Engine control method and control device

Abstract

The control device (50) calculates the ignition timing of each cylinder (101) of the engine (100) based on the presence or absence of knock, sets the ignition timing in the cylinder (101) which is closer to the advance angle side than the maximum retard ignition timing on the maximum retard angle side and the ignition timing of any cylinder which is closer to the retard angle side than the maximum advance angle ignition timing on the maximum advance angle side as the reference ignition timing, sets a range of allowable timing difference based on the reference ignition timing, i.e., an allowable timing difference range, and when it is determined that the ignition timing of each cylinder (101) does not fall within the allowable timing difference range, corrects the ignition timing in such a way that the timing difference relative to the reference ignition timing falls within the allowable timing difference range.

Description

Technical Field

[0001] The invention relates to a control method and a control device for an engine. Background Art

[0002] In an engine having multiple cylinders, when the occurrence of knock is detected, the ignition timing of the cylinder that has caused the knock is retarded in order to suppress the occurrence of knock in the next combustion cycle. On the other hand, if the ignition timing of each cylinder is controlled separately, the fluctuation of the ignition timing may increase, causing the torque difference between the cylinders to become too large. Therefore, in the control device of Patent Document 1, the ignition timing of each cylinder is set to be within a range closer to the advance angle side than the torque allowable ignition timing difference, based on the ignition timing on the most retarded angle side, i.e., the most retarded ignition timing.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2018-178927 Summary of the invention

[0004] However, the control device of Patent Document 1 sets the maximum retarded ignition timing as the setting reference for the allowable range of the ignition timing difference of each cylinder, so when the maximum retarded ignition timing is set too close to the retarded angle side due to malfunction of the knock sensor, etc., the ignition timing of all cylinders will be overcorrected to the retarded angle side. Therefore, the output torque of the engine may be reduced.

[0005] An object of the present invention is to provide a method and a device for controlling an engine that can suppress a decrease in the output torque of the engine when performing control to suppress fluctuations in the ignition timing of each cylinder.

[0006] The present invention sets the ignition timing of any cylinder whose ignition timing is closer to the advanced angle side than the maximum retarded ignition timing and closer to the retarded angle side than the maximum advanced angle ignition timing as the reference ignition timing, and controls the ignition timing of each cylinder in such a way that the timing difference relative to the reference ignition timing falls within the allowable timing difference range, thereby solving the above-mentioned problem.

[0007] Effects of the Invention

[0008] According to the present invention, since the ignition timing serving as a control reference is an ignition timing other than the most retarded ignition timing and the most advanced ignition timing, a reduction in the output torque of the engine can be suppressed when performing control to suppress fluctuations in the ignition timing of each cylinder. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a diagram showing a part of the structure of an engine controlled by the control device according to the embodiment of the present invention.

[0010] Figure 2 It is a block diagram showing the configuration of a control device according to an embodiment of the present invention.

[0011] Figure 3 Yes means Figure 2 A flowchart of the sequence of a method for controlling an engine of a control device.

[0012] Figure 4 It means by Figure 2 FIG. 1 is a diagram showing an example of correction of the ignition timing of a cylinder of an engine performed by a control device. DETAILED DESCRIPTION

[0013] Hereinafter, embodiments of the present invention will be described based on the drawings.

[0014] like Figure 1 As shown, the engine (internal combustion engine) 100 is controlled by a control device 50 (ECU). The engine 100 of this embodiment is an inline 4-cylinder engine having 4 cylinders. Figure 1 1 shows one of the cylinders 101. In addition, the engine 100 involved in the present invention is not limited to an inline 4-cylinder engine, as long as it has 3 cylinders or more, such as an inline 3-cylinder, inline 6-cylinder, V-6-cylinder, V-8-cylinder, etc.

[0015] The engine 100 has an intake passage 111 and an exhaust passage 125. An air filter 112, an air flow meter 113 for detecting the intake air flow rate, a throttle valve 114 for controlling the intake air flow rate, and a header 115 are provided in the intake passage 111. Although not shown in the figure, a compressor wheel and an intercooler of a supercharger are provided in the intake passage 111. An actuator 116 such as a DC motor for adjusting the opening of the throttle valve 114 is provided in the throttle valve 114. In addition, a fuel injection valve 118 is provided in the intake passage 111a branched from the header 115 to each cylinder 101. In addition, an air-fuel ratio sensor 126, an exhaust purification catalyst 127, and a muffler 129 are provided in the exhaust passage 125. Although not shown in the figure, a turbine of a supercharger and a bypass circuit for bypassing the turbine are provided in the exhaust passage 125, and a wastegate valve for adjusting the amount of exhaust gas bypassing the turbine is provided in the bypass circuit.

[0016] The cylinder 101 has a cylinder hole 119 formed in the cylinder body, and the piston 120 is arranged in the cylinder hole 119 so as to be reciprocatingly movable. In addition, an intake valve 121 and an exhaust valve 122 are provided in the cylinder head 102 mounted on the upper surface of the cylinder body. The space surrounded by the cylinder hole 109, the piston 120 and the cylinder head 102 constitutes a combustion chamber 123. In addition, a spark plug 124 is mounted on the cylinder head 102 so as to face the combustion chamber 123. In addition, a knock sensor 150 is provided in the cylinder body to detect the vibration generated in the cylinder 101 and to detect the presence or absence of the occurrence of knock. The knock sensor 150 is configured to include a piezoelectric element and a magnetostrictive material, and extracts a vibration (knock vibration) of a specific frequency corresponding to the knock and converts it into an electrical signal. The detection signal of the knock sensor 150 is output to the control device 50.

[0017] A crank angle sensor 131 is provided on the crankshaft 130 of the engine 100, and a detection signal of the crank angle sensor 131 is output to the control device 50. In addition to detecting the crank angle, the crank angle sensor 131 also functions as an engine rotation speed detection unit that detects the rotation speed (rotation speed per unit time) of the engine 100. In addition, the output signal of the crank angle sensor 131 corresponds to the stroke position (top dead center, etc.) of the piston 120 of each cylinder 101, so the cylinder 101 in which knocking occurs can be determined based on the output signal of the crank angle sensor 131 that detects the timing of knock vibration using the knock sensor 150 and the ignition timing of the spark plug 124.

[0018] The control device 50 receives a detection signal from the air flow meter 113 and obtains the intake air flow rate. In addition, the control device 50 receives a detection signal from the air-fuel ratio sensor 126 and obtains the air-fuel ratio. In addition, the control device 50 calculates the crankshaft unit angle signal of the crankshaft rotation angle sensor 131 within a constant time, or measures the period of the crankshaft reference angle signal, thereby obtaining the rotation speed Ne of the engine 100.

[0019] In addition, the control device 50 outputs a control signal to the actuator 116 to electronically control the opening of the throttle valve 114 and the waste gate valve so as to achieve the requested torque calculated based on the driver's accelerator pedal operation amount, etc. In addition, the control device 50 outputs a control signal to the fuel injection valve 118, and the fuel injection valve 118 is controlled so as to inject the fuel controlled to a predetermined pressure into the intake passage 111a. In addition, the control device 50 outputs a control signal to the spark plug 124 to ignite the intake air mixture of the combustion chamber 123.

[0020] Next, use Figure 2 The structure of the control device 50 will be described.

[0021] The control device 50 includes an ignition timing calculation unit 51, a reference cylinder setting unit 52, a reference ignition timing setting unit 53, an allowable timing difference range setting unit 54, an ignition timing determination unit 55, and an ignition timing correction unit 56. The control device 50 is composed of a computer having a CPU, a ROM, and a RAM. The ignition timing calculation unit 51, the reference cylinder setting unit 52, the reference ignition timing setting unit 53, the allowable timing difference range setting unit 54, the ignition timing determination unit 55, and the ignition timing correction unit 56 are stored in the ROM as a program for executing the functions of the control device 50.

[0022] The ignition timing calculation unit 51 calculates the ignition timing of each cylinder 101 based on the operating conditions of the engine 100 acquired by the operating condition acquisition unit 57 and the presence or absence of knock detected by the knock sensor 150. Specifically, when the knock sensor 150 detects the occurrence of knock, the ignition timing calculation unit 51 makes the ignition timing of the cylinder 101 in the next combustion cycle lag by a predetermined timing compared to the currently set ignition timing of the cylinder 101. On the other hand, when the knock sensor 150 does not detect the occurrence of knock, the ignition timing calculation unit 51 makes the ignition timing of the cylinder 101 in the next combustion cycle remain the same or advance compared to the currently set ignition timing of the cylinder 101 according to the operating conditions of the engine 100. The ignition timing calculation unit 51 calculates the ignition timing of the cylinder 101 in the next combustion cycle based on the current ignition timing of the cylinder 101 and the retardation or advancement of the ignition timing in the next combustion cycle. The ignition timing of the cylinder 101 is represented by the total retardation of the ignition timing relative to the top dead center in terms of the crank angle.

[0023] The reference cylinder setting unit 52 sets, as the reference cylinder, the cylinder whose ignition timing is set to the advanced angle side than the ignition timing on the maximum retard angle side (hereinafter, also referred to as the maximum retard ignition timing) among the ignition timings of the four cylinders 101 at any timing, and any one of the one or more cylinders 101 whose ignition timing is set to the retarded angle side than the ignition timing on the maximum advance angle side (hereinafter, also referred to as the maximum advance angle ignition timing). In other words, the reference cylinder setting unit 52 sets as the reference cylinder any one of the cylinders that have reached the maximum retarded ignition timing and the cylinders other than the cylinder that has reached the maximum advance angle ignition timing. The reference cylinder in the present embodiment refers to the cylinder that has reached the reference ignition timing when the ignition timing is corrected. Figure 4 is a diagram showing an example of correction of the ignition timing of a cylinder. Specifically, Figure 4As shown on the left side of FIG. 1 , the engine 100 has four cylinders 101a, 101b, 101c, and 101d. When the ignition timings of the respective cylinders are in the order of D0a, D0b, D0c, and D0d from the advanced angle side to the retarded angle side, the reference cylinder setting unit 52 of the present embodiment sets the cylinder 101b as the reference cylinder 101S. In addition, among the ignition timings D0a, D0b, D0c, and D0d, the ignition timing D0a is the most retarded ignition timing on the most retarded angle side, the ignition timing D0b is the ignition timing on the second largest retarded angle side, the ignition timing D0c is the ignition timing on the third largest retarded angle side, and the ignition timing D0d is the most advanced angle ignition timing on the most advanced angle side. That is, the reference cylinder setting unit 52 sets the cylinder 101 b set to the ignition timing D0b on the second largest retard angle side after the most retarded ignition timing D0a as the reference cylinder 101S.

[0024] In addition, the reference cylinder setting unit 52 is not limited to this, and the cylinder 101c that sets the ignition timing D0c on the third largest retard angle side after the maximum retard ignition timing D0a can also be set as the reference cylinder 101S. Similarly, in the case of a 6-cylinder engine, among the 6 cylinders at any timing, any one of the 4 cylinders other than the cylinder that reaches the maximum retard ignition timing and the cylinder that reaches the maximum advanced angle ignition timing is set as the reference cylinder. In addition, in the case of an 8-cylinder engine, among the 8 cylinders at any timing, any one of the 6 cylinders other than the cylinder that reaches the maximum retard ignition timing and the cylinder that reaches the maximum advanced angle ignition timing is set as the reference cylinder.

[0025] The reference ignition timing setting unit 53 sets the ignition timing of the reference cylinder 101S obtained by the reference cylinder setting unit 52 as the reference ignition timing DS. That is, the reference ignition timing setting unit 53 sets the ignition timing D0b of the cylinder 101b at the second largest retard angle after the most retarded ignition timing D0a as the reference ignition timing DS.

[0026] The allowable timing difference range setting unit 54 sets the allowable timing difference range R, which is a range of timing differences that can be allowed based on the reference ignition timing DS, based on the operating conditions of the engine 100 acquired by the operating condition acquisition unit 57. Figure 4 As shown, the allowable timing difference range setting unit 54 sets the threshold value of the retard angle side of the allowable timing difference range R, that is, the retard angle side allowable timing difference L1, and sets the threshold value of the advance angle side of the allowable timing difference range R, that is, the advance angle side allowable timing difference L2. Here, if the crank angle retarded by the retard angle side allowable timing difference L1 is Dr, and the crank angle advanced by the advance angle side allowable timing difference L2 is Da with reference to the reference ignition timing DS, the allowable timing difference range R is set to a range between the crank angle Dr and the crank angle Da.

[0027] The operating condition of the engine 100 acquired by the operating condition acquisition unit 57 is the intake air flow rate detected by the air flow meter 113 and the rotation speed of the engine 100 detected by the crank angle sensor 131. That is, the allowable timing difference range R is set based on the output torque (engine load) and the rotation speed of the engine 100 estimated from the intake air flow rate. In addition, the allowable timing difference range R can be set based on either the output torque (engine load) or the rotation speed of the engine 100. In addition, the estimation of the output torque (engine load) of the engine 100 can be calculated based on the driver's accelerator pedal operation amount, etc., or can be calculated based on the opening of the throttle valve 114. In addition, the operating condition of the engine 100 acquired by the operating condition acquisition unit 57 can include the air-fuel ratio detected by the air-fuel ratio sensor 126, etc. And, the retard angle side allowable timing difference L1 and the advance angle side allowable timing difference L2 of the allowable timing difference range R are set according to such operating conditions.

[0028] In addition, Figure 4 The retarded angle side permissible timing difference L1 is smaller than the advanced angle side permissible timing difference L2, but the present invention is not limited thereto. The retarded angle side permissible timing difference L1 and the advanced angle side permissible timing difference L2 may be equal to each other, or the retarded angle side permissible timing difference L1 may be larger than the advanced angle side permissible timing difference L2.

[0029] Note that the allowable timing difference range R may be a timing difference range that is set in advance regardless of the operating conditions of the engine 100 .

[0030] The ignition timing determination unit 55 determines whether the ignition timing of each cylinder 101 falls within the allowable timing difference range R based on the reference ignition timing DS. The ignition timing determination unit 55 includes a first ignition timing determination unit 55a for determining whether the ignition timing on the retarded angle side of the reference ignition timing DS falls within the allowable timing difference range R, and a second ignition timing determination unit 55b for determining whether the ignition timing on the advanced angle side of the reference ignition timing DS falls within the allowable timing difference range R.

[0031] Specifically, the first ignition timing determination unit 55a determines whether the ignition timing of each cylinder 101 is set to the retarded side relative to the reference ignition timing DS more than the retarded side allowable timing difference L1. Figure 4 As shown on the left side of , it is determined that the ignition timing D0a of the cylinder 101a is set to the retarded side relative to the reference ignition timing DS more than the retarded side allowable timing difference L1, that is, does not fall within the allowable timing difference range R.

[0032] In addition, the second ignition timing determination unit 55b determines whether the ignition timing of each cylinder 101 is set to the advanced angle side relative to the reference ignition timing DS more than the advanced angle side allowable timing difference L2. Figure 4 As shown on the left side of , it is determined that the ignition timing D0c of the cylinder 101c is set to the advanced angle side relative to the reference ignition timing DS than the advanced angle side allowable timing difference L2, that is, it falls within the allowable timing difference range R. On the other hand, it is determined that the ignition timing D0d of the cylinder 101d is set to the advanced angle side relative to the reference ignition timing DS than the advanced angle side allowable timing difference L2, that is, it does not fall within the allowable timing difference range R.

[0033] Furthermore, since the ignition timing D0b of the cylinder 101c is set as the reference ignition timing DS, it is determined that the ignition timing D0b falls within the allowable timing difference range R.

[0034] When the ignition timing determination unit 55 determines that the ignition timing of the cylinder 101 does not fall within the allowable timing difference range R, the ignition timing correction unit 56 corrects the ignition timing of the cylinder 101 so that the timing difference of the ignition timing of the cylinder 101 relative to the reference ignition timing DS falls within the allowable timing difference range R. The ignition timing correction unit 56 includes a first ignition timing correction unit 56a that corrects the ignition timing on the more retarded side than the reference ignition timing DS, and a second ignition timing correction unit 56b that corrects the ignition timing on the more advanced side than the reference ignition timing DS.

[0035] That is, when the ignition timing of the cylinder 101 is set to be closer to the retarded angle side than the retarded angle side permissible timing difference L1 with respect to the reference ignition timing DS, the first ignition timing correction unit 56a corrects the ignition timing of the cylinder 101 so that the timing difference of the ignition timing of the cylinder 101 on the retarded angle side relative to the reference ignition timing DS reaches the retarded angle side permissible timing difference L1. Specifically, Figure 4 As shown on the right side of FIG. 1 , the ignition timing D0a of the cylinder 101a, which is set to be closer to the retarded angle side than the retarded angle side permissible timing difference L1 with respect to the reference ignition timing DS, is corrected in a manner consistent with the crank angle Dr which is retarded by the retarded angle side permissible timing difference L1 with respect to the reference ignition timing DS. That is, the ignition timing D0a is corrected to the advanced angle side by D0a-D0b-L1.

[0036] In addition, when the ignition timing of the cylinder 101 is set to be closer to the advanced angle side than the allowable timing difference L2 on the advanced angle side with respect to the reference ignition timing DS, the second ignition timing correction unit 56b corrects the ignition timing of the cylinder 101 so that the timing difference on the advanced angle side of the ignition timing of the cylinder 101 with respect to the reference ignition timing DS reaches the allowable timing difference L2 on the advanced angle side. Specifically, Figure 4As shown on the right side of FIG. 1 , the ignition timing D0d of the cylinder 101d set to be closer to the advanced angle side than the allowable timing difference L2 on the advanced angle side with respect to the reference ignition timing DS is corrected in a manner consistent with the crank angle Da advanced by the allowable timing difference L2 on the advanced angle side with respect to the reference ignition timing DS. That is, the ignition timing D0d is corrected to the retarded angle side by D0d-D0b-L2.

[0037] In addition, in the present embodiment, the timing difference of the ignition timing D0a on the retarded side relative to the reference ignition timing DS is corrected to be consistent with the retarded side permissible timing difference L1, but the present invention is not limited thereto, and the timing difference of the ignition timing D0a on the retarded side relative to the reference ignition timing DS only needs to be less than or equal to the retarded side permissible timing difference L1. In addition, the timing difference of the ignition timing D0d on the advanced side relative to the reference ignition timing DS is corrected to be consistent with the advanced side permissible timing difference L2, but the present invention is not limited thereto, and the timing difference of the ignition timing D0d on the advanced side relative to the reference ignition timing DS only needs to be less than or equal to the advanced side permissible timing difference L2. That is, the ignition timing of the cylinder 101 only needs to be corrected in such a manner that the timing difference of the ignition timing of the cylinder 101 relative to the reference ignition timing DS falls within the permissible timing difference range R.

[0038] Next, use Figure 3 The following describes the procedure of the control method of the engine 100 by the control device 50 . As a premise of this control flow, the ignition timing of the engine 100 is set to a timing corresponding to the operating condition of the engine 100 acquired by the operating condition acquisition unit 57 .

[0039] First, in step S1, the ignition timing calculation unit 51 of the control device 50 determines whether the knock sensor 150 detects the occurrence of knock and identifies the cylinder 101 where the knock occurs. That is, the cylinder 101 where the knock occurs is identified based on the output signal of the crank angle sensor 131 at the timing of detecting the knock vibration by the knock sensor 150 and the ignition timing of the spark plug 124.

[0040] When it is determined that the occurrence of knock is detected, the control enters step S2, and the ignition timing calculation unit 51 calculates the retard angle amount of the ignition timing of the next combustion cycle of the cylinder 101 where the knock occurs. On the other hand, when it is determined that the occurrence of knock is not detected, the control enters step S3, and the ignition timing calculation unit 51 calculates the advance angle amount (including zero) of the ignition timing of the next combustion cycle of the cylinder 101 where the knock does not occur. Then, in step S4, the ignition timing calculation unit 51 calculates the ignition timing of each cylinder 101 separately. Specifically, the ignition timing calculation unit 51 retards the current ignition timing of the cylinder 101 where the knock is detected by the retard angle amount calculated in step S3, and maintains the current ignition timing of the cylinder 101 where the knock is not detected unchanged or advances it by the advance angle amount calculated in step S4, thereby calculating the ignition timing of each cylinder 101 separately.

[0041] Next, in step S5, the reference cylinder setting unit 52 of the control device 50 sets the reference cylinder 101S. As described above, in this embodiment, the reference cylinder 101S is the cylinder 101b (refer to Figure 4 ) In addition, in step S6, the reference ignition timing setting unit 53 of the control device 50 sets the ignition timing D0b of the cylinder 101b as the reference ignition timing DS.

[0042] Next, in step S7, the allowable timing difference range setting unit 54 sets the retarded allowable timing difference L1 and the advanced allowable timing difference L2. As described above, the retarded allowable timing difference L1 is a threshold value on the retarded side of the allowable timing difference range R, and the advanced allowable timing difference L2 is a threshold value on the advanced side of the allowable timing difference range R.

[0043] Next, in step S8, the first ignition timing determination unit 55a determines whether the ignition timing of each cylinder 10 deviates to a greater extent than the allowable timing difference L1 on the retarded angle side relative to the reference ignition timing DS. That is, the first ignition timing determination unit 55a determines whether the ignition timing of each cylinder 101 is set to be closer to the retarded angle side than the allowable timing difference L1 on the retarded angle side relative to the reference ignition timing DS. When it is determined that the ignition timing of the cylinder 10 deviates to a greater extent than the allowable timing difference L1 on the retarded angle side relative to the reference ignition timing DS, the control enters step S10, and the first ignition timing correction unit 56a corrects the ignition timing of the cylinder 101 to Dr=DS+L1. That is, if Figure 4 As shown, the first ignition timing correction unit 56a resets the ignition timing D0a of the cylinder 101a to be shifted toward the retarded side by the retarded side allowable timing difference L1 with respect to the reference ignition timing DS. Then, the control proceeds to step S12.

[0044] In step S8 , when it is determined that the ignition timing of the cylinder 10 has not deviated from the reference ignition timing DS to the retarded side by a greater amount than the retarded side allowable timing difference L1 , control proceeds to step S9 .

[0045] In step S9, the second ignition timing determination unit 55b determines whether the ignition timing of each cylinder 10 deviates more significantly than the allowable timing difference L2 on the advance angle side relative to the reference ignition timing DS. That is, the second ignition timing determination unit 55b determines whether the ignition timing of each cylinder 101 is set to be closer to the advance angle side than the allowable timing difference L2 on the advance angle side relative to the reference ignition timing DS. When it is determined that the ignition timing of the cylinder 10 deviates more significantly than the allowable timing difference L2 on the advance angle side relative to the reference ignition timing DS, the control enters step S11, and the second ignition timing correction unit 56b corrects the ignition timing of the cylinder 101 to Da=DS-L2. That is, if Figure 4 As shown, the second ignition timing correction unit 56b resets the ignition timing D0d of the cylinder 101d to the advanced angle side by the advance angle side allowable timing difference L2 with respect to the reference ignition timing DS. Then, the control proceeds to step S12.

[0046] On the other hand, in step S9, when it is determined that the ignition timing of the cylinder 10 has not deviated from the reference ignition timing DS to the advanced angle side by a greater amount than the advanced angle side allowable timing difference L2, the ignition timing correction unit 56 does not correct the ignition timing set in step S4, and control proceeds to step S12.

[0047] In step S12 , the control device 50 controls the ignition timing of the spark plug 124 of each cylinder 101 based on the ignition timing finally set by the control in steps S1 to S11 .

[0048] As described above, the control device 50 of the engine 100 of the present embodiment sets any one of the cylinders 101 whose ignition timing is closer to the advanced angle side than the maximum retarded ignition timing on the maximum retarded angle side and whose ignition timing is closer to the retarded angle side than the maximum advanced angle ignition timing on the maximum advanced angle side as the reference cylinder 101S. Furthermore, the control device 50 determines whether the ignition timing of each cylinder 101 falls within the allowable timing difference range R based on the reference ignition timing DS of the reference cylinder 101S, and corrects the ignition timing of the cylinder 101 so that it falls within the allowable timing difference range R when it is determined that it does not fall within the allowable timing difference range R. Therefore, even when the maximum retarded ignition timing is excessively close to the retarded angle side due to erroneous detection of the occurrence of knock by the knock sensor 150, the control device 50 does not set the maximum retarded ignition timing as the reference ignition timing, and thus it is possible to prevent the ignition timing of all the cylinders 101 of the engine 100 from being excessively corrected to the retarded angle side. That is, in the control method executed by the control device 50, when the control is performed to suppress the fluctuation of the ignition timing of each cylinder 101, the output torque reduction of the engine 100 can be suppressed. In addition, the control device 50 does not set the maximum advanced angle ignition timing as the reference ignition timing, thereby being able to set the average ignition timing of all cylinders 101 of the engine 100 to the retarded angle side when knocking occurs. Therefore, the control device 50 can suppress the fluctuation of the ignition timing for each cylinder 101 and prevent the occurrence of knocking.

[0049] In addition, the control device 50 sets a retarded angle side permissible timing difference L1 as a threshold value on the retarded angle side of the permissible timing difference range R, and an advance angle side permissible timing difference L2 as a threshold value on the advance angle side. The control device 50 corrects the ignition timing of the cylinder 101 in such a manner that the timing difference on the retarded angle side of the ignition timing of the cylinder 101 relative to the reference ignition timing DS is less than or equal to the retarded angle side permissible timing difference L1. In addition, the control device 50 corrects the ignition timing of the cylinder 101 in such a manner that the timing difference on the advance angle side of the ignition timing of the cylinder 101 relative to the reference ignition timing DS is less than or equal to the advance angle side permissible timing difference L2. In this way, the control of the ignition timing on the retarded angle side and the control of the ignition timing on the advance angle side are respectively performed with reference to the reference ignition timing DS, thereby appropriately suppressing the fluctuation of the ignition timing on the retarded angle side and the fluctuation of the ignition timing on the advance angle side according to each condition.

[0050] Furthermore, when the ignition timing of the cylinder 101 is calculated to be more on the retarded side than the retarded side permissible timing difference L1 with respect to the reference ignition timing DS, the control device 50 corrects the ignition timing of the cylinder 101 in such a manner that the timing difference on the retarded side of the ignition timing with respect to the reference ignition timing DS coincides with the retarded side permissible timing difference L1. Thus, for the cylinder 101 for which the occurrence of knocking needs to be prevented, the ignition timing can be corrected to the retarded side as much as possible within the permissible timing difference range R, thereby preventing the occurrence of knocking.

[0051] In addition, when the ignition timing of the cylinder 101 is calculated to be more advanced than the allowable timing difference L2 on the advanced side relative to the reference ignition timing DS, the control device 50 corrects the ignition timing of the cylinder 101 in such a manner that the timing difference on the advanced side of the ignition timing relative to the reference ignition timing DS coincides with the allowable timing difference L2 on the advanced side. Thus, the ignition timing is corrected in such a manner that the ignition timing is maintained on the advanced side to the maximum extent within the allowable timing difference range R for the cylinder 101 where no knocking occurs, and a reduction in the output torque of the engine 100 can be suppressed.

[0052] In addition, if Figure 4 As shown in FIG. 1 , the control device 50 sets the cylinder 101b having the second largest retard angle side ignition timing D0b after the maximum retard ignition timing D0a as the reference cylinder 101S. Thus, the control device 50 can suppress the reduction of the output torque of the engine 100 and make the average ignition timing of all cylinders 101 close to the retard angle side, thereby preventing the occurrence of knocking.

[0053] The allowable timing difference range R is set based on at least one of the rotation speed and the load (output torque) of the engine 100 . Thus, the control device 50 can control the ignition timing of each cylinder 101 according to the operating condition of the engine 100 .

[0054] Description of the label

[0055] 50…Control device

[0056] 51…Ignition timing calculation unit

[0057] 53… Reference ignition timing setting unit

[0058] 54…Permissible timing difference range setting unit

[0059] 55…Ignition timing determination unit

[0060] 56…Ignition timing correction unit

[0061] 100…Engine

[0062] 101…Cylinder

[0063] 101S…Standard Cylinder

[0064] DS…Standard ignition timing

[0065] R…Permissible timing difference range

[0066] L1…Allowable timing difference on the lag angle side

[0067] L2…Advance angle side allowable timing difference

Claims

1. A method for controlling an engine, comprising controlling the ignition timing of each cylinder of an engine having at least three cylinders based on an operating condition, wherein: The ignition timing of each cylinder is calculated based on the occurrence or non-occurrence of knock. The ignition timing of any cylinder among the cylinders whose calculated ignition timing is closer to the advanced angle side than the maximum retarded ignition timing on the maximum retarded angle side and closer to the retarded angle side than the maximum advanced angle ignition timing on the maximum advanced angle side is set as a reference ignition timing, The allowable timing difference range is set as a range of allowable timing difference based on the reference ignition timing. determining whether the ignition timing of each cylinder falls within the allowable timing difference range, When it is determined that the ignition timing of each cylinder does not fall within the allowable timing difference range, the ignition timing is corrected so that the timing difference of the ignition timing of the cylinder determined not to fall within the allowable timing difference range with respect to the reference ignition timing falls within the allowable timing difference range.

2. The engine control method according to claim 1, wherein: When the allowable timing difference range is set, setting a retard angle side allowable timing difference as a threshold value on the retard angle side of the allowable timing difference range, setting an allowable timing difference on the advanced angle side as a threshold on the advanced angle side of the allowable timing difference range, When determining whether the ignition timing of each cylinder falls within the allowable timing difference range, determining whether the ignition timing of each cylinder is set to the retarded angle side relative to the reference ignition timing than the retarded angle side allowable timing difference, determining whether the ignition timing of each cylinder is set to the advanced angle side relative to the reference ignition timing than the advanced angle side allowable timing difference, When the ignition timing of the cylinder is set to be closer to the retarded angle side than the retarded angle side permissible timing difference with respect to the reference ignition timing, the ignition timing of the cylinder is corrected in such a manner that the timing difference of the ignition timing of the cylinder on the retarded angle side with respect to the reference ignition timing is less than or equal to the retarded angle side permissible timing difference, When the ignition timing of the cylinder is set to be closer to the advanced angle side than the allowable timing difference on the advanced angle side relative to the base ignition timing, the ignition timing of the cylinder is corrected in such a way that the timing difference on the advanced angle side of the ignition timing of the cylinder relative to the base ignition timing is less than or equal to the allowable timing difference on the advanced angle side.

3. The engine control method according to claim 2, wherein: When the ignition timing of the cylinder is set to be closer to the retarded angle side than the retarded angle side permissible timing difference with respect to the reference ignition timing, the ignition timing of the cylinder is corrected in such a manner that the timing difference of the ignition timing of the cylinder on the retarded angle side with respect to the reference ignition timing is consistent with the retarded angle side permissible timing difference, When the ignition timing of the cylinder is set to be closer to the advanced angle side than the allowable timing difference on the advanced angle side relative to the base ignition timing, the ignition timing of the cylinder is corrected in such a manner that the timing difference on the advanced angle side of the ignition timing of the cylinder relative to the base ignition timing is consistent with the allowable timing difference on the advanced angle side.

4. The engine control method according to any one of claims 1 to 3, wherein: The ignition timing of the cylinder for which the ignition timing at the second largest retard angle side after the most retarded ignition timing is set is set as the reference ignition timing.

5. The engine control method according to any one of claims 1 to 3, wherein: The allowable timing difference range is set based on at least one of a rotation speed and a load of the engine.

6. An engine control device for controlling the ignition timing of each cylinder of an engine having at least three cylinders based on operating conditions, wherein: The engine control device comprises: an ignition timing calculation unit that calculates the ignition timing of each cylinder based on the presence or absence of knocking; a reference ignition timing setting unit that sets, as a reference ignition timing, the ignition timing of any cylinder among the cylinders whose calculated ignition timing is closer to the advanced angle side than the maximum retarded ignition timing on the maximum retarded angle side and closer to the retarded angle side than the maximum advanced angle ignition timing on the maximum advanced angle side; an allowable timing difference range setting unit for setting an allowable timing difference range which is a range of allowable timing difference based on the reference ignition timing; an ignition timing determination unit that determines whether the ignition timing of each cylinder falls within the allowable timing difference range; and The ignition timing correction unit corrects the ignition timing so that the timing difference of the ignition timing of the cylinder determined not to fall within the allowable timing difference range relative to the reference ignition timing falls within the allowable timing difference range when it is determined that the ignition timing of each cylinder does not fall within the allowable timing difference range.

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