JPH11336600A - Spark ignition type internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spark ignition type combustion engine capable of conducting stable self ignition operation by monitoring an NOx concentration in exhaust gas. SOLUTION: An operating condition judging section 2 judges, on the basis of signals from various sensors, which one of self ignition or spark ignition is suited for an operating condition, and informs an operating condition setting section 4 of a result of the judgement. A self ignition judging section 3 judges, on the basis of an NOx concentration before exhaust cleaning detected by an NOx sensor, whether a self ignition actually occurs, and informs the operating condition setting section 4 of a result of the judgement. The operating condition setting section 4 has a setting section for spark ignition 5, a setting section for self ignition 6 and a setting section for condition transition 7, and in the setting for condition transition, when the self ignition judging section 3 judges that a combustion condition to which the operating condition is transited would not occur, the original operating condition is restored.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spark ignition type internal combustion engine, and more particularly, to a spark ignition engine capable of performing a compression self-ignition operation if the operating conditions permit, thereby reducing nitrogen oxides in exhaust gas and improving fuel efficiency. The present invention relates to an internal combustion engine.

[0002]

2. Description of the Related Art In recent years, social awareness of the environment has increased, and market demands for effective use of buried fuel and suppression of CO2 emissions for preventing global warming have been increasing. It is necessary to further improve fuel efficiency.

[0003] The improvement of fuel efficiency in gasoline engines is
This is realized by increasing the operating ratio in the lean burn region where the air-fuel ratio is larger than the stoichiometric air-fuel ratio (A / F = 14.7). Nitrogen oxides such as NO and NO2 (hereinafter referred to as N
Ox).

An exhaust gas recirculation (hereinafter abbreviated as EGR) technique for returning a part of exhaust gas to a combustion chamber is known as a technique for achieving both reduction of NOx in exhaust gas and improvement of fuel efficiency. This EG
The principle of NOx reduction by R is to mix exhaust gas, which is an inert gas, with fresh air, thereby lowering the maximum combustion temperature and reducing nitrogen oxidation.

[0005] In a normal gasoline engine, a spark generated by a spark plug starts combustion.
In the engine that performs R, the radicals (radicals) rich in the chemical activity in the exhaust promote the decomposition and oxidation of gasoline,
In addition, there is an operation region in which self-ignition combustion occurs due to an increase in the compression end temperature because the amount of heat of the exhaust gas is added to fresh air.

As an internal combustion engine that performs self-ignition using such EGR, for example, a technique described in Japanese Patent Application Laid-Open No. HEI 6-193449 is known. According to this prior art,
It is determined that the operating condition of the engine is medium to low load,
The flow control valve of the exhaust gas recirculation path is opened, and a part of the exhaust gas is guided to the combustion chamber to adjust the self-ignition condition.

[0007]

However, according to the above prior art, the ignition timing, fuel injection amount, EGR, etc. are determined according to engine operating conditions such as engine speed and throttle opening.
After switching the operation state setting such as the amount, the start of the self-ignition operation is to be left to spontaneous generation. Therefore, if self-ignition does not occur due to variations in individual products, aging, changes in environmental conditions, etc., combustion will become unstable due to a large amount of EGR, and in the worst case, the operation of the engine itself will be stopped. There was a problem that something that could not be continued occurred.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to determine whether spark ignition is performed when switching between the spark ignition setting and the self-ignition setting of the operation state setting. An object of the present invention is to provide a spark ignition type internal combustion engine capable of monitoring whether self-ignition has occurred and realizing a stable operation state.

[0009]

Means for Solving the Problems (Correction Corresponding to Claims) In order to achieve the above object, the invention according to claim 1 determines whether or not a self-ignition condition is satisfied based on operating conditions. Operating condition judging means, a NOx sensor for detecting the concentration of nitrogen oxides in the exhaust gas immediately after being exhausted from the engine before the exhaust treatment, a judgment made by the operating condition judging means, and a nitrogen oxide detected by the NOx sensor. Operating state setting means for mutually switching the operating state of the engine between the operating state for spark ignition, the operating state for self-ignition, and the operating state for transition based on the substance concentration. An internal combustion engine.

According to a second aspect of the present invention, in the first aspect of the present invention, when the operating condition determining means determines that the self-ignition condition is satisfied in the spark ignition operating condition, The operating state is changed to the transition operating state, and at the same time, it is monitored whether a predetermined change occurs in the nitrogen oxide concentration detected by the NOx sensor, and when a predetermined change occurs in the nitrogen oxide concentration, Changes the operating state from the transitional operating state to the self-ignition operating state, and when a predetermined concentration change does not occur in the nitrogen oxide concentration, changes the operating state from the transitional operating state to the operating state. The gist is to return to the spark ignition operation state.

According to a third aspect of the present invention, in the first aspect of the present invention, when the operating condition determining means determines that the self-ignition condition is not satisfied in the self-ignition operating state, Changing the operation state to the transition operation state and monitoring whether a predetermined change occurs in the nitrogen oxide concentration detected by the NOx sensor; and when a predetermined change occurs in the nitrogen oxide concentration. The operating state is changed from the operating state for transition to the operating state for spark ignition, and when a predetermined concentration change does not occur in the nitrogen oxide concentration, the operating state is changed from the operating state for transition. The gist is to return to the self-ignition operation state.

According to a fourth aspect of the present invention, in the first aspect of the present invention, when the operating condition determining means determines that the self-ignition condition is not satisfied in the self-ignition operating state, Changing the operation state to the transition operation state and monitoring whether a predetermined change occurs in the nitrogen oxide concentration detected by the NOx sensor; and when a predetermined change occurs in the nitrogen oxide concentration. The operating state is changed from the operating state for transition to the operating state for spark ignition, and when a predetermined concentration change does not occur in the nitrogen oxide concentration, it is determined that the self-ignition release condition is insufficient. The gist of the present invention is to further change the operation state setting to the spark ignition inducing side.

According to a fifth aspect of the present invention, in the second aspect of the present invention, the predetermined concentration change of the nitrogen oxide concentration is a concentration change amount, a concentration change ratio, or a concentration change ratio. Is the time change rate of

According to a sixth aspect of the present invention, a criterion for determining the amount of change in the concentration of nitrogen oxide, the rate of change of the concentration, or the rate of change of the concentration over time is provided for each operating condition.

According to a seventh aspect of the present invention, in the invention according to any one of the first to sixth aspects, the criterion for the self-ignition condition in the operating condition determining means is based on the monitoring result of the nitrogen oxide concentration. The point is to update based on this.

According to an eighth aspect of the present invention, in the first aspect of the present invention, the operation state for the spark ignition, the operation state for the self-ignition, and the operation state for the state transition are changed. As operation state parameters controlled to different values according to the difference in each operation state, ignition timing,
The gist is that either the EGR amount or the fuel injection amount, or a combination of at least two of them.

[0017]

According to the present invention, a transient transition operating state is provided in addition to the spark operating state and the self-ignition operating state. Upon switching the mutual operation state between the spark ignition operation state and the self-ignition operation state based on the determination of the determination means,
Once the operation state is changed to the transition operation state, N
The nitrogen oxide concentration in the exhaust gas detected by the Ox sensor is monitored, and the self-ignition operation state can be set only in a region where the self-ignition operation can be actually performed, thereby preventing combustion from becoming unstable. This has the effect that a stable operating state can be maintained.

According to the second aspect of the present invention, in addition to the effect of the first aspect, the NOx sensor is provided in the transitional operation state when the operation mode is shifted from the spark ignition operation state to the self-ignition operation state. When a predetermined concentration change occurs in the nitrogen oxide concentration in the exhaust gas monitored by the above, it is determined that the self-ignition has succeeded, and the operation state is changed from the transition operation state to the self-ignition operation state, and the predetermined operation is performed. If no concentration change occurs, self-ignition failure is determined and the operation state for transition is returned to the operation state for spark ignition, so that if self-ignition does not actually occur due to changes in the external environment, etc. Since it is possible to return to the operating state, a more stable operating state can be continued.

According to the third aspect of the present invention, in addition to the effect of the first aspect, the NOx sensor is provided in the transition operation state when the operation state is shifted from the self-ignition operation state to the spark ignition operation state. When a predetermined concentration change occurs in the nitrogen oxide concentration in the exhaust gas monitored by the above, it is determined that the departure from the self-ignition has succeeded, and the operation state is changed from the transition operation state to the spark ignition operation state. When the predetermined concentration change does not occur, the self-ignition operation is determined to be unsuccessful, and the operation state is returned from the transition operation state to the self-ignition operation state so that the self-ignition operation is continued as long as the self-ignition operation actually continues. Therefore, the reduction of nitrogen oxides in the exhaust gas and the reduction of fuel consumption can be further performed.

According to the fourth aspect of the present invention, in addition to the effect of the first aspect, the NOx sensor is provided in the transition operation state when the operation mode is shifted from the self-ignition operation state to the spark ignition operation state. When a predetermined concentration change occurs in the nitrogen oxide concentration in the exhaust gas monitored by the above, it is determined that the departure from the self-ignition has succeeded, and the operation state is changed from the transition operation state to the spark ignition operation state. If the predetermined concentration change does not occur, the self-ignition release condition is determined to be insufficient, and the operating state setting is further changed to the spark ignition inducing side, whereby reliable self-ignition release can be realized.

According to the fifth aspect of the present invention, the predetermined concentration change of the nitrogen oxide concentration is defined as the concentration change amount, the concentration change ratio, or the time change ratio of the concentration, so that the self-ignition can be performed more precisely. Can be confirmed.

According to the sixth aspect of the present invention, the criterion for determining the amount of change in the concentration of nitrogen oxide, the rate of change in the concentration, or the rate of change in the concentration over time is provided for each of the operating conditions. Even if there is, an accurate self-ignition can be determined.

According to the present invention, the criterion of the operating condition determining means is updated based on the monitoring result of the nitrogen oxide concentration, so that variations in characteristics of individual internal combustion engines and aging of the engine can be achieved. It is possible to set the self-ignition operation area adapted to the change, the characteristic change of the fuel used, and other changes in the operating environment.

According to the present invention, a conventional spark is provided by setting any one of an ignition timing, an EGR amount, and a fuel injection amount or a combination of at least two of them as an operation state control parameter. The self-ignition operation can be easily performed by changing the control program of the ignition type internal combustion engine.

[0025]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a system configuration diagram showing a configuration of an embodiment in which a spark ignition type internal combustion engine according to the present invention is applied to a gasoline engine for a passenger car (hereinafter, abbreviated as engine). The components included in the normal engine other than the components necessary for the description of the present invention are omitted from the drawings for simplification of the description, or the reference numerals are omitted from the drawings. .

As shown in FIG. 1, the engine is provided with an engine control unit 1 having a microcomputer and the like, an air flow meter 8 for measuring an intake air amount, a throttle sensor 9 for measuring a throttle opening, and a cylinder. Fuel injection valve 10, a coolant temperature sensor 11 for measuring a coolant temperature, a knock sensor 12 for detecting knocking based on cylinder vibration caused by abnormal combustion, a spark plug 13 provided for each cylinder, an EGR valve 1 for opening and closing an EGR path.
4. An O2 sensor 15 for measuring the oxygen concentration in the exhaust gas, a NOx sensor 16 for measuring the NOx concentration in the exhaust gas before the exhaust gas purification processing, and a three-way exhaust gas purification device provided downstream of the O2 sensor 15 and the NOx sensor 16. A catalyst 17 and a distributor 18 are provided.

The NOx sensor 16 includes, for example, β-type Nb
A thin-film semiconductor NOx sensor formed into a thin film mainly containing 2O5 (niobium oxide) or a NOx sensor using an oxygen ion conductive solid electrolyte such as ZrO2 (zirconia) can be used.

An engine control unit 1 reads an output signal of various sensors such as an engine speed and a load, which will be described later, and determines an operating condition. An operating condition determining unit 2 determines self-ignition based on a measurement signal of a NOx sensor 16. A self-ignition determination unit 3 that performs the operation, and an operation state setting unit 4 that sets an operation state according to the operation conditions based on the determination results of the operation condition determination unit 2 and the self-ignition determination unit 3.

The operating condition determination unit 2 includes an air flow meter 8
Signal from the throttle sensor 9, a water temperature signal from the water temperature sensor 11, a knock sensor signal from the knock sensor 12, an O2 sensor 15
, An operating signal such as a rotation signal from the distributor 18 is input, and it is determined whether or not the operating condition of the engine satisfies the self-ignition condition based on these input signals. Then, the determination result is notified to the operation state setting unit 4.

The self-ignition judging section 3 judges whether the actual combustion state of the engine is spark ignition combustion or self-ignition combustion based on the NOx sensor signal from the NOx sensor 16, and determines the operation result by the operation state setting section. Notify 4.

The operation state setting unit 4 is a spark ignition setting unit 5, a self ignition setting unit 6, to which control is selectively transferred, based on the judgment results of the operation condition judgment unit 2 and the self ignition judgment unit 3. A transition setting unit 7 is provided. The output from each of these setting units 5, 6, 7 opens and closes the EGR valve 14, the amount of fuel injected from the fuel injection valve 10, and the ignition timing supplied to the distributor 18. Control each control signal.

FIG. 2 is a time chart for explaining the characteristics of the engine shown in FIG. 1 in each operating state setting.
Operating state setting, (b) self-ignition phenomenon, (c) NOx concentration, (d) ignition timing, (e) opening and closing of EGR valve,
(F) shows an example of a fuel injection amount and a change with time thereof.

First, it is assumed that the control according to the spark ignition setting is performed by the control of the spark ignition setting unit 5 of the operation state setting unit 4. In the spark ignition setting, the ignition timing is a standard ignition timing that sets the ignition advance as a general control method according to the rotational speed and the load, the EGR valve 14 is closed, the exhaust gas is not recirculated, and the fuel injection is performed. The volume is a standard injection volume.

Next, when the operating condition determining unit 2 determines that the operating condition is such that the self-ignition condition is satisfied, the operating condition setting unit 4 is notified of the determination, and the spark ignition setting unit 5 sets the state transition. The control is transferred to the unit 7 and a certain time ta
It is assumed that the operating state setting is changed to a state transition A setting (hereinafter abbreviated as transition A setting) for a state transition from the spark ignition setting to the self-ignition setting.

In the transition A setting, the ignition timing is advanced from the setting for spark ignition, the EGR valve is opened to perform exhaust gas recirculation, and the fuel injection amount is maintained at the standard injection amount. This transition A
In the state described above, although the control delay by the electromagnetic mechanical actuator and the passage delay time of the exhaust gas recirculation path are present, the engine advances the ignition timing while slightly increasing NOx while performing the spark ignition operation with the increase of the EGR amount. Causes knocking.

When knocking occurs, the self-ignition phenomenon occurs as shown in FIG. With the occurrence of the self-ignition phenomenon, as shown in FIG. 2 (c), the NOx concentration rapidly decreases. Generally, the amount of decrease in the NOx concentration is about several hundred ppm, or a value which is 90% or more lower than the NOx concentration during spark ignition combustion.

The self-ignition judging section 3 compares the signal obtained by A / D conversion of the measurement signal from the NOx sensor 16 with a NOx concentration change reference for self-ignition judgment stored in, for example, an internal ROM (not shown). A predetermined density reduction amount (for example, 30
0 ppm) or a predetermined concentration reduction rate (concentration reduction rate,
When the time change rate of a predetermined concentration (for example, 100 ppm / 0.1 sec) is achieved, it is determined that the self-ignition phenomenon has occurred, and the operation state setting unit 4 is notified of the self-ignition success. do.

The operating state setting unit 4 having received the notification of the success of the self-ignition shifts the control from the state transition setting unit 7 to the self-ignition setting unit 6, and outputs the operating state setting for the self-ignition (time tb). ). In the self-ignition setting, the ignition timing is returned to the standard, the EGR valve is kept open, and the fuel injection amount is reduced from the standard injection amount to, for example, 90% thereof.

In the transition A setting, a predetermined NOx
The concentration reduction takes a predetermined time (for example, t1 = 0.2 to 0.3).
If it does not occur within seconds), it is determined that the self-ignition has failed, and control is transferred from the state transition setting unit 7 to the spark ignition setting unit 5 to return to the spark ignition setting.

Next, in the self-ignition setting, when the operating condition determining unit 2 determines that the operating condition does not satisfy the self-igniting condition, the operating condition setting unit 4 is notified to that effect, The unit 4 transfers control from the self-ignition setting unit 6 to the state transition setting unit 7, and outputs a state transition B setting (hereinafter, abbreviated as transition B setting) (time tc).

In the transition B setting, the standard ignition timing is maintained, the EGR valve is closed to stop the EGR,
The fuel injection amount is returned to the standard injection amount. In the setting of the transition B, the self-ignition determination section 3 compares the signal obtained by A / D conversion of the measurement signal from the NOx sensor 16 with the NOx concentration change reference for self-ignition departure determination stored in, for example, an internal ROM (not shown). In comparison, when a predetermined concentration increase amount, a predetermined concentration increase ratio (concentration increase ratio), or a predetermined concentration time change rate is achieved, it is determined that the self-ignition departure is successful, and the operation state setting unit 4 To self-ignition release success.

The operating state setting unit 4 which has received the notification of the successful self-ignition release shifts the control from the state transition setting unit 7 to the spark ignition setting unit 5 and outputs the operating state setting for spark ignition (time td).

If a predetermined NOx is set in the transition A setting
If the concentration increase does not occur within a predetermined time (for example, t2 = 0.1 seconds), it is determined that the self-ignition has failed, and the state transition setting unit 7 sets the self-ignition setting to return to the self-ignition setting. The control is transferred to the unit 6.

In the transition A setting, if the predetermined NOx concentration rise does not occur within the predetermined time, the control parameter is further changed to the spark ignition inducing side in order to more positively depart from the self-ignition operation. May be. In this case, for example, the fuel injection amount may be increased so as to further increase the air-fuel ratio.

In the above, the cooperative operation of the operating condition determining unit 2, the self-ignition determining unit 3, and the operating state setting unit 4 has been described. However, it is also within the scope of the present invention to perform unified control without distinguishing these units. Is within.

The following flowcharts in FIGS. 3 and 4 explain the operation in the case where the inside of the engine control unit is integrated and controlled by software.

First, the engine control unit shown in the flowcharts of FIGS. 3 and 4 has four control modes including spark ignition, self-ignition, transition A, and transition B. Then, as a control cycle common to the four control modes, by repeatedly reading the operating conditions, determining various conditions, changing the mode when necessary according to the condition determination, and outputting the operation state setting according to each mode, the time is moment by moment. It shall correspond to changing operating conditions.

In FIG. 3, when the ignition key is turned on, spark ignition is set in the mode flag (step S10), and operation conditions are read (step S12). The reading of the operating conditions is an operation of reading the outputs of various sensors including, for example, the rotational speed and the engine load, and may read the output signals of the sensors as shown in FIG. 1 or intend to apply the present invention. There is no particular limitation as long as it can determine a condition for distinguishing between an operation region suitable for spark ignition of the engine and an operation region suitable for self-ignition.

Next, the output of the NOx sensor is read (step S14), and a change in the NOx concentration is detected and stored for later determination (step S16). Next, the low water temperature flag COL is determined (step S18), and COL is determined.
If D = 1, the engine is warming up, and the combustion chamber temperature is low and is not suitable for self-ignition operation. Therefore, the spark ignition setting is output (step S36), and then it is determined whether or not there is an error (step S62). If there is no error, ignition OF
It is determined whether it is F or not (step S64). If it is not OFF, the process returns to step S12 to repeat the next cycle.

The setting output for spark ignition in step S36 is
For example, the ignition timing is standardized, the EGR valve is closed, and the fuel injection amount is standardized.

In the determination of step S18, COLD
If = 1, the warm-up is over, and the mode is determined (step S20). If the mode is spark ignition, it is determined whether the operating condition read in step S12 satisfies the self-ignition condition (step S20). S22). If the self-ignition condition is not satisfied, the process proceeds to step S36.

If the self-ignition condition is satisfied in step S22, the mode is changed to transition A (step S24),
The timer for time monitoring is set to t1 to start time monitoring (step S26), the setting for transition A is output (step S28), and the process proceeds to step S62.

The setting output for transition A in step S28 is, for example, to advance the ignition timing from the standard, open the EGR valve,
The fuel injection amount is used as a standard.

If the mode is determined to be transition A in step S20, control is passed to step S30, and the NOx concentration is compared with a predetermined value stored in advance (step S3).
0). If the NOx concentration is equal to or less than the specified value in this comparison, it is determined that self-ignition has succeeded, the mode is changed to self-ignition (step S38), and the timer is stopped (step S4).
0), the self-ignition setting is output (step S42), and then the process proceeds to step S62. The setting output for self-ignition in step S42 is, for example, the ignition timing is returned to the standard,
The R valve is kept open and the fuel injection amount is set to, for example, 0.9 times the standard value.

If the NOx concentration exceeds the specified value in the comparison in step S30, the timer is referred to t1 from the start of monitoring with reference to the timer.
It is determined whether the time has elapsed (step S32), and t
If one has not elapsed, the process proceeds to step S28.

If it is determined in step S32 that t1 has already elapsed, since a predetermined change in NOx concentration has not occurred during the monitoring time, it is determined that self-ignition has failed, and the mode is changed to spark ignition (step S34). The process moves to step S36.

If the mode is self-ignition in step S20, it is determined whether the operating conditions read in step S12 satisfy the self-ignition departure condition (step S44). If the self-ignition release condition is not satisfied, the process proceeds to step S42.

If the self-ignition departure condition is satisfied in step S44, the mode is changed to transition B (step S4).
6) The timer for time monitoring is set to t2 to start time monitoring (step S48), the setting for transition B is output (step S50), and then the process proceeds to step S62.

The setting output for transition A in step S50 holds, for example, the standard ignition timing, closes the EGR valve,
This is to return the fuel injection amount to the standard.

If the mode is determined to be transition B in step S20, control is passed to step S52, and the NOx concentration is compared with a predetermined value stored in advance (step S5).
2). If the NOx concentration exceeds the specified value in this comparison,
It is determined that the self-ignition release has succeeded, the mode is changed to spark ignition (step S58), the timer is stopped (step S60), and the process proceeds to step S36.

If the NOx concentration is equal to or less than the specified value in the comparison in step S52, it is determined whether or not t2 has elapsed from the start of monitoring with reference to the timer (step S54), and t2 is still determined.
If not, the process proceeds to step S50.

If it is determined in step S54 that t2 has already elapsed, the predetermined NOx concentration change has not occurred during the monitoring time. Therefore, the fuel injection amount is further increased to change the control parameter to the spark ignition inducing side. (Step S5
6), proceed to step S52.

As described above, when the operation state setting of the engine is switched between the setting for spark ignition and the setting for self-ignition, the mode is temporarily shifted to the setting for state transition, and during the setting for state transition, NO before exhaust gas purification detected by NOx sensor
The Ox concentration is monitored, and if a predetermined concentration change occurs, the state transition setting is shifted to the target setting. If the predetermined concentration change does not occur, the state transition setting returns to the original setting. It is possible to avoid a situation in which the operation state setting is switched to an unstable operation state, and to maintain a stable operation state.

FIG. 5 is a graph showing an example in which a reference value of the amount of change in NOx concentration for determining whether or not self-ignition has succeeded is provided for each operating state. In the figure, the horizontal axis is the engine speed, and the vertical axis is the load. The low-rotation and low-load region 21 has a NOx concentration reduction amount of 300 ppm,
The region 22 of the middle rotation / medium load has the NOx concentration reduction amount 400
ppm. Since the high torque or power of the engine is required in the high-speed or high-load region 23, the region 23 is excluded from the self-ignition target.

Similarly, the rate of decrease in NOx concentration for determining self-ignition is not a uniform value, but may be, for example, 90%, 85%,
The rate of decrease in the NOx concentration for determination may be changed for each operating state, such as 80%, and used for the determination of self-ignition.

If a graph as shown in FIG. 5 is stored as a map or respective boundary values in a rewritable nonvolatile memory, and this memory can be rewritten according to the operation state when the self-ignition operation has actually succeeded. According to changes in engine characteristics and changes in external conditions, it is possible to implement learning that dynamically changes the operation area in which self-ignition operation is determined to be appropriate. It is more effective for stabilizing characteristics, improving fuel efficiency, purifying exhaust gas, and the like.

Although the external EGR control method has been described as an embodiment of the exhaust gas recirculation, it is needless to say that the present invention is not limited to this. By controlling each valve timing of the intake valve / exhaust valve to which the variable valve apparatus is applied, the EGR is controlled. The same effect can be obtained by applying a so-called internal EGR control method for controlling the amount.

[Brief description of the drawings]

FIG. 1 is a diagram showing a system configuration of an embodiment of a spark ignition type internal combustion engine according to the present invention.

FIG. 2 is a time chart illustrating the operation of the spark ignition type internal combustion engine according to the present invention.

FIG. 3 is a flowchart illustrating an operation of the spark ignition type internal combustion engine according to the present invention.

FIG. 4 is a flowchart illustrating the operation of the spark ignition type internal combustion engine according to the present invention.

FIG. 5 is a graph showing an example in which a criterion for determining whether a spark ignition state or a self-ignition state is provided for each engine operating condition.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 engine control unit 2 operating condition determining unit 3 self-ignition determining unit 4 operating state setting unit 5 spark ignition setting unit 6 self-ignition setting unit 7 state transition setting unit 10 fuel injection valve 14 EGR valve 16 NOx sensor 18 distributor

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Tomonori Urushihara Nissan Motor Co., Ltd. 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa

Claims (8)

[Claims] An operating condition determining means for determining whether or not a self-ignition condition is satisfied based on an operating condition, and detecting a concentration of nitrogen oxides in exhaust immediately after exhaust from an engine before exhaust processing. The engine operation between the spark ignition operation state, the self-ignition operation state, and the transition operation state based on the determination by the operating condition determination means and the nitrogen oxide concentration detected by the NOx sensor. Operating state setting means for switching between states; and a spark ignition type internal combustion engine. 2. When the operating condition determining means determines that the self-ignition condition is satisfied while the operating condition is the spark ignition operating condition, the operating condition is changed to the transition operating condition and the NOx is changed. It monitors whether a predetermined change occurs in the nitrogen oxide concentration detected by the sensor, and when a predetermined change occurs in the nitrogen oxide concentration,
Changing the operation state from the transition operation state to the self-ignition operation state; and when the predetermined concentration change does not occur in the nitrogen oxide concentration, the operation state is changed from the transition operation state to the spark ignition. 2. The spark ignition type internal combustion engine according to claim 1, wherein the internal combustion engine is returned to a normal operation state. 3. When the operating condition is determined to be not satisfied by the operating condition determining means in the operating condition, the operating condition is changed to the transition operating condition. It monitors whether a predetermined change occurs in the nitrogen oxide concentration detected by the NOx sensor, and when a predetermined change occurs in the nitrogen oxide concentration,
The operating state is changed from the transition operating state to the spark ignition operating state, and when a predetermined concentration change does not occur in the nitrogen oxide concentration, the operating state is changed from the transition operating state to the self-ignition. 2. The spark ignition type internal combustion engine according to claim 1, wherein the internal combustion engine is returned to a normal operation state. 4. When the operating condition is determined to be not satisfied by the operating condition determining means in the operating condition, the operating condition is changed to the operating condition for transition. It monitors whether a predetermined change occurs in the nitrogen oxide concentration detected by the NOx sensor, and when a predetermined change occurs in the nitrogen oxide concentration,
The operating state is changed from the operating state for transition to the operating state for spark ignition. If a predetermined concentration change does not occur in the nitrogen oxide concentration, it is determined that the self-ignition release condition is insufficient, and the spark is further determined. The spark ignition type internal combustion engine according to claim 1, wherein the operation state setting is changed to an ignition inducing side. 5. The method according to claim 2, wherein the predetermined concentration change of the nitrogen oxide concentration is a concentration change amount, a concentration change ratio, or a time change ratio of the concentration. A spark-ignition internal combustion engine as described. 6. The spark ignition type internal combustion engine according to claim 5, wherein a criterion for determining a concentration change amount, a concentration change ratio, or a concentration time change ratio of the nitrogen oxide concentration is provided for each operating condition. 7. The criterion for determining the self-ignition condition in the operating condition determining means is updated based on the monitoring result of the nitrogen oxide concentration.
A spark ignition type internal combustion engine according to any one of the preceding claims. 8. An ignition timing and an EGR amount as operation state parameters which are controlled to different values depending on a difference in each operation state between the spark ignition operation state, the self-ignition operation state, and the state transition operation state. The spark ignition type internal combustion engine according to any one of claims 1 to 7, wherein the internal combustion engine is any one of a fuel injection amount and a combination of at least two of them.