JP6848919B2 - Engine control method and control device - Google Patents

Description

The present invention relates to and control device controls how the engine having a cylinder mixture of air and fuel containing gasoline is burned.

Conventionally, in the field of an engine, it is known that abnormal combustion called knocking may occur locally when an engine load is high or the like. For knocking, various measures are taken to prevent knocking with high pressure in the cylinder from occurring. Specifically, under the condition that the engine load is high and the temperature in the combustion chamber is high, the air-fuel mixture of fuel and air self-ignites and burns in the outer periphery of the combustion chamber separately from the main combustion, and a high pressure wave is generated and knocking occurs. That is, vibration of the cylinder and the piston occurs. When knocking occurs, noise may increase and the piston or the like may be damaged, and it is required to prevent this.

For example, in Patent Document 1, a knock sensor for detecting knocking is provided in the engine body, and when knocking is detected by the knock sensor, the ignition timing is retarded to avoid the occurrence of knocking. It is disclosed.

Japanese Unexamined Patent Publication No. 2008-291758

In the method of detecting knocking using a knock sensor, it is found that knocking is likely to occur only after knocking occurs. Therefore, it is possible to avoid only the continuous occurrence of knocking, and it is not possible to prevent the occurrence of knocking itself. That is, the occurrence of knocking cannot be sufficiently suppressed.

The present invention has been made in view of the circumstances as described above, and an object thereof is to provide a control how your good beauty control system for an engine capable of more reliably suppress the knocking.

In order to solve the above problems, as a result of diligent research, the inventors of the present application may cause knocking when the low temperature oxidation reaction occurs before the combustion of the air-fuel mixture starts, that is, before the high temperature oxidation reaction starts. Was found to be very high.

The low-temperature oxidation reaction is a reaction that involves a slight amount of heat generation that exceeds the cooling loss. When the temperature inside the combustion chamber (cylinder) is high, hydrogen is extracted from the hydrocarbons that make up the fuel by oxygen radicals and the like. It is a reaction to start. The low-temperature oxidation reaction occurs before the high-temperature oxidation reaction, which is a reaction that emits high thermal energy while causing a flame, is started, that is, before so-called combustion is started. Knocking also occurs when the temperature in the combustion chamber is high. Therefore, as described above, when the air-fuel mixture undergoes a low-temperature oxidation reaction, the subsequent knocking is considered to be due to the high temperature in the combustion chamber.

Here, as described above, the low-temperature oxidation reaction occurs before the combustion of the air-fuel mixture starts and at a time sufficiently earlier than the time when knocking occurs. Therefore, if the occurrence of knocking is predicted based on the low temperature oxidation reaction level, which indicates the degree of occurrence of the low temperature oxidation reaction, it is possible to predict the occurrence of knocking at a sufficiently earlier time than the time when knocking occurs. Become.

On the other hand, if the low temperature oxidation reaction level is high, knocking occurs with a very high probability, but knocking may not occur even when the low temperature oxidation reaction level is high, and despite the low low temperature oxidation reaction level. We obtained the finding that knocking may occur. On the other hand, the inventors of the present application have further found that knocking is more likely to occur when the combustion after the start of the high-temperature oxidation reaction is steep.

The present invention has been made based on the above findings, the cylinder air-fuel mixture of fuel and air containing gasoline is burned, and detection means for detecting a cylinder pressure which is a pressure in the cylinder A method of controlling the engine, including heat during the first period, which is part of the specific period , based on the in-cylinder pressure detected by the detection means during the specific period from the late compression stroke to the early expansion stroke. During the first calculation step of calculating the increase amount of the occurrence rate and the second period included in the specific period and set to the retard side from the first period based on the in-cylinder pressure during the specific period. When the second calculation step of calculating the increase amount of the in-cylinder pressure and the first condition that the increase amount of the heat generation rate calculated in the first calculation step is equal to or more than the reference increase amount are satisfied, the cylinder a coolant to reduce the temperature of the inner saw including a knock suppression supplying to said cylinder, said knock suppression step, first to initiate the supply of the refrigerant in response to the first condition is satisfied When the second condition that the increase amount of the in-cylinder pressure calculated in the second calculation step is equal to or more than the reference pressure increase amount is satisfied after the step and the first step, the supply of the refrigerant is defined. continue until the end time, the second step and the including second condition for stopping the supply of the refrigerant before the end timing if not satisfied, the control method for an engine, characterized in that Provide (claim 1).

According to this method, the amount of increase in the heat generation rate during the first period, which indicates the degree of occurrence of the low-temperature oxidation reaction that correlates with the occurrence of knocking and occurs earlier than the timing at which knocking occurs, and from the first period. Since the amount of increase in the in-cylinder pressure during the second period on the retard side is calculated, it is possible to detect at an early stage that knocking is likely to occur based on these calculated values, and knocking. The occurrence can be determined accurately. Then, based on the result, the refrigerant can be effectively supplied into the cylinder, and knocking can be suppressed more reliably.

In particular, when it is determined that the amount of increase in the heat generation rate during the first period is equal to or greater than the reference increase amount, the refrigerant injection is started, and then the amount of increase in the in-cylinder pressure during the second period is determined to be equal to or greater than the reference pressure increase amount. Since the injection of the refrigerant is continued or stopped depending on whether or not the refrigerant is injected, the refrigerant can be more reliably supplied into the cylinder at an appropriate time to prevent the occurrence of knocking, and when knocking does not occur. It is possible to prevent the refrigerant from being supplied into the cylinder and the temperature inside the cylinder from dropping excessively.

In the method, the engine comprises an injector that injects fuel into the cylinder, the injector performing at least a main injection that injects fuel before compression top dead center, and the knock suppression step into the cylinder. The supplied refrigerant is preferably fuel that is additionally injected from the injector after the main injection (claim 2 ).

According to this method, it is not necessary to separately provide a device for supplying the refrigerant to the cylinder.

Further, the present invention is an engine control device including a cylinder in which a mixture of fuel containing gasoline and air is burned, and is a detection means for detecting the in-cylinder pressure which is the pressure in the cylinder, and the cylinder. A refrigerant supply means for supplying a refrigerant for lowering the temperature inside the cylinder and a control means for controlling the refrigerant supply means are provided, and the control means has a specific period from the latter stage of the compression stroke to the early stage of the expansion stroke. Based on the in-cylinder pressure detected by the detection means, the amount of increase in the heat generation rate during the first period, which is a part of the specific period, is calculated, and the amount of increase in the heat generation rate is equal to or greater than the reference increase amount. The first condition is satisfied, the refrigerant supply means is started to supply the refrigerant, and the first condition is included in the specific period and is included in the specific period based on the in-cylinder pressure during the specific period. The amount of increase in the in-cylinder pressure during the second period set on the retard side of the period is calculated, and when the second condition that the amount of increase in the in-cylinder pressure is equal to or greater than the reference pressure increase amount is satisfied, the refrigerant is supplied. Is continued until the predetermined end time , and if the second condition is not satisfied, the refrigerant supply means is controlled so that the supply of the refrigerant is stopped before the end time. A control device for a characteristic engine is provided ( claim 3 ).

According to this device, it is possible to detect at an early stage that knocking is likely to occur, and it is possible to accurately determine the occurrence of knocking. Then, based on the result, the refrigerant can be effectively supplied to the cylinder, and knocking can be suppressed more reliably.

As described above, according to the present invention, knocking can be suppressed more reliably.

It is a figure which showed the structure of the engine system which concerns on one Embodiment of this invention. It is a block diagram which shows the control system of an engine. It is a figure which showed the control map. It is a figure which showed an example of fuel injection timing, ignition timing, and heat generation rate in a high load region. It is the figure which compared and showed the change of the heat generation rate when knocking occurred and when knocking did not occur. It is an enlarged view of FIG. It is the figure which compared and showed the change of the in-cylinder pressure when knocking occurred and when knocking did not occur. It is a flowchart which showed the flow of knock determination and knock avoidance control. It is a figure which showed each change of the crank of each parameter when knock determination and knock avoidance control were performed. It is a figure which showed each change of the crank of each parameter when knock determination and knock avoidance control were performed. It is a figure which showed each change of the crank of each parameter when knock determination and knock avoidance control were performed.

(1) Overall Configuration of Engine FIG. 1 is a diagram showing a configuration of an engine system to which the control device of the engine of the present invention is applied. The engine system of the present embodiment includes a 4-stroke engine main body 1, an intake passage 20 for introducing combustion air into the engine main body 1, and an exhaust passage 30 for discharging the exhaust generated by the engine main body 1. And.

The engine body 1 is, for example, an in-line 4-cylinder engine in which four cylinders 2 are arranged in series in a direction orthogonal to the paper surface of FIG. This engine system is mounted on a vehicle, and the engine body 1 is used as a drive source for the vehicle. In the present embodiment, the engine body 1 is driven by being supplied with fuel including gasoline. The fuel may be gasoline containing bioethanol or the like.

The engine body 1 includes a cylinder block 3 in which a cylinder 2 is formed, a cylinder head 4 provided on the upper surface of the cylinder block 3, and a piston 5 fitted in the cylinder 2 so as to be reciprocating (up and down). Has.

A combustion chamber 6 is formed above the piston 5. The combustion chamber 6 is a so-called pent roof type, and the ceiling surface of the combustion chamber 6 formed by the lower surface of the cylinder head 4 has a triangular roof shape composed of two inclined surfaces, an intake side and an exhaust side. On the crown surface of the piston 5, a cavity is formed in which a region including the central portion thereof is recessed on the opposite side (lower side) of the cylinder head 4. Here, the space between the crown surface of the piston 5 and the ceiling surface of the combustion chamber 6 in the inner space of the cylinder 2 regardless of the position of the piston 5 and the combustion state of the air-fuel mixture is referred to as the combustion chamber 6.

The geometric compression ratio of the engine body 1, that is, the ratio of the volume of the combustion chamber 6 when the piston 5 is at the bottom dead center and the volume of the combustion chamber 6 when the piston 5 is at the top dead center is 15 or more. It is set to 20 or less (for example, about 17).

The cylinder head 4 has an intake port 9 for introducing the air supplied from the intake passage 20 into the cylinder 2 (combustion chamber 6) and an exhaust gas generated in the cylinder 2 to be led out to the exhaust passage 30. An exhaust port 10 is formed. Two intake ports 9 and two exhaust ports 10 are formed for each cylinder 2.

The cylinder head 4 is provided with an intake valve 11 that opens and closes an opening on the cylinder 2 side of each intake port 9, and an exhaust valve 12 that opens and closes an opening on the cylinder 2 side of each exhaust port 10.

The cylinder head 4 is provided with an injector 14 for injecting fuel. The injector 14 is attached so that the tip end portion on which the injection port is formed is located near the center of the ceiling surface of the combustion chamber 6 and faces the center of the combustion chamber 6. The injector 14 has a plurality of nozzles at its tip, and has a cone shape (specifically, a hollow cone shape) centered on the central axis of the cylinder 2 from the vicinity of the center of the ceiling surface of the combustion chamber toward the crown surface of the piston 5. It is configured to inject fuel. The taper angle (spray angle) of the cone is, for example, 90 ° to 100 °. The specific configuration of the injector 14 is not limited to this, and may be a single injector.

The injector 14 injects fuel pumped from a high-pressure pump (not shown) into the combustion chamber 6. The injection pressure of the injector 14 is increased to 30 MPa or more in a high load region where knocking is likely to occur, and fuel is injected from the injector 14 at a high pressure in a high load region. The injection pressure is preferably increased up to about 70 MPa. In this case, the fuel is injected at an injection pressure in the range of 50 MPa to 70 Ma in the high load region of the engine.

The cylinder head 4 is provided with a spark plug 13 for igniting the air-fuel mixture in the combustion chamber 6. At the tip of the spark plug 13, an electrode is formed that discharges sparks to ignite the air-fuel mixture and imparts ignition energy to the air-fuel mixture. The spark plug 13 is arranged so that its tip is located near the center of the ceiling surface of the combustion chamber 6 and faces the center of the combustion chamber 6.

The intake passage 20 is provided with an air cleaner 21 and a throttle valve 22 for opening and closing the intake passage 20 in this order from the upstream side. In the present embodiment, the throttle valve 22 is basically maintained at a fully open position or an opening close to this during engine operation, and is closed and intake air only under limited operating conditions such as when the engine is stopped. Block the passage 20.

The exhaust passage 30 is provided with a purification device 31 for purifying the exhaust gas. The purification device 31 has, for example, a built-in three-way catalyst.

The exhaust passage 30 is provided with an EGR device 40 for returning the exhaust gas passing through the exhaust passage 30, that is, a part of the burnt gas to the intake passage 20 as EGR gas. The EGR device 40 opens and closes the EGR passage 41 and the EGR passage 41 that communicate the portion of the intake passage 20 downstream of the throttle valve 22 and the portion of the exhaust passage 30 upstream of the purification device 31. It has an EGR valve 42. Further, in the present embodiment, the EGR passage 41 is provided with an EGR cooler 43 for cooling the EGR gas passing through the EGR passage 41, and the EGR gas is cooled by the EGR cooler 43 and then returned to the intake passage 20. To.

(2) Control system (2-1) System configuration FIG. 2 is a block diagram showing an engine control system. The engine system of this embodiment is collectively controlled by a PCM (powertrain control module, control means) 100. As is well known, the PCM 100 is a microprocessor composed of a CPU, a ROM, a RAM, and the like.

Various sensors are provided in the vehicle, and the PCM 100 is electrically connected to these sensors. For example, the cylinder block 3 is provided with a crank angle sensor SN1 that detects the engine speed. Further, the intake passage 20 is provided with an air flow sensor SN2 that detects the amount of air taken into each cylinder 2 through the intake passage 20. Further, the cylinder head 4 is provided with an in-cylinder pressure sensor SN3 that detects the pressure in the combustion chamber 6. One in-cylinder pressure sensor SN3 is provided for each cylinder 2. Further, the exhaust passage 30 is provided with an exhaust O2 sensor SN4 for detecting the exhaust oxygen concentration, which is the oxygen concentration of the exhaust gas flowing through the exhaust passage 20. Further, the vehicle is provided with an accelerator opening sensor SN5 that detects an opening degree (accelerator opening degree) of an accelerator pedal (accelerator opening degree) which is not shown and is operated by the driver. In the present embodiment, the in-cylinder pressure sensor SN3 functions as the detection means in the claims.

The PCM 100 executes various calculations based on the input signals from the sensors SN1 to SN5 and the like to control each part of the engine such as the spark plug 13, the injector 14, the throttle valve 22, and the EGR valve 42.

(2-2) Basic Control FIG. 3 is a control map in which the horizontal axis is the engine speed and the vertical axis is the engine load.

In the present embodiment, the low load region B in which the engine load is less than the preset first reference load Tq1 and knocking is unlikely to occur, and the high load region A in which the engine load is equal to or more than the reference load Tq1 and knocking is likely to occur. It is set. In the high load region A, a knock determination described later is performed in order to suppress the occurrence of knocking, and knock avoidance control is appropriately performed according to the result of the knock determination. In the present embodiment, as described above, the geometric compression ratio of the engine body 1 is set to 15 or more, and the temperature in the combustion chamber 6 is raised to a very high temperature. Therefore, knocking is particularly likely to occur.

The high load region A is further divided into a high load low speed region A1 in which the engine speed is less than the preset reference speed N1 and a high load high speed region A2 in which the engine speed is equal to or higher than the reference speed N1. ..

In the present embodiment, in the region where the engine speed is less than the reference speed N1 (region A1 and region B1), compression self-ignition combustion (SPCCI combustion, SPCCI: Spark Control Compression Ignition) by ignition assist is carried out. In compression self-ignition combustion, first, fuel is injected from the injector 14 into the combustion chamber 6 before the compression top dead center (TDC). This fuel mixes with air by near compression top dead center. The air-fuel mixture formed in the combustion chamber 6 is discharged from the spark plug 13 near the compression top dead center. As a result, the air-fuel mixture around the spark plug 13 is forcibly ignited. Then, the flame propagates from around the spark plug 13 to the surroundings, the temperature of the surrounding air-fuel mixture is raised, and self-ignition occurs.

On the other hand, in the region (region A2 and region B2) where the engine speed is equal to or higher than the reference speed N1, it becomes difficult to self-ignite the air-fuel mixture at a desired time. Spark ignition combustion, SI: Spark Ignition) is carried out. SI combustion is a combustion form in which almost the entire air-fuel mixture is burned by flame propagation. Discharge is performed from the spark plug 13 near the compression top dead center, and the air-fuel mixture around the spark plug 13 is forcibly ignited. .. Then, the flame propagates from around the spark plug 13 to the surroundings, and the remaining air-fuel mixture is forcibly burned by the flame propagation.

(2-3) Knock avoidance control (knock suppression step)
Next, knock avoidance control performed in the high load region A will be described with reference to FIG.

In the present embodiment, in order to avoid knocking, control of injecting fuel from the injector 14 to the air-fuel mixture during combustion is implemented as knock avoidance control.

FIG. 4 is a diagram showing an example of fuel injection timing, ignition timing, and heat generation rate in the region (A2) where SI combustion is performed in the high load region A. As shown by the solid line in FIG. 4, for example, in this region, the fuel injection Q1 is performed only once in the latter half of the intake stroke in the normal time when the knock avoidance control is not performed. Then, the air-fuel mixture is ignited by the spark plug 13 in the vicinity of the compression top dead center (at the compression top dead center in the example of FIG. 7). The fuel injection Q1 is the main injection for achieving the required engine torque. That is, the main injection Q1 is performed regardless of the presence or absence of knocking. The injection amount of the main injection Q1 is basically an amount corresponding to the required value of the engine torque.

On the other hand, when the knock avoidance control is executed, as shown by the broken line in FIG. 4, the additional injection Q2 is executed after the combustion of the fuel related to the main injection Q1 is started. As will be described later, this combustion is a high-temperature oxidation reaction, and the additional injection Q2 is carried out after the high-temperature oxidation reaction has started.

When fuel is injected into the combustion air-fuel mixture, the temperature of the air-fuel mixture is lowered and the occurrence of knocking is suppressed. In particular, in the present embodiment, the occurrence of knocking is effectively suppressed by injecting fuel at a high pressure. Specifically, knocking occurs when the air-fuel mixture locally becomes hot in the combustion chamber 6. On the other hand, in the present embodiment, since the fuel is injected at a high pressure in the air-fuel mixture, the air-fuel mixture can be agitated and the local high temperature field can be extinguished.

The amount of the additional injection Q2 is set to be sufficiently smaller than the amount of the main injection Q1. In the present embodiment, the amount of the additional injection Q2 is 10% or less of the total amount of the fuel injected into the combustion chamber 6 in one combustion cycle, that is, the total amount of the injection amount of the main injection Q1 and the injection amount of the additional injection Q2. The amount is set. For example, the amount of additional injection Q2 is set to about 5% of the total amount of fuel.

The additional injection Q2 is preferably performed at a time when about 20% of the total heat generated by the main injection Q1 is generated, and the additional injection is performed at a time excessively retarded from this time. When Q2 is carried out, mixing with air may deteriorate and the amount of smoke generated may increase. Therefore, in the present embodiment, the additional injection Q2 is performed by the preset additional injection end time (end time) . Additional injection end timing is set to a time that is included in the combustion period (period time of the high temperature oxidation reaction Ru is included in the period occurring). For example, the additional injection end time is set in advance according to the engine speed and the engine load, and is stored in the PCM100 as a map. The PCM100 extracts the values corresponding to the engine speed and the engine load from this map. ..

As described above, in the present embodiment, the fuel is used as the refrigerant for cooling the air-fuel mixture, and the injector 14 functions as the refrigerant supply means for supplying the refrigerant to the combustion chamber 6. Further, the step of carrying out the additional injection Q2 is the knock suppression step in the claim.

(2-4) Knock judgment control (prediction process)
Next, the knock determination control performed in the high load region A will be described.

In the present embodiment, the first knock determination step and the second knock determination step are performed, and it is determined whether or not knocking occurs based on the determination results (predicts the occurrence of knocking).

Here, in the present embodiment and the claims, the occurrence of knocking does not mean that knocking occurs strictly, but that the knock strength is higher than the permissible value from the viewpoint of engine reliability. Including that. The knock intensity is the maximum value of the amplitude of the waveform having a predetermined frequency or higher included in the in-cylinder pressure waveform.

(1st knock judgment step)
The inventors of the present application have diligently studied a method for determining whether or not knocking occurs earlier. As a result, it was found that when the low temperature oxidation reaction occurs, knocking is very likely to occur thereafter.

The low-temperature oxidation reaction is a reaction accompanied by a slight heat generation exceeding the cooling loss, and starts when hydrogen is extracted from the hydrocarbons constituting the fuel by oxygen radicals or the like when the temperature in the combustion chamber 6 is high. It is a reaction. The low-temperature oxidation reaction occurs before the high-temperature oxidation reaction, which is a reaction that emits high thermal energy while causing a flame, is started, that is, before combustion is started.

Knocking is a phenomenon that occurs when the air-fuel mixture locally becomes hot in the combustion chamber 6 as described above, and knocking also occurs when the temperature in the combustion chamber 6 is high. Therefore, when a low-temperature oxidation reaction occurs, knocking is very likely to occur after that. The fact that the low-temperature oxidation reaction occurs means that the temperature inside the combustion chamber 6 is high enough to cause the low-temperature oxidation reaction. It is considered that knocking is likely to occur in such a state.

FIG. 5 is a diagram showing a comparison between the heat generation rate (solid line) when the low temperature oxidation reaction occurs and the heat generation rate (broken line) when the low temperature oxidation reaction does not occur. FIG. 6 is an enlarged view of the vicinity of the compression top dead center of FIG.

The heat generation rate shown by the broken line in FIG. 6 is minimized at a predetermined crank angle CA10 before the compression top dead center, then gradually increases, and then rapidly increases with the start of the high-temperature oxidation reaction. .. On the other hand, the heat generation rate shown by the solid line in FIG. 6 becomes the minimum at a predetermined crank angle CA10 like the broken line, but then rises at a speed faster than the broken line, and a low temperature oxidation reaction occurs. It is shown. That is, the low-temperature oxidation reaction is an exothermic reaction as described above, and when the low-temperature oxidation reaction occurs, the heat generation rate is higher than when it does not occur. The amount of increase in the heat generation rate due to the low-temperature oxidation reaction is small, and although the heat generation rate starts to increase at a high rate as described above, the increase stops immediately (the heat generation rate decreases, is substantially constant,). Alternatively, it gradually rises), and then rises sharply with the start of the high-temperature oxidation reaction.

Then, as is clear from the comparison between the broken line and the solid line in FIG. 6, when the low temperature oxidation reaction occurs, the heat generation rate is higher than that when the low temperature oxidation reaction does not occur after the middle stage of combustion (high temperature oxidation reaction). It is rising sharply in, and knocking is occurring.

From the above findings, in the first knock determination step, it is determined whether or not a low temperature oxidation reaction has occurred. Then, when the low-temperature oxidation reaction occurs, it is determined that knocking is likely to occur thereafter.

Specifically, the PCM 100 calculates the heat generation rate of the pre-ignition first crank angle CA10, which is the crank angle at which the heat generation rate is minimized, as described above, and is more predetermined than the pre-ignition first crank angle. The heat generation rate of the second crank angle CA20 before ignition after the angle is calculated. The pre-ignition second crank angle CA20 is a crank angle during a period in which the heat generation rate increases with the low-temperature oxidation reaction, and both the pre-ignition first crank angle CA10 and the pre-ignition second crank angle CA20 are compression strokes. It is a crank angle included in a specific period from the late stage to the early stage of the expansion stroke and within the first period before the combustion of the air-fuel mixture starts. Then, the PCM 100 calculates the amount of increase in the pre-ignition heat generation rate, which is the amount of increase in the heat generation rate of the pre-ignition second crank angle CA20 with respect to the heat generation rate of the pre-ignition first crank angle CA10.

In the present embodiment, the amount of increase in the pre-ignition heat generation rate is used as the low temperature oxidation reaction level indicating the degree of occurrence of the low temperature oxidation reaction in the claim, and the above-mentioned step of calculating the amount of increase in the pre-ignition heat generation rate is performed. This is the first calculation process.

In the present specification and claims, the latter stage of the compression stroke means the period from 60 ° CA before the compression top dead center to the compression top dead center, and the initial stage of the expansion stroke means the period from the compression top dead center to the compression top dead center. The period up to 60 ° CA.

The PCM100 determines that a low-temperature oxidation reaction has occurred when the increase in the pre-ignition heat generation rate is equal to or greater than the reference increase amount, and determines that the low-temperature oxidation reaction has not occurred when the increase is less than the reference increase amount.

In the present embodiment, the pre-ignition first crank angle CA10 and the pre-ignition second crank angle CA20 are preset and stored in the PCM 100. For example, the first crank angle CA10 before ignition is set to about 10 ° CA before compression top dead center, and the second crank angle CA20 before ignition is set to about 5 ° CA before compression top dead center. Further, the reference increase amount is also preset and stored in the PCM 100. For example, the reference increase amount is set to about 10 J / ° CA.

Here, the low-temperature oxidation reaction occurs before the combustion of the air-fuel mixture starts (before the high-temperature oxidation reaction starts) and sufficiently earlier than the time when knocking occurs. Therefore, if it is possible to determine whether or not knocking occurs based on whether or not the low-temperature oxidation reaction has occurred, this determination can be performed at a sufficiently earlier time than the time when knocking occurs.

(Second knock judgment step)
As described above, knocking occurs with a very high probability if a low-temperature oxidation reaction occurs. However, in the process of research, the inventors of the present application knock when the EGR ratio, which is the ratio of the amount of burned gas to the total amount of gas in the combustion chamber, is high, even though the low-temperature oxidation reaction does not occur. I got the finding that there are cases. This is because when the EGR rate is high, even if the temperature in the combustion chamber is high enough to cause knocking, the burnt gas inhibits the contact between oxygen radicals and hydrocarbons, so that the low-temperature oxidation reaction is not started. Conceivable. Further, it was found that knocking may not occur depending on the variation in the air-fuel ratio in the combustion chamber, the flow, etc., even though the low-temperature oxidation reaction has occurred.

From this, in the present embodiment, the PCM 100 performs the second knock determination step as described above, and determines that knocking may occur when the low temperature oxidation reaction occurs. However, it is not determined that knocking occurs only by this determination, and the second knock determination step described below is performed to make a final determination as to whether or not knocking occurs based on the determination result of this determination step. ..

FIG. 7 is a diagram showing a change in the in-cylinder pressure with respect to the crank angle. The solid line in FIG. 7 is the in-cylinder pressure when knocking occurs, and the broken line is the in-cylinder pressure when knocking does not occur. As shown in this figure, the in-cylinder pressure increases after the crank angle CA1 at which combustion starts. Then, when knocking occurs, the in-cylinder pressure rises at a faster speed than when knocking does not occur after the crank angle CA1.

As described above, when the rate of increase in the in-cylinder pressure after the start of combustion, that is, the amount of increase is high, knocking is likely to occur. When the amount of increase in the in-cylinder pressure is equal to or greater than a predetermined value, knocking almost certainly occurs. From this, in the second knock determination step, it is determined that knocking occurs when the amount of increase in the in-cylinder pressure after the start of combustion is equal to or greater than a predetermined value.

Specifically, the amount of increase in the in-cylinder pressure during the second period after the start of combustion, which is included in the specific period from the latter stage of the compression stroke to the beginning of the expansion stroke, that is, the in-cylinder pressure immediately after the start of combustion. It is determined that knocking occurs when the rising speed is equal to or higher than the preset reference pressure rising amount.

In the present embodiment, the PCM 100 reads the in-cylinder pressure at the first crank angle after the start of combustion, which is included in a specific period from the late compression stroke to the early expansion stroke. Further, the PCM 100 reads the in-cylinder pressure of the second crank angle, which is the second crank angle after the start of combustion and is on the retard side of the first crank angle, during a specific period. Then, the PCM 100 calculates the amount of increase in the in-cylinder pressure at the second crank angle with respect to the in-cylinder pressure at the first crank angle at the second crank angle.

Further, the PCM 100 is included in a specific period from the latter stage of the compression stroke to the first stage of the expansion stroke, and is the third crank angle after the start of combustion, which is the third crank angle on the retard side of the first crank angle. Read the in-cylinder pressure of. Further, the PCM 100 is included in a specific period including the latter stage of the compression stroke and the initial stage of the expansion stroke, and is the fourth crank angle after the start of combustion, which is the fourth crank angle on the retard side of the third crank angle. Read the in-cylinder pressure at. Then, the PCM 100 calculates the amount of increase in the in-cylinder pressure at the fourth crank angle with respect to the in-cylinder pressure at the third crank angle at the fourth crank angle.

In the PCM100, the amount of increase in the in-cylinder pressure at the second crank angle with respect to the in-cylinder pressure at the first crank angle (hereinafter, appropriately referred to as the amount of increase in the first cylinder pressure) is equal to or greater than the reference pressure increase amount, and the third crank It is determined that knocking occurs when the amount of increase in the in-cylinder pressure at the fourth crank angle with respect to the in-cylinder pressure at the angle (hereinafter, appropriately referred to as the amount of increase in the second cylinder pressure) is equal to or greater than the reference pressure increase amount. On the other hand, the amount of increase in the in-cylinder pressure at the second crank angle with respect to the in-cylinder pressure at the first crank angle is less than the reference pressure increase amount, or the increase in the in-cylinder pressure at the fourth crank angle with respect to the in-cylinder pressure at the third crank angle. When the amount is less than the reference pressure increase amount, it is determined that knocking does not occur.

The first to fourth crank angles are all angles on the retard side of the pre-ignition first crank angle CA10 and the pre-ignition second crank angle CA20.

The reference pressure increase amount is the maximum value of the in-cylinder pressure increase amount when knocking does not occur, and is preset and stored in the PCM 100. For example, the reference pressure increase amount is set and stored in a map according to the engine speed and the engine load, and the PCM100 has the reference pressure increase amount corresponding to the current engine speed and the engine load from this map. Is extracted and compared with the amount of increase in the in-cylinder pressure. In the present embodiment, the reference pressure increase amount to be compared with the first cylinder internal pressure increase amount and the reference pressure increase amount to be compared with the second cylinder internal pressure increase amount are set to the same value, but they are different. You may be.

The first crank angle to the fourth crank angle are preset and stored in the PCM 100. That is, the time when combustion starts is determined to some extent for each engine speed, engine load, and the like. Therefore, in the present embodiment, the time when combustion starts is investigated by an experiment or the like, and the first crank angle is set to an angle included in a specific period from the late compression stroke to the early stage of the expansion stroke and after the start of combustion. The fourth crank angle is set in advance and stored in the PCM 100. In the present embodiment, the first to fourth crank angles are set for the engine speed and the engine load and stored in the PCM 100 as a map. For example, the first crank angle is TDC (compression top dead center), the second crank angle and the third crank angle are about ATDC 5 ° CA (compression top dead center 5 ° CA), and the fourth crank angle is ATDC 10 ° CA (compression). It is set to about 10 ° CA) after top dead center.

In the present embodiment, the amount of increase in the pressure inside the first cylinder and the amount of increase in the pressure inside the second cylinder are used as the combustion steepness representing the steepness of combustion after the start of the high-temperature oxidation reaction in the claims, and this is calculated. The above step is the second calculation step.

(2-5) Flow of knock determination control and knock avoidance control As described above, whether or not knocking occurs can be accurately determined based on the amount of increase in the in-cylinder pressure after the start of combustion. However, in the method of determining whether or not knocking occurs based on the amount of increase in the in-cylinder pressure, that is, in the second knock determination step, it is determined whether or not knocking occurs, and combustion starts. After doing. Therefore, even if the additional injection Q2 is attempted after it is determined that knocking occurs in the second knock determination step, the additional injection Q2 can actually be performed due to the drive delay of the injector 14 when the engine speed is high or the like. (The fuel actually starts to be injected from the injector 14 into the combustion chamber 6) may be later than the optimum additional injection time, which is the time when knocking can be suppressed most effectively.

Therefore, in the present embodiment, when it is determined by the first knock determination step that knocking may start, the additional injection Q2 is started (first step). That is, it is added according to the first condition that the increase in the heat generation rate before ignition is equal to or higher than the reference increase amount (according to the first condition that the low temperature oxidation reaction level is equal to or higher than the reference level). The first step of starting the injection Q2 (starting the supply of fuel as a refrigerant) is carried out.

Then, when it is determined by the second knock determination step that knocking does not occur, the additional injection Q2 is stopped (second step). That is, when the second condition that both the first cylinder pressure increase amount and the second cylinder pressure increase amount are equal to or more than the reference pressure increase amount is not satisfied (the second condition that the combustion steepness is equal to or more than the reference value). (If the condition of) is not satisfied, the second step of stopping the additional injection Q2 (stopping the supply of fuel as a refrigerant) is carried out.

On the other hand, if it is determined by the second knock determination step that knocking occurs, the additional injection Q2 is continued even after this determination (second step). That is, when the second condition that both the first cylinder pressure increase amount and the second cylinder pressure increase amount are equal to or more than the reference pressure increase amount is satisfied (the second condition that the combustion steepness is equal to or more than the reference value). (If is satisfied), the additional injection Q2 is continued (the supply of fuel as a refrigerant is continued).

The control flow will be described with reference to the flowchart of FIG.

First, the PCM 100 reads various engine information in step S1. For example, the PCM100 has an in-cylinder pressure detected by the in-cylinder pressure sensor SN3, an accelerator opening degree detected by the accelerator opening sensor SN5, an engine rotation speed detected by the crank angle sensor SN1, and an exhaust detected by the exhaust O2 sensor SN4. The oxygen concentration, the intake amount detected by the air flow sensor SN2, the opening degree of the EGR valve 42, and the like are read.

After step S1, the process proceeds to step S2. In step S2, the PCM 100 determines whether or not the engine is operating in the high load region A, that is, whether or not the engine load is equal to or greater than the reference load Tq1. The engine load is calculated based on the accelerator opening and the engine speed.

When the determination in step S2 is NO and the engine is operating in the low load region B, the PCM 100 ends the process as it is (returns to step S1). On the other hand, when the determination in step S2 is YES and the engine is operating in the high load region A, the PCM 100 proceeds to step S3.

In step S3, the PCM 100 calculates the heat generation rate dQ using the in-cylinder pressure. As a method for calculating the heat generation rate dQ, a conventionally used method can be adopted, and the description here will be omitted.

After step S3, the process proceeds to step S4. In step S4, the PCM 100 determines whether or not a low temperature oxidation reaction has occurred.

As described above, the PCM 100 calculates the amount of increase in the pre-ignition heat generation rate, which is the amount of increase in the heat generation rate of the pre-ignition second crank angle CA20 with respect to the heat generation rate of the pre-ignition first crank angle CA10. Then, the PCM100 determines that the low temperature oxidation reaction has occurred when the increase in the pre-ignition heat generation rate is equal to or greater than the reference increase amount, and does not occur when the increase in the pre-ignition heat generation rate is less than the reference increase amount. Judged as

If the determination in step S4 is YES and the PCM100 determines that the low temperature oxidation reaction has occurred, the PCM 100 proceeds to step S5. In step S5, the PCM 100 determines that knocking may occur.

After step S5, the PCM 100 proceeds to step S6 and starts driving the injector 14. Here, the injector 14 has a drive delay. Therefore, even if a command to start driving is issued to the injector 14, fuel is not immediately injected from the injector 14, and fuel is injected only after a predetermined time.

After step S6, the process proceeds to step S7. In step S7, the PCM 100 calculates the amount of increase in the first cylinder pressure and the amount of increase in the second cylinder pressure, the amount of increase in the first cylinder pressure is equal to or greater than the reference pressure increase amount, and the amount of increase in the second cylinder pressure is described above. It is determined whether or not the amount is equal to or greater than the reference pressure increase amount.

If the determination in step S7 is YES and the amount of increase in the first cylinder internal pressure is equal to or greater than the reference pressure increase amount and the amount of increase in the second cylinder internal pressure is equal to or greater than the reference pressure increase amount, the PCM 100 proceeds to step S8 and knocks. Is determined to occur, and the injector 14 is continued to be driven. After step S8, the PCM 100 proceeds to step S9.

In step S9, the PCM 100 determines whether or not the crank angle has reached the end time of the additional injection, waits for this determination to be YES, and proceeds to step S10. In step S10, the PCM 100 stops driving the injector 14.

On the other hand, when the determination in step S7 is NO and the amount of increase in the first cylinder pressure is less than the reference pressure increase amount or the amount of increase in the second cylinder pressure is less than the reference pressure increase amount, the PCM 100 proceeds to step S11. , Judge that knocking does not occur. Then, the process proceeds to step S10, and the PCM 100 stops driving the injector 14.

Returning to step S4, when the determination in step S4 is NO and it is determined that the low temperature oxidation reaction has not occurred, the PCM 100 proceeds to step S12. In step S12, similarly to step S7, the PCM 100 determines whether or not the amount of increase in the first cylinder internal pressure is equal to or greater than the reference pressure increase amount and the amount of increase in the second cylinder internal pressure is equal to or greater than the reference pressure increase amount.

If the determination in step S12 is YES and the amount of increase in the first cylinder internal pressure is equal to or greater than the reference pressure increase amount and the amount of increase in the second cylinder internal pressure is equal to or greater than the reference pressure increase amount, the PCM 100 proceeds to step S13 and knocking occurs. Judge that it will occur. Then, the PCM 100 proceeds to step S14 and starts driving the injector 14. The driving of the injector 14 is started immediately after the determination in step S13 becomes YES. However, as described above, the fuel is not injected from the injector 14 immediately after the drive is started, and the fuel is injected only after a predetermined time.

After step S14, the process proceeds to step S15. In step S15, similarly to step S9, the PCM 100 determines whether or not the crank angle has reached the end time of the additional injection, waits for this determination to be YES, and proceeds to step S16. In step S16, the PCM 100 stops driving the injector 14.

On the other hand, when the determination in step S12 is NO and the amount of increase in the first cylinder pressure is less than the reference pressure increase amount or the amount of increase in the second cylinder pressure is less than the reference pressure increase amount, the PCM 100 proceeds to step S17. , It is determined that knocking does not occur, and the process ends (returns to step S1).

9 to 11 show changes in the crank angles of the heat generation rate, the low temperature oxidation reaction flag, the knock generation flag, the drive signal of the injector 14, and the valve opening opening degree of the injector 14 when the above control is performed. It is a graph. The low temperature oxidation flag is a flag that becomes 1 when it is determined that the low temperature oxidation reaction has occurred in step S4, and becomes 0 at other times. The knock generation flag determines in step S7 or step S12 that knocking occurs when the amount of increase in the first cylinder internal pressure is equal to or greater than the reference pressure increase amount and the amount of increase in the second cylinder internal pressure is equal to or greater than the reference pressure increase amount. It is a flag that becomes 1 when it is done, and becomes 0 in other cases. The drive signal of the injector 14 is a signal sent from the PCM 100 to the injector 14, and here, when a command is issued from the PCM 100 to the injector 14 to start driving the injector 14, it becomes 1, and when this command is stopped, it becomes 1. It is represented as a signal that becomes 0.

In FIG. 9, the determinations in steps S4 and S7 are both YES, and it is determined that a low temperature oxidation reaction has occurred and knocking is likely to occur, and the amount of increase in the pressure inside the first cylinder and the amount of increase in the pressure in the first cylinder are high. It is a figure in the case where it is determined that all of the 2nd cylinder pressure increase amounts are equal to or more than the reference pressure increase amount, and knocking is determined to occur. In this case, when it is determined that the low temperature oxidation reaction has occurred at the crank angle t1 and the low temperature oxidation reaction flag changes from 0 to 1, the injector 14 is started to be driven immediately after that. Along with this, the valve opening opening of the injector 14 increases after the crank angle t1, and at the crank angle t2, the valve opening opening of the injector 14 reaches full opening, and the fuel related to the additional injection Q2 is released from the injector 14. Be jetted. Then, even after it is determined that knocking occurs at the crank angle t3 and the knock flag changes from 0 to 1, the injector 14 continues to be driven. Then, at time t4, when the end time of the additional injection is reached, the driving of the injector 14 is stopped. Even when the drive of the injector 14 is stopped due to the drive delay of the injector 14, the valve opening opening degree does not immediately close fully and gradually decreases.

As described above, when the low temperature oxidation reaction occurs, and further, when the amount of increase in the pressure in the first cylinder and the amount of increase in the pressure in the second cylinder are equal to or more than the reference pressure increase amount, the PCM100 is determined to have caused the low temperature oxidation reaction. The operation of the injector 14 is continued for a period from immediately after that to the end time of the additional injection. As a result, from the injector 14, the additional injection Q2 is performed during the period from the predetermined time during this period to the end time of the additional injection, and the additional fuel is injected into the combustion chamber 6.

On the other hand, in FIG. 10, the determination in step S4 is YES and it is determined that the low temperature oxidation reaction has occurred, while the determination in step S7 is NO and the amount of increase in the first cylinder pressure or the amount of increase in the second cylinder pressure. Is a figure when it is determined that knocking does not occur because the amount of increase in the reference pressure is less than the reference pressure. Also in this case, if it is determined that the low temperature oxidation reaction has occurred at the crank angle t11, the injector 14 is started to be driven immediately after that. Along with this, the valve opening opening degree of the injector 14 increases after the crank angle t11. However, in this case, if it is determined that knocking does not occur at the crank angle t12, the drive of the injector 14 is stopped (a drive stop signal is output from the PCM 100 to the injector 14). Along with this, the valve opening opening degree of the injector 14 gradually decreases after the crank angle t12.

In this way, while the low temperature oxidation reaction occurs, when the amount of increase in the pressure inside the first cylinder or the amount of increase in the pressure inside the second cylinder is less than the reference pressure increase, the injector 14 is driven when it is determined that the low temperature oxidation reaction occurs. Although it is started, the drive of the injector 14 is stopped as soon as it is determined that the amount of increase in the pressure inside the first cylinder or the amount of increase in the pressure inside the second cylinder is less than the reference pressure increase amount.

Further, in FIG. 11, the determination in step S4 is NO and it is determined that the low temperature oxidation reaction does not occur, while the determination in step S7 is YES and the amount of increase in the pressure inside the first cylinder and the increase in the pressure inside the second cylinder are increased. It is a figure when it is judged that knocking occurs when the amount becomes equal to or more than a reference pressure rise amount. In this case, the injector 14 is driven at the crank angle t21 where it is determined that the amount of increase in the pressure inside the first cylinder and the amount of increase in the pressure inside the second cylinder are equal to or greater than the reference pressure increase amount. Then, when the end time of the additional injection is reached at the crank angle t22, the driving of the injector 14 is stopped.

In this way, when the low temperature oxidation reaction does not occur, but the amount of increase in the first cylinder pressure and the amount of increase in the second cylinder pressure are equal to or greater than the reference pressure increase amount, the amount of increase in the first cylinder pressure and the amount of increase in the second cylinder pressure are the reference. Immediately after it is determined that the pressure rise amount or more, the injector 14 is driven.

(3) Action, etc. As described above, according to the present embodiment, knocking is first performed depending on whether or not a low-temperature oxidation reaction has occurred (whether or not the amount of increase in the heat generation rate before ignition is equal to or greater than the standard increase amount). The possibility of occurrence is determined, and then the determination of whether or not knocking occurs is determined depending on whether or not the amount of increase in the first cylinder pressure and the amount of increase in the second cylinder pressure is equal to or greater than the reference pressure increase amount. .. Therefore, it is possible to detect at an early stage that knocking is likely to occur, and it is possible to accurately predict the occurrence of knocking.

Further, when the low temperature oxidation reaction occurs, the additional injection Q2 is started (the operation of the injector 14 is started). Therefore, the fuel related to the additional injection Q2 can be more reliably injected into the combustion chamber 6 at an appropriate time, and the occurrence of knocking can be reliably prevented.

Then, when it is determined that the amount of increase in the first cylinder pressure and the amount of increase in the second cylinder pressure are equal to or greater than the reference pressure increase amount, the additional injection Q2 is continued, while the amount of increase in the first cylinder pressure and the amount of increase in the second cylinder pressure increase. When it is determined that the amount is less than the reference pressure increase amount, the additional injection Q2 is stopped. Therefore, if it is predicted that the amount of increase in the pressure inside the first cylinder and the amount of increase in the pressure inside the second cylinder are less than the reference pressure increase and knocking does not occur, the additional injection Q2 is continued and a large amount of fuel is injected into the cylinder. This, and it is possible to prevent the combustion temperature from dropping accordingly.

(4) Deformation Example In the above embodiment, in the second knock determination step, the amount of increase in the in-cylinder pressure included in the specific period from the late compression stroke to the early stage of the expansion stroke and after the start of combustion is the reference pressure increase amount. The case where it is determined that knocking occurs in the above cases has been described. When the amount of increase in the in-cylinder pressure is high, the amount of increase in the heat generation rate is also high. That is, the inventors of the present application have found that knocking is likely to occur even when the amount of increase in the heat generation rate is high after the combustion is started and is included in a specific period from the late compression stroke to the early expansion stroke. Got

Therefore, the parameter used for the judgment in the second knock determination step (the parameter used as the combustion steepness indicating the steepness of combustion after the start of the high-temperature oxidation reaction) is used as the amount of increase in the heat generation rate instead of the amount of increase in the in-cylinder pressure. May be good. That is, in the second knock determination step, when it is included in a specific period from the late compression stroke to the early stage of the expansion stroke and the amount of increase in the heat generation rate after the start of combustion is equal to or greater than a preset reference value. It may be determined that knocking occurs, and when the amount of increase in the heat generation rate is less than the reference value, it may be determined that knocking does not occur.

Specifically, it is included in a specific period from the latter stage of the compression stroke to the initial stage of the expansion stroke, and is set to the first crank angle for determining the heat generation rate, which is preset as the time after the start of combustion, and on the retard side. The heat generation rate at the set second crank angle for determining the heat generation rate is calculated. Further, the amount of increase in the heat generation rate of the second crank angle for determining the heat generation rate with respect to the heat generation rate of the first crank angle for determining the heat generation rate is calculated as the amount of increase in the heat generation rate. Then, it is determined whether or not knocking occurs by comparing the amount of increase in the heat generation rate with the reference value. The heat generation rate determination first crank angle is set to, for example, TDC, and the heat generation rate determination second crank angle is set to about ATDC 10 ° CA (10 ° CA after compression top dead center).

With this method and configuration, it is possible to accurately determine whether or not knocking occurs. Further, based on this determination result, the occurrence of knocking can be more reliably prevented, and the amount of the refrigerant supplied to the combustion chamber 6 in order to suppress the occurrence of knocking can be prevented from becoming excessive.

Further, in the above-described embodiment, the case where it is determined that knocking occurs when both the first cylinder internal pressure increase amount and the second cylinder internal pressure increase amount are equal to or more than the reference pressure increase amount in the second knock determination step has been described. .. Instead of this, it may be determined that knocking occurs when at least one of the first cylinder internal pressure increase amount and the second cylinder internal pressure increase amount is equal to or more than the reference pressure increase amount.

Further, in the above embodiment, when the amount of increase in the first cylinder pressure and the amount of increase in the second cylinder pressure are calculated and it is determined whether or not knocking occurs based on the amount of increase in the cylinder pressure during the two periods. As described above, instead of this, only the amount of increase in the in-cylinder pressure during one period may be calculated, and based on this, it may be determined whether or not knocking occurs.

Further, in the above-described embodiment, the case of determining whether or not the low temperature oxidation reaction has occurred based on the heat generation rate has been described in the first knock determination step, but the second knock determination step includes the latter stage of the compression stroke and the initial stage of the expansion stroke. It may be configured to determine whether or not a low temperature oxidation reaction has occurred based on the pressure in the combustion chamber for a specific period including. That is, the determination as to whether or not the low temperature oxidation reaction has occurred does not have to be performed based on the heat generation rate, but may be performed based on the in-cylinder pressure. That is, the parameter used as the low temperature oxidation reaction level indicating the degree of occurrence of the low temperature oxidation reaction is not limited to the heat generation rate (the amount of increase in the heat generation rate), but may be, for example, the amount of increase in the in-cylinder pressure.

In the above embodiment, as knock avoidance control, a case where additional injection for injecting fuel into the combustion chamber 6 is performed after main injection Q1 has been described, but the specific configuration of knock avoidance control is not limited to this. For example, instead of the fuel, another refrigerant capable of reducing the temperature of the air-fuel mixture may be supplied into the combustion chamber 6. Examples of this refrigerant include water and a part of exhaust gas. However, if the fuel is injected, the knock avoidance control can be performed by using the injector 14, so that it is not necessary to separately provide a device for injecting another refrigerant, and the structure can be simplified.

Further, in the above embodiment, when the injection amount of the additional injection Q2 (the amount of fuel supplied to the combustion chamber 6 by the additional injection) is 10% or less of the total amount of fuel supplied to the combustion chamber 6 in one cycle. However, the injection amount of the additional injection Q2 may be larger than 10%.

However, if the injection amount of the additional injection Q2 is increased, the temperature in the combustion chamber 6 may be significantly lowered due to the vaporization of the fuel. In addition, the mixture of fuel and air is insufficient and smoke is likely to occur. Therefore, the amount of fuel supplied to the combustion chamber 6 by the additional injection is preferably set as described above.

Further, the geometric compression ratio of the cylinder is not limited to 15 or more and 20 or less. However, when the geometric compression ratio of the cylinder is 15 or more, knocking is likely to occur. Therefore, it is effective to apply the above embodiment to this engine.

1 Engine body 2 Cylinder 6 Combustion chamber 13 Spark plug 14 Injector (refrigerant supply means)
100 PCM (control means)
SN3 In-cylinder pressure sensor (detection means)

Claims (3)

A cylinder in which mixing of fuel and air containing gasoline is burned, a method for controlling an engine comprising detecting means for detecting a cylinder pressure which is a pressure within the cylinder,
First, the amount of increase in the heat generation rate during the first period, which is a part of the specific period, is calculated based on the in-cylinder pressure detected by the detection means during the specific period from the latter stage of the compression stroke to the early stage of the expansion stroke. Calculation process and
Based on the in-cylinder pressure during the specific period, the second calculation step of calculating the amount of increase in the in-cylinder pressure during the second period included in the specific period and set to the retard side with respect to the first period. ,
When the first condition that the increase amount of the heat generation rate calculated in the first calculation step is equal to or more than the reference increase amount is satisfied , the refrigerant for lowering the temperature in the cylinder is supplied to the cylinder. look including a knock suppression process,
The knock suppression step is
The first step of starting the supply of the refrigerant when the first condition is satisfied, and
After the execution of the first step, when the second condition that the increase amount of the in-cylinder pressure calculated in the second calculation step is equal to or more than the reference pressure increase amount is satisfied, the supply of the refrigerant is supplied until the predetermined end time. continuously, the second step and the including second condition for stopping the supply of the refrigerant before the end timing if not satisfied, the control method for an engine, characterized in that. In the engine control method according to claim 1,
The engine comprises an injector that injects fuel into the cylinder.
The injector performs at least a main injection that injects fuel prior to compression top dead center.
A method for controlling an engine, wherein the refrigerant supplied to the cylinder by the knock suppression step is fuel additionally injected from the injector after the main injection. An engine control device equipped with a cylinder in which a mixture of gasoline-containing fuel and air burns.
A detection means for detecting the in-cylinder pressure, which is the pressure in the cylinder, and
A refrigerant supply means for supplying a refrigerant for lowering the temperature in the cylinder into the cylinder,
A control means for controlling the refrigerant supply means is provided.
The control means
Based on the in-cylinder pressure detected by the detection means during the specific period from the late compression stroke to the early expansion stroke, the amount of increase in the heat generation rate during the first period, which is a part of the specific period, is calculated. When the first condition that the amount of increase in the heat generation rate is equal to or greater than the reference increase amount is satisfied, the refrigerant supply means is started to supply the refrigerant, and the refrigerant is supplied.
Based on the in-cylinder pressure during the specific period, the amount of increase in the in-cylinder pressure during the second period included in the specific period and set to the retard side with respect to the first period is calculated, and the in- cylinder pressure of the in-cylinder pressure is calculated. When the second condition that the amount of increase is equal to or greater than the reference pressure increase amount is satisfied, the supply of the refrigerant is continued until the predetermined end time, and when the second condition is not satisfied, it is before the end time. wherein as the supply of coolant is stopped, controls the coolant supply means, the control apparatus for an engine, characterized in that.

Images