JP4118403B2 - Fail-safe control device for electric throttle type internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an internal combustion engine having an electric throttle system that opens and closes a throttle valve interposed in an intake system with an actuator so as to reach a target opening, and in particular, includes two accelerator opening sensors and two throttle opening sensors. The present invention relates to a fail-safe control technique when one sensor fails in a system that selects and uses one of the detected values.
[0002]
[Prior art]
Conventionally, there is an electric throttle system that electronically controls the opening of a throttle valve so that a target air amount can be obtained based on the accelerator opening (accelerator pedal depression amount) or the engine rotation speed, etc. No. 180570).
Among such electronically controlled throttle systems, especially those that do not have a fail-safe mechanism that mechanically interlocks the throttle valve with a wire or the like by accelerator operation when the drive system fails (full electric throttle system), for example, The method like this is adopted. There are two accelerator opening sensors and two throttle opening sensors. For the accelerator opening, select the smaller one of the two detection values (to prevent excessive output), and for the throttle valve opening, The detected value of the main throttle opening is used, and the larger one of the two detected values is selected in some cases (the output is excessive by correcting the smaller one by selecting the larger one for feedback control) To prevent).
[0003]
[Problems to be solved by the invention]
By the way, in the fail-safe method in such a full electric control throttle system, if one sensor fails (hereinafter referred to as a single failure), the detection value of only the remaining one sensor must be used, Since the guarantee due to double installation is lost, at least the engine output will prevent the situation that the vehicle speed will increase more than required, and control to keep the required minimum speed, for example, maximum speed of about 40 km ( Limp home control) is required.
[0004]
The present invention has been made paying attention to such a conventional problem, and provides a fail-safe control device for an electric throttle type internal combustion engine capable of ensuring limp home control in the event of a single sensor failure. Objective.
[0005]
[Means for Solving the Problems]
For this reason, as shown in FIG.
According to engine operating conditions including the accelerator opening, an throttle opening that opens and closes the throttle valve installed in the intake system with an actuator so as to reach the target opening, and detects the accelerator opening In an electric throttle type internal combustion engine having two sensors and two throttle opening sensors for detecting the opening of the throttle valve ,
Diagnose the accelerator opening sensor and the throttle opening sensor,
When both of the accelerator opening sensors are normal, the smaller one of the detection values of the two sensors is selected, and when both of the throttle opening sensors are normal Select the detection value of one of the specified sensors,
For the accelerator opening sensor and the throttle opening sensor, when diagnosing that one of the two sensors is malfunctioning, select the detection value of the sensor not diagnosed as malfunctioning,
When diagnosing that at least one of the two sensors is out of order with respect to the accelerator opening sensor and the throttle opening sensor,
The accelerator opening detected by the sensor selected for the accelerator opening sensor;
Upper limit,
With respect to the detected accelerator opening, the accelerator opening that has been processed to limit the increase rate of change to a value equal to or less than the upper limit change rate;
The output characteristic limiting means for selecting and using the smallest value is included.
[0006]
According to such a configuration, when one of the two sensors, the accelerator opening sensor and the throttle opening sensor, fails, the detected value of the remaining sensor is used, but is selected by the output characteristic limiting means. Because the output characteristics of the accelerator position sensor are limited, the limp home is controlled by controlling the throttle valve position according to the limited accelerator position characteristics, while suppressing rapid acceleration and suppressing increase in absolute speed. Control can be performed.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 2 shows a system configuration of an embodiment of the present invention.
Two accelerator opening sensors (APS) 1A and 1B detect the amount of accelerator pedal depression (accelerator opening) depressed by the driver.
[0013]
The crank angle sensor 2 generates a position signal for each unit crank angle and a reference signal for each cylinder stroke phase difference, and measures the number of occurrences of the position signal per unit time or measures the reference signal generation cycle. By doing so, the engine speed can be detected.
The air flow meter 3 detects the amount of intake air to the engine 4 (intake air amount per unit time = intake air flow rate).
[0014]
The water temperature sensor 5 detects the cooling water temperature of the engine.
The engine 4 is provided with a fuel injection valve 6 that is driven by a fuel injection signal to inject fuel directly into the combustion chamber, and an ignition plug 7 that is attached to the combustion chamber and ignites. By direct injection into the combustion chamber, leaning by stratified combustion becomes possible, and the air-fuel ratio can be variably controlled over a wide range.
[0015]
A throttle valve 9 is interposed in the intake passage 8 of the engine 4, and an actuator 10 capable of electronically controlling the opening degree of the throttle valve 9 is provided. The throttle valve 9 is provided with two throttle opening sensors 11A and 11B for detecting the opening of the throttle valve 9.
The exhaust passage 12 is provided with an air-fuel ratio sensor 13 as air-fuel ratio detection means for detecting the air-fuel ratio of the combustion mixture by detecting the concentration of a specific component in the exhaust, for example, oxygen.
[0016]
Detection signals from the various sensors are input to the control unit 14, and the control unit 14 drives the actuator 11 in accordance with the operation state detected based on the signals from the sensors to control the throttle valve 9. The fuel injection valve 6 is driven to control the fuel injection amount (fuel supply amount), the ignition timing is set, and the ignition plug 7 is ignited at the ignition timing.
[0017]
Next, failure diagnosis of the accelerator opening sensors 1A and 1B and the throttle opening sensors 11A and 11B and fail-safe control at the time of failure (limp home control) will be described with reference to FIG.
In the figure, the accelerator opening sensor system diagnosis will be described. In the output diagnosis of the accelerator opening sensors 1A and 1B, open / short failure detection is performed, and flags APS1CA and APS2CA are set to 1 when a failure occurs. In order to remove a malfunction, the flags APS1NG and APS2NG are set to 1 when the malfunction state continues for a predetermined delay time, and the malfunction of the accelerator opening sensors 1A and 1B is determined. When each flag (including a flag to be described later) is set to 1, the output to each circuit described later is at a high level. When the flag is reset to 0, the output to each circuit is at a low level. It is set to be.
[0018]
In addition, a diagnosis is made whether the difference between the accelerator opening sensors 1A and 1B is large or inconsistent (APS inconsistency diagnosis), and the flag APSXCA is set to 1 when there is a mismatch. In order to remove the inconsistency, the flag APSXNG is set to 1 when the inconsistency state continues for a predetermined delay time, and the inconsistency is determined.
[0019]
On the other hand, the throttle opening sensor system diagnosis is the same as that of the accelerator opening sensor system diagnosis. That is, open / short failure detection of the throttle opening sensors 11A and 11B is performed, and when the failure occurs, the flags TPS1CA and TPS2CA are set to 1. When the failure state continues for a predetermined delay time, the flags TPS1NG and TPS2NG 1 is set, the failure of the throttle opening sensors 11A and 11B is determined, and when the difference between the throttle opening sensors 11A and 11B is largely inconsistent, the flag TPSXCA is set to 1 and the inconsistent state Is set to 1 when a predetermined delay time continues, and it is determined that there is a mismatch.
[0020]
For the accelerator position sensor system, when all three flags APS1NG, APS2NG, APSXNG are 0 (first from the top of the table of the same system), that is, when the diagnosis results of the accelerator position sensor system are all normal The smaller one of the two detected values of the accelerator opening sensors 1A and 1B is selected (LOWER). For the throttle opening sensor system, when the three flags TPS1NG, TPS2NG, and TPSXNG are all 0 (first from the top of the table of the same system), the detection value TPO1 of one throttle opening sensor 14A is selected. To do.
[0021]
When all the systems are diagnosed as normal, there is no need for limp home, so the limp home permission flag at the time of single sensor failure is set to 0. Therefore, when both systems are normal, the actuator 11 is driven, and the opening of the throttle valve 9 is controlled so as to reach the target throttle opening set based on the smaller accelerator opening APO. Is done. In this case, since the output of the first OR circuit 31 is maintained at a low level, the warning lamp is not lit.
[0022]
Further, when only the mismatch flag APSXCA (TPSXCA) is set to 1 for at least one system (second in the table of each system), any of the accelerator opening sensors 1A, 1B (throttle opening sensors) 14A, 14B) is also determined to be unreliable, and the first OR circuit 31 becomes high level and the warning lamp is lit as shown in FIG. 32. Is driven and the opening of the throttle valve 9 is controlled so as to be the target throttle opening set based on the smaller accelerator opening APO. As described below, when at least one of the six flags APS1NG, APS2NG, APSXNG, TPS1NG, TPS2NG, and TPSXNG is 1, the first OR circuit 31 is at a high level and the warning light is turned on. Therefore, the description is omitted below.
[0023]
Next, for each system, one of the flags APS1NG, APS2NG (TPS1NG, TPS2NG) is 1, that is, only one of the accelerator opening sensors 1A, 1B (throttle opening sensors 11A, 11B) is diagnosed as a failure (single failure). In the case where it is set (third to sixth in the table of each system), the limp home permission flag at the time of single sensor failure is set to 1, and the accelerator opening APO (throttle opening TPO) is diagnosed as a failure. The detected value on the non-existing side, APS1 or APS2 (TPO1 or TPO2), is selected, but the accelerator opening degree is limited as described below according to the present invention.
[0024]
That is, when the accelerator opening sensors 1A and 1B or the throttle opening sensors 11A and 11B have a single failure, the output of the second OR circuit 33 is at a high level and two kinds of restrictions are applied to the output characteristics of the accelerator opening (illustrated). 34) One limits the absolute value of the accelerator opening with the upper limit value, and the other limits the increase change rate of the accelerator opening with the upper limit change rate. Specifically, as shown in FIG. 4A, although the upper limit value (APO limiter) and the upper limit change rate (ΔAPO limiter) are set even in the normal state, each is set to a sufficiently large value, and the normal accelerator In the operation, the value is set to a value that is not substantially limited, while the upper limit value (APO limiter) and the upper limit change rate (ΔAPO limiter) at the time of a single failure are set to small values. In the case of a single failure, the upper limit value (APO limiter) and the upper limit change rate (ΔAPO limiter) are each switched to a small value, as indicated by 35 and 36 in the figure.
[0025]
The upper limit change rate is set as the upper limit value of the change amount of the accelerator opening per unit time, and the increase change rate, that is, the increase change amount of the accelerator opening detected this time from the previous accelerator opening before the unit time. A ΔAPO limiter process (37 in the figure) is performed in which ΔAPO is compared with the upper limit change rate (ΔAPO limiter) and the smaller one is selected. Thereby, the increase change rate of the accelerator opening is limited to a value equal to or less than the upper limit change rate.
[0026]
The detected value APO of the selected one of the accelerator opening sensors 1A and 1B and the detected value of the sensor that has not been diagnosed at the time of a single failure of the accelerator opening sensor are selected. The upper limit value (APO limiter) and the accelerator opening degree processed by the ΔAPO limiter are input to the select low circuit 38, and the smallest accelerator opening degree is selected and used.
[0027]
In this way, the absolute value of the accelerator opening is limited by the upper limit value (APO limiter) and the increase rate of change is also the upper limit change rate (ΔAPO limiter), as shown by the thick solid line in FIG. Therefore, by controlling the throttle valve opening according to the limited accelerator opening characteristic, it is possible to perform limp home control while suppressing rapid acceleration and suppressing increase in absolute speed.
[0028]
Further, simply, an embodiment in which only the absolute value of the accelerator opening is limited by the upper limit value, or only the increase change rate is limited by the upper limit change rate may be used.
If two accelerator opening sensors 1A and 1B (throttle opening sensors 14A and 14B) are out of order, normal throttle opening control cannot be expected. The valve 9 is held at a predetermined default opening by a balance between a return spring and a default spring.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration / function of the present invention.
FIG. 2 is a diagram showing a system configuration of an embodiment of the present invention.
FIG. 3 is a circuit block diagram showing throttle control by diagnosis of an accelerator opening sensor and a throttle opening sensor according to the embodiment.
FIG. 4 is a diagram showing the accelerator opening output characteristics when the accelerator opening sensor and the throttle opening sensor are normal, and the accelerator opening output characteristics when a single failure occurs.
[Explanation of symbols]
1A, 1B Accelerator opening sensor 4 Engine 9 Throttle valve 10 Actuator 11A, 11B Throttle opening sensor 14 Control unit

Claims (1)

According to engine operating conditions including the accelerator opening, an throttle opening that opens and closes the throttle valve installed in the intake system with an actuator so as to reach the target opening, and detects the accelerator opening In an electric throttle type internal combustion engine having two sensors and two throttle opening sensors for detecting the opening of the throttle valve ,
Diagnose the accelerator opening sensor and the throttle opening sensor,
When both of the accelerator opening sensors are normal, the smaller one of the detection values of the two sensors is selected, and when both of the throttle opening sensors are normal Select the detection value of one of the specified sensors,
For the accelerator opening sensor and the throttle opening sensor, when diagnosing that one of the two sensors is malfunctioning, select the detection value of the sensor not diagnosed as malfunctioning,
When diagnosing that at least one of the two sensors is out of order with respect to the accelerator opening sensor and the throttle opening sensor,
The accelerator opening detected by the sensor selected for the accelerator opening sensor;
Upper limit,
With respect to the detected accelerator opening, the accelerator opening that has been processed to limit the increase rate of change to a value equal to or less than the upper limit change rate;
A fail-safe control device for an electric throttle type internal combustion engine, characterized in that it comprises output characteristic limiting means for selecting and using the smallest value among them .

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