JP2019183782A - Combustion control system for internal combustion engine - Google Patents

Abstract

Provided is a technique for estimating a deposit amount without directly contacting a sensor with combustion of an internal combustion engine.
A temperature sensor embedded in a wall surface of a combustion chamber without being exposed to a combustion chamber of an internal combustion engine, and a combustion control apparatus for estimating a deposit accumulation amount from a temperature history measured by the temperature sensor. It is set as the structure provided with these.
[Selection] Figure 1

Description

  The present invention relates to a combustion control device for an internal combustion engine.

  A technique for estimating deposit build-up that affects combustion in an internal combustion engine is disclosed. For example, a technique is disclosed in which the actual compression ratio is calculated from the pre-compression pressure and the pre-ignition pressure in the combustion chamber detected by the in-cylinder pressure sensor, and the deposit accumulation amount in the cylinder is estimated from the difference from the design compression ratio ( Patent Document 1). In addition, as a technique for estimating the amount of deposit accumulated on the top land wall surface of the piston, a technique for estimating the deposit amount by integrating the increase / decrease of the deposit according to the top land temperature estimated by the engine operating conditions is disclosed. (Patent Document 2).

Japanese Patent No. 5936367 JP 2016-14380 A

  By the way, in the technique described in Patent Document 1, the amount of deposit is estimated from the change in pressure by the in-cylinder pressure sensor. However, since the sensor provided in the combustion chamber is exposed to combustion, deposit or the like has adhered to the detection unit. In some cases, the detection characteristics change, and the reliability of the measured values may be reduced. In the technique described in Patent Document 2, the in-cylinder temperature is estimated from the operating state, and the amount of increase / decrease in the deposit is estimated and integrated based on the estimated value. The accuracy is inferior.

  One aspect of the present invention is a temperature sensor embedded in a wall surface of the combustion chamber without being exposed to the combustion chamber of an internal combustion engine, and an estimation means for estimating a deposit accumulation amount from a temperature history measured by the temperature sensor. And a combustion control device for an internal combustion engine.

  Here, it is preferable to perform the deposit removing process when the deposit accumulation amount becomes equal to or greater than a reference value.

  Further, it is preferable that the estimation means estimates the deposit accumulation amount based on a phase change of the temperature history with respect to a crank angle of the internal combustion engine. Further, it is preferable that the estimation means estimates the deposit accumulation amount based on a phase change of the temperature peak with respect to a crank angle of the internal combustion engine. At this time, it is preferable that the estimation unit estimates that the deposit accumulation amount is larger as the phase is delayed.

  In addition, it is preferable that the estimation unit estimates the deposit accumulation amount based on a change in the temperature during a combustion cycle of the internal combustion engine. Further, it is preferable that the estimation means estimates the deposit accumulation amount based on a change in the peak value of the temperature during the combustion cycle of the internal combustion engine. At this time, it is preferable that the estimating means estimates that the deposit accumulation amount increases as the temperature decreases.

  ADVANTAGE OF THE INVENTION According to this invention, the technique which estimates the amount of deposits can be provided, without making a sensor contact the combustion of an internal combustion engine directly.

It is a figure which shows the structure of the internal combustion engine and combustion control apparatus in embodiment of this invention. It is a flowchart which shows the combustion control method of the internal combustion engine in embodiment of this invention. It is a figure which shows the example of the temperature history in embodiment of this invention. It is a figure which shows the mode of the accumulation of the deposit on the wall surface of the combustion chamber of an internal combustion engine. It is a figure explaining the phase delay of the change of the temperature in a temperature history. It is a figure which shows the example of the relationship of the phase lag amount of the temperature log | history with respect to the thickness of a deposit. It is a figure explaining the change of the temperature in a temperature history. It is a figure which shows the example of the relationship of the variation | change_quantity of the temperature with respect to the thickness of a deposit.

  An internal combustion engine combustion control apparatus 100 according to an embodiment of the present invention is used by being attached to an internal combustion engine 102 as shown in FIG.

  The internal combustion engine 102 includes a cylinder 10 and a piston 20 that constitute a combustion chamber. An intake port 12 and an exhaust port 16 are provided in the cylinder 10 so as to communicate with each other. The intake port 12 is a passage for supplying air and fuel to the combustion chamber of the internal combustion engine 102. An intake valve 14 is provided between the intake port 12 and the combustion chamber. The intake valve 14 is changed from a closed state to an open state at a timing when air and fuel are supplied to the combustion chamber. The exhaust port 16 is a passage for exhausting exhaust gas from the combustion chamber of the internal combustion engine 102. An exhaust valve 18 is provided between the exhaust port 16 and the combustion chamber. The exhaust valve 18 is changed from a closed state to an open state at a timing when exhaust gas is discharged from the combustion chamber. The piston 20 is a member for obtaining power by being moved up and down by combustion of fuel in the combustion chamber. The fuel injection valve 22 includes a valve for injecting fuel from the injection hole, and injects fuel into the intake port 12 at a desired timing.

  Combustion control device 100 is connected to temperature sensor 30. The temperature sensor 30 is a sensor that measures and outputs a temperature. As shown in FIG. 1, the temperature sensor 30 is embedded in a cylinder 10 that constitutes a wall surface of the combustion chamber without being exposed to the combustion chamber of the internal combustion engine 102. At this time, it is preferable to embed the temperature sensor 30 in the vicinity of the wall surface where deposits are likely to accumulate in the combustion chamber of the internal combustion engine 102. The combustion control device 100 estimates the amount of deposits (such as soot generated by combustion) accumulated on the wall surface of the combustion chamber of the internal combustion engine 102 based on the temperature measured by the temperature sensor 30, and deposits according to the amount. Perform the removal process.

  Hereinafter, the combustion control method of the internal combustion engine 102 in the present embodiment will be described with reference to the flowchart of FIG. Combustion control includes processing for estimating the amount of deposit accumulated in the combustion chamber in a state where the internal combustion engine 102 is operated and removing the deposit.

  In step S10, the temperature is measured by the temperature sensor 30. Combustion control device 100 receives the temperature measured by temperature sensor 30 and stores it as a temperature history in a built-in memory.

  Here, as shown in FIG. 3, in a state where the internal combustion engine 102 is being operated, the temperature measured by the temperature sensor 30 changes in accordance with a change in the crank angle indicating the movement of the piston. That is, near the top dead center (TDC), the combustion of the fuel is started, the temperature in the combustion chamber rises, the wall surface temperature of the combustion chamber rises, and the temperature measured by the temperature sensor 30 rises accordingly. Thereafter, the temperature reaches a peak near the top dead center (TDC). When the combustion in the combustion chamber ends, the crank angle advances and the wall surface temperature of the combustion chamber also decreases, and the temperature measured by the temperature sensor 30 also decreases accordingly. The temperature measured by the temperature sensor 30 shows such a change every cycle of the internal combustion engine 102. In FIG. 3, an example of the temperature change in the initial state is shown by a solid line, and an example of the temperature change as the deposit accumulation amount increases is shown in the order of a broken line and a dotted line.

  The temperature measurement by the temperature sensor 30 may be performed when the internal combustion engine 102 is operated under a predetermined condition. For example, the temperature may be measured by the temperature sensor 30 when the internal combustion engine 102 is started, idling, or the like. The predetermined operating condition may be one operating condition or a plurality of operating conditions.

  In step S12, a process of estimating the deposit amount is performed. By the processing in this step, the combustion control device 100 functions as an estimation unit.

  When the combustion of the fuel in the internal combustion engine 102 is repeated, deposits accumulate on the wall surface of the combustion chamber as the operation time of the internal combustion engine 102 elapses, as shown in FIG. Since the deposit has a heat shielding effect, the phase of the temperature change with respect to the crank angle of the internal combustion engine 102 is delayed as the deposit accumulation amount increases as shown in FIG. The phase of the temperature change can be read as, for example, the amount of change in the phase of the temperature peak with respect to the crank angle of the internal combustion engine 102.

  Combustion control apparatus 100 can estimate the amount of deposit accumulation based on the phase delay amount Δθ of the temperature history with respect to the crank angle of internal combustion engine 102. FIG. 6 shows an example of the relationship between the phase delay amount Δθ of the temperature history with respect to the deposit thickness d. As shown in FIG. 6, when the deposit thickness d increases, the phase delay amount Δθ in the temperature history also increases. However, as shown in FIG. 6, the relationship is not limited to a linear relationship, and the relationship changes depending on the configuration and structure of the internal combustion engine 102. Therefore, a relationship between the phase delay amount Δθ of the temperature history with respect to the deposit thickness d is obtained in advance for each internal combustion engine 102 by experiments or the like and stored in a memory accessible from the combustion control device 100. It is possible to estimate the thickness d of the deposit in accordance with the phase delay amount Δθ of the actually measured temperature history.

  Further, as the deposit accumulation amount increases, the temperature during the combustion cycle of the internal combustion engine 102 changes as shown in FIG. That is, the temperature at a specific crank angle in the combustion cycle of the internal combustion engine 102 changes from cycle to cycle. For example, it can be read as the change amount ΔT of the temperature peak value during the combustion cycle.

  Further, the combustion control device 100 can estimate the deposit accumulation amount based on the temperature change amount ΔT during the combustion cycle of the internal combustion engine 102. FIG. 8 shows an example of the relationship between the change amount ΔT of the temperature and the thickness d of the deposit. As shown in FIG. 8, when the deposit thickness d increases, the temperature change ΔT decreases. However, as shown in FIG. 8, the relationship is not limited to a linear relationship, and the relationship changes depending on the configuration and structure of the internal combustion engine 102. Therefore, the relationship between the change amount ΔT of the temperature and the deposit thickness d is obtained in advance for each internal combustion engine 102 by experiments or the like, and is stored in a memory accessible from the combustion control device 100 to actually It is possible to estimate the thickness d of the deposit in accordance with the measured temperature change ΔT.

  In the present embodiment, the deposit thickness d is used as the deposit accumulation amount, but the present invention is not limited to this, and the phase delay amount Δθ of the temperature history and the temperature The same relationship as the change amount ΔT is shown.

  In step S14, it is determined whether or not the estimated deposit accumulation amount is equal to or greater than the start reference value. In the present embodiment, combustion control apparatus 100 shifts the process to step S16 if the deposit thickness d estimated in step S12 is equal to or greater than the start reference thickness Ds, and otherwise proceeds to step S20. Transition.

  Here, as the deposit accumulation amount used for the determination, an amount estimated from the phase lag amount Δθ of the temperature history may be used, or an amount estimated from the temperature change amount ΔT may be used. Moreover, you may use both of these. For example, an average value of the deposit accumulation amount estimated from the phase delay amount Δθ of the temperature history and the deposit accumulation amount estimated from the temperature change amount ΔT may be used as the deposit accumulation amount. Further, for example, a larger value may be used as the deposit accumulation amount for the determination between the deposit accumulation amount estimated from the phase lag amount Δθ of the temperature history and the deposit accumulation amount estimated from the temperature change amount ΔT.

  In step S16, deposit removal processing is performed. The combustion control device 100 changes the operating conditions of the internal combustion engine 102 and removes deposits accumulated on the wall surface of the combustion chamber. Specifically, the combustion control apparatus 100 accumulates on the wall surface of the combustion chamber using the fuel injection timing, fuel ignition timing, fuel injection pressure, supercharging pressure, supplied air amount, EGR rate, and the like as control parameters. The operating conditions are such that the deposit is removed. A plurality of these control parameters may be combined.

  In the present embodiment, the deposit removal process is performed according to the deposit accumulation amount, but the present invention is not limited to this. For example, a warning may be issued when the deposit accumulation amount exceeds a reference value.

  In step S18, the end of the deposit removal process is determined. Here, it is determined whether or not the deposit accumulation amount is equal to or less than the end reference value. The end reference value is smaller than the start reference value. In the present embodiment, combustion control apparatus 100 shifts the process to step S20 if deposit thickness d is equal to or smaller than end reference thickness De by the deposit removal process, and otherwise removes deposit removal process in step S16. To continue. At this time, the deposit amount can be estimated by the same processing as in steps S10 and S12.

  In step S20, the internal combustion engine 102 is set to a normal operation. The combustion control device 100 controls the internal combustion engine 102 so as to satisfy normal operating conditions.

  As described above, according to combustion control apparatus 100 in the present embodiment, it is possible to estimate the deposit accumulation amount without bringing temperature sensor 30 into direct contact with the combustion of internal combustion engine 102. A process for removing the deposit can be applied based on the deposit accumulation amount.

10 cylinder, 12 intake port, 14 intake valve, 16 exhaust port, 18 exhaust valve, 20 piston, 22 fuel injection valve, 30 temperature sensor, 100 combustion control device, 102 internal combustion engine.

Claims (8)

A temperature sensor embedded in the wall of the combustion chamber without being exposed to the combustion chamber of the internal combustion engine;
Estimating means for estimating a deposit accumulation amount from a history of temperatures measured by the temperature sensor;
A combustion control device for an internal combustion engine, comprising: A combustion control device for an internal combustion engine according to claim 1,
A combustion control apparatus for an internal combustion engine, which performs a deposit removal process when the deposit accumulation amount becomes equal to or greater than a reference value. A combustion control device for an internal combustion engine according to claim 1 or 2,
The combustion control apparatus for an internal combustion engine, wherein the estimation means estimates the deposit accumulation amount based on a phase change of the temperature history with respect to a crank angle of the internal combustion engine. A combustion control device for an internal combustion engine according to claim 3,
The combustion control apparatus for an internal combustion engine, wherein the estimation means estimates the deposit accumulation amount based on a phase change of the temperature peak with respect to a crank angle of the internal combustion engine. A combustion control device for an internal combustion engine according to claim 3 or 4,
The combustion control apparatus for an internal combustion engine, wherein the estimation means estimates that the deposit accumulation amount increases as the phase delays. A combustion control device for an internal combustion engine according to claim 1 or 2,
The combustion control apparatus for an internal combustion engine, wherein the estimation means estimates the deposit accumulation amount based on a change in the temperature during a combustion cycle of the internal combustion engine. A combustion control apparatus for an internal combustion engine according to claim 6,
The combustion control apparatus for an internal combustion engine, wherein the estimation means estimates the deposit accumulation amount based on a change in a peak value of the temperature during a combustion cycle of the internal combustion engine. A combustion control device for an internal combustion engine according to claim 6 or 7,
The combustion control apparatus for an internal combustion engine, wherein the estimation means estimates that the deposit accumulation amount increases as the temperature decreases.