JP2518317B2 - Fail-safe device for internal combustion engine for vehicles - Google Patents

Description

TECHNICAL FIELD The present invention relates to a fail-safe device for an internal combustion engine for a vehicle.

[Conventional technology and its problems]

2. Description of the Related Art Conventionally, as a fuel injection device for a vehicle internal combustion engine, a device that detects an intake air amount and a rotational speed, determines a basic injection time from the intake air amount and the rotational speed, and controls a fuel amount injected from an injection valve ( L-EFI) or the intake pressure and the rotational speed are detected, and the basic injection time is determined from the intake pressure and the rotational speed to control the amount of fuel injected from the injection valve (D-EFI).
and so on.

By the way, in the D-EFI that controls the fuel injection amount based on the intake pressure and the rotational speed, when the pipe is damaged on the downstream side of the throttle valve, the detected intake pressure becomes the atmospheric pressure, and a large amount of fuel is injected. However, since the air is supplied to the engine from the damaged portion without being throttled by the throttle valve, the rotational speed of the engine may increase abnormally.

By the way, conventionally, in JP-A-57-52643, when the throttle opening is below a predetermined value and the pressure detected by the pressure sensor shows a value close to the atmospheric pressure, the fuel injection amount is determined by the intake pressure and the rotational speed. There is a known technique for switching the control so that the fuel injection amount is controlled by the throttle opening and the number of revolutions, but the engine stalls because the air-fuel ratio is extremely thin when the throttle valve is closed. .

In addition, if the driver operates the accelerator and the throttle valve is opened to a certain extent because the driver is about to fall into a stall, the rotational speed may suddenly increase.

Therefore, it is an object of the present invention to provide a fail-safe device for an internal combustion engine for a vehicle, which can surely prevent abnormal operation of the engine even if the pipe is damaged downstream of the throttle valve in the D-EFI. .

[Means for solving problems]

In order to solve the above problems, the fifth aspect of the present invention is used.
As shown in the figure, it is a fail-safe device for a vehicle internal combustion engine, which is controlled by the control means based on the intake pressure detected by the intake pressure detection means and the rotation speed detected by the rotation speed detection means. An opening detection means for detecting the opening of the valve, an upper limit intake pressure setting means for setting an upper limit intake pressure according to the throttle opening detected by the opening detection means, and an intake pressure detected by the intake pressure detection means. When the atmospheric pressure and the upper limit intake pressure set by the upper limit intake pressure setting means are compared, and the intake pressure exceeds the upper limit intake pressure,
Judgment means for judging that an abnormality has occurred in the intake system downstream of the throttle valve, and output reduction means for lowering the fuel cut rotation speed for preventing overspeed in order to reduce the output of the engine based on the judgment result of the judgment. And have.

[Action]

According to the above configuration, when the actual intake pressure exceeds the upper limit intake pressure determined according to the throttle opening, the output reducing means reduces the fuel cut rotational speed to prevent over-rotation to reduce the engine output. To be done.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a configuration diagram showing a configuration of an engine and its peripheral equipment to which an embodiment of the present invention is applied. In the figure,
The engine 1 is a 4-cylinder spark ignition type engine mounted on a vehicle. The intake pipe 2 of the engine 1 has an intake temperature sensor 3 for detecting the intake temperature from the upstream side, a throttle opening sensor 5 for detecting the throttle opening of the throttle valve 4, and an intake sensor for detecting the pressure on the downstream side of the throttle valve 4. Barometric pressure sensor 6,
An electromagnetically operated injection valve 7 for supplying fuel to the engine 1 is provided. The engine 1 has a spark plug 8
And a temperature sensor 9 for detecting the engine temperature (cooling water temperature). Further, an atmospheric pressure sensor 10 is provided to detect the atmospheric pressure. An igniter 11 and a distributor 12 are provided for the spark plug 8, and the distributor 12 is provided with a rotation speed sensor 13 for detecting the engine rotation speed.

The signal of each sensor is input to the ECU 15, and the ECU 15 outputs a control signal to the injection valve 7 and the igniter 11. Specifically, the ECU 15 calculates the basic injection time width and the basic ignition timing based on the intake pressure and the rotational speed, and corrects them based on the intake temperature, the throttle opening, the engine temperature, and the atmospheric pressure, and the current injection time. The width and the ignition timing are determined, and a control signal corresponding to each is output.

By the way, in the ECU 15, the processing shown in the flowchart of FIG. 2 is executed. It should be noted that this process is executed every predetermined period. First, in step 201, intake pressure PM
In step 202, the throttle opening TA is acquired, and in step 203, the rotational speed NE is acquired. Then, in step 204, the predicted upper limit intake pressure PM 'is calculated from a map which is experimentally obtained in advance based on the throttle opening TA and the rotational speed NE and is stored in the storage device in the ECU 15.

Further, in step 205, when the engine temperature is low, the intake pressure PM is changed because the intake amount is increased through the passage bypassing the throttle valve 4 in order to promote warm-up, so the intake pressure PM changes according to the engine temperature. Correct the atmospheric pressure PM ′,
Furthermore, it is also corrected by atmospheric pressure and auxiliary equipment load (air conditioner load etc.). It is possible that the intake pressure with respect to the throttle opening may change due to a change with time in the vicinity of the throttle valve 4. Therefore, the upper limit intake pressure calculated corresponding to the throttle opening may be learned by the intake pressure. Good.

Next, at step 206, the upper limit intake pressure PM ′ corrected at step 205 and the intake pressure PM taken at step 201 are
When PM> PM ′, step 207, PM ≦ PM ′
In case of, this processing ends.

In step 207, it is determined that some abnormality has occurred in the intake system. Therefore, the fuel cut (F / F / F) provided to cut the fuel when the engine speed excessively increases (for example, 6500 rpm or more). C) Rotation speed is 1
After performing the process of lowering to 500 rpm, this process is terminated.

According to the above-described processing, in the state where the intake pressure PM exceeds the predicted upper limit intake pressure PM ′ corresponding to the throttle opening TA and the rotational speed NE, the engine speed is reduced because the fuel cut rotational speed is lowered. The number is suppressed from increasing above the lowered fuel cut speed, that is, the engine output is reduced so as not to exceed a predetermined value.

If damage occurs on the downstream side of the throttle valve 4 so that the downstream side of the throttle valve 4 substantially coincides with atmospheric pressure, the D-EFI that does not have the configuration of this embodiment is the third
As shown in the figure, the engine speed reaches the conventional fuel cut speed (for example, 6500 rpm) immediately after the failure. However, according to the configuration of this embodiment, as shown in FIG.
Since the fuel cut rotation speed is reduced by the process shown in the figure, the rotation speed does not increase above the lowered fuel cut rotation speed, and thus an excessive increase in rotation is prevented.

By the way, in the above embodiment, the upper limit intake pressure PM ′ is set in correspondence with the opening TA of the throttle valve 4 and the rotational speed NE.
Provide an idle switch that turns on when the throttle valve 4 is almost fully closed, and set the upper limit intake pressure corresponding to the rotational speed NE when the idle switch is on, that is, when the throttle valve 4 is almost fully closed. The upper limit intake pressure may be compared with the intake pressure when the idle switch is ON.

Further, in the above embodiment, when a failure of the intake system is detected, the engine output is reduced by lowering the fuel cut rotational speed, but the output of the engine may be reduced by other means, for example, The fuel injection may be thinned out, the ignition may be thinned out, the air-fuel ratio may be made lean, or the ignition timing may be retarded. Further, it may be on the downstream side of the throttle valve 4 and slightly upstream of the engine 1. In this case, an auxiliary throttle valve that is normally fully open may be provided to allow the auxiliary throttle valve to be closed to an opening degree that allows idle operation in the event of a failure. The operation of the feeder may be stopped to reduce the supercharging pressure, and the output may be reduced by combining any of the above means.

〔The invention's effect〕

As described above, according to the present invention, in the engine which controls the engine by the intake pressure and the rotational speed, even if the intake system is damaged downstream of the throttle valve, the state can be judged by the judgment means, and the throttle can be judged. By reducing the fuel cut speed when the actual intake pressure is higher than the upper limit intake pressure according to the valve opening, even if an abnormality occurs in the intake system downstream of the throttle valve, the configuration is simple and the engine does not stall. It is possible to sufficiently prevent the engine speed from rising excessively.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a configuration of an engine and peripheral equipment to which an embodiment of the present invention is applied, and FIG. 2 is an ECU of FIG.
FIG. 3 is a flow chart showing the processing executed in FIG. 3, FIG. 3 is a time chart at the time of failure in the conventional configuration, FIG. 4 is a time chart at the time of failure in the configuration of the present embodiment, and FIG. 5 is a block diagram showing the configuration diagram of the present invention. Is. 1 ... Engine, 2 ... Intake pipe, 5 ... Throttle opening sensor, 6 ... Intake pressure sensor, 15 ... ECU.

Front Page Continuation (72) Inventor Masumi Izumi 1-1, Showa-cho, Kariya City, Aichi Prefecture, Nippon Denso Co., Ltd. (72) Inventor Shigenori Isomura 1-1-cho, Showa-cho, Aichi Prefecture Nippon Denso Co., Ltd. (72 ) Inventor Mitsunori Takao 1-1, Showa-cho, Kariya city, Aichi Prefecture (56) References JP 58-214632 (JP, A) JP 60-11648 (JP, A) JP 64-340 (JP, A)

Claims (1)

(57) [Claims] 1. A fail safe device for an internal combustion engine for a vehicle, which is controlled by a control means on the basis of an intake pressure detected by an intake pressure detection means and a rotation speed detected by a rotation speed detection means. An opening detection means for detecting the opening of the valve, an upper limit intake pressure setting means for setting an upper limit intake pressure according to the throttle opening detected by the opening detection means, and an intake pressure detected by the intake pressure detection means. A comparison is made between the atmospheric pressure and the upper limit intake pressure set by the upper limit intake pressure setting means, and when the intake pressure exceeds the upper limit intake pressure, it is determined that an abnormality has occurred in the intake system downstream of the throttle valve. Means for reducing the output of the engine based on the determination result of the determination means, and an output reduction means for reducing the fuel cut speed for preventing over-rotation, for a vehicle. Fail-safe system of combustion engine.