Engine control device

Abstract

Disclosed is an engine control device (10) that reduces knocking by controlling an ignition timing (θ) of an engine (1), and that is provided with a first determination unit (11), a second determination unit (12), and a selection unit (13). The first determination unit (11) calculates knock occurrence probability (P) and likelihood (L) on the basis of the number of times of ignition (n) and the number of times of knocking (k), and determines whether or not it is necessary to change the ignition timing (θ), on the basis of the magnitude of the likelihood (L). The second determination unit (12) calculates knock intensity (S) or knock occurrence probability (P), and determines whether or not it is necessary to change the ignition timing (θ), on the basis of the knock intensity (S) or the knock occurrence probability (P). The selection unit (13) selects the determination result of one of the first determination unit (11) and the second determination unit (12) on the basis of a predetermined condition.

Description

Engine control unit

[0001] The present invention relates to an engine control device that suppresses engine knocking by controlling ignition timing.

[0002] A known engine ignition timing control method adjusts the ignition timing so that output torque is maximized within a range of ignition timing that is unlikely to cause knock. For example, a control device is known that calculates the ignition timing that maximizes output torque (Minimum Advance for Best Torque (MBT)) and the knock limit ignition timing (the most advanced ignition timing at which knock does not occur), and controls the ignition timing using the retarded value of these (see Patent Document 1).

[0003] On the other hand, knock limit ignition timing easily fluctuates due to factors such as the distribution of the fuel mixture in the cylinder, temperature distribution, and pressure distribution. Therefore, it is difficult to accurately calculate knock limit ignition timing. For example, it is difficult to continue operating the engine while completely suppressing knock. Therefore, a control method has been proposed in which the ignition timing is temporarily retarded when a relatively small amount of knock occurs, and then gradually advanced back to the advanced position. This method ensures output torque while suppressing the increase in knock. This type of control is called knock retard control.

[0004] Japanese Patent Application Publication No. 2018-59437

[0005] However, knock retard control tends to retard the ignition timing more than the actual knock limit ignition timing, which can result in poor fuel economy. While reducing the amount of retard in knock retard control or increasing the speed at which the ignition timing is returned in the advance direction (the amount of advance per combustion cycle) can be considered as a solution to this problem, there are concerns that these approaches may actually make knock more likely to occur.

[0006] One of the objectives of the present invention, which was devised in light of the above-mentioned problems, is to provide an engine control device that can improve fuel economy while suppressing knocking. However, in addition to this objective, another objective of the present invention is to achieve effects derived from the configurations shown in the "Description of Embodiments" below, which are not obtainable with conventional technologies.

[0007] The disclosed engine control device can be realized as the following disclosed aspects (application examples) and solves at least part of the above-mentioned problems. Each of the aspects from aspect 2 onwards is an aspect that can be selected as an additional aspect, and each of the aspects from aspect 2 onwards is an aspect that can be omitted. None of the aspects from aspect 2 onwards is disclosed as an aspect or configuration that is essential to the present invention.

[0008] Aspect 1. The disclosed engine control device suppresses knock by controlling the ignition timing of an engine, and includes a first determination unit, a second determination unit, and a selection unit. The first determination unit calculates a knock occurrence probability and a likelihood of the knock occurrence probability based on the number of ignitions and the number of knocks, and determines whether or not the ignition timing needs to be changed based on the magnitude of the likelihood. The second determination unit calculates a knock intensity or the knock occurrence probability, and determines whether or not the ignition timing needs to be changed based on the knock intensity or the knock occurrence probability. The selection unit selects the determination result of either the first determination unit or the second determination unit based on a predetermined condition.

[0009] Aspect 2. In an aspect including Aspect 1 described above, it is preferable that the first determination unit calculates a target likelihood based on the number of ignitions, the number of knocks, and a target knock occurrence probability, calculates a likelihood ratio that is a ratio of the target likelihood to the likelihood, and determines that the ignition timing needs to be changed when the likelihood ratio is equal to or less than a predetermined value.

[0010] Aspect 3. With regard to aspects including Aspect 1 above, it is preferable that the number of ignitions and the number of knocks are the numbers in a most recent first predetermined period. Aspect 4. With regard to aspects including Aspect 3 above, it is preferable that the selection unit selects the determination result of the first determination unit when a first condition is met, that is, the knock occurrence probability in a most recent second predetermined period that is shorter than the first predetermined period is equal to or less than a threshold, and selects the determination result of the second determination unit when the first condition is not met.

[0011] Aspect 5. With respect to aspects including Aspect 1 above, it is preferable that the selection unit selects the determination result of the first determination unit when a second condition that the engine is in steady operation is satisfied, and selects the determination result of the second determination unit when the second condition is not satisfied. Aspect 6. With respect to aspects including Aspect 5 above, it is preferable that the likelihood value is reset when the engine changes between steady operation and non-steady operation.

[0012] Aspect 7. With regard to aspects including Aspect 1 above, it is preferable that the selection unit selects the determination result of the first determination unit when a third condition is met, that is, when the knock intensity is less than a predetermined intensity, and selects the determination result of the second determination unit when the third condition is not met. Aspect 8. With regard to aspects including Aspect 1 above, it is preferable that a base characteristic map representing a relationship between the ignition timing and the knock probability is provided, and that the ignition timing is controlled so that the knock probability matches a target knock probability calculated from the base characteristic map.

[0013] According to the disclosed engine control device, by selectively using the determination results of the first determination unit and the second determination unit, the control accuracy of the ignition timing can be improved, and fuel economy can be improved while suppressing knocking.

[0014] 1 is a diagram showing the configuration of an engine control device as an embodiment and an engine to which the same is applied; FIG. 2 is a base characteristic map showing the relationship between ignition timing θ and knock occurrence probability P stored in the engine control device; FIG. 3 is a flowchart showing an example of a control procedure by the engine control device; FIG. 4 is a flowchart showing an example of a control procedure by the engine control device; FIG. 5 is a graph for explaining the control content by the engine control device, where (A) represents knock intensity S, (B) represents the number of knocks k, (C) represents the number of ignitions n, (D) represents knock occurrence probability P, (E) represents likelihood ratio R, and (F) represents ignition timing θ; and FIG. 6 is a graph for explaining the control content by the engine control device, where (A) represents knock intensity S, (B) represents the number of knocks k, (C) represents the number of ignitions n, (D) represents knock occurrence probability P, and (E) represents short-term knock occurrence probability P. Ｓ , (F) represents likelihood ratio R, and (G) represents ignition timing θ. This is a graph for explaining the control content by the engine control device, in which (A) represents knock intensity S, (B) represents the number of knocks k, (C) represents the number of ignitions n, (D) represents knock occurrence probability P, (E) represents engine torque, (F) represents likelihood ratio R, and (G) represents ignition timing θ.

[0015] [1. Configuration] Fig. 1 is a diagram showing the configuration of an engine control device 10 according to an embodiment and an engine 1 to which the engine control device 10 is applied. The engine 1 is a spark-ignition internal combustion engine equipped with spark plugs 2 in its cylinders, and can be installed in, for example, automobiles, ships, driving force generating devices, power generating devices, etc. The engine 1 shown in Fig. 1 is installed in an automobile. The ignition timing of the spark plugs 2 is controlled by the engine control device 10. The engine control device 10 is an electronic control device equipped with a processor and memory, and has a function of suppressing knock by controlling the ignition timing θ of the engine 1. The contents of the control performed by the engine control device 10 are recorded and saved in memory, for example, in the form of a program.

[0016] The engine control device 10 activates the spark plug 2 at an ignition timing θ that corresponds to, for example, the operating state, fuel injection method, combustion method, fuel injection amount, combustion conditions, vehicle running state, etc. of the engine 1. There are no restrictions on the number of cylinders, number of strokes, fuel injection method, or combustion method of the engine 1. The fuel injection device of the engine 1 is provided in at least one location, for example, the intake passage, the intake port, or inside the cylinder, and may be provided in multiple locations.

[0017] The engine 1 is provided with a knock sensor 3, a water temperature sensor 4, a crank angle sensor 5, and an air flow sensor 6 as sensors that detect information related to the operating state of the engine 1. The knock sensor 3 detects the occurrence and intensity of knock (knocking), and the water temperature sensor 4 detects the temperature of the engine coolant. The crank angle sensor 5 detects the crank angle and crank angular velocity (engine speed), and the air flow sensor 6 detects the intake air volume. In this embodiment, an accelerator position sensor 7 and a vehicle speed sensor 8 are connected to the engine control device 10. The accelerator position sensor 7 detects the accelerator position of the vehicle in which the engine 1 is mounted, and the vehicle speed sensor 8 detects the vehicle speed. Information detected by each of the sensors 3 to 8 is input to the engine control device 10.

[0018] The engine control device 10 includes a first determination unit 11, a second determination unit 12, a selection unit 13, and a control unit 14. These elements represent the functions of the engine control device 10 and can be programmed as software that is recorded and stored in, for example, a memory or auxiliary storage device within the engine control device 10. They can also be realized as an electronic circuit (hardware) corresponding to the software. Alternatively, they can be realized as a system that combines software and hardware.

[0019] Both the first determination unit 11 and the second determination unit 12 determine whether or not a change in the ignition timing θ is necessary. The second determination unit 12 is a determination unit that makes a determination similar to that of conventional knock retard control. In contrast, the first determination unit 11 is a determination unit that makes a determination different from that of conventional knock retard control. The first determination unit 11 and the second determination unit 12 make their determinations independently of each other. Thereafter, the selection unit 13 selects the determination result of either the first determination unit 11 or the second determination unit 12 based on predetermined conditions. The determination result selected by the selection unit 13 is transmitted to the control unit 14. The control unit 14 controls the ignition timing θ based on the determination result.

[0020] The second determination unit 12 detects or calculates the presence or absence of knock, the knock intensity S, or the knock probability P, and determines whether or not the ignition timing θ needs to be changed. The second determination unit 12 may make a determination based only on the presence or absence of knock, may make a determination based only on the knock intensity S, may make a determination based only on the knock probability P, or may make a determination based on both the knock intensity S and the knock probability P. Known methods can be applied to setting specific determination conditions and the amount of change in the ignition timing θ.

[0021] A determination method based on the occurrence of knocking will be described as an example of the determination method used by the second determination unit 12. When the knock sensor 3 detects the occurrence of knocking, the second determination unit 12 retards the ignition timing θ by a predetermined amount (in the retard direction), and when the knocking is not detected, the second determination unit 12 gradually advances the ignition timing θ.

[0022] As an example of another determination method in the second determination unit 12, a determination method based on the knock intensity S will be described. When the knock intensity S detected by the knock sensor 3 is equal to or greater than a first intensity, the second determination unit 12 determines that the ignition timing θ needs to be changed in the retard direction (retard direction). When the knock intensity S is smaller than the first intensity, the second determination unit 12 determines that the ignition timing θ needs to be changed in the advance direction (advance direction).

[0023] As an example of another determination method in the second determination unit 12, a determination method based on the knock occurrence probability P will be described. The second determination unit 12 calculates the knock occurrence probability P (= k / n) based on the number of ignitions n of the engine 1 and the number of knocks k counted (counted up) from the detection result of the knock sensor 3. The period during which the number of ignitions n and the number of knocks k are counted may be the period from the start of starting the engine 1 to the present, or may be the most recent first predetermined period (for example, the number of ignitions n up to several hundred times before the present or up to several tens of seconds before the present).

[0024] Furthermore, the second determination unit 12 determines that the ignition timing θ needs to be retarded when the knock occurrence probability P is equal to or greater than the first probability, and determines that the ignition timing θ does not need to be retarded when the knock occurrence probability P is smaller than the first probability.

[0025] The first determination unit 11 calculates a knock probability P (= k / n) based on the number of ignitions n of the engine 1 and the number of knocks k counted from the detection result of the knock sensor 3, and also calculates a likelihood L of the knock probability P. The first determination unit 11 determines whether or not the ignition timing θ needs to be changed based on the magnitude of the likelihood L. The likelihood L is a parameter corresponding to the degree of certainty or reliability of the value of the knock probability P. In this embodiment, a normalized likelihood L is used. The likelihood L can be normalized by dividing the likelihood L at the current knock probability P by the integral value of the likelihood L from when the knock probability P is 0 to when it is 1. As the number of ignitions n increases, the likelihood L is less likely to take a small value (it is easier to obtain high reliability). The calculation formula for the likelihood L is shown below.

[0026]

[0027] As an example of the determination method in the first determination unit 11, a determination method based on the magnitude of the likelihood L will be described. The first determination unit 11 determines that a change in the ignition timing θ is required when the magnitude of the likelihood L is equal to or greater than a first likelihood. The direction in which the ignition timing θ is to be changed (retarded or advanced) is determined based on the knock occurrence probability P at the time when the magnitude of the likelihood L is equal to or greater than the first likelihood. Furthermore, when the magnitude of the likelihood L is less than the first likelihood, the first determination unit 11 determines that a change in the ignition timing θ is not required (the ignition timing θ does not need to be moved).

[0028] As an example of another determination method in the first determination unit 11, a determination method based on a likelihood ratio R will be described. ｔｇｔ and the target likelihood L for likelihood L ｔｇｔ The likelihood ratio R is calculated as the ratio of the target likelihood L ｔｇｔ is the number of ignitions n, the number of knocks k, and the target knock occurrence probability P ｔｇｔ The target knock occurrence probability P ｔｇｔ is the ideal knock probability P in the current operating state of the engine 1, and is preferably a value greater than 0. In other words, if the knock probability P is 0, it means that there is a possibility that the ignition timing θ can be advanced a little more, so it cannot be said that the ignition timing θ is ideal. On the other hand, if the knock probability P is too large, it may lead to damage to the engine 1. Therefore, the target knock probability P ｔｇｔ is preferably set to a value that is neither too large nor too small. ｔｇｔ may be a fixed value set in advance, or may be a variable value calculated according to the actual ignition timing θ of the engine 1, the engine speed, and the engine load. ｔｇｔ The formula for calculating the likelihood ratio R is shown below.

[0029]

[0030] The value of the likelihood ratio R is determined based on whether the actual knock occurrence probability P is approximately equal to the target knock occurrence probability P ｔｇｔ If the operating condition is equal to the target knock occurrence probability P, the knock occurrence probability P is maintained at a value close to 1. ｔｇｔWhen the engine is in an operating state different from the above, the value of the likelihood ratio R tends to decrease as the number of ignitions n increases. Also, the rate at which the likelihood ratio R decreases decreases as the number of ignitions n increases.

[0031] 2 shows a base characteristic map 15 that defines a graph showing the relationship between the ignition timing θ of the engine 1 and the knock probability P. The engine control device 10 (control unit 14) of this embodiment stores the base characteristic map 15 for the engine 1 in ideal conditions (steady operation, predetermined temperature, standard atmospheric pressure, intake, exhaust sensor activated, new injector, etc.) that were created through tests and experiments conducted in advance. The X-axis of the graph in FIG. 2 represents the ignition timing θ as a crank angle [° CA BTDC] in the retard direction from top dead center, with the right side of the graph representing the advance side and the left side representing the retard side. Target knock probability P ｔｇｔ is set in accordance with the engine speed and / or engine load, and the base ignition timing θ , which is the ignition timing described later, is set based on the graph of this base characteristic map 15. Ｂ It should be noted that a plurality of base characteristic maps 15 may be stored in accordance with the target torque, intake air amount, fuel injection amount, etc. of the engine 1.

[0032] The first determination unit 11 determines whether the likelihood ratio R is a predetermined value R ｔｈ When the target likelihood L ｔｇｔ When the likelihood ratio R becomes sufficiently large relative to the predetermined value R, it is determined that "the number of ignitions n is sufficient and the ignition timing θ is inappropriate," and it is determined that the ignition timing θ needs to be changed. ｔｈ For example, the knock occurrence probability P is determined based on the knock occurrence probability P at the time when the knock occurrence probability P is equal to or less than the target knock occurrence probability P ｔｇｔ On the other hand, if the knock occurrence probability P is higher than the target knock occurrence probability P ｔｇｔ If it is lower than the predetermined value, it is determined that the ignition timing θ needs to be advanced.

[0033] The amount of change (retard amount, advance amount) of the ignition timing θ may be a fixed value set in advance, or may be a variable value calculated according to the knock occurrence probability P. In addition, the knock occurrence probability P is calculated from the graph of the base characteristic map 15 as a target knock occurrence probability P. ｔｇｔ For example, in the graph of the base characteristic map 15 shown in FIG. 2, the Y coordinate corresponds to the current knock occurrence probability P Ａ The point corresponding to the ignition timing θ is searched (calculated) and the X coordinate of that point is calculated. Ａ In addition, the target knock occurrence probability P ｔｇｔ The ignition timing corresponding to the base ignition timing θ Ｂ When controlling the ignition timing, the target knock occurrence probability P ｔｇｔ The ignition timing corresponding to the base ignition timing θ Ｂ The ignition timing θ is set to

[0034] Here, the current ignition timing θ ｒｅａｌ (= base ignition timing θ Ｂ ) the current knock occurrence probability P Ａ is the target knock occurrence probability P ｔｇｔ If it is higher than the calculated ignition timing θ Ａ is the current ignition timing θ ｒｅａｌ Since the current knock occurrence probability P Ａ The target knock occurrence probability P ｔｇｔ To approach this, the ignition timing θ must be retarded. Ｂ and calculated ignition timing θ Ａ A retard amount Δθ corresponding to the difference between these values ​​is set, and the ignition timing θ is shifted in the retard direction by the retard amount Δθ.

[0035] In addition, the current knock occurrence probability P Ａ is the target knock occurrence probability P ｔｇｔ If it is lower than the calculated ignition timing θ Ａ is the base ignition timing θ Ｂ Since the current knock occurrence probability PＡ The target knock occurrence probability P ｔｇｔ To get closer to this, it is necessary to advance the ignition timing θ. Ｂ and calculated ignition timing θ Ａ An advance amount Δθ corresponding to the difference between these values ​​is set, and the ignition timing θ is advanced by the advance amount Δθ.

[0036] Similarly, after the ignition timing is moved, the knock occurrence probability P Ａ Calculated ignition timing θ corresponding to Ａ Calculate the base ignition timing θ Ｂ and calculated ignition timing θ Ａ The ignition timing θ is moved by the amount of movement Δθ (retard amount Δθ, advance amount Δθ) based on the difference between the base ignition timing θ and the base ignition timing θ. Every time the first determination unit 11 determines that the ignition timing θ needs to be changed, the ignition timing is updated by the above method. The latest ignition timing is the base ignition timing θ. Ｂ is a value obtained by accumulating the amount of movement Δθ of the ignition timing θ up to now (the amount of movement Δθ is a positive value on the advance side and a negative value on the retard side).

[0037] The selection unit 13 selects the determination result of either the first determination unit 11 or the second determination unit 12 based on a predetermined condition. For example, the selection unit 13 can select the determination result of the first determination unit 11 when a first condition shown below is satisfied, and can select the determination result of the second determination unit 12 when the first condition is not satisfied. First condition: short-term knock occurrence probability P in a second predetermined period that is shorter than the first predetermined period Ｓ is the threshold P ｔｈ It must be less than or equal to:

[0038] The first predetermined period refers to the most recent target period that the first determination unit 11 refers to when calculating the knock occurrence probability P, and the second predetermined period refers to the most recent target period that the second determination unit 12 refers to when calculating the short knock occurrence probability P. Ｓ The second predetermined period is, for example, the number of ignitions n up to several tens of times before the present or the number of seconds before the present. Ｓ The number of ignitions in the second predetermined period is set to n Ｓ Then, the probability of short-term knock occurrence P ＳHa K Ｓ / n Ｓ The short-term knock occurrence probability P calculated by the second determination unit 12 is expressed as follows: Ｓ increases when knocks occur frequently in a short span of time, and decreases in a relatively short time when no knocks occur. By selection based on the first condition, when continuous knocks occur in a short period of time (frequent knocks in a short period of time, continuous knocks, intermittent knocks), the determination result of the second determination unit 12 is adopted in preference to the determination result of the first determination unit 11.

[0039] The selection unit 13 may select the determination result of the first determination unit 11 when, for example, a second condition shown below is satisfied, and may select the determination result of the second determination unit 12 when the second condition is not satisfied. Second condition: The engine 1 is in steady operation. Whether the engine 1 is in a steady state may be determined based on fluctuations in the engine output, torque, engine speed, etc., or on fluctuations in the intake air volume, accelerator opening, vehicle speed, etc. When the selection based on the second condition changes the operating state of the engine 1 (when the engine 1 becomes unsteady), the determination result of the second determination unit 12 is adopted in preference to the determination result of the first determination unit 11. Note that when the operating state of the engine 1 switches between steady operation and unsteady operation, it is preferable that the first determination unit 11 resets the value of the likelihood L, and it is also preferable that the counts of the number of ignitions n and the number of knocks k are reset. Therefore, when the second condition is not satisfied, it is preferable that the second determination unit 12 implements a determination method based on the occurrence or non-occurrence of knock or the knock intensity S.

[0040] The selection unit 13 may select the determination result of the first determination unit 11 when a third condition, for example, as shown below, is satisfied, and may select the determination result of the second determination unit 12 when the third condition is not satisfied. ｔｈ The knock intensity S here may be the value detected by the knock sensor 3 as is, or may be corrected based on the output, torque, engine speed, etc. of the engine 1. When a strong knock occurs, the selection based on the third condition causes the determination result of the second determination unit 12 to be adopted with priority over the determination result of the first determination unit 11.

[0041] The predetermined conditions referred to by the selection unit 13 when selecting a determination result include conditions other than the first, second, and third conditions. For example, one determination result may be selected based on a user selection (the operation state of a switch operated by the user or the setting state of a control setting item), or one determination result may be selected based on the continuous operation time of the engine 1, the running state of the vehicle, or the like. Furthermore, the first, second, and third conditions may be combined as shown in the flowchart of FIG. 5 , which will be described later. When multiple conditions are combined, for example, the determination result of the first determination unit 11 may be selected when all of the conditions are met, and the determination result of the second determination unit 12 may be selected when any of the conditions is not met.

[0042] The control unit 14 controls the ignition timing θ based on the determination result selected by the selection unit 13. When the determination result selected by the selection unit 13 is the determination result by the first determination unit 11, the control unit 14 controls the ignition timing θ by setting the retard amount or advance amount of the ignition timing θ based on the knock occurrence probability P. For example, when the knock occurrence probability P is equal to or greater than the target knock occurrence probability P, ｔｇｔ If the knock occurrence probability P is higher than the target knock occurrence probability P ｔｇｔ The retard amount is set so that the ignition timing θ is moved in the retard direction so that the knock occurrence probability P approaches the target knock occurrence probability P ｔｇｔ If the knock occurrence probability P is lower than the target knock occurrence probability P ｔｇｔ The advance amount is set so that the ignition timing θ approaches the value θ, and the ignition timing θ is advanced.

[0043] If the determination result selected by the selection unit 13 is the determination result by the second determination unit 12, the control unit 14 may control the ignition timing θ based on the knock intensity S, or may control the ignition timing θ based on the knock occurrence probability P. Alternatively, control similar to conventional knock retard control may be performed. For example, the ignition timing θ may be temporarily retarded by a preset retard amount, and then the ignition timing θ may be gradually returned in the advance direction.

[0044] 3, 4, and 5 are flowcharts showing examples of control procedures by the engine control device 10. Fig. 3 is a flowchart of control in which the determination result of either the first determination unit 11 or the second determination unit 12 is selected based on a predetermined condition. Fig. 4 is a flowchart of control in which the determination result is selected based on a first condition, and Fig. 5 is a flowchart of control in which the determination result is selected based on a second condition and a third condition. The controls according to these flowcharts are repeatedly executed for each cylinder at a predetermined cycle while the engine 1 is operating.

[0045] The flowchart in Figure 3 will now be described. In step A1, the number of ignitions n is counted up, and in step A2, it is determined whether or not a knock has been detected. At this time, the knock intensity S is also obtained. If a knock is not detected, the control for this cycle ends. If a knock is detected, the process proceeds to step A3, where the number of knocks k is counted up. If a knock is not detected in step A2, step A3 is skipped (the number of knocks k is not counted up) and the process proceeds to step A4. In step A4, a knock occurrence probability P is calculated from the number of ignitions n and the number of knocks k, and the likelihood L of the knock occurrence probability P is also calculated.

[0046] In the following step A5, the first determination unit 11 determines whether or not it is necessary to change the ignition timing θ based on the magnitude of the likelihood L. Meanwhile, in step A6, the second determination unit 12 determines whether or not it is necessary to change the ignition timing θ based on the knock intensity S or the knock occurrence probability P. In step A7, the selection unit 13 selects either the determination result of the first determination unit 11 or the second determination unit 12 based on a predetermined condition. In the subsequent step A8, the ignition timing θ is controlled based on the determination result selected in step A7.

[0047] The flowchart of FIG. 4 will be described. In the flowchart of FIG. 4, steps A1 to A3 and A8 are the same as those in the flowchart of FIG. 3. In step B1 following step A3, the first determination unit 11 calculates the knock occurrence probability P in the most recent first predetermined period. That is, the knock occurrence probability P is calculated based on the number of ignitions n and the number of knocks k from before the first predetermined period to the present. In step B2, the first determination unit 11 calculates the likelihood L of this knock occurrence probability P, and also calculates the target likelihood L ｔｇｔ and the likelihood ratio R. In step B3, the first determination unit 11 determines based on the likelihood ratio R whether or not the ignition timing θ needs to be changed.

[0048] On the other hand, in step B4, the second determination unit 12 determines the short-term knock occurrence probability P Ｓ That is, the short-term knock occurrence probability P is calculated based on the number of ignitions n and the number of knocks k from before the second predetermined period to the present. Ｓ The second predetermined period is shorter than the first predetermined period. In the next step B5, the second determination unit 12 calculates the short knock occurrence probability P Ｓ In step B6, the selection unit 13 determines whether or not the ignition timing θ needs to be changed based on the short-term knock occurrence probability P Ｓ is the threshold P ｔｈ It is determined whether or not the first condition is satisfied.

[0049] If the condition of step B6 is met, the process proceeds to step B7, where the selection unit 13 selects the determination result of the first determination unit 11. If the condition of step B6 is not met, the process proceeds to step B8, where the selection unit 13 selects the determination result of the second determination unit 12. In the subsequent step A8, the ignition timing θ is controlled based on the determination result selected in steps B7 and B8.

[0050] The flowchart of Figure 5 will now be described. In the flowchart of Figure 5, steps A1 to A3, B1 to B3, B7, B8, and A8 are the same as those in the flowchart of Figure 4. In step C1 following step B3, the second determination unit 12 determines whether or not the ignition timing θ needs to be changed based on the knock intensity S. In step C2, the selection unit 13 determines whether or not the operating state of the engine 1 is steady (the second condition is satisfied). If the condition of step C2 is satisfied, the process proceeds to step C3; if not, the process proceeds to step B8.

[0051] In step C3, the selection unit 13 selects the knock intensity S from the predetermined intensity S ｔｈ It is determined whether the value of the first determination unit 11 is less than the predetermined value (the third condition is satisfied). If the condition of step C3 is satisfied, the process proceeds to step B7, and if not, the process proceeds to step B8. In step B7, the selection unit 13 selects the determination result of the first determination unit 11, and in step B8, the selection unit 13 selects the determination result of the second determination unit 12. In the subsequent step A8, the ignition timing θ is controlled based on the determination results selected in steps B7 and B8.

[0052] [3. Graphs] Figures 6(A) to 6(F) are graphs for explaining the control content based on the determination results by the first determination unit 11. Figure 6(A) shows the knock intensity S, Figure 6(B) shows the number of knocks k, Figure 6(C) shows the number of ignitions n, Figure 6(D) shows the knock occurrence probability P, Figure 6(E) shows the likelihood ratio R, and Figure 6(F) shows the ignition timing θ. Note that the occurrence of knock can also be determined from the knock intensity S. The value of the number of ignitions n increases each time ignition is performed by the spark plug 2, and the value of the number of knocks k increases each time knock is detected. Each time the number of ignitions n changes, the knock occurrence probability P and likelihood L are calculated, and a preset target knock occurrence probability P is set. ｔｇｔ and the target likelihood L (not shown) ｔｇｔ The likelihood ratio R is calculated based on the above.

[0053] Time t １ The likelihood ratio R is a predetermined value R ｔｈ When the first determination unit 11 determines that the ignition timing θ needs to be changed, the first determination unit 11 determines that the ignition timing θ needs to be changed. When this determination result is selected by the selection unit 13, the control unit 14 determines that the ignition timing θ needs to be changed. １The direction of change of the ignition timing θ is determined based on the knock occurrence probability P at time t １ The knock occurrence probability P is the target knock occurrence probability P ｔｇｔ If the knock occurrence probability P is higher than the target knock occurrence probability P, the control unit 14 controls the ignition timing θ in the retard direction. ｔｇｔ When the ignition timing θ is changed, the values ​​of the number of ignitions n and the number of knocks k that have been counted up to that point are reset.

[0054] At a later time t ２ The likelihood ratio R is again set to a predetermined value R ｔｈ When the first determination unit 11 determines that the ignition timing θ needs to be changed, the first determination unit 11 determines that the ignition timing θ needs to be changed. When this determination result is selected by the selection unit 13, the control unit 14 determines that the ignition timing θ needs to be changed. ２ The direction of change of the ignition timing θ is determined based on the knock occurrence probability P at time t ２ The knock occurrence probability P is the target knock occurrence probability P ｔｇｔ If the knock occurrence probability P is lower than the target knock occurrence probability P, the control unit 14 controls the ignition timing θ in the advance direction. ｔｇｔ Controls the advance amount to match

[0055] 7A to 7G are graphs for explaining the control content in which the determination result by the first determination unit 11 is selected when the first condition is met, and the determination result by the second determination unit 12 is selected when the first condition is not met. Fig. 7A shows the knock intensity S, Fig. 7B shows the number of knocks k, Fig. 7C shows the number of ignitions n, Fig. 7D shows the knock occurrence probability P, and Fig. 7E shows the short-term knock occurrence probability P. Ｓ 7(F) shows the likelihood ratio R, and FIG. 7(G) shows the ignition timing θ.

[0056] As shown in Fig. 7(B), the first determination unit 11 counts the number of knocks k and the number of ignitions n for a relatively long, most recent first predetermined period, and calculates the knock occurrence probability P (= k / n) based on these values. As shown in Fig. 7(C), the value of the knock occurrence probability P is calculated to be a smaller value as the number of ignitions n, which corresponds to the denominator, increases. On the other hand, the value of the likelihood ratio R becomes less likely to decrease as the number of ignitions n increases, and the value of the likelihood ratio R ｔｈ It becomes less likely to become as follows.

[0057] The second determination unit 12 determines whether or not it is necessary to change the ignition timing θ based on the knock intensity S and the knock occurrence probability P. Also, as shown in FIG. 7(E), the second determination unit 12 determines whether or not it is necessary to change the ignition timing θ based on the knock occurrence probability P. Ｓ and the number of ignitions n Ｓ Based on these values, the short-term knock occurrence probability P Ｓ (= k Ｓ / n Ｓ ) is calculated. Ｓ The value of is 0 if no knock occurs during the second predetermined period, and increases rapidly if continuous knock occurs.

[0058] Short-term knock occurrence probability P Ｓ is the threshold P ｔｈ If the likelihood ratio R is equal to or less than the predetermined value R, the first condition is met, and the selection unit 13 selects the determination result of the first determination unit 11. As a result, the control unit 14 controls the ignition timing θ based on the likelihood ratio R (the magnitude of the likelihood L). For example, when the likelihood ratio R is equal to or less than the predetermined value R, ｔｈ If the likelihood ratio R exceeds a predetermined value R, the ignition timing θ is maintained as it is. ｔｈ If it is equal to or lower than this, control is performed to move the ignition timing θ based on the knock occurrence probability P.

[0059] Time t ３ The probability of short-term knock occurrence is P Ｓ is the threshold P ｔｈ If the time t exceeds the predetermined value, the first condition is not satisfied, and the selection unit 13 selects the determination result of the second determination unit 12. As a result, the control unit 14 controls the ignition timing θ based on the knock intensity S and the knock occurrence probability P. For example, at the time t ３ The knock occurrence probability P is the target knock occurrence probability P ｔｇｔ If the likelihood ratio R is higher than the predetermined value R, the control unit 14 controls the ignition timing θ in the retard direction. ｔｈ The time t ４ The control based on the determination result of the second determination unit 12 is continued until the knock occurrence probability P reaches the target knock occurrence probability P ｔｇｔ When the first condition is not satisfied (time t３ ) ignition timing may be continued until the timing returns to the normal timing.

[0060] 8A to 8G are graphs for explaining the control content in which the determination result by the first determination unit 11 is selected when the second condition and the third condition are satisfied, and the determination result by the second determination unit 12 is selected when the second condition or the third condition is not satisfied. Fig. 8A shows the knock intensity S, Fig. 8B shows the number of knocks k, Fig. 8C shows the number of ignitions n, Fig. 8D shows the knock occurrence probability P, Fig. 8E shows the engine torque, Fig. 8F shows the likelihood ratio R, and Fig. 8G shows the ignition timing θ.

[0061] When the engine 1 is in a steady state operation (engine torque is substantially constant), the knock intensity S is equal to or exceeds a predetermined intensity S ｔｈ When the likelihood ratio R is less than a predetermined value R, the second and third conditions are met, and the selection unit 13 selects the determination result of the first determination unit 11. As a result, the control unit 14 controls the ignition timing θ based on the likelihood ratio R (the magnitude of the likelihood L). For example, when the likelihood ratio R is less than a predetermined value R, ｔｈ If it exceeds the predetermined value, the ignition timing θ is maintained as it is.

[0062] Time t ５ The knock intensity S is a predetermined intensity S ｔｈ If the above condition is met, the third condition is not met, and the selection unit 13 selects the determination result of the second determination unit 12. As a result, the control unit 14 controls the ignition timing θ based on the knock intensity S and the knock occurrence probability P. For example, at time t ５ The retard amount corresponding to the knock intensity S is set, and the ignition timing θ is temporarily moved in the retard direction. At this time, the counts of the number of knocks k and the number of ignitions n are reset, and the determination by the first determination unit 11 is stopped. Thereafter, the ignition timing θ is controlled to be gradually returned in the advance direction. The ignition timing θ returns to the original state (time t ５ If a knock is detected again before the time t ６ When the ignition timing θ returns to the original value, the first determination unit 11 resumes the determination.

[0063] Time t ７ The likelihood ratio R is a predetermined value R ｔｈIf the condition is equal to or less than the time t, the first determination unit 11 determines that the ignition timing θ needs to be changed. At this time, the second and third conditions are satisfied, so the determination result of the first determination unit 11 is selected by the selection unit 13. The control unit 14 selects the determination result of the first determination unit 11 at the time t ７ The ignition timing θ is controlled based on the knock occurrence probability P. When the ignition timing θ is changed, the values ​​of the number of ignitions n and the number of knocks k that have been counted up to that point are reset, and the value of the likelihood L is also reset.

[0064] Time t ８ ~t １０ is a period in which the engine torque fluctuates greatly and the engine 1 is in an unsteady operating state. In this period, the second condition is not satisfied, and the selection unit 13 selects the determination result of the second determination unit 12. For example, at time t ９ When a knock is detected at time t ９ The retard amount is set according to the knock intensity S, and the ignition timing θ is temporarily moved in the retard direction and then gradually returned to the advance direction. １０ When the operating state of the engine 1 returns to the steady state at time t, the second condition is met, and the determination result of the first determination unit 11 becomes selectable. ９ The ignition timing θ changed in ９ The first determination unit 11 does not resume determination until the ignition timing θ returns to the value before the change.

[0065] [4. Effects] (1) The engine control device 10 suppresses knock by controlling the ignition timing θ of the engine 1, and includes a first determination unit 11, a second determination unit 12, and a selection unit 13. The first determination unit 11 calculates a knock occurrence probability P and a likelihood L of the knock occurrence probability P based on the number of ignitions n and the number of knocks k, and determines whether or not the ignition timing θ needs to be changed based on the magnitude of the likelihood L. The second determination unit 12 calculates a knock intensity S or a knock occurrence probability P, and determines whether or not the ignition timing θ needs to be changed based on the knock intensity S or the knock occurrence probability P. The selection unit 13 selects the determination result of either the first determination unit 11 or the second determination unit 12 based on a predetermined condition.

[0066] In this way, by selectively using the determination result of the first determination unit 11 and the determination result of the second determination unit 12 depending on predetermined conditions, the control accuracy of the ignition timing θ can be improved, and fuel economy can be improved while knock is suppressed. For example, by adopting the determination result of the first determination unit 11 in an operating state of the engine 1 in which the determination accuracy of the first determination unit 11 is likely to improve, it becomes easier to maintain the ignition timing θ slightly more advanced than with conventional knock retard control, and fuel economy can be improved while knock is suppressed. Furthermore, by adopting the determination result of the second determination unit 12 in an operating state of the engine 1 in which the determination accuracy of the first determination unit 11 is likely to decrease, knock can be suppressed with fuel economy equivalent to that of conventional knock retard control.

[0067] (2) The first determination unit 11 determines the number of ignitions n, the number of knocks k, and the target knock occurrence probability P ｔｇｔ Based on this, the target likelihood L ｔｇｔ and calculate the target likelihood L for the likelihood L ｔｇｔ The likelihood ratio R is calculated as the ratio of ｔｈ It can be determined that the ignition timing θ needs to be changed when the number of ignitions n is sufficient and the ignition timing θ is inappropriate. The value of the likelihood ratio R becomes small when the likelihood ratio R and the predetermined value R ｔｈ By evaluating the magnitude relationship between the first determination unit 11 and the ignition timing θ, the reliability of the determination result by the first determination unit 11 can be increased, and the control accuracy of the ignition timing θ can be further improved.

[0068] (3) In the engine control device 10, the number of ignitions n and the number of knocks k are, for example, the numbers of times during the most recent first predetermined period. This configuration allows the most recent operating state of the engine 1 to be reflected in the knock occurrence probability P and its likelihood L, and allows the timing for changing the ignition timing θ to be determined with high accuracy. Therefore, the accuracy of controlling the ignition timing θ can be improved, and fuel economy can be improved while knocking is suppressed.

[0069] (4) The selection unit 13 selects the short-term knock occurrence probability P Ｓ is the threshold P ｔｈThe determination result of the first determination unit 11 can be selected when a first condition, that is, the ignition timing θ is equal to or less than the predetermined value, is satisfied. Alternatively, the determination result of the second determination unit 12 can be selected when the first condition is not satisfied. In this manner, by prioritizing the determination result of the second determination unit 12 over the determination result of the first determination unit 11 when frequent knocks (continuous knocks) occur within a short period of time, the knock suppression effect of the engine 1 can be improved. That is, even if continuous knocks occur, if the number of ignitions n is large, the likelihood L and the likelihood ratio R are not likely to change significantly, and knock suppression may be delayed. Therefore, when continuous knocks are detected, the determination result of the second determination unit 12 is prioritized, thereby performing knock suppression early. Furthermore, by prioritizing the determination result of the first determination unit 11 when continuous knocks do not occur, the ignition timing θ can be maintained slightly more advanced than in conventional knock retard control, thereby improving fuel economy.

[0070] (5) The selection unit 13 can select the determination result of the first determination unit 11 when the second condition, that is, the engine 1 is operating steadily, is satisfied, and can select the determination result of the second determination unit 12 when the second condition is not satisfied. This selection can improve fuel economy when the operating state of the engine 1 is stable. Furthermore, when the operating state of the engine 1 is transiently fluctuating, the knock suppression effect of the engine 1 can be improved. That is, when the operating state of the engine 1 is transiently fluctuating, the relationship between the ignition timing θ and the knock occurrence probability P is thought to change (different from the base characteristic map of FIG. 2 ), and it may be impossible to accurately calculate how much the ignition timing θ should be shifted. Therefore, the selection unit 13 suppresses knocking of the engine 1 by selecting the determination result of the second determination unit 12.

[0071] (6) In the engine control device 10 described above, the value of likelihood L is reset, for example, when the engine 1 changes between steady operation and unsteady operation. The number of ignitions n and the number of knocks k are also reset when the engine 1 changes between steady operation and unsteady operation. This improves the accuracy of calculating likelihood L and likelihood ratio R, and enables accurate determination of the timing for changing the ignition timing θ. This improves the control accuracy of the ignition timing θ, and improves fuel economy while suppressing knocking. The value of likelihood L may be reset when the ignition timing θ is changed, not just when the engine 1 changes between steady operation and unsteady operation.

[0072] (7) The selection unit 13 selects whether the knock intensity S is a predetermined intensity S ｔｈ When a third condition is satisfied, that is, when the third condition is satisfied, the determination result of the first determination unit 11 is selected, and when the third condition is not satisfied, the determination result of the second determination unit 12 is selected. In this way, by prioritizing the determination result of the second determination unit 12 over the determination result of the first determination unit 11 when a strong knock occurs, it is possible to improve the knock suppression effect of the engine 1. Furthermore, by prioritizing the determination result of the first determination unit 11 when a strong knock does not occur, it is possible to maintain the ignition timing θ slightly more advanced than in conventional knock retard control, thereby improving fuel economy.

[0073] (8) The engine control device 10 includes a base characteristic map 15 that represents the relationship between the ignition timing θ and the knock probability P. The ignition timing θ of the engine 1 is set to a target knock probability P calculated from the base characteristic map 15. ｔｇｔ For example, on the graph of the base characteristic map 15 shown in FIG. 2, the base ignition timing θ is the X coordinate of the point whose Y coordinate corresponds to the knock occurrence probability P. Ｂ is calculated. Then, the base ignition timing θ Ｂ and the actual ignition timing θ ｒｅａｌ In this way, the ignition timing θ is controlled based on the difference between the knock occurrence probability P and the target knock occurrence probability P ｔｇｔ By making the ignition timing θ follow the above, it is possible to appropriately change the ignition timing θ, i.e., to prevent unnecessary large changes, thereby improving fuel economy while suppressing knocking.

[0074] [5. Other] The above-described embodiments are merely illustrative and are not intended to exclude various modifications or applications of techniques not explicitly described in the present embodiments. Various modifications of the components of the present embodiments can be implemented without departing from the spirit of the present embodiments. The components of the present embodiments can be selected or combined as needed.

[0075] The engine control device 10 described above is applicable not only to engines 1 mounted on automobiles, but also to engines 1 mounted on ships, driving force generating devices, power generating devices, etc. By controlling the engine 1 using the engine control device 10 having at least the first determination unit 11, the second determination unit 12, and the selection unit 13, it is possible to improve fuel efficiency while suppressing knocking of the engine 1, and to obtain the same effects as those of the above-described embodiment.

[0076] The present invention is applicable to the manufacturing industry of engine control devices that control engine ignition timing, the manufacturing industry of engines and engine systems that include engine control devices, and the manufacturing industry of vehicles that are equipped with engines and engine control devices.

[0077] REFERENCE SIGNS LIST 1 Engine 2 Spark plug 3 Knock sensor 4 Water temperature sensor 5 Crank angle sensor 6 Air flow sensor 7 Accelerator opening sensor 8 Vehicle speed sensor 10 Engine control device 11 First determination unit 12 Second determination unit 13 Selection unit 14 Control unit 15 Base characteristic map k Number of knocks n Number of ignitions P Knock occurrence probability P Ｓ Short-term knock occurrence probability L Likelihood R Likelihood ratio θ Ignition timing S Knock intensity P ｔｇｔ Target knock occurrence probability L ｔｇｔ Target likelihood θ ｒｅａｌ Actual ignition timing θ Ｂ Base ignition timing P ｔｈ Threshold R ｔｈ Predetermined value S ｔｈ Predetermined strength

Claims

1. An engine control device that suppresses knocking by controlling the ignition timing of an engine, comprising: a first determination unit that calculates a knocking occurrence probability and a likelihood of the knocking occurrence probability based on the number of ignition times and the number of knocking times, and determines whether to change the ignition timing based on the magnitude of the likelihood; a second determination unit that calculates a knocking intensity or the knocking occurrence probability, and determines whether to change the ignition timing based on the knocking intensity or the knocking occurrence probability; and a selection unit that selects a determination result of either the first determination unit or the second determination unit based on a predetermined condition.

2. The engine control device according to claim 1, wherein the first determination unit calculates a target likelihood based on the number of ignition times, the number of knocking times, and a target knocking occurrence probability, calculates a likelihood ratio that is a ratio of the target likelihood to the likelihood, and determines that it is necessary to change the ignition timing when the likelihood ratio becomes equal to or less than a predetermined value.

3. The engine control device according to claim 1, wherein the number of ignition times and the number of knocking times are the numbers in a most recent first predetermined period.

4. The engine control device according to claim 3, wherein the selection unit selects the determination result of the first determination unit when a first condition that the knocking occurrence probability in a most recent second predetermined period shorter than the first predetermined period is equal to or less than a threshold value is satisfied, and selects the determination result of the second determination unit when the first condition is not satisfied.

5. The engine control device according to claim 1, wherein the selection unit selects the determination result of the first determination unit when a second condition that the engine is in a steady operation is satisfied, and selects the determination result of the second determination unit when the second condition is not satisfied.

6. The engine control device according to claim 5, wherein the value of the likelihood is reset when changing between the steady operation and the non-steady operation of the engine.

7. The engine control device according to claim 1, wherein the selection unit selects the determination result of the first determination unit when a third condition that the knocking intensity is less than a predetermined intensity is satisfied, and selects the determination result of the second determination unit when the third condition is not satisfied.

8. The engine control device according to claim 1, further comprising a base characteristic map representing the relationship between the ignition timing and the knock occurrence probability, wherein the ignition timing is controlled so that the knock occurrence probability matches a target knock occurrence probability calculated from the base characteristic map.

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