JPH0447131B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electronically controlled fuel injection system that improves the responsiveness of an engine during acceleration.

[Conventional technology]

In conventional electronically controlled injection systems that calculate the basic fuel injection amount in relation to the engine's intake pipe pressure P or intake air flow rate Q, a linear throttle sensor that generates an output voltage that is a linear function of the throttle opening θth is used. The air-fuel ratio during the acceleration period is corrected in relation to the output of the throttle sensor and the intake pipe pressure P or intake air flow rate Q. However, in the case of acceleration from a light load range, the intake pipe pressure P or the intake air flow rate Q increases significantly in response to a slight increase in the throttle opening θth, so the air-fuel ratio during the acceleration period must be adjusted appropriately depending on the acceleration state. It is difficult to control, and the structure of a linear throttle sensor is more complicated than that of a contact type throttle sensor, resulting in increased cost.

Therefore, the patent application filed on the same day as this invention
-149203 measures the difference value of intake pipe pressure or intake air amount twice, determines whether the measured value is larger than a positive predetermined value, and when it is determined that the measured value is larger than the positive predetermined value. We are proposing a method that performs asynchronous injection.

In this application, the asynchronous injection condition is determined by comparing the second derivative value of the intake pipe pressure or intake air amount with a predetermined positive threshold value. It is intended to perform accurate asynchronous injection by quickly detecting the starting point.

[Problem to be solved by the invention]

The sampling period of the intake pipe pressure or intake air amount for calculating the two-time difference value needs to be long to some extent in order to avoid false detection of acceleration due to the influence of noise during steady state. but,
If the sampling period is set over the entire period of acceleration to a value determined from noise countermeasures during steady state as described above, the sampling period will become too long considering the case where a certain amount of time has passed since the start of acceleration.
Asynchronous injection tends to be delayed and acceleration performance deteriorates.

The purpose of this invention is to improve responsiveness without causing false detection due to noise in the initial stage of acceleration.

[Means to solve the problem]

In order to achieve the above object, according to the present invention,
In Fig. 5, in an electronically controlled fuel injection system that injects fuel from a fuel injection valve into the intake system of an internal combustion engine during acceleration operation asynchronously with the normal fuel injection timing that is performed in synchronization with the stroke of the internal combustion engine, load detection means for detecting the intake pipe pressure or intake air amount; time interval signal generating means for generating a predetermined time interval signal shorter than the duration of the acceleration operation; Difference value calculation means for calculating a difference value corresponding to the differential amount; Asynchronous injection condition determination means for determining an asynchronous injection condition for performing asynchronous injection by comparing the difference value calculated by the difference value calculation means with a positive predetermined threshold; an asynchronous injection means for causing an asynchronous injection from a fuel injection valve when it is determined that the injection condition is met; and a time interval setting means for setting a time interval of a time interval signal generated by the time interval signal generating means;
The time interval set by the time interval setting means is equal to the first predetermined value until the asynchronous injection condition is satisfied for the first time in one acceleration, and is equal to the first predetermined value after the asynchronous injection condition is satisfied. An electronically controlled fuel injector is provided that is equal to a shorter second predetermined value.

[Effect]

The load detection means a detects the intake pipe pressure or intake air amount of the internal combustion engine.

The time interval signal generating means b generates a predetermined time interval signal shorter than the duration of the acceleration operation.

The difference value calculation means c calculates a difference value corresponding to the twice differential amount of the intake pipe pressure or intake air amount for each time interval.

The asynchronous condition determining means d determines an asynchronous injection condition for performing asynchronous injection by comparing the difference value calculated by the difference value calculating means c with a predetermined positive threshold value.

The asynchronous injection means e causes the fuel injection valve 13 to perform asynchronous injection when it is determined that an asynchronous injection condition exists.

The time interval setting means f sets the time interval of the time interval signal generated by the time interval signal generating means, and the time interval set here is such that in one acceleration,
It is equal to the first predetermined value until the asynchronous injection condition is satisfied for the first time, and is equal to the second predetermined value shorter than the first predetermined value after the asynchronous injection condition is satisfied.

〔Example〕

The present invention will be explained below with reference to the drawings.

In FIG. 1, an air cleaner 2, a throttle valve 3, a surge tank 4, and an intake pipe 5 are provided in an intake passage 1 in this order from upstream. The bypass passage 9 is connected to the upstream side of the throttle valve 3 and the surge tank 4.
The flow cross section is controlled by a control valve 10 controlled by a pulse motor. Idle switch 1
1 is on when the throttle valve 3 is at an idling opening, and is off when the throttle valve 3 is opened more than the idling opening. The pressure sensor 12 detects the intake pipe pressure P derived from the surge tank 4. The fuel injection valve 13 is provided near the intake port and injects fuel into the intake system in response to a fuel injection pulse signal. A combustion chamber 17 of the engine 16 is defined by a cylinder head 18, a cylinder block 19, and a piston 20;
A spark plug 21 is provided. The air-fuel mixture is led to the combustion chamber 17 through the intake valve 22, and the exhaust gas is led to the combustion chamber 17 through the exhaust valve 2.
3 and is discharged from the combustion chamber 17 to the exhaust pipe 27. An oxygen sensor 28 as an air-fuel ratio sensor is attached to the exhaust pipe 27 and detects the oxygen concentration in the exhaust pipe. A water temperature sensor 29 is attached to the cylinder block 19 to detect the cooling water temperature. The cylinder discrimination sensor 32 and the rotation angle sensor 33 detect the crank angle from the rotation of the rotating shaft 35 of the power distributor 34, and detect the crank angle by 1 every time the crank angle changes by 720° and 30°, respectively.
generates pulses. The electronic control device 38 receives input signals from each sensor and sends output signals to the electromagnetic valve 10, the fuel injection valve 13, and the ignition device 39.
The secondary ignition current of the ignition device 39 is sent to the spark plug 21 of each combustion chamber 17 via the power distributor 34 .

FIG. 2 is a block diagram of the inside of the electronic control unit 38. CPU44, A/D (analog/digital converter) 45, I/O (input/output interface)・
RAM 46, ROM/I/O 47, and backup RAM 48 are connected to each other by bus 49. The backup RAM 48 is connected to the power supply and retains its memory even when the engine switch is off. Analog signals from pressure sensor 12 and water temperature sensor 29 are sent to A/D 45. The outputs of the idle switch 11, cylinder discrimination sensor 32, and rotation angle sensor 33 are sent to the I/O section of the I/O/RAM 46. The output of the oxygen sensor 28 is sent to the comparator 50.
The data is then sent to the I/O section of the I/O RAM 46. The fuel injection valve 13 receives a fuel injection pulse from the CPU 44. The ignition device 32 receives control signals from the I/O section of the I/O RAM 46 . The control valve 10 for controlling the step motor is the I/O of the ROM/I/O 47.
receives control pulses from the

FIG. 3 is a flow chart of the asynchronous injection program of the present invention. Note that synchronous injection is performed in synchronization with the crank angle, and since this is well known, the explanation will be omitted. The intake pipe pressure P as the detected value of the pressure sensor 12 is A/D converted every 10 msec.
This program is executed as an interrupt routine upon completion of A/D conversion. In step 58, the current intake pipe pressure P(k) and the previous time, that is, 20 msec
Difference from previous intake pipe pressure P( ^k -2) P( ^k ) - P( ^k -
2) and assign the difference to ΔP( ^k ).
ΔP as the amount of change in P per 20 msec is the time t
It is equivalent to the differential of P with respect to dP/dt. In step 59, it is determined whether the flag F is 1 or 0. If F=0, the process proceeds to step 61, and if F=1, the process proceeds to step 71. The flag F is reset when the idle switch 11 changes from off to on, and is set in step 66, which will be described later. Therefore, if the first asynchronous acceleration fuel injection has not yet been performed, F=0, and the process proceeds to step 61. In step 61, the current ΔP( ^k ) and the previous time, i.e.
The difference from ΔP( ^k −2) 20 msec ago is ΔP( ^k )−ΔP( ^k −
Substitute 2) for ΔΔPa. In step 62, ΔΔPa
> predetermined value A, and only if ΔΔPa>A, proceed to the subsequent steps. In step 63, it is determined whether the idle switch 11 is on or off, and only if it is off, the process proceeds to the subsequent steps. Therefore, performing asynchronous acceleration fuel injection during the deceleration period is avoided. In step 64, it is determined whether ΔP( ^k )<0, and only if ΔP( ^k ) is 0, the subsequent steps are executed. Therefore, asynchronous acceleration fuel injection during the period when P is decreasing is avoided. In step 65, asynchronous acceleration fuel injection that is not synchronized with the crank angle is performed once. The fuel injection time in this asynchronous accelerated fuel injection is selected to be a constant value, for example, 2 msec. Also, A in step 62 is B in step 72.
Since the smaller value is selected, step 65 is executed immediately after acceleration. At step 66, flag F is set to 1. Therefore, from the next execution of the program, F=1 at step 59.
A determination is made. In step 71, the current ΔP
The difference ΔP( ^k )−ΔP( ^k −1) between ( ^k ) and the previous time, that is, ΔP( ^k −1) 10 msec ago, is substituted for ΔΔPb. In step 72, it is determined whether ΔΔPb>B or B, and the subsequent steps are executed only if ΔΔPb>B. However, B<A. In step 73, it is determined whether the idle switch 11 is on or off, and in step 74, it is determined whether ΔP( ^k )<0 or 0, and only when the idle switch 11 is off and ΔP( ^k ) is 0. Proceed to the next step. In step 75, asynchronous acceleration fuel injection is performed. The fuel injection time τau in this asynchronous accelerated fuel injection is expressed by the following equation.

τau=1+40×ΔΔPb/1000 In this formula, ΔΔPb is 2 stored in RAM.
It is decimal data, and the LSB (least significant bit) of ΔΔPb
1 corresponds to 1.22mmHg. Therefore, when ΔΔPb is 50 mmHg, τau is approximately 2.6 msec. During the acceleration period in which ΔΔPbB is maintained, step 75 is executed every 10 msec to perform asynchronous accelerated fuel injection. Figure 4 shows the throttle opening θth during the acceleration period, the actual intake pipe pressure Pr, the intake pipe pressure P detected by the pressure sensor 12,
Change amount ΔP of P per 20msec, 20msec and
It shows the amount of change ΔΔPa and ΔΔPb in ΔP per 10 msec and the time change in the driving voltage of the fuel injection valve 13. During the period when the drive voltage is at a low level, the fuel injection valve 13 is maintained in an open state and injects fuel. When acceleration starts at time t1, the throttle opening θth increases from 0°. Along with this, the actual intake pipe pressure Pr increases, and the intake pipe pressure P as a detected value of the pressure sensor 12 also increases. An overshoot has occurred in P. Fuel injection Ia is performed when the idle switch 11 changes from on to off. Ib is a synchronous fuel injection performed in synchronization with the crank angle, and corresponds to an amount obtained by correcting the basic fuel injection amount as a function of the intake pipe pressure P and therefore the engine load by the cooling water temperature. I C
is an asynchronous accelerated fuel injection performed in conjunction with the execution of step 67, and is performed when ΔΔPa exceeds a predetermined value A after time t1. Id is an asynchronous accelerated fuel injection that is performed in conjunction with the execution of step 71, and is performed at a cycle of 10 msec during the period when ΔΔPb>B is maintained after the execution of Ic. Since ΔΔPa and ΔΔPb increase more than ΔP at the start of acceleration, it is possible to promptly and accurately detect the start of acceleration and perform asynchronous accelerated fuel injection. In particular, ΔΔPa increases significantly with the start of acceleration, so
The first asynchronous acceleration fuel injection is accelerated by executing step 66. Furthermore, since the increase in ΔΔPb closely reflects the increase in the slot opening degree θth, asynchronous acceleration fuel injection Id can be performed depending on the state of acceleration.

Although the embodiment shows an electronically controlled engine that calculates the basic fuel injection amount based on the intake pipe pressure P, the present invention can also be applied to an electronically controlled engine that calculates the basic fuel injection amount based on the intake air flow rate Q. Needless to say. In this case, P, ΔP, ΔΔPa,
ΔΔPb is replaced by Q, ΔQ, ΔΔQa, and ΔΔQb, respectively.

In the embodiment, the function of the time interval signal setting means of the present invention is achieved by causing the A/D converter 45 to execute the processes from step 58 at regular time intervals.

In the embodiment, the function of the difference value calculation means of the present invention is achieved by the processing in step 61 or 71 of calculating the difference value ΔΔPa corresponding to the twice differential value at a constant time interval.

In the embodiment, the function of the asynchronous condition determining means of the present invention is as follows:
Achieved by judgments 62 and 72.

In the embodiment, the function of the time interval setting means of the present invention is cleared when the idle switch is turned on (when the accelerator pedal is returned to the idle position), and is set (when the asynchronous condition is satisfied). Step 66) Using flag F, calculate the difference value ΔΔPa at step 61 while F=0 at twice the execution interval (20 milliseconds) of the routine in FIG. 3, and when F=1 is realized by calculating the difference value ΔΔPa in step 71 at an execution interval (10 milliseconds) that is equal to the execution interval of the routine shown in FIG.

〔Effect of the invention〕

According to this invention, the sampling interval for calculating the second derivative value of the intake pipe pressure or the intake air amount is set to the first predetermined value during one acceleration until the asynchronous injection condition is satisfied for the first time. equally,
After the asynchronous condition is satisfied, by setting the value equal to the second predetermined value, which is shorter than the first predetermined value, the start condition for asynchronous injection can be accurately detected without the risk of falsely detecting noise during steady state, and the asynchronous injection After the injection conditions are met, asynchronous injection can be performed quickly by shortening the sampling period, harmoniously achieving the conflicting demands of accurate and reliable detection of acceleration and improved responsiveness. There is an effect that can be done.

[Brief explanation of the drawing]

Fig. 1 is an overall schematic diagram of an electronically controlled engine to which the present invention is applied, Fig. 2 is a block diagram of the electronic control device, Fig. 3 is a flowchart of the program of the present invention, and Fig. 4 is a fuel for the acceleration engine. FIG. 5 is a graph showing changes over time in the drive voltage of the injection valve, etc., and FIG. 5 is a functional block diagram showing the configuration of the present invention. 1...Intake passage, 12...Pressure sensor, 13...
...Fuel injection valve, 38...Electronic control device.

Claims (1)

[Scope of Claims] 1. In an electronically controlled fuel injection device that injects fuel from a fuel injection valve into an intake system of an internal combustion engine during acceleration operation asynchronously with the normal fuel injection timing that is performed in synchronization with the stroke of the internal combustion engine, load detection means for detecting intake pipe pressure or intake air amount of an internal combustion engine; time interval signal generating means for generating a signal at predetermined time intervals shorter than the duration of acceleration operation; and intake pipe pressure or intake air amount at each of said time intervals. Difference value calculation means for calculating a difference value corresponding to the two-time differential amount of Asynchronous injection condition determination means for determining an asynchronous injection condition for performing asynchronous injection by comparing the difference value calculated by the difference value calculation means with a positive predetermined threshold value , comprising an asynchronous injection means for causing the fuel injection valve to perform an asynchronous injection when an asynchronous injection condition is determined, and a time interval setting means for setting a time interval of a time interval signal generated by the time interval signal generating means,
The time interval set by the time interval setting means is equal to the first predetermined value until the asynchronous injection condition is satisfied for the first time in one acceleration, and is equal to the first predetermined value after the asynchronous injection condition is satisfied. An electronically controlled fuel injector equal to a shorter second predetermined value.