JP2005098186A - Operation area control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an operation area control device of an internal combustion engine, capable of improving fuel consumption, and capable of reducing a generation quantity of NOx, by expanding a compression ignition operation area, so as to vary the compression ignition operation area in response to atmospheric pressure. <P>SOLUTION: This internal combustion engine can perform both spark ignition operation and compression ignition operation, and has an atmospheric pressure detecting means 29 for detecting the atmospheric pressure, an operation state detecting means for detecting an operation state provided for determining the compression ignition operation area, a limit value deriving means for deriving a compression ignition operation limit value of the operation state corresponding to the atmospheric pressure detected by the atmospheric pressure detecting means 29, an operation area determining means for determining whether or not to be in the compression ignition operation area, by comparing the compression ignition operation limit value derived by the limit value deriving means with the operation state detected by the operation state detecting means, and an operation area setting mean for setting the internal combustion engine in compression ignition operation, when the operation area determining means determines to be in the compression ignition operation area. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an apparatus for controlling an operation region in an internal combustion engine capable of both a spark ignition operation and a compression ignition operation.

  According to the compression ignition operation in which the air-fuel mixture supplied to the internal combustion engine is combusted by compression ignition (compression self-ignition), a high compression ratio results in good fuel efficiency and realizes relatively stable combustion even when the air-fuel ratio is lean. Moreover, since the combustion temperature is relatively low, the amount of NOx generated can be reduced.

In order to cause compression ignition, it is necessary to raise the gas temperature in the combustion chamber to a predetermined temperature or higher, and therefore, internal EGR using exhaust heat is generally employed.
The internal EGR is realized by so-called minus overlap control that closes the exhaust valve early in the middle of the exhaust stroke and opens the intake valve late in the middle of the intake stroke.

  That is, by closing the exhaust valve earlier and opening the intake valve later, a part of the combustion gas is confined in the combustion chamber near the intake top dead center, and mixed with the intake of the next cycle as residual gas (internal EGR gas). The gas temperature is raised to cause compression autoignition.

By adjusting the residual gas amount by this negative overlap valve timing control, it is generally controlled to adjust the pre-compression temperature of the fuel so that self-ignition is performed at an optimal timing by adiabatic compression. . (For example, refer to Patent Document 1).
JP-A-10-266878

  In such an operating state where self-ignition is not possible even by adjusting the residual gas amount by such negative overlap valve timing control, spark ignition operation is performed, and therefore the limit value of the operating state in which compression ignition operation is possible is set in advance. The compression ignition operation is performed only when the operation state is within the certain limit value.

  By the way, since the outflow of EGR gas from the combustion chamber is due to the differential pressure between the pressure in the combustion chamber and the atmospheric pressure (or exhaust pressure), the amount of EGR gas remaining in the combustion chamber is affected by the atmospheric pressure, Therefore, the self-ignition time is also under the influence of atmospheric pressure.

  Therefore, at the limit value of the operating state determined as described above, if the atmospheric pressure becomes low when traveling at a high altitude like an internal combustion engine mounted on a vehicle, there is a possibility that ignition does not occur at an appropriate timing or sometimes misfire occurs.

  Therefore, if the limit value of the operation state in which the compression ignition operation can be performed without misfiring even when the atmospheric pressure is low, the compression ignition operation region is set to a limit value that narrows, and the fuel consumption deteriorates. Become.

  The present invention has been made in view of the above points, and the object of the present invention is to improve the fuel consumption and the amount of NOx generated by expanding the compression ignition operation region by changing the compression ignition operation region according to the atmospheric pressure. It is in the point which provides the operation area | region control apparatus of the internal combustion engine which can aim at reduction of this.

  In order to achieve the above object, the invention described in claim 1 is an internal combustion engine capable of both a spark ignition operation and a compression ignition operation, and an atmospheric pressure detection means for detecting atmospheric pressure, and a compression ignition operation region determination. An operating state detecting means for detecting an operating state provided; a limit value deriving means for deriving a compression ignition operation limit value of the operating state corresponding to the atmospheric pressure detected by the atmospheric pressure detecting means; and the limit value deriving means. Is compared with the operation limit detected by the operation state detection means and the operation state determination means for determining whether or not it is within the compression ignition operation region, and the operation region determination means performs compression. An operation region control device for an internal combustion engine is provided that includes an operation region setting means for setting the internal combustion engine for compression ignition operation when it is determined that it is within the ignition operation region.

  The limit value deriving means derives the compression ignition operation limit value in the operation state corresponding to the atmospheric pressure, and compares the compression ignition operation limit value with the operation state to determine whether or not it is within the compression ignition operation region. Therefore, the compression ignition operation region varies depending on the atmospheric pressure, and the compression ignition operation region is not set to a compression ignition operation limit value that narrows the compression ignition operation region in consideration of the lowest atmospheric pressure. The fuel consumption can be improved and the amount of NOx generated can be reduced.

  According to a second aspect of the present invention, in the operation region control apparatus for an internal combustion engine according to the first aspect, the limit value deriving means stores a normally required torque limit value of the compression ignition operation corresponding to the engine speed of the fuel engine. A normal request torque limit value storage means; and a correction coefficient storage means for storing a normal request torque limit value correction coefficient corresponding to the atmospheric pressure, and the normal request torque limit value retrieved from the normal request torque limit value storage means A corrected required torque limit value corrected by the required torque limit value correction coefficient retrieved from the correction coefficient storage means is derived, and the operating state detecting means calculates the required torque based on the engine speed of the internal combustion engine and the depression amount of the accelerator pedal. And the operation region determination means compares the corrected required torque limit value derived by the limit value deriving means with the required torque detected by the operation state detection means. And judging whether the compression ignition operating region Te.

  The corrected required torque limit value obtained by correcting the normal required torque limit value of the compression ignition operation corresponding to the engine speed at the normal time when the atmospheric pressure is the average atmospheric pressure on the ground is corrected by the normal required torque limit value correction coefficient corresponding to the atmospheric pressure. The correction required torque limit value is compared with the required torque to determine whether or not it is within the compression ignition operation region. Therefore, the compression ignition operation region is expanded to improve fuel consumption and reduce the amount of NOx generated. Can be planned.

  According to a third aspect of the present invention, in the operation region control apparatus for an internal combustion engine according to the first aspect, the limit value deriving means stores an intake air temperature limit value memory for storing an intake air temperature limit value of the compression ignition operation corresponding to the atmospheric pressure. Whether the operating region determination unit is within the compression ignition operating region by comparing the intake air temperature limit value retrieved from the intake air temperature limit value storage unit by the limit value deriving unit with the intake air temperature. It is characterized by determining.

  Since the limit value that allows compression ignition operation can be searched according to atmospheric pressure without making the intake air temperature limit value of compression ignition operation constant, it is appropriate to ensure stable compression ignition while expanding the compression ignition operation area Therefore, the fuel consumption can be improved and the amount of NOx generated can be reduced.

Hereinafter, an embodiment according to the present invention will be described with reference to FIGS.
The internal combustion engine 1 according to the present embodiment includes an operation by a spark ignition (SI) combustion method (spark ignition operation) and an operation by a compression ignition (HCCI) method (compression ignition operation). This is a four-stroke cycle multi-cylinder internal combustion engine (may be a single cylinder) mounted on a vehicle that can be operated with different combustion methods.

  FIG. 1 is a schematic configuration diagram of the internal combustion engine 1, in which a piston 3 reciprocates in a cylinder 2, and a combustion chamber 4 is formed between a cylinder head that closes the cylinder 2 and the piston 3.

  An intake passage 5 and an exhaust passage 6 extend from the combustion chamber 4 through the ports. An intake valve 7 is provided at the opening of the intake port facing the combustion chamber 4, and an exhaust valve 8 is provided at the opening of the exhaust port facing the combustion chamber 4. The intake valve 7 that controls intake to the combustion chamber 4 and the exhaust valve 8 that controls exhaust from the combustion chamber 4 are both electromagnetic valves.

  In addition, an ignition plug 9 is attached to the combustion chamber 4 and a fuel injection valve 10 for injecting fuel directly into the combustion chamber 4 is attached.

The spark plug 9 is driven during the spark ignition operation and ignites the air-fuel mixture in the combustion chamber 4 by discharge.
The fuel injection valve 10 is connected to a fuel supply pump (not shown) and injects fuel into the combustion chamber 4 for a controlled time at a controlled timing.

  The intake passage 5 is provided with a throttle valve 11 for adjusting the intake flow rate. The throttle valve 11 is driven by an actuator (not shown), and the throttle valve opening is controlled according to the operating state.

  An exhaust purification device 12 is interposed in the exhaust passage 6, and a NOx adsorption catalyst (LNC) is used for the exhaust purification device 12.

Various sensors for detecting the operating state of the internal combustion engine 1 having the above-described structure are provided at various locations.
A rotation speed sensor 21 for detecting the rotation speed of the crankshaft (engine speed) Ne of the internal combustion engine 1 and a water temperature sensor 22 for detecting the temperature of the cooling water (engine water temperature) Tw of the internal combustion engine 1 are provided in the body of the internal combustion engine 1. It has been.

  The intake passage 5 is provided with a throttle sensor 23 for detecting the throttle valve opening degree Th in the throttle valve 11, and an intake pressure sensor 24 for detecting the intake negative pressure Pb in the intake passage 5 on the downstream side of the throttle valve 11 and An intake air temperature sensor 25 for detecting the intake air temperature Ta in the intake passage 5 is provided.

An exhaust temperature sensor 27 that detects the exhaust temperature Te is disposed in the exhaust passage 6 on the upstream side of the exhaust purification device 12.
In addition, an atmospheric pressure sensor 28 for detecting the atmospheric pressure Pa and an accelerator sensor 29 for detecting the depression amount Ap of the accelerator pedal are provided.

  Detection signals from various sensors such as the rotational speed sensor 21, the water temperature sensor 22, the throttle sensor 23, the intake pressure sensor 24, the intake air temperature sensor 25, the atmospheric pressure sensor 28, and the accelerator sensor 29 are input to the electronic control unit ECU 30. Then, it is processed by the computer to determine the operation region and to provide drive control for the intake valve 7, exhaust valve 8, spark plug 9, fuel injection valve 10, throttle valve 11 and the like in the determined operation region.

  A control procedure for determining the operation region of the spark ignition operation for discharging the spark plug 9 and the compression ignition operation for performing the compression ignition without discharging the spark plug 9 is shown in the flowchart of FIG. 2 and will be described below.

First, in step 1, it is determined whether or not it is at the start and immediately after the start. Until the warm-up is completed to some extent after the start, the process jumps to step 13 and proceeds to step 14 to perform a spark ignition operation for discharging the spark plug 9. The
When the warm-up is completed to some extent, the process proceeds to Step 2.

  In step 2, the intake air temperature Ta detected by the intake air temperature sensor 25, the engine rotational speed Ne detected by the rotational speed sensor 21, the atmospheric pressure Pa detected by the atmospheric pressure sensor 28, and the depression amount Ap of the accelerator pedal detected by the accelerator sensor 29 are calculated. Read.

  In the next step 3, the relationship between the atmospheric pressure Pa and the intake air temperature lower limit value TaL of the compression ignition operation is optimally determined in advance by experiment, the Pa-TaL table stored in the memory is searched, and the atmospheric pressure read in step 2 is read. An intake air temperature lower limit TaL corresponding to Pa is extracted.

An example of the Pa-TaL table is graphed and shown in FIG.
As shown in FIG. 3, as the atmospheric pressure becomes lower than the normal average atmospheric pressure of 760 mmHg on the ground, that is, the higher the altitude, the higher the intake air temperature lower limit TaL of the compression ignition operation is adopted.

In the next step 4, it is determined whether or not the intake air temperature Ta read in step 2 is not less than the intake air temperature lower limit value TaL and not more than the intake air temperature upper limit value TaH.
The intake air temperature upper limit TaH is a predetermined constant value regardless of the atmospheric pressure.

  If the intake air temperature Ta is within the range between the intake air temperature lower limit value TaL and the intake air temperature upper limit value TaH (TaL ≦ Ta ≦ TaH), the process proceeds to step 5; otherwise, the process jumps to steps 13 and 14; Let the spark ignition operation.

  Since the atmospheric pressure decreases and the intake air temperature lower limit TaL increases as the travel location becomes higher, the range between the intake air temperature lower limit TaL and the intake air temperature upper limit TaH is controlled to be narrow, and this range is narrowed from the beginning. It is not necessary to keep it, it is narrowed according to the atmospheric pressure.

When TaL ≦ Ta ≦ TaH and proceeding to step 5, the relationship between the atmospheric pressure Pa and the engine speed lower limit NeL for the compression ignition operation and the relationship between the atmospheric pressure Pa and the engine speed upper limit NeH for the compression ignition operation are tested in advance. The engine speed lower limit NeL and the engine speed upper limit NeH corresponding to the atmospheric pressure Pa read in step 2 are extracted by searching the Pa-NeL table and the Pa-NeH table stored in the memory. To do.

An example of a Pa-NeL table and a Pa-NeH table is graphed and shown in FIG.
As shown in FIG. 4, as the atmospheric pressure becomes lower than the normal average atmospheric pressure of 760 mmHg on the ground, the engine rotation speed lower limit value NeL of the compression ignition operation is gradually extracted, and the engine rotation speed upper limit value NeH. Will gradually extract small values.

  In the next step 6, it is determined whether or not the engine speed Ne read in step 2 is not less than the engine speed lower limit value NeL and not more than the engine speed upper limit value NeH, and the engine speed lower limit value NeL. If it is within the range between the engine speed upper limit value NeH (Ne ≦ Ne ≦ NeH), the routine proceeds to step 7, and if it is not within this range, the routine jumps to steps 13 and 14 to set the spark ignition operation.

  The higher the travel location, the lower the atmospheric pressure, and the range between the engine speed lower limit value NeL and the engine speed upper limit value NeH is controlled to be narrow, and it is not necessary to narrow this range from the beginning. , Narrowed according to atmospheric pressure.

  As described above, the intake ignition temperature lower limit value TaL, the engine speed lower limit value NeL, and the engine speed upper limit value NeH of the compression ignition operation are set to constant values, and limit values that enable the compression ignition operation according to the atmospheric pressure are extracted. Accordingly, the compression ignition operation region can be expanded and an appropriate region in which stable compression ignition can be ensured can be obtained.

When NeL ≦ Ne ≦ NeH and the routine proceeds to step 7, the required torque PM is calculated from the accelerator pedal depression amount Ap and the engine speed Ne read in step 2.
In the next step 8, the relationship between the engine speed Ne and the normal required torque lower limit value PML for the compression ignition operation and the relationship between the engine speed Ne and the normal required torque upper limit value PMH for the compression ignition operation are optimally determined in advance by experiments. And the normal required torque lower limit value PML and the normal required torque upper limit value PMH corresponding to the engine speed Ne read in step 2 are extracted.

  The normal required torque lower limit value PML and the normal required torque upper limit value PMH extracted here are those when the normal average atmospheric pressure on the ground is 760 mmHg, and an example of the Ne-PML table and the Ne-PMH table is graphed. As shown in FIG.

  As shown in FIG. 5, the normal required torque upper limit value PMH decreases with a large decrease rate as the engine speed Ne increases, and the normal required torque upper limit value PMH decreases with an extremely small decrease rate as the engine speed Ne increases. Become.

  In the next step 9, the relationship between the atmospheric pressure Pa and the required torque lower limit correction coefficient KPML and the relationship between the atmospheric pressure Pa and the required torque upper limit correction coefficient KPMH are optimally determined in advance by experiments, and the Pa-KPML table and Pa stored in the memory are stored. -Search the KPMH table and extract the required torque lower limit correction coefficient KPML and the required torque upper limit correction coefficient KPMH corresponding to the atmospheric pressure Pa read in step 2 above.

An example of the Pa-KPML table and the Pa-KPMH table is graphed and shown in FIG.
As shown in FIG. 6, the required torque lower limit correction coefficient KPML and the required torque upper limit correction coefficient KPMH are both “1” at the average atmospheric pressure of 760 mmHg, and the required torque lower limit correction coefficient KPML decreases as the average atmospheric pressure decreases to 760 mmHg. The required torque upper limit correction coefficient KPMH gradually shows a small value.

  When the normal required torque lower limit value PML is multiplied by the required torque lower limit correction coefficient KPML (> 1) and corrected to the corrected required torque lower limit value PML / KPML considering the atmospheric pressure, the corrected required torque lower limit value PML / KPML is A value larger than the normal required torque lower limit value PML (<1) shown in FIG.

  Further, when the normal required torque upper limit value PMH is multiplied by the required torque upper limit correction coefficient KPMH to be corrected to the corrected required torque upper limit value PMH / KPMH considering the atmospheric pressure, the corrected required torque upper limit values PMH / KPMH are shown in FIG. A value smaller than the normal required torque upper limit value PMH is shown.

  In the next step 10, the corrected required torque lower limit value PML / KPML and the corrected required torque obtained by correcting the normal required torque lower limit value PML and the normal required torque upper limit value PMH with the required torque lower limit correction coefficient KPML and the required torque upper limit correction coefficient KPMH, respectively. It is determined whether or not the required torque PM calculated in step 7 is within the range between the upper limit values PMH and KPMH. If it is within the range, the process proceeds to step 11; Fly to spark-ignition operation.

  When PML · KPML ≦ PM ≦ PMH · KPMH and the process proceeds to step 11, it is determined whether or not the timer described later is timed up (t = 0). If t = 0, the process proceeds to step 12 to perform the pressure ignition operation. Continue and jump from step 11 to step 14 until time is up.

In step 10, it is determined that the required torque PM is not in the range between the corrected required torque lower limit value PML · KPML and the corrected required torque upper limit value PMH · KPMH. When the process proceeds to step 13, the timer is set and started. 14 is spark ignition operation.
This timer is a down timer in which a predetermined time T is set as the timer time t and the timer time t decreases as time elapses when the timer T starts.

  During the spark ignition operation, the timer is sequentially set and PML · KPML ≦ PM ≦ PMH · KPMH is satisfied, and even if the process proceeds from step 10 to step 11, the process proceeds from step 11 to step 14 until the timer expires. The ignition operation is continued, and when the time is up, the routine proceeds from step 11 to step 12 to set the compression ignition operation.

  That is, when shifting from the spark ignition operation to the compression ignition operation, the compression ignition operation can be smoothly started without causing misfire or the like by shifting in a completely stable operation state after the elapse of the predetermined time T.

  The range between the corrected required torque lower limit value PML / KPML and the corrected required torque upper limit value PMH / KPMH corresponds to the compression ignition operation region, and if the required torque PM exists in this compression ignition operation region, the compression ignition operation is executed. Is done.

  As the atmospheric pressure decreases, the corrected required torque lower limit value PML / KPML increases and the corrected required torque upper limit value PMH / KPMH decreases, so the range between them, that is, the compression ignition operation region becomes narrower.

  In order to enable traveling at a high altitude with low atmospheric pressure, compression is performed by changing the compression ignition operation region according to the atmospheric pressure as in this embodiment, rather than fixing to a compression ignition operation region that is narrower than the original. The ignition operation region can be expanded, and fuel consumption can be improved and the amount of NOx generated can be reduced.

  As described above, the actual operation region determination control is not performed at the time of starting or immediately after starting (step 1), but the intake air temperature Ta is within the range between the intake air temperature lower limit value TaL and the intake air temperature upper limit value TaH (step 4). The engine speed Ne is within the range between the engine speed lower limit value NeL and the engine speed upper limit value NeH (step 6), and the required torque PM is the correction request torque lower limit value PML · KPML and the correction request torque upper limit value PMH. The compression ignition operation is executed only when it is within the range between KPMH (step 10), and the spark ignition operation is executed otherwise.

  The intake air temperature lower limit value TaL in step 4, the engine speed lower limit value NeL and the engine speed upper limit value NeH in step 6, and the correction request torque lower limit value PML / KPML and the correction request torque upper limit value PMH / KPMH in step 10 are all. Since a limit value capable of compression ignition operation is extracted and used according to the atmospheric pressure, the compression ignition operation region can be expanded, and fuel consumption can be improved and NOx generation amount can be reduced.

  The present invention is applicable to an internal combustion engine capable of both a spark ignition operation and a compression ignition operation.

1 is a schematic configuration diagram of an internal combustion engine according to an embodiment of the present invention. It is a flowchart which shows the procedure of driving | running | working area | region determination control. It is the figure which plotted the Pa-TaL table which is the relationship between atmospheric pressure Pa and the intake air temperature lower limit TaL of compression ignition operation. Graph showing Pa-NeL table and Pa-NeH table Pa-TaL table showing the relationship between atmospheric pressure Pa and engine rotation speed lower limit value NeL for compression ignition operation and the relationship between atmospheric pressure Pa and engine rotation speed upper limit value NeH for compression ignition operation FIG. Example of Ne-PML table and Ne-PMH table showing relationship between engine speed Ne and normal required torque lower limit value PML for compression ignition operation and relationship between engine speed Ne and normal request torque upper limit value PMH for compression ignition operation FIG. It is the figure which made the graph of the example of the Pa-KPML table and Pa-KPMH table which are the relationship between atmospheric pressure Pa and request torque lower limit correction coefficient KPML, and the relationship between atmospheric pressure Pa and request torque upper limit correction coefficient KPMH.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine, 2 ... Cylinder, 3 ... Piston, 4 ... Combustion chamber, 5 ... Intake passage, 6 ... Exhaust passage, 7 ... Intake valve, 8 ... Exhaust valve, 9 ... Spark plug, 10 ... Fuel injection valve, 11 ... Throttle valve, 12 ... Exhaust gas purification device,
21 ... Rotational speed sensor, 22 ... Water temperature sensor, 23 ... Throttle sensor, 24 ... Intake pressure sensor, 25 ... Intake temperature sensor, 27 ... Exhaust temperature sensor, 28 ... Atmospheric pressure sensor, 29 ... Accelerator sensor,
30 ... ECU.

Claims (3)

In an internal combustion engine capable of both spark ignition operation and compression ignition operation,
Atmospheric pressure detection means for detecting atmospheric pressure;
An operation state detection means for detecting an operation state provided for determination of the compression ignition operation region;
Limit value deriving means for deriving the compression ignition operation limit value of the operating state corresponding to the atmospheric pressure detected by the atmospheric pressure detecting means;
An operation region determination means for comparing the compression ignition operation limit value derived by the limit value deriving means with the operation state detected by the operation state detection means to determine whether or not it is within the compression ignition operation region;
An operation region setting means for setting the internal combustion engine to the compression ignition operation when the operation region determination means determines that the operation region determination means is within the compression ignition operation region;
An operating region control device for an internal combustion engine, comprising: The limit value deriving means includes
A normal required torque limit value storage means for storing a normal required torque limit value of the compression ignition operation corresponding to the engine speed of the internal combustion engine;
Correction coefficient storage means for storing a normal required torque limit value correction coefficient corresponding to the atmospheric pressure,
Deriving a corrected demand torque limit value obtained by correcting the normal demand torque limit value retrieved from the normal demand torque limit value storage means with the demand torque limit value correction coefficient retrieved from the correction coefficient storage means,
The operating state detection means detects the required torque based on the engine speed of the internal combustion engine and the amount of depression of the accelerator pedal,
The operation area determination means compares the correction required torque limit value derived by the limit value deriving means with the request torque detected by the operation state detection means to determine whether or not the engine is within the compression ignition operation area. The operating region control device for an internal combustion engine according to claim 1. The limit value deriving means includes
Intake temperature limit value storage means for storing the intake temperature limit value of the compression ignition operation corresponding to the atmospheric pressure,
The operation area determination means compares the intake air temperature limit value retrieved from the intake air temperature limit value storage means by the limit value deriving means with the intake air temperature to determine whether or not the vehicle is within the compression ignition operation area. The operating region control device for an internal combustion engine according to claim 1.

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