Ignition timing control method and apparatus for an internal combustion engine

Abstract

In an internal combustion engine equipped with a variable compression ratio mechanism, abnormal noises caused by combustion pressure in a specific low-load operating range are appropriately suppressed by controlling the advance angle limit of the ignition timing. [Solution] The noise suppression advance ignition limit value calculation unit 101 includes a map search unit 102, an advance ignition limit value selection unit 103, a change rate limit unit 104, a change rate limit determination unit 105, and a dummy value output unit 106. When the region determination unit 107 determines that the operating point is within the noise region, it outputs the noise suppression advance ignition limit value OPDADV via the select-low unit 110. The final ignition timing is limited to the retarded side of the MBT point by this advance ignition limit value. The map search unit 102 includes an advance ignition limit value map for each engine state label ETDST corresponding to the compression ratio. When the compression ratio is high, the ignition timing is limited to the retarded side even more.

Description

Technical Field

[0001] This invention relates to an ignition timing control of an internal combustion engine that limits the final ignition timing with an advance limit value on the retard side from the MBT point in order to suppress abnormal noise caused by combustion pressure generated in a specific low load operation region in an internal combustion engine equipped with a variable compression ratio mechanism.

Background Art

[0002] Patent Document 1 discloses retarding the ignition timing on the condition that, for example, after warm-up when the operating point (rotation speed and load) of the internal combustion engine is within a specific operating region in order to suppress abnormal noise generated in a specific operating region of the internal combustion engine.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In an internal combustion engine equipped with a variable compression ratio mechanism, abnormal noise may be generated due to combustion pressure in a specific low load operation region. In such a case, if the retard amount for suppressing abnormal noise is set constant without considering the compression ratio for the ignition timing of a certain operating point included in the specific low load operation region, the abnormal noise cannot be sufficiently reduced when the compression ratio is high, and there is a concern that an excessive retard amount may cause misfire when the compression ratio is low.

Means for Solving the Problems

[0005] This invention is an ignition timing control method for an internal combustion engine that limits the final ignition timing with an advance limit value on the retard side from the MBT point in order to suppress abnormal noise caused by combustion pressure generated in a specific low load operation region in an internal combustion engine equipped with a variable compression ratio mechanism, Determine whether the rotational speed and load of the internal combustion engine are within the above-mentioned specific low-load operating range. The compression ratio is determined by the above variable compression ratio mechanism, If the operating range is within the specific low-load operating range described above, the advance limit value is set such that the higher the compression ratio, the more retarded the ignition timing becomes. This advance limit value restricts the final ignition timing. [Effects of the Invention]

[0006] According to this invention, in a specific low-load operating range where abnormal noise is a problem, the advance limit value is set such that the higher the compression ratio, the more retarded the ignition timing becomes. The final ignition timing is then limited accordingly, thereby sufficiently reducing abnormal noise even under high compression ratio conditions, and avoiding stalls or misfires due to excessive ignition timing retardation under low compression ratio conditions. [Brief explanation of the drawing]

[0007] [Figure 1] Diagram illustrating the configuration of a series hybrid vehicle. [Figure 2] A diagram illustrating the configuration of an internal combustion engine in one embodiment. [Figure 3] Diagram illustrating the mechanism of abnormal noise generation. [Figure 4] A block diagram of one embodiment, which includes an advance ignition timing limit value map for each compression ratio. [Figure 5] A modified block diagram showing an advance limit value map for each engine state label. [Figure 6] This characteristic diagram shows the operating range where abnormal noise is a problem, and also illustrates examples of transitions in the operating point within this abnormal noise range. [Figure 7] A time chart showing the operation of one embodiment with respect to the transition of the operating point in Figure 6. [Figure 8] A time chart showing the operation of a comparative example without advance ignition limit control. [Figure 9] A time chart showing the operation of a comparative example where advance angle limit control does not consider the compression ratio. [Figure 10]A time chart showing the operation of one embodiment when transitioning to idle operation. [Figure 11] A characteristic diagram showing an example of the transition of the operating point into the abnormal noise range as the rotational speed increases. [Figure 12] A time chart showing the operation of one embodiment with respect to the transition of the operating point in Figure 11. [Modes for carrying out the invention]

[0008] The following describes an embodiment in which this invention is applied to an internal combustion engine for power generation in a series hybrid vehicle. Figure 1 schematically shows the configuration of a series hybrid vehicle. The series hybrid vehicle is composed of a power generation motor generator 1 that mainly operates as a generator, an internal combustion engine 2 used as a power generation internal combustion engine that drives the power generation motor generator 1 according to power demands, a drive motor generator 4 that mainly operates as a motor to drive the drive wheels 3, and a battery 5 that temporarily stores the generated electricity. The electricity obtained by the internal combustion engine 2 driving the power generation motor generator 1 is stored in the battery 5 via an inverter device (not shown). The drive motor generator 4 is driven and controlled using the power from the battery 5. The electricity generated during regeneration by the drive motor generator 4 is also stored in the battery 5 via an inverter device (not shown). In the illustrated example, the motor generator 1 and the internal combustion engine 2 are linked via a gear train, but they may be directly connected to each other.

[0009] The operation of motor generators 1 and 4, the charging and discharging of battery 5, and the operation of internal combustion engine 2 are controlled by controller 6. Controller 6 consists of multiple controllers connected to each other so that they can communicate with one another, including motor controller 7 which controls motor generators 1 and 4, engine controller 8 which controls internal combustion engine 2, and battery controller 9 which manages battery 5. Information such as the opening of the accelerator pedal (not shown) and vehicle speed is input to controller 6. Battery controller 9 also determines the state of charge (SOC) of battery 5 based on its voltage and current and manages its charging and discharging.

[0010] As driving modes of such a series hybrid vehicle, there are an EV driving mode in which the vehicle runs using the power of the battery 5 without combustion operation (i.e., power generation or charging) of the internal combustion engine 2, and a HEV driving mode in which the vehicle runs while generating power by the combustion operation of the internal combustion engine 2. The battery controller 9 manages charging and discharging of the battery 5 so that the SOC of the battery 5 is maintained between a predetermined SOC upper limit target value and a SOC lower limit target value. For example, when the SOC decreases due to EV driving and falls below the SOC lower limit target value, the internal combustion engine 2 is started via the engine controller 8 and power generation is performed. The power generation by the internal combustion engine 2 ends, for example, when the SOC approaches the SOC upper limit target value. During this power generation, usually, the internal combustion engine 2 is operated at some specific operating points (combinations of torque and rotational speed) where the fuel efficiency is the best.

[0011] Also, when the required driving force of the vehicle is high, since the required driving force of the vehicle cannot be covered with the power that can be supplied from the battery 5, the vehicle enters the HEV driving mode and power generation is performed by the internal combustion engine 2. At this time, in order to increase the power generation output, for example, the internal combustion engine 2 is operated at some specific operating points where the rotational speed is higher than the best fuel efficiency point.

[0012] FIG. 2 shows an example of the system configuration of the internal combustion engine 2. This internal combustion engine 2 is, for example, a spark ignition type internal combustion engine with a turbocharger (so-called gasoline engine) of a four-stroke cycle provided with a variable compression ratio mechanism 12 using a complex link type piston crank mechanism.

[0013] A pair of intake valves 14 and a pair of exhaust valves 15 are arranged on the ceiling wall surface of the combustion chamber 13, and a spark plug 16 is arranged at the central portion surrounded by these intake valves 14 and exhaust valves 15. A cylinder pressure sensor 25 for detecting the cylinder pressure is provided in the combustion chamber 13.

[0014] In the intake port 17 opened and closed by the intake valve 14, fuel injection valves 18 for injecting fuel toward the intake valve 14 are arranged for each cylinder. The fuel injection valve 18 is an electromagnetic or piezoelectric injection valve that opens when a drive pulse signal is applied, and injects an amount of fuel substantially proportional to the pulse width of the drive pulse signal. Note that a configuration of direct injection into the cylinder may also be employed.

[0015] An electronically controlled throttle valve 21 whose opening degree is controlled by a control signal from the engine controller 8 is provided upstream of the collector portion 19a of the intake passage 19 connected to the intake port 17. Further upstream thereof, a compressor 22A of a turbocharger 22 is disposed. An air flow meter 23 for detecting the intake air amount and an air cleaner 24 are disposed upstream of the compressor 22A. The collector portion 19a incorporates a heat exchanger, i.e., a water-cooled intercooler 26, for cooling the supercharged intake air by heat exchange with cooling water. An intercooler water temperature sensor 36 is provided in the intercooler 26 to detect the temperature of the cooling water flowing through the intercooler 26. An intake air temperature sensor 37 is provided on the outlet side of the intake air of the intercooler 26 to detect the temperature of the intake air that has passed through the intercooler 26. Further, separately from the intercooler water temperature sensor 36, a coolant temperature sensor 38 for detecting the temperature of the cooling water flowing through the water jacket of the internal combustion engine 2 is provided at an appropriate position such as the water jacket. Further, a knock sensor 39 for detecting knocking vibration is provided at an appropriate position on the cylinder block of the internal combustion engine 2.

[0016] The turbine 22B of the turbocharger 22 disposed in the exhaust passage 31 includes a wastegate valve 32 whose opening degree is controlled by a control signal from the engine controller 8. Catalytic devices 33, 34 are disposed downstream of the turbine 22B in the exhaust passage 31, and a muffler 35 is disposed further downstream.

[0017] The variable compression ratio mechanism 12 utilizes a known double-link piston-crank mechanism described in Japanese Patent Publication No. 2014-159770 and Japanese Patent Publication No. 2005-127200, and comprises a lower link 42 rotatably attached to the crank pin 41 of the crankshaft, an upper link 43 connecting an upper pin 48 at one end of the lower link 42 to the piston pin 49 of the piston 40, a control shaft 44 rotatably supported on the engine body side, a control link 45 connecting a control pin 50 at the other end of the lower link 42 to the control shaft 44, and an electric actuator 46 that controls the rotational position of the control shaft 44. The control shaft 44 has an eccentric shaft portion, and the base end of the control link 45 is supported on this eccentric shaft portion so as to be rotatable, i.e., swingable. In this variable compression ratio mechanism 12, the posture of each link changes according to the rotational position of the control shaft 44, and the top dead center position of the piston 40 changes up and down, thereby changing the mechanical compression ratio. The mechanical compression ratio is determined by the rotational position of the control shaft 44, which is moved by the electric actuator 46. This rotational position is simultaneously detected as the actual value of the mechanical compression ratio, i.e., the actual compression ratio. In other words, the electric actuator 46 itself also functions as an actual compression ratio sensor. In such a variable compression ratio mechanism 12, the actual compression ratio can be detected even when the crankshaft is stationary, i.e., in a non-rotating state.

[0018] The engine controller 8 receives detection signals from various sensors, including the in-cylinder pressure sensor 25, air flow meter 23, intercooler water temperature sensor 36, coolant temperature sensor 38, knock sensor 39, intake air temperature sensor 37, and actual compression ratio sensor (electric actuator 46), as well as from a crank angle sensor 52 for detecting engine rotational speed, an accelerator pedal opening sensor 53 for detecting the amount the driver depresses the accelerator pedal, a boost pressure sensor 54 for detecting boost pressure, and an air-fuel ratio sensor 55 located in the exhaust passage 31. Based on these detection signals, the engine controller 8 optimally controls the fuel injection amount and timing by the fuel injector 18, the ignition timing by the spark plug 16, the mechanical compression ratio by the variable compression ratio mechanism 12, the opening of the throttle valve 21, the opening of the wastegate valve 32, and so on.

[0019] Here, the mechanical compression ratio by the variable compression ratio mechanism 12 is controlled according to a target compression ratio set for each operating point of the internal combustion engine 2. This target air-fuel ratio generally tends to be lower as the load increases. Furthermore, even at the same operating point, the target compression ratio can differ depending on various conditions such as coolant temperature and intake air temperature.

[0020] Furthermore, regarding the ignition timing, a basic ignition timing ADV0 corresponding to the MBT point is defined for each operating point, and the final ignition timing is set by applying an appropriate correction to this basic ignition timing ADV0. This final ignition timing is then limited by an advance limit value that is retarded compared to the basic ignition timing ADV0, as will be described later, and it cannot advance beyond this advance limit value, i.e., approach the MBT point (basic ignition timing ADV0). In this invention, one of these advance limit values ​​is set to suppress abnormal noise caused by combustion pressure occurring in a specific low-load operating range.

[0021] Next, with reference to Figure 3, the mechanism of noise generation in the internal combustion engine 2 of the above embodiment will be explained. Figure 3 schematically shows the crankshaft 71 of an inline 3-cylinder internal combustion engine as an example, and this crankshaft 71 is supported by four main journal sections 72-75 at the bottom of the cylinder block. The rear end of the crankshaft 71 is equipped with a relatively large mass section 76 such as a flywheel, and the front end of the crankshaft 71 is equipped with a relatively small mass section 77 such as a crank pulley. In this configuration, the combustion pressure of cylinder #1, indicated by arrow Pe, causes the front end of the crankshaft 71 to bend and deform radially, resulting in a strong radial collision between the front end of the crankshaft 71 and the #1 main journal section 72, producing a knocking sound. Since this knocking sound is mainly due to the combustion pressure of cylinder #1, it occurs every 720°CA, resulting in an abnormal noise with a peak in the 0.5th rotation frequency range. This abnormal noise occurs in a specific abnormal noise region A shown in Figure 6. The abnormal noise region A is a medium-speed, low-load operating range that includes at least around 2000 rpm to 3000 rpm, and the range varies slightly depending on the compression ratio. The abnormal noise consists of the sound of the crankshaft 71 striking the #1 main journal section 72, resulting in a "dada-da" sound, which the applicant refers to as the "dada-da sound." It is thought that this abnormal noise is influenced by the increased inertial mass associated with the crankpin due to the double-link piston-crank mechanism that constitutes the variable compression ratio mechanism 12.

[0022] Next, based on the block diagram in Figure 4, the setting of the ignition timing advance limit value for noise suppression (this is called advance limit control) will be explained. Figure 4 shows one embodiment equipped with an advance limit value map for each compression ratio. The noise suppression advance limit value calculation unit 101 included in the ignition timing control system has a map search unit 102, an advance limit value selection unit 103, a change rate limit unit 104, a change rate limit determination unit 105, and a dummy value output unit 106, and outputs the noise suppression advance limit value OPDADV.

[0023] In addition to the noise suppression advance limit value calculation unit 101, a trace knock advance limit value calculation unit 109 is provided to calculate a trace knock advance limit value ADVTRMBT to maintain knocking at a weak level, also known as a trace knock state. The advance limit value OPDADV output by the noise suppression advance limit value calculation unit 101 and the advance limit value ADVTRMBT output by the trace knock advance limit value calculation unit 109 are compared with each other in the select-low unit 110, and the smaller value (i.e., the value that is relatively retarded) is output as the advance limit value. The final ignition timing is restricted to the retarded side of the MBT point (basic ignition timing ADV0) by this advance limit value. Here, the advance limit value is expressed as a crank angle with the direction from top dead center of compression toward the advance side being positive, similar to a general "advance value".

[0024] The noise suppression advance limit value calculation unit 101 receives information on the compression ratio, torque (i.e., load), and rotational speed at that time. The map search unit 102 has multiple advance limit value maps MAP, each of which advance limit value OPDADV corresponding to the rotational speed and torque of the internal combustion engine 2 is assigned to a number of representative compression ratios. The map search unit 102 uses these multiple advance limit value maps MAP to search for advance limit values ​​corresponding to the compression ratio, rotational speed, and torque. Basically, the multiple advance limit value maps MAP for each compression ratio have the characteristic that, for the same operating point, the higher the compression ratio, the more retarded the advance limit value OPDADV becomes.

[0025] The compression ratio, torque, and rotational speed information are input to the region determination unit 107 in parallel. The region determination unit 107 determines whether the rotational speed and torque are within the abnormal noise region A shown in Figure 6, which is predetermined for each compression ratio, and outputs a "dada-da" noise control flag if they are within the abnormal noise region A. The prohibition condition determination unit 108 determines whether the conditions for prohibiting advance ignition limit control to suppress abnormal noise are met, and the idle flag and fuel cut flag are input to indicate the prohibition conditions. During idling when the idle flag is on, and immediately after fuel cut recovery when the fuel cut flag has reversed from on to off, it is desirable to prohibit advance ignition limit control to avoid misfires or stalls. If the conditions are not prohibition conditions, the "dada-da" noise control flag is output to the abnormal noise suppression advance ignition limit value calculation unit 101 via the prohibition condition determination unit 108, and if the conditions are prohibition conditions, the "dada-da" noise control flag is not output.

[0026] The "dada-da" sound control flag is input to the advance limit value selection unit 103 with an appropriate delay. If the "dada-da" sound control flag is on, the advance limit value selection unit 103 selects the advance limit value OPDADV from the map search unit 102 and outputs it to the rate of change limit unit 104. Since this advance limit value OPDADV changes in steps when the advance limit value map MAP is switched in accordance with the change in compression ratio, the rate of change limit unit 104 limits the rate of change before it is output to the select-low unit 110.

[0027] When the dash-dada-da sound control flag is off, the advance angle limit value selection unit 103 selects and outputs the advance angle limit value ADVTRMBT calculated by the trace knock advance angle limit value calculation unit 109.

[0028] The rate of change limiting determination unit 105 determines whether the rate of change limiting unit 104 is in the process of limiting the rate of change. The dummy value output unit 106 outputs a dummy value to the select row unit 110 that is a sufficiently large value (e.g., 100°CA) exceeding the MBT point as the advance angle limit value if the daddada sound control flag is off and the rate of change limiting unit 104 is not limiting the rate of change. Under the condition that this dummy value is output, the output of the select row unit 110 becomes the advance angle limit value ADVTRMBT calculated by the trace knock advance angle limit value calculation unit 109. In other words, advance angle limit control is not performed.

[0029] Thus, in the above embodiment, the advance limit value for the ignition timing when the operating point (torque / rotational speed) is within the abnormal noise region A is set according to the compression ratio at that time. Therefore, it is possible to achieve ignition timing advance limit (in other words, retardation control from the basic ignition timing ADV0) in an appropriate manner.

[0030] Next, Figure 5 is a block diagram of a modified example that includes an advance ignition limit value map for each engine state label. In order to efficiently consolidate the control of the internal combustion engine 2, which includes various types of control, the current state of the internal combustion engine 2 may be indicated by multiple engine state labels. For example, in one example, there are multiple engine state labels ETDST, such as No. 1 to No. 20, and each of these engine state labels ETDST is defined by conditions that include at least the intake air temperature and water temperature of the internal combustion engine 2, and each is assigned a target compression ratio. In other words, the engine state label ETDST corresponds to a parameter that discretely indicates the compression ratio. The map search unit 102 then includes multiple advance ignition limit value maps MAP, each of which an advance ignition limit value OPDADV corresponding to the rotational speed and torque of the internal combustion engine 2 is assigned to each of these engine state labels ETDST.

[0031] Therefore, in the example shown in Figure 5, the engine state label ETDST information is input to the noise suppression advance ignition limit value calculation unit 101, rather than the compression ratio itself. The same applies to the region determination unit 107.

[0032] Aside from the points mentioned above, the explanation is the same as that given for Figure 4, so we will omit further explanation. In this configuration of Figure 5 as well, the advance ignition timing limit value when the operating point (torque and rotational speed) is within the abnormal noise region A will be set according to the compression ratio at that time. Therefore, it is possible to achieve ignition timing advance limiting in a way that is neither excessive nor insufficient.

[0033] Figure 7 is a time chart showing the operation of one embodiment, and from top to bottom, it shows the changes in (a) the rotational speed of the internal combustion engine, (b) the torque of the internal combustion engine, (c) the compression ratio, (d) the ignition timing (final ignition timing), (e) the magnitude of the abnormal noise (rattling sound), and (f) the rattling sound control flag. Note that the ignition timing in column (d) is more advanced towards the top of the figure. This example corresponds to the case where the operating point transitions from point P1 to point P2 in Figure 6. In other words, it is an example where the operating state at point P1 transitions to point P2, which is in the abnormal noise region A, due to a decrease in torque (load), and at time t1, it is in the abnormal noise region A.

[0034] Furthermore, Figure 8 is a time chart of the comparative example, showing the operation when advance limit control is not performed. When advance limit control is not performed, as shown in the comparative example in Figure 8, the noise in column (e) increases as the torque decreases and the system enters the noise region A at time t1. Then, at time t2, the noise increases further as the compression ratio increases.

[0035] In contrast, in one embodiment shown in Figure 7, the rattling noise control flag is turned on at time t1, and the final ignition timing is limited by the advance ignition timing limit value OPDADV for noise suppression. In other words, the final ignition timing is retarded compared to the ignition timing characteristics in Figure 8. Furthermore, as the compression ratio increases at time t2, even at the same operating point (point P2 in Figure 6), the advance ignition timing limit value OPDADV for noise suppression becomes retarded as the compression ratio changes, and the final ignition timing is further retarded. Therefore, as shown in column (e) of Figure 7, the noise is appropriately suppressed.

[0036] Time t2 corresponds to the timing when the engine state label ETDST switches due to, for example, a rise in coolant temperature (e.g., from No. 2 to No. 3). Here, the compression ratio increases while remaining at the same operating point (point P2 in Figure 6) in accordance with the change in the engine state label ETDST. Therefore, in the example in Figure 4, the advance limit value map MAP for each compression ratio is switched in accordance with the change in compression ratio at time t2, and in the example in Figure 5, the advance limit value map MAP set for each engine state label ETDST is switched at time t2.

[0037] Figure 9 is a time chart showing the operation of a comparative example where advance ignition limit control does not consider the compression ratio. In this comparative example, even if the compression ratio at the same operating point increases at time t2, the advance ignition limit value does not change, and the same final ignition timing is maintained. Therefore, abnormal noises after time t2 cannot be sufficiently suppressed.

[0038] Although not shown in the diagram, if the advance ignition timing limit is set assuming a high compression ratio after time t2, the ignition timing may become excessively retarded under low compression ratio conditions before time t2, potentially causing misfires or stalls.

[0039] Next, we will explain an example of operation when the conditions for prohibiting advance ignition timing limit control are met. Figure 10 is a time chart showing the operation of one embodiment when the engine transitions to idle operation while running in the abnormal noise region A, and column (g) shows the idle flag associated with the on / off state of the idle switch. In this example of Figure 10, the operation is the same as in Figure 7 described above until time t3, when the operating point falls within the abnormal noise region A due to the decrease in torque, the rattling noise control flag is turned on, and advance ignition timing limit control begins. Then, at time t2, as the compression ratio increases (engine state label ETDST changes), the advance ignition timing limit value OPDADV for suppressing abnormal noise is changed, and the final ignition timing is restricted to the retarded side.

[0040] In this example, at time t3, the engine enters idle mode, and the idle flag is turned on. As a result, the rattling noise control flag is turned off, and advance ignition timing limit control is disabled. Note that, as shown in column (d), the basic ignition timing ADV0 during idle mode is generally set to be relatively retarded, making abnormal noises (rattling noises) less likely to occur.

[0041] Figures 11 and 12 show examples of operation when the rotational speed increases while the torque remains constant, causing the system to enter the abnormal noise region A. Specifically, as shown in Figure 11, this is an example where the operating point transitions from point P11 to point P12, resulting in the system entering the abnormal noise region A.

[0042] As shown in Figure 12, at time t1, the rattling noise control flag is turned on, and advance ignition timing limit control begins. This suppresses abnormal noises that are likely to occur in the abnormal noise region A, similar to the case in Figure 7 described above. Furthermore, at time t2, for example, the engine state label ETDST changes due to an increase in coolant temperature, and the compression ratio increases. In response to this, the advance ignition timing limit value OPDADV for abnormal noise suppression is changed, and the final ignition timing is restricted to the retarded side. This ensures that abnormal noises are reliably suppressed even at high compression ratios.

[0043] Although one embodiment of the present invention has been described in detail above, the present invention is not limited to the above embodiment, and various modifications are possible. For example, the internal combustion engine in the above embodiment is equipped with a variable compression ratio mechanism that utilizes a double-link piston crank mechanism including a lower link, an upper link, and a control link, but other known variable compression ratio mechanisms may be used as the variable compression ratio mechanism. Furthermore, the internal combustion engine may be a non-supercharged internal combustion engine.

[0044] Furthermore, although the above embodiments described an example of application to a series hybrid vehicle, the present invention is not limited to internal combustion engines for power generation in series hybrid vehicles, but can also be applied to general internal combustion engines used as a power source for vehicles. [Explanation of Symbols]

[0045] 1…Motor Generator 2…Internal combustion engine 8…Engine controller 12... Variable compression ratio mechanism 16... Spark plug 18…Fuel injector 21... Throttle valve 101... Calculation unit for calculating advance angle limit value for noise suppression 102...Map Search Section

Claims

1. An ignition timing control method for an internal combustion engine equipped with a variable compression ratio mechanism, wherein the final ignition timing is limited by an advance limit value that is retarded beyond the MBT point in order to suppress abnormal noise caused by combustion pressure occurring in a specific low-load operating range. Determine whether the rotational speed and load of the internal combustion engine are within the above-mentioned specific low-load operating range. The compression ratio is determined by the above variable compression ratio mechanism, If the operating range is within the specific low-load operating range described above, the advance limit value is set such that the higher the compression ratio, the more retarded the ignition timing becomes. This advance limit value restricts the final ignition timing. A method for controlling the ignition timing of an internal combustion engine.

2. For each of several representative compression ratios, multiple advance limit value maps are created, each assigning an advance limit value corresponding to the rotational speed and load of the internal combustion engine. This advance angle limit value map is used to search for advance angle limit values ​​corresponding to the compression ratio, rotational speed, and load. The ignition timing control method for an internal combustion engine according to claim 1.

3. It has multiple engine condition labels, each defined by conditions including at least the intake air temperature and water temperature of the internal combustion engine, and each assigned a target compression ratio. The above advance ignition timing limit map is created for each of the above engine state labels, which corresponds to the compression ratio. The ignition timing control method for an internal combustion engine according to claim 2.

4. During idle in an internal combustion engine, the final ignition timing is not limited by the above advance limit value. The ignition timing control method for an internal combustion engine according to claim 1.

5. During fuel cut-off recovery in an internal combustion engine, the final ignition timing is not limited by the above advance limit value. The ignition timing control method for an internal combustion engine according to claim 1.

6. The above variable compression ratio mechanism consists of a double-link piston crank mechanism including a lower link, an upper link, and a control link. The above-mentioned abnormal noise is a rotational 0.5th-order noise caused by radial vibration of the crankshaft at the end of the crankshaft. The ignition timing control method for an internal combustion engine according to claim 1.

7. The above internal combustion engine is an internal combustion engine used for power generation in a series hybrid vehicle. The ignition timing control method for an internal combustion engine according to claim 1.

8. An ignition timing control device for an internal combustion engine equipped with a variable compression ratio mechanism, which limits the final ignition timing to an advance limit value that is retarded beyond the MBT point in order to suppress abnormal noise caused by combustion pressure occurring in a specific low-load operating range. This ignition timing control device is Determine whether the rotational speed and load of the internal combustion engine are within the above-mentioned specific low-load operating range. The compression ratio is determined by the above variable compression ratio mechanism, If the operating range is within the specific low-load operating range described above, the advance limit value is set such that the higher the compression ratio, the more retarded the ignition timing becomes. This advance limit value restricts the final ignition timing. Ignition timing control device for internal combustion engines.

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