JP2015052289A - Cylinder pressure sensor abnormality detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To determine abnormality in a cylinder pressure sensor by separating the same from the abnormality in a compression ratio or friction of an internal combustion engine.SOLUTION: A cylinder pressure sensor abnormality detection device: estimates a variation of a compression ratio of an internal combustion engine in accordance with a period from a start of stop control of the internal combustion engine to a stop thereof; calculates an estimated value of a maximum cylinder pressure after the start of the stop control in accordance with the estimated variation of the compression ratio; and acquires an actual maximum cylinder pressure after the start of the stop control on the basis of output of a cylinder pressure sensor after the start of the stop control. The cylinder pressure sensor abnormality detection device determines abnormality in sensitivity of the cylinder pressure sensor with the actual maximum cylinder pressure and the estimated value as parameters.

Description

  The present invention relates to an abnormality detection device for an in-cylinder pressure sensor. Specifically, the present invention relates to an abnormality detection device that determines whether or not an in-cylinder pressure sensor disposed in a cylinder of an internal combustion engine is abnormal.

  Patent Document 1 discloses a system for diagnosing abnormality of an in-cylinder pressure sensor. In this system, a parameter representing a change state of the pressure state is calculated based on the in-cylinder pressure state detected when the fuel supply to the internal combustion engine is stopped, and based on the transition of the calculated parameter, An abnormality of the in-cylinder pressure sensor is detected.

JP 2007-113473 A JP 2005-002847 A JP 2012-149562 A JP2011-236826A JP 2008-089443 A

  By the way, the value of the in-cylinder pressure obtained from the output of the in-cylinder pressure sensor is different between the case where the sensitivity abnormality of the in-cylinder pressure sensor occurs and the case where an abnormality occurs in the compression ratio of the internal combustion engine or the friction change occurs. It is similar. For this reason, for example, in the abnormality determination based on the output change of the in-cylinder pressure sensor as in Patent Document 1, it is difficult to separate the sensitivity abnormality of the in-cylinder pressure sensor from the abnormality of the compression ratio and friction. However, it is very important to identify the failure part in the operation of the internal combustion engine.

  The present invention has been made in view of the above points, and has been improved so that the abnormality of the compression ratio or friction of the internal combustion engine and the abnormality of the in-cylinder pressure sensor can be separated and the presence or absence of the abnormality of the in-cylinder pressure sensor can be determined. An object of the present invention is to provide an abnormality detection device for an in-cylinder pressure sensor.

In order to achieve the above object, a first invention is an in-cylinder pressure sensor abnormality detection device comprising:
An in-cylinder pressure sensor disposed in a cylinder of the internal combustion engine;
Means for estimating the amount of change in the compression ratio of the internal combustion engine according to the time from the start of stop control of the internal combustion engine to the stop of the internal combustion engine;
Means for calculating an estimated value of the maximum in-cylinder pressure after the start of the stop control according to the estimated amount of change in the compression ratio;
Means for obtaining an actual maximum in-cylinder pressure after the start of the stop control based on an output of the in-cylinder pressure sensor after the start of the stop control;
Means for determining presence or absence of sensitivity abnormality of the in-cylinder pressure sensor, using the actual maximum in-cylinder pressure and the estimated value as parameters;
Is provided.

  According to the present invention, it is possible to estimate the degree of change in the compression ratio according to the time from the start of stop control of the internal combustion engine to the stop of the internal combustion engine. Thereby, the estimated value of the maximum in-cylinder pressure corresponding to the influence of the change in the compression ratio can be calculated from the start of the internal combustion engine stop control. Then, by comparing the estimated value of the maximum in-cylinder pressure with the actual maximum in-cylinder pressure, the change in the maximum in-cylinder pressure due to the influence of the compression ratio change and the change in the maximum in-cylinder pressure due to the abnormality of the in-cylinder pressure sensor are separated. Whether or not the in-cylinder pressure sensor is abnormal can be determined. Therefore, the presence or absence of abnormality of the in-cylinder pressure sensor can be determined with higher accuracy.

It is a schematic block diagram for demonstrating the whole structure of the system of Embodiment 1 of this invention. It is a figure for demonstrating the change of the maximum in-cylinder pressure after the engine stop control start in Embodiment 1 of this invention until an engine stop. It is a figure for demonstrating the change of the maximum in-cylinder pressure of each cylinder after engine stop control start in Embodiment 1 of this invention until an engine stop. It is a figure for demonstrating the relationship between the largest in-cylinder pressure at the time of an engine stop in Embodiment 1 of this invention, and an update timing. It is a flowchart for demonstrating the control routine which ECU performs in Embodiment 1 of this invention. It is a figure for demonstrating the relationship between the largest cylinder pressure at the time of an engine stop, and update timing in Embodiment 2 of this invention. It is a flowchart for demonstrating the control routine which ECU performs in Embodiment 2 of this invention. It is a figure for demonstrating the relationship between the maximum in-cylinder pressure at the time of an engine stop and update timing in Embodiment 3 of this invention. It is a figure for demonstrating the relationship between the update timing and compression ratio change amount in Embodiment 3 of this invention. It is a figure for demonstrating the relationship between the compression ratio variation | change_quantity and the estimated value of the largest in-cylinder pressure in Embodiment 3 of this invention. It is a figure for demonstrating the relationship between the maximum in-cylinder pressure at the time of the engine stop in Embodiment 4 of this invention, and the compression ratio raise amount or compression loss amount. It is a figure for demonstrating the relationship between the compression ratio variation | change_quantity and the estimated value of an update timing in Embodiment 4 of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted. The present invention is not limited to the following embodiments.

Embodiment 1 FIG.
[System configuration of the present embodiment]
FIG. 1 is a schematic configuration diagram for explaining an overall configuration of a system according to an embodiment of the present invention. In the system of FIG. 1, the internal combustion engine is a spark ignition engine 10. The engine 10 has four cylinders 12. However, the internal combustion engine in the present invention is not limited to four cylinders. The engine 10 is provided with a crank angle sensor 14. An in-cylinder pressure sensor 16 is installed in each cylinder 12. The in-cylinder pressure sensor 16 is a sensor that generates an output corresponding to the pressure in the cylinder 12, and can detect the in-cylinder pressure. The system according to the present embodiment includes an ECU (Electronic Control Unit) 20 as a control device. Various sensors such as the crank angle sensor 14 and the in-cylinder pressure sensor 16 described above and various actuators such as an injector are connected to the ECU 20. ECU20 can control the driving | running state of the engine 10 by driving each actuator according to a predetermined control program based on the output of each of those sensors.

[In-cylinder pressure sensor abnormality detection control]
The control executed by the ECU 20 in the present embodiment includes control for detecting the in-cylinder pressure and detecting abnormality of the in-cylinder pressure sensor based on the detection. Control of abnormality detection of the in-cylinder pressure sensor is executed as follows.

  FIG. 2 is a diagram for explaining a change in the maximum in-cylinder pressure from the start of the engine stop control to the stop of the engine. In FIG. 2, the horizontal axis represents time, and the vertical axis represents the maximum in-cylinder pressure for each cycle of a certain cylinder. When the fuel supply is stopped (F / C) by starting the engine stop control, the maximum in-cylinder pressure gradually decreases until the engine is stopped, as shown in FIG.

  FIG. 3 is a diagram for explaining a change in the maximum in-cylinder pressure of each cylinder from the start of the engine stop control to the stop of the engine in the first embodiment of the present invention, in the vicinity of the broken line A including the broken line A of FIG. The timing of (immediately before the engine stops) is enlarged. In FIG. 3, the numerical values shown in circles are cylinder numbers, and the maximum in-cylinder pressure Pmax is a value based on the output of the in-cylinder pressure sensor detected in the compression TDC of each cylinder. As shown in FIG. 3, the value of the maximum in-cylinder pressure Pmax of each cylinder gradually decreases after the engine stop is started, but when the engine is stopped, the piston stops without exceeding the compression TDC due to the compression reaction force. Accordingly, the maximum in-cylinder pressure Pmax is not detected after the engine is stopped.

  In the present embodiment, the maximum in-cylinder pressure Pmax is detected and updated every time at the compression TDC timing for each cylinder 12 until the engine is stopped after the engine stop control is started. In the control of the first embodiment, the final value detected immediately before the engine is stopped is used as the maximum in-cylinder pressure Pmax. Further, the time required from the start of the engine stop control to the last detection of the maximum in-cylinder pressure Pmax is detected as the update timing t and used for the following control. The following control may be executed for each cylinder, and will be described using one cylinder as an example.

  By the way, when the in-cylinder pressure sensor 16 and the engine 10 are normal, the value of the maximum in-cylinder pressure when the engine is stopped and the value of the time (update timing) required from the start of the engine stop control to the engine stop are obtained through experiments, simulations, or It can be calculated theoretically. In the present embodiment, the maximum in-cylinder pressure during normal stop (maximum in-cylinder pressure during normal operation) Pmax_ok and the update timing during normal operation (update timing during normal operation) t_ok are obtained in advance and stored in the ECU 20 in advance. Keep it. Then, by comparing the detected maximum in-cylinder pressure Pmax and the update timing t with a pre-stored value at normal time, it is determined whether there is an abnormality in the in-cylinder pressure sensor 16 and the compression ratio change.

  FIG. 4 is a diagram for illustrating the relationship between the maximum in-cylinder pressure Pmax when the engine is stopped and the update timing t in the first embodiment of the present invention. In FIG. 4, the horizontal axis represents the update timing t, and the vertical axis represents the maximum in-cylinder pressure Pmax. In the abnormality determination control according to the first embodiment, the determination is divided into the following five cases.

(A) Normality determination As shown in FIG. 4A, when the detected update timing t coincides with the normal update timing t_ok, and the maximum in-cylinder pressure Pmax coincides with the normal maximum in-cylinder pressure Pmax_ok, compression is performed. It is determined that both the ratio and the sensitivity of the in-cylinder pressure sensor 16 are normal.

(B) Abnormal determination of sensitivity increase of in-cylinder pressure sensor As shown in FIG. 4B, the update timing t coincides with the normal update timing t_ok, but the maximum in-cylinder pressure Pmax is larger than the normal maximum in-cylinder pressure Pmax_ok. It is determined that an abnormality in sensitivity increase has occurred in the in-cylinder pressure sensor 16.

(C) Abnormality Determination of Sensitivity Reduction of In-Cylinder Pressure Sensor On the other hand, as shown in FIG. 4C, the update timing t coincides with the normal update timing t_ok, but the maximum in-cylinder pressure Pmax is greater than the normal maximum cylinder pressure Pmax_ok. Is also small, it is determined that an abnormality in sensitivity reduction has occurred in the in-cylinder pressure sensor 16.

(D) Abnormal determination of compression ratio increase As shown in FIG. 4D, the update timing t is earlier than the normal update timing t_ok (that is, t is smaller than t_ok), and the maximum in-cylinder pressure Pmax is the maximum at normal time. When the pressure is greater than the in-cylinder pressure Pmax_ok, it is determined that an abnormality in which the compression ratio increases is occurring.

(E) Abnormal determination of compression loss As shown in E of FIG. 4, the update timing t is later than the normal time t_ok (that is, t is larger than t_ok), and the maximum in-cylinder pressure Pmax is the normal maximum in-cylinder pressure Pmax_ok. If it is smaller, it is determined that an abnormality in compression loss has occurred in the engine.

[Specific Control of First Embodiment]
FIG. 5 is a flowchart for illustrating a control routine executed by ECU 20 in the first embodiment of the present invention. The routine of FIG. 5 is a routine that is repeatedly executed while the engine 10 is operating. In the routine of FIG. 5, first, in step S100, it is determined whether or not the engine stop control is started and the fuel supply is stopped (F / C = ON). If the stop of fuel supply is not permitted, the current process is temporarily terminated.

  When the stop of fuel supply is recognized in step S100, sampling of the in-cylinder pressure is started (S102). Here, the output of the in-cylinder pressure sensor 16 is acquired for each compression TDC, the in-cylinder pressure is detected, and this value is sequentially updated as the maximum in-cylinder pressure Pmax.

  Next, it is determined whether or not the engine 10 has been stopped (S104). When the engine stop is not recognized, the process returns to step S102 and sampling of the in-cylinder pressure is continued. The in-cylinder pressure is sampled until the engine stop is recognized in step S104.

  When the engine stop is confirmed in step S104, the final value of the maximum in-cylinder pressure Pmax and the update timing t are acquired (S106). That is, the last updated value of the maximum in-cylinder pressure Pmax is obtained as the maximum in-cylinder pressure Pmax, and the time from the start of engine stop control until the final value of the maximum in-cylinder pressure Pmax is updated is acquired as the update timing t.

  Next, it is determined whether or not the difference (Pmax−Pmax_ok) between the maximum in-cylinder pressure Pmax and the normal maximum in-cylinder pressure Pmax_ok is larger than a predetermined value α1 (S108). The predetermined value α1 is a value stored in the ECU 20 in advance, and is a reference value for determining whether or not the maximum in-cylinder pressure Pmax substantially matches the normal maximum in-cylinder pressure Pmax_ok.

  If it is determined in step S108 that the difference between the maximum in-cylinder pressure Pmax and the normal maximum cylinder pressure Pmax_ok is larger than the predetermined value α1, then the difference between the normal update timing t_ok and the update timing t (t_ok−t). Is greater than a predetermined value β1 (S110). The predetermined value β1 is a value stored in the ECU 20 in advance, and is a value serving as a reference for determining whether or not the update timing t substantially matches the normal update timing t_ok.

  In step S110, when it is recognized that the difference between the normal update timing t_ok and the update timing t is larger than the predetermined value β1, it is determined in step S112 that the compression ratio is abnormal (corresponding to D above). On the other hand, in step S110, when it is not recognized that the difference between the normal update timing t_ok and the update timing t is larger than the predetermined value β1, it is determined that the sensitivity increase of the in-cylinder pressure sensor 16 is abnormal (corresponding to B above). . Thereafter, the current process is temporarily terminated.

  On the other hand, if it is not determined in step S108 that the difference between the maximum in-cylinder pressure Pmax and the normal maximum cylinder pressure Pmax_ok is greater than the predetermined value α1, then the difference between the normal maximum cylinder pressure Pmax_ok and the maximum in-cylinder pressure Pmax is determined. It is determined whether (Pmax_ok−Pmax) is larger than a predetermined value α1 (S116).

  In step S116, if it is recognized that the difference between the normal maximum cylinder pressure Pmax_ok and the maximum cylinder pressure Pmax is larger than the predetermined value α1, then the difference between the update timing t and the normal update timing t_ok (t−t_ok). Is determined to be greater than a predetermined value β1 (S118).

  If it is determined in step S118 that the difference between the update timing t and the normal update timing t_ok is greater than the predetermined value β1, it is determined in step S120 that the compression loss is abnormal (corresponding to E above). On the other hand, if it is not recognized in step S118 that the difference between the update timing t and the normal update timing t_ok is greater than the predetermined value β1, it is determined that the sensitivity of the in-cylinder pressure sensor 16 is abnormal (corresponding to C above). . Thereafter, the current process is temporarily terminated.

  In step S116, when it is not recognized that the difference between the normal maximum in-cylinder pressure Pmax_ok and the maximum in-cylinder pressure Pmax is larger than the predetermined value α1, the current process ends. That is, since the maximum in-cylinder pressure Pmax is normally detected, it is determined that the compression ratio and the sensitivity of the in-cylinder pressure sensor 16 are both normal (corresponding to A above).

  As described above, according to the first embodiment, the abnormality due to the change in the compression ratio and the sensitivity abnormality of the in-cylinder pressure sensor 16 can be distinguished and determined. Therefore, the abnormality determination of the in-cylinder pressure sensor 16 can be performed with higher accuracy, and the illustrated torque and the like using the in-cylinder pressure sensor 16 can be correctly calculated.

  In the present embodiment, the same predetermined value α1 is used as the reference value for the determination in step S108 and step S116. However, the predetermined value α1 is a value that can be set as appropriate according to the accuracy of the determination and the like. This is not limited to the case where the predetermined value α1 is used. Similarly, the same predetermined value β1 is used as the reference value for the determination in step S110 and step S118, but is not limited to the case where the same predetermined value β1 is used. The same applies to the following embodiments.

Embodiment 2. FIG.
The system of the second embodiment has the same configuration as in FIG. The system according to the second embodiment executes the same control as the system according to the first embodiment except that the determination is made by distinguishing the influence of the friction change in addition to the abnormality of the compression ratio and the sensitivity of the in-cylinder pressure sensor 16.

  In the second embodiment, the detection method of the maximum in-cylinder pressure Pmax and the update timing t is the same as that of the first embodiment. FIG. 6 is a diagram for explaining the relationship between the maximum in-cylinder pressure Pmax when the engine is stopped and the update timing t in Embodiment 2 of the present invention. In FIG. 6, the horizontal axis represents the update timing t, and the vertical axis represents the maximum in-cylinder pressure Pmax. In the control of abnormality determination of the second embodiment, the following two determinations (F) and (G) are further added to the same determination as (A) to (E) of the first embodiment. A determination divided into determinations is performed.

In the following, the normal update timing n cycles before the normal update timing t_ok is expressed as “t_ok− _n ”, and the normal update timing after n cycles is expressed as “t_ok _{+ n} ”. Further, the normal maximum in-cylinder pressures n cycles before or after the final update timing t_ok at normal time are expressed as “Pmax_ok− _n ” and “Pmax_ok _{+ n} ”, respectively. These values before and after n cycles are values that can be obtained and set in advance by experiment, simulation, or theoretically in the same manner as the normal maximum cylinder pressure Pmax_ok and the normal update timing t_ok. In the second embodiment, these set values are stored in the ECU 20 in advance.

(F) Friction rise abnormality determination When the maximum in-cylinder pressure Pmax is greater than the normal maximum cylinder pressure Pmax_ok and the update timing t is earlier than the normal update timing t_ok, the update timing t is further updated when normal. When normal update timing t_ok _-n n cycles before timing t_ok and the maximum in-cylinder pressure Pmax matches the normal maximum cylinder pressure Pmax_ok _-n at the normal update timing t_ok _-n before n cycles Is determined not to be an abnormal increase in compression ratio but to increase in friction.

(G) Abnormal determination of friction reduction When the maximum in-cylinder pressure Pmax is smaller than the normal maximum cylinder pressure Pmax_ok and the update timing t is later than the normal update timing t_ok, the update timing t is further updated when normal. When normal update timing t_ok _{+ n} after n cycles of timing t_ok and the maximum in-cylinder pressure Pmax coincides with normal maximum in-cylinder pressure Pmax_ok _{+ n} at the normal update timing t_ok _{+ n} after n cycles, compression is performed. It is determined that the friction is not reduced but the ratio is not abnormal.

  FIG. 7 is a flowchart for illustrating a control routine executed by ECU 20 in the second embodiment of the present invention. The routine of FIG. 7 includes the processes of steps S202 to S206 instead of the process of step S112 when the determination of step S110 is “YES”, and the process of step S120 when the determination of step S118 is “YES”. This routine is the same as the routine of FIG. 5 except that the processes of steps S212 to S216 are provided instead of the process of FIG.

In the routine of FIG. 7, if it is determined in step S110 that the difference between the normal update timing t_ok and the update timing t is greater than the predetermined value β1, then in step S202, the normal update timing n cycles before The absolute value of the difference between t_ok- _n and the update timing t is smaller than the predetermined value β2, and the absolute value of the difference between the normal maximum cylinder pressure Pmax_ok- _n and the maximum cylinder pressure Pmax at the normal update timing t_ok- _n before n cycles. It is determined whether the value is smaller than a predetermined value α2. Here, the predetermined values α2 and β2 are reference values for determining whether the update timing and the maximum in-cylinder pressure are approximately equal to the values at the normal time, and are values set in advance and stored in the ECU 20.

  When the determination in step S202 is “YES”, it can be determined that the maximum in-cylinder pressure Pmax is a normal value and only the stop timing is advanced. Therefore, in this case, it is determined in step S204 that the friction is abnormal (corresponding to F above). On the other hand, when the determination in step S202 is “NO”, it is determined that the compression ratio is abnormally increased (S206). Thereafter, the current process ends.

On the other hand, if it is found in the process of step S118 that the difference between the update timing t and the normal update timing t_ok is greater than the predetermined value β1, then in step S212, the normal update timing t_ok _{+ n} after n cycles The absolute value of the difference from the update timing t is smaller than the predetermined value β2, and the absolute value of the difference between the normal maximum cylinder pressure Pmax_ok _{+ n} and the maximum cylinder pressure Pmax at the normal update timing t_ok _{+ n} after n cycles is a predetermined value α2. It is determined whether it is smaller.

  When the determination in step S212 is “YES”, it can be determined that the maximum in-cylinder pressure Pmax is a normal value and only the stop timing is delayed. Therefore, in this case, it is determined in step S214 that there is an abnormality in friction reduction (corresponding to G above). On the other hand, if the determination in step S212 is “NO”, it is determined that the compression loss is abnormal (S216). Thereafter, the current process ends.

  As described above, by determining abnormality according to the case classification of the second embodiment, it is possible to determine for each cylinder by separating the change in compression ratio, the change in sensitivity of the in-cylinder pressure sensor, and the change in friction.

  Note that the case where the same predetermined values α2 and β2 are used in the determinations in steps S202 and S212 has been described, but the present invention is not limited to this, and different values may be used as the reference values for determination. The same applies to the following embodiments.

Embodiment 3 FIG.
The system of the third embodiment has the same configuration as the system of FIG. The system according to the third embodiment is the same as the system according to the first embodiment except that when the compression ratio abnormality and the sensitivity abnormality of the in-cylinder pressure sensor 16 occur simultaneously, each abnormality is determined separately. Take control.

  FIG. 8 is a diagram for explaining the relationship between the maximum in-cylinder pressure and the update timing when the engine is stopped in the third embodiment of the present invention. As shown in FIG. 8, for example, when the maximum in-cylinder pressure Pmax is larger than the normal maximum cylinder pressure Pmax_ok and the update timing t is earlier than the normal update timing t_ok, the normal maximum cylinder pressure Pmax_ok is equal to the normal maximum cylinder pressure Pmax_ok. The difference includes the one caused by the sensitivity abnormality of the in-cylinder pressure sensor 16 and the one caused by the increase in the compression ratio. Accordingly, the degree of sensitivity abnormality or compression ratio increase abnormality of the in-cylinder pressure sensor 16 cannot be determined only by the maximum in-cylinder pressure Pmax and the update timing t. Therefore, in this embodiment, as will be described below, an estimated value of the maximum in-cylinder pressure (value indicated by an asterisk in FIG. 8) due to the influence of the increase in the compression ratio is obtained, and this value and the value of the maximum in-cylinder pressure Pmax. As a parameter, the sensitivity abnormality of the in-cylinder pressure sensor 16 is determined.

  FIG. 9 is a diagram for explaining the relationship between the update timing t and the compression ratio change amount according to Embodiment 3 of the present invention, and FIG. 9A shows the relationship between the update timing t and the compression ratio increase amount. , (B) represents the relationship between the update timing t and the compression loss amount.

  As shown in FIG. 9A, the compression ratio increase amount becomes zero when the update timing t coincides with the normal update timing t_ok, and becomes proportional as the update timing t becomes earlier than the normal update timing t_ok. Have a growing relationship. Further, as shown in FIG. 9B, the compression loss amount is zero when the update timing t matches the normal update timing t_ok, and as the update timing t becomes later than the normal update timing t_ok. , Have a proportionally larger relationship.

  Such a correlation between the update timing t and the amount of increase or loss of the compression ratio can be obtained in advance by experiments or simulations. In the present embodiment, the compression ratio increase amount or dropout amount corresponding to the update timing t is calculated based on this correlation.

  FIG. 10 is a diagram for explaining the relationship between the compression ratio change amount and the estimated value Pmax_ε of the maximum in-cylinder pressure in the third embodiment of the present invention. FIG. 10 (a) shows the compression ratio increase amount and the estimated value Pmax_ε. (B) is a figure for demonstrating the relationship between compression loss amount and estimated value Pmax_ε.

  As shown in FIG. 10A, when the amount of increase in the compression ratio is large, the amount of increase in the maximum in-cylinder pressure Pmax resulting from the increase in the compression ratio becomes large. Therefore, the estimated value Pmax_ε of the maximum in-cylinder pressure resulting from the increase in the compression ratio (that is, excluding the influence due to the sensitivity fluctuation of the in-cylinder pressure sensor 16) increases as the increase in the compression ratio increases. On the other hand, as shown in FIG. 10B, when the amount of compression loss increases, the amount of decrease in the maximum in-cylinder pressure Pmax caused by compression loss increases. Therefore, the estimated value Pmax_ε of the maximum in-cylinder pressure resulting from the compression loss (that is, excluding the influence due to the sensitivity fluctuation of the in-cylinder pressure sensor 16) becomes smaller as the amount of compression loss increases.

  There is a correlation between the amount of increase or loss of the compression ratio and the estimated value Pmax_ε of the maximum in-cylinder pressure corresponding to the amount, and the correlation is obtained in advance by experiments or simulations. In the present embodiment, based on this correlation, an estimated value Pmax_ε corresponding to the amount of increase in the compression ratio or the amount of loss is calculated.

  In the third embodiment, a ratio (Pmax / Pmax_ε) between the calculated estimated value Pmax_ε and the maximum in-cylinder pressure Pmax is obtained. Sensitivity abnormality of the in-cylinder pressure sensor 16 is determined using this ratio as a parameter. That is, if the parameter is 1, it is determined that there is no abnormality in sensitivity of the in-cylinder pressure sensor 16. In addition, as the difference (absolute value) between the parameter and 1 increases, the degree of sensitivity abnormality of the in-cylinder pressure sensor 16 increases, and as the difference between the parameter and 1 decreases, the degree of sensitivity abnormality of the in-cylinder pressure sensor 16 increases. It is determined to be small. For example, a threshold value for determining sensitivity abnormality may be set, and when the difference between the parameter and 1 is larger than the threshold value, it may be determined that the cylinder pressure sensor 16 has a sensitivity abnormality.

  In the third embodiment, the case where the presence or absence of the sensitivity abnormality of the in-cylinder pressure sensor 16 or the degree of the sensitivity abnormality is determined according to the ratio between the estimated value Pmax_ε and the maximum in-cylinder pressure Pmax has been described. It is not limited to this. For example, the sensitivity abnormality of the in-cylinder pressure sensor 16 may be determined using a difference between the estimated value Pmax_ε and the maximum in-cylinder pressure Pmax as a parameter.

  In the present embodiment, the case where the compression ratio and the sensitivity abnormality of the in-cylinder pressure sensor 16 are determined using the final update timing t, the maximum in-cylinder pressure Pmax, and the estimated value Pmax_ε at that time as parameters has been described. . However, the present invention is not limited to this, and any update timing and maximum in-cylinder pressure may be used as long as the timing is after the start of engine stop control. However, the detection timing of the maximum in-cylinder pressure Pmax and the estimated value Pmax_ε need to be the same timing.

Embodiment 4 FIG.
The system of the fourth embodiment has the same configuration as the system of FIG. The system of the fourth embodiment performs the same control as the system of FIG. 2 except that when the compression ratio change and the friction change occur at the same time, abnormality determination is performed by dividing the degree of each abnormality.

  Referring to FIG. 6, for example, when the maximum in-cylinder pressure Pmax is larger than the normal maximum cylinder pressure Pmax_ok and the update timing t is earlier than the normal update timing t_ok, the difference in the maximum in-cylinder pressure Pmax includes a compression ratio abnormality. The cause and the cause due to the friction abnormality are included, and the degree of abnormality of the compression ratio and the friction cannot be determined only by the maximum in-cylinder pressure Pmax and the update timing t. Therefore, in the present embodiment, the update timing due to the compression ratio abnormality is estimated from the update timing t, and the friction abnormality is determined using the estimated value and the update timing t as parameters.

  FIG. 11 is a diagram for explaining the relationship between the maximum in-cylinder pressure Pmax and the compression ratio change amount according to the fourth embodiment of the present invention. FIG. 11A shows the relationship between the maximum in-cylinder pressure Pmax and the compression ratio increase amount. (B) represents the relationship between the maximum in-cylinder pressure Pmax and the amount of compression loss.

  As shown in FIG. 9A, the compression ratio increase amount becomes zero when the maximum in-cylinder pressure Pmax coincides with the normal maximum cylinder pressure Pmax_ok, and the maximum in-cylinder pressure Pmax is larger than the normal maximum cylinder pressure Pmax_ok. As it becomes, it has a relationship that increases proportionally. Further, as shown in FIG. 9B, the compression loss amount is zero when the maximum in-cylinder pressure Pmax matches the normal maximum cylinder pressure Pmax_ok, and the maximum in-cylinder pressure Pmax is normal maximum cylinder pressure Pmax_ok. As it becomes smaller, it has a relationship that increases proportionally.

  Such a correlation between the maximum in-cylinder pressure Pmax and the amount of increase or loss of the compression ratio can be obtained in advance by experiments or simulations. In the fourth embodiment, the compression ratio increase amount or dropout amount corresponding to the maximum in-cylinder pressure Pmax is calculated based on this correlation.

  FIG. 12 is a diagram for explaining the relationship between the compression ratio change amount and the update timing estimated value t_ε in Embodiment 4 of the present invention. FIG. 12A shows the relationship between the compression ratio increase amount and the estimated value t_ε. (B) is a diagram for explaining the relationship between the compression loss amount and the estimated value t_ε.

  As shown in FIG. 10A, when the amount of increase in the compression ratio is large, the variation in the update timing t due to the increase in the compression ratio becomes large. Accordingly, the update timing estimated value t_ε due to the effect of the compression ratio increase (that is, excluding the effect of the friction change) becomes earlier (becomes a smaller value) as the compression ratio increase amount increases. On the other hand, as shown in FIG. 10B, the delay in the update timing due to the compression loss increases as the compression loss amount increases. Therefore, the delay with respect to the normal update timing t_ok of the estimated value t_ε of the update timing due to the effect of compression loss (that is, excluding the effect of the change in friction) becomes large.

  As described above, the compression ratio increase amount or dropout amount and the estimated update timing t_ε corresponding thereto have a correlation, and the correlation is obtained in advance through experiments, simulations, or the like. In the present embodiment, an estimated value t_ε is calculated according to the compression ratio increase amount or dropout amount.

  In the present embodiment, a ratio (t / t_ε) between the calculated estimated value t_ε and the update timing t is obtained. Friction abnormality is determined using this ratio as a parameter. That is, if the parameter is 1, it is determined that there is no abnormality in friction. Further, it is determined that the degree of friction abnormality is larger as the difference (absolute value) between the parameter and 1 is larger, and the degree of friction abnormality is smaller as the difference between the parameter and 1 is smaller. For example, a threshold value for determining a friction abnormality may be set, and if the difference (absolute value) between the parameter and 1 is larger than the threshold value, the friction abnormality may be determined.

  In the fourth embodiment, the case where the presence or absence of the friction abnormality or the degree of abnormality is determined using the ratio between the estimated value t_ε and the update timing t as a parameter has been described, but the present invention is not limited to this. . For example, friction abnormality may be determined using a difference between the estimated value t_ε and the update timing t as a parameter.

  In other cases, in the above embodiment, when the number of each element, quantity, quantity, range, etc. is mentioned, unless otherwise specified or clearly specified in principle, that number The invention is not limited to the number mentioned. The structures, steps, and the like described in this embodiment are not necessarily essential to the present invention unless otherwise specified or clearly specified in principle.

10 Engine 12 Cylinder 14 Crank Angle Sensor 16 In-Cylinder Pressure Sensor 20 ECU

Claims (1)

An in-cylinder pressure sensor disposed in a cylinder of the internal combustion engine;
Means for estimating the amount of change in the compression ratio of the internal combustion engine according to the time from the start of stop control of the internal combustion engine to the stop of the internal combustion engine;
Means for calculating an estimated value of the maximum in-cylinder pressure after the start of the stop control according to the estimated amount of change in the compression ratio;
Means for obtaining an actual maximum in-cylinder pressure after the start of the stop control based on an output of the in-cylinder pressure sensor after the start of the stop control;
Means for determining presence or absence of sensitivity abnormality of the in-cylinder pressure sensor, using the actual maximum in-cylinder pressure and the estimated value as parameters;
An abnormality detection device for an in-cylinder pressure sensor, comprising:

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