Ignition timing control device for internal combustion engine

Abstract

To appropriately set a correction amount of ignition timing for an internal combustion engine that includes a valve characteristic variable mechanism, a supercharger and a waste gate valve.SOLUTION: An internal combustion engine ignition timing control apparatus is applied to an internal combustion engine that includes: a valve characteristic variable mechanism for changing an open-close characteristics of at least one of intake- and exhaust valves; a supercharger; and a waste gate valve. The ignition timing control apparatus includes an ignition timing correction amount calculation part for calculating a correction amount of ignition timing against basic ignition timing that is preset as basis for ignition timing for the engine by using: base boost pressure in the engine when the valve characteristic variable mechanism is in a base state preset for the engine as a reference state applicable when open-close characteristics of the intake- and exhaust valves are changed; and present boost pressure that is determined on the basis of the present state of the valve characteristic variable mechanism and present state of the waste gate valve.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an ignition timing control device for an internal combustion engine. [Background technology]

[0002] Conventionally, internal combustion engines have been known that employ a variable valve mechanism for the purpose of improving fuel economy by reducing pumping losses in response to the introduction of internal exhaust gas recirculation (EGR). When the variable valve mechanism is activated, the amount of internal EGR may change. Because changes in the amount of internal EGR affect the combustion state in the internal combustion engine, it is known that the ignition timing of the spark plug is corrected depending on the operating status of the variable valve mechanism (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-248983 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, an internal combustion engine may be equipped with a wastegate valve in addition to a turbocharger. When the wastegate valve transitions to a closed state, back pressure in the internal combustion engine increases. When back pressure in the internal combustion engine increases, the amount of internal EGR increases. When the amount of internal EGR increases, the compression end temperature during combustion increases, making knocking more likely to occur. Correcting the ignition timing is effective in suppressing knocking. However, Patent Document 1 does not take into account cases where the internal combustion engine is equipped with a turbocharger and a wastegate valve. Therefore, Patent Document 1 leaves room for improvement in setting the amount of ignition timing correction in an internal combustion engine equipped with a turbocharger and a wastegate valve.

[0005] Therefore, an object of the invention disclosed in this specification is to appropriately set the correction amount of the ignition timing in an internal combustion engine equipped with a valve characteristic variable mechanism, a supercharger, and a wastegate valve. [Means for solving the problem]

[0006] The above object is achieved by an ignition timing control device applied to an internal combustion engine including a variable valve characteristic mechanism that changes the opening / closing characteristics of at least one of an intake valve and an exhaust valve, and a supercharger and a wastegate valve, the ignition timing control device including an ignition timing correction amount calculation unit that calculates a correction amount of ignition timing relative to a basic ignition timing that is preset as a basic ignition timing in the internal combustion engine, using a base supercharging pressure in the internal combustion engine when the variable valve characteristic mechanism is in a base state that is preset in the internal combustion engine as a reference state when the opening / closing characteristics of the intake valve and the exhaust valve are changed, and a current supercharging pressure that is determined depending on the current state of the variable valve characteristic mechanism and the current state of the wastegate valve.

[0007] In the ignition timing control device for an internal combustion engine having the above configuration, the ignition timing correction amount calculation unit can be configured to calculate the correction amount of the ignition timing using a difference value between a base intake manifold pressure that reflects the base supercharging pressure and a current intake manifold pressure that reflects the current supercharging pressure.

[0008] Furthermore, in the ignition timing control device for an internal combustion engine having the above configuration, the ignition timing correction amount calculation unit can calculate the correction amount of the ignition timing using a correction coefficient calculated based on the difference value, an engine load, and a rotation speed of the internal combustion engine. [Effects of the Invention]

[0009] The invention disclosed in this specification, together with the variable valve characteristics mechanism, can appropriately set the correction amount of the ignition timing in an internal combustion engine equipped with a supercharger and a wastegate valve. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram showing the general configuration of an internal combustion engine equipped with an ignition timing control device according to an embodiment. [Figure 2] FIG. 2 is a block diagram showing a schematic configuration of an electronic control unit that functions as an ignition timing control device in the embodiment. [Figure 3] FIG. 3 is an example of a map for calculating the base supercharging pressure in the ignition timing control device of the embodiment. [Figure 4] FIG. 4 is an example of a map for calculating the difference between the current intake pipe pressure and the base intake pipe pressure in the ignition timing control device of the embodiment. [Figure 5] FIG. 5 is an example of a map for calculating a correction coefficient used to calculate the ignition timing correction amount in the ignition timing control device of the embodiment. [Figure 6] FIG. 6 is an example of a graph showing an ignition timing correction amount calculated based on the difference between the current intake pipe pressure and the base intake pipe pressure and the correction coefficient in the ignition timing control device of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions and proportions of the various parts in the drawings may not be exactly the same as those in reality. In addition, some details may be omitted in the drawings.

[0012] (Embodiment) [Configuration of an internal combustion engine] First, a schematic configuration of an internal combustion engine 100 equipped with an ECU (Electronic Control Unit) 40 that functions as an ignition timing control device of the embodiment will be described with reference to Figure 1. The internal combustion engine 100 uses gasoline as fuel, but can use conventionally known gasoline substitute fuels such as ethanol and natural gas instead of gasoline.

[0013] The internal combustion engine 100 has a plurality of cylinders 2 in a cylinder block 1a (only one cylinder 2 is shown in FIG. 1). A piston 3 is slidably housed in each cylinder 2, and a combustion chamber 2a is formed between the piston 3 and a cylinder head 1b disposed above the cylinder block 1a. The piston 3 is connected to a crankshaft 5 via a connecting rod 4. An injector 6 that injects fuel into the cylinder and a spark plug 7 are provided in the combustion chamber 2a. The fuel injected from the injector 6 is mixed with air in the combustion chamber 2a and ignited by the spark plug 7. The ignited mixture burns and explodes, pushing the piston 3 downward. The pushed-down piston 3 transmits the explosive force to the crankshaft 5 via the connecting rod 4, causing the crankshaft 5 to rotate. The injector 6 may be provided in an intake pipe 10 near the combustion chamber 2a.

[0014] The internal combustion engine 100 is provided with an intake port 8 and an exhaust port 9 facing the combustion chamber 2a, and an intake pipe 10 forming an intake passage is connected to the intake port 8, and an exhaust pipe 11 forming an exhaust passage is connected to the exhaust port 9.

[0015] The intake pipe 10 is provided with, in order from the upstream side of the intake air flow, an air cleaner 12, an air flow meter 13, a compressor 14a of a turbocharger 14 serving as a supercharger, an intercooler 15, a boost pressure sensor 16, a throttle valve 17, and an intake manifold 18. The throttle valve 17 is provided with a throttle opening sensor 17a. The air flow meter 13 detects the amount of air flowing through the intake pipe 10. The boost pressure sensor 16 detects the boost pressure of the air being sent into the combustion chamber 2a. The boost pressure detected by the boost pressure sensor 16 is used as the current boost pressure to calculate the ignition timing correction amount. The calculation of the ignition timing correction amount will be described in detail later. The throttle valve 17 adjusts the amount of air being sent into the combustion chamber 2a. The throttle opening sensor 17a detects the opening of the throttle valve 17.

[0016] The intake pipe 10 branches at an intake manifold 18 and is connected to the intake ports 8 of each cylinder.

[0017] The exhaust pipe 11 is provided with an exhaust manifold 20, a turbine 14b of the turbocharger 14, and a catalyst 21, in that order from the upstream side of the exhaust flow. The turbine 14b is connected to the compressor 14a by a rotating shaft and is rotated by gas discharged from the combustion chamber 2a through the exhaust port 9. Rotation of the turbine 14b rotates the compressor 14a, supercharging the intake air. The catalyst 21 purifies the exhaust gas. The exhaust pipe 11 is provided with an exhaust bypass passage 60 that bypasses the turbine 14b. The exhaust bypass passage 60 is provided with a wastegate valve (hereinafter referred to as "WGV") 61 that opens and closes the exhaust bypass passage 60. The WGV 61 is driven to open and close by an actuator 62 connected to a vacuum pump 63 that generates negative pressure. The WGV 61 adjusts the supercharging pressure of the turbocharger 14. Specifically, when supercharging is required, the WGV 61 closes the exhaust bypass passage 60 and guides the exhaust gas to the turbine 14b. When the WGV 61 operates to the closing side, the back pressure in the internal combustion engine 100 increases.

[0018] The internal combustion engine 100 is equipped with an intake valve 23 that opens and closes an intake port 8, and an exhaust valve 24 that opens and closes an exhaust port 9. The intake valve 23 and the exhaust valve 24 open and close in accordance with the rotation of an intake camshaft and an exhaust camshaft (not shown) that are drivingly connected to the crankshaft 5. As a result, the intake valve 23 and the exhaust valve 24 are driven to open and close at predetermined timing in synchronization with the rotation of the crankshaft 5 and in response to the reciprocating movement of each piston 3. The internal combustion engine 100 is equipped with an intake VVT mechanism 25a, which is a variable valve mechanism that variably sets the valve timing, which is the opening and closing timing of the intake valve 23, and an exhaust VVT mechanism 25b, which is a variable valve mechanism that variably sets the valve timing, which is the opening and closing timing of the exhaust valve 24. The intake VVT mechanism 25a and the exhaust VVT mechanism 25b are included in a variable valve characteristic mechanism 25 (see FIG. 2).

[0019] The ECU 40 includes a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), a storage device, etc. The ECU 40 controls the internal combustion engine 100 by executing programs stored in the ROM or the storage device. In this embodiment, the ECU 40 functions as an engine load acquisition unit 41, an engine speed acquisition unit 42, a WGV control unit 43, and a valve characteristic setting unit 44. The ECU 40 also functions as a current supercharging pressure acquisition unit 45, a current intake pipe pressure acquisition unit 46, a base supercharging pressure acquisition unit 47, a base intake pipe pressure acquisition unit 48, a difference value acquisition unit 49, a correction coefficient acquisition unit 50, and an ignition timing correction amount calculation unit 51.

[0020] The engine load obtaining unit 41 obtains the engine load KL based on the intake air amount obtained by the air flow meter 13 .

[0021] The engine speed acquisition unit 42 acquires the rotation speed of the crankshaft 5, that is, the engine speed NE, based on the detection value of the crank angle sensor 70.

[0022] The WGV control unit 43 controls the actuator 62 that operates the WGV 61 based on the detected value of the accelerator pedal opening sensor 71 and the engine speed NE acquired by the engine speed acquisition unit 42 .

[0023] The valve characteristics setting unit 44 sets the state of the valve characteristics variable mechanism 25 based on the engine load KL acquired by the engine load acquisition unit 41 and the engine speed NE acquired by the engine speed acquisition unit 42 .

[0024] The current supercharging pressure acquisition unit 45 acquires the current supercharging pressure pcmsm based on the detected value of the supercharging pressure sensor 16. The current supercharging pressure pcmsm changes depending on the operating state of the turbocharger .

[0025] The current intake manifold pressure acquisition unit 46 acquires the current intake manifold pressure pmsm using an air model that uses the current boost pressure pcmsm acquired by the current boost pressure acquisition unit 45. That is, the current intake manifold pressure acquisition unit 46 uses the current boost pressure pcmsm as an argument for acquiring the current intake manifold pressure pmsm. The air model also uses information corresponding to the state of the variable valve characteristics mechanism 25. When acquiring the current intake manifold pressure pmsm, information corresponding to the current state of the variable valve characteristics mechanism 25 set by the valve characteristics setting unit 44 is used. Here, the information corresponding to the state of the variable valve characteristics mechanism 25 is information related to the valve timing, which is the opening and closing timing of the intake valve 23, and information related to the valve timing, which is the opening and closing timing of the exhaust valve 24. Note that methods for acquiring the intake manifold pressure using an air model are conventionally known, and since a conventionally used air model is also used in this embodiment, detailed description thereof will be omitted here.

[0026] The base boost pressure acquisition unit 47 acquires the base boost pressure pcmbs. The base boost pressure pcmbs is the boost pressure in the internal combustion engine 100 when the valve characteristics variable mechanism 25 is in a base state. Here, the valve characteristics variable mechanism 25 being in a base state means that the valve characteristics variable mechanism 25 is in a preset state that serves as a reference state when changing opening and closing characteristics, such as the opening and closing timings of the intake valve 23 and the exhaust valve 24, in the internal combustion engine 100. The base boost pressure pcmbs is acquired based on a map that uses the engine speed NE and the engine load KL as parameters. This map will be described later.

[0027] The base intake manifold pressure acquisition unit 48 acquires the base intake manifold pressure pmbs using an air model that uses the base boost pressure pcmbs acquired by the base boost pressure acquisition unit 47. That is, the base intake manifold pressure acquisition unit 48 uses the base boost pressure pcmbs as an argument for acquiring the base intake manifold pressure pmbs. The air model also uses information corresponding to the state of the valve characteristics variable mechanism 25. When acquiring the base intake manifold pressure pmbs, information corresponding to the state of the valve characteristics variable mechanism 25 in a base state is used. Here, the information corresponding to the state of the valve characteristics variable mechanism 25 is information related to the valve timing, which is the opening and closing timing of the intake valve 23, and information related to the valve timing, which is the opening and closing timing of the exhaust valve 24. This is the same as when the current intake manifold pressure pmsm is acquired. However, the opening and closing timings of the intake valve 23 and the exhaust valve 24 when acquiring the base intake manifold pressure pmbs are times that are preset for the base state. Note that when acquiring the base intake manifold pressure pmbs, the same air model as when acquiring the current intake manifold pressure pmsm is used.

[0028] A difference value acquisition unit 49 calculates a difference value dpm between the current intake pipe pressure pmsm acquired by the current intake pipe pressure acquisition unit 46 and the base intake pipe pressure pmbs acquired by the base intake pipe pressure acquisition unit 48. The difference value dpm is acquired based on a map having the current intake pipe pressure pmsm, the base intake pipe pressure pmbs, the engine speed NE, and the engine load KL as parameters. This map will be described later.

[0029] The correction coefficient acquisition unit 50 acquires a correction coefficient kdpm for correcting the difference value dpm acquired by the difference value acquisition unit 49. The correction coefficient kdpm is acquired based on a map that uses the engine speed NE and the engine load KL as parameters. This map will be described later.

[0030] The ignition timing correction amount calculation unit 51 calculates the ignition timing correction amount afin using the difference value dpm acquired by the difference value acquisition unit 49 and the correction coefficient kdpm acquired by the correction coefficient acquisition unit 50.

[0031] The ECU 40 functions as an ignition timing control device through cooperation of these components. The WGV control unit 43 does not directly function as part of the ignition timing control device, but controls the opening and closing state of the WGV 61 as part of engine control. When the opening and closing state of the WGV 61 changes, the boost pressure and back pressure change, and ultimately the internal EGR amount changes. The ignition control device of this embodiment uses the base boost pressure pcmbs and the current boost pressure pcmsm to reflect the effect of the opening and closing state of the WGV 61 on the internal EGR amount in the ignition timing correction amount afin.

[0032] [Determining the ignition timing correction amount afin] Next, the process of determining the ignition timing correction amount afin by the ignition timing control device of this embodiment will be described. The ECU 40 corrects the ignition timing of the spark plug 7 using the ignition timing correction amount afin calculated by the ignition timing correction amount calculation unit 51. The ECU 40 performs the process of determining the ignition timing correction amount afin at a predetermined cycle so that the operating state of the internal combustion engine 100 is reflected in the ignition timing correction. The ignition timing correction amount afin is expressed by the following equation 1. (Equation 1) Ignition timing correction amount afin = correction coefficient kdpm × difference value dpm

[0033] The ECU 40 corrects the basic ignition timing abse by the ignition timing correction amount afin. Here, the basic ignition timing abse indicates the ignition timing on the retard side between the ignition timing that provides the maximum combustion torque at the current operating point of the internal combustion engine 100 and the ignition timing at the advance limit of the ignition timing that can suppress knocking, and is the ignition timing that is set in advance depending on the model of the internal combustion engine 100.

[0034] <Getting current intake manifold pressure pmsm> As described above, the current intake manifold pressure pmsm is acquired by the current intake manifold pressure acquisition unit 46. The current supercharging pressure pcmsm used when the current intake manifold pressure pmsm is acquired is acquired by the current supercharging pressure acquisition unit 45.

[0035] <Obtaining base intake manifold pressure (pmbs)> As described above, the base intake pipe pressure pmbs is acquired by the base intake pipe pressure acquisition unit 48. The base supercharging pressure pcmbs used when acquiring the base intake pipe pressure pmbs is acquired by the base supercharging pressure acquisition unit 47 using the map shown in FIG. 3 in the following manner.

[0036] <Obtaining base boost pressure PCMBS> FIG. 3 is an example of a map for calculating the base boost pressure pcmbs. However, what is shown in FIG. 3 is only a portion of the map. In other words, the map shown in FIG. 3 is used to calculate the base boost pressure pcmbs at a certain engine speed NE. Therefore, if the engine speed NE is different, another portion of the map is referenced.

[0037] The base boost pressure pcmbs at a certain engine speed NE is acquired in accordance with the engine load KL acquired by the engine load acquisition unit 41, for example, based on the map shown in Fig. 3. When the engine load KL of the internal combustion engine 100 is low, the internal combustion engine 100 is not supercharged, and therefore the base boost pressure pcmbs is a value equivalent to atmospheric pressure.

[0038] Here, the reason why the base boost pressure pcmbs is used when obtaining the base intake manifold pressure pmbs is to reflect changes in the back pressure in the internal combustion engine 100 in the value of the intake manifold pressure used to calculate the ignition timing correction amount afin. In the internal combustion engine 100, opening and closing control of the WGV 61 is performed as part of engine control. When the WGV 61 operates in the valve closing direction, the back pressure increases. The increase in back pressure affects the internal EGR amount. In other words, an increase in back pressure increases the internal EGR amount. An increase in the internal EGR amount increases the compression end temperature, making knocking more likely to occur. Therefore, in this embodiment, the base boost pressure pcmbs is used when obtaining the base intake manifold pressure pmbs in order to perform control that reflects the difference between the base boost pressure and the current boost pressure.

[0039] <Calculation of the difference value dpm> As described above, the difference value dpm is acquired by the difference value acquisition unit 49. The difference value acquisition unit 49 acquires the difference value dpm using the map shown in FIG. 4. FIG. 4 is an example of a map for calculating the difference value dpm. However, FIG. 4 shows only a portion of the map. In other words, the map shown in FIG. 4 calculates the difference value dpm for a certain engine speed NE and a certain valve characteristic. Therefore, if the engine speed NE or the valve characteristics of the intake valve 23 and the exhaust valve 24 are different, another portion of the map is referenced.

[0040] Referring to FIG. 4, at a certain engine load KL, a difference occurs between the current intake manifold pressure pmsm and the base intake manifold pressure pmbs, and this difference is the difference value dpm. The reason for this difference value dpm is that the current intake manifold pressure pmsm and the base intake manifold pressure pmbs are calculated using different boost pressures. That is, the base intake manifold pressure pmbs, which is the target for calculating the difference value dpm, uses the base boost pressure pcmbs as an argument when calculated by the air model. Similarly, the current intake manifold pressure pmsm is also calculated by the air model using the current boost pressure pcmsm as an argument when calculated by the air model. As a result, the difference between the base boost pressure pcmbs and the current boost pressure pcmsm is reflected in the difference value dpm. In this way, by reflecting the difference between the base boost pressure pcmbs and the current boost pressure pcmsm in the difference value dpm, the ignition timing control device can calculate an ignition timing correction amount that appropriately reflects the intake manifold pressure in the internal combustion engine 100.

[0041] <Calculation of correction coefficient kdpm> As described above, the correction coefficient kdpm is acquired by the correction coefficient acquisition unit 50. The correction coefficient acquisition unit 50 acquires the correction coefficient kdpm using the map shown in FIG. 5. FIG. 5 is an example of a map for acquiring the correction coefficient kdpm. However, FIG. 5 shows only a portion of the map. In other words, the map shown in FIG. 5 acquires the correction coefficient kdpm according to the engine load KL at a certain engine speed NE. Therefore, if the engine speed NE is different, another portion of the map is referenced. By using the correction coefficient kdpm using the engine speed NE and the engine load KL as parameters, it is possible to calculate the ignition timing correction amount afin that more accurately reflects the operating state of the internal combustion engine 100.

[0042] <Calculation of ignition timing correction amount afin> As described above, the ignition timing correction amount afin is calculated by the ignition timing correction amount calculation unit 51. The ignition timing correction amount calculation unit 51 calculates the ignition timing correction amount afin using the above-described formula 1. FIG. 6 is a graph showing the ignition timing correction amount afin calculated for each engine load KL. Note that FIG. 6 shows the ignition timing correction amount afin for a certain engine speed NE and a certain valve characteristic. Therefore, if the engine speed NE or the valve characteristics of the intake valve 23 and the exhaust valve 24 are different, a different ignition timing correction amount afin will be displayed.

[0043] The ECU 40 corrects the ignition timing of the spark plug 7 using the ignition timing correction amount afin calculated by the ignition timing correction amount calculation unit 51.

[0044] In addition, in the internal combustion engine 100, KCS (Knock Control System) learning is performed, but if ignition timing correction using the base boost pressure pcmbs is not performed, it is expected that the KCS learning value will not be stable.

[0045] In contrast to this, the ignition timing correction amount afin in this embodiment reflects the boost pressure that changes depending on the state of the WGV 61 and the state of the variable valve characteristics mechanism 25. This suppresses the occurrence of knocking itself and stabilizes the KCS learning value.

[0046] According to the ignition timing control device of this embodiment, the correction amount of the ignition timing can be appropriately set in the internal combustion engine 100 equipped with the turbocharger 14 and the WGV 61.

[0047] The above-described embodiments are merely examples for implementing the present invention, and the present invention is not limited to these. Various modifications of these embodiments are within the scope of the present invention. Furthermore, it is obvious from the above description that various other embodiments are possible within the scope of the present invention. [Explanation of symbols]

[0048] 10 intake pipe 11 exhaust pipe 14 Turbocharger 16 Boost pressure sensor 23 Intake valve 24 Exhaust valve 25 Variable valve characteristics mechanism 25a Intake VVT mechanism 25b Exhaust VVT mechanism 40 ECU 45 Current boost pressure acquisition unit 46 Current intake pipe pressure acquisition unit 47 Base supercharging pressure acquisition unit 48 Base intake pipe pressure acquisition unit 49 Differential value calculation unit 50 Correction coefficient acquisition unit 51 ignition timing correction amount calculation unit 60 exhaust bypass passage 61 Wastegate valve (WGV) 62 Actuator 63 Vacuum pump 70 Crank angle sensor 71 accelerator pedal opening sensor 100 internal combustion engine

Claims

1. An ignition timing control device applied to an internal combustion engine including a valve characteristic variable mechanism that changes the opening / closing characteristic of at least one of an intake valve and an exhaust valve, a supercharger, and a wastegate valve, an ignition timing correction amount calculation unit that calculates a correction amount of ignition timing relative to a basic ignition timing that is preset as a basic ignition timing in the internal combustion engine, using a base boost pressure in the internal combustion engine when the valve characteristics variable mechanism is in a base state that is preset in the internal combustion engine as a reference state when the opening / closing characteristics of the intake valve and the exhaust valve are changed, and a current boost pressure that is determined depending on a current state of the valve characteristics variable mechanism and a current state of the wastegate valve, Ignition timing control device for internal combustion engines.

2. the ignition timing correction amount calculation unit calculates the correction amount of the ignition timing using a difference value between a base intake pipe pressure that reflects the base supercharging pressure and a current intake pipe pressure that reflects the current supercharging pressure.

2. The ignition timing control device for an internal combustion engine according to claim 1.

3. the ignition timing correction amount calculation unit calculates the correction amount of the ignition timing using the difference value, a correction coefficient calculated based on an engine load and a rotation speed of the internal combustion engine.

3. The ignition timing control device for an internal combustion engine according to claim 2.

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