Preignition determination method and preignition determination device

Abstract

This preignition determination method for an internal combustion engine comprises: an in-cylinder pressure information acquisition step for acquiring at least a first pressure which is the pressure before reaching a compression top dead center in a determination target combustion cycle of a determination target cylinder to be determined for the presence or absence of a preignition, a second pressure which is the pressure after reaching the compression top dead center in the determination target combustion cycle of the target cylinder, and a pressure ratio which is the ratio of the second pressure to the first pressure; and a preignition detection step for determining that preignition has taken place in the target cylinder when both a pressure ratio determination condition, where the pressure ratio acquired in the in-cylinder pressure information acquisition step is lower by at least a prescribed amount as compared with pressure ratio standard data corresponding to the pressure ratio, and a first pressure determination condition, where the first pressure acquired in the in-cylinder pressure information acquisition step is higher by at least a prescribed amount as compared with first pressure standard data corresponding to the first pressure, are satisfied.

Description

Pre-ignition determination method and pre-ignition determination device

[0001] The present disclosure relates to a method and apparatus for determining whether pre-ignition occurs in an internal combustion engine. This application claims priority to Japanese Patent Application No. 2024-024082, filed on February 20, 2024, with the Japan Patent Office, the contents of which are incorporated herein by reference.

[0002] Patent Document 1 discloses that when the ratio of the pressure in the cylinder near the compression top dead center (compression pressure) to the reference pressure during the compression stroke exceeds a certain value, and when the rate of pressure increase exceeds a threshold value, it is determined that pre-ignition has occurred.

[0003] Patent No. 4119796

[0004] When the fuel used in an internal combustion engine is relatively highly combustible, early pre-ignition (early in the compression stroke) may occur. In the case of early pre-ignition, combustion is completed before the pressure detection point described in Patent Document 1, and the pressure ratio becomes the same as when a misfire occurs, which creates the problem of being unable to distinguish between pre-ignition and misfire.

[0005] In view of the above circumstances, at least one embodiment of the present disclosure aims to provide a pre-ignition determination method and a pre-ignition determination device that can accurately determine whether pre-ignition occurs in an internal combustion engine.

[0006] A pre-ignition determination method according to at least one embodiment of the present disclosure is a method for determining whether or not pre-ignition has occurred in an internal combustion engine, the method comprising: an internal-cylinder pressure information acquisition step of acquiring at least a first pressure, which is a pressure before top dead center of compression stroke in a combustion cycle of a target cylinder to be determined as to whether or not pre-ignition has occurred in the internal combustion engine; a second pressure, which is a pressure after top dead center of compression stroke in a combustion cycle of the target cylinder to be determined as to whether or not pre-ignition has occurred in the internal combustion engine; and a pressure ratio, which is a ratio of the second pressure to the first pressure; and an internal-cylinder pressure detection step of determining that the target cylinder has pre-ignited if both of the following conditions are satisfied: a pressure ratio determination condition that the pressure ratio acquired in the internal-cylinder pressure information acquisition step is smaller than standard pressure ratio data corresponding to the pressure ratio by a predetermined amount or more; and a first pressure determination condition that the first pressure acquired in the internal-cylinder pressure information acquisition step is larger than standard first pressure data corresponding to the first pressure by a predetermined amount or more.

[0007] According to at least one embodiment of the present disclosure, there is provided a pre-ignition determination device for an internal combustion engine configured to determine whether or not pre-ignition has occurred in the internal combustion engine, and the device includes: an internal-cylinder pressure information acquisition unit configured to acquire at least a first pressure, which is the pressure before top dead center of compression stroke in a combustion cycle of a target cylinder that is to be determined as to whether or not pre-ignition has occurred in the internal combustion engine; a second pressure, which is the pressure after top dead center of compression stroke in a combustion cycle of the target cylinder that is to be determined as to whether or not pre-ignition has occurred in the internal combustion engine; and a pressure ratio, which is the ratio of the second pressure to the first pressure; and an internal-cylinder pressure information acquisition unit configured to determine whether or not pre-ignition has occurred in the target cylinder when both a pressure ratio determination condition that the pressure ratio acquired by the internal-cylinder pressure information acquisition unit is smaller than standard pressure ratio data corresponding to the pressure ratio by a predetermined amount or more and a first pressure determination condition that the first pressure acquired by the internal-cylinder pressure information acquisition unit is larger than standard first pressure data corresponding to the first pressure by a predetermined amount or more are satisfied.

[0008] According to at least one embodiment of the present disclosure, a pre-ignition determination method and a pre-ignition determination device are provided that can accurately determine whether or not pre-ignition occurs in an internal combustion engine.

[0009] 1 is a schematic configuration diagram illustrating an example of a configuration of an internal combustion engine system including a pre-ignition determination device according to an embodiment of the present disclosure; FIG. 1 is a schematic configuration diagram illustrating an example of a configuration of an internal combustion engine according to an embodiment of the present disclosure; FIG. 2 is an explanatory diagram illustrating a combustion cycle of an internal combustion engine according to an embodiment of the present disclosure; FIG. 3 is an explanatory diagram illustrating a measurement timing of an in-cylinder pressure used to determine whether or not early pre-ignition occurs according to an embodiment of the present disclosure; FIG. 4 is an explanatory diagram illustrating a change in in-cylinder pressure relative to a combustion state in a cylinder; FIG. 5 is an explanatory diagram illustrating a detection logic for early pre-ignition; FIG. 6 is an explanatory diagram illustrating an example of a detection flow for early pre-ignition according to an embodiment of the present disclosure; FIG. 7 is an explanatory diagram illustrating an example of a detection flow for early pre-ignition according to an embodiment of the present disclosure;

[0010] Hereinafter, several embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of components described as embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present disclosure.

[0011] (Internal Combustion Engine System) Fig. 1 is a schematic diagram illustrating an example of the configuration of an internal combustion engine system 1 including a pre-ignition determination device 3 according to an embodiment of the present disclosure. As shown in Fig. 1, the internal combustion engine system 1 includes an internal combustion engine (engine) 2 and a pre-ignition determination device 3 configured to determine whether or not pre-ignition (early pre-ignition) occurs in the internal combustion engine 2. As shown in Fig. 1, the internal combustion engine 2 includes at least one cylinder 4 (in the illustrated example, multiple cylinders 4). The internal combustion engine 2 is configured to generate power by combusting fuel inside the multiple cylinders 4. If the fuel is a fuel with relatively high combustibility, for example, a fuel gas containing hydrogen, early pre-ignition may occur.

[0012] The internal combustion engine 2 includes a power transmission shaft 21 for transmitting power generated by the internal combustion engine 2 to other devices. As shown in Fig. 1, the internal combustion engine system 1 may include a generator 11 connected to the power transmission shaft 21 of the internal combustion engine 2. The generator 11 is configured to recover the power generated by the internal combustion engine 2 via the power transmission shaft 21 and generate electricity using the recovered power.

[0013] 2 is a schematic diagram illustrating an example of the configuration of an internal combustion engine 2 according to an embodiment of the present disclosure. As shown in FIG. 2 , each of the multiple cylinders 4 includes a cylinder body 41 and a piston 42 housed inside the cylinder body 41. Each of the multiple cylinders 4 has a combustion chamber 43 formed between the cylinder body 41 and the piston 42. The internal combustion engine 2 is configured to combust fuel and combustion gas in each combustion chamber 43 of the multiple cylinders 4.

[0014] In the following embodiments, a case will be described in which the internal combustion engine 2 is a gas engine configured to combust (premix combustion) a mixture of gas fuel (fuel) and air (combustion gas) in the combustion chamber 43, but some embodiments of the present disclosure are also applicable to cases in which the internal combustion engine 2 is a gasoline engine or a diesel engine that injects liquid fuel such as gasoline into air in the combustion chamber 43. In addition, in the following embodiments, a case will be described in which the internal combustion engine 2 is a four-stroke engine, but some embodiments of the present disclosure are also applicable to cases in which the internal combustion engine 2 is a two-stroke engine.

[0015] 2 , the internal combustion engine system 1 includes a gas fuel supply device (fuel supply device) 44 configured to supply gas fuel (fuel) to the cylinders 4, an ignition device (spark plug in the illustrated example) 45 that ignites an air-fuel mixture of the gas fuel and air in the combustion chamber 43, and an in-cylinder pressure acquisition device (in-cylinder pressure sensor in the illustrated example) 46 configured to acquire the in-cylinder pressure of the cylinders 4. The gas fuel supply device 44, the ignition device 45, and the in-cylinder pressure acquisition device 46 are provided individually for each cylinder 4.

[0016] The gas fuel supply device 44 may be a gas fuel injection valve (fuel injection valve) configured to inject gas fuel (fuel). In the embodiment shown in Fig. 2, the gas fuel supply device 44 is configured to supply gas fuel to a combustion chamber 43 formed inside the cylinder 4, but may also be configured to supply gas fuel to an air introduction line (combustion gas introduction line) 12 that introduces air (combustion gas) to the combustion chamber 43.

[0017] In addition, some embodiments of the present disclosure can also be applied to an internal combustion engine 2 that is configured to self-ignite a mixture of gas fuel (fuel) and air (combustion gas) in the combustion chamber 43 without having an ignition device 45.

[0018] As shown in Figure 2, the internal combustion engine system 1 includes the above-mentioned air inlet line 12, one end of which is connected to the combustion chamber 43 of the cylinder 4 and which introduces air into the combustion chamber 43 of the cylinder 4, an exhaust discharge line 13, one end of which is connected to the combustion chamber 43 of the cylinder 4 and which introduces unburned gas or exhaust gas from the combustion chamber 43 of the cylinder 4, and a gas fuel inlet line 14, one end of which is connected to a gas fuel supply device 44 and which introduces gas fuel from a gas fuel supply source (e.g., a gas storage tank) to the gas fuel supply device 44.

[0019] The air inlet line 12 and the exhaust discharge line 13 are branched into a plurality of lines, each of which is connected to a combustion chamber 43 of a corresponding cylinder 4. The gas fuel inlet line 14 is branched into a plurality of lines, each of which is connected to a gas fuel supply device 44 of a corresponding cylinder 4.

[0020] The air introduction line 12 forms a flow path for introducing air into the combustion chamber 43, and includes an intake port formed inside the internal combustion engine 2 and communicating with the combustion chamber 43. The exhaust discharge line 13 forms a flow path for discharging unburned gas or exhaust gas from the combustion chamber 43, and includes an exhaust port formed inside the internal combustion engine 2 and communicating with the combustion chamber 43. The gas fuel introduction line 14 forms a flow path for guiding gas fuel to the gas fuel supply device 44. Each of the air introduction line 12, the exhaust discharge line 13, and the gas fuel introduction line 14 is not limited to piping.

[0021] Each of the multiple internal cylinder pressure acquisition devices 46 is configured to acquire the internal cylinder pressure of the cylinder 4 to which the internal cylinder pressure acquisition device 46 corresponds. In the illustrated embodiment, the internal cylinder pressure acquisition device 46 is configured to generate electricity corresponding to the pressure inside the cylinder 4 to which the internal cylinder pressure acquisition device 46 is attached. In some embodiments, the internal cylinder pressure acquisition device 46 uses a piezoelectric element, a strain gauge, or the like as a pressure detection element. By monitoring the amount of electricity generated by the internal cylinder pressure acquisition device 46 in the pre-ignition determination device 3 of the internal combustion engine 2, the internal pressure of the cylinder 4 to which the internal cylinder pressure acquisition device 46 is attached can be monitored.

[0022] (Pre-ignition Determination Device) The pre-ignition determination device 3 may be configured as a microcomputer including a central processing unit (CPU) including a processor, a random access memory (RAM), a read-only memory (ROM), an I / O interface, etc. The pre-ignition determination device 3 may be an electronic control unit mounted on the engine control unit 30 that controls the operation of each device included in the internal combustion engine system 1, such as the internal combustion engine 2, the gas fuel supply device 44, and the ignition device 45, or may be configured as an electronic control unit separate from the engine control unit 30. Furthermore, the pre-ignition determination device 3 may be implemented as one of the functions (programs or circuits) included in the engine control unit 30.

[0023] The gas fuel supply device 44 is configured so that the timing (supply crank angle) and amount of gas fuel supplied are controlled by the engine control unit 30. The ignition device 45 is configured so that the ignition timing (ignition crank angle) is controlled by the engine control unit 30. The gas fuel supplied to the combustion chamber 43 or the air inlet line 12 by the gas fuel supply device 44 is mixed with air sent to the combustion chamber 43 via the air inlet line 12 and then combusted in the combustion chamber 43. Exhaust gas generated by combustion in the combustion chamber 43 is discharged to the outside of the internal combustion engine system 1 via the exhaust discharge line 13.

[0024] The pre-ignition determination device 3 receives various signals from devices (e.g., the internal combustion engine 2 and the generator 11) and sensors (e.g., the in-cylinder pressure acquisition device 46) provided in the internal combustion engine system 1 via an I / O interface and inputs them to a CPU or the like. The CPU is configured to execute various controls in accordance with control programs stored in a ROM. The pre-ignition determination device 3 includes a storage unit 31 that stores various signals (e.g., detected values ​​from the in-cylinder pressure acquisition device 46) from the devices and sensors provided in the internal combustion engine system 1.

[0025] 3 is an explanatory diagram for explaining a combustion cycle C of the internal combustion engine 2 according to one embodiment of the present disclosure. The internal combustion engine 2 is configured to generate output by repeatedly performing a combustion cycle C, one cycle of which consists of four strokes, namely, an intake stroke PR1, a compression stroke PR2, an expansion stroke PR3, and an exhaust stroke PR4, in each of the multiple cylinders 4 during operation of the internal combustion engine 2.

[0026] During the intake stroke PR1, gas (air or a mixture of air and gas fuel) is drawn into the combustion chamber 43 via the air inlet line 12, and the piston 42 moves from top dead center (TDC) to bottom dead center (BDC). During the compression stroke PR2, the gas drawn into the combustion chamber 43 during the intake stroke PR1 is compressed, and the piston 42 moves from bottom dead center (BDC) to top dead center (TDC). During the expansion stroke PR3, the gas compressed during the compression stroke PR2 expands (burns), and the piston 42 moves from top dead center (TDC) to bottom dead center (BDC). During the exhaust stroke PR4, the gas expanded during the expansion stroke PR3 is discharged from the combustion chamber 43 to the exhaust discharge line 13, and the piston 42 moves from bottom dead center (BDC) to top dead center (TDC).

[0027] Ignition by the ignition device 45 is performed when the piston 42 moves to near compression top dead center (TDC) during the compression stroke PR2. TL in FIG. 3 indicates an example of the ignition timing (ignition timing) by the ignition device 45. In one embodiment, when the crank angle CA at compression top dead center (TDC) is 0°, the crank angle CA at the ignition timing TL is −15°. A predetermined period T1 before the ignition timing TL in the combustion cycle C is defined as a boundary, and ignition occurring between this boundary and the ignition timing TL is defined as early pre-ignition. In the illustrated example, the crank angle CA at this boundary is −40°. The pre-ignition determination method and pre-ignition determination device 3 according to some embodiments are methods (devices) for determining whether or not an internal combustion engine 2 is experiencing early pre-ignition.

[0028] (Measurement Timing of In-Cylinder Pressure) FIG. 4 is an explanatory diagram illustrating the measurement timing of the in-cylinder pressure used to determine whether or not early pre-ignition has occurred in one embodiment of the present disclosure. Among the multiple cylinders 4 of the internal combustion engine 2, a cylinder 4 that is the target of the determination of whether or not early pre-ignition has occurred in the internal combustion engine 2 is defined as a target cylinder 4A, and cylinders 4 other than the target cylinder 4A are defined as non-target cylinders 4B. The determination of whether or not early pre-ignition has occurred uses a first pressure P1, a second pressure P2, and a pressure ratio P2 / P1, which is the ratio of the second pressure P2 to the first pressure P1. The pressure used to determine whether or not early pre-ignition has occurred may be a difference from the pressure at a reference point, for example, the pressure at bottom dead center (BDC) before the start of compression. In this case, the influence of drift of the in-cylinder pressure acquisition device (in-cylinder pressure sensor) 46 can be reduced.

[0029] The first pressure P1 is the pressure (in-cylinder pressure) at a predetermined crank angle (first crank angle) CA1 during the compression stroke PR2 prior to the compression top dead center TDC in the target combustion cycle of the target cylinder 4A. The second pressure P2 is the pressure (in-cylinder pressure) at a predetermined crank angle (second crank angle) CA2 during the expansion stroke PR3 after the compression top dead center TDC in the target combustion cycle of the target cylinder 4A. In the illustrated embodiment, the first crank angle CA1 and the second crank angle CA2 have the same crank angle difference from the compression top dead center TDC, but the crank angle difference may be different. Also, as shown in FIG. 4 , the first crank angle CA1 is prior to the ignition timing TL.

[0030] FIG. 5 is an explanatory diagram illustrating changes in in-cylinder pressure with respect to the combustion state in cylinder 4. As shown in FIG. 5 , when combustion in cylinder 4 is normal combustion or normal pre-ignition, a pressure increase occurs due to combustion between the first crank angle CA1 and the second crank angle CA2, resulting in a relatively high second pressure P2. The pressure ratio P2 / P1, which is the ratio of the second pressure P2 to the first pressure P1, is also relatively high. In contrast, when combustion in cylinder 4 is early pre-ignition, combustion completes before the first crank angle CA1, and the pressure waveform thereafter corresponds to compression and expansion due to simple movement of the piston 42 without combustion. In this case, the pressure ratio P2 / P1 is relatively low, similar to that in the case of a misfire (see FIG. 6 ).

[0031] As shown in FIG. 6, when combustion in cylinder 4 is early pre-ignition or misfire, the pressure ratio P2 / P1 is smaller than the pressure ratio P2 / P1 in normal combustion or normal pre-ignition. Therefore, by comparing these pressure ratios, it is possible to distinguish between early pre-ignition or misfire and normal combustion or normal pre-ignition in cylinder 4.

[0032] On the other hand, as shown in Figures 5 and 6, when combustion in cylinder 4 is early pre-ignition, the first pressure P1 is larger than the first pressure P1 in normal combustion, normal pre-ignition, or misfire. Therefore, by comparing the first pressure P1, it is possible to distinguish between early pre-ignition and misfire in combustion in cylinder 4.

[0033] 7 and 8 are explanatory diagrams illustrating an example of a flow for detecting early pre-ignition according to an embodiment of the present disclosure. A pre-ignition determination method according to some embodiments includes an in-cylinder pressure information acquisition step and a pre-ignition detection step. The pre-ignition determination method may be performed by the pre-ignition determination device 3. The pre-ignition determination device 3 includes an in-cylinder pressure information acquisition unit 32 and an in-cylinder pre-ignition determination unit 33. The in-cylinder pressure information acquisition unit 32 and the pre-ignition determination unit 33 are configured to acquire necessary information from the storage unit 31. The in-cylinder pressure information acquisition unit 32 may also acquire information related to the in-cylinder pressure of the cylinder 4 (a signal, for example, a value detected by the in-cylinder pressure acquisition device 46) from the in-cylinder pressure acquisition device 46. The pre-ignition determination unit 33 may also acquire the output power and rotation speed of the internal combustion engine 2 from devices (for example, the internal combustion engine 2 or the generator 11) provided in the internal combustion engine system 1.

[0034] (In-cylinder Pressure Information Acquisition Step) The in-cylinder pressure information acquisition step acquires at least the first pressure P1, the second pressure P2, and a pressure ratio P2 / P1, which is the ratio of the second pressure P2 to the first pressure P1, in a target combustion cycle of a target cylinder 4A that is to be determined for the presence or absence of pre-ignition in the internal combustion engine 2. As shown in Figures 7 and 8 , the in-cylinder pressure information acquisition step includes a first pressure acquisition step S11 that acquires the first pressure P1 in the target combustion cycle of the target cylinder 4A, a second pressure acquisition step S12 that acquires the second pressure P2 in the target combustion cycle of the target cylinder 4A, and a pressure ratio acquisition step S13 that acquires the pressure ratio P2 / P1 in the target combustion cycle of the target cylinder 4A.

[0035] The in-cylinder pressure information acquisition steps (first pressure acquisition step S11, second pressure acquisition step S12, and pressure ratio acquisition step S13) may be performed by the in-cylinder pressure information acquisition unit 32. The in-cylinder pressure information acquisition unit 32 acquires the first pressure P1 and the second pressure P2 in the combustion cycle to be determined of the target cylinder 4A from the storage unit 31 or an in-cylinder pressure acquisition device 46 provided in the target cylinder 4A. The in-cylinder pressure information acquisition unit 32 may calculate the pressure ratio P2 / P1 from the acquired first pressure P1 and second pressure P2, or may acquire the pressure ratio P2 / P1 calculated outside the in-cylinder pressure information acquisition unit 32.

[0036] (Pre-ignition Detection Step) In the pre-ignition detection step, it is determined that the target cylinder 4A has pre-ignited if both the pressure ratio determination condition and the first pressure determination condition are satisfied. The pre-ignition detection step includes a pressure ratio determination step S14, a first pressure determination step S15, and a pre-ignition determination step S16 that determines whether or not pre-ignition has occurred based on the determination results of the pressure ratio determination step S14 and the first pressure determination step S15.

[0037] In the pressure ratio determination step S14, it is determined whether or not the pressure ratio P2 / P1 acquired in the above-mentioned in-cylinder pressure information acquisition step satisfies the pressure ratio determination condition that the pressure ratio P2 / P1 is smaller than the pressure ratio standard data PRSD corresponding to the pressure ratio P2 / P1 by a predetermined amount or more.

[0038] In the first pressure determination step S15, it is determined whether or not the first pressure P1 acquired in the above-mentioned in-cylinder pressure information acquisition step satisfies the first pressure determination condition that the first pressure P1 is greater than the first pressure standard data P1SD corresponding to the first pressure P1 by a predetermined amount.

[0039] In the pre-ignition determination step S16, it is determined that the target cylinder 4A has pre-ignited if both the pressure ratio determination condition and the first pressure determination condition are satisfied.

[0040] The pre-ignition detection steps (pressure ratio determination step S14, first pressure determination step S15, and pre-ignition determination step S16) may be performed by the pre-ignition determination unit 33. That is, the pre-ignition determination unit 33 is configured to determine that the target cylinder 4A has pre-ignited when both the pressure ratio determination condition and the first pressure determination condition are satisfied.

[0041] If the pressure ratio determination condition is satisfied, the combustion in the combustion cycle to be determined for the target cylinder 4A can be determined to be early pre-ignition or misfire, rather than normal combustion or normal pre-ignition. Furthermore, if the first pressure determination condition is satisfied, the combustion in the combustion cycle to be determined for the target cylinder 4A can be determined to be early pre-ignition, rather than misfire. In other words, if both the pressure ratio determination condition and the first pressure determination condition are satisfied, the combustion in the combustion cycle to be determined for the target cylinder 4A can be determined to be early pre-ignition, rather than normal combustion, normal pre-ignition, or misfire. Therefore, the pre-ignition determination method (pre-ignition determination device 3) described above makes it possible to accurately determine whether pre-ignition occurs in the internal combustion engine 2.

[0042] (First Pressure Standard Data) In some embodiments, as shown in FIG. 7 , the first pressure standard data P1SD is the average value of the first pressure P1 of a plurality of combustion cycles preceding the target combustion cycle of the target cylinder 4A. Here, the plurality of combustion cycles preceding the target combustion cycle of the target cylinder 4A are preferably a plurality of consecutive combustion cycles immediately preceding the target combustion cycle. Specifically, if the target combustion cycle is defined as the nth (n is a natural number) combustion cycle Cn and the mth (m is a natural number) combustion cycle preceding the target combustion cycle is defined as Cn-m, the plurality of combustion cycles include combustion cycles Cn-1, Cn-2, ..., Cn-m. Note that the plurality of combustion cycles preferably do not include a combustion cycle determined to be an early pre-ignition.

[0043] 7 , the first pressure determination step S15 may determine that the first pressure determination condition is satisfied when the first pressure P1 in the target combustion cycle of the target cylinder 4A is greater than the average value of the first pressure P1 over the multiple combustion cycles by a predetermined amount (step S151). The pre-ignition determination unit 33 may be configured to obtain the first pressure P1 over the multiple combustion cycles from the storage unit 31 and calculate the average value of the first pressure P1.

[0044] By using the average value of the first pressure P1 of multiple combustion cycles prior to the combustion cycle to be judged of the target cylinder 4A, which is easily available, as the first pressure standard data P1SD, it is possible to accurately determine whether or not pre-ignition has occurred in the target cylinder 4A.

[0045] In some embodiments, as shown in FIG. 8, the above-mentioned first pressure standard data P1SD is the average value of the first pressure P1 of a combustion cycle whose timing at least partially overlaps with the combustion cycle to be determined of a plurality of cylinders 4B other than the target cylinder 4A of the internal combustion engine 2.

[0046] FIG. 9 is an explanatory diagram illustrating the combustion cycles of multiple cylinders 4 (4A, 4B) of an internal combustion engine 2 according to an embodiment of the present disclosure. As shown in FIG. 9 , if the target combustion cycle of a target cylinder 4A is defined as the nth (n is a natural number) combustion cycle Cn and the combustion cycle immediately preceding the target combustion cycle is defined as Cn-1, the combustion cycles of multiple cylinders (non-target cylinders) 4B (4C, 4D) other than the target cylinder 4A that at least partially overlap in timing with the target combustion cycle may include the nth combustion cycle, the n-1th combustion cycle, or the n+1th combustion cycle. However, any of these may be used; for example, the nth combustion cycle may be used. Note that the combustion cycles that at least partially overlap in timing with the target combustion cycle preferably do not include combustion cycles in which fuel supply was intentionally stopped and misfired, or combustion cycles in which measurement was not performed by the in-cylinder pressure acquisition device 46.

[0047] 8 , the first pressure determination step S15 may determine that the first pressure determination condition is satisfied if the first pressure P1 of the target combustion cycle of the target cylinder 4A is greater than or equal to a predetermined value of the average value of the first pressure P1 of combustion cycles of the non-target cylinders 4B that at least partially overlap in timing with the target combustion cycles (step S152). The pre-ignition determination unit 33 may be configured to obtain the first pressure P1 of the combustion cycles that at least partially overlap in timing with the target combustion cycle from the memory unit 31 or the in-cylinder pressure acquisition device 46 mounted on the non-target cylinder 4B, and calculate the average value of the first pressure P1.

[0048] By adopting the average value of the first pressure P1 of the combustion cycle in which the non-target cylinder 4B has the same operating conditions, such as the load rate, as the target cylinder 4A as the first pressure standard data P1SD, erroneous detection can be suppressed by comparison with the non-target cylinder 4B even if there are fluctuations in the operating conditions, such as the load rate, and therefore it is possible to accurately determine whether or not pre-ignition has occurred in the target cylinder 4A.

[0049] In some embodiments, the above-described first pressure standard data P1SD is a set value of the first pressure that is set in accordance with the output and rotation speed of the internal combustion engine 2. The pre-ignition determination unit 33 may be configured to acquire, from the storage unit 31, association information that associates the output, rotation speed, and set value of the first pressure of the internal combustion engine 2, and to calculate the set value of the first pressure from the output and rotation speed of the internal combustion engine 2 based on the association information.

[0050] By adopting a set value of the first pressure that is set according to the output and rotation speed of the internal combustion engine 2 as the first pressure standard data P1SD, it is possible to suppress erroneous detection or oversight when there are fluctuations in the output or rotation speed of the internal combustion engine 2, thereby making it possible to accurately determine the presence or absence of pre-ignition in the target cylinder 4A. Note that in some other embodiments, the above-mentioned first pressure standard data P1SD may be a set value (fixed value) of the first pressure that does not change according to the output and rotation speed of the internal combustion engine 2.

[0051] In some embodiments, as shown in FIG. 7, the above-mentioned pressure ratio standard data PRSD is a set value (fixed value) of the pressure ratio that does not change depending on the output and rotation speed of the internal combustion engine 2.

[0052] As shown in FIG. 7, the pressure ratio determination step S14 may determine that the pressure ratio determination condition is met when the pressure ratio P2 / P1 of the combustion cycle to be determined for the target cylinder 4A is smaller than the set value (fixed value) of the pressure ratio by a predetermined amount (step S141).

[0053] In some embodiments, as shown in FIG. 7 , the pressure ratio standard data PRSD is the average value of the pressure ratios P2 / P1 of multiple combustion cycles preceding the target combustion cycle of the target cylinder 4A. Here, the multiple combustion cycles preceding the target combustion cycle of the target cylinder 4A are preferably multiple consecutive combustion cycles immediately preceding the target combustion cycle. Specifically, if the target combustion cycle is defined as the nth (n is a natural number) combustion cycle Cn and the mth (m is a natural number) combustion cycle preceding the target combustion cycle is defined as Cn-m, the multiple combustion cycles include combustion cycles Cn-1, Cn-2, ..., Cn-m. It is preferable that the multiple combustion cycles not include any combustion cycle determined to have early pre-ignition.

[0054] 7 , the pressure ratio determination step S14 may determine that the pressure ratio determination condition is satisfied when the pressure ratio P2 / P1 of the target combustion cycle of the target cylinder 4A is smaller than the average value of the pressure ratios P2 / P1 over the multiple combustion cycles by a predetermined amount (step S142). The pre-ignition determination unit 33 may be configured to obtain the pressure ratios P2 / P1 over the multiple combustion cycles from the storage unit 31 or a past pressure ratio information acquisition unit 34 (described later) and calculate the average value of the pressure ratios P2 / P1.

[0055] By using the average value of the pressure ratio P2 / P1 of multiple combustion cycles prior to the combustion cycle to be judged of the target cylinder 4A, which is easily available, as the pressure ratio standard data PRSD, it is possible to accurately determine whether or not pre-ignition has occurred in the target cylinder 4A.

[0056] In some embodiments, as shown in FIG. 8 , the pressure ratio standard data PRSD is the average value of the pressure ratio P2 / P1 of combustion cycles that at least partially overlap with the combustion cycle to be determined for a plurality of cylinders 4B other than the target cylinder 4A of the internal combustion engine 2.

[0057] 9 , if the target combustion cycle of the target cylinder 4A is defined as the nth combustion cycle Cn (n is a natural number) and the combustion cycle immediately before the target combustion cycle is defined as Cn−1, the combustion cycles of the cylinders 4B (4C, 4D) other than the target cylinder 4A (non-target cylinders) that at least partially overlap in timing with the target combustion cycle may include the nth combustion cycle, the n−1th combustion cycle, or the n+1th combustion cycle, but any of these may be used. For example, the nth combustion cycle may be used. Note that it is preferable that the combustion cycles that at least partially overlap in timing with the target combustion cycle do not include combustion cycles in which fuel supply was intentionally stopped and misfired, or combustion cycles in which measurement was not performed by the in-cylinder pressure acquisition device 46.

[0058] 8 , the pressure ratio determination step S14 may determine that the pressure ratio determination condition is satisfied when the pressure ratio P2 / P1 of the target combustion cycle of the target cylinder 4A is smaller than the average value of the pressure ratios P2 / P1 of the combustion cycles of the non-target cylinders 4B whose timings at least partially overlap with those of the target combustion cycles of the non-target cylinders 4B by a predetermined value or more (step S144). The pre-ignition determination unit 33 may be configured to obtain the pressure ratios P2 / P1 of the combustion cycles whose timings at least partially overlap with those of the target combustion cycle from the storage unit 31 and calculate the average value of the pressure ratios P2 / P1.

[0059] By using the average value of P2 / P1 of the combustion cycle of the non-target cylinder 4B, which has the same operating conditions such as load factor as the target cylinder 4A, as the pressure ratio standard data PRSD, erroneous detection can be suppressed by comparison with the non-target cylinder 4B even if there are fluctuations in operating conditions such as load factor, so that the presence or absence of pre-ignition in the target cylinder 4A can be accurately determined.

[0060] In some embodiments, the pressure ratio standard data PRSD is a set value of the pressure ratio P2 / P1 that is set according to the output and rotation speed of the internal combustion engine 2. The pre-ignition determination unit 33 may be configured to acquire, from the storage unit 31, association information that associates the output, rotation speed, and set value of the pressure ratio P2 / P1 of the internal combustion engine 2, and to calculate the set value of the pressure ratio P2 / P1 from the output and rotation speed of the internal combustion engine 2 based on the association information.

[0061] By adopting a pressure ratio setting value that is set according to the output and rotation speed of the internal combustion engine 2 as the pressure ratio standard data PRSD, it is possible to suppress erroneous detection or oversight when there are fluctuations in the output or rotation speed of the internal combustion engine 2, thereby making it possible to accurately determine whether or not pre-ignition has occurred in the target cylinder 4A.

[0062] A pre-ignition determination method according to some embodiments includes a past pressure ratio information acquisition step and a pressure ratio variation calculation step. The pre-ignition determination device 3 includes a past pressure ratio information acquisition unit 34 and a pressure ratio variation calculation unit 35.

[0063] In the past pressure ratio information acquisition step, pressure ratios of a plurality of combustion cycles prior to the combustion cycle to be determined for the target cylinder 4A are acquired. The past pressure ratio information acquisition step may be performed by the past pressure ratio information acquisition unit 34. The past pressure ratio information acquisition unit 34 may acquire the first pressure P1 and the second pressure P2 in past combustion cycles prior to the combustion cycle to be determined for the target cylinder 4A from the storage unit 31 and calculate the pressure ratio P2 / P1 from the acquired first pressure P1 and second pressure P2, or may acquire a pressure ratio P2 / P1 calculated outside the past pressure ratio information acquisition unit 34.

[0064] In the pressure ratio variation calculation step, the pressure ratio of the combustion cycle to be determined and the pressure ratios of the combustion cycles preceding the combustion cycle to be determined are statistically processed to calculate a variation amount VA representing the statistical variation of the pressure ratio. The variation amount VA may be, for example, a standard deviation. The pressure ratio variation calculation step may be performed by a pressure ratio variation calculation unit 35.

[0065] The above-mentioned pressure ratio determination conditions include a condition that the variation amount VA calculated in the pressure ratio variation amount calculation step is greater than the variation amount standard data VASD, which is the pressure ratio standard data PRSD corresponding to the variation amount VA, by a predetermined amount or more (S143).

[0066] By adopting the amount of variation VA (e.g., standard deviation) as a judgment parameter for the pressure ratio judgment condition, early pre-ignition can be distinguished from other combustion events (normal combustion, normal pre-ignition, misfire), and therefore it is possible to accurately determine whether the combustion in the combustion cycle being judged for the target cylinder 4A is early pre-ignition.

[0067] Note that the pressure ratio determination condition in pressure ratio determination step S14 may be satisfied when any one of the determination conditions in steps S141, S142, S143, or S144 described above is satisfied. For example, as shown in Fig. 7, the pressure ratio determination condition in pressure ratio determination step S14 may be satisfied when any one of the determination conditions in steps S141, S142, or S143 described above is satisfied. Also, as shown in Fig. 8, the pressure ratio determination condition in pressure ratio determination step S14 may be satisfied when any one of the determination conditions in steps S141 or S144 described above is satisfied.

[0068] In some embodiments, the variation standard data VASD is an average value of the variation (e.g., standard deviation) of the pressure ratio P2 / P1 for a plurality of combustion cycles preceding the target combustion cycle of the target cylinder 4A. Here, the plurality of combustion cycles preceding the target combustion cycle of the target cylinder 4A are preferably a plurality of consecutive combustion cycles immediately preceding the target combustion cycle. Specifically, if the target combustion cycle is defined as the nth (n is a natural number) combustion cycle Cn and the mth (m is a natural number) combustion cycle preceding the target combustion cycle is defined as Cn-m, the plurality of combustion cycles include combustion cycles Cn-1, Cn-2, ..., Cn-m. It is preferable that the plurality of combustion cycles does not include a combustion cycle determined to have early pre-ignition.

[0069] 7 , the pressure ratio determination step S14 may determine that the pressure ratio determination condition is satisfied when the amount of variation in the pressure ratio P2 / P1 in the target combustion cycle of the target cylinder 4A is greater than or equal to a predetermined value as compared to the average value of the amount of variation in the pressure ratio P2 / P1 over the multiple combustion cycles (step S143). The pre-ignition determination unit 33 may be configured to obtain the pressure ratios P2 / P1 over the multiple combustion cycles from the storage unit 31 or a past pressure ratio information acquisition unit 34 (described later) and calculate the average value of the pressure ratios P2 / P1.

[0070] By using the average value of the variation in the pressure ratio P2 / P1 of multiple combustion cycles prior to the combustion cycle to be determined for the target cylinder 4A, which is easily available, as the pressure ratio standard data PRSD, it is possible to accurately determine whether or not pre-ignition occurs in the target cylinder 4A.

[0071] In some embodiments, the above-described variation amount standard data VASD is a set value of the variation amount that is set according to the output and rotation speed of the internal combustion engine 2. The pre-ignition determination unit 33 may be configured to acquire, from the storage unit 31, association information that associates the output, rotation speed, and set value of the variation amount of the internal combustion engine 2, and to calculate the set value of the variation amount from the output and rotation speed of the internal combustion engine 2 based on the association information.

[0072] By adopting a set value of the variation amount that is set according to the output and rotation speed of the internal combustion engine 2 as the variation amount standard data VASD, it is possible to suppress erroneous detection or oversight when there are fluctuations in the output or rotation speed of the internal combustion engine 2, thereby making it possible to accurately determine the presence or absence of pre-ignition in the target cylinder 4A. Note that in some other embodiments, the above-mentioned variation amount standard data VASD may be a set value (fixed value) of the variation amount that does not change according to the output and rotation speed of the internal combustion engine 2.

[0073] 10 and 11 are explanatory diagrams illustrating an example of a flow for detecting early pre-ignition according to an embodiment of the present disclosure. In some embodiments of the pre-ignition determination method, the above-described in-cylinder pressure information acquisition step acquires the maximum pressure MP in the target combustion cycle of the target cylinder 4A. The above-described pre-ignition detection step (pre-ignition determination unit 33) determines that the target cylinder 4A has pre-ignited if the maximum pressure determination condition is met in addition to the pressure ratio determination condition and the first pressure determination condition. The pre-ignition detection step includes a maximum pressure determination step that determines whether the maximum pressure MP acquired in the above-described in-cylinder pressure information acquisition step satisfies the maximum pressure determination condition. The pre-ignition determination step S16 determines whether pre-ignition has occurred based on the determination results of the pressure ratio determination step S14, the first pressure determination step S15, and the maximum pressure determination step. The pre-ignition determination step determines that the target cylinder 4A has pre-ignited if the pressure ratio determination condition, the first pressure determination condition, and the maximum pressure determination condition are met.

[0074] The maximum pressure determination condition includes a case where the maximum pressure MP is abnormal based on the maximum pressure MP acquired in the in-cylinder pressure information acquisition step and the maximum pressure standard data MPSD corresponding to the maximum pressure MP. For example, if the maximum pressure MP acquired in the in-cylinder pressure information acquisition step is greater than a predetermined value TMP of the maximum pressure MP, which is the maximum pressure standard data MPSD, by more than a predetermined amount, the abnormality determination is determined to be abnormal, and the maximum pressure determination condition is satisfied. The set value TMP is preferably set according to the output and rotation speed of the internal combustion engine 2, i.e., its value preferably varies according to the output and rotation speed of the internal combustion engine 2. By adding the maximum pressure determination condition to the pre-ignition determination conditions in this way, erroneous detection can be suppressed, thereby more accurately determining whether pre-ignition occurs in the target cylinder 4A.

[0075] In this specification, expressions expressing relative or absolute arrangements, such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial," not only strictly express such arrangements, but also express a state in which there is a relative displacement with a tolerance or an angle or distance to the extent that the same function is obtained. For example, expressions expressing that things are in an equal state, such as "identical," "equal," and "homogeneous," not only express a state in which there is a strict equivalence, but also express a state in which there is a tolerance or a difference to the extent that the same function is obtained. Furthermore, in this specification, expressions expressing shapes such as a rectangular shape or a cylindrical shape not only express shapes such as a rectangular shape or a cylindrical shape in the strict geometric sense, but also express shapes including concave and convex portions, chamfered portions, etc., to the extent that the same effect is obtained. Furthermore, in this specification, the expressions "comprise," "include," or "have" a component are not exclusive expressions that exclude the presence of other components.

[0076] The present disclosure is not limited to the above-described embodiments, but also includes modifications to the above-described embodiments and appropriate combinations of these modifications.

[0077] The contents of the above-described embodiments can be understood, for example, as follows.

[0078] 1) A pre-ignition determination method according to at least one embodiment of the present disclosure is a method for determining whether or not pre-ignition has occurred in an internal combustion engine (2), comprising: a cylinder pressure information acquisition step of acquiring at least a first pressure (P1) that is a pressure before a top dead center of compression stroke in a combustion cycle of a target cylinder (4A) that is a target for determining whether or not pre-ignition has occurred in the internal combustion engine (2), a second pressure (P2) that is a pressure after the top dead center of compression stroke in the combustion cycle of the target cylinder (4A), and a pressure ratio (P2 / P1) that is a ratio of the second pressure to the first pressure; and a pre-ignition detection step of determining that the target cylinder (4A) is experiencing pre-ignition when both a pressure ratio determination condition that the pressure ratio (P2 / P1) acquired in the in-cylinder pressure information acquisition step is smaller than pressure ratio standard data (PRSD) corresponding to the pressure ratio (P2 / P1) by a predetermined amount or more and a first pressure determination condition that the first pressure (P1) acquired in the in-cylinder pressure information acquisition step is larger than first pressure standard data (P1SD) corresponding to the first pressure (P1) by a predetermined amount or more are satisfied.

[0079] According to the method 1), when both the pressure ratio determination condition and the first pressure determination condition are satisfied, the combustion in the combustion cycle to be determined for the target cylinder (4A) can be determined to be early pre-ignition, rather than normal combustion, normal pre-ignition, or misfire. Therefore, the pre-ignition determination method described above makes it possible to accurately determine whether or not pre-ignition occurs in the internal combustion engine (2).

[0080] 2) In some embodiments, the pre-ignition determination method described in 1) above further includes: a past pressure ratio information acquisition step of acquiring the pressure ratios of a plurality of combustion cycles prior to the combustion cycle to be determined of the target cylinder (4A); and a pressure ratio variation calculation step of statistically processing the pressure ratio of the combustion cycle to be determined and the pressure ratios of the plurality of combustion cycles prior to the combustion cycle to be determined to calculate a variation amount (VA) representing the statistical variation of the pressure ratio, wherein the pressure ratio determination condition includes a condition that the variation amount (VA) calculated in the pressure ratio variation amount calculation step is greater than or equal to a predetermined value compared to variation amount standard data (VASD), which is the pressure ratio standard data (PRSD) corresponding to the variation amount (VA).

[0081] According to the method 2), by using the variation (VA) as a judgment parameter for the pressure ratio judgment condition, early pre-ignition can be distinguished from other combustion events (normal combustion, normal pre-ignition, misfire), and therefore it is possible to accurately determine whether or not combustion in the combustion cycle to be judged in the target cylinder (4A) is early pre-ignition.

[0082] 3) In some embodiments, in the pre-ignition determination method described in 1) above, the pressure ratio standard data (PRSD) is an average value of the pressure ratios of a plurality of combustion cycles of the target cylinder (4A) prior to the target combustion cycle to be determined.

[0083] According to the method 3) above, by using the average value of the pressure ratio (P2 / P1) of a plurality of combustion cycles prior to the combustion cycle to be determined for the target cylinder (4A), which is easily available, as the pressure ratio standard data (PRSD), it is possible to accurately determine whether or not pre-ignition occurs in the target cylinder (4A).

[0084] 4) In some embodiments, in the pre-ignition determination method described in 1), the pressure ratio standard data (PRSD) is an average value of the pressure ratios of combustion cycles of a plurality of cylinders (4B) other than the target cylinder (4A) of the internal combustion engine (2) whose timing at least partially overlaps with the combustion cycle to be determined.

[0085] According to the method of 4) above, by using the average value of the pressure ratio (P2 / P1) of the non-target cylinder (4B) in the combustion cycle having the same operating conditions, such as the load factor, as the target cylinder (4A), as the pressure ratio standard data (PRSD), it is possible to suppress erroneous detection by comparing with the non-target cylinder (4B) even when there are fluctuations in the operating conditions, such as the load factor, and therefore it is possible to accurately determine whether or not pre-ignition occurs in the target cylinder (4A).

[0086] 5) In some embodiments, in the pre-ignition determination method described in 1), the pressure ratio standard data (PRSD) is a set value of the pressure ratio that is set according to the output and rotation speed of the internal combustion engine (2).

[0087] According to the method of 5) above, by adopting a set value of the pressure ratio that is set according to the output and rotation speed of the internal combustion engine (2) as the pressure ratio standard data (PRSD), it is possible to suppress erroneous detection or oversight when there are fluctuations in the output or rotation speed of the internal combustion engine (2), and therefore it is possible to accurately determine whether or not pre-ignition occurs in the target cylinder (4A).

[0088] 6) In some embodiments, in the pre-ignition determination method described in 2) above, the variation amount standard data (VASD) is an average value of the variation amounts of a plurality of combustion cycles prior to the combustion cycle to be determined.

[0089] According to the method 6) above, by using the average value of the variation amounts of a plurality of combustion cycles prior to the combustion cycle to be judged of the target cylinder (4A), which is easily available, as the pressure ratio standard data (PRSD), it is possible to accurately judge whether or not pre-ignition occurs in the target cylinder (4A).

[0090] 7) In some embodiments, in the pre-ignition determination method described in 2), the variation amount standard data (VASD) is a set value of the variation amount that is set according to the output and rotation speed of the internal combustion engine (2).

[0091] According to the method of 7) above, by adopting a set value of the amount of variation that is set according to the output and rotation speed of the internal combustion engine (2) as the amount of variation standard data (VASD), it is possible to suppress erroneous detection or oversight when there are fluctuations in the output or rotation speed of the internal combustion engine (2), and therefore it is possible to accurately determine whether or not pre-ignition occurs in the target cylinder (4A).

[0092] 8) In some embodiments, in the pre-ignition determination method described in any of 1) to 7) above, the first pressure standard data (P1SD) is an average value of the first pressure (P1) for a plurality of combustion cycles prior to the combustion cycle to be determined for the target cylinder (4A).

[0093] According to the method of 8) above, by using the average value of the first pressure (P1) of a plurality of combustion cycles prior to the combustion cycle to be judged of the target cylinder (4A), which is easily available, as the first pressure standard data (P1SD), it is possible to accurately judge whether or not pre-ignition occurs in the target cylinder (4A).

[0094] 9) In some embodiments, in the pre-ignition determination method described in any of 1) to 8) above, the first pressure standard data (P1SD) is an average value of the first pressure (P1) of combustion cycles that overlap at least partially with the combustion cycle to be determined for a plurality of cylinders (4B) other than the target cylinder (4A) of the internal combustion engine (2).

[0095] According to the method of 9) above, by adopting the average value of the first pressure (P1) of the non-target cylinder (4B) in a combustion cycle having the same operating conditions, such as the load factor, as the target cylinder (4A) as the first pressure standard data (P1SD), it is possible to suppress erroneous detection by comparison with the non-target cylinder (4B) even when there are fluctuations in the operating conditions, such as the load factor, and therefore it is possible to accurately determine whether or not pre-ignition has occurred in the target cylinder (4A).

[0096] 10) In some embodiments, in the pre-ignition determination method described in any one of 1) to 9) above, the first pressure standard data (P1SD) is a set value of the first pressure that is set according to the output and rotation speed of the internal combustion engine (2).

[0097] According to the method of 10) above, by adopting a set value of the first pressure that is set according to the output and rotation speed of the internal combustion engine (2) as the first pressure standard data (P1SD), it is possible to suppress erroneous detection or oversight when there are fluctuations in the output or rotation speed of the internal combustion engine (2), and therefore it is possible to accurately determine whether or not pre-ignition occurs in the target cylinder (4A).

[0098] 11) In some embodiments, in the pre-ignition determination method described in any of 1) to 10) above, the in-cylinder pressure information acquisition step acquires a maximum pressure (MP) in the combustion cycle of the target cylinder (4A) to be determined, and the pre-ignition detection step determines that the target cylinder has pre-ignited if a maximum pressure determination condition that the maximum pressure (MP) is abnormal is further satisfied based on an abnormality determination based on the maximum pressure (MP) acquired in the in-cylinder pressure information acquisition step and maximum pressure standard data (MPSD) corresponding to the maximum pressure (MP).

[0099] According to the method 11), by adding the maximum pressure determination condition to the pre-ignition determination conditions, erroneous detection can be suppressed, and therefore, the presence or absence of pre-ignition in the target cylinder (4A) can be determined with higher accuracy.

[0100] 12) A pre-ignition determination device (3) according to at least one embodiment of the present disclosure is a pre-ignition determination device (3) for an internal combustion engine (2) configured to determine whether or not pre-ignition occurs in the internal combustion engine (2), and includes: an in-cylinder pressure information acquisition unit (32) configured to acquire at least a first pressure (P1) that is a pressure before a compression top dead center in a combustion cycle of a target cylinder (4A) that is a target for determining whether or not pre-ignition occurs in the internal combustion engine (2), a second pressure (P2) that is a pressure after the compression top dead center in the combustion cycle of the target cylinder (4A), and a pressure ratio (P2 / P1) that is a ratio of the second pressure to the first pressure; and a pre-ignition determination unit (33) configured to determine that the target cylinder (4A) is experiencing pre-ignition when both of the following conditions are satisfied: a pressure ratio determination condition that the pressure ratio (P2 / P1) acquired by the in-cylinder pressure information acquisition unit (32) is smaller than pressure ratio standard data (PRSD) corresponding to the pressure ratio (P2 / P1) by a predetermined amount or more; and a first pressure determination condition that the first pressure (P1) acquired by the in-cylinder pressure information acquisition unit (32) is larger than first pressure standard data (P1SD) corresponding to the first pressure (P1) by a predetermined amount or more.

[0101] According to the configuration of 12), when both the pressure ratio determination condition and the first pressure determination condition are satisfied, the combustion in the combustion cycle to be determined for the target cylinder (4A) can be determined to be early pre-ignition, rather than normal combustion, normal pre-ignition, or misfire. Therefore, the pre-ignition determination device (3) described above can accurately determine whether or not pre-ignition occurs in the internal combustion engine (2).

[0102] 13) In some embodiments, the pre-ignition determination device (3) described in 12) above further includes: a past pressure ratio information acquisition unit (34) configured to acquire the pressure ratio of a plurality of combustion cycles prior to the combustion cycle to be determined of the target cylinder (4A); and a pressure ratio variation calculation unit (35) configured to statistically process the pressure ratio of the combustion cycle to be determined and the pressure ratios of a plurality of combustion cycles prior to the combustion cycle to be determined, and calculate a variation amount (VA) representing a statistical variation of the pressure ratio, wherein the pressure ratio determination condition includes a condition that the variation amount (VA) calculated in the pressure ratio variation amount calculation unit (35) is greater than or equal to a predetermined value compared to variation amount standard data (VASD), which is the pressure ratio standard data (PRSD) corresponding to the variation amount (VA).

[0103] According to the configuration of 13), by using the variation (VA) as a judgment parameter for the pressure ratio judgment condition, early pre-ignition can be distinguished from other combustion events (normal combustion, normal pre-ignition, misfire), and therefore it is possible to accurately determine whether or not combustion in the combustion cycle to be judged of the target cylinder (4A) is early pre-ignition.

[0104] 14) In some embodiments, in the pre-ignition determination device (3) described in 12) or 13) above, the in-cylinder pressure information acquisition unit (32) is configured to acquire a maximum pressure (MP) in the combustion cycle of the target cylinder (4A) to be determined, and the pre-ignition determination unit (33) is configured to determine that the target cylinder (4A) has pre-ignited when a maximum pressure determination condition that the maximum pressure (MP) is abnormal is further satisfied based on an abnormality determination based on the maximum pressure (MP) acquired by the in-cylinder pressure information acquisition unit (32) and maximum pressure standard data (MPSD) corresponding to the maximum pressure (MP).

[0105] According to the above configuration 14), by adding the maximum pressure determination condition to the pre-ignition determination conditions, erroneous detection can be suppressed, and therefore, the presence or absence of pre-ignition in the target cylinder (4A) can be determined with higher accuracy.

[0106] REFERENCE SIGNS LIST 1 Internal combustion engine system 2 Internal combustion engine 3 Pre-ignition determination device 4 Cylinder 4A Target cylinder 4B Non-target cylinder 31 Storage unit 32 Cylinder pressure information acquisition unit 33 Pre-ignition determination unit 34 Past pressure ratio information acquisition unit 35 Pressure ratio variation amount calculation unit

Claims

1. A method for determining whether or not an internal combustion engine has pre-ignition, the method comprising: an in-cylinder pressure information acquisition step for acquiring at least a first pressure, which is the pressure before top dead center of compression stroke in a combustion cycle of a target cylinder that is to be determined whether or not the internal combustion engine has pre-ignition; a second pressure, which is the pressure after top dead center of compression stroke in a combustion cycle of the target cylinder that is to be determined whether or not the internal combustion engine has pre-ignition; and an in-cylinder pressure detection step for determining that the target cylinder has pre-ignition if both of the following conditions are satisfied: a pressure ratio determination condition that the pressure ratio acquired in the in-cylinder pressure information acquisition step is smaller than standard pressure ratio data corresponding to the pressure ratio by a predetermined amount or more; and a first pressure determination condition that the first pressure acquired in the in-cylinder pressure information acquisition step is larger than standard first pressure data corresponding to the first pressure by a predetermined amount or more.

2. The pre-ignition determination method according to claim 1, further comprising: a past pressure ratio information acquisition step of acquiring the pressure ratios of a plurality of combustion cycles prior to the combustion cycle to be determined for the target cylinder; and a pressure ratio variation calculation step of statistically processing the pressure ratio of the combustion cycle to be determined and the pressure ratios of a plurality of combustion cycles prior to the combustion cycle to be determined to calculate a variation amount representing the statistical variation of the pressure ratio, wherein the pressure ratio determination condition includes a condition that the variation amount calculated in the pressure ratio variation amount calculation step is greater than or equal to a predetermined value compared to variation amount standard data, which is the pressure ratio standard data corresponding to the variation amount.

3. The pre-ignition determination method according to claim 1, wherein the standard pressure ratio data is an average value of the pressure ratios of a plurality of combustion cycles of the target cylinder prior to the combustion cycle to be determined.

4. The pre-ignition determination method according to claim 1, wherein the standard pressure ratio data is an average value of the pressure ratios of combustion cycles of a plurality of cylinders other than the target cylinder of the internal combustion engine, the combustion cycles of which timing at least partially overlap with the combustion cycle to be determined.

5. The pre-ignition determination method according to claim 1, wherein the standard pressure ratio data is a set value of the pressure ratio that is set according to the output and rotation speed of the internal combustion engine.

6. The pre-ignition determination method according to claim 2, wherein the standard data of variation is an average value of the variation amounts of a plurality of combustion cycles prior to the combustion cycle to be determined.

7. The pre-ignition determination method according to claim 2, wherein the standard data of the amount of variation is a set value of the amount of variation that is set according to the output and rotation speed of the internal combustion engine.

8. A method for determining pre-ignition as claimed in any one of claims 1 to 7, wherein the first pressure standard data is an average value of the first pressure for a plurality of combustion cycles of the target cylinder prior to the combustion cycle to be determined.

9. A method for determining pre-ignition as claimed in any one of claims 1 to 7, wherein the first pressure standard data is an average value of the first pressure of combustion cycles of a plurality of cylinders other than the target cylinder of the internal combustion engine, the combustion cycles overlapping at least partially in timing with the combustion cycle to be determined.

10. A method for determining pre-ignition according to any one of claims 1 to 7, wherein the first pressure standard data is a set value of the first pressure that is set according to the output and rotation speed of the internal combustion engine.

11. A pre-ignition determination method as claimed in any one of claims 1 to 7, wherein in the cylinder pressure information acquisition step, a maximum pressure in the combustion cycle of the target cylinder to be determined is acquired, and in the pre-ignition detection step, it is determined that the target cylinder has pre-ignited if a maximum pressure determination condition that the maximum pressure is abnormal is further satisfied based on an abnormality determination based on the maximum pressure acquired in the cylinder pressure information acquisition step and maximum pressure standard data corresponding to the maximum pressure.

12. A pre-ignition determination device for an internal combustion engine configured to determine whether or not pre-ignition has occurred in an internal combustion engine, comprising: an in-cylinder pressure information acquisition unit configured to acquire at least a first pressure, which is the pressure before top dead center of compression stroke in a combustion cycle of a target cylinder that is to be determined as to whether or not pre-ignition has occurred in the internal combustion engine; a second pressure, which is the pressure after top dead center of compression stroke in a combustion cycle of the target cylinder that is to be determined as to whether or not pre-ignition has occurred in the internal combustion engine; and a pre-ignition determination unit configured to determine that the target cylinder has pre-ignited if both a pressure ratio determination condition that the pressure ratio acquired by the in-cylinder pressure information acquisition unit is smaller than standard pressure ratio data corresponding to the pressure ratio by a predetermined amount or more and a first pressure determination condition that the first pressure acquired by the in-cylinder pressure information acquisition unit is larger than standard first pressure data corresponding to the first pressure by a predetermined amount or more are satisfied.

13. A pre-ignition judgment device as described in claim 12, further comprising: a past pressure ratio information acquisition unit configured to acquire the pressure ratio of a plurality of combustion cycles prior to the combustion cycle to be judged of the target cylinder; and a pressure ratio variation amount calculation unit configured to statistically process the pressure ratio of the combustion cycle to be judged and the pressure ratios of a plurality of combustion cycles prior to the combustion cycle to be judged, and calculate a variation amount representing the statistical variation of the pressure ratio, wherein the pressure ratio judgment condition includes a condition that the variation amount calculated by the pressure ratio variation amount calculation unit is greater than or equal to a predetermined value compared to variation amount standard data, which is the pressure ratio standard data corresponding to the variation amount.

14. A pre-ignition judgment device as described in claim 12 or 13, wherein the in-cylinder pressure information acquisition unit is configured to acquire the maximum pressure in the combustion cycle of the target cylinder to be judged, and the pre-ignition judgment unit is configured to judge that the target cylinder has pre-ignited when a maximum pressure judgment condition that the maximum pressure is abnormal is further satisfied based on an abnormality judgment based on the maximum pressure acquired by the in-cylinder pressure information acquisition unit and maximum pressure standard data corresponding to the maximum pressure.

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