JP2010001825A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for an internal combustion engine capable of optimally controlling a combustion state during a start, in the control device for the internal combustion engine controlling an electronic throttle valve during the start of the internal combustion engine. <P>SOLUTION: This device is provided with an operation cycle set means setting operation cycle of the throttle control based on the combustion state of the internal combustion engine 10 in throttle control for starting the internal combustion engine 10 under a condition where opening of the electronic throttle valve 22 is reduced and increasing the opening after start. The operation cycle set means changes over operation cycle of the throttle control between setting as crank angle synchronization and setting as time synchronization based the combustion state. Preferably, engine speed NE is used as a correlation value of the combustion state, and operation cycle of the throttle control is set to time synchronization if the engine speed is lower than a prescribed lower limit value. The lower limit value is variably set based on friction acting on the internal combustion engine 10. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly, to a control device for an internal combustion engine that controls an electronic throttle valve when starting.

  Conventionally, as disclosed in, for example, Japanese Patent Application Laid-Open No. 2005-320923, an internal combustion engine control device that lengthens a cycle for calculating an input of a controlled object when a change in a target value or an output of the controlled object is small It has been known. More specifically, in this control device, when the change in the target valve timing or the change in the actual valve timing is small, the calculation cycle of the parameter adjustment mechanism and the calculation cycle of the controller are longer than the normal calculation cycle. Is set. Thereby, it is possible to reduce the calculation load of the ECU while ensuring the control accuracy of the variable valve timing device.

JP 2005-320923 A JP 2001-12292 A JP 2006-29194 A Japanese Patent No. 2886692

  For the control of the internal combustion engine, there is a control for performing calculation in a calculation cycle synchronized with the rotation angle of the crank angle (hereinafter referred to as “crank angle synchronization”) and a calculation cycle synchronized with time (hereinafter referred to as “time synchronization”). ) And a control for performing an operation. In general, in the control related to the combustion cycle of the internal combustion engine, calculation is performed in synchronization with the crank angle.

  Here, in the control of the electronic throttle valve at the start of the internal combustion engine, the calculation is generally performed in synchronization with the crank angle. More specifically, in this control, the opening degree of the electronic throttle valve is fully closed when the ignition switch is turned on. Then, by gradually opening the throttle valve after the start, the engine is shifted to a stable idle state while suppressing variations in the air-fuel ratio. When such control is performed in synchronization with the crank angle, the throttle can be opened and closed in synchronization with the intake stroke. For this reason, high-precision control of the engine speed and the air amount behavior can be performed.

  However, when the calculation is performed in synchronization with the crank angle, the calculation cycle changes depending on the engine speed. For this reason, when a situation occurs in which the engine speed becomes lower than the range assumed at the time of normal start-up, the control responsiveness is lowered, and there is a risk of causing an engine stall associated with the deterioration of the combustion state. Further, when a situation occurs in which the engine speed increases beyond the range assumed at the time of normal starting, there is a possibility that the load on the CPU increases, resulting in a control failure due to task omission or the like. As described above, if the control of the electronic throttle valve is always performed at a constant calculation cycle synchronized with the crank angle, it is assumed that it is difficult to maintain a good combustion state at the start.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a control device for an internal combustion engine that can optimally control the combustion state at the start of the internal combustion engine.

In order to achieve the above object, a first invention is a control device for an internal combustion engine,
Throttle control means for controlling the opening of a throttle valve provided in the intake passage of the internal combustion engine;
Based on the combustion state of the internal combustion engine, the calculation cycle of the throttle control means is set as a cycle synchronized with the rotation angle of the crankshaft of the internal combustion engine (hereinafter referred to as crank angle synchronization) or a cycle synchronized with time ( Hereinafter, calculation cycle setting means for switching whether to set as time synchronization),
It is characterized by providing.

According to a second invention, in the first invention,
The throttle control means controls the opening of the throttle valve immediately after the internal combustion engine is started.

According to a third invention, in the first or second invention,
The calculation cycle setting means includes means for acquiring the engine speed of the internal combustion engine, and sets the calculation period of the throttle control means to the time synchronization when the engine speed is smaller than a predetermined lower limit value. It is characterized by that.

According to a fourth invention, in the third invention,
The calculation cycle setting means sets the lower limit value to a larger value as the friction is larger, based on the friction acting on the internal combustion engine.

According to a fifth invention, in the third invention,
The calculation cycle setting means includes means for acquiring a water temperature of the internal combustion engine, and sets the lower limit value to a larger value as the water temperature is lower.

According to a sixth invention, in the third invention,
The calculation cycle setting means includes means for acquiring the driving status of the auxiliary machinery of the internal combustion engine, and when the auxiliary machinery is driven, the lower limit value is set as compared with the case where the auxiliary machinery is not driven. It is characterized by being set to a large value.

A seventh invention is the first or second invention, wherein
The calculation cycle setting means includes means for acquiring an in-cylinder pressure during combustion of the internal combustion engine, and sets the calculation cycle of the throttle control means to the time synchronization when the in-cylinder pressure is smaller than a predetermined lower limit value. It is characterized by doing.

According to an eighth invention, in any one of the first to seventh inventions,
The calculation cycle setting means includes means for acquiring the engine speed of the internal combustion engine, and sets the calculation period of the throttle control means to the time synchronization when the engine speed is larger than a predetermined upper limit value. It is characterized by that.

According to a ninth invention, in any one of the first to eighth inventions,
The calculation cycle setting means includes angular acceleration acquisition means for acquiring angular acceleration of the crankshaft, and sets the calculation cycle of the throttle control means to the time synchronization when the angular acceleration is smaller than a predetermined threshold. It is characterized by that.

  According to the first invention, in the throttle control for controlling the opening of the throttle valve of the internal combustion engine, the calculation cycle of the control is synchronized with the rotation angle of the crankshaft of the internal combustion engine (crank angle synchronization); It is switched between periods synchronized with time (time synchronization). In the control of the throttle valve, it is expected to improve the controllability of the air amount behavior and the engine speed behavior if the calculation is performed in synchronization with the crank angle synchronized with the intake stroke. On the other hand, since the calculation cycle of the calculation based on the crank angle synchronization changes depending on the engine speed, depending on the combustion state of the internal combustion engine, it is better to perform the calculation in time synchronization than in the crank angle synchronization. It may be preferred. According to the present invention, since the calculation cycle can be switched and set based on the combustion state of the internal combustion engine, a situation in which the combustion state deteriorates can be effectively suppressed.

  According to the second invention, in the throttle control immediately after the start of the internal combustion engine, whether to set the calculation period of the throttle control as crank angle synchronization or time synchronization based on the combustion state of the internal combustion engine is switched. Can do. Immediately after starting the internal combustion engine, the engine speed is not stable. For this reason, depending on the combustion state of the internal combustion engine, it may be preferable to perform the calculation in time synchronization rather than in the crank angle synchronization. According to the present invention, since the calculation cycle can be switched based on the combustion state of the internal combustion engine, a situation in which the combustion state deteriorates can be effectively suppressed.

  According to the third aspect, when the engine speed is smaller than the predetermined lower limit value, the calculation cycle of the control means is set to time synchronization. If the calculation is performed in synchronization with the crank angle in a region where the engine speed is extremely low, the control responsiveness may be reduced, and engine stall may occur due to deterioration of the combustion state. According to the present invention, it is possible to perform time-synchronized calculation in such a region, so that it is possible to effectively suppress a situation where the control responsiveness is lowered and the combustion state is deteriorated.

  According to the fourth invention, the lower limit value is variably set based on the magnitude of the friction of the internal combustion engine. In an operating state with a large amount of friction, there is a concern that engine stall may occur even if the engine speed is not in a very low speed region. According to the present invention, since the magnitude of the friction is reflected in the setting of the calculation cycle, the calculation area based on crank angle synchronization can be effectively expanded.

  According to the fifth aspect, the lower limit value is set to a larger value as the water temperature of the internal combustion engine is lower. When the water temperature is low, the internal combustion engine has a large friction. For this reason, according to the present invention, the lower limit value can be set larger as the friction of the internal combustion engine increases, so that the occurrence of engine stall due to the deterioration of the combustion state can be effectively suppressed.

  According to the sixth aspect, when the auxiliary machinery is driven, the lower limit value is set larger than when the auxiliary machinery is not driven. When the accessories are driven, the friction of the internal combustion engine increases. For this reason, according to the present invention, the lower limit value can be set larger as the friction of the internal combustion engine increases, so that the occurrence of engine stall due to the deterioration of the combustion state can be effectively suppressed.

  According to the seventh aspect, when the in-cylinder pressure during combustion is smaller than the predetermined lower limit value, the calculation cycle of the control means is set to time synchronization. When the in-cylinder pressure at the time of combustion is smaller than a predetermined lower limit value, it can be determined that the combustion state has deteriorated due to incomplete combustion such as misfire. For this reason, according to the present invention, it is possible to perform time-synchronized calculation in such a region, so that it is possible to effectively suppress a situation in which the control responsiveness decreases and the combustion state deteriorates.

  According to the eighth aspect, when the engine speed is larger than the predetermined upper limit value, the calculation cycle of the control means is set to time synchronization. If the calculation based on crank angle synchronization is performed in a region where the engine speed is higher than the normally assumed speed, there is a possibility that the load on the CPU increases and the task is lost. According to the present invention, time-synchronized computation can be performed in such a region, so that it is possible to effectively suppress the occurrence of control failure accompanying an increase in CPU load.

  According to the ninth aspect, when the angular acceleration of the crankshaft is smaller than the predetermined threshold, the calculation cycle by time synchronization is set. When the combustion state of the internal combustion engine deteriorates, the engine speed is drastically decreased, so that the angular acceleration is decreased. Therefore, according to the present invention, by comparing the angular acceleration with a predetermined threshold, it is possible to determine when the combustion state deteriorates regardless of the engine speed.

  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. The present invention is not limited to the following embodiments.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
FIG. 1 is a diagram for explaining a control device for an internal combustion engine according to an embodiment of the present invention and a structure around it. An intake passage 12 and an exhaust passage 14 communicate with the internal combustion engine 10. The intake passage 12 includes an air filter 16 at an upstream end. The air filter 16 is assembled with an intake air temperature sensor 18 for detecting the intake air temperature THA (ie, the outside air temperature). An exhaust purification catalyst 32 is disposed in the exhaust passage 14.

  An air flow meter 20 is disposed downstream of the air filter 16. An electronic throttle valve 22 is provided downstream of the air flow meter 20. A throttle motor 24 that is an actuator for driving the electronic throttle valve 22 is provided at one end of the shaft of the electronic throttle valve 22, and a throttle opening sensor 52 that detects the opening degree TA of the electronic throttle valve 22 is provided at the other end. Is provided. The electronic throttle valve 22 is driven to open and close by a throttle motor 24 based on an accelerator opening detected by an accelerator opening sensor and a throttle opening command value determined from each control signal of an electronic control device attached to the engine. It is what is done.

  A surge tank 28 is provided downstream of the electronic throttle valve 22. Further, a fuel injection valve 30 for injecting fuel into the intake port of the internal combustion engine 10 is disposed further downstream of the surge tank 28.

  The internal combustion engine 10 includes an intake valve 36 and an exhaust valve 38. An ignition plug is provided in the cylinder of the internal combustion engine 10 to ignite the fuel sprayed into the combustion chamber. Further, a piston 34 that reciprocates inside the cylinder is provided in the cylinder. Further, the internal combustion engine 10 is provided with a water temperature sensor 54 for detecting the cooling water temperature THW.

  Various auxiliary machines 42 are connected to the internal combustion engine 10. Examples of the auxiliary machinery 42 include a compressor for an air conditioner, an alternator, a torque converter, a pump for power steering, and the like. The piston 34 is connected to a crankshaft 40 that is rotationally driven by the reciprocating motion. The vehicle drive system and the above-described auxiliary machinery 42 are driven by the rotational torque of the crankshaft 40. A crank angle sensor 56 for detecting the rotation angle of the crankshaft 40 is attached in the vicinity of the crankshaft 40.

  As shown in FIG. 1, the control device of this embodiment includes an ECU (Electronic Control Unit) 50. In addition to the various sensors described above, the ECU 50 includes a KCS sensor that detects the occurrence of knocking, and various sensors for detecting vehicle speed, in-cylinder pressure, exhaust temperature, lubricating oil temperature, catalyst bed temperature, and the like (none of which are shown). ) Is connected. The ECU 50 is connected to various actuators such as the throttle motor 24, the fuel injection valve 30, and the auxiliary machinery 42 described above.

[Operation of Embodiment 1]
(About throttle control at start-up)
Next, with reference to FIG. 2, the opening degree control of the electronic throttle valve 22 (hereinafter simply referred to as “throttle control”) from the start of the internal combustion engine 10 to the transition to the steady idle state will be described. FIG. 2 is a diagram for explaining changes in the engine speed NE and the throttle opening degree TA in the throttle control. As shown in this figure, the internal combustion engine 10 is started with the electronic throttle valve 22 fully closed. More specifically, first, when the ignition switch is turned on at time t1, the throttle motor 24 is driven at the same time, and the electronic throttle valve 22 is closed. When the engine is started with the electronic throttle valve 22 closed, fuel atomization can be promoted and variations in the air-fuel ratio between the cylinders can be suppressed, so that the startability can be improved. In addition, since the intake pipe pressure can be reduced quickly, a steady state can be established at an early stage, and the controllability of the fuel injection amount and the air-fuel ratio can be improved.

  The electronic throttle valve 22 is opened at a predetermined timing (time t2 in FIG. 2) after starting. More specifically, the ECU 50 calculates the optimal valve opening timing and throttle opening based on various input values correlated with the combustion state of the internal combustion engine 10. Then, the throttle motor 24 is driven so that the calculated valve opening timing and throttle opening are obtained.

  Here, the calculation cycle of the throttle control is preferably a cycle synchronized with the intake stroke in the combustion cycle, that is, a calculation cycle synchronized with the rotation angle of the crankshaft 40 (crank angle synchronization). As a result, the engine speed behavior, the air amount behavior, and the like can be controlled with high accuracy, so that the combustion state at the start can be optimally controlled.

  However, when calculation is performed in synchronization with the crank angle, the calculation cycle changes depending on the engine speed NE. For this reason, when a situation occurs in which the engine speed NE becomes lower than the range assumed at the time of normal starting due to various factors, the control responsiveness is lowered, and the engine speed is deteriorated due to the deterioration of the combustion state. There is a risk of causing this. On the other hand, when the engine speed NE increases beyond the range assumed at the time of normal starting, the calculation load of the ECU 50 increases, which may cause a control failure such as missing a task. is there.

  Therefore, in the first embodiment, the calculation period of the throttle control is variably set according to the engine speed NE. More specifically, when the engine speed NE falls below a predetermined lower limit value L, the calculation period of throttle control is changed from a crank angle synchronization to a calculation period synchronized with time (time synchronization). For example, the lower limit L is set to a rotational speed (for example, 800 rpm) lower than a normally assumed idle rotational speed. When the throttle control is executed in time synchronization, the calculation can be performed at an arbitrary time period regardless of the engine speed NE, even in a region where the engine speed NE is extremely low. For this reason, the situation in which the combustion state of the internal combustion engine 10 deteriorates due to a decrease in the control response of the electronic throttle valve 22 can be effectively suppressed.

  Further, when the engine speed NE exceeds a predetermined upper limit value H, the calculation period of the throttle control is changed from crank angle synchronization to time synchronization. For example, the upper limit value H is set to a rotational speed (for example, 2000 rpm) that is higher than the normally assumed rotational speed at startup. When the throttle control is executed in time synchronization, even in a region where the engine speed NE is extremely high, the calculation can be performed at an arbitrary time period regardless of the engine speed NE. For this reason, it is possible to effectively suppress a situation where a task omission occurs due to an increase in the calculation load of the ECU 50 and the combustion state of the internal combustion engine 10 deteriorates.

  Thus, when the internal combustion engine 10 is started, the combustion state of the internal combustion engine 10 can always be optimally controlled by variably setting the calculation cycle in accordance with the engine speed NE.

[Specific Processing in Embodiment 1]
Next, with reference to FIG. 3, the specific content of the process performed in this Embodiment is demonstrated. FIG. 3 is a flowchart of a routine in which the ECU 50 sets a calculation cycle in throttle control.

  In the routine shown in FIG. 3, it is first determined whether throttle control is being executed (step 100). Specifically, it is determined whether or not the opening degree control of the electronic throttle valve 22 from the start of the internal combustion engine 10 to the transition to the steady idle state is being executed. As a result, when it is determined that the throttle control is not being executed, it is determined that it is not necessary to execute the control of this routine, and this routine is immediately terminated.

  On the other hand, if it is determined in step 100 that the throttle control is being executed, the process proceeds to the next step, and it is determined whether or not the engine speed NE is greater than a predetermined upper limit value H (step 102). ). Here, specifically, the engine speed NE detected by the crank angle sensor 56 is compared with the upper limit value H set in advance through experiments or the like. As a result, when it is recognized that the engine speed NE> the upper limit value H is established, if the throttle control is executed in synchronization with the crank angle, the calculation load of the ECU 50 due to the extremely high engine speed NE is outside the allowable range. Therefore, the process proceeds to the next step, and throttle control is executed with a calculation period synchronized with time (step 104).

  On the other hand, if the establishment of the engine speed NE> the upper limit value H is not recognized in step 102, it is determined that the calculation load of the ECU 50 due to crank angle synchronization is within the allowable range, and the process proceeds to the next step. It is determined whether the engine speed NE is smaller than a predetermined lower limit L (step 106). Here, specifically, the engine speed NE detected by the crank angle sensor 56 is compared with the lower limit value L set in advance through experiments or the like. As a result, when it is recognized that the engine speed NE <the upper limit value L is established, if the throttle control is executed in synchronization with the crank angle, the control responsiveness is reduced due to the extremely low engine speed NE. When it is determined that it is outside, the process proceeds to step 104, and throttle control is performed in time synchronization.

  On the other hand, if the establishment of the engine speed NE <lower limit value L is not recognized in step 106, it is determined that the decrease in control responsiveness due to crank angle synchronization is within the allowable range, and the process proceeds to the next step. Then, throttle control by crank angle synchronization is executed (step 108).

  As described above, according to the first embodiment, in the throttle control of the internal combustion engine 10, when the engine speed NE is smaller than the predetermined lower limit value L, the time-synchronized throttle control is performed. For this reason, it is possible to effectively suppress the situation where the control responsiveness of the throttle control is lowered and the combustion state is deteriorated.

  Further, according to the first embodiment, in the throttle control of the internal combustion engine 10, when the engine speed NE is larger than the predetermined upper limit value H, the throttle control by time synchronization is performed. For this reason, generation | occurrence | production of the control failure accompanying the increase in the calculation load of ECU50 can be suppressed effectively.

  By the way, according to the first embodiment described above, as throttle control, the internal combustion engine 10 is started with the electronic throttle valve 22 closed, and the opening degree of the electronic throttle valve 22 after the start is gradually opened. However, throttle control is not limited to this. In other words, the throttle valve opening control of the internal combustion engine 10 is not limited to the throttle control at the start.

  Further, according to the first embodiment described above, the calculation cycle in the throttle control is variably set between time synchronization and crank angle synchronization based on a comparison between the engine speed NE of the internal combustion engine 10 and a predetermined value. However, the value that can be used to determine the calculation cycle is not limited to the engine speed NE. That is, as long as the value has a correlation with the combustion state of the internal combustion engine 10, for example, in an internal combustion engine provided with an in-cylinder pressure sensor, the calculation cycle may be varied based on the in-cylinder pressure during combustion. More specifically, when the combustion pressure in the internal combustion engine 10 is low, it can be determined that incomplete combustion such as misfire has occurred. Therefore, for example, when the combustion pressure detected by the in-cylinder pressure sensor is smaller than a predetermined lower limit value, it may be determined that the combustion state has deteriorated and the calculation cycle may be set in time synchronization.

  In the first embodiment described above, the electronic throttle valve 22 corresponds to the “throttle valve” in the first invention, and the throttle control corresponds to the “throttle control means” in the first invention. Further, the “calculation cycle setting means” in the first aspect of the present invention is realized by the ECU 50 executing the processing of step 102 or 106 described above.

  Further, in the first embodiment described above, the “calculation cycle setting means” in the third aspect of the present invention is realized by the ECU 50 executing the processing of step 106.

  Further, in the first embodiment described above, the “calculation cycle setting means” according to the eighth aspect of the present invention is realized by the ECU 50 executing the process of step 102.

Embodiment 2. FIG.
[Features of Embodiment 2]
Next, a second embodiment of the present invention will be described with reference to FIGS. The system of the present embodiment can be realized by causing the ECU 50 to execute a routine shown in FIG. 5 described later using the hardware configuration shown in FIG.

  In the first embodiment described above, in the throttle control of the internal combustion engine 10, when the engine speed NE is smaller than the predetermined lower limit L, the throttle control is performed in time synchronization. Thereby, generation | occurrence | production of the engine stall by deterioration of a combustion state can be suppressed effectively.

  Here, as described above in the first embodiment, in the throttle control of the internal combustion engine 10, the controllability of the air amount behavior and the engine speed behavior is better when the calculation is performed in synchronization with the crank angle than in the calculation with time synchronization. Improvement can be expected.

  However, in the first embodiment described above, the lower limit L is set as a fixed value. The lower limit L is set based on a situation where the engine stall resistance is the lowest, that is, a situation where the engine friction is the largest. Therefore, in an engine situation where the friction is small, such as a restart after the internal combustion engine 10 is warmed up, it is assumed that the throttle control is performed in time synchronization regardless of the region where the engine is not stalled.

  Therefore, in the second embodiment, the control region based on time synchronization is expanded by variably setting the lower limit L. More specifically, the lower limit L is variably set based on the water temperature THW as the correlation value of the friction of each part of the engine.

  FIG. 4 is a diagram for explaining the dependency of the lower limit value L on the water temperature THW. The lower limit L is calculated based on the relationship shown in this figure. As shown in this figure, the lower limit L tends to decrease as the water temperature THW increases. This is because the friction of each part of the engine becomes smaller as the warm-up of the internal combustion engine 10 progresses. Therefore, by calculating the lower limit L based on the relationship shown in FIG. 4, it is possible to effectively expand the calculation area based on crank angle synchronization in a range where the internal combustion engine 10 does not stall.

[Specific Processing in Second Embodiment]
Next, with reference to FIG. 5, the specific content of the process performed in this Embodiment is demonstrated. FIG. 5 is a flowchart of a routine in which the ECU 50 sets a calculation cycle in throttle control.

  In the routine shown in FIG. 5, it is first determined whether throttle control is being executed (step 200). Here, specifically, the same processing as in step 100 is executed. As a result, when it is determined that the throttle control is not being executed, it is determined that it is not necessary to execute the control of this routine, and this routine is immediately terminated.

  On the other hand, if it is determined in step 200 that the throttle control is being executed, the process proceeds to the next step and the water temperature THW is taken in (step 202). Here, specifically, the detection signal of the water temperature sensor 54 is captured. Next, the lower limit value L is calculated (step 204). The ECU 50 stores the relationship between the water temperature THW and the lower limit value L shown in FIG. Here, specifically, the lower limit L corresponding to the water temperature THW taken in at step 202 is calculated based on this relationship.

  Next, it is determined whether the engine speed NE is smaller than a predetermined lower limit L (step 206). Here, specifically, the engine speed NE detected by the crank angle sensor 56 is compared with the lower limit value L calculated in step 204. As a result, when it is recognized that the engine speed NE <the upper limit value L is established, if the throttle control is executed in synchronization with the crank angle, the control responsiveness is reduced due to the extremely low engine speed NE. When it is determined that it is outside, throttle control is performed in synchronization with time (step 208). Here, specifically, the same processing as in step 104 is executed.

  On the other hand, if the establishment of the engine speed NE <lower limit value L is not recognized in step 206, it is determined that the reduction in control responsiveness due to crank angle synchronization is within the allowable range, and the process proceeds to the next step. Then, throttle control based on crank angle synchronization is executed (step 210). Here, specifically, the same processing as in step 108 is executed.

  As described above, according to the second embodiment, the lower limit L is calculated based on the water temperature THW in the throttle control when the internal combustion engine 10 is started. As a result, the lower limit value L reflecting the magnitude of the friction can be set, so that the calculation area based on the crank angle synchronization can be expanded to the maximum without causing the engine stall.

  By the way, according to the first embodiment described above, as throttle control, the internal combustion engine 10 is started with the electronic throttle valve 22 closed, and the opening degree of the electronic throttle valve 22 after the start is gradually opened. However, throttle control is not limited to this. In other words, the throttle valve opening control of the internal combustion engine 10 is not limited to the throttle control at the start.

  Further, according to the second embodiment described above, the lower limit L is variably set based on the water temperature THW, but the parameter used for the calculation of the lower limit L is not limited to the water temperature THW. That is, as long as it has a correlation with engine friction, for example, other detected values such as the outside air temperature THA may be used, and the driving status of the auxiliary machinery 42 may be considered.

  FIG. 6 is a diagram for explaining the dependency of the lower limit value L on the water temperature THW and the driving status of the auxiliary machinery 42. A chain line L1 shown in this figure indicates a case where the air conditioner as the auxiliary machinery 42 is turned off, and a solid line L2 indicates a case where the air conditioner is turned on. As a modification of the second embodiment, the lower limit value L can be calculated based on the relationship shown in FIG. That is, in this figure, the lower limit value L when the air conditioner is turned on is offset in a direction that becomes larger than the lower limit value L situation when the air conditioner is turned off. This is because the friction increased by turning on the air conditioner is taken into consideration. Therefore, as shown in FIG. 6, the lower limit L that reflects the engine friction in more detail can be calculated by taking into account the driving situation of the auxiliary machinery 42.

  The magnitude of engine friction also changes due to aging and the like. For this reason, for example, a steady change in friction due to a secular change or the like may be stored as a learning value, and further taken into account when calculating the lower limit L. Thereby, the calculation accuracy of the lower limit L considering the friction can be further increased.

  In the second embodiment, the electronic throttle valve 22 corresponds to the “throttle valve” in the first invention, and the throttle control corresponds to the “throttle control means” in the first invention. Further, the “calculation cycle setting means” in the first aspect of the present invention is realized by the ECU 50 executing the processing of step 206 described above.

  In the second embodiment described above, the “calculation cycle setting means” according to the fifth aspect of the present invention is realized by the ECU 50 executing the process of step 204.

Embodiment 3 FIG.
[Features of Embodiment 3]
Next, Embodiment 3 of the present invention will be described with reference to FIG. 7 and FIG. The system of the present embodiment can be realized by causing the ECU 50 to execute a routine shown in FIG. 8 to be described later using the hardware configuration shown in FIG.

  In the first embodiment described above, in the throttle control of the internal combustion engine 10, when the engine speed NE is smaller than the predetermined lower limit L, the throttle control is performed in time synchronization. Thereby, generation | occurrence | production of the engine stall by deterioration of a combustion state can be suppressed effectively.

  Here, when aged deterioration or sudden unstable combustion due to deposits or the like occurs in the internal combustion engine 10, it becomes difficult to determine the deterioration of the combustion state only by the engine speed NE described above. FIG. 7 is a diagram showing changes in the engine speed NE before and after the deterioration of the combustion state during normal times and aging deterioration. A chain line L3 in this figure indicates a change in the engine speed NE at the normal time. As indicated by the chain line L3, when the engine speed NE is lower than the lower limit L during normal times, the combustion state is deteriorated. In other words, the engine speed NE at which the combustion state deteriorates at normal times is set as the lower limit value L.

  On the other hand, the solid line L4 in this figure shows the change in the engine speed NE during aged deterioration. When the internal combustion engine 10 is deteriorated over time due to deposits or the like, the engine friction increases constantly. For this reason, as indicated by the solid line L4, before the engine speed NE decreases to the lower limit L, it is assumed that engine stall occurs due to deterioration of the combustion state. In addition, when sudden unstable combustion occurs, the combustion state may be deteriorated regardless of the magnitude of the engine speed NE. Therefore, in such a case, the deterioration of the combustion state cannot be accurately determined based on the engine speed NE.

  Therefore, in the third embodiment, in addition to the engine speed NE, the angular acceleration dω / dt of the crankshaft 40 is used as a parameter for determining deterioration of the combustion state. As shown in FIG. 7, when the combustion state deteriorates, the engine speed NE decreases rapidly. For this reason, the angular acceleration dω / dt greatly decreases before and after the combustion state deteriorates. Therefore, by determining whether or not the angular acceleration dω / dt has fallen below a predetermined threshold value, it is possible to accurately determine the occurrence of deterioration of the combustion state.

[Specific Processing in Embodiment 3]
Next, with reference to FIG. 8, the specific content of the process performed in this Embodiment is demonstrated. FIG. 8 is a flowchart of a routine in which the ECU 50 sets a calculation cycle in throttle control.

  In the routine shown in FIG. 8, first, it is determined whether throttle control is being executed (step 300). Here, specifically, the same processing as in step 100 is executed. As a result, when it is determined that the throttle control is not being executed, it is determined that it is not necessary to execute the control of this routine, and this routine is immediately terminated.

  On the other hand, if it is determined in step 300 that the throttle control is being executed, the process proceeds to the next step, and it is determined whether or not the engine speed NE is smaller than a predetermined lower limit value L2 (step 302). ). Here, specifically, the engine speed NE detected by the crank angle sensor 56 is compared with the lower limit L2. As the lower limit value L2, a value set in advance through experiments or the like is used as a value larger than the lower limit value L in step 106. As a result, if the engine speed NE <lower limit L2 is not established, it is determined that there is no possibility of engine stall due to deterioration of the combustion state even if the internal combustion engine 10 has deteriorated over time. Then, the throttle control is performed by synchronizing the crank angle (step 304). Here, specifically, the same processing as in step 108 is executed.

  On the other hand, if it is determined in step 302 that the engine speed NE <upper limit L2 is established, it is determined that there is a possibility of engine stall due to deterioration of the combustion state, and the routine proceeds to the next step. The acceleration dω / dt is calculated (step 306). Specifically, first, the angular velocity ω is calculated based on the detection signal of the crank angle sensor 56. Next, the angular acceleration dω / dt is calculated as a time change amount of the angular velocity ω.

  In the routine shown in FIG. 8, it is next determined whether or not the angular acceleration dω / dt is smaller than a predetermined threshold value W (step 308). Specifically, the angular acceleration dω / dt calculated in step 306 is compared with the threshold value W. As the threshold W, a value obtained in advance through experiments or the like is used as a threshold for determining deterioration of the combustion state. As a result, if the establishment of the angular acceleration dω / dt <threshold W is not recognized, it is determined that there is no possibility of engine stall due to the deterioration of the combustion state, and the routine proceeds to the above step 304 where the throttle by the crank angle synchronization Control is executed.

  On the other hand, if the angular acceleration dω / dt <threshold value W is found to be established in step 308, it is determined that there is an engine stall associated with the deterioration of the combustion state, and the process proceeds to the next step. +1 is counted in the counter (step 310).

  Next, it is determined whether or not the determination counter is greater than a predetermined threshold value J (step 312). Here, specifically, the determination counter accumulated in step 310 is compared with the threshold value J. The threshold value J is a threshold value set for preventing erroneous determination, and a value set in advance by experiment or the like is used. As a result, if the determination counter> threshold value J is not satisfied, the routine proceeds to step 304, where throttle control is performed with crank angle synchronization.

  On the other hand, if it is determined in step 312 that the determination counter> threshold value J is satisfied, it is determined that engine stall occurs due to the deterioration of the combustion state, and the process proceeds to the next step, where time-controlled throttle control is executed. (Step 314). Here, specifically, the same processing as in step 104 is executed.

  As described above, according to the third embodiment, the combustion state is determined based on not only the magnitude of the engine speed NE but also the magnitude of the angular acceleration dω / dt. For this reason, even when aged deterioration or the like occurs, the timing at which the combustion state deteriorates can be accurately determined. Therefore, the occurrence of engine stall can be effectively avoided by executing the throttle control by time synchronization at such timing.

  By the way, according to the first embodiment described above, as throttle control, the internal combustion engine 10 is started with the electronic throttle valve 22 closed, and the opening degree of the electronic throttle valve 22 after the start is gradually opened. However, throttle control is not limited to this. In other words, the throttle valve opening control of the internal combustion engine 10 is not limited to the throttle control at the start.

  In the third embodiment described above, the electronic throttle valve 22 corresponds to the “throttle valve” in the first invention, and the throttle control corresponds to the “throttle control means” in the first invention. Further, the “calculation cycle setting means” according to the first aspect of the present invention is realized by the ECU 50 executing the processing of step 304, 308, or 312 described above.

  In the above-described third embodiment, the ECU 50 executes the process of step 306, so that the “angular acceleration acquisition means” in the ninth invention executes the process of step 308. The “calculation cycle setting means” in the ninth aspect of the invention is realized.

It is a figure for demonstrating the structure of the control apparatus of the internal combustion engine which concerns on Embodiment 1 of this invention, and its periphery. FIG. 3 is a diagram for explaining throttle control of the internal combustion engine 10. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a figure for demonstrating the dependence with respect to the water temperature THW of the lower limit L. FIG. It is a flowchart of the routine performed in Embodiment 2 of this invention. It is a figure for demonstrating the dependence with respect to the drive of the auxiliary devices of the lower limit L. It is a figure which shows the change of the engine speed NE before and behind the deterioration of a combustion state at the time of normal time and aged deterioration. It is a flowchart of the routine performed in Embodiment 3 of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 22 Electronic throttle valve 24 Throttle motor 28 Surge tank 40 Crankshaft 42 Auxiliary machinery 50 ECU (Electronic Control Unit)
52 Throttle opening sensor 54 Water temperature sensor 56 Crank angle sensor ω Angular velocity dω / dt Angular acceleration

Claims (9)

Throttle control means for controlling the opening of a throttle valve provided in the intake passage of the internal combustion engine;
Based on the combustion state of the internal combustion engine, the calculation cycle of the throttle control means is set as a cycle synchronized with the rotation angle of the crankshaft of the internal combustion engine (hereinafter referred to as crank angle synchronization) or a cycle synchronized with time ( Hereinafter, calculation cycle setting means for switching whether to set as time synchronization),
A control device for an internal combustion engine, comprising:   2. The control apparatus for an internal combustion engine according to claim 1, wherein the throttle control means controls an opening degree of the throttle valve immediately after the internal combustion engine is started.   The calculation cycle setting means includes means for acquiring the engine speed of the internal combustion engine, and sets the calculation period of the throttle control means to the time synchronization when the engine speed is smaller than a predetermined lower limit value. 3. The control device for an internal combustion engine according to claim 1, wherein the control device is an internal combustion engine.   4. The control apparatus for an internal combustion engine according to claim 3, wherein the calculation cycle setting means sets the lower limit value to a larger value as the friction is larger, based on the friction acting on the internal combustion engine.   The control apparatus for an internal combustion engine according to claim 3, wherein the calculation cycle setting means includes means for acquiring a water temperature of the internal combustion engine, and sets the lower limit value to a larger value as the water temperature is lower.   The calculation cycle setting means includes means for acquiring the driving status of the auxiliary machinery of the internal combustion engine, and when the auxiliary machinery is driven, the lower limit value is set as compared with the case where the auxiliary machinery is not driven. 4. The control device for an internal combustion engine according to claim 3, wherein the control device is set to a large value.   The calculation cycle setting means includes means for acquiring an in-cylinder pressure during combustion of the internal combustion engine, and sets the calculation cycle of the throttle control means to the time synchronization when the in-cylinder pressure is smaller than a predetermined lower limit value. 3. The control device for an internal combustion engine according to claim 1, wherein the control device is an internal combustion engine.   The calculation cycle setting means includes means for acquiring the engine speed of the internal combustion engine, and sets the calculation period of the throttle control means to the time synchronization when the engine speed is larger than a predetermined upper limit value. 8. The control device for an internal combustion engine according to claim 1, wherein the control device is an internal combustion engine.   The calculation cycle setting means includes angular acceleration acquisition means for acquiring angular acceleration of the crankshaft, and sets the calculation cycle of the throttle control means to the time synchronization when the angular acceleration is smaller than a predetermined threshold. 9. The control device for an internal combustion engine according to claim 1, wherein the control device is an internal combustion engine.

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