JPS624542B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel cutoff method for an internal combustion engine, in particular, a method suitable for use in an automobile engine equipped with an electronically controlled fuel injection device, in which an intake throttle valve is closed;
The present invention also relates to an improvement in a fuel cutoff method for an internal combustion engine, which cuts off fuel supply when the engine speed is equal to or higher than a predetermined speed.

In internal combustion engines, especially automobile engines equipped with electronically controlled fuel injection devices, for example, the intake throttle valve is closed during deceleration in order to reduce emissions of harmful components such as hydrocarbons in exhaust gas and improve fuel efficiency. When the valve is closed and the engine speed is above a predetermined speed, the fuel supply is cut off and fuel is cut off. However, due to this fuel cut, the torque generated by the engine changes from positive to negative, giving a shock to the vehicle when the fuel is cut. Therefore, it was not possible to reduce the fuel cut rotation speed very low, and it was not possible to sufficiently improve fuel efficiency and exhaust gas purification performance.

In addition, the fuel cut rotation speed is controlled to be switched to a high rotation side or a low rotation side depending on the running speed of the vehicle (referred to as vehicle speed), the clutch switch of a manual transmission, the neutral switch of an automatic transmission, etc. Although a method has been proposed to prevent the fuel from being cut, it has not been sufficient as a countermeasure against fuel cut shocks. That is, for example, as shown in FIG. 1, depending on the operating state of the brake,
The fuel cut rotation speed is set to the low rotation side (dashed line A) when the brake is in an operating state, and on the high rotation side (dashed line B) when the brake is not operated.
However, this method has a problem in that the fuel cut-off becomes larger for lower speed gears. In the figure, solid line C ₁ is a straight line showing the relationship between vehicle speed and engine speed in 1st gear, and solid line C ₂ is
Straight line and solid line also show the relationship in 2nd gear
C ₃ is a straight line that similarly shows the relationship in 3rd gear, solid line C ₄ is a straight line that also shows the relationship in 4th gear, and solid line C ₅ is a straight line that also shows the relationship in 5th gear.

The present invention has been made in order to eliminate the above-mentioned conventional drawbacks, and provides a fuel cutoff method for an internal combustion engine that can alleviate the shock caused by fuel cutoff and improve fuel efficiency and exhaust gas purification performance. With the goal.

The present invention provides a fuel cutoff method for an internal combustion engine in which the fuel supply is cut off when an intake throttle valve is closed and the engine speed is above a predetermined speed, and the brake is not operated and the fuel supply is cut off. ,
The above objective is achieved by not cutting off the fuel supply when the vehicle speed is less than a predetermined vehicle speed.

Additionally, if the brake changes from an operating state to a non-operating state while the fuel supply is cut off, the fuel supply cutoff is released regardless of the vehicle speed and engine speed, allowing smooth re-acceleration. It was made so that it would become so.

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

This embodiment includes an air cleaner 12 for taking in outside air, an air flow meter 14 for detecting the flow rate of the intake air taken in by the air cleaner 12, and a built-in air flow meter 14, as shown in FIG. For example, a potentiometer-type intake air amount sensor 16, an intake air temperature sensor 18 for detecting the temperature of intake air, which is also built into the air flow meter 14, and an intake pipe 20 downstream of the air flow meter 14. An intake throttle valve 22 for controlling the flow rate of intake air, which is arranged to rotate in conjunction with an accelerator pedal (not shown) disposed at the driver's seat; and the intake throttle valve 22.
an idle switch 24 for detecting that the engine is closed and in the idle position; and an injector 28 for injecting fuel toward the intake port of the engine 10, which is disposed in the intake manifold 26.
and arranged on the downstream side of the exhaust manifold 30,
An oxygen concentration sensor 32 for detecting the air-fuel ratio from the residual oxygen concentration in exhaust gas, a three-way catalytic converter 36 disposed downstream of the exhaust pipe 34, and a brake pedal 38 disposed at the driver's seat. A brake switch 40 is disposed on the back side and outputs an on signal when the brake pedal 38 is depressed.
, a vehicle speed sensor 44 that is disposed in the transmission 42 and detects the vehicle speed from the rotation speed of the propeller shaft, and a rotation speed sensor 46 that outputs a pulse signal with a frequency corresponding to the rotation speed of the crankshaft of the engine 10.
, the cooling water temperature sensor 48 that detects the cooling water temperature of the engine 10, the intake air amount detected by the intake air amount sensor 16 in the air flow meter 14, and the engine rotation speed detected by the rotation speed sensor 46. In addition to determining the fuel injection time of
an air-fuel ratio control circuit that creates a valve-opening time signal by making corrections according to the outputs of the oxygen concentration sensor 32, the cooling water temperature sensor 48, etc., and controls the air-fuel ratio by controlling the valve-opening time of the injector 28; 5
0, when the brake switch 40 is in the on state in the air-fuel ratio control circuit 50, the idle switch 2
4 is on, and the rotation speed sensor 46
When the engine speed determined from the output is equal to or higher than a predetermined speed, the valve opening time signal is set to zero to cut off the fuel supply, while the brake switch 40
is in the off state, the idle switch 24 is on, the vehicle speed determined from the vehicle speed sensor 44 is equal to or higher than the predetermined vehicle speed, and the engine rotation speed determined from the output of the rotation speed sensor 46 is at the predetermined rotation speed. When this is the case, the valve opening time signal is set to zero to cut off the fuel supply, and when the idle switch 24 is on and the brake switch 40 changes from the on state to the off state, the vehicle speed and engine Regardless of the rotation speed, a regular valve opening time signal is output to the injector 28 to release the fuel supply cutoff.

The air-fuel ratio control circuit 50, as shown in detail in FIG. 3, for example, counts the engine rotation speed once per engine rotation based on the output of the microprocessor 52 that calculates the fuel injection amount and the rotation speed sensor 46. At the same time, the rotation number counter 54 outputs an interrupt command signal to the interrupt control unit 56 at the end of counting, and generates an interrupt signal in response to the interrupt command signal output from the rotation number counter 54, and causes the microprocessor 52 to inject fuel. an interrupt control unit 56 that executes an interrupt processing routine for calculating the amount, the idle switch 24, and the brake switch 4;
0, the output signal of the vehicle speed sensor 44, and the starter switch 5 that controls the operation of the starter (not shown)
A digital input port 60 receives digital signals such as a starter signal inputted from 8 at a timing suitable for input and transmits them to the microprocessor 52, the intake air amount sensor 16, and the intake air temperature sensor 1.
8. An analog input port consisting of an analog multiplexer and an analog-to-digital converter for converting analog signals input from the oxygen concentration sensor 32, cooling water temperature sensor 48, etc. into digital signals and sequentially reading them into the microprocessor 52. 6
2, the rotation number counter 54, and the interrupt control section 5
6. A common bus 64 for transmitting output information from the digital input port 60, analog input port 62, etc. to the microprocessor 52, a power supply circuit 70 connected to the battery 68 via a key switch 66, and the microprocessor 52. a random access memory 72 that can be read and written to temporarily store calculation data, etc.; a read-only memory 74 that stores programs and various constants; and the microprocessor 52. Injector 2 calculated by
8, that is, a fuel injection time control counter consisting of a down counter including a register for converting a digital signal representing the fuel injection amount into a pulse signal with a pulse width giving the actual valve opening time of the injector 28. 76, a power amplifying section 78 for converting the pulse signal output from the fuel injection time control counter 76 into a valve opening time signal for driving the injector 28, a timer 80 for measuring elapsed time, and the idle switch. 24, brake switch 40, vehicle speed sensor 44, rotation speed sensor 4
6, when the brake switch 40 is in the on state, the fuel supply is cut off when the idle switch 24 is on and the engine speed is above a predetermined speed; 40 is in the off state, the idle switch 24 is on, the vehicle speed determined from the vehicle speed sensor 44 is equal to or higher than the predetermined vehicle speed, and
The fuel supply is cut off when the engine speed is higher than a predetermined speed, and the idle switch 24
is on, and when the brake switch 40 changes from the on state to the off state, a fuel cut signal is output to the power amplification section 78 so as to release the fuel supply cutoff regardless of the vehicle speed and engine rotation speed. The fuel cut control circuit 82 includes a fuel cut control circuit 82.

The action will be explained below.

Fuel cut control according to the present invention is performed as shown in FIG. That is, first step 101
Then, it is determined whether the idle switch 24 is on. If the idle switch 24 is not on, the intake throttle valve 22 is open, so the process proceeds to step 102 and fuel injection is performed using the valve opening time signal calculated by a known method. On the other hand, if the idle switch 24 is on, the process proceeds to step 103, where it is determined whether the brake switch 40 is on. When the brake switch 40 is on, that is, when the brake pedal 38 is depressed,
Proceed to step 104 and set the brake flag to 1 this time.
At the same time, in step 105, it is determined whether or not the engine rotation speed determined from the output of the rotation speed sensor 46 is equal to or higher than a predetermined rotation speed Nrpm. If the engine speed is Nrpm or more, the process proceeds to step 106, where fuel cut is performed, and further, in step 107, the contents of the current brake flag are transferred to the previous brake flag in order to determine the brake state during the next processing. . Further, if it is detected in step 103 that the brake switch 40 is off, that is, that the brake pedal 38 is not depressed, the process proceeds to step 108.
Proceed to and set the brake flag to 0 this time. Furthermore,
In step 109, it is determined whether the sum of the contents of the current brake flag and the contents of the previous brake flag is 0. If the sum of the contents of the current brake flag and the contents of the previous brake flag is not 0, that is, the contents of the previous brake flag are 1.
If the brake changes from the operated state to the non-operated state this time, the process proceeds to the aforementioned step 102, and fuel injection is performed regardless of the vehicle speed and engine rotational speed. Also, in step 109, the sum of the contents of the current brake flag and the contents of the previous brake flag is 0.
, that is, the brake remains inactive, step 11
0, and it is determined whether the vehicle speed determined from the output of the vehicle speed sensor 44 is equal to or higher than a predetermined vehicle speed VKm/h. If the vehicle speed is VKm/h or higher, the process proceeds to step 105 mentioned above, where it is determined whether the engine speed is equal to or higher than the predetermined rotation speed Nrpm, and then the process described above is performed according to the result of the determination. Either the fuel is cut off in step 106, or the fuel is injected in step 102. On the other hand, if it is determined in step 110 that the vehicle speed is less than VKm/h, the process proceeds to step 102, where fuel injection is performed regardless of the engine speed at that time.

In this way, when the brake pedal 38 is depressed and the deceleration state is entered, the idle switch 24 is turned on and the brake switch 40 is turned on, so that the engine rotation speed determined from the output of the rotation speed sensor 46 If the rotation speed is equal to or higher than the set rotation speed Nrpm, fuel cut is performed. On the other hand, if the brake pedal 38 is not depressed and the deceleration state is entered, the idle switch 24 is turned on, but since the brake switch 40 is off, the vehicle speed is determined according to the vehicle speed determined from the output of the vehicle speed sensor 44. If the vehicle speed is equal to or higher than the set vehicle speed VKm/h, fuel cut is performed when the engine speed determined from the rotational speed sensor 46 is equal to or higher than the set vehicle speed Nrpm. When this occurs, fuel cut is stopped and fuel injection is performed regardless of the set rotational speed Nrpm.

FIG. 5 shows the relationship between the vehicle speed and engine rotational speed, the fuel cut rotational speed when the brake is operated (broken line A), and the fuel cutoff vehicle speed when the brake is not operated (broken line D) in this embodiment.

In this embodiment, when the intake throttle valve is closed and the brake changes from an operating state to a non-operating state, the fuel supply cutoff is released regardless of the vehicle speed and engine rotation speed. Therefore, once the brake is operated to decelerate, re-acceleration is performed smoothly.

In this example, as shown in FIG.
Broken line A showing the fuel cut rotation speed during brake operation
Since the intersection point E of the dashed line D indicating the fuel cut vehicle speed when the brake is not operated is below the straight line _C5 indicating the characteristics of the fifth gear, which is the highest speed gear, the vehicle speed is determined to be VKm/h at step 110 in FIG. If the above is determined, the condition for determining the engine speed in step 105 is omitted, and as shown by the broken line F in FIG.
If it is determined in step 110 that the vehicle speed is equal to or higher than VKm/h, it is possible to immediately proceed to step 106 and perform a fuel cut. However, as shown by the dashed-dotted line G in Fig. 5, the fuel cut vehicle speed is set lower, and the intersection H of the dashed-dotted line G and the broken line A is lower than the straight line _C5 , which indicates the characteristics of the highest speed gear (5th gear). If it is in the upper left, it is necessary to insert step 105 between step 110 and step 106, as shown by the solid line in FIG.

In the above embodiment, the present invention is applied to an automobile engine equipped with an intake air volume type electronically controlled fuel injection device, but the scope of application of the present invention is not limited thereto, and is applied to an intake pressure type electronically controlled fuel injection device. It is obvious that the present invention can be similarly applied to an automobile engine equipped with an electronically controlled fuel injection device or a general internal combustion engine equipped with a carburetor.

As explained above, according to the present invention, when the brake is operated to alleviate the fuel cut shock, fuel cut is performed in the same way as in the conventional case, whereas when the brake is not operated, when the fuel cut shock becomes a problem,
Since fuel injection is restarted at higher speeds in lower gears, fuel cut-off is significantly alleviated and vehicle driving performance is greatly improved. This makes it possible to significantly expand the fuel cut range, and has excellent effects such as improving fuel efficiency and exhaust gas purification performance.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the fuel cut rotation speed when the brake is operated and when the brake is not operated in an example of a conventional fuel cutoff method for an internal combustion engine, and FIG. 2 is a diagram showing the fuel cutoff speed for an internal combustion engine according to the present invention. FIG. 3 is a block diagram showing an automobile engine equipped with an intake air amount type electronically controlled fuel injection device in which the embodiment of the invention is adopted. FIG. 3 shows the configuration of the air-fuel ratio control circuit used in the device. FIG. 4 is a block diagram showing an example. FIG. 4 is a flowchart showing a fuel cut control program used in the device. FIG. FIG. 3 is a diagram showing fuel cut vehicle speed. 10...Engine, 22...Intake throttle valve, 24
...Idle switch, 28...Injector,
38... Brake pedal, 40... Brake switch, 42... Transmission, 44... Vehicle speed sensor, 4
6...Rotational speed sensor, 50...Air-fuel ratio control circuit, 52...Microprocessor, 54...Revolution counter, 56...Interrupt control section, 60...Digital input port, 62...Analog input port, 72... Random access memory, 74...
Read-only memory, 76... counter for fuel injection time control, 78... power amplification section, 82... fuel cut control circuit.

Claims (1)

[Scope of Claims] 1. A fuel cutoff method for an internal combustion engine that cuts off fuel supply when an intake throttle valve is closed and the engine speed is equal to or higher than a predetermined speed, wherein the brake is in an inoperable state. 1. A fuel cutoff method for an internal combustion engine, characterized in that the fuel supply is not cut off when the running speed of the vehicle is less than a predetermined vehicle speed. 2. According to claim 1, when the brake changes from an operating state to a non-operating state while the fuel supply is cut off, the fuel supply cutoff is released regardless of the vehicle speed and engine rotation speed. How to shut off fuel in an internal combustion engine.