Patent Application
20130092136
1. Field of the Invention
The present invention relates to an ignition control apparatus that controls ignition of an internal combustion engine mainly utilized in a vehicle.
2. Description of the Related Art
In recent years, the issues such as environment preservation and fuel depletion. have been raised; measures for these issues are urgently required also in the automobile industry. The measures include, as an example, ultra-lean-combustion (sometimes referred to as stratified-lean-combustion) operation of an internal combustion engine that utilizes a stratified air-fuel mixture. However, in the stratified-lean-combustion operation of an internal combustion engine, the distribution of inflammable fuel-air mixtures may vary in the combustion chamber of the internal combustion engine; therefore, there exists a problem that the ignition plug is liable to smolder. In particular, in spray-guide-type stratified-lean-combustion operation where an unburned fuel is directly sprayed toward an ignition plug, smolder of the ignition plug occurs conspicuously.
When an ignition plug smolders, the ignition energy leaks to the ground level (referred to as a GND level, hereinafter) through conductive carbon or iron oxide that form the smolder, and hence the gap between a center electrode, which is a first electrode of the ignition plug, and a second electrode of the GND level is not led to a breakdown (sometimes referred to as a flashover, hereinafter); therefore, no spark discharge occurs, or it takes a superfluous time by the time the gap is led to a flashover where a spark discharge occurs. As a result, there is posed a defect that, for example, the output decreases because the actual ignition timing is delayed. Moreover, it takes a superfluous time by the time the gap is led to a flashover where a spark discharge occurs; thus, even should the gap between the electrodes of the ignition plug is led to a flashover, the spark discharge can be maintained just for a short time. As a result, there has been a problem that because ignition of the inflammable fuel-air mixture is not stabilized, the ignition performance or the combustion performance is deteriorated.
Furthermore, because in recent years, there has been a tendency that an ignition plug becomes slimmer or becomes to have a longer reach, the to-the-ground static capacity of the ignition plug is likely to increase; therefore, along with the effect of an increase, in the required voltage for the ignition plug, that is caused by an increase in the compression ratio of an internal combustion engine, the creation of an energy leak path due to the smolder of the ignition plug has been more and more affecting the ignition performance of the internal combustion engine.
Accordingly, in order to solve the foregoing problems caused by the smolder of an ignition plug, there has been proposed an ignition apparatus disclosed in Patent Document 1. In the conventional ignition apparatus disclosed in Patent Document 1, even at the timing when no combustion of an inflammable fuel-air mixture is carried out, the ignition plug performs a spark discharge so that a smolder of the ignition plug is prevented from developing and the smolder is burned out.
[Patent Document 1] Japanese Patent No. 3917185
However, although it can decrease the frequency of occurrence of a ignition-plug smolder, the conventional ignition apparatus disclosed in Patent Document 1 cannot completely suppress or remove the smolder; thus, there still exists the problem that the occurrence of a smolder deteriorates the ignition performance or the combustion performance.
The present invention has been implemented in order to solve the foregoing problems in a conventional ignition apparatus; the objective thereof is to provide an ignition control apparatus that can securely produce a spark discharge even when a smolder is produced in an ignition plug.
An ignition control apparatus according to the present invention includes an ignition plug that is provided with a first electrode and a second electrode that face each other by the intermediary of a gap and that produces a spark discharge in the gap so that a inflammable fuel-air mixture inside a combustion chamber of an internal combustion engine is ignited, when a predetermined high voltage is applied to the first electrode; an ignition coil device that generates the predetermined high voltage, by accumulating energy and releasing the accumulated energy, and that applies the generated predetermined high voltage to the first electrode; a current detection device that applies a bias voltage to the first electrode and detects a current that flows in the first electrode based on the applied bias voltage; a smolder level detection device that detects a level of a smolder produced in the ignition plug, based on a value of the current detected by the current detection device; and a control device that controls, based on a smolder level detected by the smolder level detection device, at least one of the timing of ignition, the number of ignition events per power stroke of the internal combustion engine, and the amount of energy accumulated in the ignition coil device.
An ignition control apparatus according to the present invention is provided with a control device that controls, based on a smolder level detected by the smolder level detection device, at least one of the timing of ignition, the number of ignition events per power stroke of the internal combustion engine, and the amount of energy accumulated in the ignition coil device; therefore, ignition can securely be performed under the circumstances where a smolder is produced. As a result, extinction of the internal combustion engine is prevented so that decrease in the output is suppressed; concurrently, deleterious components can be prevented from being exhausted to the air, and increase in the consumption of the fuel can be prevented.
The foregoing and other object, features, aspects, and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.
In general, the internal combustion engine 100 mounted in a vehicle is configured as a multi-cylinder internal combustion engine provided with a plurality of combustion chambers; however, in this embodiment, only one of the plurality of combustion chambers is illustrated.
An ignition coil device 102 produces a high voltage for ignition, based on an instruction from a control device 103 and supplies the produced high voltage to the central electrode 101a of the ignition plug 101. A current detection device 104 produces a voltage, which is different from the high voltage for ignition, and supplies the produced voltage, as a bias voltage, to the central electrode 101a of the ignition plug 101; the current detection device 104 detects a current that flows, based on the supplied bias voltage, in the gap between the central electrode 101a and the GND electrode 101b, and generates an output voltage corresponding to the value of the detected current.
A smolder level detection device 105 determines the smolder level of a smolder produced in the ignition plug 101, based on the level of the output voltage from the current detection device 104, and inputs the determination result to the control device 103. The control device 103 is a device for controlling the operation of the ignition coil device 102; based on the result of smolder level determination by the smolder level detection device 105, the control device 103 controls at least one of the ignition timing, which is a timing of a spark discharge by the ignition plug 101, the number of ignition events per power stroke of the internal combustion engine 100, and the amount of energy stored in the ignition coil device 102. In the ignition control apparatus according to Embodiment 1, the control device 103 performs the foregoing control by correcting the immediately previous control amount.
Next, there will be explained the specific configuration of an ignition control apparatus according to Embodiment 1 of the present invention.
The current detection device 104 is configured with a first Zener diode 201, one end of which is connected with the other end of the secondary coil 102b of the ignition coil device 102; a second Zener diode 203, one end of which is connected with the other end of the first Zener diode 201 and the other end of which is connected with the GND-level portion of the vehicle; a resister 204 connected across the first Zener diode 201; a capacitor 202, one end of which is connected with the connection point between the resister 204 and the second Zener diode 203 and the other end of which is connected with the GND-level portion of the vehicle; and an operational amplifier 301, the input terminal IN3 of which is connected with one end of the resister 204 and the input terminal IN2 of which is connected with the other end of the resister 204. From its output terminal OU1, the operational amplifier 301 outputs an output voltage corresponding to the voltage across the resister 204, which is inputted through the input terminals IN2 and IN3.
The smolder level detection device 105 is configured with a microprocessor (referred to as an MPU, hereinafter) 302 and an A/D converter 303; the output voltage of the current detection device 104 is converted into a digital signal by the A/D converter 303 and inputted to MPU 302. The method for smolder level detection by the smolder level detection device 105 will be described later.
The control device 103 is configured with MPU 302 and an interface circuit (referred to as an I/F circuit, hereinafter) 304, and supplies a control signal, described later, to the gate electrode of IGBT 102d in the ignition coil device 102.
In addition, in
Next, the operation of the ignition control apparatus according to Embodiment 1 of the present invention will be explained.
In
At first, the case where no smolder is produced in the ignition plug 101 will be explained. In
When the primary current I1 flows in the primary coil 102a, magnetic energy is stored in the iron core 102c of the ignition coil device 102. When at the timing T1, the primary current I1 starts to flow in the primary coil 102a, a voltage is induced across the secondary coil 102b, and the voltage across the secondary coil 102b continues to rise in the positive direction until the iron core 102c is magnetically saturated; however, the voltage rise is not represented in the waveform of the central-electrode voltage B in
Next, when at the timing T2, the level of the control signal A is changed from H level to L level, IGBT 102d turns OFF and the primary current I1 that has been flowing in the primary coil 102a is cut off, so that release of the magnetic energy stored in the iron core 102c begins. Due to the release of the magnetic energy, charging of the to-the-ground static capacity formed of the ignition plug 101 and the like is started, so that the voltage applied to the central electrode 101a increases in the negative direction as represented in the waveform of the central-electrode voltage B in
Next, at the timing T3, the central-electrode voltage B reaches a breakdown voltage, which is a predetermined high voltage; a dielectric breakdown is caused in the gap between the central electrode 101a and the GND electrode 101b, resulting in a spark discharge; then, the discharge current C instantaneously flows between these electrodes. The discharge electrode C flows through the path consisting of the GND electrode 101b, the central electrode 101a, the secondary coil 102b, the first Zener diode 201, the capacitor 202, and the GND, in that order, thereby charging the capacitor 202.
After a discharge begins at the timing T3, the central-electrode voltage B almost instantaneously lowers from the breakdown voltage to a discharge maintaining voltage. The discharge between the central electrode 101a and the GND electrode 101b is maintained by the discharge maintaining voltage. In this situation, the time between the timings T3 and t4 is a discharge duration t. At the timing t4, the charging voltage across the capacitor 202 reaches the breakdown voltage of the second Zener diode 203; the discharge current C flows to the GND by way of the second Zener diode 203; then, the discharge between the central electrode 101a and the GND electrode 101b stops.
At the timing T4, the discharge between the central electrode 101a and the GND electrode 101b stops; however, after the timing T4, the voltage that has been charged across the capacitor 202 is applied, as a bias voltage V0, to the central electrode 101a. However, in the case where no smolder is produced, for example, on the surface of the insulating supporter 101c between the central electrode 101a and the GND electrode 101b, no leakage current caused by a smolder flows in the space between the central electrode 101a and the GND-level portion. Accordingly, as the output voltage D of the current detection device 104, there is generated only a mount-shaped voltage 301 based on a current that flows through ions produced by combustion immediately after the timing T4 at which the discharge ends; when the ions disappear, the output voltage D becomes “0”.
Next, the case where a smolder is produced in the ignition plug 101 will be explained. When due to a smolder, a conductive substance is formed, for example, on the surface of the insulating supporter 101c between the central electrode 101a and the GND electrode 101b, a leakage current flows to the GND through the path consisting of the capacitor 202, the resister 204, the secondary coil 102b, the central electrode 101a, a leakage path produced by the conductive substance caused through the smolder, and the GND electrode 101b, in that order. The leakage current is detected, as a potential difference across the resister 204, by the operational amplifier 301; the output voltage Dl corresponding to the value of the detected potential difference is outputted from the current detection device 104.
MPU 302 receives the output voltage D1 outputted from the current detection device 104 by way of the A/D converter 303 in the smolder level detection device 105; based on the output voltage D1, the smolder level is calculated. The method of calculating the smolder level will be described later.
Here, there will be explained the central-electrode voltage at a time when a smolder is produced in the ignition plug 101 and an energy leakage path is formed in the space between the central electrode 101a and the GND.
In order to produce a flashover between the central electrode 101a and the GND electrode 101b, it is required that as described above, mainly the to-the-ground static capacity formed between the central electrode 101a and the GND-level portion is charged, as represented in
However, in the recent years, there has been a tendency that for the purpose of improving the thermal efficiency of an internal combustion engine, the compression ratio of the internal combustion engine is raised; therefore, the pressure inside a cylinder is extremely high when the piston is approximately at the top death center. Accordingly, as described in Paschen's Law, the dielectric breakdown voltage increases by AV corresponding to the increase in the pressure inside the cylinder. In other words, in the case where the pressure inside the cylinder rises when the piston is approximately at the top death'center and hence the compression ratio of the internal combustion engine becomes high, the foregoing flashover is caused; thus, more energy is required.
There has been a tendency that the shape of the ignition plug becomes thinner and the length thereof becomes longer as the structure of an internal combustion engine becomes more complex; this fact, at the same time, leads to the increase in the to-the-ground static capacity of the ignition plug. When the to-the-ground static capacity of the ignition plug increases, the speed of charging the to-the-ground static capacity decreases and hence the time instant when the charging is completed is delayed along the direction indicated by the arrow 411; due to this delay and the foregoing increase ΔV in the dielectric breakdown voltage, the energy required for the dielectric breakdown voltage to be reached largely increases. The middle-thick solid line in
When under the foregoing severe environment, a smolder causes a leakage path to be produced in an ignition plug, the time instant when the charging is completed is further delayed along the direction indicated by the arrow 412; the central-electrode voltage is represented as the curve B11 indicated by the thickest solid line in
The waveform of the central-electrode voltage B1 represented in
The ignition control apparatus according to Embodiment 1 of the present invention can solve the foregoing problems at a time when a smolder is produced.
In the case where a smolder is produced, the bias voltage V0 based on the voltage across the foregoing capacitor 202 is applied to the central electrode 101a in the duration other than the ignition discharge operation duration from T1 to T14; thus, by way of a leakage path formed of the smolder, a leakage current flows from the central electrode 101a to the cylinder block, of the internal combustion engine, that is a GND-level portion. Therefore, in the duration other than the ignition discharge operation duration from T2 to T14, the output voltage D1 of the current detection device 104 becomes a value approximately corresponding to the smolder level L.
Immediately after the timing T4, the output voltage D1 of the current detection device 104 includes the waveform 301 caused by combustion; because it is difficult to distinguish a leakage signal from the waveform 301, the smolder level detection device 105 calculates the smolder level L by reading the voltage value at a time instant in the vicinity of the timing T15 at which combustion has been completed or at a time instant in the vicinity of the timing T10 at which the combustion has not been started.
The smolder level L is expressed, for example, by a resistance value; assuming that the charging voltage across the capacitor 202 is 100[V], the resistance value of the resister 204 is 1 [kΩ], the resistance value of the primary coil 102a is 5[kΩ], and the value of the output voltage D1 of the current detection device 104 is 1[V], the smolder level L is calculated through the following equation.
L=(100[V]−1[V])÷{(1[V]÷(1 [kΩ]+5 [kΩ])}=594 [kΩ]
Here, as far as the smolder level L is concerned, the smaller its value is, the higher the smolder level is.
In addition, the smolder level L may be expressed by the value of a leakage current or by the value of a voltage across the resister 204, instead of a resistance value. In this case, the larger the value of the smolder level L is, the higher the smolder level is.
In the step S501 in
That is to say, the foregoing map MAP1 is a map in which corresponding to the value of the smolder level L, there is set the energization time correction amount CDWEL for correcting the output time of the control signal A represented in
Next, in the step S503, based on the foregoing correction amounts obtained in the step S502, the respective control amounts are corrected. That is to say, the control device 103 generates a new energization time control amount CDEL obtained through the duration from the timing T21 to the timing T22, by correcting the period (time) from the timing T1 to the timing T2 corresponding to an uncorrected energization time control amount DWEL, based on the energization time control amount CDWEL. Moreover, the control device 103 generates a new cutoff timing control amount IG, by correcting an uncorrected cutoff timing control amount IG corresponding to the timing T2, based on the cutoff timing correction amount CIG. Furthermore, the control device 103 generates a new ignition count control amount MIG, by correcting an uncorrected ignition count control amount MIG, based on the ignition count correction amount CMIG.
Next, the operation of the ignition control apparatus according to Embodiment 1 of the present invention will further be explained with reference to the timing chart in
In other words, when a smolder is produced, a dielectric breakdown requires a large energy, as described above. Accordingly, in order to lengthen the energization duration DWEL, which is a time for accumulating magnetic energy in the ignition coil device 102, the timing at which the control signal A2 is raised from L level to H level is advanced from T1 to T21, by correcting the energization duration DWEL at a time when no smolder is produced, based on the energization time correction amount CDWEL.
When a smolder is produced, the time in which the dielectric breakdown voltage is reached becomes longer, as described above; thus, the cutoff timing IG for the primary current I1 that flows in the primary coil 102a is corrected in such a way as to advance, for example, from T2 to T22. In such a way as described above, the timings of the dielectric breakdown, i.e., the so-called ignition timings T3 and T23 can be set at approximately the same time instant.
In the case where no smolder is produced, the discharge duration t immediately after a flashover is a period from the timing T3 to the timing T4; however, in the case where a smolder is produced, the timing T13 of the dielectric breakdown is delayed and hence the residual magnetic energy decreases. As a result, the discharge duration t1 becomes a period from the timing T13 to the timing T14, whereby it becomes shorter than its counterpart at a time when no smolder is produced. Accordingly, multi ignition is performed so that the energy at a time when a smolder is produced becomes the same as the energy that is supplied to an inflammable fuel-air mixture when no smolder is produced. In the example represented in
That is to say, after the first ignition is performed at the timing T23, the level of the control signal A2 is raised from L level to H level at the timing T24 so that the primary current I1 is applied to the primary coil 102a and hence magnetic energy is again accumulated in the ignition coil device 102. Then, at the timing T25, the control signal A2 is lowered from H level to L level in order to cut off the primary current I1 so that the accumulated magnetic energy is again released and the second ignition is performed. In this case, because a flashover has been already produced at the timing T13, the second ignition is performed at the timing T25 only by raising the voltage of the central electrode 101a up to the discharge maintaining voltage. Then, the discharge is ended at the timing T26.
In the case of this multi ignition, the discharge duration t2 is given by the following equation.
t2(T3 to T4)≈t21(T23 to T24)+t22 (T25 to T26)
Here, after and including the second ignition, the energization duration (T24 to T25) of the primary current I1 may be a predetermined fixed value; alternatively, a value determined in accordance with the smolder level L may preliminarily be set in a map, or a variable may be adopted, instead of the map.
As described above, the ignition control apparatus according to Embodiment 1 of the present invention makes it possible that even when a smolder is produced, there can be performed ignition that is equivalent to ignition at a time when no smolder is produced.
An ignition control apparatus according to the present invention is mounted in an automobile, a motorcycle, an outboard engine, an extra machine, or the like utilizing an internal combustion engine, and is capable of securely performing appropriate ignition even when a smolder is produced in an ignition plug; therefore, extinction of the internal combustion engine can be prevented, and decrease in the output can be suppressed. As a result, deleterious components are prevented from being exhausted to the air, and the fuel consumption can be prevented from increasing; thus, the present invention can contribute to environment preservation.
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 |
|---|---|---|---|
| 2011-227646 | Oct 2011 | JP | national |
