JP5744585B2 - Engine control device - Google Patents

Description

  The present invention relates to compression auto-ignition combustion means for operating an engine by compression auto-ignition combustion for compressing and self-igniting an air-fuel mixture in a combustion chamber, and compression spark ignition in the compression auto-ignition combustion by the compression auto-ignition combustion means. The present invention relates to an engine control device comprising combustion start timing control means for controlling the combustion start timing by spark-igniting an air-fuel mixture that has been discharged and compressed in the combustion chamber.

In the engine control device as described above, the combustion start timing may become unstable simply by performing the compression auto-ignition combustion by the compression auto-ignition combustion means. Therefore, the engine is operated by the compression auto-ignition combustion by the compression auto-ignition combustion means. In addition, the ignition plug is operated at a desired timing to cause a spark discharge by the combustion start timing control means to control the combustion start timing in the compression ignition combustion (see, for example, Patent Document 1). ).
The apparatus described in Patent Document 1 includes an ignition plug that sparks and ignites an air-fuel mixture compressed in a combustion chamber, so that the engine is not only operated by compression self-ignition combustion by a compression self-ignition combustion means. The engine is also operated by spark ignition combustion in which the spark plug is spark discharged at a desired time to spark ignite the air-fuel mixture compressed in the combustion chamber. When the engine load region is a high load region, the engine is operated by spark ignition combustion, and when the engine load region is a low load region, the engine is operated by compression self-ignition combustion. .

Japanese Patent No. 3873580

  In compression self-ignition combustion, by increasing the compression ratio and intake air temperature, the mixture temperature is raised to the ignition temperature inherent to the fuel, and the mixture (for example, a lean mixture having a low fuel concentration) is subjected to bulk combustion. Therefore, when spark spark is activated by spark ignition in compression auto-ignition combustion, the atmospheric pressure during spark discharge of the spark plug is high and the air-fuel mixture is also a lean air-fuel mixture, so the spark plug is required for spark ignition. The required voltage tends to increase. For this reason, there has been a problem that the deterioration of the spark plug progresses quickly and the durability of the spark plug decreases.

  The present invention has been made paying attention to this point, and an object of the present invention is to provide an engine control device capable of improving the durability of the spark plug while controlling the combustion start timing in the compression ignition combustion. Is to provide

In order to achieve this object, the characteristic configuration of the engine control device according to the present invention includes a compression auto-ignition combustion means for operating the engine by compression auto-ignition combustion that compresses and self-ignites an air-fuel mixture in a combustion chamber, and Engine control comprising combustion start timing control means for controlling the combustion start timing by spark ignition of the spark plug and spark ignition of the air-fuel mixture compressed in the combustion chamber in compression autoignition combustion by the compression autoignition combustion means In the device
Combustion state detection means for detecting the combustion state of the combustion chamber, and the combustion state detection in a state where the combustion is started by the compression autoignition combustion means and the combustion start timing is controlled by the combustion start timing control means. Based on detection information of the means, active combustion cycle determination means for determining an active combustion cycle in which the combustion state of the combustion chamber is in an active combustion state, and based on a determination result of the active combustion cycle determination means, Spark discharge stopping means for stopping spark discharge by the spark plug is provided in a cycle in which the combustion state is predicted to be an active combustion state.

  The engine repeats this cycle with a series of operations for performing each stroke in the order of the intake stroke, compression stroke, combustion / expansion stroke, and exhaust stroke. Therefore, the compressed self-ignition combustion means burns by performing compression auto-ignition combustion. In the case where the combustion start timing is controlled by the start timing control means, in each cycle, the ignition plug is sparked at the desired timing by the combustion start timing control means, and the air-fuel mixture in the combustion chamber is spark ignited for compression ignition. The combustion start time of combustion is controlled. In this case, in the active combustion cycle in which the combustion state of the combustion chamber is the active combustion state, the air-fuel mixture can be self-ignited at a desired time and combustion can be started without spark discharge of the spark plug. Therefore, according to this characteristic configuration, the active combustion cycle determining means determines the active combustion cycle based on the detection information of the combustion state detecting means, and the spark discharge stopping means is based on the determination result of the active combustion cycle determining means. The spark discharge by the spark plug is stopped in the cycle in which the combustion state of the combustion chamber becomes the active combustion state. As a result, it is possible to suppress the spark discharge of the spark plug in a state where the required voltage is increased, and to make the spark plug spark discharge by setting the cycle for stopping the spark discharge by the spark plug to be the active combustion cycle. Even if not, the combustion start timing can be controlled. Therefore, it is possible to improve the durability of the spark plug while controlling the combustion start timing in the compression auto-ignition combustion.

  According to a further characteristic configuration of the engine control device according to the present invention, the active combustion cycle determination means sets a period including a plurality of cycles as a determination target period, and detects the combustion state for each of the plurality of cycles in the determination target period. The detection information of the means is compared to determine the active combustion cycle during the determination target period.

  According to this feature configuration, the active combustion cycle determination means compares the detection information of the combustion state detection means in each cycle during the determination target period. For example, the combustion state in each cycle during the determination target period By calculating the average value of the detection values of the detection means and comparing the calculated average value with the detection value of the combustion state detection means in each cycle, how is the average combustion state during the determination target period? It is possible to grasp whether the combustion state is changing. Therefore, the active combustion cycle determination means can determine the active combustion cycle during the determination target period while considering the combustion state during the determination target period, and can appropriately determine the active combustion cycle.

According to a further characteristic configuration of the engine control device according to the present invention, the active combustion cycle determination means sets a period including a plurality of cycles as a determination target period, determines the active combustion cycle in the determination target period, and the spark. The discharge stop means uses, as a spark discharge stop cycle, a cycle in which the combustion state of the combustion chamber is predicted to be an active combustion state in the set period for spark discharge stop after the determination target period based on the determination result of the active combustion cycle determination means. The spark discharge by the spark plug is stopped in the spark discharge stop cycle.

Here, FIG. 2 is a graph of experimental results showing how the maximum pressure of the combustion chamber pressure in each cycle changes with time. FIG. 2 shows the change in the maximum cylinder pressure for 60 cycles, and the average value for the maximum cylinder pressure for 60 cycles is indicated by k, which is 2.5% higher than the average value k. The determined determination value is indicated by h. As a result, when the in-cylinder maximum pressure of a certain cycle is equal to or greater than the determination value h, the cycle is in an active combustion state, and the in-cylinder maximum pressure is less than the determination value h. The cycle is a cycle that does not become an active combustion state.
For example, as shown in FIG. 2, when a cycle that becomes an active combustion state occurs, the engine does not continue the cycle that becomes an active combustion state, but once it becomes a cycle that does not become an active combustion state, Again, the cycle becomes an active combustion state. Since such a phenomenon occurs periodically, the active combustion cycle determination means can detect the change in the in-cylinder maximum pressure in each cycle by setting the determination target period to 60 cycles, for example. Periodic changes between a cycle that is in an active combustion state and a cycle that is not in an active combustion state can be determined. Therefore, since the determination result of the active combustion cycle determination means reflects a periodic change between a cycle that is in the active combustion state and a cycle that is not in the active combustion state, the spark discharge stopping means is in the active combustion state. By using the determination result of the cycle determination means, it is possible to easily predict which cycle becomes the active combustion state and which cycle does not become the active combustion state in the spark discharge stop setting period. . Therefore, the spark discharge stopping means sets, as a spark discharge stop cycle, a cycle that can be predicted to become an active combustion state from the determination result of the active combustion cycle determination means, and stops the spark discharge by the spark plug in the spark discharge stop cycle. Therefore, while adopting a simple configuration of setting the spark discharge stop cycle, the cycle for stopping the spark discharge of the spark plug can be appropriately set to a cycle in which the combustion state of the combustion chamber becomes the active combustion state.

  The engine control device according to the present invention is further characterized in that the spark discharge stop means sets the reference according to the active combustion cycle from the determination result of the active combustion cycle determination means when setting the spark discharge stop cycle. A cycle is obtained, and the spark discharge stop cycle is set based on the obtained reference setting cycle.

  As described above, in the engine, there is a periodic change between the cycle that is in the active combustion state and the cycle that is not in the active combustion state. Therefore, when the reference setting cycle corresponding to the active combustion cycle is obtained, the reference setting cycle is determined. By using as a reference, it is possible to easily predict the cycle in which the active combustion state occurs. Therefore, according to this feature configuration, the spark discharge stopping means obtains a reference setting cycle corresponding to the active combustion cycle from the determination result of the active combustion cycle determining means, and performs the spark discharge stopping cycle based on the obtained reference setting cycle. Since it is set, the spark discharge stop cycle can be set easily and appropriately.

According to a further characteristic configuration of the engine control apparatus according to the present invention, the active combustion cycle determination unit is configured to detect the combustion state of the combustion chamber and the combustion state detection by the combustion state detection unit each time the determination period elapses. The determination of the active combustion cycle based on the detection result is repeatedly performed, and the spark discharge stopping unit is configured to determine whether the active combustion cycle is determined based on the determination result each time the active combustion cycle is determined by the active combustion cycle determination unit. The spark discharge by the spark plug is stopped in a cycle in which the combustion state is predicted to be an active combustion state.

  Since the combustion state in the combustion chamber changes with the passage of time and various combustion conditions, it is conceivable that the cycle in which the active combustion state is brought about also changes. Therefore, according to this feature configuration, the active combustion cycle determination unit repeatedly performs detection by the combustion state detection unit and determination of the active combustion cycle each time the determination period elapses, and the spark discharge stop unit includes the active combustion cycle. Each time the active combustion cycle is determined by the determining means, a process for stopping a new spark discharge based on the determination result is performed. As a result, even if the cycle in which the active combustion state is changed, the combustion start timing in the compression auto-ignition combustion can be controlled while flexibly responding to it, and the durability of the spark plug can be improved.

  A further characteristic configuration of the engine control device according to the present invention is to determine whether or not the combustion state in the combustion chamber is an unstable state. It is in the point provided with the cancellation means which stops the stop of discharge.

  When the spark discharge stopping means performs the process of stopping the spark discharge by the spark plug in the cycle in which the combustion state of the combustion chamber is in the active combustion state, the spark discharge by the spark plug is stopped, so that the combustion conditions, etc. In some cases, the combustion state of the combustion chamber may become unstable. Therefore, according to this feature configuration, when the canceling means determines that the combustion state of the combustion chamber is unstable, the spark discharge stopping means stops the spark discharge and the combustion state of the combustion chamber is stopped. Is prevented from becoming unstable.

Schematic configuration diagram of the engine The graph of the experimental result which showed how it changes with time progress about the maximum pressure among the pressure in a combustion chamber in each cycle. Flow chart showing the operation of the active combustion cycle determination means and the spark discharge stop means

As shown in FIG. 1, an engine 100 that controls operation by the engine control apparatus according to the present embodiment includes a cylinder 1 and a cylinder head 2 connected to an upper portion of the cylinder 1. The piston 5 connected to the crankshaft 4 via the connecting rod 3 is accommodated so as to be reciprocally movable in the vertical direction.
The combustion chamber 6 is formed by the top surface of the piston 5, the inner surface of the cylinder 1, and the lower surface of the cylinder head 2. An intake passage 7 and an exhaust passage 8 are opened in the combustion chamber 6, an intake valve 9 is provided on the intake passage 7 side of the combustion chamber 6, and an exhaust valve 10 is provided on the exhaust passage 8 side of the combustion chamber 6. ing. The cylinder head 2 is provided with a spark plug 11 at the approximate center of its lower surface.

  The engine 100 reciprocates the piston 5 in the cylinder 1 and opens and closes the intake valve 9 and the exhaust valve 10 to thereby perform an intake stroke, a compression stroke, a combustion / expansion stroke, and an exhaust stroke in the combustion chamber 6. Each process is performed sequentially. Thereby, the reciprocating motion of the piston 5 is output as a rotational motion of the crankshaft 4 by the connecting rod 3. Such a configuration is the same as that of a normal four-stroke internal combustion engine.

  The engine 100 uses gas fuel such as city gas (13A) as fuel. The intake passage 7 is supplied with fuel G to the air A that is supercharged by a supercharger (not shown) or the like and flows through the intake passage 7 to form an air-fuel mixture M; A throttle valve 13 having an adjustable passage cross-sectional area and a heating means 14 capable of heating the air-fuel mixture M supplied to the combustion chamber 6 are provided. Here, for the heating means 14, for example, a heat medium that collects exhaust heat of exhaust gas that circulates in the exhaust passage 8, or a mixture that circulates in the intake passage 7 and cooling water that has cooled the cylinder 1 and the like to high temperature. A heat exchanger that exchanges heat with the gas M, an electric heater, or the like can be used.

  Although not shown, the spark plug 11 is provided with a center electrode and a ground electrode facing each other at a tip portion (lower end portion in FIG. 1) with a gap between the center electrode and the ground electrode. By performing spark discharge, the air-fuel mixture M is configured to spark-ignite.

  The crankshaft 4 is provided with a crankshaft sensor 15 that detects a rotation angle and a rotation speed of the crankshaft 4. The cylinder head 2 is provided with a pressure sensor 16 (corresponding to combustion state detection means) that detects the pressure in the combustion chamber 6. An operation control unit 17 that controls the operation of the engine 100 is provided, and the detection information of the crankshaft sensor 15 and the detection information of the pressure sensor 16 are input to the operation control unit 17. The relationship between the engine output and the engine rotation speed is set in advance, and the operation control unit 17 obtains a target output as the engine output from the magnitude of the load and the like, and the relationship between the preset engine output and the engine rotation speed is obtained. The target rotational speed for outputting the target output is obtained from the relationship. The operation control unit 17 is configured to control the opening degree of the throttle valve 13 and the like so that the rotation speed detected by the crankshaft sensor 15 becomes the target rotation speed obtained.

  The operation control unit 17 compresses the air-fuel mixture M in the combustion chamber 6 and compresses the self-ignited combustion. The compressed self-igniting combustion means 18 operates the engine 100 by compressed self-ignition combustion. Combustion start timing control means 19 is provided for controlling the combustion start timing by spark-igniting the air-fuel mixture compressed in the combustion chamber 6 by spark discharge of the spark plug 11 during combustion.

The operation of engine 100 will be described.
In the engine 100, when the intake valve 9 is opened, the piston 5 descends from the top dead center TDC, whereby an intake stroke for sucking the air-fuel mixture M into the combustion chamber 6 is performed. Here, the intake passage 7 is provided with heating means 14 capable of heating the air-fuel mixture M supplied to the combustion chamber 6. The compression self-ignition combustion means 18 supplies the combustion chamber 6 so that the air-fuel mixture M is heated by the heating means 14 so that the air-fuel mixture M is compressed in the combustion chamber 6 and rises to a temperature capable of self-ignition. The supply air temperature of the air-fuel mixture M is controlled.

  Next, the engine 100 performs a compression stroke in which the air-fuel mixture M in the combustion chamber 6 is compressed by raising the piston 5 with the intake valve 9 closed. At this time, since the high-temperature air-fuel mixture M heated by the heating means 14 is sucked into the combustion chamber 6, the air-fuel mixture M is compressed and self-ignited in the combustion chamber 6 by performing a compression stroke. . However, the temperature of the air-fuel mixture M does not rise to a temperature at which self-ignition is possible at a desired time, and the combustion start time of compression self-ignition combustion may become unstable. Therefore, the combustion start timing control means 19 operates the spark plug 11 at a desired timing to cause spark discharge, thereby sparking the mixture M in the combustion chamber 6 and controlling the combustion start timing in the compression ignition combustion. Like to do.

  Next, in the engine 100, the air-fuel mixture M in the combustion chamber 6 is combusted and a combustion / expansion stroke is performed. Thereafter, the piston 5 ascends with the exhaust valve 10 opened, whereby the combustion chamber 6 A discharge process for discharging the exhaust gas E to the exhaust path 8 is performed. In this way, the engine 100 is configured to repeat this cycle with a series of operations for performing each stroke in the order of the intake stroke, the compression stroke, the combustion / expansion stroke, and the exhaust stroke as one cycle.

  In this way, the spark plug 11 is used to control the combustion start timing of the compression ignition combustion. However, if the ignition plug 11 is used in an atmosphere where the compression ignition combustion is performed, the required voltage increases. As a result, the durability of the spark plug 11 may be reduced. Therefore, in the present embodiment, the spark discharge by the spark plug 11 is stopped in the active combustion cycle in which the combustion state of the combustion chamber 6 becomes the active combustion state, thereby appropriately controlling the combustion start timing of the compression ignition combustion. However, the durability of the spark plug 11 is improved.

  As shown in FIG. 1, the operation control unit 17 includes an active combustion cycle determination unit 20 that performs a determination process for determining an active combustion cycle in which the combustion state of the combustion chamber 6 is an active combustion state, and a combustion state of the combustion chamber 6. Is provided with spark discharge stopping means 21 for performing a spark discharge stopping process for stopping the spark discharge by the spark plug 11 in a cycle in which the engine is in an active combustion state.

Based on FIG. 2, the active combustion cycle determination means 20 and the spark discharge stop means 21 will be described.
FIG. 2 shows a state in which the maximum pressure of the combustion chamber pressure in each cycle is elapsed with time in a state where the compression autoignition combustion means 18 performs compression autoignition and the combustion start timing control means 19 controls the combustion start timing. It is a graph of the experimental result which showed how it changed with it. FIG. 2 shows the change in the maximum in-cylinder pressure of 60 cycles, and the average value of the maximum in-cylinder pressure of 60 cycles is indicated by k, which is increased by 2.5% with respect to the average value k. The judgment value is indicated by h.

  When the combustion state in the combustion chamber 6 becomes an active combustion state, the in-cylinder maximum pressure at that time also rises. Therefore, by observing what value the in-cylinder maximum pressure is, the active combustion cycle Can be determined. Therefore, the active combustion cycle determination means 20 acquires the in-cylinder maximum pressure from the detection information of the pressure sensor 16 for each of a plurality of cycles in the determination target period (60 cycles shown in FIG. 2), and in each of these cycles The active combustion cycle during the determination target period is determined by comparing the in-cylinder maximum pressure.

  The active combustion cycle determination means 20 obtains an average value k of the in-cylinder maximum pressure during the determination target period from the in-cylinder maximum pressure in each cycle, and a determination value increased by 2.5% with respect to the average value k. h. When the maximum in-cylinder pressure of a certain cycle is greater than or equal to the determination value h, the active combustion cycle determination means 20 determines that the cycle is an active combustion cycle, and the maximum in-cylinder pressure of a certain cycle is the determination value h. If it is less than that, it is determined that the cycle is not in an active combustion state. As described above, the active combustion cycle determination unit 20 performs a plurality of cycles as a determination process in a state where the compression self-ignition combustion unit 18 performs compression self-ignition and the combustion start timing control unit 19 controls the combustion start timing. The including period is a determination target period (60 cycles in the case shown in FIG. 2), and the active combustion cycle in the determination target period is determined.

  In the cycle determined as the active combustion cycle by the active combustion cycle determination means 20, the combustion state of the combustion chamber 6 is the active combustion state. Therefore, even if the spark discharge by the spark plug 11 is stopped, it is more appropriate by the compression self-ignition. Combustion starts at the time. Therefore, in the spark discharge stopping process, the spark discharge stopping unit 21 determines that the combustion state of the combustion chamber 6 becomes an active combustion state in the spark discharge stop setting period after the determination target period based on the determination result of the active combustion cycle determining unit 20. The cycle is set as a spark discharge stop cycle, and the spark discharge by the spark plug 11 is stopped in the spark discharge stop cycle.

  As shown in FIG. 2, the active combustion cycle in which the in-cylinder maximum pressure is not less than the determination value h does not continuously occur, but the active combustion cycle in which the in-cylinder maximum pressure is not less than the determination value h and the in-cylinder maximum pressure. Is repeated with a cycle lower than the judgment value h. Accordingly, when setting the spark discharge stop cycle, the spark discharge stopping means 21 obtains a reference setting cycle Sa corresponding to the active combustion cycle from the determination result of the active combustion cycle determining means 20, and uses the obtained reference setting cycle as a reference. A spark discharge stop cycle S1 is set.

  That is, the spark discharge stopping means 21 is a cycle in which the in-cylinder maximum pressure is reduced from the determination value h or more to a value lower than the determination value h (in the previous cycle, the in-cylinder maximum pressure is the determination value h or more and In this cycle, the cycle in which the in-cylinder maximum pressure is less than the determination value h) is obtained as the reference setting cycle Sa. Then, the spark discharge stopping means 21 obtains the probability of a cycle that is equal to or greater than the determination value h for the nth cycle from the reference setting cycle Sa, and then determines that the determination value is equal to or greater than the determination value h for the n + 1th cycle from the reference setting cycle Sa. Find the probability of the cycle. In this way, the spark discharge stopping means 21 obtains the probability of a cycle that is greater than or equal to the determination value h while sequentially raising the nth order from the nth to the mth (for example, n = 1, m = 5). Repeat. The spark discharge stopping means 21 sets the cycle with the highest probability as the spark discharge stop cycle S <b> 1 among the calculated probabilities that are equal to or higher than the set probability (for example, 60%). In FIG. 2, since the third cycle from the reference setting cycle Sa is 85% and the fourth cycle from the reference setting cycle Sa is 15%, the third cycle from the reference setting cycle Sa is the spark discharge stop cycle. It is set as S1.

  Here, the setting of the spark discharge stop cycle S1 is performed on the condition that the obtained probability is equal to or higher than the set probability (for example, 60%), and there is only a cycle in which the obtained probability is less than the set probability (for example, 60%). Does not set the spark discharge stop cycle S1. When the obtained probability is less than the set probability (for example, 60%), a cycle that does not become an active combustion state is often set as a spark discharge stop cycle, and the combustion state of the combustion chamber 6 may become unstable. is there. Therefore, in such a case, the spark discharge stop cycle S1 is not set itself, and the durability of the spark plug 11 can be improved while preventing the combustion state of the combustion chamber 6 from becoming unstable. .

  In setting the spark discharge stop cycle, the spark discharge stopping means 21 sets a period having the same length as the determination target period immediately after the determination target period (1st to 60th cycle in FIG. 2). (In FIG. 2, the 61st to 120th cycles), and the spark discharge stop cycle S1 is set in the set period for stopping the spark discharge. And the spark discharge stop means 21 stops the spark discharge by the spark plug 11 in the spark discharge stop cycle S1 set in the set period for spark discharge stop (for example, the 61st to 120th cycles in the case shown in FIG. 2). . The spark discharge stop setting period is the same period as the determination target period immediately after the determination target period (1st to 60th cycle in FIG. 2), and the spark discharge stop setting period (61 to 120 in FIG. 2). Cycle), the spark discharge stop cycle S1 can be set based on the determination result of the active combustion cycle determination means 20 with the immediately preceding period as the determination target period, and the spark discharge stop cycle S1 is set appropriately. Can be done.

Hereinafter, based on the flowchart of FIG. 3, the operation of the active combustion cycle determination means 20 and the spark discharge stop means 21 will be described.
First, the active combustion cycle determination means 20 determines whether or not a determination period (for example, 1 minute) has elapsed (step # 1). In the case where the determination period has elapsed, the active combustion cycle determination means 20 illustrates the determination target period (in FIG. 2, the case where 60 cycles is set is illustrated, but here, for example, 100 cycles is set). Pressure data of the pressure sensor 16 for each of a plurality of cycles is detected (step # 2).

  When the active combustion cycle determination means 20 detects the pressure data of the pressure sensor 16, if the spark discharge stop means 21 performs a process for stopping the spark discharge in the spark discharge stop cycle S 1, the spark discharge stop means 21. The process of stopping the spark discharge is stopped, spark discharge by the spark plug 11 is performed in each cycle, the compression self-ignition combustion means 18 performs compression self-ignition, and the combustion start time control means 19 controls the combustion start time. Then, the pressure data of the pressure sensor 16 is detected.

  The active combustion cycle determination means 20 obtains the average value k and the determination value h from the pressure data detected during the determination target period, as described with reference to FIG. 2, and determines the active combustion cycle during the determination target period. (Step # 3).

  Then, the spark discharge stopping means 21 performs the spark discharge for a period of the same length as the determination target period immediately after the determination target period (for example, the first to 100th cycles) based on the determination result of the active combustion cycle determination means 20. The set period for stopping (for example, the 101st to 200th cycles when the start of the determination target period is the first cycle), and as described with reference to FIG. 2, the active combustion cycle determining means in the set period for stopping spark discharge A reference setting cycle Sa corresponding to the active combustion cycle is obtained from the determination result of 20 (step # 4).

  Further, as described with reference to FIG. 2, the spark discharge stopping means 21 obtains the probability of a cycle that is equal to or greater than the determination value h for the nth cycle from the reference setting cycle Sa, and the nth order from the nth. Repeatedly moving up to mth. Then, the spark discharge stopping means 21 uses the spark having the highest probability among the obtained probabilities that are equal to or higher than the set probability (for example, 60%) as the spark discharge stop cycle S1, and sparks for the set period for spark discharge stop. A setting process for the discharge stop cycle S1 is performed (step # 5). In this setting process, if all the obtained probabilities are less than the set probability (for example, 60%), the spark discharge stopping means 21 does not set the spark discharge stop cycle S1.

  When the spark discharge stop cycle S1 is set for the spark discharge stop setting period, the spark discharge stop means 21 stops the spark discharge in the spark discharge stop cycle S1 set in the spark discharge stop setting period ( Step # 7). The spark discharge stopping means 21 repeatedly performs the process of stopping the spark discharge in the spark discharge stop cycle S1 set in the spark discharge stop setting period every time a spark discharge stop setting period (for example, 100 cycles) elapses. . Thus, when the active combustion cycle determination during the determination target period is performed by the active combustion cycle determination means 20, the spark discharge stopping means 21 enters the spark discharge stop setting period based on the determination result. The process of stopping the spark discharge is repeated in the set spark discharge stop cycle S1.

  The active combustion cycle determination means 20 detects the combustion state of the combustion chamber 6 by the pressure sensor 16 (step # 2) and the active combustion cycle based on the detection result of the pressure sensor 16 every time a determination period (for example, 1 minute) elapses. This determination (step # 3) is repeated. Each time the active combustion cycle determination unit 20 determines the active combustion cycle, the spark discharge stopping unit 21 performs the setting process of the spark discharge stop cycle S1 based on the determination result, and ignites the spark discharge stop cycle S1. Spark discharge by the plug 11 is stopped (steps # 4 to # 7).

  When the spark discharge stopping means 21 is performing the process of stopping the spark discharge by the spark plug 11 in the spark discharge stop cycle S1, the stopping means 22 determines whether or not the combustion state in the combustion chamber 6 is unstable. In the unstable state, the spark discharge stopping means 21 stops the process of stopping the spark discharge in the spark discharge stop cycle S1 (steps # 8 and # 9).

The canceling means 22 will be described.
Although the spark discharge stopping means 21 stops the spark discharge by the spark plug 11 in the spark discharge stop cycle S1, the durability of the spark plug 11 can be improved, but the combustion state in the combustion chamber 6 is in an unstable state. There is a possibility. Therefore, as shown in FIG. 1, the operation control unit 17 determines whether or not the combustion state in the combustion chamber 6 is an unstable state. The stop means 22 which stops the stop of the spark discharge by is provided. The canceling means 22 obtains the indicated mean effective pressure using a combustion analysis device or the like, and the combustion state in the combustion chamber 6 is unstable when the rate of change in the indicated mean effective pressure is greater than or equal to a threshold value (eg, 3%). It is determined that it is in a state.

[Another embodiment]
(1) In the above embodiment, for the spark discharge stop setting period, a period having the same length as the determination target period immediately after the determination target period is set as the spark discharge stop setting period. For example, immediately after the determination target period After the set period elapses, a period having the same length as the determination target period can be set as the spark discharge stop set period. In this way, the period for setting the spark discharge stop period can be changed as appropriate, but the length of the period is the same length as the determination target period or an integer multiple of the determination target period. It is preferable to do this.

(2) In the above embodiment, every time the spark discharge stop setting period elapses, the spark discharge stopping means 21 repeats the process of stopping the spark discharge in the spark discharge stop cycle S1 set in the spark discharge stop setting period. However, it is only necessary that the spark discharge stopping means 21 performs the process of stopping the spark discharge at least once in the spark discharge stop cycle S1 set in the spark discharge stop setting period. For example, every time the spark discharge stop setting period elapses, a process of stopping the spark discharge in the spark discharge stop cycle S1 set in the spark discharge stop setting period and a process of stopping the process of stopping the spark discharge are performed. It can also be done alternately.

(3) In the above embodiment, the compression auto-ignition combustion means 18 controls the heating means 14 to control the supply temperature of the air-fuel mixture M supplied to the combustion chamber 6. Is compressed and self-ignited to be compressed and self-ignited and combusted, but by performing exhaust gas recirculation for returning a part of the exhaust gas in the exhaust passage 8 to the intake passage 7 and controlling the exhaust gas recirculation amount, The supply temperature of the mixture M supplied to the combustion chamber 6 can also be controlled.
In addition, in order to compress and self-ignite the air-fuel mixture M in the combustion chamber 6 to perform compression self-ignition combustion, instead of controlling the supply temperature of the air-fuel mixture M, the compression ratio or air-fuel mixture in the combustion chamber 6 is changed. Various combustion conditions such as the equivalence ratio of M can also be controlled, and what combustion conditions are controlled can be appropriately changed.

(4) In the above embodiment, as described with reference to FIG. 2, in setting the spark discharge stop cycle, the cycle in which the in-cylinder maximum pressure is decreased from the determination value h or higher to a value lower than the determination value h (one In the previous cycle, the in-cylinder maximum pressure is equal to or higher than the determination value h, and in this cycle, the in-cylinder maximum pressure is less than the determination value h) is obtained as the reference setting cycle Sa. A cycle in which the in-cylinder maximum pressure is equal to or higher than the determination value h can also be obtained as a reference setting cycle. In this case, in FIG. 2, since the probability that the fourth cycle from the reference setting cycle is equal to or greater than the determination value h is 85%, the fourth cycle from the reference setting cycle is set as the spark discharge stop cycle. .
As described above, how the spark discharge stop cycle is set in the setting period for stopping spark discharge can be appropriately changed.

(5) In the above embodiment, the combustion state detection means is used as the pressure sensor 16, and the active combustion cycle in which the combustion state of the combustion chamber is the active combustion state is determined using the in-cylinder maximum pressure of the combustion chamber pressure in each cycle. However, instead of the maximum in-cylinder pressure, the active combustion cycle in which the combustion state of the combustion chamber is the active combustion state is determined using the rate of increase in heat generation in each cycle and the center of gravity position of the heat generation rate. You can also.

  The present invention relates to compression auto-ignition combustion means for operating an engine by compression auto-ignition combustion for compressing and self-igniting an air-fuel mixture in a combustion chamber, and compression spark ignition in the compression auto-ignition combustion by the compression auto-ignition combustion means. A combustion start timing control means for controlling the combustion start timing by spark-igniting the air-fuel mixture that has been discharged and compressed in the combustion chamber, and can control the combustion start timing in the compression ignition combustion, It can be applied to various engine control devices that can improve the durability of the engine.

6 Combustion chamber 11 Spark plug 16 Pressure sensor (combustion state detection means)
18 Compression Autoignition Combustion Unit 19 Combustion Start Timing Control Unit 20 Active Combustion Cycle Determination Unit 21 Spark Discharge Stop Unit 22 Stop Unit 100 Engine

Claims (6)

In the compression self-ignition combustion means for operating the engine by compression self-ignition combustion for compressing and self-igniting the air-fuel mixture in the combustion chamber, and in the compression self-ignition combustion by the compression self-ignition combustion means, the spark plug is spark discharged to An engine control device comprising combustion start timing control means for controlling the combustion start timing by spark ignition of an air-fuel mixture compressed in a combustion chamber,
Combustion state detection means for detecting the combustion state of the combustion chamber, and the combustion state detection in a state where the combustion is started by the compression autoignition combustion means and the combustion start timing is controlled by the combustion start timing control means. Based on detection information of the means, active combustion cycle determination means for determining an active combustion cycle in which the combustion state of the combustion chamber is in an active combustion state, and based on a determination result of the active combustion cycle determination means, An engine control device comprising spark discharge stopping means for stopping spark discharge by the spark plug in a cycle in which the combustion state is predicted to be an active combustion state.   The active combustion cycle determination unit sets a period including a plurality of cycles as a determination target period, compares detection information of the combustion state detection unit for each of the plurality of cycles in the determination target period, and determines the period during the determination target period. The engine control apparatus according to claim 1, wherein the active combustion cycle is determined. The active combustion cycle determination unit sets a period including a plurality of cycles as a determination target period, determines the active combustion cycle in the determination target period, and the spark discharge stop unit determines the determination result of the active combustion cycle determination unit From the above, a cycle in which the combustion state of the combustion chamber is predicted to be an active combustion state in the set period for the spark discharge stop after the determination target period is set as a spark discharge stop cycle, and the spark by the spark plug is set in the spark discharge stop cycle. The engine control device according to claim 1 or 2, wherein the discharge is stopped.   In setting the spark discharge stop cycle, the spark discharge stop means obtains a reference setting cycle corresponding to the active combustion cycle from the determination result of the active combustion cycle determination means, and uses the obtained reference setting cycle as a reference. The engine control device according to claim 3, wherein a spark discharge stop cycle is set. The active combustion cycle determination means repeatedly performs the detection of the combustion state of the combustion chamber by the combustion state detection means and the determination of the active combustion cycle based on the detection result of the combustion state detection every time the determination period elapses, The spark discharge stopping unit performs the ignition in a cycle in which the combustion state of the combustion chamber is predicted to be an active combustion state based on the determination result every time the active combustion cycle is determined by the active combustion cycle determining unit. The engine control device according to any one of claims 1 to 4, wherein spark discharge by the plug is stopped.   And determining whether or not the combustion state in the combustion chamber is an unstable state. If the combustion state is an unstable state, the combustion chamber includes a stopping unit that stops the stop of the spark discharge by the spark discharge stopping unit. The engine control device according to any one of 1 to 5.

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