JP6002067B2 - Engine combustion fluctuation detection device and engine combustion fluctuation detection method - Google Patents

Description

  The present invention relates to an engine combustion fluctuation detection device and an engine combustion fluctuation detection method.

  2. Description of the Related Art Conventionally, a technique for detecting the combustion state of each cylinder of an engine based on rotation fluctuation of a crankshaft has been proposed (see, for example, Patent Document 1). By the way, in general, the rotational speed of the crankshaft of a multi-cylinder engine changes from a decreasing direction to an increasing direction at the end of the compression stroke of a certain cylinder as the combustion starts in the cylinder, and monotonically at the beginning of the expansion stroke of the cylinder. It increases and then changes in a decreasing direction as the compression pressure of the other cylinders entering the compression stroke increases.

  Therefore, in the technique described in Patent Document 1, in order to detect the combustion state of each cylinder while eliminating the influence of other cylinders (that is, the cylinders in the compression stroke described above), The average of the crankshaft at the initial stage of combustion of each cylinder, from when the rotational angular velocity changes from the reduced state to the increased state until the crankshaft rotates by a predetermined angle (or until it next changes to the reduced state) Rotational angular velocity is detected.

JP 2000-104598 A

  As described above, the technique disclosed in Patent Document 1 detects the angular velocity of the crankshaft at the initial stage of combustion of a predetermined cylinder, thereby detecting a cylinder whose ignition timing is one after the predetermined cylinder (hereinafter referred to as “rear cylinder”). The detection of the angular velocity is attempted by eliminating the influence of the compression stroke. However, the angular velocity of the crankshaft in the early stage of combustion of the predetermined cylinder is affected by the angular velocity (that is, the combustion state of the front cylinder) of the cylinder whose ignition timing is one prior to the predetermined cylinder (hereinafter also referred to as “front cylinder”). Can be considered.

  In particular, when the number of cylinders of the engine is large or when the engine speed increases, the interval between the combustion period of the previous cylinder and the combustion start timing of the predetermined cylinder is shortened. It can be considered that the influence on the detection result is increased. Here, with the technique described in Patent Document 1, it is difficult to sufficiently remove the influence of other cylinders (particularly the previous cylinder), and accuracy is sufficient when it is attempted to determine combustion fluctuation for each individual cylinder. It could not be said.

  The present invention has been made to solve the above-described problems, and an engine combustion fluctuation detection device capable of detecting combustion fluctuation for each cylinder of the engine with higher accuracy, and engine combustion fluctuation detection. It aims to provide a method.

  An engine combustion fluctuation detection apparatus according to the present invention includes a crank angle sensor that detects a rotational position of a crankshaft of an engine, and a change in time of the rotational position of the crankshaft detected by the crank angle sensor. In addition, an actual angular velocity acquisition means for obtaining the actual angular velocity of the crankshaft, an actual angular velocity of the predetermined cylinder obtained by the actual angular velocity acquisition means, an actual angular velocity of the previous cylinder whose ignition order is one order before the predetermined cylinder, and the Based on the degree of influence of the angular velocity of the previous cylinder on the angular velocity of the predetermined cylinder, the true angular velocity acquisition means for obtaining the true angular velocity of the predetermined cylinder when it is assumed that there is no combustion fluctuation for each cylinder, and the true angular velocity acquisition means Based on the true angular velocity of the predetermined cylinder, the actual angular velocity of the previous cylinder, and the degree of influence, a provisional cylinder provisional cylinder that takes into account the influence of the angular velocity of the previous cylinder on the true angular velocity of the predetermined cylinder is considered. From the temporary angular velocity obtaining means for obtaining the angular velocity, the difference obtaining means for obtaining the angular velocity difference between the actual angular velocity of the predetermined cylinder and the temporary angular velocity obtained by the temporary angular velocity obtaining means, and the angular velocity difference obtained by the difference obtaining means, Standard deviation acquisition means for obtaining a standard deviation value of the angular velocity difference in a predetermined cylinder is provided.

  The engine combustion fluctuation detecting method according to the present invention includes an actual angular velocity acquisition step for obtaining an actual angular velocity of the crankshaft for each cylinder of the engine based on a temporal change in the rotational position of the crankshaft detected by the crank angle sensor. And the actual angular velocity of the predetermined cylinder obtained in the actual angular velocity acquisition step, the actual angular velocity of the previous cylinder whose firing order is one order earlier than the predetermined cylinder, and the influence of the angular velocity of the previous cylinder on the angular velocity of the predetermined cylinder. Based on the true angular velocity acquisition step for obtaining the true angular velocity of the predetermined cylinder when it is assumed that there is no combustion fluctuation for each cylinder, the true angular velocity of the predetermined cylinder obtained in the true angular velocity acquisition step, the actual angular velocity of the previous cylinder, And a provisional angular velocity acquisition step for obtaining a provisional angular velocity of the predetermined cylinder in consideration of the influence of the angular velocity of the previous cylinder on the true angular velocity of the predetermined cylinder based on the degree of influence. A difference obtaining step for obtaining an angular velocity difference between the actual angular velocity of the predetermined cylinder and the provisional angular velocity obtained in the provisional angular velocity obtaining step, and an angular velocity difference obtained in the difference obtaining step from the angular velocity difference obtained in the difference obtaining step. A standard deviation obtaining step for obtaining a standard deviation value.

  According to the engine combustion fluctuation detection apparatus or the engine combustion fluctuation detection method according to the present invention, the angular velocity (true angular velocity) of a predetermined cylinder when it is assumed that there is no combustion variation for each cylinder is obtained. On the other hand, a provisional angular velocity in consideration of the influence of the angular velocity (that is, the combustion state) of the previous cylinder on the angular velocity of the predetermined cylinder is obtained. Then, a standard deviation value of a difference (angular velocity difference) between the actual angular velocity and the temporary angular velocity, that is, an index value of angular velocity fluctuation (combustion fluctuation) of a predetermined cylinder is obtained. Therefore, it is possible to obtain the angular velocity fluctuation (that is, combustion fluctuation) of the predetermined cylinder in consideration of the steady influence of the cylinder whose ignition order is one before, that is, by removing the combustion fluctuation. As a result, it is possible to detect the combustion fluctuation for each cylinder of the engine with higher accuracy.

ただし、Ｘは影響度であり、角速度ωの添字ｍは点火順序を示し、添字ｎはｎサイクル目の燃焼行程であることを示す。
仮角速度取得手段が、次式（２）に基づいて、所定気筒の仮の角速度を求めることが好ましい。

In the engine combustion fluctuation detecting apparatus according to the present invention, the true angular velocity acquisition means obtains the true angular velocity of the predetermined cylinder based on the following equation (1):

However, X is an influence degree, the subscript m of the angular velocity ω indicates the ignition order, and the subscript n indicates the combustion stroke of the nth cycle.
It is preferable that the provisional angular velocity acquisition means obtains a provisional angular velocity of the predetermined cylinder based on the following equation (2).

ただし、Ｘは影響度であり、角速度ωの添字ｍは点火順序を示し、添字ｎはｎサイクル目の燃焼行程であることを示す。
仮角速度取得ステップにおいて、次式（２）に基づいて、所定気筒の仮の角速度を求めることが好ましい。

In the engine combustion fluctuation detection method according to the present invention, in the true angular velocity acquisition step, the true angular velocity of the predetermined cylinder is obtained based on the following equation (1):

However, X is an influence degree, the subscript m of the angular velocity ω indicates the ignition order, and the subscript n indicates the combustion stroke of the nth cycle.
In the provisional angular velocity acquisition step, it is preferable to obtain a provisional angular velocity of the predetermined cylinder based on the following equation (2).

  In this way, based on the above formulas (1) and (2), the true angular velocity of the predetermined cylinder and the temporary velocity are assumed in consideration of the influence of the angular velocity of the previous cylinder (that is, the combustion state) on the angular velocity of the predetermined cylinder. Angular velocity can be calculated.

  In the engine combustion fluctuation detecting apparatus according to the present invention, it is preferable that the influence degree is set according to the engine speed.

  In the engine combustion fluctuation detection method according to the present invention, it is preferable that the influence degree is set according to the engine speed.

  As described above, since the interval between the combustion period of the previous cylinder and the combustion start timing of the predetermined cylinder becomes shorter as the engine speed increases, the combustion state (angular speed) of the previous cylinder becomes the detection result of the angular speed in the predetermined cylinder. It is possible that the impact will increase. In this case, since the influence degree is variably set according to the engine speed, the influence degree can be set appropriately.

  In the combustion fluctuation detecting apparatus for an engine according to the present invention, the actual angular velocity acquisition means is a predetermined section set between the ignition timing of a predetermined cylinder and the ignition timing of a cylinder one order after the predetermined cylinder. In this case, it is preferable to obtain the actual angular velocity of the predetermined cylinder.

  In the engine combustion fluctuation detection method according to the present invention, in the actual angular velocity acquisition step, the ignition timing of the predetermined cylinder is set between the ignition timing of the cylinder after the predetermined cylinder and the ignition sequence one after the predetermined cylinder. It is preferable to obtain the actual angular velocity of the predetermined cylinder in the predetermined section.

  In this way, by setting a section that includes the combustion period of the predetermined cylinder and does not include the combustion period of the rear cylinder (that is, a section that is not easily affected by the combustion state of the rear cylinder), the angular velocity for the predetermined cylinder is set. Can be detected. Therefore, it is possible to detect the combustion fluctuation of the predetermined cylinder with higher accuracy.

  According to the present invention, it is possible to detect the combustion fluctuation for each cylinder of the engine with higher accuracy.

It is a figure which shows the structure of the engine to which the combustion fluctuation detection apparatus of the engine which concerns on embodiment was applied. It is a flowchart which shows the process sequence of the combustion fluctuation | variation detection process by the combustion fluctuation | variation detection apparatus of the engine which concerns on embodiment. It is a figure which shows an example of the detection area which detects the angular velocity of each cylinder. It is a figure which shows an example of the angular velocity of the acquired crankshaft. It is a figure for demonstrating the calculation method of a true angular velocity, a temporary angular velocity angle, an angular velocity difference, and an angular velocity standard deviation.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the same element and the overlapping description is abbreviate | omitted.

  First, the configuration of the engine 10 to which the engine combustion fluctuation detection apparatus according to the embodiment is applied will be described with reference to FIG. FIG. 1 is a diagram showing a configuration of an engine 10 to which an engine combustion fluctuation detection device is applied.

  The engine 10 is, for example, a horizontally opposed four-cylinder gasoline engine. In the engine 10, air sucked from the air cleaner 16 is throttled by an electronically controlled throttle valve 13 provided in the intake pipe 15, passes through the intake manifold 11, and is sucked into each cylinder formed in the engine 10. Here, the amount of air taken in from the air cleaner 16 is detected by an air flow meter 14 disposed between the air cleaner 16 and the throttle valve 13. In addition, a vacuum sensor 30 for detecting the pressure (intake pipe negative pressure) in the intake manifold 11 is disposed in the collector portion (surge tank) constituting the intake manifold 11. Further, the throttle valve 13 is provided with a throttle opening sensor 31 that detects the opening of the throttle valve 13.

  In the vicinity of the intake port 22 communicating with the intake manifold 11, an injector 12 for injecting fuel is attached to each cylinder. The injector 12 injects the fuel sucked up by the feed pump and sent out from the fuel tank into the intake port 22. Further, a spark plug 17 that ignites the air-fuel mixture and an igniter built-in coil 21 that applies a high voltage to the spark plug 17 are attached to the cylinder head of each cylinder. In each cylinder of the engine 10, an air-fuel mixture of the sucked air and the fuel injected by the injector 12 is ignited by the spark plug 17 and burned. The exhaust gas after combustion is exhausted through the exhaust pipe 18.

An air-fuel ratio sensor 19 that outputs a signal corresponding to the oxygen concentration in the exhaust gas is attached to the exhaust pipe 18. As the air-fuel ratio sensor 19, an O ₂ sensor that detects the exhaust air-fuel ratio on and off is used. As the air-fuel ratio sensor 19, a linear air-fuel ratio sensor (LAF sensor) that can detect the exhaust air-fuel ratio linearly may be used.

Further, an exhaust purification catalyst 20 is disposed downstream of the air-fuel ratio sensor 19. The exhaust purification catalyst 20 is a three-way catalyst, which simultaneously oxidizes hydrocarbons (HC) and carbon monoxide (CO) in the exhaust gas and reduces nitrogen oxides (NOx) to produce harmful gas components in the exhaust gas. Is purified to harmless carbon dioxide (CO ₂ ), water vapor (H ₂ O) and nitrogen (N ₂ ).

  The exhaust pipe 18 is provided with an exhaust gas recirculation device (hereinafter referred to as an “EGR (Exhaust Gas Recirculation) device”) 40 that recirculates a part of the exhaust gas discharged from the engine 10 to the intake pipe 15 of the engine 10. It has been. The EGR device 40 includes an EGR pipe 41 that communicates the exhaust pipe 18 and the intake pipe 15 of the engine 10 and an EGR valve 42 that is disposed on the EGR pipe 41 and adjusts an exhaust gas recirculation amount (EGR flow rate). ing. The opening degree of the EGR valve 42 is controlled by an electronic control device 50 described later according to the operating state of the engine 10.

  In addition to the air flow meter 14, the air-fuel ratio sensor 19, the vacuum sensor 30, and the throttle opening sensor 31 described above, a cam angle sensor 32 for determining the cylinder of the engine 10 is attached in the vicinity of the camshaft of the engine 10. . A crank angle sensor 33 for detecting the rotational position of the crankshaft 10a is attached in the vicinity of the crankshaft 10a of the engine 10. Here, for example, a timing rotor 33a in which protrusions of 34 teeth with two teeth missing are formed at an interval of 10 ° is attached to the end of the crankshaft 10a, and the crank angle sensor 33 is connected to the timing rotor 33a. The rotational position of the crankshaft 10a is detected by detecting the presence or absence of the protrusion. As the cam angle sensor 32 and the crank angle sensor 33, for example, an electromagnetic pickup type is used.

  These sensors are connected to an electronic control unit (hereinafter referred to as “ECU”) 50. Further, the ECU 50 includes a water temperature sensor 34 that detects the temperature of the cooling water of the engine 10, an oil temperature sensor 35 that detects the temperature of the lubricating oil, and an accelerator pedal that detects the amount of depression of the accelerator pedal, that is, the opening of the accelerator pedal. Various sensors such as an opening sensor 36 are also connected.

  The ECU 50 includes a microprocessor that performs calculations, a ROM that stores programs for causing the microprocessor to execute each process, a RAM that stores various data such as calculation results, and a backup RAM in which the stored contents are held by a 12V battery. And an input / output I / F and the like. The ECU 50 also includes an injector driver that drives the injector 12, an output circuit that outputs an ignition signal, a motor driver that drives an electric motor that opens and closes the electronically controlled throttle valve 13, and the like.

  In the ECU 50, the cylinder is determined from the output of the cam angle sensor 32, and the engine speed is obtained from the output of the crank angle sensor 33. That is, the crank angle sensor 33 corresponds to the rotation speed detecting means described in the claims. Further, in the ECU 50, based on the detection signals input from the various sensors described above, various types such as the intake air amount, the intake pipe negative pressure, the accelerator pedal opening, the air-fuel ratio of the air-fuel mixture, and the water temperature and oil temperature of the engine 10 are provided. Information is acquired. Then, the ECU 50 comprehensively controls the engine 10 by controlling the fuel injection amount, the ignition timing, and various devices such as the throttle valve 13 based on the acquired various pieces of information.

  Further, the ECU 50 calculates the angular velocity (crank angular velocity) of the crankshaft 10a for each cylinder of the engine 10 from the crank angle signal acquired by the crank angle sensor 33, and detects the combustion fluctuation for each cylinder. Therefore, the ECU 50 functionally includes a real angular velocity acquisition unit 51, a true angular velocity acquisition unit 52, a provisional angular velocity acquisition unit 53, a difference acquisition unit 54, and a standard deviation acquisition unit 55. In the ECU 50, the program stored in the ROM is executed by the microprocessor, whereby the actual angular velocity acquisition unit 51, the true angular velocity acquisition unit 52, the provisional angular velocity acquisition unit 53, the difference acquisition unit 54, and the standard deviation acquisition unit 55. Each function is realized.

  The actual angular velocity acquisition unit 51 obtains the actual angular velocity of the crankshaft in a predetermined predetermined section for each cylinder of the engine 10 based on the temporal change in the rotational position of the crankshaft 10 a detected by the crank angle sensor 33. That is, the actual angular velocity acquisition unit 51 functions as an actual angular velocity acquisition unit described in the claims.

At that time, the actual angular velocity acquisition unit 51 determines the ignition timing of the predetermined cylinder (BTDC 40 ° in the example of FIG. 3) and the ignition timing of the cylinder one order after the predetermined cylinder (BTDC 40 in the example of FIG. 3). The actual angular velocity of the predetermined cylinder is obtained in a predetermined section set between Here, FIG. 3 shows an example of a detection section for detecting the actual angular velocity of each cylinder. As shown in FIG. 3, in the present embodiment, the actual angular velocity ω _{m, n} of each cylinder is set to be calculated in the section from BTDC 40 ° CA to BTDC 40 ° CA. The suffix m of the actual angular velocity ω indicates the ignition order, and n indicates the combustion stroke of the nth cycle.

Here, the ignition order of the engine 10 is in the order of the first cylinder (# 1), the third cylinder (# 3), the second cylinder (# 2), and the fourth cylinder (# 4). Therefore, for example, the angular velocity ω _{1, n} of the first cylinder (# 1) is in the section from BTDC 40 ° CA of the first cylinder (# 1) to BTDC 40 ° CA of the third cylinder (# 3) (that is, 1 (Based on the time required to rotate from BTDC 40 ° CA of the No. 1 cylinder (# 1) to BTDC 40 ° CA of the No. 3 cylinder (# 3)).

Here, an example of the actual angular velocity ω _{m, n} of the crankshaft 10a acquired by the actual angular velocity acquisition unit 51 is shown in FIG. In FIG. 4, the horizontal axis represents time, and the vertical axis represents the actual angular velocity ω _{m, n} (rad / s). The actual angular velocity of the crankshaft obtained by the actual angular velocity acquisition unit 51 is output to the actual angular velocity acquisition unit 52.

  The true angular velocity acquisition unit 52 is the actual angular velocity (average value) of the predetermined cylinder (m cylinder) obtained by the actual angular velocity acquisition unit 51, and the previous cylinder (m-1 cylinder) whose ignition order is one before the predetermined cylinder. When it is assumed that there is no combustion fluctuation for each cylinder based on the actual angular velocity (average value) of the cylinder and the degree of influence X of the angular velocity (combustion pressure / combustion state) of the previous cylinder on the angular velocity of the predetermined cylinder (that is, all cylinders) Is calculated as the true angular velocity (see FIG. 5). FIG. 5 is a diagram for explaining a method of calculating the true angular velocity, the temporary angular velocity angle, the angular velocity difference, and the velocity standard deviation. The true angular velocity acquisition unit 52 functions as a true angular velocity acquisition unit described in the claims.

  More specifically, first, the true angular velocity acquisition unit 52 acquires the influence degree X. Here, how to obtain the influence degree X will be described. The ROM or the like of the ECU 50 stores a map (influence map) that defines the relationship among the engine speed (rpm), the engine load (g / rev), and the influence degree X. The influence degree X is acquired by searching the influence degree map based on the above. The influence map data can be obtained, for example, by a desktop simulation or an engine bench test (actual machine experiment).

なお、真角速度取得部５２により求められた所定気筒（ｍ気筒）の真の角速度（平均値）は、仮角速度取得部５３に出力される。 And the true angular velocity acquisition part 52 calculates | requires the true angular velocity (average value) of a predetermined cylinder (m cylinder) based on following Formula (1).

The true angular velocity (average value) of the predetermined cylinder (m cylinder) obtained by the true angular velocity acquisition unit 52 is output to the provisional angular velocity acquisition unit 53.

  The provisional angular velocity acquisition unit 53 is based on the true angular velocity (average value) of the predetermined cylinder (m cylinder) obtained by the true angular velocity acquisition unit 52, the actual angular velocity of the previous cylinder (m-1 cylinder), and the influence degree X. The average value of the angular velocity of the predetermined cylinder in consideration of the influence of the angular velocity (combustion pressure / combustion state) of the previous cylinder with respect to the true angular velocity of the predetermined cylinder (that is, the actual Pi (combustion pressure) influence of the m-1 cylinder). The average value of the angular velocities of the received m cylinders) is obtained as a temporary angular velocity. The provisional angular velocity acquisition unit 53 functions as provisional angular velocity acquisition means described in the claims.

なお、仮角速度取得部５３により求められた所定気筒（ｍ気筒）の仮の角速度（平均値）は、差分取得部５４に出力される。 More specifically, the provisional angular velocity acquisition unit 53 obtains a provisional angular velocity (average value) of a predetermined cylinder (m cylinder) based on the following equation (2).

The provisional angular velocity (average value) of the predetermined cylinder (m cylinder) obtained by the provisional angular velocity acquisition unit 53 is output to the difference acquisition unit 54.

  The difference acquisition unit 54 uses the difference between the actual angular velocity of the predetermined cylinder (m cylinder) obtained by the actual angular velocity acquisition unit 51 and the provisional angular velocity (average value) obtained by the provisional angular velocity acquisition unit 53 as an angular velocity difference. Ask. That is, the difference acquisition unit 54 functions as a difference acquisition unit described in the claims.

なお、差分取得部５４により求められた所定気筒（ｍ気筒）の角速度差分Δω_ｍ，ｎは、標準偏差取得部５５に出力される。 More specifically, the difference acquisition unit 54 obtains the angular velocity difference Δω _{m, n} of the predetermined cylinder based on the following equation (3).

The angular velocity difference Δω _{m, n} of the predetermined cylinder (m cylinder) obtained by the difference obtaining unit 54 is output to the standard deviation obtaining unit 55.

  The standard deviation acquisition unit 55 uses the angular velocity difference obtained by the difference acquisition unit 54, and the standard deviation value (angular velocity standard deviation) of the angular velocity difference in the predetermined cylinder (m cylinder), that is, the combustion of the predetermined cylinder (m cylinder). Find an indicator of change. The standard deviation acquisition unit 55 functions as standard deviation acquisition means described in the claims.

More specifically, the standard deviation acquisition unit 55 obtains a standard deviation value (angular velocity standard deviation) σω of an angular velocity difference of a predetermined cylinder based on the following equation (4). Note that the number of data N is preferably set to about 500, for example.

  Next, the operation of the engine combustion fluctuation detection device will be described with reference to FIG. Here, FIG. 2 is a flowchart showing a processing procedure of combustion fluctuation detection processing by the engine combustion fluctuation detection device. This process is repeatedly executed in the ECU 50 at a predetermined timing.

  In step S100 (actual angular velocity acquisition step), the actual angular velocity of the crankshaft 10a in the predetermined section described above is determined for each cylinder of the engine 10 based on the temporal change in the rotational position of the crankshaft 10a detected by the crank angle sensor 33. Desired.

  Next, in step S102 (true angular velocity acquisition step), the actual angular velocity (average value) of the predetermined cylinder (m cylinder) obtained in step S100, the previous cylinder (m− Based on the actual angular velocity (average value) of one cylinder) and the influence degree X of the angular velocity of the preceding cylinder on the angular velocity of the predetermined cylinder, there is no combustion fluctuation for each cylinder (that is, all the cylinders combusted the same) ) Is obtained as the true angular velocity. Since the true angular velocity calculation method is as described above, detailed description thereof is omitted here.

  Subsequently, in step S104 (provisional angular velocity acquisition step), the true angular velocity (average value) of the predetermined cylinder (m cylinder) obtained in step S102, the actual angular velocity of the previous cylinder (m-1 cylinder), and the degree of influence. Based on X, an average value of the angular velocities of the predetermined cylinders in consideration of the influence of the angular velocities of the previous cylinders with respect to the true angular velocities of the predetermined cylinders is obtained as a temporary angular velocity. Note that the provisional angular velocity calculation method is as described above, and a detailed description thereof will be omitted here.

  In the subsequent step S106 (difference acquisition step), a difference (angular velocity difference) between the actual angular velocity of the predetermined cylinder (m cylinder) and the temporary angular velocity (average value) obtained in step S104 is obtained. Note that the calculation method of the angular velocity difference is as described above, and thus detailed description thereof is omitted here.

  In step S108 (standard deviation acquisition step), from the angular velocity difference obtained in step S106, the standard deviation value (angular velocity standard deviation) of the angular velocity difference in the predetermined cylinder (m cylinder) is determined for the predetermined cylinder (m cylinder). It is calculated as an index of combustion fluctuation. Since the method for calculating the angular velocity standard deviation is as described above, detailed description thereof is omitted here.

  As described above in detail, according to the present embodiment, the angular velocity (true angular velocity) of a predetermined cylinder (m cylinder) when it is assumed that there is no combustion fluctuation for each cylinder is obtained. On the other hand, a provisional angular velocity is obtained in consideration of the influence degree X of the angular velocity (that is, the combustion state) of the front cylinder (m−1 cylinder) on the angular velocity of the predetermined cylinder. Then, a standard deviation value of a difference (angular velocity difference) between the actual angular velocity and the temporary angular velocity, that is, an index value of angular velocity fluctuation (combustion fluctuation) of a predetermined cylinder is obtained. Therefore, it is possible to obtain the angular velocity fluctuation (that is, combustion fluctuation) of the predetermined cylinder in consideration of the steady influence of the cylinder whose ignition order is one before, that is, by removing the combustion fluctuation. As a result, the combustion fluctuation for each cylinder of the engine 10 can be detected with higher accuracy.

  Further, according to the present embodiment, the influence degree is set to X, and the above formulas (1) and (2) are used, whereby the angular speed of the front cylinder (m-1 cylinder) with respect to the angular speed of the predetermined cylinder (m cylinder). In consideration of the influence degree, the true angular velocity and the temporary angular velocity of the predetermined cylinder can be calculated.

  As described above, as the engine speed increases, the interval between the combustion period of the front cylinder (m-1 cylinder) and the combustion start timing of the predetermined cylinder (m cylinder) becomes shorter. ) May have a large influence on the detection result of the angular velocity in the predetermined cylinder. According to the present embodiment, the influence degree X is variably set according to the rotational speed of the engine 10, and therefore the influence degree X can be set appropriately.

  Further, according to the present embodiment, the ignition timing (BTDC 40 °) of a predetermined cylinder (m cylinder) and the ignition timing (BTDC 40 °) of a cylinder (m + 1 cylinder) that is one after the predetermined cylinder in ignition sequence. The actual angular velocity of the predetermined cylinder is obtained in a predetermined section set between the two. Therefore, it is possible to set an interval including the combustion period of the predetermined cylinder and not including the combustion period of the rear cylinder (that is, a section that is not easily influenced by the combustion state of the rear cylinder), and to detect the angular velocity with respect to the predetermined cylinder. it can. Therefore, it is possible to detect the combustion fluctuation of the predetermined cylinder with higher accuracy.

  Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be made. For example, in the above embodiment, the influence degree X of the angular speed of the previous cylinder with respect to the angular speed of the predetermined cylinder is obtained from the engine speed and the engine load by using the influence degree map, but is obtained only from the engine speed. Also good.

In the above embodiment, the angular velocity difference of the predetermined cylinder (m cylinder) is calculated based on the above equation (3) as the difference between the actual angular velocity and the provisional angular velocity (average value). It is good also as a structure which calculates directly based on following Formula (5), without calculating | requiring.

  In the embodiment described above, a four-cylinder engine has been described as an example of the engine 10, but the engine 10 is not limited to a four-cylinder engine. The section for detecting the angular velocity of the crankshaft 10 is not limited to the above embodiment.

  In the above embodiment, the case where the present invention is applied to a port injection type engine has been described as an example. However, the present invention is applied to an in-cylinder injection type engine and an engine that combines in-cylinder injection and port injection. Can also be applied.

DESCRIPTION OF SYMBOLS 10 Engine 10a Crankshaft 13 Electronically controlled throttle valve 17 Spark plug 21 Igniter built-in coil 31 Throttle opening sensor 32 Cam angle sensor 33 Crank angle sensor 33a Timing rotor 34 Water temperature sensor 35 Oil temperature sensor 36 Accelerator pedal opening sensor 50 ECU
51 Real angular velocity acquisition unit 52 True angular velocity acquisition unit 53 Temporary angular velocity acquisition unit 54 Difference acquisition unit 55 Standard deviation acquisition unit

Claims (8)

A crank angle sensor for detecting the rotational position of the crankshaft of the engine;
An actual angular velocity obtaining means for obtaining an actual angular velocity of the crankshaft for each cylinder of the engine based on a change in the rotational position of the crankshaft detected by the crank angle sensor;
The actual angular velocity of the predetermined cylinder obtained by the actual angular velocity acquisition means, the actual angular velocity of the previous cylinder whose firing order is one order before the predetermined cylinder, and the degree of influence of the angular velocity of the previous cylinder on the angular velocity of the predetermined cylinder Based on a true angular velocity obtaining means for obtaining a true angular velocity of the predetermined cylinder when it is assumed that there is no combustion fluctuation for each cylinder,
Based on the true angular velocity of the predetermined cylinder obtained by the true angular velocity acquisition means, the actual angular velocity of the front cylinder, and the influence degree, the influence of the angular velocity of the front cylinder on the true angular velocity of the predetermined cylinder. Provisional angular velocity acquisition means for obtaining a provisional angular velocity of the predetermined cylinder in consideration of
Difference obtaining means for obtaining an angular velocity difference between the actual angular velocity of the predetermined cylinder and the provisional angular velocity obtained by the provisional angular velocity obtaining means;
An engine combustion fluctuation detecting device comprising: standard deviation obtaining means for obtaining a standard deviation value of the angular velocity difference in the predetermined cylinder from the angular velocity difference obtained by the difference obtaining means. The true angular velocity acquisition means obtains a true angular velocity of the predetermined cylinder based on the following equation (1):

However, X is an influence degree, the subscript m of the angular velocity ω indicates the ignition order, and the subscript n indicates the combustion stroke of the nth cycle.
2. The engine combustion fluctuation detecting apparatus according to claim 1, wherein the provisional angular velocity acquisition unit obtains a provisional angular velocity of the predetermined cylinder based on the following equation (2).

  The engine combustion fluctuation detection device according to claim 1 or 2, wherein the influence degree is set according to a rotational speed of the engine.   The actual angular velocity acquisition means obtains the actual angular velocity of the predetermined cylinder in a predetermined section set between the ignition timing of the predetermined cylinder and the ignition timing of the cylinder whose ignition order is one order after the predetermined cylinder. The engine combustion fluctuation detection device according to any one of claims 1 to 3, wherein An actual angular velocity acquisition step for obtaining an actual angular velocity of the crankshaft for each cylinder of the engine based on a temporal change in the rotational position of the crankshaft detected by the crank angle sensor;
The actual angular velocity of the predetermined cylinder obtained in the actual angular velocity acquisition step, the actual angular velocity of the previous cylinder whose firing order is one order earlier than the predetermined cylinder, and the degree of influence of the angular velocity of the previous cylinder on the angular velocity of the predetermined cylinder A true angular velocity acquisition step for obtaining a true angular velocity of the predetermined cylinder when it is assumed that there is no combustion fluctuation for each cylinder,
Based on the true angular velocity of the predetermined cylinder, the actual angular velocity of the previous cylinder, and the influence degree obtained in the true angular velocity acquisition step, the influence of the angular velocity of the front cylinder on the true angular velocity of the predetermined cylinder. A provisional angular velocity acquisition step for obtaining a provisional angular velocity of the predetermined cylinder in consideration of
A difference obtaining step for obtaining an angular velocity difference between the actual angular velocity of the predetermined cylinder and the provisional angular velocity obtained in the provisional angular velocity obtaining step;
And a standard deviation obtaining step for obtaining a standard deviation value of the angular velocity difference in the predetermined cylinder from the angular velocity difference obtained in the difference obtaining step. In the true angular velocity acquisition step, the true angular velocity of the predetermined cylinder is obtained based on the following equation (1):

However, X is an influence degree, the subscript m of the angular velocity ω indicates the ignition order, and the subscript n indicates the combustion stroke of the nth cycle.
6. The engine combustion fluctuation detection method according to claim 5, wherein, in the provisional angular velocity acquisition step, a provisional angular velocity of the predetermined cylinder is obtained based on the following equation (2).

  The engine combustion fluctuation detection method according to claim 5 or 6, wherein the influence degree is set in accordance with a rotational speed of the engine. In the actual angular velocity acquisition step, the actual angular velocity of the predetermined cylinder is obtained in a predetermined section set between the ignition timing of the predetermined cylinder and the ignition timing of the cylinder that is one after the predetermined cylinder. The method for detecting combustion fluctuations in an engine according to any one of claims 5 to 7.

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