JPS62344B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel cut method for an electronically controlled fuel injection engine that controls the amount of fuel supplied to an intake system by operating an injection valve using an electric signal.

In order to improve the efficiency of fuel consumption during deceleration and to reduce the amount of harmful unburned components in the exhaust gas, fuel cuts are well known in which the supply of fuel is interrupted during deceleration.
In the conventional fuel cut method, regardless of the deceleration of the vehicle, when the engine speed drops to a predetermined value or less due to deceleration, fuel cut is terminated and fuel supply is resumed. It has been difficult to set the engine rotational speed at the end of fuel cut to a sufficiently low value in order to appropriately suppress shocks caused by fluctuations in torque generated by the engine. The engine speed at the end of fuel cut is determined by the output of the clutch switch that detects the vehicle speed and the clutch connection state, the switch that detects the neutral position of the transmission, and the output of the switch that detects the operating state of the brake pedal. Although a fuel cut method has been proposed in which the fuel cut is changed to a value, it is insufficient in terms of shock protection when the fuel cut ends.

An object of the present invention is to further improve fuel consumption efficiency and reduce the amount of unburned components in exhaust gas by setting the engine rotational speed at the end of fuel cut to a sufficiently small value while avoiding the shock at the end of fuel cut. It is an object of the present invention to provide a fuel cut method for an electronically controlled fuel injection engine that can further reduce the amount of fuel cut.

In order to achieve this object, the present invention focuses on the fact that during a period when the vehicle deceleration is large, the driver, etc. feels less shock due to the shock at the end of fuel cut, and the deceleration is larger than a predetermined value. The engine rotational speed at the end of the fuel cut in this case is made smaller than the engine rotational speed at the end of the fuel cut in the case where the deceleration is smaller than a predetermined value.

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is an overall schematic diagram of an electronically controlled fuel injection engine. The intake system is provided with an air cleaner 1, an air flow meter 2, a throttle valve 3, a surge tank 4, and an intake pipe 5 in this order from upstream. The bypass passage 6 is connected to the upstream side of the throttle valve 3 and the surge tank 4.
The flow cross section is controlled by a bimetallic control valve 7. During warm-up, the bypass passage 6 is opened to increase the intake air flow rate.
The fuel injection valve 9 is attached to the intake pipe 5 near the intake port, and is operated by an electric pulse signal to inject fuel. The combustion chamber 10 of the engine body 17 is divided by a cylinder head 11, a cylinder block 12, and a piston 13, and the air-fuel mixture is passed through an intake valve 14.
The fuel is drawn into the combustion chamber 10 through the combustion chamber 10, and after combustion is discharged into the exhaust pipe 16 through the exhaust valve 15. A throttle position sensor 18 detects the idling opening of the throttle valve 3, and a water temperature sensor 19 is attached to the cylinder block 12 to detect the temperature of the cooling water.
The acceleration/deceleration sensor 20 is composed of a potentiometer, and is connected to the slider 2 in relation to the acceleration/deceleration applied to the vehicle body.
1 swings and generates a voltage related to the acceleration/deceleration of the vehicle. The air-fuel ratio sensor 22 is attached to the exhaust pipe 16 and detects the oxygen concentration in the exhaust gas. Air flow meter 2, throttle position sensor 1
8. The outputs of the water temperature sensor 19, acceleration/deceleration sensor 20, and air-fuel ratio sensor 22, as well as the ignition signal from the ignition coil 23, are sent to the electronic control device 24, and the output of the electronic control device 24 is sent to the fuel injection valve 9. .

FIG. 2 is a block diagram of the electronic control unit 24, and FIG. 3 is a waveform diagram of each block in FIG. The ignition primary signal A1 from the ignition coil 23 is sent to a frequency divider circuit 29, which generates one pulse for every 720 degree change in crank angle. In the embodiment, the internal combustion engine is a four-cylinder engine, and one pulse is sent to the frequency dividing circuit 2 for every four primary ignition pulses.
9 output. The basic injection pulse generation circuit 30 includes a first capacitor 31, and the first capacitor 31 is charged for a time T1 equal to the pulse width of the output pulse of the frequency dividing circuit 29, that is, at a time t1.
is charged with a predetermined current A4 from t2 to t2, and at time t2
The first capacitor 31 is discharged with a discharge current related to the output voltage of the air flow meter 2, and the voltage across the first capacitor 31 becomes zero at time t3 after time T2 has elapsed from time t2. The discharge current of the first capacitor 31 becomes smaller as the intake air flow rate Q increases, and since the time T1 is inversely proportional to the engine rotational speed N, the time T2 is proportional to Q/N. The basic injection pulse generating circuit 30 generates a pulse having a pulse width T2 as an output, and this output is sent to a multiplier circuit 33 via a diode 32. The multiplier circuit 33 includes a second capacitor 34, and the second capacitor 34 is connected to the time T2.
is charged and discharged from time t3. The charging current of the second capacitor 34 changes depending on the feedback signal of the air-fuel ratio sensor 22, and the discharging current changes depending on the output of the water temperature sensor 19. From time t3 to time T
The voltage across the second capacitor 34 becomes zero at time t4 when 3 has elapsed;
2 is corrected according to the engine operating condition.
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+T4. The time T4 is equal to the invalid injection time of the fuel injection valve 9. The output of the multiplier circuit 33 is sent to the base of a power amplifier 36 via an OR circuit 35. The four fuel injection valves 9 are connected in parallel to each other, with one end connected to a power amplifier 36 and the other end connected 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. In the digital correction circuit 53, a CPU (central processing unit) 39,
Timer 40, interrupt control unit 41, input interface 42, output interface 43, RAM (random access storage) 44, ROM (read-only storage) 45, A/D (analog/digital)
Converter 46 and D/A (digital/analog) converter 47 are connected to each other via bus 48. The interrupt calculation section 41 receives the output of the basic injection pulse generation circuit 30 and inputs the output from the input interface 4.
2 receives the digital outputs of the throttle position sensor 18 and the air-fuel ratio sensor 22, and the A/D converter 46 receives the digital outputs of the throttle position sensor 18 and the air-fuel ratio sensor 22.
Receives analog output of 9. The storage battery 38 is connected to a main power supply circuit 51 and to an auxiliary power supply circuit 52 via a key switch 50 in the driver's cab 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 50 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. From the output interface 43 to the multiplication circuit 33
When the signal to is 0, the output pulse of the basic injection pulse generation circuit 30 is prevented from being sent to the multiplication circuit 33, and as a result, the fuel injection valve 9 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, and asynchronous injection not synchronized with the crank angle is performed. The output of the fuel cut circuit 53 is sent to the frequency dividing circuit 29.

FIG. 4 shows details of the fuel cut circuit 53. The primary ignition signal of the ignition coil 23 is sent to an F/V (frequency/voltage) converter 56, and a voltage proportional to the engine rotation speed N is generated at the output end of the F/V converter 56. The output of the F/V converter 56 is connected to the resistor 57.
is sent to the anti-phase input terminal of operational amplifier 58 via . The output of the acceleration/deceleration sensor 20 is sent to the comparator 59 and compared with the reference voltage B1 of the terminal 60, and the output of the comparator 59 becomes 1 when the deceleration of the vehicle is equal to or higher than the predetermined value D, indicating that the vehicle Deceleration is a predetermined value D
If it is smaller, it becomes 0. The output of comparator 59 is sent to switch 61. Terminal 62 of voltage B2
A resistor 63, a variable resistor 64, and a resistor 65 are connected in series between and ground, and the switch 61 is connected in parallel to the resistor 65.
The tap voltage of variable resistor 64 is sent to the positive phase input terminal of operational amplifier 58. The output of the operational amplifier 58 and the idle signal of the throttle position sensor 18 are sent to an OR circuit 66, and the outputs of the OR circuit 66 and the frequency divider circuit 29 are sent to the basic injection pulse generation circuit 30 via an AND circuit 67. Therefore, during the period in which the output of the OR circuit 66 is 0, the output pulse of the frequency dividing circuit 29 is prevented from being sent to the basic injection pulse generating circuit 30, and fuel cut is performed. Note that the idle signal is 0 when the throttle valve 3 is at the idling opening.

When the deceleration of the vehicle is greater than or equal to the predetermined value D, the output of the comparator 59 becomes 1, and the switch 61 is closed, thereby increasing the tap voltage of the variable resistor 64,
That is, the input voltage at the positive phase input terminal of the operational amplifier 58 is maintained at a small value V1. Further, when the deceleration of the vehicle is smaller than the predetermined value D, the output of the comparator 59 becomes 0, and the switch 61 is opened. The voltage is maintained at a value V2 greater than V1 (V2>V1). Voltage value V1,
V2 is the engine rotation speed N1, N2 (N1<N2) respectively
For example, N1 and N2 are each 1000r.pm,
It is 2000rpm. Engine speed N is N1 or
If greater than N2, the output of operational amplifier 58 is 0.
is maintained. During deceleration, the output of the throttle position sensor 18 is also maintained at 0, so during the deceleration period when the engine speed is greater than N1 or N2, the output of the OR circuit 66 is maintained at 0, and fuel is cut. Due to deceleration, the engine rotation speed N
When the value decreases to a value smaller than N1 or N2, or when the throttle valve 3 is opened to a greater extent than the idling opening, the output of the OR circuit 66 becomes 1, the fuel cut ends, and the fuel supply is restarted. The engine rotation speed at the end of fuel cut is N1 if the vehicle deceleration is greater than the predetermined value D, and N2 (N2>N2 if the vehicle deceleration is less than the predetermined value D).
N1). The deceleration of the vehicle is large during operation of the control brake and during engine braking due to the operation of the low-speed gear of the transmission, and the impact caused by the engine torque fluctuation as the fuel cut ends is small. Therefore, set the engine speed at the end of fuel cut to a sufficiently small value.
Even when set to N1, the impact is small. In addition, when the vehicle is coasting and decelerating, the shock feeling is large, so the engine rotation speed is set to N2, which generates a small shock, so that the shock feeling given to the driver etc. when the fuel cut ends can be suppressed. .

FIG. 5 is a flowchart of a program when the present invention is applied to an electronically controlled fuel injection engine that controls fuel supply from the fuel injection valve 9 only by a microprocessor without using an analog circuit. This program is executed at predetermined time intervals. In step 75, the deceleration of the vehicle is input. In step 76, it is determined whether the deceleration is greater than or equal to the predetermined value D or less than the predetermined value D. If the deceleration is greater than or equal to the predetermined value D, the process proceeds to step 77, and if the deceleration is less than the predetermined value D, the process proceeds to step 80. In step 77, the first flag is set to 1. The first flag=1 means that the deceleration at the current time is greater than or equal to the predetermined value D. In step 78, the first flag + the second flag
Determine whether the flag = 0 or 1, and if the answer to the calculation formula is 1, proceed to step 81, and if the answer to the calculation formula is 0.
If so, proceed to step 79. The first and second flags are single-digit binary numbers, so if the second flag is 1, the answer to this calculation formula is 0; if the second flag is 0, this calculation formula The answer is 1. The second flag=1 means that the deceleration was ≧D during the previous execution of the program. In step 79, if the deceleration of the vehicle is continuously maintained below the predetermined value D, the engine rotational speed at the end of the fuel cut is set to N1. In step 80, the first flag is set to 0. In step 81, if the deceleration of the vehicle at the current time is smaller than D, or if the deceleration of the vehicle at the previous execution of the program is smaller than the predetermined value D, the engine rotational speed at the end of fuel cut is set to N2 (N2 >N1). In step 82, the value of the first flag is assigned to the second flag.

In this way, the present invention sets the engine rotational speed at the end of fuel cut to a small value when the impact felt by the driver is small and the deceleration of the vehicle is larger than a predetermined value. If the deceleration of the vehicle is smaller than a predetermined value, the engine rotational speed at the end of fuel cut is set to a large value. In this way, it is possible to increase the fuel cut period while suppressing the shock feeling felt by the driver, thereby improving fuel consumption efficiency and suppressing the release of unburned components into the atmosphere. The ability to set the engine rotation speed at the end of fuel cut to a small value means that the engine rotation speed at which fuel cut could not be started using conventional fuel cut methods (in the example, engine rotation speeds greater than N1 and smaller than N2) fuel cut can also be initiated at
The impact feeling when fuel cut starts is also reduced.

[Brief explanation of the drawing]

FIG. 1 is an overall schematic diagram of an electronically controlled fuel injection engine to which the present invention is applied, FIG. 2 is an internal block diagram of the electronic control device shown in FIG. 1, and FIG. 3 is a diagram of the electronic control device shown in FIG. A waveform diagram explaining the action, Figure 4 is the second waveform diagram.
FIG. 5 is a detailed circuit diagram of the fuel cut circuit shown in FIG. 5, and FIG. 5 is a flowchart of the program when the present invention is executed by the program. 9... Fuel injection valve, 21... Acceleration/deceleration sensor,
23...Ignition coil, 24...Electronically controlled fuel injection device, 53...Fuel cut circuit.

Claims (1)

[Claims] 1 In a fuel cut method for an electronically controlled fuel injection engine that controls the amount of fuel supplied to the intake system by operating the injection valve using an electric signal, the deceleration of the vehicle is detected, and if the deceleration is larger than a predetermined value, A fuel cut method for an electronically controlled fuel injection engine, characterized in that the engine rotation speed at the end of the fuel cut is made smaller than the engine rotation speed at the end of the fuel cut when the deceleration is smaller than a predetermined value.