JPS5859322A - Electronically controlled fuel injection engine - Google Patents

Abstract

PURPOSE:To improve the accuracy in controlling the air fuel ratio, by switching the fuel injection to one fuel injection per cycle of the engine under the specified operating state of the engine, and alleviating the restriction of the minimum fuel injection quantity. CONSTITUTION:Two fuel injections are oerformed for one cycle of the engine in synchronization with the rotation of the engine. In step 58, the engine speed of 1,000rpm or more is judged. In a step 59, the fuel is cut OFF. When the engine speed of 900rpm or less is judged in a step 60, a program is finished, and the fuel cut is finished. When the engine speed is 900rpm or more, the step is advanced to a step 61, the contents of a counter, which counts the number of rotation of a crank shaft are judged. In this way, since one fuel injection per cycle of the engine is performed when the engine speed is decreased and the fuel cut is finished, the accuracy in controlling the air fuel ratio can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronically controlled fuel injection engine that injects fuel from a fuel injection valve to an intake system in synchronization with engine rotation (crank angle).

In an electronically controlled fuel injection engine, a required fuel injection amount is calculated from the intake air flow 1, engine rotational speed, etc., and an electric pulse having a pulse width corresponding to the required fuel injection amount is sent to the fuel injection valve. A fuel injection valve has a minimum fuel injection amount as a lower limit at which fuel can be injected in one fuel injection, and in a conventional electronically controlled fuel injection engine, it is injected twice per engine d1 cycle regardless of the engine operating state. Because fuel injection is performed, it is difficult to significantly reduce the amount of fuel injected.
Air-fuel ratio control accuracy had deteriorated.

The purpose of this protest is to relax the restrictions on the minimum fuel injection amount.
An object of the present invention is to provide an electronically controlled engine that can improve the control accuracy of air-fuel ratio.

In order to achieve this object, according to the electronically controlled fuel injection engine of the present invention, fuel injection is performed twice per engine cycle under normal conditions, and a significant reduction in fuel injection IIt is required. In the operating range of the engine, the fuel injection is switched to once per engine cycle.

The present invention will be described in detail with reference to the drawings.

Figure 1 is an overall schematic diagram of an electronically controlled fuel injection engine.
The air sucked into the intake passageway 2 through the air cleaner 1 has its flow rate controlled by a throttle valve 3 that is linked to an accelerator pedal in the driver's cab, and is guided to the combustion chamber of the engine body 5 via an intake branch pipe 4. .

The exhaust system is provided with, in order from upstream, an exhaust branch pipe 6, an exhaust pipe 7, and a catalytic converter 8 that accommodates a three-way catalyst. The current supplied to the spark plug in the combustion chamber is controlled by the ignition coil 9 and the power distributor IO. Air flow meter 1
3 detects the intake air flow I+1, the intake temperature sensor 14 detects the intake air temperature, the water temperature sensor 15 is attached to the cylinder block and detects the cooling water temperature, and the air-fuel ratio sensor 16
is attached to the exhaust branch pipe 6 to detect the oxygen concentration in the exhaust gas, and the throttle sensor 17 detects the opening degree of the throttle valve 3. Primary current signal of ignition coil 9, air flow meter 1
3. The outputs of the intake air temperature sensor 14, water temperature sensor 16, air-fuel ratio sensor 16, and throttle sensor 17 are sent to the electronic control unit 20. The fuel injection valves 21 are provided at each core portion of the intake branch pipe 4 and are opened and closed in response to electric pulses from the electronic control device 20.

FIG. 2 is a block diagram of the electronic control device 2o, and FIG. 3 is a waveform diagram of each block in FIG.

The next-ignition signal AI from the ignition coil 9 is sent to a divider circuit 29 which generates one pulse for every 20 degree change in the rank angle. In the exemplary embodiment, the internal combustion engine is a four-cylinder engine, and one pulse is generated as the output of the frequency divider circuit 29 for every four post-ignition pulses, that is, for every 1/2 cycle of the engine. The basic injection pulse generation circuit 30 includes a first capacitor 31, and the first capacitor 31 generates a predetermined current A for a time TI equal to the pulse width of the output pulse of the frequency dividing circuit 29, that is, from time 11 to t2.
The first capacitor 31 is charged at time t2 and discharged at a discharge current related to the output voltage of the air flow meter 2 at time t2, and at time t3 after time T2 has elapsed from time t2.
The voltage across 0 becomes zero. The discharge current of the first capacitor 31 is smaller as the intake air flow taQ is larger, and the discharge current of the first capacitor 31 is smaller as the intake air flow taQ is larger.
is inversely proportional to the engine speed N, so the time T2 is Q/N
is proportional to. The basic injection pulse generation circuit generates a pulse with a pulse width T2 as an output, and this output is sent to a multiplier circuit 33 via a diode 32. Multiplier circuit 3
3 includes a second capacitor 34, and the second capacitor 3
4 is charged for time T2 and is also discharged for time t3.

The charging current of the second capacitor 34 changes depending on the feedback signal of the air-fuel ratio sensor 16, and the discharging current changes depending on the output of the water temperature sensor 15. At time t4, when time T3 has elapsed from time t3, the voltage across the second capacitor 34 becomes zero, but time T3 is the time T2 corrected based on the operating state of the engine.

A pulse with a pulse width T4 is generated from time t4 to time t5, and the multiplier circuit 23 outputs a pulse with a pulse width T5 equal to time T2+T3+74. The time T4 is equal to the invalid injection time of the fuel injection valve 9. Multiplying circuit 33-5
The output is sent via OR circuit 35 to power amplifier 360 base. The four fuel injection valves 21 are connected in parallel to each other, and are connected at one end to a power amplifier 36 and at the other end via a resistor 37 to a storage battery 38 as a DC power source. The accumulator 38 is also connected to the input of the multiplier circuit 33 via a resistor 49. Digital correction circuit 53
In the CPU (central processing unit) 39, timer 40,
Interrupt control unit 41. Input interface 42, output interface 43. RAM (arbitrary access storage device) 44
, ROM (read-only memory) 45, A/1) (analog/digital) converter 46, and D/A (digital/analog) converter 47 are connected to each other via a bus 48. The section 41 receives the output of the basic injection pulse generation circuit 30, and the input interface 42 receives the output from the air-fuel ratio sensor f16 and the throttle position sensor 17.
The A/P converter signal receives the analog outputs of the air flow meter 13 and the water temperature sensor 15. The storage battery 38 is connected to the main power circuit 51 and to the auxiliary power circuit 52 via a key switch 5o in the driver's cab serving as an ignition switch. The RAM 44 is supplied with power from the auxiliary power supply circuit 52 and can retain memory even while the key switch 5o is open. Each output terminal of the output interface 43 is connected to an input terminal of the multiplication circuit 33 and an input terminal of the OR circuit 35.

The signal from the output interface 43 to the multiplication circuit 33 is 0.
In this case, the output pulse of the basic injection pulse generation circuit 3o is prevented from being sent to the multiplication circuit 33, and as a result, the fuel injection valve 21 is not driven and fuel cut is performed. Further, when a pulse is sent from the output interface 43 to the OR circuit 35, the power amplifier 36 becomes conductive,
Asynchronous injection is performed that is not synchronized with the crank angle.

Under normal conditions, an amount of fuel greater than the minimum fuel injection amount for one injection from the fuel injection valve 21 is required, so all output pulses of the basic injection pulse generation circuit 30 are sent to the multiplication circuit 33, as shown in FIG. As shown in , for each cycle of the engine (4 in the example), since it is a cylinder internal combustion engine, the ignition -
Two fuel injection pulses (output All of multiplier circuit 33) are formed for every eight ignition pulses as subsequent signal A1. On the other hand, in a predetermined operating range of the engine in which the amount of fuel to be injected is significantly reduced by one, the input terminal of the multiplier circuit 33 is maintained at 0 by the signal from the output interface 43 during the period of the engine's η cycle; One of the two output pulses of the injection pulse generation circuit 30 is blocked from being input to the multiplication circuit 33, and fuel injection is performed once per engine cycle.

FIG. 4 is a flowchart of an example program when the present invention is applied to a fuel cut method.

In step 57, it is determined from the input from the throttle sensor 17 whether or not the throttle valve 3 is at the idling opening. If the determination result is positive, the process proceeds to step 58, and if not, the program is terminated.

In step 58, the engine rotation speed is 100 o r, p,
It is determined whether or not it is greater than or equal to m, and if the determination result is positive, the process proceeds to step 59, and if not, the process proceeds to step 60. In step 59, a fuel cut is performed. The fuel cut is performed by setting the input terminal of the multiplication circuit 33 to 0 using the output interface 43.

Therefore, the engine rotation speed is 100 Or, p, m,
During the above deceleration period, fuel cut is performed. In step 60, it is determined whether the engine rotational speed is 90 Or, p, m, or less. If the determination result is positive, this program is terminated, and if not, the program proceeds to Stella:j61. Therefore, if the engine rotational speed is 90 Or, p, m, or less, the fuel cut is terminated. In step 6, it is determined whether the content of the counter is 1 or not, and if the determination result is positive, this program is terminated, and if not, step 5
Proceed to 9. This counter is a 1-bit counter that counts the number of revolutions of the crankshaft, and during one of the two revolutions of the crankshaft, the content of the 1-bit counter is 0, and during the period of the other revolution, the content of the 1-bit counter is 0. The content of is l. Therefore, the engine rotation speed is 90Or, p
, m, thicker (1000 r, p, m), if the fuel is injected once per two revolutions of the crankshaft, or in other words, per 1 cycle of the engine.In this way, the engine speed decreases and the fuel When finishing the cut,
Instead of the usual two fuel injections per engine cycle, there is now one fuel injection per engine cycle, and then two fuel injections per engine cycle. , the change in engine torque due to the end of the fuel cut becomes more gradual, and the impact is suppressed.

FIG. 5 is an explanatory diagram of the fuel injection amount when the throttle valve 3 is opened from the idling opening and the engine is accelerated. ◎When the throttle valve 3 is opened from the idling opening, that is, the output of the throttle sensor 17 is Time t when changing from on to off
At 1, the intake air flow rate detected by the air flow meter 13 immediately increases. Afrometer 1
The intake air that has passed through the airflow meter 13 takes a predetermined time to be sucked into the combustion chamber due to the volume of the intake system downstream from the airflow meter 13. The amount of petroleum fuel ejected immediately increases as shown by the broken line in FIG. 5, and with the conventional fuel injection method, the amount of harmful unburned components in the exhaust gas increases. However, in the present invention, fuel injection is performed once per cycle of the engine until acceleration start time t1 or time t2 when a predetermined time has elapsed, so the fuel injection height becomes excessive as shown by the solid line in Figure 5. However, the actual demand (Il) will vary along the line.

As described above, according to the present invention, in an operating state of the engine that requires a reduction in fuel injection by 110 degrees, fuel injection is switched from two fuel injections per engine cycle to l (+il fuel fuel) injection. By relaxing the restriction on the minimum fuel injection amount of the fuel injection valve, it is possible to improve the air-fuel ratio control by ?+'i degrees.

[Brief explanation of drawings]

Fig. 1 is an overall schematic diagram of an electronically controlled fuel injection engine as an embodiment of the present invention, Fig. 2 is a block diagram of the electronic control device shown in Fig. 1, and Fig. 3 is an explanation of the operation of the block diagram shown in Fig. 2. FIG. 4 is a flowchart of a program in which the present invention is applied to fuel cut during deceleration, and FIG. 5 is an explanatory diagram when the present invention is applied to fuel injection at the start of acceleration. 9... Ignition coil, 20... Electronic control device, 21.
...Fuel injection valve patent applicant Toyota Motor Corporation! Be°- Figure 1 Figure 5 Ono tl ℃2 hours

Claims (1)

[Claims] 1. In an electronically controlled fuel injection engine that performs fuel injection twice per engine cycle in synchronization with engine rotation, fuel injection is performed once per engine cycle under a predetermined operating state of the engine. An electronically controlled fuel injection engine characterized by being switched to 2. A patent characterized in that the predetermined operating state of the engine is a period during which the engine is decelerating and the engine rotational speed is between a predetermined value of kuru l and a second predetermined value that is larger than the first predetermined value. An electronically controlled fuel injection engine according to claim 1. 3. Electronic control according to claim 1, characterized in that the predetermined operating range of the engine is during acceleration within a predetermined time from the time when the intake system throttle valve is opened from idle and ring opening. fuel injection engine.