JP2005061323A - Control device for compression ignition internal combustion engine - Google Patents

Abstract

[PROBLEMS] To perform not only introduction of internal EGR gas by changing valve timings of an intake valve and an exhaust valve, but also execute external EGR to recirculate exhaust gas to an intake system, and precisely control the amount of exhaust gas required for compression ignition. A control apparatus for a compression ignition internal combustion engine that improves ignition performance is provided. Variable valve timing mechanism for changing valve timing of intake valve and exhaust valve for opening / closing engine combustion chamber between two characteristics The internal EGR gas to be left in the combustion chamber is controlled to a predetermined amount, and the external EGR amount to be recirculated to the intake system is controlled (S10 to S18), so that it is supplied to the combustion chamber. The air-fuel mixture is combusted by compression ignition.
[Selection] Figure 3

Description

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

  As an ignition method for internal combustion engines, a compression ignition method in which fuel (light oil) is injected directly into air that has been heated to high temperature by high compression, such as diesel engines that use light oil as fuel, and gasoline is used as fuel. There are two spark ignition methods in the engine, and the current ignition method is almost determined by the fuel. In addition, recently, attempts have been made to self-ignite by supplying an air-fuel mixture obtained by sufficiently mixing various fuels such as gasoline and light oil with air at high temperature and pressure.

  In such an engine, the ignition starts in the entire combustion chamber and reacts at the same time. Therefore, the combustion starts with a low-temperature oxidation reaction, and the combustion temperature can be made relatively low so that the emission of nitrogen oxides is reduced. In addition to being able to reduce, the compression ratio can be increased from the spark ignition engine, and the fuel efficiency can be improved. This type of engine is called a compression ignition engine or a premixed compression ignition engine.

The problem with this compression engine (premixed compression ignition engine) is that the ignition delay increases as the load decreases, eventually leading to misfire. Conversely, pre-ignition occurs as the load increases. Knocking occurs. As a countermeasure, it is known that it is effective to increase the temperature of the air-fuel mixture in order to promote ignition, and while introducing high-temperature EGR gas to promote ignition, the amount of EGR gas is determined according to the load. It is known to control. (For example, refer to Patent Document 1).
JP 2000-64863 A

  This prior art is equipped with a variable valve mechanism that can change the opening timing of the exhaust valve and the intake valve to advance the closing timing of the exhaust valve and delay the opening timing of the intake valve at a low engine load. A large amount of internal EGR gas remains by making it horn, and a high-temperature mixture obtained by mixing uniformly with fresh air is compressed and ignited and burned. On the other hand, when the engine is under heavy load, The opening timing of the intake valves is set near the top dead center, and the air-fuel mixture is ignited by spark ignition.

  However, in the above-described prior art, the compression ignition combustion is realized only by changing the opening and closing timings of the intake valve and the exhaust valve, that is, the valve timings thereof, so the valve timing control must be complicated. I didn't get it. In addition, since compression ignition is achieved only by the internal EGR gas obtained through the control of the valve timing, the required amount of exhaust gas (EGR) cannot be precisely controlled, so that the ignition performance is not always satisfactory. .

  Therefore, the object of the present invention is to solve the above-mentioned problems, and not only the introduction of the internal EGR gas by changing the valve timing of the intake valve and the exhaust valve, but also the execution of the external EGR that recirculates the exhaust gas to the intake system. It is an object of the present invention to provide a control apparatus for a compression ignition internal combustion engine that precisely controls a necessary amount of exhaust gas and thereby improves ignition performance.

  In order to solve the above-mentioned object, according to claim 1, the valve timing (and lift amount) of at least one of the intake valve and the exhaust valve that opens and closes the combustion chamber of the internal combustion engine is set between at least two characteristics. The variable valve timing mechanism to be changed, the internal EGR means for controlling the operation of the variable valve timing mechanism to cause the exhaust gas to remain in the combustion chamber, and the EGR passage connecting the intake system and the exhaust system of the internal combustion engine are inserted. An EGR valve, external EGR control means for controlling the amount of exhaust gas to be recirculated to the intake system by adjusting the opening degree of the EGR valve, and the internal EGR so that the exhaust gas to be retained becomes a predetermined amount. The external E so as to control the amount of exhaust gas to be recirculated to the intake system according to at least the load of the internal combustion engine. Operating the R control unit, thus it was composed as and a compression ignition control means for the combustion by compression ignition the mixture supplied to the combustion chamber.

  In the control apparatus for the compression ignition internal combustion engine according to claim 2, the compression ignition combustion in which the internal combustion engine compresses and ignites the air-fuel mixture according to the operating state and the spark ignition combustion in which the combustion is performed by spark ignition. The predetermined amount is an exhaust gas amount necessary for a limit value of the load of the internal combustion engine capable of compression ignition combustion, and the compression ignition control means Is switched to the spark ignition combustion when the value exceeds the limit value.

  In the control apparatus for a compression ignition internal combustion engine according to claim 3, the compression ignition control means controls the amount of exhaust gas to be recirculated to the intake system according to the operation of the variable valve timing mechanism. The EGR control means is configured to operate.

  In the control apparatus for a compression ignition internal combustion engine according to claim 1, the operation of the variable valve timing mechanism for changing the valve timing (and the lift amount) of at least one of the intake valve and the exhaust valve between at least two characteristics. To control the operation of the internal EGR means so that the exhaust gas to be retained becomes a predetermined amount, and at least adjust the opening of the EGR valve according to the load of the internal combustion engine and return to the intake system Since the external EGR control means is operated so as to control the amount of exhaust gas and the mixture is compressed and ignited and combusted, the mixture temperature (in-cylinder gas temperature) necessary for compression ignition is determined by the internal EGR. While securing the amount of exhaust gas, it becomes possible to precisely control the amount of exhaust gas in the low load range by the external EGR control means, and therefore the ignition performance It is possible to improve. Moreover, the structure as a control apparatus of a compression ignition internal combustion engine can be simplified.

  In the control apparatus for the compression ignition internal combustion engine according to claim 2, the predetermined amount is an exhaust gas amount required at the limit value of the load of the internal combustion engine capable of compression ignition combustion, and the load of the internal combustion engine is the limit. Since it is configured to switch to spark ignition combustion when exceeding the value, the mixture gas temperature required for compression ignition is secured with the exhaust gas amount by the internal EGR as described above, and the exhaust gas amount in the low load region is set by the external EGR control means. It can be precisely controlled and the ignition performance can be improved.

  In the control apparatus for the compression ignition internal combustion engine according to claim 3, since the external EGR control means is operated so as to control the EGR amount in accordance with the operation of the variable valve timing mechanism, the external EGR control means The amount of exhaust gas in the low load range can be controlled more precisely, and therefore the ignition performance can be further improved.

  The best mode for carrying out a control apparatus for a compression ignition internal combustion engine according to the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a schematic diagram generally showing a control apparatus for a compression ignition internal combustion engine according to a first embodiment of the present invention.

  In FIG. 1, reference numeral 10 indicates a 4-cylinder 4-cycle in-line internal combustion engine (hereinafter referred to as “engine”) using gasoline as fuel. In the engine 10, the air drawn from an air cleaner (not shown) and passing through the intake pipe 12 is adjusted in flow rate by the throttle valve 14 and flows through the intake manifold 16. When the intake valve 18 is opened, the combustion chamber (see FIG. (Not shown).

  An injector 20 is disposed near the intake port in front of the intake valve 18. Gasoline fuel stored in a fuel tank (not shown) is pumped to the injector 20 through a fuel supply pipe (not shown) and connected to an ECU (electronic control unit) 24 through a drive circuit 22. When a drive signal indicating the valve opening time is supplied from the ECU 24 to the drive circuit 22, the injector 20 opens and injects gasoline fuel corresponding to the valve opening time into the intake port. The injected gasoline fuel mixes with the inflowing air to form an air-fuel mixture and flows into the combustion chamber.

  Reference numeral 26 denotes a spark plug. The spark plug 26 is connected to the ECU 24 via an ignition device 30 such as an igniter. When an ignition signal is supplied from the ECU 24 to the ignition device 30, a spark discharge is generated between the electrodes facing the combustion chamber to ignite the air-fuel mixture. And burn. As will be described later, the air-fuel mixture is also combusted by compression ignition. That is, the engine 10 is configured as a compression ignition engine (internal combustion engine) that switches between pre-combustion ignition combustion in which an air-fuel mixture is combusted by compression ignition and spark ignition combustion in which spark ignition is combusted in accordance with an operating state. The Therefore, in the engine 10, the compression ratio is set to a value between 14 and 16 that provides the best combustion efficiency.

  Gas (exhaust gas) generated by the combustion flows to the exhaust manifold 34 when the exhaust valve 32 is opened. The exhaust manifold 34 gathers downstream to form an exhaust system gathering portion, to which an exhaust pipe 36 is connected. The exhaust gas flows through the exhaust manifold 34, then flows through the exhaust pipe 36, and is further released to the atmosphere outside the engine.

  A crank angle sensor (shown as “ENG rotational speed” in the figure) 40 is disposed in the vicinity of the crankshaft or camshaft (both not shown) of the engine 10, and a cylinder discrimination signal and TDC (top dead center) of each cylinder. ) Or a TDC signal indicating a crank angle in the vicinity thereof, and a crank angle signal obtained by subdividing the TDC signal. Those outputs are input to the ECU 24.

  The ECU 24 includes a microcomputer and includes a CPU, ROM, RAM, A / D conversion circuit, input / output circuit, and counter. The ECU 24 counts the crank angle signal in the input signal and calculates (detects) the engine speed (ENG speed) NE.

  An accelerator pedal (not shown) is arranged on the floor of a driver's seat (not shown) of the vehicle on which the engine 10 is mounted, and an accelerator opening sensor ("Accelerator opening" in the figure) 42) is provided and outputs a signal corresponding to the accelerator opening ACC indicating the amount of depression of the driver's accelerator pedal. The output is also input to the ECU 24.

  The throttle valve 14 is mechanically disconnected from the accelerator pedal and connected to an actuator (such as a stepping motor) 44. The actuator 44 is connected to the ECU 24. The ECU 24 drives the actuator 44 from the accelerator opening ACC detected through the accelerator opening sensor 42 and controls the opening TH of the throttle valve 14. Thus, the operation of the throttle valve 14 is controlled by the DBW method.

  A rotation angle sensor 46 such as a rotary encoder is connected to the actuator 44, and a signal corresponding to the throttle opening TH is output through the rotation angle of the actuator 44 and sent to the ECU 24.

  An air flow meter 50 is disposed near the air cleaner of the engine 10 and outputs a signal corresponding to the intake air amount Q indicating the engine load. Further, a water temperature sensor (not shown) is arranged in a cooling water passage (not shown) of the engine 10 to output a signal corresponding to the engine cooling water temperature TW, and another temperature sensor is provided near the air flow meter 50. (Not shown) is arranged and outputs a signal corresponding to the temperature TA of the intake air. The outputs of these sensor groups are also input to the ECU 24.

  The intake valve 18 and the exhaust valve 32 described above are connected to a variable valve timing mechanism 54. Although the detailed illustration of the variable valve timing 54 is omitted, for example, the variable valve timing 54 has a structure disclosed in JP-A-2-275043, and three cams are juxtaposed on the camshaft and slid on the three cams. Three rocker arms are arranged in contact with each other.

  One intake valve 18 is connected to each of the rocker arms at both ends arranged on the intake valve side, and when the load on the engine 10 is relatively low and the engine speed is relatively low, the central rocker arm is idled, The intake valve 18 is driven with valve timing (and lift amount) characteristics determined by cams at both ends. The exhaust valve 32 is also configured to operate in the same manner.

  The characteristic is shown by a solid line in FIG. 2 (18 for the intake valve 18 and 32 for the exhaust valve 32 are displayed. When the air-fuel mixture is combusted by compression ignition as will be described later ("compression ignition combustion operation") The valve timing (and lift amount) is set to this characteristic, more specifically, as shown in the figure, the closing timing of the exhaust valve 32 is advanced and the opening timing of the intake valve 18 is delayed. In this way, a predetermined amount of exhaust gas remains in the cylinder to increase the temperature of the air-fuel mixture (in-cylinder gas temperature), thereby enabling the compression ignition operation. This corresponds to the amount of exhaust gas required at the limit value of the load capable of compression ignition combustion operation.

  The three rocker arms are configured to be connectable by pins. When the load on the engine 10 is relatively high and the engine speed is also relatively high, the pins are moved by hydraulic pressure to connect the three rocker arms, and the central cam The intake valve 18 is driven with the valve timing (and lift amount) characteristics determined in step (1). The same applies to the exhaust valve 32.

  On the other hand, as will be described later, when the air-fuel mixture is burned by spark ignition (referred to as “spark combustion operation”), the valve timing (and lift amount) is set to this characteristic. More specifically, as shown in the drawing, both the valve closing timing of the exhaust valve 32 and the valve opening timing of the intake valve 18 are changed to near the top dead center of the piston. As a result, the closing of the exhaust valve 32 is retarded and the amount of gas discharged in the combustion chamber is increased, while the opening of the intake valve 18 is advanced and the inflow of intake air is accelerated, so that the exhaust gas is combusted. It is sent to the exhaust system without remaining in the chamber.

  Returning to the description of FIG. 1, the variable valve timing mechanism 54 is connected to the ECU 24 via the hydraulic control circuit 56. The ECU 24 controls the operation of the variable valve timing mechanism 54 by exciting / de-energizing an electromagnetic solenoid (not shown) of the hydraulic control circuit 56 to control the movement of the above-described pin. The valve timing (and lift amount) is set (changed) to one of the above two characteristics.

  An EGR passage 60 is disposed between the intake pipe 12 and the exhaust pipe 36 of the engine 10 to connect the intake system and the exhaust system of the engine 10. An EGR valve 60a composed of an electromagnetic solenoid valve is inserted in the EGR passage 60. The EGR valve 60 a is connected to the ECU 24 via the drive circuit 62. The ECU 24 adjusts the opening degree of the EGR valve 60a via the drive circuit 62 and controls the amount of exhaust gas to be recirculated to the intake system.

  Next, the operation of the control apparatus for the compression ignition internal combustion engine according to the first embodiment will be described.

  FIG. 3 is a flowchart showing the operation. The illustrated program is started every predetermined time, for example, 10 msec.

  Explained below, in S10, the required load (required torque) PMECMD [N · m] of the engine 10 is calculated from the accelerator opening ACC and the engine speed NE. This is done by searching the map data whose characteristics are shown in FIG.

  Next, in S12, the output of the above-described sensor group excluding the crank angle sensor 40 is read, and engine operating parameters such as the intake air amount Q, the throttle opening TH, and the engine coolant temperature TW are detected.

  Next, in S14, it is determined whether or not the operation of the engine 10 is in the spark ignition operation region. This is performed by searching the map data showing the characteristics in FIG. 5 from the calculated required load PMECMD and the engine speed NE. As shown in the figure, the compression ignition operation region includes a region such as an idle region where the required load PMECMD and the engine speed NE are extremely small (very low load region), a region where the required load PMECMD and the engine speed NE are high (high load). Regions other than (region), in other words, the low load and medium load regions, and the other regions are the spark ignition operation region.

  When the result in S14 is negative, the program proceeds to S16, and the EGR amount (exhaust gas amount) required in the operating state is calculated from the similarly calculated required load PMECMD and engine speed NE. Note that the EGR amount includes both internal EGR and external EGR.

  Next, in S18, the spark ignition is turned off, that is, the ignition through the spark plug 26 is not performed, and the throttle opening TH is fully opened. Then, the operation of the variable valve timing mechanism 54 is controlled to switch to (set) the valve timing (V / T) characteristic for compression ignition operation shown in FIG. 2, and the opening of the EGR valve 60a is adjusted to adjust the external EGR. EGR control is performed so that the internal EGR amount obtained by switching the valve timing characteristics and the external EGR amount obtained by adjusting the opening degree of the EGR valve 60a become the values calculated in S16.

  This will be described with reference to FIG. 6 and FIG.

  FIG. 6 and FIG. 7 are explanatory diagrams showing the air-fuel ratio A / F with respect to the engine load, the EGR control method, and the EGR amount obtained thereby by comparing this embodiment with the prior art, and FIG. 6 shows this embodiment. FIG. 7 shows the control of the prior art described above.

  In the prior art shown in FIG. 7, the compression ignition operation is ensured corresponding to the engine load by changing the in-cylinder gas temperature by changing the EGR amount (internal EGR amount) via the valve timing. At the lowest load point a at that time, the air-fuel ratio (A / F) does not reach 14.7 (theoretical air-fuel ratio), and the ignition temperature has a sufficient margin. In other words, the present invention is in a state where the air-fuel ratio can be enriched and the in-cylinder gas temperature can be lowered, and the present invention has been made paying attention to that point.

  The control of this embodiment shown in FIG. 6 will be described. In this embodiment, the valve timing is fixed to that for the compression ignition operation on the lower load side than b which is the maximum load point of the compression ignition operation. The EGR valve 60a for introducing the external EGR is opened and the opening degree is gradually increased as the load becomes low, thereby increasing the total EGR amount including the inside and outside, and the mixture temperature (in-cylinder gas) Temperature) and control to reduce the intake air amount (enrich the air-fuel ratio).

  That is, by using the valve timing (and lift amount) V / T for compression ignition combustion operation, it corresponds to the amount of exhaust gas required at the limit value of the load (point b described above) that allows compression ignition combustion operation in the cylinder. The exhaust gas is left (predetermined amount described above) and the remaining EGR amount is obtained by external EGR. In that case, since an external EGR having a temperature lower than that of the prior art is introduced, the amount of EGR is increased in total to ensure the self-ignition temperature. As a result, the mixture gas temperature (in-cylinder gas temperature) was increased to enable the compression ignition operation.

  Returning to the explanation of S18 in FIG. 3, the fuel injection amount control is also executed at the same time. Specifically, the fuel injection amount is determined by searching map data set in advance according to the required load PMECMD and the engine speed NE, and most of the determined fuel injection amount is changed from the intake stroke to the compression stroke. It sprays over.

  On the other hand, when the result in S14 is affirmative, the routine proceeds to S20, where the throttle opening TH is controlled according to the required load PMECMD. Further, map data set in advance according to the required load PMECMD and the engine speed NE is searched to determine the ignition timing, and spark discharge is performed at the determined ignition timing to ignite the air-fuel mixture. Further, as described in S18, the fuel injection amount is determined and the fuel injection is executed, and at the same time, the control of the air-fuel ratio (A / F) is also executed.

  Further, since it is in the spark combustion operation region, the operation of the variable valve timing mechanism 54 is controlled so that the valve timing (and lift amount) V / T has a characteristic indicated by a broken line in FIG. Note that the threshold value for determining whether or not the spark ignition operation region is in S14 is specifically set to a value corresponding to the point b in FIG.

  In this embodiment, as described above, not only the introduction of the internal EGR gas by changing the valve timing of the intake valve 18 and the exhaust valve 32 but also the external EGR for returning the exhaust gas to the intake system is also executed. The control is simple and simple, and the amount of exhaust gas required for compression ignition can be precisely controlled, so that the ignition performance can be improved.

  Next, a control apparatus for a compression ignition internal combustion engine according to a second embodiment of the present invention will be described.

  FIG. 8 is a flow chart similar to FIG. 3, showing the overall control apparatus for the compression ignition internal combustion engine according to the second embodiment.

  The description will focus on the differences from the first embodiment. In the second embodiment, the variable valve timing mechanism 54 has a structure having a cam as described in JP-A-7-180520. In addition to realizing the characteristics indicated by the solid line in FIG. 2 in the low rotation range at low load, in addition to realizing the characteristics indicated by the broken line in FIG. When the load is lower than the load and in the low rotation range, the exhaust valve 32 is closed earlier (on the advance side) and the intake valve 18 is opened later (on the retard side) than the characteristic indicated by the solid line in FIG. In order to increase the amount of internal EGR.

  Explaining with reference to the flow chart of FIG. 8, when proceeding from S10 to S16 and proceeding to S18a, two types of characteristics are selected based on the engine load (specifically, the required load PMECMD) and the engine speed NE. I did (switch). In this case, the characteristic indicated by the solid line in FIG. 2 is the medium load, and the lower load side than that described above is the low load.

  FIG. 9 is an explanatory view similar to FIG. 6 showing the processing of the second embodiment. In this case, since the internal EGR amount is set in two stages, the characteristic of the control amount of the external EGR is also changed accordingly.

  Since the second embodiment is configured as described above, the amount of exhaust gas required for compression ignition can be controlled more precisely, and the ignition performance can be further improved. The remaining configuration of the second embodiment including the remaining processing of the flowchart of FIG. 8 is not different from that of the first embodiment.

  As described above, in the first and second embodiments of the present invention, the valve timing (and lift amount) of at least one of the intake valve 18 and the exhaust valve 32 that opens and closes the combustion chamber of the engine (internal combustion engine) 10. A variable valve timing mechanism 54 that changes between at least two characteristics, an internal EGR means (ECU 24, drive circuit 56) for controlling the operation of the variable valve timing mechanism to leave exhaust gas in the combustion chamber, and the internal combustion engine An EGR valve 60a inserted in an EGR passage 60 connecting the intake system (intake pipe 12) and the exhaust system (exhaust pipe 36) of the engine, and the opening degree of the EGR valve are adjusted to be returned to the intake system. External EGR control means (ECU 24, drive circuit 62) for controlling the amount of exhaust gas to be exhausted, and the internal E so that the exhaust gas to be retained becomes a predetermined amount. In addition to controlling the operation of the R means, at least the amount of exhaust gas to be recirculated to the intake system is controlled according to the load of the internal combustion engine (more specifically, the load (the engine required load PMECMD and the engine speed NE)). The external EGR control means is operated, and therefore, compression ignition control means (ECU 24, S18, S18a) for compressing and igniting the air-fuel mixture supplied to the combustion chamber is provided.

  The internal combustion engine is an internal combustion engine that is switchable between the compression ignition combustion for compressing and igniting an air-fuel mixture in accordance with the operating state and the spark ignition combustion for combusting by spark ignition, and the predetermined amount is The amount of exhaust gas required at the limit value of the load of the internal combustion engine capable of compression ignition combustion (point b in FIG. 6), and when the load of the internal combustion engine exceeds the limit value, It was configured to switch to the spark ignition combustion (ECU 24, S14).

  The compression ignition control means is configured to operate the external EGR control means so as to control the amount of exhaust gas to be recirculated to the intake system in accordance with the operation of the variable valve timing mechanism (ECU 24, S18a).

  In the above description, the valve timing characteristics of the intake valve 18 and the exhaust valve 32 shown in FIG. 2 are merely examples, and the present invention is not limited thereto.

  Further, although the embodiment of the present invention has been described by taking the intake port injection engine as an example, the present invention is applicable even to an in-cylinder injection engine.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view showing an overall control apparatus for a compression ignition internal combustion engine according to a first embodiment of the present invention. 2 is a graph showing two valve timing (and lift amount) characteristics that are switched (set) by the variable valve timing mechanism of the apparatus shown in FIG. 1. It is a flowchart explaining operation | movement of the apparatus shown in FIG. 2 is an explanatory graph showing the map data characteristics of the required load (required torque) PMECMD used in the processing of the flow chart of FIG. FIG. 3 is an explanatory graph showing map data characteristics of a spark ignition operation region used in the processing of the flowchart of FIG. 2. 3 is an explanatory diagram showing the control of the flow chart. It is explanatory drawing which shows control of a prior art in contrast with FIG. FIG. 4 is a flowchart similar to FIG. 3, generally showing a control apparatus for a compression ignition internal combustion engine according to a second embodiment of the present invention. 8 is an explanatory diagram showing the control of the flow chart.

Explanation of symbols

10 Compression ignition internal combustion engine (engine)
18 Intake valve 24 ECU (electronic control unit)
32 Exhaust valve 34 Exhaust manifold (exhaust system)
54 Variable valve timing mechanism 56 Hydraulic control circuit 60 EGR passage 60a EGR valve 62 Drive circuit

Claims (3)

  A variable valve timing mechanism for changing a valve timing of at least one of an intake valve and an exhaust valve for opening and closing a combustion chamber of an internal combustion engine between at least two characteristics, and controlling an operation of the variable valve timing mechanism to control the combustion chamber An internal EGR means for causing exhaust gas to remain, an EGR valve inserted in an EGR passage connecting an intake system and an exhaust system of the internal combustion engine, and an opening degree of the EGR valve is adjusted and returned to the intake system The external EGR control means for controlling the amount of exhaust gas to be controlled, and the operation of the internal EGR means so that the exhaust gas to be retained becomes a predetermined amount, and at least returned to the intake system according to the load of the internal combustion engine The external EGR control means is operated so as to control the amount of exhaust gas to be controlled, so that the air-fuel mixture supplied to the combustion chamber is compressed and attached. Control system for a compression ignition internal combustion engine, characterized in that it comprises a compression-ignition control means to burn with.   The internal combustion engine is an internal combustion engine that is switchable between the compression ignition combustion in which an air-fuel mixture is compressed and ignited in accordance with an operating state and the spark ignition combustion in which it is burned by spark ignition, and the predetermined amount is the compression ignition The amount of exhaust gas required at the limit value of the load of the internal combustion engine capable of combustion, and the compression ignition control means switches to the spark ignition combustion when the load of the internal combustion engine exceeds the limit value. The control apparatus for a compression ignition internal combustion engine according to claim 1. 3. The compression ignition control means operates the external EGR control means so as to control the amount of exhaust gas to be recirculated to the intake system in accordance with the operation of the variable valve timing mechanism. Control device for compression ignition internal combustion engine.

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