JP2020033941A - Control device for internal combustion engine - Google Patents

Abstract

To provide a control device for an internal combustion engine capable of suppressing knocking even if deposit adhesion amount increases.SOLUTION: When vibration intensity calculated based on an output signal of a knocking sensor 64 is a knocking determination value or greater, a CPU 52 updates ignition timing to the timing delay side. When deposit accumulation amount is large and the ignition timing is set within a predetermined range on the timing advance side of a compression top dead center, the CUP 52 sets timing delay side updating amount of the ignition timing to a large value.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a control device for an internal combustion engine that controls knocking by manipulating ignition timing.

  For example, Patent Document 1 described below discloses a control device that sets an ignition timing to a retard side when a deposit amount in a cylinder of an internal combustion engine is equal to or more than a predetermined value. Further, in this control device, when knocking occurs, the ignition timing is retarded by feedback control.

JP 2013-60885 A

  By the way, when the ignition timing is within a predetermined range on the advance side from the compression top dead center, even if the ignition timing is retarded by feedback control when knocking occurs, the knocking tends to not be quickly stopped, It has been found by the inventors that this tendency becomes apparent as the amount of deposits increases. Here, the above tendency is that the pressure in the combustion chamber is high near the compression top dead center and the moving speed of the piston becomes slow. It is considered that this is because the amount of decrease in pressure due to the retardation of is reduced.

  In order to solve the above problem, a control device for an internal combustion engine is configured to perform a feedback process of calculating a retard update amount of an ignition timing when knocking has occurred based on an output signal of a knock sensor, and And an operation process for operating an ignition device based on the retarded ignition timing.The feedback process is performed when the amount of deposits in the cylinder of the internal combustion engine is equal to or greater than a predetermined amount and the ignition timing is compressed. If it is within a predetermined range before the top dead center, a process for setting the retard update amount to a larger value as compared with the case where it is not so is included.

  The tendency of the ignition timing to retard the pressure drop and the knocking suppression effect to be small when combustion of the fuel-air mixture occurs near the compression top dead center is apparent when deposits are deposited. Become Therefore, in the above configuration, when the deposit amount is equal to or more than a predetermined amount and the ignition timing is within a predetermined range before the compression top dead center, the retard amount is increased to increase the effect of the pressure by retarding. Can be reduced. Thus, knocking can be suppressed.

FIG. 1 is a diagram showing a control device and an internal combustion engine according to one embodiment. 5 is a flowchart showing a procedure of a process executed by the control device according to the embodiment. The figure which shows the relationship between the crank angle and the temperature in a combustion chamber in the embodiment. The figure which shows the relationship between the ignition timing and the pressure reduction rate in the embodiment.

Hereinafter, an embodiment of a control device for an internal combustion engine will be described with reference to the drawings.
The internal combustion engine 10 shown in FIG. 1 is mounted on a vehicle. In the intake passage 12 of the internal combustion engine 10, a throttle valve 14 and a port injection valve 16 are provided in order from the upstream side. The fuel injected from the port injection valve 16 and the air sucked into the intake passage 12 flow into the combustion chamber 24 defined by the cylinder 20 and the piston 22 with the opening of the intake valve 18. In the combustion chamber 24, a mixture of fuel and air is provided for combustion by spark discharge of an ignition device 26, and energy generated by the combustion is converted into rotational energy of a crankshaft 28 via a piston 22. The air-fuel mixture used for combustion in the combustion chamber 24 is discharged to the exhaust passage 32 as exhaust gas when the exhaust valve 30 is opened. The exhaust passage 32 is provided with a catalyst 34 having an oxygen storage capacity.

  A portion of the exhaust passage 32 upstream of the catalyst 34 is connected to the intake passage 12 by an EGR passage 40. The EGR passage 40 is provided with an EGR valve 42 for adjusting a cross-sectional area of the passage.

  The control device 50 controls the internal combustion engine 10 and controls the internal combustion engine 10 such as the throttle valve 14, the port injection valve 16, the ignition device 26, and the EGR valve 42 in order to control the control amounts such as the torque and the exhaust component ratio. Operate the operation unit. The control device 50 detects the intake air amount Ga detected by the air flow meter 60, the output signal Scr of the crank angle sensor 62, the output signal Sn of the knocking sensor 64, and the intake temperature sensor 66 to control the control amount. The intake air temperature Tin is referred to.

  The control device 50 includes a CPU 52, a ROM 54, and a backup RAM 56. The CPU 52 executes a program stored in the ROM 54 to control the control amount. The backup RAM 56 is a RAM that maintains power even when the main power of the control device 50 is turned off and power is not supplied to the CPU 52 and the like.

  FIG. 2 shows a procedure of a process executed by the control device 50. The process shown in FIG. 2 is realized by the CPU 52 repeatedly executing the program stored in the ROM 54 at, for example, a predetermined cycle. In the following, a step number of each process is represented by a number preceded by “S”.

  In the series of processes shown in FIG. 2, the CPU 52 first determines whether or not the vibration intensity calculated based on the output signal Sn of the knocking sensor 64 is equal to or greater than a knocking determination value (S10). If it is determined that the knocking is equal to or greater than the knocking determination value (S10: YES), the CPU 52 determines that knocking has occurred, and calculates the retarded side update amount Δa of the feedback correction amount KCS according to the rotation speed NE and the charging efficiency η. (S12). Here, the feedback correction amount KCS is an operation amount for operating the ignition timing to the advanced side within a range where knocking can be suppressed by feedback control based on the output signal Sn of the knocking sensor 64. More specifically, the CPU 52 performs a map calculation of the retarded side update amount Δa in a state where map data having the rotational speed NE and the charging efficiency η as input variables and the retarded side update amount Δa as an output variable is stored in the ROM 54 in advance. . The rotation speed NE is calculated by the CPU 52 based on the output signal Scr. The charging efficiency η is calculated by the CPU 52 based on the intake air amount Ga and the rotation speed NE.

  Next, the CPU 52 indicates that the ignition timing Aig when the ignition device 26 was operated last time is equal to or greater than the first timing Af (eg, “20 BTDC”) and equal to or less than the second timing As (eg, “10 BTDC”). It is determined whether the logical product of the condition (A) and the condition (A) that the filling efficiency η is equal to or smaller than the specified value ηth is true (S14). In this embodiment, the ignition timing is set to a larger value as the ignition timing is advanced.

  The condition (A) is a condition in which the ignition timing is such that the combustion temperature of the air-fuel mixture becomes high and the amount of decrease in the pressure in the combustion chamber 24 due to the retardation of the ignition timing is small. FIG. 3 shows the relationship between the crank angle and the temperature in the combustion chamber 24 (in-cylinder temperature). As shown in FIG. 3, as the crank angle approaches the compression top dead center, the in-cylinder temperature increases. For this reason, if ignition occurs near the compression top dead center, the combustion temperature of the air-fuel mixture increases, and knocking is likely to occur. FIG. 3 shows a comparison between the case where no deposit is deposited in the cylinder of the internal combustion engine 10 and the case where deposit is deposited. According to FIG. 3, the in-cylinder temperature is higher after the deposit is deposited than before the deposit, and the tendency becomes more remarkable as approaching the compression top dead center.

  FIG. 4 shows the relationship between the charging efficiency η and the ignition timing, and the relationship between the charging efficiency η and the reduction rate of the pressure P in the combustion chamber 24 when the ignition timing is retarded by a unit crank angle. As shown in FIG. 4, when the ignition timing is between the first timing Af and the second timing As, the ignition timing is retarded compared to when the ignition timing is further retarded. Does not decrease. This is because the moving speed of the piston 22 becomes small immediately before the compression top dead center, and the piston is located near the top dead center when the pressure becomes the highest due to the combustion accompanying ignition, as compared with a later period. That is, the pressure in the combustion chamber 24 cannot be effectively reduced due to the retardation of the ignition timing.

  The upper right of FIG. 4 shows a comparison between the case where the ignition timing is at compression top dead center and the case where the ignition timing is delayed by 2 ° CA from the compression top dead center. In this case, the in-cylinder pressure can be effectively reduced by a slight retard amount (2 ° CA).

On the other hand, the above condition (a) is a condition that knocking is likely to occur due to a large amount of deposits deposited in the cylinders of the internal combustion engine 10.
Returning to FIG. 2, when determining that the logical product is true (S14: YES), the CPU 52 multiplies the delay-side update amount Δa by a correction coefficient Ka having a value equal to or greater than “1”, thereby obtaining the retard angle. The side update amount Δa is corrected (S16). Here, the CPU 52 calculates the correction coefficient Ka to be a larger value when the intake air temperature Tin is high than when it is low. Further, the CPU 52 calculates the correction coefficient Ka to be larger when the third learning value r is larger than when it is smaller. The third learning value r is a learning value for delaying the ignition timing when knocking occurs due to deposit accumulation. The third learning value r takes a value from “0” to “1”. When the third learning value r is large, the ignition timing is set to a more retarded side. In particular, when the third learning value r is “0”, the CPU 52 sets the correction coefficient Ka to “1”. That is, when the third learning value r is “0”, the CPU 52 does not perform the increase correction of the retard side update amount Δa. This is because, in the present embodiment, the purpose of increasing and correcting the retard-side update amount Δa is to suppress knocking caused by deposit accumulation.

  That is, the internal combustion engine 10 according to the present embodiment is designed to have a small volume in the combustion chamber 24 for a high compression ratio. Even if the compression ratio is low, the actual compression ratio greatly changes as compared with the one having a small compression ratio, and knocking is likely to occur. In addition, when the deposit adheres to the piston 22, the heat in the combustion chamber 24 is less likely to be radiated through the piston 22 as compared with the case where the deposit does not adhere. Prone. For this reason, in the present embodiment, knocking is likely to occur due to the adhesion of the deposit, and when there is an ignition timing between the first timing Af and the second timing As, knocking is performed even if the ignition timing is retarded. A problem that was difficult to control became apparent. Therefore, when deposits are attached, the retarded side update amount Δa is increased and corrected, and the retarded side update amount Δa is increased and corrected until the above-mentioned problem does not become apparent, thereby lowering the fuel consumption rate. Or decrease in acceleration performance.

The CPU 52 variably sets the correction coefficient Ka for each cylinder #i (i = 1, 2,...).
The CPU 52 corrects the feedback correction amount KCS to the retard side by subtracting the retardation-side update amount Δa from the feedback correction amount KCS when the process of S16 is completed or when a negative determination is made in the process of S14. (S18).

  On the other hand, when the CPU 52 makes a negative determination in the process of S10, the CPU corrects the feedback correction amount KCS to the advanced side by adding the advanced side update amount Δb to the feedback correction amount KCS (S20). It is desirable that the advance-side update amount Δb is a value smaller than the retard-side update amount Δa.

  When the processing of S18 and S20 is completed, the CPU 52 determines whether or not the charging efficiency η is equal to or less than a specified value ηth (S22). This process is for determining whether or not the region is liable to knock due to a large amount of deposits deposited in the cylinders of the internal combustion engine 10.

  If the CPU 52 determines that it is equal to or smaller than the specified value ηth (S22: YES), “Ab−AR + a1 + a2-r · DL + KCS” is substituted for the ignition timing Aig (S24). Here, the most advanced ignition timing Ab is a timing on the retard side between the MBT ignition timing and the first knock limit point. The MBT ignition timing is an ignition timing at which a maximum torque is obtained (maximum torque ignition timing). The first knock limit point is an advance limit value of the ignition timing (knock limit ignition) at which knocking can be kept within an acceptable level under the assumed best conditions when using a high octane number fuel having a high knock limit. Time).

  The retard difference AR is a difference between the most advanced ignition timing Ab and the second knock limit point. The second knock limit point is an advance limit of the ignition timing (knock limit ignition timing) at which knocking can be kept within an acceptable level when a low octane fuel having a low knock limit is used and no deposit is attached. ). The CPU 52 variably sets the retardation difference AR based on the operating point of the internal combustion engine 10 in view of the fact that the value of the second knock limit point may differ depending on the operating point of the internal combustion engine 10. More specifically, the CPU 52 stores the map data in which the rotational speed NE and the charging efficiency η that define the operating point of the internal combustion engine 10 as input variables and the retardation difference AR as an output variable are stored in the ROM 54 in advance, and the CPU 52 determines the retardation difference. Map the AR.

  The first learning value a1 is a value that is updated so as to reduce the absolute value of the feedback correction amount KCS for each region divided by the rotation speed NE in the full load region. The second learning value a2 is a value that is updated so as to reduce the absolute value of the feedback correction amount KCS for each of the regions divided by the rotation speed NE and the charging efficiency η in the low load region and the medium load region.

  The maximum deposit delay amount DL is a difference between the second knock limit point and the third knock limit point. The third knock limit point is an advance limit of the ignition timing at which knocking can be kept within an acceptable level when a low octane number fuel having a low knock limit is used and a deposit is attached to a maximum assumed amount. Knock limit ignition timing). The CPU 52 variably sets the maximum deposit delay amount DL according to the operating point of the internal combustion engine 10. More specifically, the CPU 52 deposits map data in a state in which the rotational speed NE and the charging efficiency η that define the operating point of the internal combustion engine 10 as input variables and the maximum deposit delay amount DL as an output variable are stored in the ROM 54 in advance. The map calculation of the maximum delay amount DL is performed.

On the other hand, if the CPU 52 determines that it is larger than the specified value ηth (S22: NO), “Ab−AR + a1 + KCS” is substituted for the ignition timing Aig (S26).
When the processing of S24 and S26 is completed, the CPU 52 outputs the operation signal MS3 to the ignition device 26 to operate the ignition device 26 so as to cause the ignition device 26 to generate a spark discharge at the ignition timing Aig (S28).

  Then, the CPU 52 updates the first learning value a1, the second learning value a2, and the third learning value r when the charging efficiency η is equal to or smaller than the specified value ηth, and when the charging efficiency η is larger than the specified value ηth, One learning value a1 is updated (S30). Here, the CPU 52 calculates the learning correction amount KCSs based on the exponential moving average processing value of the feedback correction amount KCS. When the learning correction amount KCSs is equal to or smaller than the specified value ηth and the learning correction amount KCSs is larger than the advance side reference value AB, the CPU 52 sets “KCS-AB” as the learning value update amount, and sets the first learning value a1 and the second learning value. The first learning value a1, the second learning value a2, and the third learning value r are updated such that the sum of the update amounts of the value a2 and “r · DL” becomes “KCS-AB”. When the learning correction amount KCSs is equal to or less than the specified value ηth and the learning correction amount KCSs is smaller than the retardation side reference value AA, the CPU 52 sets “KCSs−AA” as the learning value update amount, and sets the first learning value a1, The first learning value a1, the second learning value a2, and the third learning value r are updated such that the sum of the update amounts of the second learning value a2 and “r · DL” becomes “KCS-AA”.

  On the other hand, when the learning correction amount KCSs is larger than the specified value ηth and the learning correction amount KCSs is larger than the advance side reference value AB, “KCS-AB” is set as the update amount of the first learning value a1, and the first learning value a1 is updated. I do. Further, when the learning correction amount KCSs is larger than the specified value ηth and the learning correction amount KCSs is smaller than the retardation side reference value AA, the CPU 52 sets “KCSs−AA” as an update amount of the first learning value a1, and The learning value a1 is updated.

  Incidentally, when updating the learning value, the CPU 52 executes a process of subtracting the learning value update amount from the learning correction amount KCSs and the feedback correction amount KCS. The first learning value a1, the second learning value a2, and the third learning value r are stored in the backup RAM 56 and updated.

When the process of S30 is completed, the CPU 52 temporarily ends a series of processes illustrated in FIG.
Here, the operation and effect of the present embodiment will be described.

  When the deposit amount is large when the ignition timing is between the first timing Af and the second timing As, the CPU 52 increases the ignition timing retard amount update amount Δa when knocking occurs. Thereby, when the tendency of the knocking suppression effect due to the retardation of the ignition timing to be low when the ignition timing is between the first timing Af and the second timing As becomes apparent due to the accumulation of the deposit, The retard side update amount Δa can be increased. According to the increased retard-side updating amount Δa, knocking can be suppressed because the pressure can be effectively reduced by retarding.

In addition to the increase correction of the retard side update amount Δa, the following countermeasures can be considered to suppress knocking.
Countermeasure 1. An in-cylinder injection valve for injecting fuel into the combustion chamber 24 is provided. The injection timing is set near the compression bottom dead center to suppress a rise in the temperature inside the combustion chamber 24 due to latent heat of vaporization.

Countermeasure 2. An actuator for varying the valve opening timing of the intake valve 18 is provided, and the valve closing timing of the intake valve 18 is delayed to lower the actual compression ratio.
Countermeasure 3. The degree of opening of the EGR valve 42 is increased, and the EGR rate, which is the ratio of the exhaust gas from the EGR passage 40 to the fluid sucked into the combustion chamber 24, is increased.

  Here, in the case of measure 1, the degree of mixing of air and fuel is reduced due to the retarded injection timing, or the amount of fuel adhering to the wall surface of the cylinder 20 is increased, so that the exhaust component is reduced. It may worsen or increase the fuel consumption rate.

  In the case of measure 2, when the closing timing of the intake valve 18 is changed promptly as in the case of the ignition timing, the amount of intake air is not stable. Therefore, once knocking occurs, knocking does not occur. Even so, it takes a longer time to return the valve closing timing of the intake valve 18 than to return the ignition timing to the advanced side. Therefore, the fuel consumption rate increases.

  Further, in the case of the measure 3, since the EGR rate is not stable when the opening degree of the EGR valve 42 is changed quickly like the ignition timing, once the knocking occurs, the knocking does not occur. However, it takes a longer time to restore the opening degree of the EGR valve 42 than to return the ignition timing to the advanced side. For this reason, the exhaust characteristics deteriorate and the fuel consumption rate increases.

In any of the above measures 1 to 3, at least one of the degree of deterioration of the exhaust characteristics and the degree of increase of the fuel consumption rate is larger than in the case of the present embodiment.
<Correspondence>
The correspondence between the items in the above embodiment and the items described in the section of “Means for Solving the Problem” is as follows. The feedback processing corresponds to the processing of S10 to S16, and the operation processing corresponds to the processing of S28.

<Other embodiments>
The present embodiment can be modified and implemented as follows. This embodiment and the following modifications can be implemented in combination with each other within a technically consistent range.

  In the above embodiment, when the affirmative determination is made in the processing of S14, the retard side update amount Δa is corrected by the correction coefficient Ka, but the invention is not limited to this. For example, in place of the process in S14, in addition to the above conditions (A) and (A), whether the logical product of three conditions of a condition that the third learning value r is equal to or greater than a predetermined value is true or not is determined. May be used as map data for performing the map calculation of the retard side update amount Δa. In this case, the value calculated using the map data used when the logical product is true may be larger than the value calculated using the map data used when the logical product is false. To do.

  In the above embodiment, the adhesion of the deposit is grasped by the third learning value r, but is not limited to this. For example, the deposit amount may be estimated according to the rotational speed NE and the charging efficiency η that define the operating point of the internal combustion engine 10. In this case, the CPU 52 determines that the deposit amount is larger when the period during which the low-speed low-load operation region is long is longer than when the period is short. The amount should be small.

  The fuel injection valve is not limited to the port injection valve that injects fuel into the intake passage 12, but may be an in-cylinder injection valve that injects fuel into the combustion chamber 24.

  Reference Signs List 10 internal combustion engine, 12 intake passage, 14 throttle valve, 16 port injection valve, 18 intake valve, 20 cylinder, 22 piston, 24 combustion chamber, 26 ignition device, 28 crankshaft, 30 ... exhaust valve, 32 ... exhaust passage, 34 ... catalyst, 40 ... EGR passage, 42 ... EGR valve, 50 ... control device, 52 ... CPU, 54 ... ROM, 56 ... backup RAM, 60 ... air flow meter, 62 ... crank angle Sensor, 64: knocking sensor, 66: intake air temperature sensor.

Claims (1)

Based on the output signal of the knocking sensor, a feedback process of calculating a retard update amount of the ignition timing when knocking occurs,
Performing an operation process of operating an ignition device based on the ignition timing delayed in accordance with the retard update amount;
The feedback processing is performed when the amount of deposits in the cylinder of the internal combustion engine is equal to or more than a predetermined amount and the ignition timing is within a predetermined range before the compression top dead center. And a control device for the internal combustion engine including a process for setting the retard update amount to a large value.