JPH0520578B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a fuel cutoff method for an internal combustion engine.

[Conventional technology]

In conventional fuel cutoff methods, fuel cutoff is performed by detecting the deceleration period using a throttle sensor that detects the opening of the throttle valve and an engine rotation speed sensor (crank angle sensor); The fuel return engine rotational speed at which fuel recovery is stopped is set to be constant regardless of vehicle speed.

[Problem to be solved by the invention]

In this case, the lower the fuel recovery engine rotation speed, the longer the fuel cutoff period will be, so fuel consumption can be reduced. However, if the fuel recovery engine rotation speed is lowered, a shock will occur when fuel supply is restarted at a low vehicle speed. The problem is that it becomes large.

[Means to solve the problem]

According to the present invention, in order to solve the above problems, in a fuel cutoff method for an internal combustion engine that cuts off fuel supply to the intake system during a deceleration period of the internal combustion engine, the fuel cutoff is stopped when the vehicle speed is equal to or higher than a predetermined value. The fuel return engine rotational speed is set to a smaller value than in other cases.

[Effect]

When the vehicle speed is above a predetermined value, the fuel return engine rotation speed is lowered, and when the vehicle speed is below the predetermined value, the fuel return engine rotation speed is increased.

〔Example〕

FIG. 1 is an overall schematic diagram of an electronically controlled fuel injection engine to which the present invention is applied. The air sucked by the air cleaner 1 is transferred to the air flow meter 2, throttle valve 3,
Surge tank 4, intake port 5, and intake valve 6
The air is sent to the combustion chamber 8 of the engine body 7 via the intake passage 12 containing the air. Throttle valve 3 is the accelerator pedal 1 in the driver's cab.
Linked to 3. The combustion chamber 8 is divided by a cylinder head 9, a cylinder block 10, and a piston 11, and the exhaust gas generated by combustion of the air-fuel mixture is passed through an exhaust valve 15, an exhaust port 16, an exhaust branch pipe 17, and an exhaust pipe. 18 to the atmosphere. The bypass passage 21 connects the upstream of the throttle valve 3 and the surge tank 4, and the bypass flow control valve 22
controls the flow cross-sectional area of the bypass passage 21 to maintain a constant engine rotational speed during idling. An exhaust gas recirculation (EGR) passage 23 that guides exhaust gas to the intake system in order to suppress the generation of nitrogen oxides is
The exhaust branch pipe 17 and the surge tank 4 are connected, and an on-off valve type exhaust gas recirculation (EGR) control valve 24 opens and closes the EGR passage 23 in response to electric pulses. The intake temperature sensor 28 is the air flow meter 2
A throttle position sensor 29 is provided inside to detect the intake air temperature, and a throttle position sensor 29 detects the opening degree of the throttle valve 3. The water temperature sensor 30 is attached to the cylinder block 10 to detect the cooling water temperature, that is, the engine temperature, and the air-fuel ratio sensor 31, known as an oxygen concentration sensor, is attached to the collecting part of the exhaust branch pipe 17 to detect the oxygen concentration in the collecting part. The crank angle sensor 32
detects the crank angle of the crankshaft from the rotation of the shaft 34 of the power distributor 33 connected to the crankshaft (not shown) of the engine body 7, and the vehicle speed sensor 35 detects the rotational speed of the output shaft of the automatic transmission 36. do. These sensors 2, 28, 29, 30, 31, 32, 35
The output of the storage battery 37 and the voltage of the storage battery 37 are sent to the electronic control unit 40. A fuel injection valve 41 is provided near each intake port 5 corresponding to each cylinder,
Pump 42 sends fuel from fuel tank 43 to fuel injection valve 41 via fuel passage 44 . The electronic control unit 40 calculates the amount of fuel to be injected as a function of the input signals from each sensor, and sends an electrical pulse to the fuel injection valve 41 with a pulse width corresponding to the calculated amount of fuel to be injected. The electronic controller 40 also controls the bypass flow control valve 22, the EGR control valve 24, the solenoid 45 of the automatic transmission hydraulic control circuit, and the ignition device 46. The secondary side of the ignition coil of the ignition device 46 is connected to the power distributor 33 .

FIG. 2 is an internal block diagram of the electronic control unit. CPU (central processing unit) 56, ROM (read-only memory) 57, RAM (direct access memory) 58, C-RAM (complementary RAM) 59, A/D (analog/digital) converter with multiplexer 60, and The input/output interface 61 is
They are connected to each other via a bus 62. C-
The RAM 59 is connected to an auxiliary power source, and is supplied with a predetermined amount of power even when the ignition switch is opened and the engine is stopped so that the memory can be retained. Analog signals from the air flow meter 2, intake temperature sensor 28, water temperature sensor 30, and air-fuel ratio sensor 31 are sent to an A/D converter 60. Throttle position sensor 29, crank angle sensor 32,
The output of the vehicle speed sensor 35 is sent to the input/output interface 61, and the bypass flow control valve 22,
EGR control valve 24, solenoid 45, and ignition device 46 receive input signals from input/output interface 61.

FIG. 3 is a flowchart of a program implementing the present invention. In step 65, it is determined whether the idle switch is on, that is, whether or not the throttle valve 3 is at the idling opening. If the determination result is positive, the process proceeds to step 66, and if not, the process proceeds to step 77. The idle switch is included in the throttle sensor 29 mentioned above. In step 66, it is determined whether the engine rotation speed Ne≧Nc, and if the determination result is positive, the process proceeds to step 67, and if not, the process proceeds to step 68. Nc is the minimum engine rotation speed at which fuel cutoff starts, and has a relationship of Nc≧Nh with respect to Nh, which will be described later. At step 67, the flag f=1. The flag f is a flag to indicate that the conditions for implementing a fuel cutoff are satisfied, and once it becomes 1, it is maintained at 1 until the fuel supply is restarted. At step 70, the flag f/c is set to 1. If flag f/c=1, a fuel cutoff is performed. In step 68, it is determined whether f=1 or not. If the determination result is positive, proceed to step 69, and if not, proceed to step 77.
Proceed to. In step 69, it is determined whether the engine rotation speed Ne≧Nh or not, and if the determination result is positive, the process proceeds to step 70.
If not, proceed to step 74. Nh and Nl (described later) are engine rotational speeds at which fuel cutoff is stopped, that is, fuel supply is restarted, and Nh>
It is Nl. In step 74, it is determined whether the vehicle speed V≧V0 or not. If the determination result is positive, the process proceeds to step 76, and if not, the process proceeds to step 75. In step 75, it is determined whether or not the braking device, ie, the brake, is in operation. If the determination result is positive, the process proceeds to step 76, and if not, the process proceeds to step 77. In step 76, it is determined whether the engine rotation speed Ne≧Nl, and if the determination result is positive, the process proceeds to step 70, and if not, the process proceeds to step 70.
Proceed to 77. At step 70, the flag f=0.
At step 78, the flag f/c=0, so the fuel cutoff is canceled, that is, fuel is supplied. Therefore, during deceleration of the internal combustion engine, the engine rotational speed Ne
If it is above Nc, fuel cutoff will be performed and the vehicle speed V will be
If the engine rotational speed Ne is higher than V0 or the brake is in operation, the fuel cutoff is canceled when the engine speed Ne decreases to the smaller set value Nl.
In other cases, the fuel cutoff is canceled when the engine speed Ne decreases to the larger set value Nh.
In addition, as a preferred embodiment, Nc=2000r.pm,
Nh=1800r.pm, Nl=1000r.pm.

FIG. 4 shows the implementation range and the stop range of fuel cutoff in the present invention. In addition, in Fig. 4, the vehicle speed V- at 2nd, 3rd, and 4th speeds
It shows the relationship between engine rotational speed Ne. The higher the vehicle speed or engine rotational speed is, the less the vehicle occupant will feel the rolling motion of the vehicle due to the impact caused by fluctuations in the output torque of the engine when the fuel is restored, that is, when the fuel supply is resumed after a fuel cutoff. This is because, as the vehicle speed or engine rotational speed increases, the rolling motion of the vehicle is alleviated due to the large inertia of the vehicle or engine rotating parts. Therefore, V≧
High speed region A and V< as V0 and Ne≧Nl
In the high rotation region B where V0 and Ne≧Nh, the fuel can be cut off without any problem. Further, while the braking device is in operation, a braking force acts on the vehicle and the rolling of the vehicle is considerably alleviated. Therefore, V<V0
In region C where Nl≦Ne<Nh, fuel cutoff is performed only when the brake system is in operation.
Area D is an area where fuel cutoff is not performed. In this way, the fuel cut-off area is enlarged as a whole.

〔Effect of the invention〕

When the vehicle speed is above a predetermined value, the fuel return engine rotation speed is lowered, and when the vehicle speed is below a predetermined value, the fuel return engine rotation speed is increased, thereby suppressing the impact that occurs when fuel supply is resumed. The fuel cut-off period can be increased, thus reducing fuel consumption.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an electronically controlled fuel injection engine to which the present invention is applied, FIG. 2 is a block diagram of the electronic control device of FIG. 1, FIG. 3 is a flowchart of a program for implementing the present invention, and FIG. The figure is a diagram showing areas in which fuel cutoff is performed and stopped. 29...Throttle sensor, 32...Crank angle sensor, 40...Electronic control device.

Claims (1)

[Claims] 1. In a fuel cutoff method for an internal combustion engine that cuts off the fuel supply to the intake system during the deceleration period of the internal combustion engine, when the vehicle speed is above a predetermined value, the fuel return engine rotation speed at which the fuel cutoff is stopped is set higher than in other cases. A fuel cutoff method for an internal combustion engine, characterized by setting the fuel to a small value.