JP2901612B2 - Engine intake system failure detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to an intake system failure detection device for an engine.

[Prior art]

In a so-called D-JETRO type fuel injection control system for an engine, a basic fuel injection amount is determined in accordance with an intake pipe pressure of an engine and an engine speed, and the basic fuel injection amount is corrected in accordance with an engine operating state. I have. However, there is a case where air such as a blind plug is removed by a backfire or the like downstream of the throttle valve and air abnormally flows into the intake manifold without passing through the throttle valve. In this case, in the above-described fuel injection control system, the fuel injection amount is increased by the air flow rate increased by the abnormal inflow of air, because the fuel injection amount is determined in accordance with the suction pipe internal pressure. As a result, the engine speed may increase abnormally against the driver's will. Therefore, as described in, for example, Japanese Patent Application Laid-Open No. 58-214632, even when air abnormally flows downstream of the throttle valve, the engine fuel is prevented from abnormally increasing. An injection control system has been proposed. Here, the value of the suction pipe pressure is assumed in advance from the throttle valve opening and the engine speed, and the actual detected value of the suction pipe pressure is compared with the above assumed value. When it is large, the basic fuel injection amount is fixed at a predetermined value, thereby preventing an abnormal increase in the engine speed.

[Problems to be solved by the invention]

However, when the engine is started, the engine speed and the pressure in the suction pipe fluctuate greatly, and further, in the process in which the pressure in the suction pipe, which was the atmospheric pressure before the start, settles down to a steady state,
The response delay of the pressure in the suction pipe due to the volume of the suction system occurs. For this reason, the predetermined pressure calculated from the throttle opening and the engine speed may temporarily fall below the suction pipe pressure, and an erroneous determination that an abnormality in the intake system is determined even if there is no failure in the intake system. There is a possibility. The present invention has been made based on the above circumstances, and detects an abnormality in an intake system based on at least three parameters of a throttle opening, an engine speed, and a pressure in an intake pipe. In the fuel injection control system to be restricted, an engine intake system failure detection device that sets a condition so as to limit the abnormality determination so that an erroneous determination of the intake system failure is not made at the time of starting and that can ensure high detectability is provided. It is something to offer.

[Means for Solving the Problems]

For this reason, in the present invention, as the first means, at the time of engine start or for a certain period from the engine start, the abnormality determination of the intake system is performed for at least one of the above parameters or the determination value obtained by the above parameters. An abnormality determination restricting means for setting a predetermined fixed value that is not performed is provided. Further, in the present invention, as the second means, at the time of engine start or for a certain period of time after the engine start, abnormality determination of the intake system is not performed for at least one of the above parameters or the determination value obtained by the above parameters. There is provided an abnormality determination restricting means for applying an uncorrected correction.

[Action]

Therefore, when starting the engine, a condition is set for the judgment value or a parameter for setting the judgment value so as not to cause an erroneous judgment. No high detectability can be ensured.

【Example】

Hereinafter, an embodiment of the present invention will be specifically described with reference to the drawings. FIG. 1 is a block diagram for explaining the principle of an intake system failure detecting device according to the present invention. In FIG. 1, reference numeral 1 denotes an engine, and one side of a cylinder of the engine detects the temperature of cooling water. A water temperature sensor 2 is provided. Further, an injector 3 is provided at a stage preceding the intake port of the engine 1, and a throttle opening sensor 5 is provided at a position of the throttle valve 4. Further, an air passage 6 is provided in parallel with the throttle valve 4, and an idle speed control valve (hereinafter referred to as an ISC valve) 7 is provided here. The opening of the ISC valve 7 is controlled by a signal from the electronic control unit 8. In the figure, reference numeral 9 denotes a crank angle sensor, 10 denotes an intake air temperature sensor provided downstream of the throttle valve 4, 11 denotes an air cleaner, 12 denotes a pressure sensor provided downstream of the throttle valve 4 for detecting pressure in an intake pipe, 13 Is an O ₂ sensor provided in the exhaust system. The electronic control unit 8 can constitute a logic circuit as shown in FIG. 2 as a part of the electronic control. The electronic control unit 8 realizes program control as shown in the flowchart of FIG. A failure of the intake system is detected based on signals from the angle sensor 9 and the pressure sensor 12, and a necessary fail-safe operation such as fuel cut is performed. Here, the engine speed Ne is obtained from the output of the crank angle sensor 9 by the engine speed calculating means 81, and the throttle opening degree is obtained from the throttle opening degree sensor 5.
THR * is required. In this embodiment, there is an air passage 6 which bypasses in parallel with the throttle valve 4, so that the ISC
Since the air is introduced into the intake system by opening the valve 7, it is necessary to correct the throttle opening THR * in consideration of the increment. Therefore, the electronic control unit 8 calculates the ISC valve opening degree from the signals of the engine speed (crank angle sensor 9), the water temperature sensor 2, and the throttle opening degree sensor under the condition that the engine operation state is determined to be idling. Means 80
Thus, an opening control signal is given to the ISC valve 7.
Since a duty solenoid valve is used for the ISC valve 7, the electronic control unit 8 outputs a control signal at a valve drive duty ratio. At the same time, IS
The value SQ of the opening sectional area of the C valve 7 is calculated by the ISC valve opening sectional area calculating means 82 in a form corresponding to the valve driving duty ratio. Then, the electronic control unit 8
Is prepared in advance in the ROM a two-dimensional map using the above SQ value and the throttle opening THR * as parameters, and when the SQ value is given to the throttle opening conversion means 83, the throttle opening THR * And the throttle opening conversion value corresponding to the SQ value is extracted from the above map, and the corrected throttle opening THR = f (THR *, SQ) is calculated by interpolation calculation. The throttle opening THR and the engine speed Ne corrected in this way are introduced into the determination pressure calculating means 84. The electronic control unit 8 prepares a two-dimensional map (see FIG. 4) in which the determination value of the suction pipe internal pressure is determined in advance using the throttle opening degree THR and the engine speed Ne as parameters, and stores the map in the ROM. In the means 84, based on the throttle opening THR and the engine speed Ne, the corresponding determination value of the suction pipe internal pressure is obtained from the above map, and the determination pressure PMF = f (Ne, THR) is calculated by interpolation calculation. On the other hand, the output signal of the rotation speed calculating means 81 is a starting time discriminating means.
The start control signal is output to the engine 85 when the engine is started or for a certain period of time after the engine is started. Then, the comparing means 86 compares the determination pressure PMF with the suction pipe pressure PM detected by the pressure sensor 12. As a result, if the determination pressure PMF is larger than the suction pipe internal pressure PM, it is determined that the intake system is normal, but if the determination pressure PMF is smaller, it is determined that the intake system has failed, and a failure such as a fuel cut has occurred. Outputs the judgment output for performing safe. This determination output is supplied to abnormality determination limiting means 87,
On the other hand, the above-described start determination signal is also supplied to the abnormality determination limiting means 87. The abnormality determination restricting means 87 is configured in the form of an AND gate in this embodiment, and the start determination signal is at a low level at the time of engine start or for a certain period of time after engine start, and in other engine drive states. High level. The determination output is at a high level at the time of the failure determination of the intake type. For this reason, even if the failure is determined by the comparing means 86 at the start of the engine or for a certain period of time from the start of the engine (this is set in consideration of the time until the pressure in the intake pipe reaches a normal value), As a result, the result of prohibiting the judgment output as a possibility of erroneous judgment at the time of starting is obtained. Such a failure detection function of the intake system can be realized by a built-in program in the electronic control unit 8 according to a flowchart shown in FIG. Here, in step S101, the engine speed Ne is calculated, and at step S102, a determination at the time of starting / after starting is performed.
A selection is made as to whether to proceed to step S106. If it is a start, the process proceeds to step S106. If it is not a start, in step S104, the determination pressure PMF is calculated as PMF = f (Ne, THR). Next, in step S105, the suction pipe pressure PM and the determination pressure
Compare with PMF. In this case, if PMF> PM, it is determined that the intake system has no failure, and the process proceeds to step S106.
If <PM, it is determined that the intake system has failed, and the routine goes to Step S107. Then, in step S106, the flag XFAIN is cleared as the determination output signal, but in step S107, the flag XFAIN is set. In the above embodiment, the judgment pressure is calculated by extracting the judgment value from the map by the judgment pressure calculating means 84 [Step S1
Although the determination pressure MPF = f (Ne, THR) in 04, the throttle opening determination value is obtained for the suction pipe pressure and the engine speed X and Y axes, and the throttle opening determination value TH is calculated by interpolation calculation.
RF is calculated, and the comparison means 86 calculates the actual throttle opening THR.
(THRF <THR in step S105). Further, a determination value of the engine speed is obtained by taking the suction pipe pressure and the throttle opening as the X and Y axes, the engine speed Nef is calculated by interpolation calculation, and the comparison means 86 compares the engine speed Nef with the actual engine speed Ne. Nef> Ne) may be performed in step S105. On the other hand, FIG. 5 is a block diagram showing an embodiment of the intake system failure detecting device according to the first aspect of the present invention. In FIG. During the period, at least one of the three parameters of the throttle opening, the engine speed, and the pressure in the suction pipe, or at least one of the determination values obtained by the above parameters.
By setting a predetermined value at which no abnormality is determined for the intake system, it is possible to prevent the failure of the intake system from being substantially determined until the intake pipe pressure reaches a normal value. ing. That is, in this embodiment, when the start-time determination means 85 determines that the engine is being started,
The output signal of the pressure sensor 12 to be given to the comparison means 86 (here, the judgment value of the suction pipe pressure in the judgment pressure calculation means 84, that is, the judgment pressure, is obtained. However, as described above, when the determination value of the throttle opening or the determination value of the engine speed is extracted from the map and interpolated and calculated as THRF or Nef, respectively, the sensor output becomes Instead of the output signal from the throttle opening sensor 5 or the crank angle sensor 9), the signal switching means 88 is driven in order to set a predetermined constant value. In this embodiment, a mode is shown in which a constant value is set at the start of the engine for the pressure in the suction pipe, which is one of the three parameters, but a constant value is used instead of the determination value obtained by the determination pressure calculating means 84. Set a value and compare it with 86
And a comparison may be made as a sensor output. This makes it possible to set the condition for abnormality determination so that, for example, PMF ≧ PM is always ensured when the engine is started. In the flowchart shown in FIG.
When it is determined in S103 that it is the time of starting, a step S201 of substituting a PMF costant for a determination value obtained based on three parameters, for example, a determination pressure PMF of the suction pipe pressure, is provided. As a result, in the next step S105, PMF> PM
When the determination is made, the condition for moving to step S106 can be always set. FIG. 7 is a block diagram showing an embodiment of the intake system failure detecting device according to the second aspect of the present invention.
The abnormality determination restricting means 87 determines whether at least one of the three parameters of the throttle opening, the engine speed, and the suction pipe pressure, or at least one of the determination values obtained from the above parameters, at the time of starting the engine or for a certain period of time after the engine starts. By performing the correction in this way, it is possible to substantially prevent the failure determination of the intake system from being performed until the pressure in the suction pipe reaches a normal value. That is, in this embodiment, when it is determined by the start-time determination means 85 that the engine is being started,
The output signal THR of the throttle opening sensor 5 given to the judgment pressure calculating means 84 (here, the judgment value of the suction pipe pressure in the judgment pressure calculating means 84, ie, the judgment pressure is the engine speed and the throttle opening are the X and Y axes. And a correction value output means for adding a constant value THR constant to the output value of the throttle opening degree sensor 5 due to the extraction of the determination value from the map to be obtained and the interpolation calculation thereof. 89
And a THR constant is given to the adding means 90, where THR ← THR + THR constant is added, and this is determined as a corrected throttle opening degree THR.
To give to. The signal to be corrected may be one or two of the three parameters (throttle opening, engine speed, and suction pipe pressure) used for the X and Y axes of the map. I just need. In the above embodiment, the abnormality determination restricting means is configured to correct one of the parameters before obtaining the determination value, but may be configured to correct the determination value itself. Further, a configuration may be adopted in which correction is performed on the actually measured sensor output compared with the determination value by the comparing unit 86. In the flowchart shown in FIG.
When it is determined in S103 that the engine is to be started, a step S301 of substituting one of three parameters, for example, the throttle opening THR = THR + THR constant as in the embodiment of FIG. 7, is provided. Accordingly, when the PMF is calculated in the next step S105, a condition is made for the calculated value PMF = f (Ne, THR), and when the process proceeds to step S105, PMF> P
The value M can be taken.

【The invention's effect】

The present invention has been described in detail above. At the time of starting the engine or for a certain period of time after the start of the engine, at least three parameters of the throttle opening, the engine speed, and the pressure in the suction pipe or the determination values obtained by the above parameters are used. At least one of them is set to a predetermined constant value at which the abnormality determination of the intake system is not performed, or is corrected so that the erroneous determination of the intake system failure is not performed at the time of starting.
Since the conditions are set so as to limit the abnormality determination, high detectability can be maintained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an engine control system to which an intake system failure detecting device according to the present invention is applied, FIG. 2 is a block diagram showing a function for detecting an intake system failure in an electronic control unit, and FIG. FIG. 4 is a flowchart of control for realizing the function, and FIG.
FIG. 5 is a three-dimensional diagram of a two-dimensional map for obtaining a determination value of the suction pipe internal pressure as the X and Y axes, and FIG. 5 is a block diagram for explaining a main configuration of an intake system failure detection device according to the first embodiment;
FIG. 6 is a flow chart corresponding to FIG. 5, FIG. 7 is a block diagram for explaining a main configuration of the intake system failure detecting device according to the second aspect of the present invention, and FIG. 8 corresponds to FIG. FIG. DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Water temperature sensor, 3 ... Injector, 4 ... Throttle valve, 5 ... Throttle opening sensor, 6 ... Air passage, 7 ... ISC valve, 8 ... Electronic control unit, 9 …… Crank angle sensor, 10 …… Intake air temperature sensor, 11 …… Air cleaner, 12 …… Pressure sensor, 13…
... O sensor, 81 ... rotation speed calculation means, 82 ... ISC valve opening cross-sectional area calculation means, 83 ... throttle opening degree conversion means, 84 ... judgment pressure calculation means, 85 ... start time discrimination means,
86... Comparison means, 87...

Continuation of the front page (56) References JP-A-58-214632 (JP, A) JP-A-58-15738 (JP, A) JP-A-59-28048 (JP, A) JP-A-60-11657 (JP) JP-A-57-51936 (JP, A) JP-A-56-167746 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) F02D 41/00-41/40 F02D 45/00 301-395

Claims (2)

(57) [Claims] 1. A fuel injection control system for detecting an abnormality of an intake system based on at least three parameters of a throttle opening, an engine speed, and a pressure in an intake pipe, and restricting a fuel injection amount when the abnormality is detected. An abnormality determination limit for setting a predetermined constant value at which at least one of the above parameters or the determination values obtained from the above parameters is not determined to be an abnormality in the intake system at the time of engine start or for a certain period of time after the engine start. An intake system failure detection device for an engine, characterized by comprising means. 2. A fuel injection control system for detecting an abnormality in an intake system based on at least three parameters of a throttle opening, an engine speed, and a pressure in an intake pipe, and restricting a fuel injection amount when the abnormality is detected. At least one of the above parameters or a determination value obtained by the above parameters is provided with abnormality determination limiting means for making a correction such that an abnormality determination of the intake system is not made at the time of starting the engine or for a predetermined time from the start of the engine. An intake system failure detection device for an engine, characterized in that: