JP6133684B2 - Fault diagnosis device - Google Patents

Description

  The present invention relates to a failure diagnosis apparatus.

  2. Description of the Related Art Conventionally, there has been known a failure diagnosis apparatus that includes two microcomputers (hereinafter simply referred to as “microcomputers”) of a main control unit and a monitoring unit and diagnoses a failure of an internal combustion engine to be monitored using these two microcomputers. (For example, refer to Patent Document 1).

  The main control unit, which is one microcomputer, calculates an engine control amount related to driving of the internal combustion engine and the like, and executes engine control based on the calculation result. The monitoring unit, which is the other microcomputer, performs the same engine control amount calculation as that for the main control unit simultaneously for monitoring, and the calculation result of the engine control amount calculated by the main control unit with the calculation result of the monitoring engine control amount A failure of the internal combustion engine is diagnosed by comparison.

JP 2012-180780 A

  However, in the conventional failure diagnosis apparatus as described above, two microcomputers are used and the same calculation is always performed for control and monitoring. Therefore, the monitoring microcomputer is subjected to the same calculation load as the control microcomputer, and the monitoring microcomputer is required to have the same calculation performance as the control microcomputer, which increases the cost for monitoring. There was a problem.

  In addition, the reliability of the fault diagnosis result is simply determined by simply omitting some of the control calculation elements in the monitoring unit simply because the calculation load is high by performing the same calculation as the control unit in the monitoring unit. Will fall.

  The present invention has been made in order to solve the above-described conventional problems. The reliability of the diagnostic result is reduced while reducing the calculation load when performing the two-system calculation for the monitoring target and for the monitoring. It is an object of the present invention to provide a failure diagnosis device that can ensure the above.

  In order to achieve the above object, the failure diagnosis apparatus according to the present invention includes (1) a main control unit that calculates a control amount by combining a plurality of control calculation elements, and a plurality of control calculation elements used in the main control unit. The same control calculation as that of some of the control calculation elements is performed, and the remaining control calculation elements of the plurality of control calculation elements are set in advance with respect to values calculated by the control calculation elements on the main control unit. And a monitoring unit that calculates a control amount for monitoring using the value limited by the guard value in the predetermined range as the calculation value of the remaining control calculation elements.

  With this configuration, the main control unit calculates a control amount by combining a plurality of control calculation elements. The monitoring unit performs control calculations similar to some of the control calculation elements used in the main control unit, and the remaining control calculation elements are values calculated by the control calculation elements on the main control unit. In contrast, a value limited by a preset guard value within a predetermined range is used as a calculation value for the remaining control calculation elements, and a control amount for monitoring is calculated using each of these elements.

  At this time, the monitoring unit does not use all of the plurality of control calculation elements used in the main control unit as they are, some of the control calculation elements are left as they are, and the remaining control calculation elements are limited by a guard value within a predetermined range. The control amount for monitoring is calculated using the value.

  As a result, the reliability of the diagnosis result can be ensured while reducing the calculation load when performing the two systems of control and monitoring for the monitoring target.

  The failure diagnosis apparatus according to the present invention is the failure diagnosis apparatus according to (1), wherein (2) the control amount calculated by the main control unit is compared with the monitoring control amount calculated by the monitoring unit. In addition, the control unit is configured to include a comparison unit that determines that the monitoring target has failed on the condition that the value of the control amount calculated by the main control unit is larger than the value of the monitoring control amount.

  With this configuration, the calculation result of the main control unit and the calculation result of the monitoring unit are compared, and if the value of the control amount calculated by the main control unit is larger than the value of the control amount for monitoring, the monitoring target is faulty. It can be determined that there is.

  The failure diagnosis device according to the present invention is the failure diagnosis device according to the above (1) or (2), further comprising: (3) a valve control unit that adjusts an intake air amount of the internal combustion engine; A control calculation element for adjusting the intake air amount by the valve control unit is used as the plurality of control calculation elements.

  With this configuration, when a failure occurs in the internal combustion engine, it is possible to cope with the failure of the internal combustion engine by adjusting the intake air amount for driving the internal combustion engine.

  Further, the failure diagnosis apparatus according to the present invention is the failure diagnosis apparatus according to (3), further comprising: (4) an ISC control unit that feedback-controls an intake air amount when the internal combustion engine is idling, and the ISC control unit Calculates a correction value using the remaining control calculation elements of the plurality of control calculation elements, and the monitoring unit takes the control value set in advance for the correction value calculated by the ISC control unit. A correction value not deviating from the maximum obtained upper limit guard value is used as the remaining control calculation element.

  With this configuration, the control calculation element calculated by the main control unit and the control calculation element calculated by the monitoring unit can be easily made the same, and the reliability of the calculation result can be improved.

  According to the present invention, it is possible to provide a failure diagnosis apparatus capable of ensuring the reliability of a diagnosis result while reducing the calculation load when performing two systems of control and monitoring for a monitoring target. .

1 is a schematic block configuration diagram of a failure diagnosis apparatus according to a first embodiment of the present invention.

  Hereinafter, a failure diagnosis apparatus according to an embodiment of the present invention will be described with reference to the drawings.

First, the configuration will be described.
As shown in FIG. 1, the failure diagnosis apparatus 1 of the present embodiment has a main control unit 10 that calculates a control amount by combining a plurality of control calculation elements. In addition, the failure diagnosis apparatus 1 includes a monitoring unit 20 that calculates a control amount for monitoring separately from the main control unit 10. The monitoring unit 20 performs the same control calculation as some of the control calculation elements used in the main control unit 10. Further, the monitoring unit 20 is configured such that the remaining control calculation elements of the plurality of control calculation elements used in the main control unit 10 are predetermined ranges set in advance with respect to values calculated by the control calculation elements on the main control unit 10. The engine control amount for monitoring is calculated using the value limited by the guard value as a calculation value.

  Specifically, the monitoring unit 20 includes a comparison unit 23 that compares the control amount calculated by the main control unit 10 with the monitoring control amount calculated by the monitoring unit 20. The comparison unit 23 determines that the monitoring target has failed on the condition that the value of the control amount is larger than the value of the control amount for monitoring.

  Here, the monitoring object applied to the present invention is applied to the engine 2 which is an internal combustion engine, and the configuration of the engine 2 will be described first. In FIG. 1, the overall view of the engine 2 is omitted, and only the main part is schematically shown. In FIG. 1, an engine 2 discharges from the combustion unit 50 a combustion unit 50 composed of a plurality of cylinders, an intake unit 60 that supplies a gas such as air to the combustion unit 50, and exhaust gas generated by combustion in the combustion unit 50. And an exhaust part 70 to be operated.

  Note that, for example, the combustion unit 50 illustrates only one cylinder among four cylinders adjacent to each other along the depth direction orthogonal to the paper surface of FIG. 1. The engine 2 is not limited to four cylinders, and may be constituted by a single cylinder or a multi-cylinder arranged arbitrarily.

  The combustion unit 50 includes a cylinder block 51 and a cylinder head 52 fixed to the upper part of the cylinder block 51. The cylinder block 51 and the cylinder head 52 form a space inside, and house the piston 53 so as to be able to reciprocate in this space. The piston 53 has a rod 54 whose upper end is connected. By connecting the lower end of the rod 54 to a link mechanism (not shown), the linear motion due to the reciprocating motion of the piston 53 is converted into the rotational motion of the crankshaft. The cylinder block 51, the cylinder head 52, and the piston 53 form a combustion chamber 55 above the piston 53 in the above-described space.

  In the cylinder block 51, cooling water flows, and a water jacket 56 for cooling the cylinder block 51 due to a temperature difference between the cooling water and the cylinder block 51 is formed.

  The cylinder head 52 includes an intake valve 57A, an exhaust valve 57B, and an ignition plug 58 for igniting the air-fuel mixture introduced into the combustion chamber 55. The cylinder block 51 also has a water temperature sensor 59 for detecting the temperature of the cooling water flowing through the water jacket 56.

  The intake valve 57A introduces a gas such as air taken in by the intake section 60 into the combustion chamber 55 as an air-fuel mixture. The exhaust valve 57B discharges exhaust gas from the combustion chamber 55 to the exhaust part 70. The intake valve 57A and the exhaust valve 57B are connected to a crankshaft via a timing belt (not shown), and the combustion chamber 55 is opened and closed at a desired timing as the crankshaft rotates.

  The spark plug 58 has an electrode formed of platinum or an iridium alloy. The spark plug 58 ignites the air-fuel mixture introduced into the combustion chamber 55 by energizing the electrode at a desired timing to generate a discharge.

  The water temperature sensor 59 is constituted by a thermistor whose resistance value changes according to temperature, for example. The water temperature sensor 59 outputs a change in the resistance value of the thermistor according to the temperature of the cooling water for cooling the engine 2 as a voltage change amount.

  The intake section 60 introduces gas such as air that has passed through an air cleaner (not shown) and entered from the outside of the vehicle into the combustion chamber 55. The intake pipe 61 has a throttle valve 62 on the downstream side of the air cleaner. The intake pipe 61 communicates with the combustion chamber 55 by connecting the tip to the cylinder head 52.

  The throttle valve 62 has a throttle motor 63 that is an actuator for driving the throttle valve 62 at one end of the valve shaft. The throttle valve 62 has a throttle opening sensor 64 for detecting the opening of the throttle valve 62 at the other end of the valve shaft. The throttle valve 62 in this embodiment is an electronically controlled throttle that is opened and closed by a throttle motor 63.

  The throttle valve 62 has a valve shaft in the center of a thin disc-shaped valve body, and the valve body is also rotated by rotating the valve shaft by the throttle motor 63, whereby the gas flow rate in the intake pipe 61 is increased. Is supposed to change. The throttle opening sensor 64 detects the opening of the throttle valve 62.

  The intake pipe 61 forms a surge tank 65 on the downstream side of the throttle valve 62. The surge tank 65 is provided with a pressure sensor 66 for detecting the internal intake pressure.

  An injector 67 that injects fuel into air or the like passing through the intake pipe 61 is disposed near the tip of the intake pipe 61. The injector 67 may be disposed in the cylinder block 51. The injector 67 introduces an air-fuel mixture generated by injecting fuel into air or the like passing through the intake pipe 61 into the combustion chamber 55.

  The exhaust unit 70 includes an exhaust pipe 71 that communicates with the combustion chamber 55 via an exhaust valve 57B, and an O2 sensor 72 that is a kind of an air-fuel ratio sensor that detects the concentration of exhaust gas. The O2 sensor 72 is disposed upstream of a three-way catalytic converter (not shown) that simultaneously purifies three harmful components HC, CO, and NOx in the exhaust gas exhausted by the exhaust pipe 71, and the exhaust gas An electric signal is generated in accordance with the concentration of oxygen component therein.

  In addition, the structure of the engine 2 mentioned above is an example, and is not limited to the structure mentioned above. In the present embodiment, the main control unit 10 and the monitoring unit 20 are configured by an engine control unit (hereinafter simply referred to as “engine ECU”) 3 using a single microcomputer.

  Although not shown, the engine ECU 3 has, for example, an input / output interface for signal input from various sensors and a drive control signal output for the engine 2, a CPU that performs arithmetic processing, a ROM that stores a control program for the engine 2, and the like. These are connected to each other by a bus.

  Since the configuration and operation of the engine ECU 3 are known, further description is omitted except for the configuration and operation related to the present invention.

  In the failure diagnosis apparatus 1, the main control unit 10 includes a required torque calculation unit 11 and a valve control unit 12. The valve control unit 12 controls the drive of the throttle motor 63 based on the calculation result (a) by the required torque calculation unit 11. Further, when the opening command value of the throttle valve 62 is input to the valve control unit 12 as the calculation result (a), the throttle motor 63 can follow at high speed in response to the command value.

  The requested torque calculation unit 11 receives an accelerator opening signal from an accelerator opening sensor that detects an accelerator opening corresponding to the depression amount of the accelerator pedal 4 in order to calculate the engine control amount. This accelerator opening signal is used for some control calculation elements among the plurality of control calculation elements in the failure diagnosis apparatus 1.

  The required torque calculation unit 11 receives a correction value signal from the ISC control unit 30 that calculates the ISC correction amount used to calculate the engine control amount. The correction value signal from the ISC control unit 30 is used for the remaining control calculation elements of the plurality of control calculation elements in the failure diagnosis apparatus 1.

  The ISC control unit 30 controls the engine speed at idling to be as low as possible in order to suppress wasteful fuel consumption in response to the recent demand for energy saving and exhaust purification performance. The ISC control unit 30 performs control to rapidly raise the temperature of the catalytic converter that exhibits good exhaust purification performance in the activation temperature range at the start.

  For this reason, the ISC controller 30 normally presets the target idle speed as a low speed that can be idling without causing engine stall. The ISC control unit 30 feedback-controls the intake air amount during idling so as to maintain the idle rotational speed at the target idle rotational speed. Thus, by controlling the ignition timing that greatly affects the combustion and exhaust properties of the engine 2 to the retard side during cold start, the exhaust temperature during cold start can be raised, and the catalytic converter can be raised quickly. it can.

  The ISC control unit 30 outputs the calculated correction value to the required torque calculation unit 11 as a control calculation element for calculating the engine control amount. For example, the ISC control unit 30 calculates each correction value based on outputs from the rotation angle sensor 31 and the water temperature sensor 59 that detect the rotation angle of the crankshaft, as well as outputs from the air conditioner device 5 and the alternator 6. It has become.

  The ISC control unit 30 corrects the rotational speed of the engine 2 as one of the control calculation elements. The ISC control unit 30 specifies a correction condition for correcting the ignition timing of the engine 2 with respect to a combustion speed change caused by a change from the basic engine speed to the engine speed. The ISC controller 30 increases the engine speed so that the intake air turbulence increases, and the combustion speed increases according to the engine speed regardless of the torque, air-fuel ratio, and ignition timing of the engine 2. Ignition timing control is performed in consideration of the influence. The ISC control unit 30 stores a map in which a positive rotational speed is determined based on the engine rotational speed and the in-cylinder pressure peak crank angle, and calculates the rotational speed correction value with reference to this map. Yes.

  The ISC control unit 30 corrects the water temperature of the engine 2 which is one of the calculation elements. The ISC control unit 30 ensures stable rotation of the engine 2 while the cooling water temperature of the engine 2 is low. That is, while the cooling water temperature of the engine 2 is low, the friction due to the oil viscosity is large, so that the idling flow rate is increased as compared with the end of warm-up in order to maintain the desired idling speed and stably rotate the engine 2. There is a need to. Therefore, the ISC control unit 30 stores a map in which the water temperature correction value is determined in relation to the cooling water temperature in order to obtain a correction value corresponding to the increased amount, and calculates the water temperature correction value with reference to this map. It is like that.

  The ISC control unit 30 performs air conditioner correction, which is one of the calculation elements. When the driving resistance of the engine 2 increases with the operation of the air conditioner device 5, the ISC control unit 30 ensures stable rotation of the engine 2 according to the driving resistance.

  The ISC control unit 30 increases or decreases the basic air amount necessary for maintaining the target idling engine speed in a stable operation state when the engine is warm, reflecting the difference in conditions between the stable operation state and the current time. The air conditioner correction value is calculated. At this time, the air conditioner correction value is set according to the load state of the air conditioner device 5. For example, the air conditioner correction value includes an air increase necessary for maintaining the target idle speed when the engine is cold, and an air conditioner correction value corresponding to the operation of an accessory device other than the air conditioner device 5. The engine ECU 3 controls the intake air amount to the engine 2 during idling based on the air conditioner correction value.

  For example, if the air conditioner device 5 is in an on state, the ISC control unit 30 calculates an air conditioner correction value from the map based on the actual engine speed. The air conditioner correction value is a correction value for reflecting the load of the air conditioner device 5 on the fuel injection amount to the engine 2 and is adjusted according to the engine speed. Therefore, if the air conditioner device 5 is in the off state, the air conditioner correction value is set to “0”.

  The ISC control unit 30 performs alternator correction, which is one of the control calculation elements. When power generation is performed by the alternator 6 of the engine 2 during idle operation, the ISC control unit 30 ensures stable rotation of the engine 2 according to the driving resistance of the engine 2 associated therewith. When the ISC control unit 30 increases the power generation amount of the alternator 6 that supplies power in accordance with the operation of the on-vehicle electric device, the engine speed is excessively decreased due to the driving load of the engine 2 when obtaining the required power generation amount. The alternator correction value is calculated so as not to occur.

  The monitoring unit 20 includes an upper limit guard determination unit 21 that determines whether or not a predetermined upper limit guard is exceeded for each correction value output from the ISC control unit 30. The monitoring unit 20 includes a monitoring torque calculation unit 22 that calculates a monitoring engine control amount based on an accelerator opening signal from the accelerator opening sensor and a correction value signal that has passed through the upper limit guard determination unit 21. The monitoring unit 20 includes a comparison unit 23. The comparison unit 23 compares the calculation result (a) of the engine control amount by the required torque calculation unit 11 with the calculation result (b) of the monitoring engine control amount by the monitoring torque calculation unit 22.

  The upper limit guard value used in the upper limit guard determination unit 21 is provided corresponding to the setting state at the time of idling such as on / off for each presence / absence and type of an external load of the air conditioner device 5 or the like. Is. At this time, the upper limit guard initial value is set as the upper limit guard value. The upper limit guard initial value is set to such a size that the integral correction term can absorb the friction at the initial stage of engine start.

  As an example of a specific upper limit guard value, the engine ECU 3 uses the map for calculating the water temperature correction value by the ISC control unit 30 to calculate the upper limit guard value based on the water temperature at the time of engine start and the integration. It has become. For example, when the range that the air conditioner correction can take is 0 to 29 Nm, the upper limit guard value is set to 30 Nm. The upper limit guard determination unit 21 performs a guard process by using an upper limit guard value based on the water temperature and integration at the time of starting the engine.

Next, the operation of the present invention will be described.
The present invention includes a valve control unit 12 that adjusts an intake air amount for driving the engine, and an engine ECU 3 that determines a valve opening degree in the valve control unit 12, and the main control unit 10 is based on the valve control unit 12. A control calculation element for determining the opening is used as a plurality of control calculation elements.

  Specifically, it has an ISC control unit 30 that performs feedback control of the intake air amount during engine idling. The ISC control unit 30 calculates a correction value using the remaining control calculation elements among the plurality of control calculation elements, and outputs the correction value to the engine ECU 3. The monitoring unit 20 uses a correction value that does not deviate from the maximum upper limit guard value that can be set in advance for the correction value output from the ISC control unit 30 for the remaining control calculation elements.

  More specifically, in the present invention, the engine control amount is separately calculated by the main control unit 10 and the monitoring unit 20 in order to guarantee the accuracy of the engine control amount by the engine ECU 3. As a result, the actual engine control is executed based on the engine control amount calculation result (a) calculated by the main control unit 10, and the actual engine is calculated based on the monitoring engine control amount calculation result (b) calculated by the monitoring unit 20. The control amount can be monitored.

  At this time, some control calculation elements used in the main control unit 10 are not simply omitted depending on the priority level, but upper limit guards are set on some control calculation elements of the main control unit 10, and the monitoring unit 20 Failure detection is performed when a failure exceeding the upper limit guard value occurs while reducing the computation load.

  That is, the ISC control unit 30 calculates a number of correction amounts such as a rotation speed correction amount, a water temperature correction amount, an air conditioner correction amount, an alternator correction amount, and the like, and the required torque calculation unit 11 of the main control unit 10 and the monitoring unit 20 This is output to the monitoring torque calculator 22. If all of these are calculated by the monitoring unit 20 in the same manner as the main control unit 10, not only will the calculation load increase, but the amount of memory (not shown) used to temporarily store the calculation results of the monitoring unit 20 will also be increased. growing. Therefore, after the upper limit guard is performed on each correction amount calculated by the ISC control unit 30 with the maximum value that can be taken in the control, the calculation load and memory usage can be reduced by reflecting them in the engine control amount for monitoring. .

  Therefore, the comparison unit 23 compares the calculation result (a) with the calculation result (b), and the engine 2 fails on the condition that the value of the calculation result (a) is larger than the value of the calculation result (b). It comes to judge that. When the comparison unit 23 determines that the engine 2 has failed, the comparison unit 23 outputs a failure signal to the valve control unit 12. When receiving the failure signal, the valve control unit 12 sets the intake air to “0”. In addition to outputting a failure signal to the valve control unit 12, the comparison unit 23 may output a failure signal to a drive control unit (not shown) of the injector 67, for example.

  As described above, the main control unit 10 of the failure diagnosis apparatus 1 performs the engine control by calculating the actual engine control amount using the accelerator opening signal and the various control calculation elements corrected by the ISC control unit 30.

  On the other hand, the monitoring unit 20 of the failure diagnosis apparatus 1 uses the accelerator opening signal as it is, and uses various control calculation elements that have passed through the upper limit guard determination unit 21 among the control type calculation elements corrected by the ISC control unit 30. The engine control amount for monitoring is calculated.

  The comparison unit 23 calculates the engine control amount calculation result (a) calculated by the required torque calculation unit 11 of the main control unit 10 and the monitoring engine control amount calculated by the monitoring torque calculation unit 22 of the monitoring unit 20. The calculation result (b) is compared.

  Further, the comparison unit 23 determines that the engine control is abnormal on the condition that the value of the calculation result (a) is larger than the value of the calculation result (b), and executes fail-safe such as output restriction and retreat travel. ing.

  For example, if it is assumed that the rotational speed correction amount is an abnormality and becomes an excessive value than the normal value, the required torque becomes a value larger than the normal value. In the monitoring unit 20, the rotation speed correction amount after the upper limit guard is reflected in the monitoring torque, and thus becomes a value smaller than the required torque. As a result, required torque> monitoring torque and engine control abnormality can be detected.

  By the way, in the above embodiment, the main ECU 10 and the monitoring unit 20 are provided in the engine ECU 3 by one microcomputer, and the engine control amount and the monitoring engine control amount are calculated by the same method. The failure of the engine 2 was diagnosed by comparison.

  In such a case, in order to compare two types of calculation results for control and monitoring, a memory for temporarily storing the calculation results is required, and a large-capacity memory is required. For example, when the calculation result (b) of the monitoring unit 20 includes control calculation elements that exceed the upper limit guard, the upper limit value of the memory capacity must be increased in order to store the calculation result.

  On the other hand, in the failure diagnosis apparatus 1, since the upper limit guard is set for the calculation by the monitoring unit 20, the upper limit of the memory capacity can be suppressed to some extent, and a large capacity memory need not be used. . Therefore, the cost of the memory can be suppressed and it can contribute to the reduction of the component cost.

  When the monitoring target is the engine 2, many correction amounts such as an ISC correction amount and an environmental correction amount exist as control calculation elements in the calculation of the engine control amount. For this reason, if these complicated engine control amount calculations are simultaneously performed by a single microcomputer, the calculation load of the microcomputer increases, and a higher performance microcomputer is required.

  On the other hand, in the fault diagnosis apparatus 1, since the upper limit guard is set for the calculation by one monitoring unit 20, the processing capability of the microcomputer can be suppressed to some extent, and a high-performance microcomputer is not used. Also good. Therefore, the cost of an expensive microcomputer can be suppressed and it can contribute to the reduction of component costs.

  Furthermore, even if two microcomputers are used for control and monitoring, respectively, the processing capacity of the microcomputer used for monitoring should be lower than that used for control. it can. Therefore, the cost of an expensive microcomputer can be suppressed and it can contribute to the reduction of component costs.

  Further, the control arithmetic element used in the monitoring unit 20 cannot be simplified such that a part thereof is simply omitted in order to reduce the calculation load by the monitoring unit 20. That is, if a part of the control calculation element is simply omitted, the reliability of the failure diagnosis result by the monitoring unit 20 is lowered.

  On the other hand, the monitoring unit 20 performs control calculations similar to some control calculation elements among the plurality of control calculation elements used in the main control unit 10 and the remaining control among the plurality of control calculation elements. The calculation element calculates the engine control amount for monitoring using a value obtained by limiting the value calculated by the control calculation element on the main control unit 10 with a guard value within a predetermined range set in advance as the calculation value of the remaining control calculation elements. .

  Thereby, the reliability of the diagnosis result can be ensured while reducing the calculation load of the monitoring unit 20. Therefore, since the memory capacity is small and the processing performance of the microcomputer is low, it is possible to suppress a rise in the component cost and to provide the low-cost failure diagnosis apparatus 1 for the engine 2. Further, the main control unit 10 and the monitoring unit 20 can be configured by a single microcomputer.

  As described above, in the failure diagnosis apparatus 1 according to the embodiment of the present invention, the main control unit 10 calculates a control amount by combining a plurality of control calculation elements, and the monitoring unit 20 uses the plurality of control calculation elements. Control computation elements similar to some of the control computation elements are performed, and the remaining control computation elements of the plurality of control computation elements are set to values computed by the control computation elements on the main control unit 10. On the other hand, the control amount for monitoring is calculated using the value limited by the guard value within a predetermined range set in advance as the calculated value of the remaining control calculation elements. The reliability of the diagnosis result can be ensured while reducing the calculation load when performing the calculation.

  In the present embodiment, the correction amount calculated by the ISC control unit 30 is described as the upper limit guard set by the maximum value that can be taken by the control. However, the correction amount calculated by the ISC control unit 30 You may use together the lower limit guard value set with the minimum value which can be taken.

  In the above embodiment, the abnormality is determined by comparing the engine control amount that is the required torque and the monitoring engine control amount that is the monitoring torque, but the correction amount of the main control unit 10 and the monitoring unit The correction amount after 20 upper guards may be directly compared.

  The present invention is applicable to both gasoline engines and diesel engines. In addition to these vehicle engines, the present invention is useful for general internal combustion engines, but the monitoring target is not limited to these.

  As described above, the failure diagnosis apparatus according to the present invention can ensure the reliability of the diagnosis result while reducing the calculation load when performing the two systems of control and monitoring for the monitoring target. It is effective for a failure diagnosis apparatus for vehicles.

  DESCRIPTION OF SYMBOLS 1 ... Failure diagnosis apparatus, 2 ... Engine (internal combustion engine), 3 ... Engine ECU, 10 ... Main control part, 20 ... Monitoring part, 23 ... Comparison part, 30 ... ISC control part

Claims (4)

A main control unit that calculates a control amount by combining a plurality of control calculation elements;
While performing a control calculation similar to some control calculation elements of the plurality of control calculation elements used in the main control unit, the remaining control calculation elements of the plurality of control calculation elements are the main control unit A monitoring unit that calculates a control amount for monitoring using a value that is limited by a guard value within a predetermined range set in advance with respect to a value calculated by the above control calculation element, as a calculation value of the remaining control calculation element;
A failure diagnosis apparatus comprising:   The control amount calculated by the main control unit is compared with the monitoring control amount calculated by the monitoring unit, and the control amount value calculated by the main control unit is larger than the monitoring control amount value. The failure diagnosis apparatus according to claim 1, further comprising a comparison unit that determines that the monitoring target has failed on the condition that the monitoring target is larger. A valve control unit for adjusting the intake air amount of the internal combustion engine;
The failure diagnosis apparatus according to claim 1, wherein the main control unit uses a control calculation element for adjusting an intake air amount by the valve control unit as the plurality of control calculation elements. An ISC control unit that performs feedback control of an intake air amount when idling the internal combustion engine;
The ISC control unit calculates a correction value using the remaining control calculation elements of the plurality of control calculation elements,
The monitoring unit uses a correction value that does not deviate from the maximum upper limit guard value that can be taken in the preset control with respect to the correction value calculated by the ISC control unit as the remaining control calculation element. The fault diagnosis apparatus according to claim 3.

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