Abnormality determination device for internal combustion engine

Abstract

To provide an abnormality determination device for determining whether or not an internal combustion engine is in an abnormal state.SOLUTION: A device includes: control sections 21, 22, 23 that determine request torque on the basis of an accelerator pedal operation amount and control an internal combustion engine 10 on the basis of the request torque; and an abnormality determination section 27 that determines that the internal combustion engine is in an abnormal state when excessive torque that is an excess of actual engine torque relative to the request torque is larger than a torque deviation threshold value Qth. The abnormality determination device determines a reference value Qth0 calculated on the basis of the accelerator pedal operation amount as the torque deviation threshold value Qth when determining that the internal combustion engine is not in a deceleration state on the basis of a difference dT between the request torque and an averaged request torque obtained by applying delay averaging processing to the request torque, and determines an averaged torque deviation threshold value Qblr obtained by applying the delay averaging processing to the reference value Qth0 as the torque deviation threshold value Qth when determining that the internal combustion engine is in the deceleration state on the basis of the difference dT.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an abnormality determination device for an internal combustion engine, for determining whether or not the internal combustion engine is in an abnormal state in which excessive torque is generated. [Background technology]

[0002] Conventional devices control an internal combustion engine so that the internal combustion engine generates torque corresponding to the required torque. The conventional device estimates the torque actually generated by the internal combustion engine, and if the excess torque, which is the torque obtained by subtracting the required torque from the estimated torque, remains equal to or exceeds a torque deviation threshold for a duration threshold or longer, the conventional device determines that the internal combustion engine is in the abnormal state. The conventional device determines the torque deviation threshold and the duration threshold according to the accelerator pedal depression amount, which is correlated with the vehicle speed (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-14972 Summary of the Invention

[0004] When the accelerator pedal depression amount changes from a certain value to zero (i.e., immediately after a deceleration state occurs), the required torque, torque deviation threshold, and duration threshold each immediately decrease in response to the decrease in the accelerator pedal depression amount. On the other hand, when the accelerator pedal depression amount changes from a certain value to zero, the throttle valve opening is rapidly decreased, but the intake air volume does not decrease immediately but decreases with a response delay. Therefore, the torque generated by the internal combustion engine also decreases with a delay in response to a change in the accelerator pedal depression amount. In other words, the internal combustion engine has a response delay to a change in the required torque. Therefore, when a deceleration state occurs, the torque actually generated by the internal combustion engine becomes greater than the required torque, and the excessive torque is likely to remain above the torque deviation threshold. As a result, there is a risk that the internal combustion engine may be erroneously determined to be abnormal. The present invention has been made to address the above-mentioned problems.

[0005] One aspect of the abnormality determination device for an internal combustion engine of the present invention is to a control unit (21, 22, 23) that controls the internal combustion engine (10) to generate a torque equal to a required torque (Treq) determined based on an accelerator pedal operation amount (AP); an abnormality determination unit (27) that estimates the torque actually generated by the internal combustion engine as an engine torque (Tact), and determines that the internal combustion engine is in an abnormal state when an excessive torque state occurs in which an excessive torque (Qex) of the engine torque relative to the required torque is greater than a torque deviation threshold (Qth); An abnormality determination device for an internal combustion engine, comprising: A determination is made as to whether the internal combustion engine is in a deceleration state based on a difference (dT) between the required torque (Treq) and a smoothed required torque (Trb) obtained by performing a delay smoothing process on the required torque corresponding to a response delay of the internal combustion engine to a change in the required torque (B1 to B4). calculating a reference value (Qth0) of the torque deviation threshold based on the accelerator pedal operation amount; The apparatus is provided with a threshold calculation unit (26) configured to determine the reference value (Qth0) as the torque deviation threshold (Qth) when it is determined that the internal combustion engine is not in the deceleration state, and to determine the torque deviation threshold (Qth) as a post-smoothing torque deviation threshold (Qblr) obtained by applying a delay smoothing process corresponding to the response delay of the internal combustion engine to the reference value (Qth0) when it is determined that the internal combustion engine is in the deceleration state.

[0006] According to this, when the accelerator pedal depression amount is reduced and the vehicle is decelerating, the torque deviation threshold is changed in accordance with the response delay of the internal combustion engine, so that the excess torque (Qex) is unlikely to exceed the torque deviation threshold (Qth). Therefore, when the vehicle is decelerating, the possibility of erroneously determining that the internal combustion engine is in an abnormal state can be reduced. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic diagram of an abnormality determination device for an internal combustion engine according to an embodiment of the present invention; [Figure 2] Functional block diagram of the anomaly determination threshold calculation unit shown in Figure 1 [Figure 3] The routine executed by the CPU of the engine ECU shown in Figure 1 DETAILED DESCRIPTION OF THE INVENTION

[0008] An internal combustion engine abnormality determination device (hereinafter referred to as "this device") according to an embodiment of the present invention is incorporated into an engine ECU 20 that controls a multi-cylinder internal combustion engine 10 (hereinafter sometimes simply referred to as "engine 10"), which is a fuel injection, spark ignition, gasoline engine shown in FIG. 1. The engine ECU 20 is an electronic control device equipped with a microcomputer including a CPU, ROM, RAM, non-volatile memory, etc. The ROM stores constants, look-up tables, programs, etc. The engine ECU 20 controls the actuators of the engine 10, namely, the fuel injection valve 11, the ignition device 12, and the throttle motor 13.

[0009] The engine ECU 20 acquires output values ​​from the following sensors. An accelerator pedal operation amount sensor 31 that detects an accelerator pedal operation amount AP. A vehicle speed sensor 32 detects the speed (vehicle speed) SPD of the vehicle equipped with the engine 10. An engine rotation speed sensor 33 for detecting the rotation speed NE of the engine 10 . An air flow meter 34 detects the intake air amount Ga of the engine 10. An air-fuel ratio sensor 35 for detecting the air-fuel ratio AF of the exhaust gas of the engine 10.

[0010] The engine ECU 20 controls an alarm device 30 that includes an alarm buzzer and an alarm lamp. The engine ECU 20 includes various function execution units (21-28) described below that are realized by the CPU executing programs.

[0011] The required torque calculation unit 21 calculates the required torque Treq by applying the detected accelerator pedal operation amount AP and the detected vehicle speed SPD to a predetermined lookup table MapTreq(AP, SPD). According to the table MapTreq(AP, SPD), the required torque Treq increases as the accelerator pedal operation amount AP increases.

[0012] The control amount calculation unit 22 calculates the target torque Ttgt by adding the margin torque Tm to the required torque Treq. The control amount calculation unit 22 calculates the target load factor KLtgt by applying the calculated target torque Ttgt to a lookup table MapKLtgt(Ttgt) that is calculated in advance under the assumption that the air-fuel ratio is the stoichiometric air-fuel ratio and the ignition timing is MBT. The load factor is the ratio of the amount of intake air in the cylinder to the maximum amount of intake air in the cylinder, which is determined according to the engine speed NE. Furthermore, the control amount calculation unit 22 calculates the target throttle opening TAtgt by applying the calculated target load factor KLtgt and the detected engine speed NE to a lookup table MapTAtgt(KLtgt, NE) that is calculated in advance.

[0013] The control amount calculation unit 22 calculates the ignition timing SA by applying the required torque Treq, the target load factor KLtgt, and the detected engine speed NE to a lookup table MapSA(Treq, KLtgt, NE) that has been calculated in advance. As a result, the ignition timing SA is retarded by an amount corresponding to the margin torque Tm. In addition, the control amount calculation unit 22 calculates the fuel injection amount Finj required to make the air-fuel ratio of the mixture drawn into the engine 10 coincide with the stoichiometric air-fuel ratio, based on the detected intake air amount Ga and the detected engine speed NE, etc.

[0014] The actuator driving unit 23 drives the fuel injection valve 11 so that fuel is injected from the fuel injection valve 11 in the fuel injection amount Finj calculated by the control amount calculation unit 22. The actuator driving unit 23 controls the ignition device 12 so that ignition is performed at the ignition timing SA calculated by the control amount calculation unit 22. The actuator driving unit 23 drives the throttle motor 13 so that the actual throttle valve opening coincides with the target throttle opening TAtgt calculated by the control amount calculation unit 22.

[0015] The engine torque estimation unit 24 estimates the torque (engine torque) Tact actually generated by the engine 10 by applying the detected "engine speed NE, intake air amount Ga, and air-fuel ratio AF" to a predetermined lookup table MapTact(NE, Ga, AF).

[0016] The excess torque calculation unit 25 calculates the excess torque Qex by subtracting the required torque Treq from the engine torque Tact. The abnormality determination threshold calculation unit 26 calculates (determines) the torque deviation threshold Qth and the duration threshold Tth based on the accelerator pedal operation amount AP, as will be described in detail later with reference to FIG.

[0017] When the state in which the excessive torque Qex is greater than the torque deviation threshold Qth continues for a duration threshold Tth or longer, the abnormality determination unit 27 determines that the engine 10 is in an abnormal state in which excessive torque is being generated. When the abnormality determination unit 27 determines that the engine 10 is in an abnormal state in which excessive torque is being generated, it sounds the alarm buzzer of the alarm device 30, turns on the alarm lamp of the alarm device 30, and activates the fail-safe execution unit 28.

[0018] The fail-safe execution unit 28 sends an instruction signal to the actuator drive unit 23 so that the engine 10 generates a constant small torque. As a result, the actuator drive unit 23 drives the throttle motor 13 to change the throttle valve to a fully closed state, and the ignition timing is maintained at a fixed ignition timing. The fuel injection amount is set to the fuel injection amount Finj calculated by the control amount calculation unit 22.

[0019] The required torque Treq varies depending on the accelerator pedal depression amount AP. Therefore, when a deceleration operation is performed and the accelerator pedal depression amount AP suddenly decreases from a certain value to "0," the required torque Treq also suddenly decreases. Consequently, the throttle valve opening is also suddenly reduced. However, the intake air amount Ga decreases with a delay relative to changes in the accelerator pedal depression amount AP due to a response delay of the intake air. Therefore, the torque generated by the engine 10 also decreases with a delay relative to changes in the accelerator pedal depression amount AP. In other words, the engine 10 has a response delay to changes in the required torque. Therefore, when a deceleration operation is performed, the excess torque Qex temporarily increases, which may lead the abnormality determination unit 27 to erroneously determine that the engine 10 is in an abnormal state. Therefore, when the abnormality determination threshold calculation unit 26 (hereinafter referred to as "threshold calculation unit 26") determines that the engine 10 is in a deceleration state, it changes the torque deviation threshold Qth and the duration threshold Tth in accordance with the response delay of the engine 10.

[0020] More specifically, as shown in FIG. 2, the threshold calculation unit 26 performs a delay process B1 and a smoothing process (effectively a low-pass filter process) B2 corresponding to the response delay of the engine 10 on the required torque Treq to obtain a smoothed required torque Trb.

[0021] In this embodiment, delay processing means using, as the variable z, a variable z(t-Δt) a predetermined time Δt before for the variable z(t) at the current time t. Δt is an adaptive value. Furthermore, in this embodiment, smoothing processing means using Y(n) obtained by processing the current value X(n) of the variable X using the following equation instead of the variable X. Y(n-1) is the previous value of Y(n). a is an adaptive value greater than "0" and less than "1". Y(n)=a·Y(n-1)+(1-a)·X(n)

[0022] The threshold calculation unit 26 performs difference processing B3, which subtracts the required torque Treq from the smoothed required torque Trb, to calculate the difference dT, and then performs comparison processing B4, which determines that the vehicle is decelerating if the difference dT is positive. For example, as shown in block TM in FIG. 2, if the accelerator pedal depression amount AP suddenly decreases at time t1, the difference dT becomes positive from time t1 to time t3, and it is determined that the vehicle is decelerating from time t1 to time t3.

[0023] Meanwhile, the threshold calculation unit 26 calculates the torque deviation threshold reference value Qth0 by applying the accelerator pedal depression amount AP to the lookup table MapQ(AP) shown in block B5. According to the table MapQ(AP), the torque deviation threshold reference value Qth0 increases as the accelerator pedal depression amount AP increases. Furthermore, the threshold calculation unit 26 calculates a "smoothed torque deviation threshold Qblr" by performing "delay processing B6 and smoothing processing B7, which correspond to the response delay of the internal combustion engine 10," on the torque deviation threshold reference value Qth0. Then, if the first selection unit B8 determines that the vehicle is in a deceleration state, the threshold calculation unit 26 determines and outputs the "smoothed torque deviation threshold Qblr" as the final torque deviation threshold Qth. If the first selection unit B8 determines that the vehicle is in a deceleration state, the threshold calculation unit 26 determines and outputs the "torque deviation threshold reference value Qth0" as the final torque deviation threshold Qth.

[0024] Similarly, the threshold calculation unit 26 calculates the duration threshold reference value Tth0 by applying the accelerator pedal depression amount AP to the lookup table MapT(AP) illustrated in block B9. According to the table MapT(AP), the duration threshold reference value Tth0 increases as the accelerator pedal depression amount AP increases. Furthermore, the threshold calculation unit 26 calculates a "post-smoothing process duration threshold reference value Tblr" by performing "delay processing B10 and smoothing processing B11 corresponding to the response delay of the internal combustion engine 10" on the duration threshold reference value Tth0. Then, if the second selection unit B12 determines that the vehicle is in a deceleration state, the threshold calculation unit 26 determines and outputs the "post-smoothing process duration threshold reference value Tblr" as the final duration threshold Tth. If the second selection unit B12 determines that the vehicle is in a deceleration state, the threshold calculation unit 26 determines and outputs the "post-smoothing process duration threshold reference value Tblr" as the final duration threshold Tth. If the second selection unit B12 determines that the vehicle is not in a deceleration state, the threshold calculation unit 26 determines and outputs the "duration threshold reference value Tth0" as the final duration threshold Tth.

[0025] As a result, even if the excess torque Qex temporarily increases due to a delayed response of the engine 10 when the accelerator pedal depression amount AP suddenly decreases, the excess torque Qex is unlikely to exceed the torque deviation threshold Qth, and even if the excess torque Qex does exceed the torque deviation threshold Qth, this state is unlikely to continue for longer than the duration threshold Tth. This reduces the possibility of erroneously determining that the engine 10 is in an abnormal state.

[0026] Next, a specific operation of the CPU of the engine ECU 20 will be described. The CPU executes the routine shown in the flowchart of FIG. 3 every time a predetermined time elapses. Therefore, at a predetermined timing, the CPU starts processing from step (hereinafter referred to as "S") 300 in FIG. 3 and proceeds to S305, where it determines whether the value of an abnormality determination flag Xab, which indicates that the engine 10 is determined to be in an abnormal state generating excessive torque when the value is "1," is "0." The value of the abnormality determination flag Xab is stored in a non-volatile memory.

[0027] If the value of flag Xab is not "0", the CPU executes the process of S360 described below, then proceeds to S395, and temporarily ends this routine. On the other hand, if the value of flag Xab is "0", the CPU executes the "processing of S310 to S330" described below, and then proceeds to S335. S310: The CPU obtains the required torque Treq as described above. S315: The CPU obtains the engine torque Tact as described above. S320: The CPU obtains the excess torque Qex as described above. S325: The CPU reads the torque deviation threshold value Qth determined as described above. S330: The CPU reads the duration threshold Tth determined as described above.

[0028] In S335, the CPU determines whether the excess torque Qex is greater than the torque deviation threshold Qth, and if the excess torque Qex is greater than the torque deviation threshold Qth, in S340 the CPU increases the value of the timer T by "1". Next, the CPU proceeds to S345, where it determines whether the value of the timer T is greater than the duration threshold Tth. If the value of the timer T is greater than the duration threshold Tth, the CPU determines in S350 that the engine 10 is in an abnormal state and sets the value of the abnormality determination flag Xab to "1". Thereafter, the CPU performs the above-mentioned fail-safe processing in S355, proceeds to S395, and temporarily ends this routine.

[0029] If the CPU determines "No" in S335, it proceeds to S360 to set the value of timer T to "0", and then proceeds to S395.

[0030] As described above, the present device changes the torque deviation threshold Qth and the duration threshold Tth in response to the delayed response of the engine 10 caused by the delayed response of the intake air during deceleration when the accelerator pedal depression amount is reduced. Therefore, the excessive torque Qex is unlikely to exceed the torque deviation threshold Qth, and even if the excessive torque Qex does exceed the torque deviation threshold Qth, this state is unlikely to continue for longer than the duration threshold Tth. Therefore, when a deceleration state occurs, the present device can reduce the possibility of erroneously determining that the engine 10 is in an abnormal state in which it continues to generate excessive torque.

[0031] The present invention is not limited to the above embodiment, and various modifications can be adopted within the scope of the present invention. For example, the duration threshold reference value Tth0, which is not subjected to delay smoothing processing, may always be adopted as the duration threshold Tth. [Explanation of symbols]

[0032] 10... internal combustion engine, 20... engine ECU, 26... abnormality determination threshold calculation unit, 27... abnormality determination unit

Claims

[Claim 1] a control unit that controls the internal combustion engine so that the internal combustion engine generates a torque equal to a required torque determined based on an accelerator pedal operation amount; an abnormality determination unit that estimates the torque actually generated by the internal combustion engine as engine torque, and determines that the internal combustion engine is in an abnormal state when an excessive torque state occurs in which the excess torque of the engine torque relative to the required torque is greater than a torque deviation threshold value; An abnormality determination device for an internal combustion engine, comprising: determining whether the internal combustion engine is in a deceleration state based on a difference between the required torque and a smoothed required torque obtained by performing a delay smoothing process on the required torque corresponding to a response delay of the internal combustion engine to a change in the required torque; calculating a reference value of the torque deviation threshold based on the accelerator pedal operation amount; When it is determined that the internal combustion engine is not in the deceleration state, the reference value is determined as the torque deviation threshold value; When it is determined that the internal combustion engine is in the deceleration state, a post-smoothing torque deviation threshold value obtained by performing a delay smoothing process corresponding to a response delay of the internal combustion engine on the reference value is determined as the torque deviation threshold value. a threshold calculation unit configured as follows: An abnormality determination device for an internal combustion engine, comprising:

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