JP2012092718A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reliably control the occurrence of unusual combustion even when a low temperature short trip is repeated, with a control device of an internal combustion engine.SOLUTION: The control device of an internal combustion engine, includes: a low temperature short trip detection device for detecting a low temperature short trip where an internal combustion engine is stopped before completing a warm-up operation when performing a cold start under a low temperature environment; a count device for counting the number of low temperature short trips (Stp); and a drive region restriction device for performing a drive region restriction control that restricts a drive region of the internal combustion engine when a number Stp counted by the count device becomes a predetermined value or larger.

Description

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

  Japanese Patent Laid-Open No. 2006-258017 includes both an in-cylinder injector and an intake passage injector. When the internal combustion engine is warm, the internal combustion engine is started by injecting fuel only from the in-cylinder injector. In addition, a control device for an internal combustion engine is disclosed in which the internal combustion engine is started by injecting fuel only from the intake passage injector when the internal combustion engine is cold. According to this apparatus, the following effects can be obtained. When the internal combustion engine is warmly started, the fuel is easily vaporized, so that the unburned fuel hardly remains in the cylinder, but the temperature in the cylinder is high and pre-ignition and knocking are likely to occur. For this reason, by directly injecting fuel into the cylinder only from the in-cylinder injector, the temperature in the cylinder can be lowered, and the engine can be started while suppressing the occurrence of pre-ignition and knocking. When the internal combustion engine is cold-started, the temperature in the cylinder is low so that pre-ignition and knocking are difficult to occur, but the fuel is difficult to vaporize and unburned fuel is likely to be generated. For this reason, by injecting fuel into the intake passage only from the injector for the intake passage, vaporization of the fuel can be promoted and unburned fuel can be suppressed. Therefore, both suppression of preignition and knocking and suppression of unburned fuel can be achieved.

JP 2006-258017 A JP 54-7027 A JP 2005-273498 A

  However, the above conventional technique cannot be applied to an internal combustion engine having only an in-cylinder injector or an intake passage injector.

  As described above, when the internal combustion engine is cold started, the temperature in the cylinder is low and the fuel is less likely to vaporize. In particular, when the outside air temperature is low, the fuel becomes more difficult to vaporize. For this reason, when the internal combustion engine is cold-started when the outside air temperature is low and the internal combustion engine is stopped before the warm-up is completed (hereinafter referred to as “low-temperature short trip”), Since unburned fuel adheres to the internal combustion engine and the internal combustion engine is stopped before the adhering fuel disappears, deposits easily accumulate on the wall surface in the cylinder. In an internal combustion engine having only an in-cylinder injector, fuel must be injected from the in-cylinder injector even during a cold start, and deposits are likely to accumulate in the cylinder due to a low-temperature short trip. In addition, when the outside air temperature is low, even if the fuel is injected from the intake passage injector, the fuel is not easily vaporized. When tripping occurs, deposits accumulate in the cylinder.

  According to the knowledge of the present inventor, when low temperature short trips are repeatedly performed and the deposit in the cylinder increases, abnormal combustion may occur.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a control device for an internal combustion engine that can reliably suppress the occurrence of abnormal combustion even when a low-temperature short trip is repeated. And

In order to achieve the above object, a first invention is a control device for an internal combustion engine,
A low temperature short trip detection means for detecting a low temperature short trip in which the internal combustion engine is stopped after the cold start and before the warm-up is completed in a low temperature environment;
Counting means for counting the number of low temperature short trips;
An operation region restriction unit that performs operation region restriction control for restricting the operation region of the internal combustion engine when the number of times counted by the counting unit is equal to or greater than a predetermined value;
It is characterized by providing.

The second invention is the first invention, wherein
The counting means counts the number of low temperature short trips with a higher weight as the engine representative temperature at the start or stop of the low temperature short trip is lower.

The third invention is the first or second invention, wherein
In the operation region restriction control, the operation region restriction means expands a region for restricting the operation of the internal combustion engine as the number of low temperature short trips increases.

According to a fourth invention, in any one of the first to third inventions,
An in-cylinder temperature increasing means for performing in-cylinder temperature increase control for increasing the in-cylinder temperature when the operation region restriction control is executed is provided.

The fifth invention is the fourth invention, wherein
The in-cylinder temperature raising means performs control for advancing ignition timing as the in-cylinder temperature raising control.

The sixth invention is the fifth invention, wherein
The in-cylinder temperature increasing means increases the advance amount of the ignition timing as the number of times counted by the counting means increases.

  According to the first aspect of the invention, when the number of times counted by the counting means for counting the number of low-temperature short trips exceeds a predetermined value, it is possible to perform the operation region restriction control for restricting the operation region of the internal combustion engine. . For this reason, it is possible to reliably suppress the occurrence of abnormal combustion due to deposits accumulated in the cylinder due to the low temperature short trip.

  According to the second invention, the lower the engine representative temperature at the start or stop of the low temperature short trip, the lower the engine representative temperature, the higher the weight, and the number of the low temperature short trips is counted. This can correspond to the deposit amount in the cylinder. For this reason, it is possible to more accurately determine the necessity of the operation region restriction control, and it is possible to reduce the influence on drivability while reliably suppressing the occurrence of abnormal combustion.

  According to the third invention, when the number of low-temperature short trips is large, that is, when the deposit accumulation amount in the cylinder is large, the operation restriction region is expanded as compared with the case where the deposit accumulation amount in the cylinder is relatively small. Can do. For this reason, even when the deposit amount in the cylinder is large, the occurrence of abnormal combustion can be more reliably prevented. In addition, when the deposit amount in the cylinder is relatively small, the operation restriction area is not increased more than necessary, so that the influence on drivability can be reduced.

  According to the fourth aspect of the invention, by performing the in-cylinder temperature increase control for increasing the in-cylinder temperature when the operation region restriction control is performed, it is possible to increase the temperature of the deposit and promote the disappearance of the deposit.

  According to the fifth aspect of the present invention, the in-cylinder temperature can be easily increased without requiring a special mechanism by performing the control for advancing the ignition timing as the in-cylinder temperature increase control.

  According to the sixth invention, when the control for advancing the ignition timing is performed as the in-cylinder temperature rise control, the advance amount of the ignition timing can be increased as the number of low-temperature short trips increases. When the number of low-temperature short trips is large, the deposit accumulation amount is large. Therefore, by increasing the ignition timing advance amount, the combustion temperature can be increased and the deposit disappearance rate can be increased. On the other hand, when the number of low-temperature short trips is relatively small, the deposit accumulation amount is small, so the deposit disappearance rate may be somewhat low. For this reason, when the number of low-temperature short trips is relatively small, the deterioration of the vibration noise can be suppressed to a minimum by reducing the ignition timing advance amount and lowering the knock level.

It is a figure for demonstrating the system configuration | structure of Embodiment 1 of this invention. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a map for determining low temperature short trip in Embodiment 1 of this invention. It is a flowchart of the routine performed in Embodiment 1 of the present invention. 6 is a map showing a region where the operation of the internal combustion engine is restricted (prohibited) in the operation region restriction control according to the first embodiment of the present invention. It is a map for determining low temperature short trip in Embodiment 2 of this invention. It is a figure for demonstrating the effect of Embodiment 2 of this invention. It is a figure which shows the relationship between the frequency | count of the low temperature short trip in Embodiment 3 of this invention, and an operation | movement restriction | limiting area | region. 7 is a map showing a region where the operation of the internal combustion engine is restricted (prohibited) in the operation region restriction control of the third embodiment of the present invention. It is a flowchart of the routine performed in Embodiment 3 of the present invention. It is a figure for demonstrating the effect of Embodiment 4 of this invention. It is a figure for demonstrating the effect of Embodiment 5 of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted.

Embodiment 1 FIG.
FIG. 1 is a diagram for explaining a system configuration according to the first embodiment of the present invention. As shown in FIG. 1, the system of this embodiment includes a spark ignition type internal combustion engine 10. This internal combustion engine 10 is suitable as a power source for a vehicle. The number of cylinders and the cylinder arrangement of the internal combustion engine 10 are not particularly limited. In FIG. 1, only one cylinder is representatively depicted.

  Each cylinder of the internal combustion engine 10 is provided with a piston 12, an intake valve 14, an exhaust valve 16, a spark plug 18, and a fuel injector 20 that directly injects fuel into the cylinder (combustion chamber). . An intake passage 22 and an exhaust passage 24 are connected to each cylinder. The present invention is not limited to the configuration shown in the figure, and is an internal combustion engine that includes only an intake passage fuel injector that injects fuel into an intake passage (intake port), or an in-cylinder injection fuel injector and an intake passage fuel injector. The present invention can also be applied to an internal combustion engine having both of the above.

  The internal combustion engine 10 according to the present embodiment includes a supercharger 26, an intake valve device 44 that drives the intake valve 14, and an exhaust valve device 46 that drives the exhaust valve 16. The supercharger 26 has a compressor 26a and a turbine 26b. The turbine 26 b is disposed in the middle of the exhaust passage 24 and rotates by the energy of the exhaust gas flowing through the exhaust passage 24. The compressor 26 a is disposed in the middle of the intake passage 22, and is compressed by the air in the intake passage 22 by being driven by the turbine 26 b and rotating.

  An air cleaner 28 and an air flow meter 30 for detecting the amount of intake air are installed in the intake passage 22 upstream of the compressor 26a. An intercooler 32, a throttle valve 34, and a surge tank 36 are provided in the intake passage 22 downstream of the compressor 26a.

  A bypass passage 38 that bypasses the upstream side and the downstream side of the turbine 26b is provided in the vicinity of the turbine 26b. A waste gate valve 40 that opens and closes the bypass passage 38 is provided. When the waste gate valve 40 is opened, a part of the exhaust gas flows downstream through the bypass passage 38 without passing through the turbine 26b. The waste gate valve 40 of the present embodiment is configured by an electromagnetic valve, and opening / closing thereof is controlled by an ECU 50 described later. An exhaust purification catalyst 42 for purifying exhaust gas is installed in the exhaust passage 24 downstream of the turbine 26b.

  The system of this embodiment includes an ECU (Electronic Control Unit) 50 that controls the operation of each device of the internal combustion engine 10. In addition to the air flow meter 30, a sensor system including the following sensors is electrically connected to the ECU 50. The crank angle sensor 47 outputs a signal synchronized with the rotation of the crankshaft of the internal combustion engine 10. The ECU 50 can calculate the engine speed based on the crank angle detected based on the output of the crank angle sensor 47. Further, the ECU 50 can calculate the engine load based on the engine speed and the intake air amount detected by the air flow meter 30. The water temperature sensor 48 detects the cooling water temperature of the internal combustion engine 10. Knock sensor 49 detects a knock generated in internal combustion engine 10. In addition to the above, the sensor system includes various sensors used for controlling the internal combustion engine 10 or the vehicle. The ECU 50 is connected to various devices such as the ignition plug 18, the fuel injector 20, the throttle valve 34, and the waste gate valve 40 described above.

  In the present embodiment, the cooling water temperature detected by the water temperature sensor 48 is used as the representative temperature of the internal combustion engine 10, but in the present invention, the temperature of the other part of the internal combustion engine 10 (for example, the temperature of the cylinder head or the cylinder block). Etc.) may be provided, and the detected temperature may be used as the representative temperature.

  The ECU 50 detects the operating state of the internal combustion engine 10 using a sensor system, and controls the operation by driving each device based on the detection result. For example, the engine speed and the crank angle are detected based on the output of the crank angle sensor 47, and the intake air amount is detected by the air flow meter 30. Further, the fuel injection amount is calculated based on the intake air amount, the engine speed, and the like, and after determining the fuel injection timing, ignition timing, etc. based on the crank angle, the fuel injector 20 and the spark plug 18 are driven.

  As described above, when the internal combustion engine 10 is cold-started in a low-temperature environment (for example, below freezing point) and the warm-up is not completed, the internal-combustion engine 10 is stopped (hereinafter referred to as “low-temperature short trip”). Is easy to deposit deposits in the cylinder. When the low temperature short trip is repeatedly performed, the deposit accumulation in the cylinder proceeds rapidly. According to the knowledge of the present inventor, when the internal combustion engine 10 is operated and warmed up in a state where the low temperature short trip is repeatedly performed and the deposit accumulation amount in the cylinder is increased as described above, Abnormal combustion may occur. According to the inventor's research, such abnormal combustion is not runaway pre-ignition that occurs at high rotation and high load (so-called pre-ignition), but heat that is generated with very loud combustion noise at low rotation and high load. It was found that the surface ignition abnormal combustion (hereinafter simply referred to as “abnormal combustion”). This abnormal combustion is particularly likely to occur in an internal combustion engine with a supercharger. Unlike the pre-ignition at high rotation, this abnormal combustion does not run away and cause in-cylinder melting. However, since this abnormal combustion generates a very high in-cylinder pressure, if it is repeated, fatigue of each part may be caused and the internal combustion engine 10 may be damaged.

  In this embodiment, in order to prevent the above-described abnormal combustion, the low temperature short trip is detected and the number of times is counted to determine the deposit accumulation in the cylinder, and the deposit accumulation amount in the cylinder is the cause of the abnormal combustion. If it is determined that the target level has been reached, a control for preventing (inhibiting) the operation of the internal combustion engine 10 in the low rotation high load region (hereinafter referred to as “operation region restriction control”) is performed. As a result, the internal combustion engine 10 is not operated in a low-rotation and high-load region where there is a risk of abnormal combustion, so that abnormal combustion can be reliably prevented.

  2 and 4 are flowcharts of routines executed by the ECU 50 in the present embodiment in order to realize the above functions. According to the routine shown in FIG. 2, first, when it is detected that the ignition switch of the vehicle is turned on, that is, when the internal combustion engine 10 is started (step 100), the coolant temperature detected by the coolant temperature sensor 48 is detected. Is stored as the starting water temperature THWa (step 102). Thereafter, when it is detected that the ignition switch has been turned off, that is, that the internal combustion engine 10 has been stopped (step 104), the cooling water temperature detected by the water temperature sensor 48 is stored as the stop water temperature THWb (step 104). 106).

  When both the start time water temperature THWa and the stop time water temperature THWb are low, it can be determined that the operation of the internal combustion engine 10 was a low temperature short trip. FIG. 3 is a map for determining a low temperature short trip. In the map shown in FIG. 3, the horizontal axis represents the starting water temperature THWa and the vertical axis represents the stopping water temperature THWb, and a low temperature short trip determination region is set. When a low-temperature short trip is performed such that the point defined by the starting water temperature THWa and the stopping water temperature THWb is below the threshold line in this low-temperature short trip determination region, it is determined that deposits will accumulate in the cylinder. can do. In step 108, using the map shown in FIG. 3, the point defined by the starting water temperature THWa and the stopping water temperature THWb acquired in steps 102 and 106 is below the threshold line in the low temperature short trip determination region. It is determined whether it is a side. In this step 108, when the point defined by the starting water temperature THWa and the stopping water temperature THWb is below the threshold line in the low temperature short trip determination region, it is determined that the low temperature short trip is detected, and the low temperature short trip is determined. 1 is added to the number of times Stp (step 110).

  According to the process of the routine shown in FIG. 2 described above, a low temperature short trip can be detected and the number of times can be counted. By repeating the low temperature short trip, the deposit amount in the cylinder increases. For this reason, it can be determined by the low temperature short trip count Stp whether or not the deposit accumulation amount in the cylinder is equal to or higher than the level causing abnormal combustion. In the present embodiment, the determination value is S1. That is, when the number of low temperature short trips Stp is equal to or greater than S1, it is determined that the deposit accumulation amount in the cylinder is equal to or higher than a level causing abnormal combustion.

  According to the routine shown in FIG. 4, when it is detected that the ignition switch of the vehicle is turned on, that is, that the internal combustion engine 10 is started (step 200), the low temperature short trip count Stp is acquired (step 202). ), The success or failure of Stp ≧ S1 is determined (step 204). When Stp <S1, it can be determined that the deposit amount in the cylinder has not reached a level causing abnormal combustion. In this case, since it is not necessary to perform the operation region restriction control, the execution of this routine is terminated as it is.

  On the other hand, when Stp ≧ S1 is established in step 204, it can be determined that the deposit amount in the cylinder has reached a level that causes abnormal combustion, and therefore it is necessary to perform operation region restriction control. However, the abnormal combustion can occur after the internal combustion engine 10 has been warmed up to some extent, and it can be determined that the abnormal combustion does not occur before reaching the warm-up state. In the present embodiment, a determination value THWig for determining the warm-up state of the internal combustion engine 10 in which abnormal combustion may occur based on the coolant temperature is set in advance. If it is determined in step 204 that Stp ≧ S1, then the cooling water temperature THW detected by the water temperature sensor 48 is compared with this determination value THWig (step 206), and while THW <THWig, Execution of the operation area restriction control is delayed. If THW ≧ THWig, the operation region restriction control is executed (step 208). Thus, in this embodiment, since the operation region restriction control is not executed before the warm-up state of the internal combustion engine 10 reaches a stage where abnormal combustion can occur, unnecessary operation region restriction control is executed. It can be avoided.

  FIG. 5 is a map showing a region where the operation of the internal combustion engine 10 is restricted (prohibited) in the operation region restriction control. In the map shown in FIG. 5, a predetermined region on the low rotation and high load side, that is, a region in which abnormal combustion may be caused is set as the operation restriction region. In the operation region restriction control in step 208, control is performed so that the operation state of the internal combustion engine 10 does not enter the operation restriction region of the map shown in FIG. There are various methods for preventing the operation state of the internal combustion engine 10 from entering the operation restriction region. In this embodiment, a method of opening the waste gate valve 40 in a low rotation high load region is employed. By opening the waste gate valve 40, the supercharging pressure is reduced and the increase in the engine load is restricted, so that the operation state of the internal combustion engine 10 can be prevented from entering the operation restriction region. For this reason, generation | occurrence | production of abnormal combustion can be prevented reliably.

  After the warm-up of the internal combustion engine 10 is completed, the operation is continued, and when the temperature of the deposit accumulated in the cylinder rises and exceeds the deposit disappearance temperature, the deposit gradually disappears. ECU 50 stores in advance a cooling water temperature determination value THWdp that can be determined that the temperature of the deposit accumulated in the cylinder is equal to or higher than the deposit disappearance temperature. When the operation is continued for a predetermined time in a state where the cooling water temperature is equal to or higher than the determination value THWdp, it can be determined that the deposit accumulated in the cylinder disappears and there is no risk of abnormal combustion. For this reason, at this time, the operation region restriction control is canceled (terminated). Further, even when the operation region restriction control is not executed, if the operation of the internal combustion engine 10 is continued for a predetermined time while the cooling water temperature is equal to or higher than the determination value THWdp, it is determined that the accumulated deposit has disappeared. Therefore, the ECU 50 resets the low temperature short trip count Stp to zero.

In the present invention, the method of preventing the operation state of the internal combustion engine 10 from entering the operation restriction region is not limited to the method of opening the waste gate valve 40, and may be replaced by the following method, for example. You can also.
(1) A method for preventing the operation state of the internal combustion engine 10 from entering the operation restriction region by restricting the opening of the throttle valve 34.
(2) In a vehicle equipped with an automatic transmission (a planetary gear type stepped transmission, a continuously variable transmission, etc.), the operating state of the internal combustion engine 10 is prevented from entering the driving restriction region by changing the shift line. how to.

  In the first embodiment described above, the ECU 50 executes the processing of steps 100 to 108, whereby the “low temperature short trip detection means” in the first invention executes the processing of step 110. The “counting means” in the first invention is realized by executing the processing of the routine shown in FIG. 4 in the “counting means” in the first invention.

Embodiment 2. FIG.
Next, the second embodiment of the present invention will be described with reference to FIG. 6 and FIG. 7. The description will focus on the differences from the first embodiment described above, and the same matters will be described. Simplify or omit.

  FIG. 6 is a map for determining a low temperature short trip in the present embodiment. In the map shown in FIG. 6, a plurality of regions are set as the low temperature short trip determination region according to the starting water temperature THWa and the stopping water temperature THWb. That is, the region A on the lowest temperature side, the region B on the higher temperature side than the region A, and the region C on the higher temperature side than the region B are set for the starting water temperature THWa and the stopping water temperature THWb. .

  The amount of deposit that accumulates in the cylinder when a low temperature short trip is performed increases as the starting water temperature THWa decreases and increases as the stopping water temperature THWb decreases. Therefore, the deposit accumulation amount when the point defined by the start-time water temperature THWa and the stop-time water temperature THWb is in the region B is larger than the deposit accumulation amount in the region C. The deposit accumulation amount at this time is further larger than the deposit accumulation amount in the region B. In view of this, in the present embodiment, the following control is performed in order to more accurately determine whether or not the in-cylinder deposit accumulation amount is higher than a level that can cause abnormal combustion.

  In the present embodiment, when counting the number of low temperature short trips Stp in step 110 of FIG. 2, the lower the starting water temperature THWa or the stopping water temperature THWb, the greater the weight is added and the counting is performed. For example, when the point defined by the start-time water temperature THWa and the stop-time water temperature THWb is in the region A, it is 1, when it is in the region B, 0.5 when it is in the region C. Are added to the low temperature short trip count Stp. The number of times calculated with weights in this way is hereinafter referred to as “low temperature short trip number integrated value Stp”. In step 202 of the routine shown in FIG. 4, the low temperature short trip number integrated value Stp is read out, and in step 204, the necessity of the operation region restriction control is determined based on the low temperature short trip number integrated value Stp.

  The low temperature short trip count integrated value Stp serves as a more accurate index for depositing in-cylinder deposits compared to a value obtained by simply counting the number of low temperature short trips for the reason described above. For this reason, according to the present embodiment, it is possible to more accurately determine the necessity of the operation region restriction control based on the low temperature short trip count integrated value Stp. FIG. 7 is a diagram for explaining the effect of the present embodiment. The horizontal axis of FIG. 7 shows the simple number of low temperature short trips, and the vertical axis shows the low temperature short trip number integrated value Stp. In FIG. 7, a graph indicated by a thick line indicates an example of a change in the low-temperature short trip number integrated value Stp when the low-temperature short trip is repeated, and a thin line indicates the determination value Stp in the first embodiment. As shown in this figure, the determination value Stp in the first embodiment increases simply in proportion to the number of low-temperature short trips. On the other hand, the low temperature short trip count integrated value Stp in the present embodiment increases in accordance with the degree of deposit accumulation in each low temperature short trip, so that a low temperature short trip with relatively little deposit accumulation is performed. The amount of increase in the low-temperature short trip count integrated value Stp is small. Therefore, as compared with the first embodiment, it is possible to postpone the timing at which the low temperature short trip count integrated value Stp reaches the determination value S1 and the operation region restriction control is executed, thereby reducing the influence on drivability. Can do.

Embodiment 3 FIG.
Next, the third embodiment of the present invention will be described with reference to FIG. 8 to FIG. 10. The description will focus on the differences from the above-described embodiment, and the description of the same matters will be simplified. Or omit.

  In the present embodiment, the operation limit region in the operation region limit control is expanded as the number of low temperature short trips Stp increases. FIG. 8 is a diagram showing the relationship between the number of low temperature short trips Stp and the operation restriction region in the present embodiment. FIG. 9 is a map showing the operation restriction region in the present embodiment. In the map shown in FIG. 9, the operation restriction area is set in stages. That is, the operation restriction area A on the lowest rotation high load side, the operation restriction area B on the high rotation low load side compared to the operation restriction area A, and the high rotation low load side compared to the operation restriction area B. An operation restriction area C is set.

  Abnormal combustion is more likely to occur as the deposit amount in the cylinder increases. For this reason, when the deposit amount in the cylinder is large, abnormal combustion may occur in a relatively wide operation region on the low rotation high load side. On the contrary, when the deposit accumulation amount in the cylinder is not so large, the possibility of abnormal combustion is limited to a relatively narrow operating region on the low rotation high load side. In this embodiment, in view of this, the following control is performed. As shown in FIG. 8, when the number of low temperature short trips Stp is S1 or more, the operation in the operation restriction area A is prohibited. Further, when the number of low temperature short trips Stp is equal to or greater than S2 (> S1), the operation in the operation restriction area B is prohibited in addition to the operation restriction area A. Furthermore, when the number of low temperature short trips Stp is equal to or greater than S3 (> S2), operation in the operation restriction area C is prohibited in addition to the operation restriction areas A and B.

  FIG. 10 is a flowchart of a routine executed by the ECU 50 in the present embodiment in order to realize the above function. In the present embodiment, the ECU 50 executes the routine of FIG. 10 instead of the routine of FIG. 4 of the first embodiment. In FIG. 10, the same steps as those of the routine shown in FIG. 4 are denoted by the same reference numerals, and the description thereof is omitted or simplified. According to the routine shown in FIG. 10, the number of low temperature short trips Stp is acquired (step 202), and success or failure of Stp ≧ S1 is determined (step 210). As a result, when Stp ≧ S1 is satisfied, the operation restriction area A in FIG. 9 is set as the operation restriction area (step 212). In this case, subsequently, success / failure of Stp ≧ S2 is determined (step 214), and if Stp ≧ S2 is satisfied, the operation restriction region B in FIG. 9 is additionally set as the operation restriction region (step) 216). In this case, the success or failure of Stp ≧ S3 is further determined (step 218), and if Stp ≧ S3 is satisfied, the operation restriction region C in FIG. 9 is additionally set as the operation restriction region. (Step 220). After the operation restriction area is set in this way, the operation area restriction control is executed (step 208).

  According to the control of the present embodiment described above, when the number of low-temperature short trips Stp is large, that is, when the deposit accumulation amount in the cylinder is large, the operation restriction is more effective than when the deposit accumulation amount in the cylinder is relatively small. The area can be enlarged. For this reason, even when the deposit amount in the cylinder is large, the occurrence of abnormal combustion can be more reliably prevented. In addition, when the deposit amount in the cylinder is relatively small, the operation restriction area is not increased more than necessary, so that the influence on drivability can be reduced. In the present embodiment, the low temperature short trip count integrated value Stp described in the second embodiment may be used as the low temperature short trip count Stp.

  In the third embodiment described above, the “operating region limiting means” in the third aspect of the present invention is realized by the ECU 50 executing the routine shown in FIG.

Embodiment 4 FIG.
Next, a fourth embodiment of the present invention will be described with reference to FIG. 11. The description will focus on the differences from the above-described embodiments, and the description of the same matters will be simplified or omitted. To do.

  In the present embodiment, when the operation region restriction control described in the above-described embodiment is executed, the in-cylinder temperature increase control for increasing the in-cylinder temperature is executed in parallel with the operation region restriction control. As described above, the deposit accumulated in the cylinder gradually disappears when the temperature becomes higher than the deposit disappearance temperature. In the present embodiment, the temperature of the wall surface in the cylinder can be raised by the in-cylinder temperature rise control, and the temperature of the deposit accumulated on the wall surface can be raised. As a result, the temperature of the deposit can be maintained as high as possible or higher than the deposit disappearance temperature, and the deposit can be eliminated early.

  The method for increasing the in-cylinder temperature in the in-cylinder temperature increase control is not particularly limited, but in this embodiment, the in-cylinder temperature is increased by decreasing the cooling amount for the internal combustion engine 10. For example, the engine cooling water is circulated by an electric pump, and when the in-cylinder temperature rise control is performed, the amount of cooling is reduced by lowering the circulation flow rate by the electric pump than usual, thereby reducing the in-cylinder temperature from normal. Can be high. Alternatively, the amount of cooling by engine oil may be reduced. For example, an electric oil pump that circulates engine oil and an oil jet mechanism that cools the piston 12 when the oil pressure is equal to or higher than a predetermined oil pressure are provided, and when the in-cylinder temperature rise control is performed, the oil pressure is made less than the predetermined oil pressure to cool the piston 12. The in-cylinder temperature may be raised by stopping the oil jet and raising the temperature of the piston 12.

  FIG. 11 is a diagram for explaining the effect of the present embodiment, and is a diagram illustrating an example of how the engine output, the in-cylinder wall surface temperature, the deposit temperature, and the deposit accumulation amount change with time. Regarding the in-cylinder wall surface temperature, the deposit temperature, and the deposit accumulation amount, the case where the in-cylinder temperature increase control is executed is indicated by a thick line, and the case where the in-cylinder temperature increase control is not executed is indicated by a thin line as a comparative example. Hereinafter, the effect of this embodiment will be described with reference to FIG. As the engine output is higher, the amount of heat generated by the combustion of fuel in the cylinder also increases, so the temperature in the cylinder tends to increase. For this reason, the in-cylinder wall surface temperature increases and decreases as the engine output increases and decreases. If the in-cylinder temperature rise control is not executed, even if the deposit temperature once exceeds the deposit disappearance temperature, the deposit temperature may fall below the deposit disappearance temperature again as the engine output decreases. is there. On the other hand, when the in-cylinder temperature rise control is executed, the in-cylinder wall surface temperature can be shifted to the high temperature side as a whole. For this reason, even if the engine output fluctuates, the deposit temperature is easily maintained at the deposit disappearance temperature or higher. Therefore, the disappearance of the deposit can be promoted. The risk of occurrence of abnormal combustion is proportional to the amount of deposits. According to the present embodiment, the disappearance of the deposit can be promoted by the in-cylinder temperature rise control, so that the occurrence of abnormal combustion can be more reliably prevented. Further, by facilitating the disappearance of the deposit, it is possible to cancel (end) the operation region restriction control earlier, so that the influence on drivability can be reduced.

  Note that the in-cylinder temperature rise control is preferably executed in a region other than the operation region (high rotation high load region) where pre-ignition may occur. Thereby, it can prevent reliably that preignition is induced. Moreover, since the in-cylinder temperature is high in the operation region where pre-ignition may occur, the deposit temperature can be maintained at the deposit disappearance temperature or higher without executing the in-cylinder temperature increase control. For this reason, unnecessary execution of in-cylinder temperature increase control can be avoided by executing in-cylinder temperature increase control in a region other than the operation region in which pre-ignition may occur.

  In the above-described fourth embodiment, the “in-cylinder temperature increasing means” in the third aspect of the present invention is realized by the ECU 50 executing the above-described in-cylinder temperature increasing control in parallel with the execution of the operation region restriction control. ing.

Embodiment 5 FIG.
Next, a fifth embodiment of the present invention will be described with reference to FIG. 12. The description will focus on the differences from the above-described embodiments, and the description of the same matters will be simplified or omitted. To do.

  In the present embodiment, as a method for increasing the in-cylinder temperature in the above-described in-cylinder temperature increase control of the third embodiment, a method of advancing the ignition timing from the normal time is employed. That is, in this embodiment, ignition timing advance control is executed as in-cylinder temperature rise control. When the ignition timing is advanced, the combustion temperature rises, so that the in-cylinder temperature can be raised.

  The ECU 50 controls the ignition timing by executing knocking feedback control based on the output of the knock sensor 49. That is, the ECU 50 gradually retards the ignition timing when knock is detected, and gradually advances the ignition timing when knock does not occur. The ignition timing advance control can be realized by changing the threshold in the knocking feedback control. That is, at the time of execution of the ignition timing advance control, the threshold value of the knocking feedback control is changed so that knocking at a slightly higher level than that at the normal time occurs. As a result, the ignition timing is controlled to be advanced from the normal time, so that the combustion temperature rises and the deposit temperature also rises. For this reason, the loss | disappearance of a deposit can be accelerated | stimulated.

  FIG. 12 is a diagram for explaining the effect of the present embodiment, and is a diagram showing an example of how the engine load, ignition timing, combustion temperature, deposit temperature, and deposit accumulation amount change with time. Regarding the ignition timing, combustion temperature, deposit temperature, and deposit accumulation amount, the case where the ignition timing advance control is executed is indicated by a thick line, and the case where the ignition timing advance control is not executed is indicated by a thin line as a comparative example.

  As shown in FIG. 12, when the ignition timing advance control is executed, the combustion temperature can be shifted to the high temperature side as a whole, compared with the case where it is not executed. For this reason, even if the engine output fluctuates, the deposit temperature is easily maintained at the deposit disappearance temperature or higher. Therefore, the disappearance of the deposit can be promoted.

  Further, as shown in FIG. 12, it is desirable that the advance amount of the ignition timing is large on the low load side and small on the high load side. On the low load side, there is no danger of pre-ignition and there is a large margin until knocking occurs, so that the ignition timing can be advanced more than on the high load side. For this reason, by increasing the advance amount of the ignition timing on the low load side, it is possible to increase the combustion temperature and further promote the disappearance of the deposit.

  Further, the ignition timing advance amount may be decreased when the number of low temperature short trips Stp is relatively small, and the ignition timing advance amount may be increased when the number of low temperature short trips Stp is large. This is because when the number of low temperature short trips Stp is large, the deposit accumulation amount is large, and therefore it is preferable to increase the rate of deposit disappearance by increasing the ignition timing advance amount. On the other hand, when the number of low temperature short trips Stp is relatively small, the deposit accumulation amount is also small, so the deposit disappearance rate may be somewhat low. For this reason, when the number of low temperature short trips Stp is relatively small, the deterioration of vibration noise can be suppressed to a minimum by reducing the ignition timing advance amount and lowering the knock level.

  In the fifth embodiment described above, the “in-cylinder temperature increasing means” in the fifth and sixth inventions is achieved by the ECU 50 executing the ignition timing promotion control described above in parallel with the execution of the operation region restriction control. It has been realized.

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Piston 14 Intake valve 16 Exhaust valve 18 Spark plug 20 Fuel injector 22 Intake passage 24 Exhaust passage 26 Supercharger 34 Throttle valve 38 Bypass passage 40 Waste gate valve 42 Exhaust purification catalyst 50 ECU

Claims (6)

A low temperature short trip detection means for detecting a low temperature short trip in which the internal combustion engine is stopped after the cold start and before the warm-up is completed in a low temperature environment;
Counting means for counting the number of low temperature short trips;
An operation region restriction unit that performs operation region restriction control for restricting the operation region of the internal combustion engine when the number of times counted by the counting unit is equal to or greater than a predetermined value;
A control device for an internal combustion engine, comprising:   2. The control of an internal combustion engine according to claim 1, wherein the counting means counts the number of times of the low temperature short trip with a higher weight as the engine representative temperature at the start or stop of the low temperature short trip is lower. apparatus.   3. The internal combustion engine according to claim 1, wherein the operation region restriction unit expands a region for restricting operation of the internal combustion engine as the number of low temperature short trips increases in the operation region restriction control. Engine control device.   The internal combustion engine control according to any one of claims 1 to 3, further comprising in-cylinder temperature increasing means for performing in-cylinder temperature increasing control for increasing the in-cylinder temperature when the operation region restriction control is executed. apparatus.   5. The control apparatus for an internal combustion engine according to claim 4, wherein the in-cylinder temperature increasing means performs control for advancing ignition timing as the in-cylinder temperature increase control.   6. The control apparatus for an internal combustion engine according to claim 5, wherein the in-cylinder temperature increasing means increases the advance amount of the ignition timing as the number of times counted by the counting means increases.

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