JP2015071984A - Premixing compression ignition type engine, and operation control method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology capable of: establishing a control index for appropriate combustion timing, the index indicating a variation in cycle variability; and positively and sufficiently achieving restriction over cycle variation under control of combustion timing in a premixing compression ignition type engine.SOLUTION: A total input calorific value Qi that is a heat generation amount of fuel supplied to a combustion chamber every 1 cycle is fed out and at the same time an in-cylinder heat generation amount Q that is an actual heat generation amount in the combustion chamber is monitored; a combustion timing detecting process in which a timing that an input reference combustion ratio that is a ratio of an in-cylinder heat generation amount Q to a total input calorific value Qi reaches a predetermined set combustion ratio (a) is detected as a premixing gas combustion timing Ti in the combustion chamber; and a combustion timing control for adjusting a prescribed operating condition influencing against a premixing gas combustion phase in such a way that a detected combustion timing Ti may be kept within a range of a prescribed target combustion timing is executed.

Description

The present invention performs premixed compression ignition combustion in which a premixed gas of fresh air and fuel is compressed and self-ignited and burned in the combustion chamber,
Combustion timing detection means for executing a combustion timing detection process for detecting the combustion timing of the premixed gas in the combustion chamber;
Operation control means for performing combustion timing control for adjusting predetermined operating conditions that affect the combustion phase of the premixed gas so that the combustion timing detected by the combustion timing detection means is maintained within a predetermined target combustion timing range The present invention relates to a premixed compression ignition type engine and an operation control method thereof.

As an engine that can achieve low pollution and high efficiency, a so-called premixed compression in which a premixed mixture of air and fuel is pre-mixed into the combustion chamber and the premixed mixture is self-ignited by adiabatic compression of the piston and burned. A premixed compression ignition type engine that performs ignition (HCCI) combustion is known (see, for example, Patent Documents 1 and 2).
Such a premixed compression ignition type engine can improve the efficiency by increasing the compression ratio, and can reduce the NOx by burning the fuel in a lean state. Has the merit that the premixed gas can be easily ignited and combusted even when gaseous fuel such as natural gas city gas is used.

In a premixed compression ignition engine, it is important that the premixed gas is self-ignited at an appropriate time in the vicinity of the top dead center in the combustion chamber in order to maintain stable operation and further improve the efficiency. However, the self-ignition timing of a premixed compression ignition engine differs from a spark ignition engine that can actively determine the spark ignition timing, and varies depending on slight disturbances such as the temperature, pressure, concentration, and components of the premixed gas. To do.
Therefore, in the conventional premixed compression ignition type engine described in Patent Documents 1 and 2, etc., in order to maintain appropriate self-ignition near the top dead center and to suppress cycle fluctuation due to knocking, misfire, etc. While performing the combustion timing detection process for sequentially detecting the combustion timing of the premixed gas in the combustion chamber, the internal EGR amount is changed to adjust the temperature of the premixed gas in the combustion chamber, or a spark is applied to the combustion chamber. In order to adjust the predetermined operating conditions that affect the actual combustion phase of the premixed gas, such as inducing self-ignition, the detected combustion timing is within the predetermined target combustion timing range. The combustion timing control to be controlled is executed.
In the combustion timing detection processing of these conventional premixed compression ignition engines, in-cylinder heat generation, which is the actual heat generation in the combustion chamber, is monitored when detecting the combustion timing of the premixed gas in the combustion chamber. Then, with reference to the total in-cylinder heat generation amount obtained by accumulating the in-cylinder heat generation amount over the entire combustion process, the combustion timing of the premixed gas is detected using the progress of the in-cylinder heat generation amount.
Specifically, the heat generation rate (heat generation rate) in the combustion chamber is sequentially obtained from the volume of the combustion chamber that can be obtained from the crank angle and the in-cylinder pressure measured by the in-cylinder pressure sensor. The integral in the combustion process up to the time is obtained sequentially as the amount of heat generated in the cylinder. Then, the in-cylinder heat generation amount is accumulated over the entire combustion process to obtain the total in-cylinder heat generation amount, and the cylinder is the ratio of the in-cylinder heat generation amount up to that time with respect to the total in-cylinder heat generation amount. The in-cylinder reference combustion ratio is sequentially obtained, and the in-cylinder reference combustion timing at which the in-cylinder reference combustion ratio reaches a predetermined set ratio such as 50% is detected as the combustion timing of the premixed gas in the combustion chamber. .

JP2013-133814A JP 2008-057407 A

  In a premixed compression ignition type engine, experimental data when the combustion phase is changed by changing the intake air temperature while keeping the equivalence ratio (air-fuel ratio) of the premixed gas constant are shown in FIGS. In a premixed compression ignition type engine, generally, when the intake air temperature rises, the combustion phase is advanced, and when the intake air temperature is lowered, the combustion phase is delayed.

FIG. 3 shows the in-cylinder reference combustion timing when the in-cylinder reference combustion ratio reaches 50% (hereinafter referred to as “in-cylinder reference combustion ratio 50% timing”), and the coefficient of variation of the illustrated effective pressure (hereinafter “cycle variation coefficient”). And the relationship. As can be seen from the experimental results, when the in-cylinder reference combustion rate 50% is delayed after 10 (deg. ATDC), the cycle variation coefficient increases rapidly. In such a state, it becomes difficult to control the in-cylinder reference combustion ratio 50% timing within the target combustion timing range in the combustion timing control.
FIG. 4 shows a history of the heat generation rate of the combustion chamber with respect to the crank angle at the time of each in-cylinder reference combustion ratio of 50%. FIG. 5 shows the relationship between the in-cylinder reference combustion rate 50% and the total in-cylinder heat generation amount. As can be seen from these experimental results, when the in-cylinder reference combustion rate 50% is delayed after 10 (deg. ATDC), the total in-cylinder heat generation amount decreases rapidly. In other words, the combustion efficiency, which is the ratio of the total in-cylinder heat generation amount to the total input heat generation amount, which is the total heat generation amount of the fuel supplied to the combustion chamber in one cycle, rapidly decreases. On the other hand, the delay width at the time of the in-cylinder reference combustion ratio 50% with respect to the decrease in the total in-cylinder heat generation amount gradually decreases.
That is, in the premixed compression ignition type engine, in a state where the combustion phase is greatly delayed, the combustion efficiency actually decreases and the cycle fluctuation increases. However, this increase in cycle fluctuation does not appear accurately as a change in the 50% timing of the in-cylinder reference combustion ratio based on the total in-cylinder heat generation amount, or the change in cycle fluctuation is difficult to distinguish. Become. Therefore, the in-cylinder reference combustion ratio 50% timing, which is the combustion timing based on the total in-cylinder heat generation amount accumulated during the entire combustion process, is a control index for the combustion timing in premixed compression ignition combustion. Can be said to be inappropriate.
Therefore, in a premixed compression ignition type engine, it is desired to establish an appropriate control index for the combustion timing that can show changes in cycle fluctuations.

  The present invention has been made paying attention to such a point, and an object of the present invention is to establish an appropriate combustion timing control index capable of expressing changes in cycle fluctuations in a premixed compression ignition type engine, The object is to provide a technique capable of reliably and sufficiently realizing suppression of cycle fluctuation by control.

In order to achieve this object, a premixed compression ignition engine according to the present invention comprises:
In the combustion chamber, premixed compression ignition combustion is performed in which a premixed gas of fresh air and fuel is compressed and self-ignited to burn.
Combustion timing detection means for executing a combustion timing detection process for detecting the combustion timing of the premixed gas in the combustion chamber;
Operation control for performing combustion timing control for adjusting predetermined operating conditions that affect the combustion phase of the premixed gas so that the combustion timing detected by the combustion timing detection means is maintained within a predetermined target combustion timing range A premixed compression ignition engine comprising means,
Its feature configuration is
In the combustion timing detection process, the combustion timing detection means derives a total input calorific value that is the sum of the calorific values of fuel supplied to the combustion chamber every cycle, and the actual heat generation amount in the combustion chamber. A certain amount of in-cylinder heat generation is monitored, and the time when the input reference combustion ratio, which is the ratio of the in-cylinder heat generation amount to the total input heat generation amount, reaches a predetermined set combustion ratio is detected as a combustion timing. is there.

According to this feature configuration, when detecting the combustion timing of the premixed gas in the combustion chamber in the combustion timing detection process, the total in-cylinder heat generation amount obtained by accumulating the in-cylinder heat generation amount over the entire combustion process is used as a reference. Rather than using the in-cylinder reference combustion rate obtained as follows, the input reference combustion rate obtained based on the total input calorific value, which is the total calorific value of the fuel supplied to the combustion chamber in one cycle, is used.
That is, referring to FIG. 2, the in-cylinder heat generation amount Q, which is the actual heat generation amount in the combustion chamber obtained sequentially, is successively monitored, and conventionally, it is sequentially monitored as the actual heat generation amount in the combustion chamber. The in-cylinder heat generation amount Q is a time when the in-cylinder heat generation amount Q reaches a predetermined set ratio a with respect to the total in-cylinder heat generation amount Qs obtained by accumulating the in-cylinder heat generation amount over the entire combustion process. It is detected as the combustion timing of the premixed gas.
On the other hand, in the combustion timing detection process of this feature configuration, the in-cylinder heat generation amount Q that is successively monitored as the actual heat generation amount in the combustion chamber is the calorific value of the fuel supplied to the combustion chamber every cycle. The input reference combustion timing Ti, which is a time when the predetermined set ratio a is reached with respect to the total input calorific value Qi, which is the sum of the above, is detected as the combustion timing of the premixed gas.

FIG. 3 shows experimental data when the combustion timing is changed by changing the intake air temperature while keeping the equivalence ratio of the premixed gas constant, and the in-cylinder reference combustion ratio as an example of the in-cylinder reference combustion timing Ts is shown. An in-cylinder reference combustion ratio 50% period, which has reached 50%, and an input reference combustion ratio 50% period, in which the input reference combustion ratio as an example of the input reference combustion period Ti has reached 50%, respectively. The relationship with the cycle variation coefficient in is shown.
As can be seen from this experimental data, in the input reference combustion timing Ti, as compared with the in-cylinder reference combustion timing Ts, the increase in the cycle variation coefficient when the combustion phase is delayed becomes gradual. Therefore, for the input reference combustion timing Ti, a relatively wide control range with respect to the variation of the cycle variation coefficient is secured, and the change in the cycle variation coefficient appears accurately as the change in the input reference combustion timing Ti. As a result, it becomes easy to discriminate changes in the cycle variation coefficient.
Therefore, according to the present invention, in the premixed compression ignition type engine, by using the input combustion timing as an appropriate combustion timing control index capable of expressing the variation of the cycle variation, the cycle variation can be reliably suppressed by the combustion timing control. It can be fully realized.

A further characteristic configuration of the premixed compression ignition engine according to the present invention is as follows:
A fuel supply amount measuring means for measuring the fuel supply amount to the combustion chamber;
In the combustion timing detection process, the combustion timing detection means derives the total input calorific value from the total fuel supply amount that is the sum of the fuel supply amounts measured by the fuel supply amount measurement means for each cycle. .

  According to this characteristic configuration, in the combustion timing detection process, the fuel supply amount to the combustion chamber measured by the fuel supply amount measuring means is obtained in the intake stroke when acquiring the total input heat generation amount used for detection of the input reference combustion timing. If the total fuel supply amount that is the sum of the fuel supply amount per cycle is obtained by accumulating the fuel supply amount as a whole, the total input heat generation is performed by multiplying the total fuel supply amount by the unit calorific value of the fuel. The amount can be acquired.

A further characteristic configuration of the premixed compression ignition engine according to the present invention is as follows:
In-cylinder pressure measuring means for measuring the in-cylinder pressure that is the pressure of the combustion chamber,
In the combustion timing detection process, the combustion timing detection means integrates an integral amount obtained by integrating the heat generation rate obtained from the cylinder pressure measured by the cylinder pressure measurement means and the volume of the combustion chamber in the combustion process. The point is to monitor as a quantity.

  According to this feature configuration, in the combustion timing detection process, when acquiring the in-cylinder heat generation amount used for detection of the input reference combustion timing, measurement is performed by the in-cylinder pressure measuring means with respect to the volume change of the combustion chamber in the compression stroke and the expansion stroke. By analyzing the in-cylinder pressure change, the heat generation rate in the combustion chamber is obtained, and the heat generation rate in the cylinder can be sequentially acquired in such a manner that the heat generation rate is integrated in the combustion process up to that time.

A further characteristic configuration of the premixed compression ignition engine according to the present invention is as follows:
The operation control means, in the combustion timing control, as the operating conditions, the temperature of fresh air sucked into the combustion chamber, the pressure of fresh air sucked into the combustion chamber, the actual compression ratio of the combustion chamber, the equivalent of premixed gas This is to adjust at least one of the ratio, the exhaust gas recirculation rate, and the spark generation timing of the auxiliary spark plug provided in the combustion chamber.

According to this characteristic configuration, the operating condition that is adjusted by the combustion timing control to affect the actual combustion phase of the premixed gas in the combustion chamber and to suppress cycle fluctuations is the new intake air to the combustion chamber. The temperature of the air (hereinafter referred to as “intake air temperature”), the pressure of fresh air taken into the combustion chamber (hereinafter referred to as “intake pressure”), the actual compression ratio of the combustion chamber, the equivalence ratio of the premixed air, At least one of the spark generation times of the auxiliary spark plug provided can be used.
For example, if the intake pressure is adjusted, or if the actual compression ratio is adjusted by adjusting the closing timing of the intake valve, the pressure of the premixed gas before self-ignition in the combustion chamber changes, and the premixed gas Since the timing of self-ignition changes, as a result, the combustion timing of the premixed gas can be adjusted.
Further, if the intake air temperature is adjusted, the temperature of the premixed gas before self-ignition in the combustion chamber changes, and as a result, the combustion timing of the premixed gas can be adjusted.
Also, if the mixing ratio of fuel to fresh air is adjusted and the equivalence ratio of the premixed gas is adjusted, the timing of self-ignition of the premixed gas and the combustion speed in the combustion chamber will change. The combustion time can be adjusted.
Further, when exhaust gas recirculation (EGR) is adopted and the exhaust gas recirculation rate (EGR rate) obtained as a ratio of the exhaust gas recirculation amount to the intake air amount is adjusted, the oxygen concentration and the inert gas concentration in the premixed gas Changes, and the timing of self-ignition of the premixed gas and the combustion speed change. As a result, the combustion timing of the premixed gas can be adjusted.
In addition, by providing an auxiliary spark plug capable of generating sparks in the combustion chamber and adjusting the spark generation timing of the auxiliary spark plug, the timing at which self-ignition of the premixed gas is induced in the combustion chamber by the spark changes. As a result, the combustion timing of the premixed gas can be adjusted.

Moreover, the operation control method of the premixed compression ignition engine according to the present invention for achieving this object is as follows:
In a premixed compression ignition type engine that performs premixed compression ignition combustion in which a premixed mixture of fresh air and fuel is compressed and self-ignited and combusted in a combustion chamber,
A combustion timing detection process for detecting the combustion timing of the premixed gas in the combustion chamber;
Preliminary execution of combustion timing control for adjusting predetermined operating conditions that affect the combustion phase of the premixed gas so that the combustion timing detected in the combustion timing detection processing is maintained within a predetermined target combustion timing range. An operation control method for a mixed compression ignition engine,
Its feature configuration is
In the combustion timing detection process, a total input calorific value that is the sum of the calorific values of the fuel supplied to the combustion chamber per cycle is derived, and an in-cylinder heat generation amount that is an actual heat generation amount in the combustion chamber And the time when the input reference combustion ratio, which is the ratio of the in-cylinder heat generation amount to the total input heat generation amount, reaches a predetermined set combustion ratio is detected as the combustion timing.

  According to this characteristic configuration, the same combustion timing detection process and combustion timing control as those performed by the premixed compression ignition type engine according to the present invention are executed. Therefore, similarly to the premixed compression ignition type engine according to the present invention. In the premixed compression ignition type engine, by using the input combustion timing as an appropriate combustion timing control index that can show changes in cycle variation, the suppression of cycle variation by combustion timing control is realized reliably and sufficiently. Can do.

Schematic configuration diagram of a premixed compression ignition engine in the present embodiment Diagram explaining the definition of in-cylinder reference combustion timing and input reference combustion timing The graph which shows the relationship of the cycle variation coefficient with respect to each of the in-cylinder reference combustion timing and the input reference combustion timing The graph which shows the history of the heat generation rate with respect to the crank angle in the cylinder standard combustion timing Graph showing the relationship between in-cylinder reference time and total in-cylinder heat generation

Embodiments of the present invention will be described with reference to the drawings.
A premixed compression ignition type engine (hereinafter simply referred to as “engine”) 1 shown in FIG. 1 has a cylinder 2 and a cylinder head 3 connected to the upper portion of the cylinder 2. The piston 4 connected to the crankshaft 6 via the connecting rod 5 is accommodated so as to be reciprocally movable. A combustion chamber 10 is formed by the top surface of the piston 4, the inner surface of the cylinder 2, and the lower surface of the cylinder head 3. An intake passage 21 and an exhaust passage 31 are opened in the combustion chamber 10, an intake valve 20 is provided on the intake passage 21 side of the combustion chamber 10, and an exhaust valve 30 is provided on the exhaust passage 31 side of the combustion chamber 10. ing.

  In the intake passage 21 of the engine 1, a mixer that forms a premixed gas M by mixing the fuel A, which is natural gas, with the air A flowing through the intake passage 21 together with the supply amount adjustment by the fuel supply valve 24. 23 is provided. In addition, a throttle valve 22 that can adjust the intake amount of the premixed gas M to the combustion chamber 10 by adjusting the opening is provided on the downstream side of the mixer 23 in the intake passage 21. Further, on the downstream side of the throttle valve 22 in the intake passage 21, a heat exchanger that heats the premixed gas M sucked into the combustion chamber 10 by heat exchange with a relatively high temperature (for example, 80 ° C.) engine cooling water CW. 25 is provided. Then, the premixed gas M that has passed through the heat exchanger 25 is sucked into the combustion chamber 10.

Then, when the piston 4 is lowered from the top dead center with the intake valve 20 opened, an intake stroke for intake of the premixed gas M from the intake passage 21 to the combustion chamber 10 is performed. When the piston 4 rises in a state in which 20 is closed, a compression stroke for compressing the premixed gas M in the combustion chamber 10 is performed.
In the latter stage of the compression stroke, the premixed gas M is heated by adiabatic compression, the oxidation reaction of the fuel F proceeds, and when the temperature rises to the ignition temperature of the fuel F where the chain branching reaction occurs, self-ignition occurs. So-called HCCI combustion, in which the premixed gas M burns, is performed.
In the expansion stroke following the compression stroke, the piston 4 is lowered due to the increase in the volume of the combustion chamber 10 accompanying the combustion of the premixed gas M, and in the subsequent exhaust stroke, the piston 4 is opened with the exhaust valve 30 opened. By rising, the exhaust gas E in the combustion chamber 10 is discharged to the exhaust passage 31.
In this way, the engine 1 is configured to repeatedly perform a series of operations for performing each stroke in the order of the intake stroke, the compression stroke, the expansion stroke, and the exhaust stroke.

Further, a cooling water supply amount adjusting valve 26 capable of adjusting the supply amount of engine cooling water to the heat exchanger 25 provided in the intake passage 21 is provided. The cooling water supply amount adjusting valve 26 adjusts the amount of cooling water supplied to the heat exchanger 25 to adjust the heating capacity of the heat exchanger 25 with respect to the premixed gas M, so that fresh air is supplied to the combustion chamber 10. It functions as an intake air temperature adjusting means for adjusting the intake air temperature, which is the temperature of the premixed air M to be sucked.
Further, by adjusting the temperature of the premixed gas M sucked into the combustion chamber 10 by the cooling water supply amount adjusting valve 26, the temperature of the premixed gas M at the time of compression in the combustion chamber 10 changes. The combustion timing of the premixed gas M can be adjusted.
That is, it can be said that the temperature of the premixed gas M adjusted by the cooling water supply amount adjusting valve 26 is an operating condition that affects the combustion phase of the premixed gas M in the combustion chamber 10. 26 can be said to be a combustion timing adjusting means capable of adjusting the combustion timing of the premixed gas M in the combustion chamber 10 by changing the operating conditions.

  In the engine 1, as various sensors, an in-cylinder pressure sensor 8 (an example of an in-cylinder pressure measuring unit) that measures an in-cylinder pressure that is a pressure in the combustion chamber 10, and a crank angle sensor 7 that measures a crank angle that is an angle of the crankshaft 6. A fuel supply amount sensor 9 (an example of a fuel supply amount measuring unit) that measures the flow rate of the fuel F flowing through the fuel supply valve 24 as a fuel supply amount to the combustion chamber 10 is provided.

  Various controls of the engine 1 are performed by an ECU (Engine Control Unit) 50. The ECU 50 executes a predetermined computer program to detect the combustion timing of the premixed gas M in the combustion chamber 10. Combustion timing detection means 51 for performing detection processing, and adjusting the intake air temperature, which is a predetermined operating condition that affects the combustion phase of the premixed gas, to determine the combustion timing detected by the combustion timing detection means 51 as a predetermined target combustion timing It functions as the operation control means 52 etc. for executing the combustion timing control etc. maintained within the range.

  The operation control means 52 is generated by the mixer 23 by controlling the opening of the fuel supply valve 24 based on the oxygen concentration of the exhaust gas E detected by an oxygen sensor (not shown) simultaneously with the combustion timing control. The air-fuel ratio control for maintaining the equivalent ratio (air-fuel ratio) of the premixed gas M to be a fuel-lean desired target equivalent ratio suitable for HCCI combustion, and the rotation of the crankshaft 6 obtained from the detection result of the crank angle sensor 7 Various controls such as rotational speed maintenance control for controlling the opening degree of the throttle valve 22 are performed so that the speed is maintained at a desired rotational speed.

In the combustion timing detection process executed by the combustion timing detection means 51, referring to FIG. 2 as well, the change state of the in-cylinder pressure detected by the in-cylinder pressure sensor 8 while referring to the crank angle θ detected by the crank angle sensor 7. By analyzing the above, the in-cylinder heat generation amount Q, which is the actual heat generation amount in the combustion chamber 10, is sequentially derived and monitored.
Specifically, as shown in the following [Equation 1], the volume V of the combustion chamber 10 is obtained from the crank angle θ, and the volume change (dV / dθ) and the in-cylinder pressure change (dP / dθ) in the compression stroke and the expansion stroke. From this, the heat generation rate (dQ / dθ) in the combustion chamber 10 is obtained.
Then, the in-cylinder heat generation amount Q is sequentially acquired in such a manner that the heat generation rate (dQ / dθ) is integrated in the combustion process up to the crank angle θ at that time.

At the same time, while referring to the crank angle θ detected by the crank angle sensor 7, the combustion timing detection means 51 integrates the fuel supply amount to the combustion chamber 10 measured by the fuel supply amount sensor 9 for each cycle. The fuel supplied to the combustion chamber 10 every cycle is calculated by calculating the total fuel supply amount, which is the sum of the fuel supply amounts per cycle, and multiplying the total fuel supply amount by the unit heating value of the fuel F. A total input calorific value Qi, which is the total calorific value of F, can be derived.
Then, the combustion timing detection means 51 inputs the timing when the charging reference combustion ratio, which is the ratio of the in-cylinder heat generation amount up to that timing with respect to the total input heat generation amount, reaches a predetermined set combustion ratio a such as 50%. It is detected as the reference combustion time Ti.

Next, in the combustion timing control executed by the operation control means 52, the intake air temperature, which is an operating condition that affects the combustion phase of the premixed gas M, is adjusted by the cooling water supply amount adjustment valve 26, and the combustion timing detection means. The injection reference combustion timing Ti detected at 51 is controlled within a predetermined target combustion timing range near top dead center (for example, within a range of 8 deg.ATDC to 12 deg.ATDC).
Specifically, when the input reference combustion timing Ti is late with respect to the target combustion timing range, the opening degree of the cooling water supply amount adjustment valve 26 is increased, the intake air temperature is increased, and the premixed gas M is burned. Make the phase early. Conversely, when the input reference combustion timing Ti is earlier than the target combustion timing range, the opening degree of the cooling water supply amount adjustment valve 26 is reduced, the intake air temperature is lowered, and the combustion phase of the premixed gas M is changed. Delay it. As a result, the input reference combustion timing Ti is maintained within the target combustion timing range, and knocking, misfire, etc. are avoided, and cycle fluctuations are suppressed.

[Other Embodiments]
Finally, other embodiments of the present invention will be described. Note that the configuration of each embodiment described below is not limited to being applied independently, and can be applied in combination with the configuration of other embodiments as long as no contradiction arises.

(1) In the above embodiment, the combustion chamber 10 is adjusted by adjusting the opening of the cooling water supply amount adjustment valve 26 that can adjust the supply amount of engine cooling water to the heat exchanger 25 provided in the intake passage 21. The intake air temperature, which is the temperature of the premixed gas M sucked into the intake air, is adjusted. For example, the intake air temperature may be adjusted by adjusting the heating output of the electric heater provided in the intake passage 21.

(2) In the above embodiment, the intake air temperature is used as the predetermined operating condition that affects the combustion phase of the premixed gas M. However, the intake air temperature can be changed by adjusting the rotation speed of the supercharger. The actual compression ratio of the combustion chamber 10 that can be changed by adjusting the pressure of the mixture M, the closing timing of the intake valve, the equivalence ratio of the premixed gas that can be changed by adjusting the opening of the fuel supply valve 24, and exhaust gas recirculation The rate (EGR rate) and the like can also be used as predetermined operating conditions that affect the combustion phase of the premixed gas M since the combustion timing of the premixed gas M can be adjusted by changing these.
In addition, if an auxiliary spark plug capable of generating a spark is provided in the combustion chamber 10 and the spark generation timing of the auxiliary spark plug is adjusted, the timing at which self-ignition of the premixed gas is induced by the spark in the combustion chamber 10 is achieved. As a result, since the combustion timing of the premixed gas M can be adjusted, the spark generation timing of the auxiliary spark plug can also be used as a predetermined operating condition that affects the combustion phase of the premixed gas M.

(3) In the above embodiment, the fuel supply amount sensor 9 that directly measures the fuel supply amount to the combustion chamber 10 is provided, but the opening of the fuel supply valve 24, the opening of the throttle valve 22, the engine speed and the load From such information, the fuel supply amount to the combustion chamber 10 may be obtained indirectly.

(4) In the above embodiment, the heat generation rate for determining the in-cylinder heat generation amount in the combustion chamber 10 is determined using the in-cylinder pressure measured by the in-cylinder pressure sensor 8 and the volume of the combustion chamber 10. A temperature sensor that measures the temperature of the combustion chamber 10 may be provided instead of the in-cylinder pressure sensor 8, and the heat generation rate may be obtained using the in-cylinder temperature measured by the temperature sensor and the volume of the combustion chamber 10.

The present invention performs premixed compression ignition combustion in which a premixed gas of fresh air and fuel is compressed and self-ignited and burned in the combustion chamber,
Combustion timing detection means for executing a combustion timing detection process for detecting the combustion timing of the premixed gas in the combustion chamber;
Operation control means for performing combustion timing control for adjusting predetermined operating conditions that affect the combustion phase of the premixed gas so that the combustion timing detected by the combustion timing detection means is maintained within a predetermined target combustion timing range Can be suitably used as a premixed compression ignition type engine and an operation control method.

1: Engine 7: Crank angle sensor 8: In-cylinder pressure sensor (in-cylinder pressure measuring means)
9: Fuel supply amount sensor (fuel supply amount measuring means)
10: Combustion chamber 24: Fuel supply valve 26: Cooling water supply amount adjusting valve (intake air temperature adjusting means)
50: ECU
51: Combustion timing detection means 52: Operation control means A: Air CW: Engine cooling water F: Fuel M: Premixed gas

Claims (5)

In the combustion chamber, premixed compression ignition combustion is performed in which a premixed gas of fresh air and fuel is compressed and self-ignited to burn.
Combustion timing detection means for executing a combustion timing detection process for detecting the combustion timing of the premixed gas in the combustion chamber;
Operation control for performing combustion timing control for adjusting predetermined operating conditions that affect the combustion phase of the premixed gas so that the combustion timing detected by the combustion timing detection means is maintained within a predetermined target combustion timing range A premixed compression ignition engine comprising means,
In the combustion timing detection process, the combustion timing detection means derives a total input calorific value that is the sum of the calorific values of fuel supplied to the combustion chamber every cycle, and the actual heat generation amount in the combustion chamber. Premixing that monitors the amount of heat generated in a cylinder and detects when the input reference combustion ratio, which is the ratio of the amount of heat generated in the cylinder with respect to the total amount of generated heat, reaches a predetermined set combustion ratio as the combustion timing Compression ignition engine. A fuel supply amount measuring means for measuring the fuel supply amount to the combustion chamber;
2. The combustion timing detection means derives the total input heat generation amount from a total fuel supply amount that is a total for each cycle of the fuel supply amount measured by the fuel supply amount measurement means in a combustion timing detection process. The premixed compression ignition engine described in 1. In-cylinder pressure measuring means for measuring the in-cylinder pressure that is the pressure of the combustion chamber,
In the combustion timing detection process, the combustion timing detection means integrates an integral amount obtained by integrating the heat generation rate obtained from the cylinder pressure measured by the cylinder pressure measurement means and the volume of the combustion chamber in the combustion process. The premixed compression ignition engine according to claim 1 or 2, which is monitored as a quantity.   The operation control means, in the combustion timing control, as the operating conditions, the temperature of fresh air sucked into the combustion chamber, the pressure of fresh air sucked into the combustion chamber, the actual compression ratio of the combustion chamber, the equivalent of premixed gas The premixed compression ignition engine according to any one of claims 1 to 3, wherein at least one of a ratio, an exhaust gas recirculation rate, and a spark generation timing of an auxiliary spark plug provided in the combustion chamber is adjusted. In a premixed compression ignition type engine that performs premixed compression ignition combustion in which a premixed mixture of fresh air and fuel is compressed and self-ignited and combusted in a combustion chamber,
A combustion timing detection process for detecting the combustion timing of the premixed gas in the combustion chamber;
Preliminary execution of combustion timing control for adjusting predetermined operating conditions that affect the combustion phase of the premixed gas so that the combustion timing detected in the combustion timing detection processing is maintained within a predetermined target combustion timing range. An operation control method for a mixed compression ignition engine,
In the combustion timing detection process, a total input calorific value that is the sum of the calorific values of the fuel supplied to the combustion chamber per cycle is derived, and an in-cylinder heat generation amount that is an actual heat generation amount in the combustion chamber Operation of a premixed compression ignition engine that detects when the input reference combustion ratio, which is the ratio of the in-cylinder heat generation amount with respect to the total input heat generation amount, reaches a predetermined set combustion ratio as the combustion timing Control method.

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