JP5971230B2 - Abnormality determination device for internal combustion engine - Google Patents

Description

  The present invention relates to an abnormality determination device for an internal combustion engine.

  2. Description of the Related Art Conventionally, a diagnostic device that detects an abnormality occurring in an internal combustion engine is known. For example, Patent Document 1 discloses a configuration for determining a cylinder in which compression pressure is insufficient, that is, so-called compression loss occurs in a cranking rotation state in which a crankshaft is rotated while fuel supply to a cylinder and ignition are stopped. It is disclosed. This compression loss determination is based on the principle that when an abnormality in which the compression pressure decreases occurs in the cylinder, the fluctuation of the angular speed of the crankshaft during cranking rotation increases.

JP 2012-202241 A

  By the way, as a cause of the compression loss, there is a decrease in the sealing performance of the cylinder due to mechanical factors such as damage to the piston ring or failure of the valve system. Further, when the deposit bites into the intake valve or the exhaust valve, the valve closing is hindered, and the sealing performance of the cylinder cannot be maintained. Since such deposit biting occurs suddenly during engine operation, even if the cranking rotation state is generated after the engine operation is stopped, the loss of compression due to such bite biting is reproduced. It ’s difficult. Therefore, as disclosed in Patent Document 1, in the diagnostic device that determines the cylinder in which the compression loss is generated by generating the cranking rotation state, the presence or absence of the occurrence of the compression loss based on highly reproducible mechanical factors. However, it is not possible to determine whether or not a compression loss due to the bite of the deposit has occurred during engine operation.

  The present invention has been made in view of such circumstances, and an object thereof is to provide an abnormality determination device that can determine the occurrence of compression loss during normal engine operation in which combustion is performed. There is.

Hereinafter, means for solving the above-described problems and the effects thereof will be described.
An abnormality determination device for an internal combustion engine for solving the above problem includes a calculation unit that calculates an angular acceleration of a crankshaft of the internal combustion engine, and a determination unit that determines that compression loss has occurred. In this abnormality determination device, the calculation unit calculates the angular acceleration during engine operation, and the determination unit has a negative value for the angular acceleration calculated by the calculation unit in an expansion stroke, and expansion When the angular acceleration calculated by the calculation unit in the stroke continuously decreases from the compression top dead center until the determination period elapses, it is determined that a compression loss has occurred.

  If no compression loss occurs and compression is normally performed in the compression stroke, the angular velocity of the crankshaft increases in the expansion stroke with combustion. Therefore, in this case, the angular acceleration of the crankshaft becomes a positive value during the expansion stroke.

  However, since combustion does not occur when compression loss occurs, the angular velocity of the crankshaft does not increase during the expansion stroke. In addition, since the negative pressure acts on the combustion chamber during the expansion stroke, the angular velocity of the crankshaft decreases. Therefore, when compression loss occurs, the angular acceleration of the crankshaft becomes a negative value during the expansion stroke.

  Even if no compression loss occurs, combustion does not occur if misfire occurs. However, if compression loss has not occurred, even if combustion has not occurred, air compressed in the compression stroke expands in the expansion stroke, and the piston is pushed back by the repulsive force. The angular speed of the crankshaft will increase. Therefore, in this case, the angular acceleration of the crankshaft becomes a positive value during the expansion stroke.

  In the above configuration, since the compression loss determination is performed based on the positive / negative of the angular acceleration of the crankshaft during the expansion stroke during the engine operation, occurrence of the compression loss can be determined during the normal engine operation.

  If the load acting on the crankshaft of the internal combustion engine is large, the angular velocity of the crankshaft is unlikely to increase when misfire occurs. Therefore, when it is determined whether or not the compression loss has occurred based only on whether or not the angular acceleration of the crankshaft in the expansion stroke is a negative value, a state in which a large load is acting When a misfire occurs, there is a risk that it is erroneously determined that a compression loss has occurred even though a compression loss has not occurred.

  Therefore, in the above configuration, in addition to the negative value of the angular acceleration of the crankshaft in the expansion stroke, the angular acceleration of the crankshaft in the expansion stroke continues from the compression top dead center until the determination period elapses. Therefore, it is determined that the compression loss has occurred based on the decrease.

  When compression loss occurs, repulsive force due to compressed air is less likely to occur in the compression stroke, and negative pressure is generated in the combustion chamber after passing through compression top dead center. As a result, the angular acceleration of the crankshaft continues to decrease. On the other hand, when a misfire occurs in a state where a compression loss has not occurred and a large load is acting, a repulsive force is generated by the compressed air in the compression stroke. Therefore, compared to the case where compression loss has occurred, the angular acceleration of the crankshaft is less likely to decrease even after passing through the compression top dead center, and the angular acceleration continues to decrease compared to when compression loss has occurred. It takes time to become.

  Therefore, as in the above configuration, the compression loss occurs based on the fact that the angular acceleration of the crankshaft in the expansion stroke continuously decreases from the compression top dead center until the determination period elapses. If it is determined, it is possible to determine the state in which the action of the repulsive force due to the compressed air is less likely to occur, and to determine that the compression loss has occurred. Therefore, when misfire occurs in a state where a large load is applied, it is possible to suppress erroneous determination that compression loss has occurred even though compression loss has not occurred. You can also.

The block diagram which shows the functional structure of the electronic control unit which is one Embodiment of the abnormality determination apparatus of an internal combustion engine. The flowchart which shows the process sequence of the compression loss determination routine which the electronic control unit performs. (A) is a timing chart which shows the change of angular velocity (omega), (B) is a timing chart which shows the change of angular acceleration (alpha).

  Hereinafter, an embodiment in which an internal combustion engine abnormality determination device is embodied in an electronic control unit 10 that controls an internal combustion engine mounted on a vehicle will be described with reference to FIGS. 1 to 3. Note that the internal combustion engine controlled by the electronic control unit 10 in this embodiment is an in-line four-cylinder engine having four cylinders.

  As shown in FIG. 1, the electronic control unit 10 is connected to a crank angle sensor 20 that outputs a crank angle signal corresponding to a change in the crank angle that is the rotation angle of the crankshaft of the internal combustion engine. The electronic control unit 10 includes a calculation unit 11 that calculates an angular velocity ω of the crankshaft and an angular acceleration α of the crank angle based on the crank angle signal output from the crank angle sensor 20. Furthermore, the electronic control unit 10 includes a determination unit 12 that determines that compression loss has occurred in the internal combustion engine, and a storage unit 13 that stores the number of times it has been determined that compression loss has occurred.

  Next, the processing procedure of the compression loss determination routine executed by the electronic control unit 10 will be described with reference to FIG. This determination routine is repeatedly executed every time the crank angle is advanced by 30 ° CA.

In the following description, the compression top dead center is referred to as TDC, and the crank angle is expressed with TDC as 0 ° CA. Further, the expansion bottom dead center is referred to as BDC.
When this determination routine is started, first, in step S100, it is determined whether or not a precondition for determination of compression loss is satisfied. Here, (1) the crank angle sensor 20 is operating normally, (2) the amount of operation of the accelerator pedal of the vehicle on which the internal combustion engine is mounted is “0”, and (3) the vehicle speed is “0”. (4) that the internal combustion engine is in an idling state is set as a precondition. When any of the preconditions (1) to (4) is not satisfied, it is determined in step S100 that the precondition is not satisfied (S100: NO), and this determination routine is temporarily terminated. .

  On the other hand, when all of the preconditions (1) to (4) are satisfied, it is determined in step S100 that the precondition is satisfied (S100: YES), and the processing after step S110 is performed.

  In step S <b> 110, the calculation unit 11 calculates the angular acceleration α based on the crank angle signal input from the crank angle sensor 20. That is, in this step S110, the calculation unit 11 calculates the angular velocity ω of the crankshaft by differentiating the crank angle grasped based on the crank angle signal, and further calculates the angular acceleration α by differentiating the angular velocity ω. .

  Next, in step S120, it is determined whether or not the angular acceleration α in the expansion stroke after TDC is a negative value. When the determination timing at this time is not the expansion stroke, or when the angular acceleration α is not a negative value even in the expansion stroke (S120: NO), this determination routine is once ended.

On the other hand, when the angular acceleration α in the expansion stroke after TDC is a negative value (S120: YES), the processing after step S130 is performed.
In step S130, it is determined whether or not the angular acceleration α continuously decreases during the determination period.

  In step S130, the angular acceleration α calculated in step S110 is compared with the angular acceleration α ′ calculated in step S110 in the previous routine, and it is determined whether α ′> α is satisfied. Determined. That is, it is determined whether or not the angular acceleration α decreases with the advance of the crank angle. When the determination that the angular acceleration α is decreasing is performed twice consecutively, it is determined that the angular acceleration α is continuously decreasing.

  However, the determination period is a period in which the crank angle is from 0 ° CA to 90 ° CA. That is, the period from when the TDC is passed until this determination routine is performed three times is the determination period. In this step S130, during the determination period after the TDC is passed until the determination routine is completed three times. If it is determined that the angular acceleration α is continuously decreasing, an affirmative determination is made. On the other hand, if it is not determined that the angular acceleration α has continuously decreased during the determination period after passing through the TDC and until this determination routine is completed three times, a negative determination is made.

If a negative determination is made in step S130 (S130: NO), this determination routine is once terminated.
On the other hand, when an affirmative determination is made in step S130 (S130: YES), that is, when it is determined that the angular acceleration α is continuously decreasing from the TDC until the determination period elapses, compression loss occurs. It is determined that the process is being performed, and the process of step S140 is performed.

  In step S140, one compression loss counter that stores the number of compression loss in the storage unit 13 is added. When the compression loss counter is added in this way, this determination routine is once terminated.

  Next, changes in the angular velocity ω and the angular acceleration α in the expansion stroke from TDC to BDC will be described with reference to FIG. 3A shows a change in the angular velocity ω of the crankshaft, and FIG. 3B shows a change in the angular acceleration α of the crankshaft. A thin line L11 in FIG. 3A indicates a change in the angular velocity ω in a normal state where no compression loss occurs, and a thin line L21 in FIG. 3B indicates a change in the angular acceleration α at that time. Yes. In addition, a two-dot chain line L12 in FIG. 3A shows a change in the angular velocity ω in a state where misfire has occurred due to an abnormality such as a fuel injection system or an ignition system, although compression loss has not occurred. A two-dot chain line L22 in FIG. 3B indicates a change in the angular acceleration α at that time. The alternate long and short dash line L13 indicates a change in the angular velocity ω in a state where misfire occurs and a large load is applied to the internal combustion engine, although compression loss does not occur. A chain line L23 indicates a change in the angular acceleration α at that time. A thick line L14 in FIG. 3A shows a change in angular velocity ω in a state where compression loss occurs, and a thick line L24 in FIG. 3B shows a change in angular acceleration α at that time. Yes.

  When compression loss has not occurred and combustion has occurred normally, as indicated by a thin line L11 in FIG. 3A, the angular velocity ω increases in the range of 60 ° CA from TDC. The increase in the angular velocity ω is accompanied by generation of torque due to combustion of the compressed air-fuel mixture. Therefore, as shown in FIG. 3B, the angular acceleration α at this time temporarily becomes a positive value.

  In addition, even when misfire occurs, the angular velocity ω increases in the range of 60 ° CA from TDC as indicated by a two-dot chain line L12 in FIG. Therefore, as shown in FIG. 3B, the angular acceleration α at this time also temporarily becomes a positive value. This is due to the repulsive force generated as the air compressed in the compression stroke expands in the expansion stroke. That is, although no combustion has occurred due to the occurrence of misfire, since the compression loss has not occurred, the piston is pushed back by the repulsive force generated when the compressed air in the cylinder expands, and the angular velocity ω increases. is there. However, in this case, since a large torque due to combustion cannot be obtained, the angular acceleration α is an angle in a state in which normal combustion occurs as indicated by a thin line L21 as indicated by a two-dot chain line L22 in FIG. It becomes lower than the acceleration α. Therefore, the degree of the increase in the angular velocity ω indicated by the two-dot chain line L12 in FIG. 3A is also compared with the change in the angular velocity ω in the state where the combustion normally occurs, which is indicated by the thin line L11 in FIG. It is getting smaller.

  In addition, when misfire occurs and a large load is applied to the internal combustion engine, the angular velocity ω does not increase even after passing through the TDC as shown by a one-dot chain line L13 in FIG. It gradually decreases until reaching BDC. This is because the load acting on the internal combustion engine works so as to cancel the repulsive force. Therefore, the angular acceleration α at this time does not become a positive value as shown by a one-dot chain line L23 in FIG. 3B, but after maintaining a substantially constant level in the range of 30 ° CA to 90 ° CA. It decreases from 90 ° CA. That is, the angular acceleration α is always a negative value after passing through the TDC.

  On the other hand, when the compression loss occurs, air escapes from the combustion chamber in the compression stroke, and thus the repulsive force due to air as described above hardly occurs in the expansion stroke. Furthermore, when passing through the TDC, the piston descends in a state where it is difficult for air to flow into the combustion chamber, and a negative pressure is generated in the combustion chamber. Therefore, when compression loss occurs, the angular velocity ω continues to decrease immediately after passing through the TDC, as indicated by the thick line L14 in FIG. Therefore, the angular acceleration α at this time is always a negative value as shown by a thick line L24 in FIG. 3B, and the timing at which the angular acceleration α continues to decrease (at 30 ° CA in FIG. 3B). The timing is earlier than the case of the two-dot chain line L22 and the one-dot chain line L23 in which compression loss does not occur (the timing at 90 ° CA in FIG. 3B).

Next, the effect produced by repeatedly executing the compression loss determination routine described with reference to FIG. 2 will be described with reference to FIGS.
As described above, a normal case where compression loss has not occurred (in the case of the thin line L21 in FIG. 3B) and a case where misfire has occurred and a large load is not acting (FIG. 3B). In L22), the angular acceleration α in the expansion stroke after TDC temporarily becomes a positive value. Therefore, in these cases, when the angular acceleration α is a positive value, the compression loss determination routine shown in FIG. 2 is executed, and when the process proceeds to step S120, a negative determination is made by the determination in step S120. The determination routine is terminated without determining that the compression loss has occurred. Even in these cases, as shown in FIG. 3B, the angular acceleration α becomes a negative value after 90 ° CA, but at this time, the determination period is ended, so that the determination in step S120 is positive. Even if the determination is made, a negative determination is made in step S130. Accordingly, in this case as well, the determination routine is terminated without determining that compression loss has occurred. As described above, when there is a normal case where no compression loss has occurred and when a misfire has occurred and a large load is not acting, a negative determination is made in step S120 or step S130, and a compression loss determination routine is performed. It is not determined that compression loss has occurred.

  On the other hand, when a misfire has occurred and a large load is acting on the internal combustion engine (in the case of the alternate long and short dash line L23 in FIG. 3B), the angular acceleration α in the expansion stroke after the TDC is always as described above. Negative value. Therefore, in this case, when the compression loss determination routine shown in FIG. 2 is executed and the process proceeds to step S120, an affirmative determination is made by the determination in step S120, and the process proceeds to step S130. However, in this case, since the repulsive force is generated by the compressed air as described above, the angular acceleration α is almost in the range of 30 ° CA to 90 ° CA as shown by a one-dot chain line L23 in FIG. After maintaining a certain level, it begins to drop from 90 ° CA. Therefore, in this case, since the angular acceleration α does not continuously decrease during the determination period up to 90 ° CA, a negative determination is made in step S130. Accordingly, in this case as well, the determination routine is terminated without determining that compression loss has occurred. As described above, when a misfire occurs and a large load is applied to the internal combustion engine, a negative determination is made in step S130. In this case as well, a compression loss occurs through the compression loss determination routine. It is not determined to be.

  On the other hand, when the compression loss occurs (in the case of the thick line L24 in FIG. 3B), as described above, the angular acceleration α in the expansion stroke after the TDC is always a negative value. Therefore, in this case, when the compression loss determination routine shown in FIG. 2 is executed and the process proceeds to step S120, an affirmative determination is made by the determination in step S120, and the process proceeds to step S130. When the compression loss occurs, the repulsive force due to air as described above is unlikely to occur, and a negative pressure is generated in the combustion chamber during the expansion stroke. Therefore, the angular acceleration α starts to decrease from around 30 ° CA. . Accordingly, an affirmative determination is made in step S130 while the determination routine is repeatedly executed.

  Specifically, when compression loss occurs, the angular acceleration α continues to decrease after 30 ° CA, as indicated by a thick line L24 in FIG. Therefore, when the determination routine is executed at 60 ° CA, the angular acceleration α30 at the time of 30 ° CA is compared with the angular acceleration α60 at the time of 60 ° CA in step S130, and it is determined that the angular acceleration α has decreased. Is done. However, since this decrease determination is the first determination, a negative determination is made in step S130 at this time. At this time, it is not determined that a compression loss has occurred, and the determination routine is temporarily terminated.

  Subsequently, when the determination routine is executed at 90 ° CA, the angular acceleration α60 at 60 ° CA and the angular acceleration α90 at 90 ° CA are compared in step S130, and the angular acceleration α decreases. It is determined that Since the decrease determination at this time is the second decrease determination that is continuous with the previous decrease determination, it is determined that the angular acceleration α is continuously decreasing at this time. As a result, since it is determined that the angular acceleration α continuously decreases in the determination period up to 90 ° CA, an affirmative determination is made.

  When compression loss has occurred in this way, an affirmative determination is made in step S130 while repeating the determination routine, it is determined that compression loss has occurred, and a compression loss counter is added in step S140. Become so.

  That is, according to this compression loss determination routine, the state in which the angular velocity ω is less likely to increase due to the action of the load and the repulsive force due to the compressed air are less likely to occur due to the continuous decrease determination of the angular acceleration α in step S130. It is possible to discriminate from the state in which compression loss is occurring.

According to the embodiment described above, the following effects can be obtained.
(1) Since the compression loss determination is performed based on the angular acceleration α of the crankshaft during the expansion stroke during engine operation, the occurrence of compression loss can be determined during normal engine operation.

  (2) The crankshaft angular acceleration α in the expansion stroke is compressed to determine that compression loss has occurred based on continuously decreasing between TDC and 90 ° CA. It is possible to determine a state in which the action of repulsive force due to air is less likely to occur, and to determine that compression loss has occurred. Therefore, when misfire occurs in a state where a large load is applied, it is possible to suppress erroneous determination that compression loss has occurred even though compression loss has not occurred. Can do.

  (3) Since the number of times determined that compression loss has occurred is stored in the storage unit 13, the state of the internal combustion engine can be grasped based on the determined number. When maintaining the internal combustion engine, the state of the internal combustion engine can be determined by referring to the information stored in the storage unit 13, and an appropriate response according to the state of the internal combustion engine can be performed.

  (4) Since the compression loss determination is performed during the idling operation, it is possible to determine the compression loss without being affected by the fluctuation of the angular acceleration α due to the change in the driving state. Therefore, the determination accuracy can be improved.

In addition, the said embodiment can also be implemented with the following forms which changed this suitably.
In the above-described embodiment, in the process of step S100, it is included in the compression loss determination precondition that the internal combustion engine is in the idling operation state, but it is not necessary to include the idling operation state in the precondition. If it is in the idling operation state, the determination accuracy of the compression loss is improved, but the compression loss determination can be performed even if it is not in the idling operation state. Since the preconditions are relaxed, opportunities for performing compression loss determination can be increased.

  In the above embodiment, four preconditions are set in the process of step S100, but other conditions may be set. Alternatively, the preconditions may be reduced as appropriate. Further, the processing after step S110 is performed when all the preconditions are satisfied, but the present invention is not limited to this. For example, the processing after step S110 may be performed when three of the four preconditions are satisfied.

  In the above embodiment, the determination period in step S130 is the period from the crank angle from 0 ° CA to 90 ° CA, and the period until the decrease determination of the angular acceleration α is performed three times after passing through the TDC. The determination period may be set. For example, even if a determination period such as a period until the crank angle changes by a predetermined amount after passing the TDC, or a period until a predetermined time elapses after passing the TDC, the angular acceleration α in the first half of the expansion stroke is set. Can be determined.

  -It may replace with the structure which sets a determination period like the said embodiment, and you may make it restrict | limit the period which performs the compression loss determination routine in the said embodiment. For example, the execution period of the compression loss determination routine is set to 90 ° CA from TDC, and when the routine processing at 90 ° CA ends, the compression loss determination routine is not performed until the TDC of another cylinder arrives. Also good. In this case, in step S130, whether or not the compression loss has occurred can be determined by determining whether or not the angular acceleration α is continuously decreasing regardless of whether or not the determination period is in progress. .

  -It may be determined that an abnormality has occurred in the internal combustion engine by the compression loss determination in the above embodiment. Further, it may be determined that an abnormality has occurred in the internal combustion engine when the value of the compression loss counter becomes equal to or greater than a predetermined value. Furthermore, the operation of the internal combustion engine can be stopped when it is determined that an abnormality has occurred in the internal combustion engine.

  As shown by a two-dot chain line in FIG. 1, a display unit 30 that displays the number of compression loss determinations stored in the storage unit 13 may be connected to the electronic control unit 10. Since the compression loss determination can be visualized, the driver of the vehicle equipped with the internal combustion engine can know the occurrence of the compression loss during driving. Moreover, you may display on the display part 30 that abnormality has generate | occur | produced in the internal combustion engine.

  In the above embodiment, the abnormality determination device employed in the in-line four-cylinder engine having four cylinders is illustrated, but the number of cylinders of the internal combustion engine that can perform the compression loss determination is not limited to four. For example, the compression loss determination can be performed even in the case of six cylinders. However, in the above-described embodiment, the period until the decrease determination of the angular acceleration α performed at 30 ° CA intervals is performed three times after passing through the TDC, that is, the period from 0 ° CA to 90 ° CA is set as the determination period. However, this is limited to the case of a four-cylinder internal combustion engine. The combustion interval in each cylinder becomes shorter as the number of cylinders increases. For this reason, if the internal combustion engine is configured to determine the compression loss by setting a fixed determination period, the angular acceleration α fluctuates due to combustion occurring in another cylinder, and the continuous decrease in the angular acceleration α is accurately detected. May not be able to be determined. Therefore, in order to improve the accuracy of the compression loss determination, it is necessary to set the determination period while avoiding a period that is susceptible to the fluctuation of the angular acceleration α due to the combustion of another cylinder.

  As described above, when an internal combustion engine having a different number of cylinders is employed, it is preferable to set a determination period for performing a continuous decrease determination of the angular acceleration α according to the number of cylinders. In the case of six cylinders, since the combustion interval in each cylinder is 120 ° CA, the determination period may be set in a range within 120 ° CA from TDC.

  In the above embodiment, the compression loss determination routine is executed every time the CA is advanced by 30 ° CA. However, the interval for executing the compression loss determination routine may be changed as appropriate. In this case, when the determination period is set according to the number of executions of the determination routine, the set number is changed. In order to secure an opportunity to perform the compression loss determination, it is preferable to set a short interval for executing the determination routine.

  DESCRIPTION OF SYMBOLS 10 ... Electronic control unit, 11 ... Calculation part, 12 ... Determination part, 13 ... Memory | storage part, 20 ... Crank angle sensor, 30 ... Display part.

Claims (1)

An internal combustion engine abnormality determination device for determining abnormality of an internal combustion engine,
A calculation unit for calculating an angular acceleration of a crankshaft of the internal combustion engine;
A determination unit that determines that compression loss has occurred,
The calculation unit calculates the angular acceleration during engine operation,
The determination unit is configured such that the angular acceleration calculated by the calculation unit in the expansion stroke is a negative value, and the angular acceleration calculated by the calculation unit in the expansion stroke is from the compression top dead center until the determination period elapses. An abnormality determination device for an internal combustion engine that determines that compression loss has occurred when the pressure continuously decreases in between.