Patent Grant
10626807
The disclosure of Japanese Patent Application No. 2017-082540 filed on Apr. 19, 2017 including its specification, claims and drawings, is incorporated herein by reference is its entirety.
The present invention relates to a controller and a control method for an internal combustion engine for determining a combustion state based on ion current.
To date, there has been known a controller for an internal combustion engine which determines a combustion state, such as preignition and knock, based on the ion current which flows into the discharge electrode of the spark plug. For example, in the technology disclosed in Japanese Patent Unexamined Application Publication No. 63-68774 (JP 63-68774 A), it is configured to determine that preignition with large intensity occurred in the case where generation of the ion current is detected before the ignition timing by the spark discharge of the spark plug.
In the technology disclosed in Japanese Patent Unexamined Application Publication No. 2009-57940 (JP 2009-57940 A), it is configured to determine the generation end timing of the ion current after the ignition timing, and determine the intensity of preignition based on the generation end timing.
However, a noise component according to a noise component superimposed on the power source voltage supplied to the ignition coil may be superimposed on the detection value of the ion current, and the amplitude of the noise component of the ion current may become large. In this case, if combustion state, such as intensity of preignition, is determined based on the ion current like the technologies of JP 63-68774 A and JP 2009-57940 A, it may cause erroneous determination.
Thus, it is desirable to provide a controller and a control method for an internal combustion engine capable of suppressing causing erroneous determination of combustion state even if noise component is superimposed on the ion current.
A controller for an internal combustion engine according to the present invention is a controller for an internal combustion engine that is provided with an spark plug which ignites a fuel-air mixture in a combustion chamber, an ignition coil which supplies an ignition energy to the spark plug, and an ion current detection circuit which outputs an output signal according to an ion current which flows into a discharge electrode of the spark plug, the controller for the internal combustion engine including:
A control method for an internal combustion engine according to the present invention is a control method for an internal combustion engine that is provided with a spark plug which ignites a fuel-air mixture in a combustion chamber, an ignition coil which supplies an ignition energy to the spark plug, and an ion current detection circuit which outputs an output signal according to an ion current which flows into a discharge electrode of the spark plug, the control method for the internal combustion engine including:
In the case where the amplitude of the noise component superimposed on the ion current is large, when the true value of the ion current drops, the lower part of the vibration component of the ion current reaches 0, and erroneous determination of combustion state may cause. According to the controller and the control method for the internal combustion engine concerning the present invention, at a time point when the minimum value of the ion current is below the determination prohibition threshold value, since it includes the case where the true value of the ion current is dropping in the state where the amplitude of the noise component of the ion current is large, determination of the combustion state at this time point is prohibited, and erroneous determination of the combustion state can be suppressed. Therefore, even if noise component is superimposed on the ion current, erroneous determination of the combustion state can be suppressed.
A controller 50 for an internal combustion engine 1 (hereinafter, referred to simply as the controller 50) according to Embodiment 1 will be explained with reference to the drawings.
1. The Configuration of the Internal Combustion Engine 1
The configuration of the internal combustion engine 1 will be explained. The internal combustion engine 1 has a plurality of combustion chambers 25 (for example, four combustion chambers 25) in which a fuel-air mixture is combusted. The combustion chamber 25 is configured by a cylinder and a piston 5. Hereinafter, the combustion chamber 25 is also referred to the cylinder. The internal combustion engine 1 is provided with an intake path 23 for supplying air to the each combustion chamber 25 and an exhaust path 17 for discharging exhaust gas from the each combustion chamber 25. The internal combustion engine 1 has a throttle valve 6 for opening and closing the intake path 23. The throttle valve 6 is an electronically controlled throttle valve that is opening/closing-driven by an electric motor controlled by the controller 50. The throttle valve 6 is provided with a throttle opening degree sensor 7 that generates an electric signal according to a throttle opening degree of the throttle valve 6.
An air cleaner 24 for purifying air taken into the intake path 23 is provided at the most upstream part of the intake path 23. An air flow sensor 3 which outputs an electric signal according to an intake air amount taken into the intake path 23 is provided in a part of the intake path 23 at the upstream side of throttle valve 6. The part of the intake path 23 at the downstream side of the throttle valve 6 is an intake manifold 11, and is connected to a plurality of combustion chambers 25. The upstream side part of the intake manifold 11 is a surge tank for suppressing an intake pulsation.
A manifold pressure sensor 8 which outputs an electric signal according to a manifold pressure which is a gas pressure in the intake manifold 11 is provided in the intake manifold 11. Either one of the air flow sensor 3 or the manifold pressure sensor 8 may be provided. An injector 13 for injecting a fuel is provided in an intake port which is the downstream side part of the intake manifold 11. The injector 13 may be provided in such a way as to inject a fuel directly into the combustion chamber 25.
A spark plug 18 for igniting the fuel-air mixture in the combustion chamber 25 and an ignition coil 16 for supplying ignition energy to the spark plug 18 are provided on the top of the each combustion chamber 25. On the top of the each combustion chamber 25, there are provided an intake valve 14 for adjusting the amount of intake air to be taken from the intake path 23 into the combustion chamber 25 and an exhaust valve 15 for adjusting the amount of exhaust gas to be exhausted from the combustion chamber 25 to the exhaust path 17. The intake valve 14 is provided with an intake variable valve timing mechanism that makes the opening and closing timing thereof variable. The exhaust valve 15 is provided with an exhaust variable valve timing mechanism that makes the opening and closing timing thereof variable. Each of the intake and the exhaust variable valve timing mechanisms 14, 15 has an electric actuator which changes a phase angle of the opening and closing timing of the valve. The electric actuator is an electric motor which changes the phase angle.
A crankshaft of the internal combustion engine 1 is provided with a signal plate in which a plurality of teeth were provided in the outer circumference with the preliminarily set angle interval. A crank angle sensor 9 is fixed to a cylinder block so as to oppose the tooth of the signal plate of the crankshaft and outputs a pulse signal synchronizing with passage of the tooth. Although not shown in the figure, a cam shaft of the internal combustion engine 1 is provided with a signal plate in which a plurality of teeth were provided in the outer circumference with the preliminarily set angle interval. A cam angle sensor 10 is fixed so as to oppose the tooth of the signal plate of the cam shaft and outputs a pulse signal synchronizing with passage of the tooth. Based on two kinds of output signals of the crank angle sensor 9 and the cam angle sensor 10, the controller 50 detects a crank angle on the basis of the top dead center of each piston 5 and determines a stroke of each combustion chamber 25.
<Ion Current Detection Circuit 19, Ignition Coil 16, Spark Plug 18>
An ion current detection circuit 19 which outputs an output signal according to a current which flows into a discharge electrode 181 of each spark plug 18 is provided. One ion current detection circuit 19, one ignition coil 16, and one spark plug 18 are provided for each of a plurality of the combustion chambers 25. In the present embodiment, the ignition coil 16 and the ion current detection circuit 19 are integrally configured.
One end of the primary coil 161 is connected to the positive electrode of the direct current power source 28, and the other end of the primary coil 161 is connected to the ground (the negative electrode of the direct current power source 28) via the igniter 163. By controlling on/off of the igniter 163 by the controller 50, the electrical connection from the direct current power source 28 to the primary coil 161 is turned on or turned off. A power source voltage sensor 27 which detects a power source voltage supplied to the primary coil 161 from the direct current power source 28 is provided. One end of the secondary coil 162 is connected to the ground via the discharge electrode 181 of the spark plug 18, and the other end of the secondary coil 162 is connected to the ground via two diodes 191, 192 of the ion current detection circuit 19.
The ion current detection circuit 19 is provided with a Zener diode 191 and a diode 192 which are reversely connected in series with each other between the other end of the secondary coil 162 and the ground, a capacitor 193 which is connected in parallel with the Zener diode 191, and an amplifier 194 which amplifies a voltage according to the ion current to output as the output signal of the ion current detection circuit 19.
The capacitor 193 is charged by the discharge current which flows through the discharge electrode 181 during a spark discharge period until the inter-electrode voltage reaches a breakdown voltage (a bias voltage) of the Zener diode 191. The bias voltage of the capacitor 193 is applied to the discharge electrode 181 of the spark plug 18 in a period other than the spark discharge period, and the ion generated when fuel-air mixture burned flows through the discharge electrode 181 as the ion current. As a result, a current according to the ion current flows into the capacitor 193 via a resistance in the amplifier 194, and the both-ends voltage of the resistance in the amplifier 194 becomes a voltage according to the ion current. Then, the both-ends voltage of the resistance in the amplifier 194 is amplified by an operational amplifier in the amplifier 194, and is outputted to the controller 50 as the output signal.
The ion current detection circuit 19 is configured to detect the ion current of the positive side, and cannot detect the ion current of the negative side. For example, the ion current detection circuit 91 is provided with a diode which blocks current in a flowing direction from the capacitor 193 to the resistance in the ion current detection circuit 19. An A/D converter of the controller 50 does not convert the output signal of the ion current detection circuit 19 corresponding to the ion current of the negative side.
2. The Configuration of the Controller 50
Next, the controller 50 will be explained. The controller 50 is the one whose control subject is the internal combustion engine 1. As shown in the block diagram of
As the computing processing unit 90, ASIC (Application Specific Integrated Circuit), IC (Integrated Circuit), DSP (Digital Signal Processor), FPGA (Field Programmable Gate Array), various kinds of logical circuits, various kinds of signal processing circuits, and the like may be provided. As the computing processing unit 90, a plurality of the same type ones or the different type ones may be provided, and each processing may be shared and executed. As the storage apparatuses 91, there are provided a RAM (Random Access Memory) which can read data and write data from the computing processing unit 90, a ROM (Read Only Memory) which can read data from the computing processing unit 90, and the like. The input circuit 92 is connected with various kinds of sensors and switches and is provided with an A/D converter and the like for inputting output signals from the sensors and the switches to the computing processing unit 90. The output circuit 93 is connected with electric loads and is provided with a driving circuit and the like for outputting a control signal from the computing processing unit 90.
In addition, the computing processing unit 90 runs software items (programs) stored in the storage apparatus 91 such as a ROM and collaborates with other hardware devices in the controller 50, such as the storage apparatus 91, the input circuit 92, and the output circuit 93, so that the respective functions of the control units 51 through 54 included in the controller 50 are realized. Setting data items such as maps and determination value to be utilized in the control units 51 through 54 are stored, as part of software items (programs), in the storage apparatus 91 such as a ROM.
In Embodiment 1, the input circuit 92 is connected with various kinds of sensors such as the air flow sensor 3, the throttle position sensor 7, the manifold pressure sensor 8, the crank angle sensor 9, the cam angle sensor 10, a plurality of the ion current detection circuits 19 (in this example, four) for the each combustion chamber 25, the accelerator position sensor 26, and the power source voltage sensor 27. The output circuit 93 is connected with various kinds of actuators such as the throttle valve 6 (the electric motor), the injector 13, the intake variable valve timing mechanism 14, the exhaust variable valve timing mechanism 15, and a plurality of the ignition coils 16 (in this example, four) for the each combustion chamber 25. The controller 50 is connected with various kinds of unillustrated sensors, switches, actuators, and the like.
The controller 50 detects an intake air amount based on the output signal of the air flow sensor 3 or the manifold pressure sensor 8 and the like, detects a throttle opening angle based on the output signal of the throttle position sensor 7, and detects an accelerator opening degree based on the output signal of the accelerator position sensor 26. The controller 50 detects an angle and a rotational speed of the crankshaft, and the opening and closing timings of the intake valve 14 and the exhaust valve 15, based on the output signal of the crank angle sensor 9 and the cam angle sensor 10.
As basic control, the controller 50 calculates a fuel injection amount, an ignition timing, and the like, based on inputted output signals and the like from the various kinds of sensors, and then performs driving control of the injector 13, the ignition coil 16, and the like. Based on the accelerator opening degree and the like, the controller 50 calculates the output torque of the internal combustion engine 1 demanded by the driver, and then controls the throttle valve 6 and the like so that an intake air amount for realizing the demanded output torque is obtained. Specifically, the controller 50 calculates a target throttle opening degree and performs driving control of the electric motor for the throttle valve 6 so that the throttle opening degree approaches the target throttle opening degree. The controller 50 calculates target opening and closing timings of the intake valve 14 and the exhaust valve 15 based on the rotational speed of the crankshaft (the internal combustion engine 1), the intake air amount, and the like, respectively, and then performs driving control of the electric actuators for the intake and the exhaust variable valve timing mechanisms 14, 15 so that the opening and closing timings of the intake valve 14 and the exhaust valve 15 approaches the target opening and closing timings, respectively.
2-1. The Ignition Control Unit 54
The ignition control unit 54 implements an ignition control processing that shuts down after connecting electrically the primary coil 161 and the direct current power source 28 for generating high voltage in the secondary coil 162 and generating spark discharge in the discharge electrode 181. The ignition control unit 54 calculates an energizing time and an ignition timing (an ignition crank angle) to the primary coil 161. After the ignition control unit 54 turns on the igniter 163 and energizes the primary coil 161 during the energizing time, the ignition control unit 54 turns off the igniter 163 at the ignition timing and shuts down the energization of the primary coil 161 to generate spark discharge. Spark discharge is continued until the magnetic energy accumulated in the core 166 decreases.
2-2. The Ion Current Detection Unit 51
The ion current detection unit 51 implements an ion current detection processing that detects the ion current generated by combustion of the fuel-air mixture based on the output signal of the ion current detection circuit 19. The Ion current detection unit 51 performs the A/D conversion of the output signal of the ion current detection circuit 19 in a sampling period shorter than one half of the cycle of the noise component superimposed on the detected ion current (for example, less than or equal to 1/10 of the cycle of the noise component). The ion current detection unit 51 performs the A/D conversion continuously for every sampling period during the determination period Tj set corresponding to the combustion period of each combustion, and stores the detection value of each ion current to the storage apparatus 91, such as RAM, by correlating with the crank angle at the detecting time point and the like. The determination period Tj of each cylinder is set to a predetermined crank angle interval on the basis of the top dead center of the piston of each cylinder (for example, a crank angle interval from 60° before the top dead center to 90° after the top dead center).
2-3. The Combustion State Determination Unit 52
The combustion state determination unit 52 implements a combustion state determination processing that determines a combustion state of each cylinder based on the ion current during the determination period Tj set corresponding to the combustion period of each combustion (for example, the crank angle interval from 60° before the top dead center to 90° after the top dead center). The combustion state determination unit 52 determines the combustion state at a predetermined crank angle after the determination period Tj, based on the detection value of the ion current during the determination period Tj stored in the storage apparatus 91.
<Noise Component Superimposed on Ion Current>
As shown in
The periodic noise component of the power source voltage is transmitted to the secondary coil 162 side via the primary coil 161 and the core 166, and be superimposed on the output signal of the ion current detection circuit 19 as the periodic noise component of the ion current. When the amplitude of the periodic noise component of the power source voltage increases or decreases, the amplitude of the periodic noise component superimposed on the output signal of the ion current detection circuit 19 also increases or decreases according to the increase or decrease of the amplitude. Thus, if the ion current on which the periodic noise component is superimposed is used as it is, the combustion state cannot be determined with good accuracy.
<Reduction of Noise Component by Statistical Processing>
Accordingly, in order to reduce the noise component, the combustion state determination unit 52 calculates a statistical processing value Ist of the ion current during a processing period ΔTc at each time point of the determination period Tj. According to this configuration, the noise component of the ion current can be reduced by the statistical processing.
The processing period ΔTc is set to a period greater than or equal to one cycle of the periodic noise component superimposed on the ion current (for example, natural number times of one cycle). As mentioned above, the noise component of the ion current is according to the noise component superimposed on the power source voltage. Accordingly, in the present embodiment, the combustion state determination unit 52 sets the processing period ΔTc to a period greater than or equal to one cycle of the periodic noise component superimposed on the power source voltage supplied to the ignition coil 16. The combustion state determination unit 52 determines the cycle of the noise component superimposed on the power source voltage based on the output signal of the power source voltage sensor 27, and sets the processing period ΔTc to a period obtained by multiplying a preliminarily set coefficient greater than or equal to one (for example, a natural number greater than or equal to one) to the determined cycle of the noise component of the power source voltage.
In the present embodiment, the combustion state determination unit 52 calculates, as the statistical processing value Ist, an average value (a moving average value) of the ion current during the processing period ΔTc, or a median value of a maximum value and a minimum value of the ion current during the processing period ΔTc.
For example, the combustion state determination unit 52 changes a processing time point tp from the start point of the determination period Tj to the end point, and repeatedly performs moving average processing that calculates the average value of the ion current sampled during the processing period ΔTc centered at the processing time point tp (from tp−ΔTc/2 to tp+ΔTc/2), to calculate the average value at each time point of the determination period Tj.
Alternatively, the combustion state determination unit 52 changes the processing time point tp from the start point of the determination period Tj to the end point, and repeatedly performs median value calculation processing that calculates the maximum value and the minimum value of the ion current sampled during the processing period ΔTc centered at the processing time point tp (from tp−ΔTc/2 to tp+ΔTc/2), and calculates the median value (average value) of the maximum value and the minimum value, to calculate the median value at each time point of the determination period Tj.
By performing such statistical processing, the statistical processing value Ist of the ion current whose noise component was reduced can be calculated, and it becomes easy to perform determination of the combustion state.
<Detection of Preignition>
In the present embodiment, the combustion state determination unit 52 determines an occurrence and a sign of preignition as the combustion state. The preignition is a phenomenon in which the overheated spark plug 18 or the carbon sludge accumulated into the combustion chamber 25 becomes a heat source, and the compressed fuel-air mixture causes self-ignition before spark ignition.
The waveform of the ion current will be explained.
On the other hand, it is considered that an ion generated by the burning reaction itself as described above and an ion generated when NOx which exists in existing gas is thermally ionized with a temperature rise in the combustion chamber 25 becomes a medium of the ion current which appears in the crest of the latter half. The peak appears at the crank angle at which the temperature in the combustion chamber 25 becomes the highest. The peak becomes higher as combustion is more active as a whole, and the peak becomes lower as combustion is slower.
In contrast to the waveform of the ion current at this normal combustion, when there is the sign and the occurrence of preignition, the rise of the ion current advances as compared with the normal combustion, and the end timing of the ion current also advances as compared with the normal combustion. As the generation start timing and the generation end timing of the ion current become the advance angle side more, the intensity of preignition becomes larger. As the peak timing of the crest of the latter half becomes the advance angle side more, the intensity representing the sign and the occurrence of preignition becomes larger. If the ion current begins to be generated before the ignition timing, preignition occurs and its intensity becomes very large.
The combustion state determination unit 52 determines a time point (crank angle) when the statistical processing value Ist of the ion current during the determination period Tj becomes lower than a preliminarily set end determination threshold value Thjf after the ignition timing, as the generation end timing of the ion current. Then, the combustion state determination unit 52 determines that the intensity of preignition becomes larger as the determined generation end timing of the ion current becomes the advance angle side more than a preliminarily set generation end timing of the ion current at the normal combustion.
The combustion state determination unit 52 determines a time point (crank angle) when the statistical processing value Ist of the ion current during the determination period Tj becomes higher than a preliminarily set start determination threshold value Thjs before the ignition timing, as the generation start timing of the ion current. The combustion state determination unit 52 determines that the intensity of preignition is very large in the case where the generation start timing of the ion current is before the ignition timing.
<Erroneous Determination by Float from 0 of Statistical Processing Value Ist by Noise Component>
Since it is not configured to detect the ion current of the negative side as mentioned above, as shown in
In the case where the amplitude of the noise component of the power source voltage increases and the amplitude of the noise component of the ion current increases, the float width from 0 of the statistical processing value Ist of the ion current also increases according to the increase in the amplitude. Since the amplitude of the noise component is not constant and fluctuates wildly irregularly, the float width from 0 of the statistical processing value Ist also fluctuates according to fluctuation of the amplitude of the noise component.
For example, as shown in
On the other hand, as shown in
As described above, when the generation end timing of the ion current cannot be determined even though the true value of the ion current dropped to around zero, since there is a possibility that the fluctuation timing of the amplitude of the noise component is determined erroneously as the generation end timing of the ion current if determination is continued, it is considered to stop determination of the combustion state of this combustion time. On the other hand, when the generation end timing of ion current can be determined before the true value of the ion current drops to around zero, it is considered that the amplitude of the noise component at the determination timing is small and normal determination is performed.
As shown in
<Determination Prohibition Processing by Minimum Value Imin of Ion Current>
Accordingly, the combustion state determination unit 52 implements a determination prohibition processing that calculates a minimum value Imin of the ion current during the processing period ΔTc at each time point of the determination period Tj, and prohibits determination of the combustion state at a time point when the minimum value Imin of the ion current is below a preliminarily set determination prohibition threshold value Thjp.
For example, the combustion state determination unit 52 changes a processing time point tp from the start point of the determination period Tj to the end point, and repeatedly performs minimum value calculation processing that calculates the minimum value Imin of the ion current sampled during the processing period ΔTc centered at the processing time point tp (from tp−ΔTc/2 to tp+ΔTc/2), to calculate the minimum value Imin at each time point of the determination period Tj.
The combustion state determination unit 52 determines the combustion state of each combustion based on the statistical processing value Ist at each time point when the minimum value Imin of ion current becomes larger than the determination prohibition threshold value Thjp. In the present embodiment, the combustion state determination unit 52 determines the generation end timing and the generation start timing of the ion current as mentioned above, based on the statistical processing value Ist at each time point when the minimum value Imin of the ion current becomes larger than the determination prohibition threshold value Thjp. The determination prohibition threshold, value Thjp is set to a value smaller than the end determination threshold value Thjf and the start determination threshold value Thjs.
According to this configuration, when the minimum value Imin of the ion current becomes below the determination prohibition threshold value Thjp, it can be determined that the true value of the ion current drops to around zero, and the determination of the combustion state in this case can be prohibited. As shown in
As shown in
2-4. The Combustion State Control Unit 53
The combustion state control unit 53 implements a combustion state control processing that controls the combustion state based on the determination result of the combustion state by the combustion state determination unit 52. In the present embodiment, the combustion state control unit 53 implements a preignition suppression control that suppresses occurrence of preignition according to the intensity of preignition determined by the combustion state determination unit 52. Specifically, the combustion state control unit 53 performs one or both of a decrease of charging efficiency and a change of fuel injection, in the case where the intensity of preignition becomes large. There is fuel cut or enrichment as the change of fuel injection. The combustion state control unit 53 performs fuel cut in the case where the intensity of preignition becomes larger than a threshold value, and performs enrichment according to the intensity of preignition in the case where the intensity of preignition is smaller than the threshold value. In the case where the injector 13 which injects fuel directly in the combustion chamber 25 is provided, compression stroke injection may be performed as enrichment.
According to the intensity of preignition, the combustion state control unit 53 changes the phase angle of one or both of the intake variable valve timing mechanism 14 and the exhaust variable valve timing mechanism 15 so that charging efficiency (intake air amount in the combustion chamber 25) decreases.
2-5. Flowchart
The procedure (the control method of internal combustion engine 1) of schematic processing of the controller 50 concerning the present embodiment is explained based on the flow chart shown in
In the step S01, as mentioned above, the ion current detection unit 51 implements the ion current detection processing (an ion current detection step) that detects the ion current generated by combustion of the fuel-air mixture based on the output signal of the ion current detection circuit 19.
In the step S02, as mentioned above, the combustion state determination unit 52 implements the combustion state determination processing (a combustion state determination step) that determines the combustion state of each combustion chamber 25 based on the ion current during the determination period Tj set corresponding to the combustion period of each combustion chamber 25. At this time, as mentioned above, the combustion state determination unit 52 implements the determination prohibition processing that calculates the minimum value Imin of the ion current during the processing period ΔTc at each time point of the determination period Tj, and prohibits determination of the combustion state at a time point when the minimum value Imin of the ion current is below a preliminarily set determination prohibition threshold value Thjp.
In the step S03, as mentioned above, the combustion state control unit 53 implements the combustion state control processing (a combustion state control step) that controls the combustion state based on the determination result of the combustion state by the combustion state determination unit 52.
Lastly, other embodiments of the present invention will be explained. Each of the configurations of embodiments to be explained below is not limited to be separately utilized but can be utilized in combination with the configurations of other embodiments as long as no discrepancy occurs.
(1) In the above-mentioned Embodiment 1, there has been explained the case where the combustion state determination unit 52 determines occurrence of preignition as the combustion state. However, embodiments of the present invention are not limited to the foregoing case. For example, the combustion state determination unit 52 may determine occurrence of knock as the combustion state. For example, the combustion state determination unit 52 may extract a component of a knock occurrence frequency band included in the ion current with a band pass filter and the like, and may determine the intensity of knock based on the extracted value. Even in this case, like Embodiment 1, the combustion state determination unit 52 calculates the minimum value Imin of the ion current during the processing period ΔTc, and prohibits determination of the knock occurrence at a time point when the minimum value Imin of the ion current is below a preliminarily set determination prohibition threshold value Thjp. The combustion state control unit 53 may change the ignition timing to the retard angle side according to the intensity of knock, as control of the combustion state.
(2) In the above-mentioned Embodiment 1, there has been explained the case where the combustion state determination unit 52 determines a time point (crank angle) when the statistical processing value Ist of the ion current during the determination period Tj becomes lower than a preliminarily set end determination threshold value Thjf after the ignition timing, as the generation end timing of the ion current, and then determines that the intensity of preignition becomes larger as the determined generation end timing of the ion current becomes the advance angle side more. However, embodiments of the present invention are not limited to the foregoing case. The combustion state determination unit 52 may determine a peak time point (crank angle) of the crest of the latter half after the ignition timing based on the statistical processing value Ist of the ion current during the determination period Tj. Then, the combustion state determination unit 52 determines that the intensity of preignition becomes larger as the determined peak time point of the crest of the latter half becomes the advance angle side more than a preliminarily set peak time point of the crest of the latter half at the normal combustion.
Various modifications and alterations of this invention will be apparent to those skilled in the art without departing from the scope and spirit of this invention, and it should be understood that this is not limited to the illustrative embodiments set forth herein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017-082540 | Apr 2017 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 5925819 | Yoshinaga | Jul 1999 | A |
| 6145491 | Wilstermann | Nov 2000 | A |
| 20030183195 | Uchida | Oct 2003 | A1 |
| 20040084018 | Zhu | May 2004 | A1 |
| 20050114012 | Zhu | May 2005 | A1 |
| 20070079817 | VanDyne | Apr 2007 | A1 |
| 20070186903 | Zhu | Aug 2007 | A1 |
| 20090084353 | Inada | Apr 2009 | A1 |
| 20090173315 | Inada | Jul 2009 | A1 |
| 20110210744 | Barrett | Sep 2011 | A1 |
| Number | Date | Country |
|---|---|---|
| 63-068774 | Mar 1988 | JP |
| 2009-057940 | Mar 2009 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20180306129 A1 | Oct 2018 | US |
