JPH0428898B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a fuel cut control device.

(Prior Art) In recent years, in order to improve the fuel efficiency of vehicles, systems have been put into practical use that stop fuel injection (hereinafter referred to as fuel cut) in fuel injection type vehicles when the vehicle decelerates.

When performing this fuel cut, when the engine speed drops to a predetermined speed, it must be stopped and the engine controlled normally to prevent engine stalling. However, with conventional systems, the air conditioner is sometimes used or the vehicle is When the vehicle speed was slow, the engine stall was prevented by setting the return rotation speed slightly higher than normal.

(Problem to be Solved by the Invention) However, in this conventional system, the engine torque is generated the moment the fuel cut is stopped and normal control is resumed, and the engine stalls. Occasionally, this occurred.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides means for detecting deceleration of vehicle speed, means for detecting the degree of decrease in engine speed, and means for detecting deceleration of vehicle speed at a predetermined level. and a return rotation speed switching means for switching the return rotation speed to a low rotation speed when the degree of decrease in the engine rotation speed is larger than a judgment value and smaller than a predetermined judgment value.

(Function) According to the present invention, when the deceleration of the vehicle speed is large and the degree of decrease in the engine speed is small, the shock at the time of fuel cut stop is small, so the return speed is switched to a low speed to improve fuel efficiency. be able to.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

The fuel injection system shown in FIG. 1 includes an engine 1, an air cleaner 2, an intake manifold 3 provided between the air cleaner 2 and the engine 1, and a throttle valve 4.
, an injector 5 provided on the intake manifold 3, an air flow meter 6, an exhaust manifold 7 provided on the exhaust side of the engine 1, an 02 sensor 8 provided thereon, and the downstream side of the exhaust manifold 7. a three-way catalyst device 9 provided in the engine 1; a water temperature sensor 10 provided in the water jacket of the engine 1; an intake air temperature sensor 11 provided in the intake manifold 3; A user 12, an ignition coil 13 connected thereto, and the throttle valve 4
The main components are a throttle sensor 14 that detects the opening degree of the engine, and a connection circuit 15 whose input side receives signals from each of the sensors and whose output side is connected to the injector 5.

Next, the control circuit 15 will be explained based on FIG. However, since this control circuit 15 is already known, it will be briefly explained here.

The control circuit 15 in this example mainly includes a timer, a central processing unit CPU, a storage device RAM, a ROM, an A/D converter, a D/A converter, an interrupt control section, a digital input port, a digital output port, and a power supply circuit. A basic injection pulse generator that forms a basic injection pulse using the microcomputer 16, a frequency dividing circuit that inputs and divides the primary ignition signal 13a of the ignition coil 13, and both signals from the air flow meter 6 and the frequency dividing circuit. Circuit and microcomputer 1
The injector 5 receives signals from the D/A converter 6, the water temperature sensor 10, and the intake air temperature sensor 11.
It is mainly composed of a multiplication correction circuit that controls.

Next, to explain the signals input to each circuit, the 02 sensor 8, throttle sensor 14, clutch signal 17, and starter signal 18 are input to the digital input port, and the basic injection pulse cut signal A, asynchronous An injection pulse signal B is output, a correction signal 19 is output from the D/A converter, a basic injection pulse 20 is output from the basic injection pulse generation circuit, and an injector drive pulse signal 21 is output from the multiplication correction circuit. Ru. 22 is a key switch, 23 is a battery, 24 is an OR gate, 25 is an injector register, 26 is an injector drive transistor, 27 is a diode, and 28 is a pull-up resistor.

In a vehicle having such a fuel injection system, fuel cut (hereinafter referred to as FC) control in this example is performed as follows.

First, when the FC control is restored (stopped), the engine speed varies between high level (high rotation) H and low level (low rotation) as shown in FIG. ) L is set in two stages. And this means that when the engine is warmed up normally with a coolant temperature of about 80℃, the high level is 1400rpm.
Low level is around 900rpm.

Next, an example of FC control will be explained based on the flowchart shown in FIG. 4. In this chart, it is first determined whether the throttle is fully open (this is detected by the throttle sensor 14).
If this is No, it will shift to normal control,
If Yes, it is determined whether the engine speed is 900 rpm or more (this is detected by the ignition primary signal 13a of the ignition coil 13). If the answer is No, the control shifts to normal control, and if the answer is Yes, it is determined whether the rate of change ΔNe of the engine speed is greater than a predetermined value X1. If this judgment is Yes, the engine speed Ne will be
It is determined whether the engine speed is 1400 rpm or more, and if it is No, it is determined whether the rate of change ΔNe of the engine speed is smaller than a predetermined value is performed, and if Yes, it is determined whether the engine rotation speed Ne is 1400 rpm or more.
If this is No, it will shift to normal control,
If Yes, FC processing is performed.

In this way, whether the engine speed Ne is 900 rpm
In addition to determining whether the engine speed is 1400 rpm or more, the rate of change ΔNe of the engine speed is greater than X1, that is, the engine speed is decreasing extremely rapidly, or the rate of change ΔNe is smaller than X2, that is, the degree of decrease in the engine speed. When there are few (for example,
(When coasting with the gear set to neutral, etc.)
When FC control is stopped, engine torque is generated, and the shock caused by this is large.
Rotation speed at FC control stop (return rotation speed)
Switch to a high level of 1400rpm to prevent shock from occurring. In addition, when the rate of change ΔNe of the engine speed is between the predetermined values X1 and X2, that is, during normal deceleration, the shock caused by the engine torque at the time of FC control stop is small, and the deceleration state that is relatively frequently used saves fuel consumption. Because it also leads to
Set to low level of 900rpm.

Next, embodiments of the present invention will be described. In this embodiment, the system determines two factors: Δv, which is the rate of change in vehicle speed (that is, deceleration), and ΔNe, which is the rate of change in engine speed (that is, the degree of decrease), and then returns to prevent generation of engine torque. It is configured to switch the rotation speed. That is, as shown in Fig. 5, when the rate of change in vehicle speed Δv is large and the rate of change in engine speed ΔNe is large, the rate of change in vehicle speed Δv is small and the rate of change in engine speed ΔNe is large. When the rate of change in vehicle speed Δv is small and the rate of change in engine speed ΔNe is small, when the return speed is at a low level (900 rpm),
Due to the large shock that occurs when the FC stops,
Switch the return rotation speed to high level (1400 rpm).

In addition, when the rate of change in vehicle speed Δv is large and the rate of change in engine speed ΔNe is small, fewer shocks occur when the FC is stopped, so in order to improve fuel efficiency, the return speed is set to a low level (900 rpm).
Switch to.

When the rate of change in vehicle speed Δv is large and the rate of change in engine speed ΔNe is small, it can be determined that the gear is in high gear and the brake is being applied. Because it is a stage, it is difficult for engine torque changes to be transmitted, and since the brakes are being depressed, torque changes can be absorbed by the brakes, so the shock transmitted to the driver is small.

In addition, in this example, in each FC control described above,
As shown in FIG. 6, a 300 rpm width hysteresis is set. This prevents frequent switching between activation and deactivation of the FC control.

(Effects of the Invention) As described above in detail, the present invention includes means for detecting deceleration of vehicle speed, means for detecting the degree of decrease in engine speed, and means for detecting deceleration of vehicle speed that is lower than a predetermined determination value. and a return rotation speed switching means for switching the return rotation speed to a low rotation speed when the engine rotation speed is large and the degree of decrease in the engine rotation speed is smaller than a predetermined determination value. When the deceleration of the vehicle speed is large and the degree of decrease in engine speed is small, such as when the brake is pressed, the shock at the time of fuel cut-off is small, so the return speed is switched to a low speed to reduce fuel consumption. You can improve your performance.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a fuel injection system according to an embodiment of the present invention, Fig. 2 is a block diagram of its control circuit, and Fig. 3 shows the relationship between engine cooling water temperature and fuel cut control return rotation speed. FIG. 4 is a flowchart showing an example of fuel cut control; FIG. 5 is an explanatory diagram showing an embodiment of fuel cut control according to the present invention;
FIG. 6 is an explanatory diagram showing the hysteresis of fuel cut control. 1...Engine, 5...Injector, 10...
... Water temperature sensor, 15 ... Control circuit, ΔNe ... Rate of change in engine speed (degree of decrease), Δv ... Rate of change in vehicle speed (deceleration), H ... High level (high rotation),
L...Low level (low rotation).

Claims (1)

[Scope of Claims] 1. An injector mounted on an intake manifold or the like of an engine, and a control circuit for controlling the injector according to engine specifications, when the engine decelerates under predetermined conditions, the injector In the fuel cut control device, the fuel cut control device stops the fuel injection of the vehicle, and stops the fuel stop operation and returns to normal control when the engine speed decreases to a predetermined return speed after the start of the fuel stop operation. means for detecting deceleration; means for detecting a degree of decrease in engine speed; and when the deceleration of the vehicle speed is greater than a predetermined determination value and the degree of decrease in the engine speed is smaller than a predetermined determination value; A fuel cut control device comprising: a return rotation speed switching means for switching the return rotation speed to a low rotation speed.