 ° C. A is executed routine of FIG. 5 is input is the reference crank angle flag F _m at step 140 is returned to an excisional has been the main routine. Since the cylinder discrimination signal for each 720 ° C. is output at the intake top dead center of the first cylinder, the flag F _{m is set} at the intake top dead center of the first cylinder.
Will be set.

When an interrupt request signal for each 30 ° C. A is input is routine of FIG. 4 is executed, whether the reference crank angle flag F _m at step 122 is reset is determined, step is when it is reset 128 The count value CCRNK of the crank angle counter is incremented by 1. Meanwhile, when the flag F _m is excisional to zero the count value CCRNK while resetting the flag F _m at step 124 and step 126. In the next step 121, the reference position θ calculated in the main routine of FIG. 1 and stored in the RAM is read out, and in step 123 the count value CCRNK is read out.
By determining whether or not has matched the reference position θ,
It is determined whether or not the crank angle matches the fuel injection start reference position θ of the first group. If the count value CCRNK matches the reference position θ, the sum of the current time and the time Tθ (fuel injection start time) is set in the compare register A1 in step 125, and the current time, time Tθ, fuel and excisional sum of injection pulse width τ (the fuel injection end time) to the compare register B _1, and the process returns to the main routine.

On the other hand, if it is determined in step 123 that the count value CCRNK does not match the reference position θ, 8 is added to the reference position θ in step 129, and the value of the reference position θ is less than 24 in steps 130 and 131. After limiting to the value of
By determining whether or not the count value CCRNK matches the reference position θ restricted as described above, it is determined whether or not the crank angle matches the reference position θ for starting fuel injection of the second group. I do. If the count value CCRNK matches the reference position θ, the sum of the current time and the time Tθ (fuel injection opening time) is compared in step 133 with the compare register A2.
And the current time in step 134,
The sum of the time Tθ and the fuel injection pulse width τ (fuel injection end time) is set in the compare register B2, and the process returns to the main routine.

Conversely, if it is determined in step 132 that the count value CCRNK does not match the reference position θ, 8 is added to the reference position θ in step 135, and the value of the reference position θ is incremented by 24 in steps 136 and 137. After limiting to a value less than 138
It is determined whether the crank angle matches the reference position θ for starting fuel injection of the third group by determining whether the count value CCRNK matches the reference position θ restricted as described above. I do. If the count value CCRNK matches the reference position θ, the sum of the current time and the time Tθ (fuel injection start time) is compared in step 139 with the compare register A3.
And the current time in step 141,
The sum of the time Tθ and the fuel injection pulse width τ (fuel injection end time) is set in the compare register B3, and the process returns to the main routine.

FIG. 6 and FIG. 7 show that the current time is a compare register.
This shows a time matching interrupt routine that is interrupted when the time matches the time set in A1 and B1. If the current time matches the time set in compare register A1, the sixth
The interrupt routine shown in the figure is executed, and in step 142, binary data for opening the first group of fuel injection valves is sent from the CPU to the fuel injection control circuit, and the current time is set in the compare register B1. If the time coincides, the interrupt routine shown in FIG. 7 is executed, and in step 144, binary data for closing the first group of fuel injection valves is sent to the fuel injection control circuit. When the current time coincides with the time set in the compare registers A2 and A3, a time coincidence interrupt routine (not shown) similar to FIG. 6 is executed, and the fuel injection valves of the second group and the fuel of the third group are executed. Each injection valve is opened and the compare register
When the time coincides with the time set in B2 and B3, a time coincidence interrupt routine (not shown) similar to that shown in FIG. 7 is executed.
The group of fuel injectors and the third group of fuel injectors are each closed.

By performing the above control, as shown in FIG. 8, when the idle switch is off, the fuel injection is terminated before the top dead center of the first, third, and second cylinders, and when the idle switch is on. Starts fuel injection after the above top dead center.

FIG. 9 shows a change in the fuel injection end timing when the value of the constant α changes from α ₀ to α ₁ . FIG. 9 shows only the change for the first group, but the same applies to other groups.

Although an example in which fuel is injected for each group of cylinders has been described above, the present invention is not limited to this, and can be applied to an independent injection engine that injects fuel for each cylinder. Also, the present invention can be applied to an engine that calculates a basic fuel pulse width from an engine speed and an intake air amount per one engine rotation. Further, the acceleration may be detected from the rate of change of the intake valve pressure and the rate of change of the intake air amount. Further, in the above, an example has been described in which the time from the start of fuel injection to the end of fuel injection is controlled by time, but this time may be converted into a crank angle and controlled based on the count value CCRNK.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a main routine of one embodiment of the present invention, FIG. 2 is a schematic diagram of an engine provided with a fuel injection device according to one embodiment of the present invention, and FIG. 3 is a control circuit of FIG. FIG. 4 is a flowchart showing a 30 ° C. interrupt routine of the above embodiment, FIG. 5 is a flowchart showing a 720 ° C. interrupt routine of the above embodiment, and FIGS. 6 and 7 are time coincidence interrupt routines. FIG. 8 is a diagram showing fuel injection timing and the like, and FIG. 9 is a diagram showing a change in fuel injection end timing at the time of acceleration. 6 ... Idle switch, 16 ... Fuel injection valve, 28 ... Crank angle sensor.

Claims (1)

(57) [Claims] 1. A fuel injection control apparatus for an internal combustion engine for calculating a fuel injection amount at a predetermined cycle, comprising: acceleration detection means for detecting acceleration of the engine; and crank angle detection means for detecting a crank angle and outputting a crank angle signal. And controlling the fuel injection valve based on the crank angle signal so that fuel injection ends at a predetermined timing before the intake top dead center during steady operation, and furthermore, when acceleration of the engine is detected, Control means for controlling the fuel injection valve so that the fuel injection ends before the fuel injection control device for the internal combustion engine.