JP6350135B2 - Ignition device and ignition method for internal combustion engine - Google Patents

Description

  According to the present invention, a primary current is supplied to and cut off from the primary coil of the ignition coil to generate a discharge voltage between the electrodes of the spark plug connected to the secondary coil, and after the discharge by the secondary coil is started, The present invention relates to an ignition device and an ignition method for an internal combustion engine in which a superimposed voltage in the same direction as the discharge voltage is applied between electrodes of a spark plug to continue the discharge current.

  In an ignition device using an ignition coil, a primary discharge current is applied to the primary coil, and then the primary current is cut off at a predetermined ignition timing, thereby generating a high discharge voltage in the secondary coil and A discharge is generated between the electrodes of the connected spark plug. The discharge voltage and discharge energy generated in the secondary coil basically correspond to the energization time to the primary coil.

  Patent Documents 1 and 2 disclose a technique in which a superimposed voltage by another booster circuit is applied to a spark plug over a discharge period after the ignition timing in order to increase the discharge period and obtain reliable ignition. . In this case, after the discharge between the electrodes is started by the secondary voltage by the ignition coil, the discharge current is continued by the overlap voltage, and a larger amount of energy is given to the air-fuel mixture.

Japanese Patent No. 2554568 JP 2013-151866 A

  The application of the overlap voltage as described above is effective for improving the ignition performance under conditions where a large amount of exhaust gas recirculation is performed, for example. If the superimposed voltage is not applied normally during the operation, misfire or instability of combustion will occur.

  Therefore, there is a need for a technique for diagnosing whether or not the application of the superimposed voltage functions correctly.

  Here, when applying the overlap voltage, the discharge time becomes longer due to the overlap of the overlap voltage as described above. However, the discharge time itself is different for each cycle both when the overlap voltage is applied and when the overlap voltage is not applied. Variation is large. Therefore, if the discharge time is simply compared with the threshold value, the probability of erroneous determination is high and correct diagnosis cannot be performed.

The present invention generates a discharge voltage between the electrodes of the spark plug connected to the secondary coil by energizing and interrupting the primary current to the primary coil of the ignition coil,
In the ignition device or ignition method for an internal combustion engine in which a discharge current is continued by applying a superimposed voltage in the same direction as the discharge voltage between the electrodes of the ignition plug after the start of discharge by the secondary coil.
The secondary current flowing between the electrodes is monitored to obtain a discharge time at a predetermined secondary current threshold, and the discharge time is compared with a predetermined discharge time threshold to determine whether or not the superimposed voltage is applied. .

  That is, according to the present invention, the secondary current threshold value is set to an appropriate current level, and the discharge time at the secondary current threshold value is compared with a predetermined discharge time threshold value, thereby determining whether or not the superimposed voltage is applied.

  When the superposed voltage is not applied, the waveform of the secondary current is approximately triangular, and the cycle variation appears such that the waveform of this approximately triangular shape changes. On the other hand, when the superimposed voltage is applied, the waveform of the secondary current has a stepped shape, and the cycle variation appears so that it changes in a substantially similar shape. Therefore, by setting the secondary current threshold to an appropriate intermediate current level, it is possible to determine whether or not the overlap voltage is applied without being affected by the cycle variation.

  According to the present invention, it can be determined during engine operation whether or not the superimposed voltage is actually applied. Therefore, the failure of the superimposed voltage function can be self-diagnosed, and for example, misfire can be avoided in advance.

BRIEF DESCRIPTION OF THE DRAWINGS The structure explanatory drawing of the internal combustion engine provided with the ignition device of one Example of this invention. Structure explanatory drawing which shows the structure of an ignition device. FIG. 3 is a configuration explanatory view showing details of an ignition unit of each cylinder. The waveform diagram of secondary voltage etc. at the time of non-application and application of an overlap voltage. The wave form diagram which shows the characteristic of the secondary current at the time of a superimposed voltage application, and its cycle dispersion | variation. The wave form diagram which shows the characteristic of the secondary current at the time of non-application of an overvoltage, and its cycle dispersion | variation. Explanatory drawing of secondary current threshold value AG. Explanatory drawing which shows distribution of the discharge time in each secondary current threshold value AG. Explanatory drawing which showed the characteristic of the secondary current at the time of a superimposed voltage application, and the characteristic of the secondary current at the time of a superimposed voltage non-application superimposed. Explanatory drawing explaining the relationship between the peak value of a secondary current, and a secondary current threshold value. The flowchart which shows 1st Example of this invention. Explanatory drawing which shows the time series data (a) of the discharge time which changes for every cycle, and the data (b) after carrying out the leveling process. The characteristic view which shows the relationship between the in-cylinder gas flow velocity and discharge time in ignition timing. The characteristic view which shows the relationship between the in-cylinder gas density and discharge time in an ignition timing. The characteristic view which shows the relationship between discharge gap length and discharge time. The characteristic view which shows the relationship between the in-cylinder gas pressure and the discharge time at the ignition timing. The characteristic view which shows the characteristic of the discharge time threshold value with respect to the cylinder gas flow velocity in ignition timing. The characteristic view which shows the characteristic of the discharge time threshold value with respect to in-cylinder gas density in ignition timing. The characteristic view which shows the characteristic of the discharge time threshold with respect to discharge gap length. The characteristic view which shows the characteristic of the discharge time threshold value with respect to in-cylinder gas pressure in ignition timing. The flowchart which shows 2nd Example of this invention. The characteristic view which shows the characteristic of the cylinder gas flow velocity with respect to ignition timing and rotation speed. Explanatory drawing of the discharge time of the secondary current used as the detection object for gap length estimation.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a configuration explanatory view showing a system configuration of an internal combustion engine 1 equipped with an ignition device according to the present invention, wherein a piston 3 is arranged in each of a plurality of cylinders 2 of the internal combustion engine 1, An intake port 5 that is opened and closed by the intake valve 4 and an exhaust port 7 that is opened and closed by the exhaust valve 6 are connected to each other. In addition, a fuel injection valve 8 is provided for injecting and supplying fuel into the cylinder. The fuel injection timing and fuel injection amount of the fuel injection valve 8 are controlled by an engine control unit (ECU) 10. In order to ignite the air-fuel mixture generated in the cylinder by the fuel injection valve 8, a spark plug 9 is disposed at the center of the ceiling surface, for example. The illustrated example is configured as an in-cylinder direct injection internal combustion engine, but a port injection configuration in which a fuel injection valve is disposed in the intake port 5 may be used. The engine control unit 10 receives detection signals from a number of sensors such as an air flow meter 21 that detects the intake air amount, a crank angle sensor 22 that detects the engine speed, and a temperature sensor 23 that detects the coolant temperature. Has been.

  The ignition plug 9 is connected to an ignition unit 11 that outputs a discharge voltage to the ignition plug 9 in response to an ignition signal from the engine control unit 10. Further, an overlap voltage control unit 12 is provided for controlling the overlap voltage by the ignition unit 11 in response to the overlap voltage request signal from the engine control unit 10. The engine control unit 10, the ignition unit 11, and the overlap voltage control unit 12 are connected to an in-vehicle 14-volt battery 13.

  As shown in detail in FIGS. 2 and 3, the ignition unit 11 includes an ignition coil 15 including a primary coil 15 a and a secondary coil 15 b (see FIG. 3), and a primary current to the primary coil 15 a of the ignition coil 15. It includes an igniter 16 that controls energization / cutoff, and a superimposed voltage generation circuit 17 (see FIG. 2) including a booster circuit. A spark plug 9 is connected to the secondary coil 15 b of the ignition coil 15. The overlap voltage generation circuit 17 boosts the voltage of the battery 13 to a predetermined overlap voltage, and then overlaps the spark plug 9 after starting the discharge of the spark plug 9 based on the control signal of the overlap voltage control unit 12. Output voltage. The overlap voltage generation circuit 17 generates an overlap voltage in the direction of the same potential as the original discharge voltage generated between the electrodes of the spark plug 9 when the primary current to the primary coil is interrupted. In the example of FIG. 2, the overlap voltage generation circuit 17 is built in the ignition unit 11 together with the ignition coil 15, but a configuration in which the overlap voltage generation circuit 17 is provided separately from the ignition unit 11 may be employed. .

  As shown in FIG. 3, a secondary current detection resistor 20 is provided in series with the secondary coil 15b in order to monitor the secondary current flowing between the electrodes of the spark plug 9 during discharge. A signal indicating the secondary current of each cylinder detected through the secondary current detection resistor 20 is input to the engine controller 10 and monitored by the engine controller 10.

  FIG. 4 illustrates changes in the secondary current (discharge current) depending on whether or not the overlap voltage is applied. The primary current (primary coil energization signal), the overlap voltage, The waveforms of the secondary voltage and the secondary current are collectively shown.

  When the superimposed voltage is not applied, the operation is the same as that of a general ignition device. That is, the primary current is supplied to the primary coil 15 a of the ignition coil 15 through the igniter 16 for a predetermined energization time. Along with the interruption of the primary current, a high discharge voltage is generated in the secondary coil 15b, and a discharge is generated between the electrodes of the spark plug 9 with dielectric breakdown of the air-fuel mixture. Specifically, a very high voltage capacitive discharge occurs instantaneously, followed by an induction discharge. During the induction discharge, the secondary current flowing between the electrodes decreases relatively abruptly in a triangular wave shape with the passage of time from the start of the discharge.

  On the other hand, when applying the overlap voltage, supply of the overlap voltage is started almost simultaneously with the interruption of the primary current, and a constant overlap voltage is superimposed for a predetermined period. Thereby, as shown in the drawing, the secondary current continues at a high level for a relatively long period from the start of discharge.

  In the present embodiment, such superposed voltage is used to improve the ignitability in the high EGR operation region.

  5 and 6 show the variation of the secondary current for each cycle. In these drawings and FIGS. 7, 9, and 10 described later, the positive and negative signs are reversed. FIG. 5 shows the characteristics at the time of applying the overlap voltage. The overlap voltage command signal shown in FIG. 5A is turned on for a predetermined period from the ignition timing. Due to the superposition of the superposed voltage based on this superposed voltage command, the secondary current becomes a stepped waveform as shown in (b), but the actual characteristics are caused by the variation for each cycle based on various conditions. Are different from each other as shown in, for example, a1 to a6. That is, if the delay time (actual overlap voltage application delay time shown in FIG. 10) from the ON of the overlap voltage command signal to the stepwise change due to the superposition of the actual overlap voltage is short, as shown in a1, the secondary current is , The discharge time until the secondary current becomes zero becomes longer, while being kept constant at a high current value. On the contrary, if the delay time until the step change is long, as shown in a6, the value of the secondary current in the region where it is held constant decreases, and the discharge time until the secondary current becomes zero is shown. Shorter.

  FIG. 6 shows the characteristics when no overlap voltage is applied (when the overlap voltage application function fails). Since no overlap voltage is applied, the secondary current has a triangular wave shape, but is based on various conditions. Depending on the variation for each cycle, the actual characteristics are different as shown in b1 to b5, for example. That is, the rate of decrease of the secondary current changes while maintaining a substantially triangular wave shape, and the discharge time until the secondary current becomes 0 changes long and short.

  FIG. 7 is an explanatory diagram when the current threshold value is set to the current value level of A to G with respect to the characteristics of the secondary current changing as described above, and the discharge time at each of the current threshold values A to G is as follows. The secondary current waveform is represented by the length that the broken lines of the current thresholds A to G cross. Since the waveform of the secondary current changes in the range of the characteristics a1 to a6 when the superimposed voltage is applied, the discharge time at each of the current thresholds A to G also changes in the range of the characteristics a1 to a6. When the superimposed voltage is not applied, the waveform of the secondary current changes in the range of characteristics b1 to b5, so that the discharge time at each of the current thresholds A to G also changes in the range of characteristics b1 to b5.

  FIG. 8 is an explanatory diagram illustrating the distribution due to cycle fluctuations of the discharge time in each of the current thresholds A to G obtained as shown in FIG. 7, with the horizontal axis representing the current threshold and the vertical axis representing the discharge time. Solid lines LA to LG shown with squares in the figure show the distribution of discharge time at each of the current thresholds A to G when a superimposed voltage is applied. Solid lines MA to MG shown with circles in the figure indicate the distribution of discharge time at each of the current thresholds A to G when no overlap voltage is applied (at the time of failure).

  In FIG. 8, for example, the solid line LA and the solid line MA indicating the discharge time distribution at the current threshold A partially overlap each other. This means that the magnitude relationship between the two may be reversed due to cycle variations. Therefore, depending on the length of the discharge time until the secondary current becomes 0 (that is, the threshold value A), it may be overlapped with the time of applying the overlapping voltage. This means that it cannot be distinguished from when no voltage is applied (at the time of failure).

Similarly, the current threshold B Contact and current threshold E, F, for also G, it is difficult to clearly identify the two.

On the other hand, for example, the solid line LC indicating the discharge time distribution at the current threshold C is sufficiently separated from the solid line MC. This means that even when there is a cycle variation, it is possible to clearly distinguish when the overlap voltage is applied and when the overlap voltage is not applied (at the time of failure) based on the length of the discharge time. The same applies to the current threshold D.

  In this manner, as shown in the figure, it is possible to define a failure determination possible region between the discharge time distribution when the overlap voltage is applied and the discharge time distribution when the overlap voltage is not applied. Accordingly, a determination secondary current threshold is set between the lower limit secondary current value X and the upper limit secondary current value Y corresponding to both ends of the failure determination possible region, and the discharge time at the secondary current threshold is set to a predetermined value. It is possible to determine whether or not the overlap voltage is actually applied by comparing with the discharge time threshold value.

  FIG. 9 is a diagram illustrating the secondary current characteristics when the superimposed voltage is applied as shown in FIG. 5 and the secondary current characteristics when the superimposed voltage is not applied as shown in FIG. FIG. As shown in the figure, the region where the respective characteristics in consideration of cycle fluctuations remain without overlapping corresponds to the failure determination possible region.

  The upper limit secondary current value Y is, for example, at least 40 percent of the peak value (Imax) of the secondary current. As shown in FIG. 10, this corresponds to the secondary current value due to the overlap voltage when the above-described actual overlap voltage application delay time reaches a predetermined limit. At a level where the discharge current (secondary current) due to the superposition of the superposed voltage is less than 40% of the secondary current peak value Imax, the effect of improving the combustion resistance due to the superposed voltage cannot be enjoyed in the first place. However, it is necessary to design so that the discharge current level due to the superposition of the superposed voltage does not become less than 40% of the peak value Imax. Correspondingly, the upper limit secondary current value Y is 40% or more of the peak value Imax. Become. Note that the peak value Imax does not include the spike-shaped portion indicated by the symbol Z in FIG.

  Next, FIG. 11 is a flowchart showing a specific processing flow of the first embodiment in which the diagnosis of the superimposed voltage function is performed to determine whether exhaust gas recirculation is possible. This process is executed in the exhaust gas recirculation region, which is an engine operating condition where a superimposed voltage is applied.

  In step 1, the value of the secondary current detected via the secondary current detection resistor 20 is read. In step 2, the discharge time NowTd at a predetermined secondary current threshold is calculated from the read change in the secondary current. To do. Here, as described above, the secondary current threshold value is appropriately set within the range of the failure determination possible region, that is, between the lower limit secondary current value X and the upper limit secondary current value Y.

  In step 3, a discharge time threshold value Td_fail is set. This discharge time threshold value Td_fail corresponds to the secondary current threshold value used in step 1, so that even when there is a cycle variation as shown in FIG. For example, it is set to an intermediate value between both distributions.

  In step 4, the discharge time NowTd is compared with the discharge time threshold Td_fail. Here, if the discharge time NowTd is equal to or greater than the discharge time threshold Td_fail, it can be determined that the superimposed voltage is normally applied, so the process proceeds to step 5 and exhaust gas recirculation is permitted. In step 6, the target exhaust gas recirculation rate is calculated.

  On the other hand, if the discharge time NowTd is less than the discharge time threshold value Td_fail, it is determined that the superimposed voltage function has failed. Accordingly, the process proceeds to step 7 and exhaust gas recirculation is prohibited. Thereby, misfire and combustion instability due to exhaust gas recirculation are avoided. At the same time, the failure may be notified by turning on a warning lamp or the like. Further, the exhaust gas recirculation rate may be limited to be lower than that in the normal state, instead of completely stopping the exhaust gas recirculation.

  Here, the comparison between the discharge time NowTd and the discharge time threshold value Td_fail may be performed for each cycle. Preferably, the time series data of the discharge time at the predetermined secondary current threshold value obtained for each cycle is leveled. It is good to compare with a predetermined discharge time threshold value after performing the conversion process. FIG. 12 is an explanatory diagram showing a comparison between time-series data (a) of discharge time at a predetermined secondary current threshold that varies from cycle to cycle and data (b) after the leveling process. is there. Here, the characteristics D1 and D2 when the superimposed voltage is applied and the characteristics d1 and d2 when the superimposed voltage is not applied (at the time of failure) are shown together.

  As shown in the figure, although the fluctuation for each cycle is relatively large in the time-series data (a) as it is, by performing a leveling process using, for example, a weighted average, two characteristics D2 are obtained as shown in (b). , D2 is increased in S / N ratio, and the determination accuracy is improved.

  Next, the discharge time threshold Td_fail is determined using at least one of the in-cylinder gas flow velocity at the ignition timing, the in-cylinder gas density at the ignition timing, the in-cylinder gas pressure at the ignition timing, and the gap length between the electrodes of the spark plug. A description will be given of a second embodiment in which correction is made.

  The discharge time of the secondary current, particularly the discharge time in induction discharge, is affected by the gas flow rate in the cylinder. There are three highly sensitive parameters that affect the discharge time: the in-cylinder gas flow rate at the ignition timing, the in-cylinder gas density (or in-cylinder gas pressure) at the ignition timing, and the discharge gap length.

  FIG. 13 shows the result of determining the relationship between the in-cylinder gas flow rate at the ignition timing and the discharge time under the conditions that the in-cylinder gas density and the gap length at the ignition timing are constant. As shown in the figure, the higher the in-cylinder gas flow rate, the shorter the discharge time.

  FIG. 14 shows the result of determining the relationship between the in-cylinder gas density at the ignition timing and the discharge time under the conditions that the in-cylinder gas flow velocity and the gap length at the ignition timing are constant. As shown, the higher the in-cylinder gas density, the shorter the discharge time.

  FIG. 15 shows the result of obtaining the relationship between the gap length and the discharge time under the condition that the cylinder gas density at the ignition timing and the cylinder gas flow velocity at the ignition timing are constant. As shown in the figure, the larger the gap length, the shorter the discharge time.

  FIG. 16 shows the result of determining the relationship between the in-cylinder gas pressure at the ignition timing and the discharge time under the conditions that the in-cylinder gas flow velocity and the gap length at the ignition timing are constant. As shown, the higher the in-cylinder gas pressure, the shorter the discharge time.

  Therefore, it is desirable to correct the discharge time threshold Td_fail so as to eliminate the influence of these parameters.

  FIG. 17 shows the characteristics of the corrected discharge time threshold Td_fail for the in-cylinder gas flow rate at the ignition timing under the condition that the in-cylinder gas density and the gap length at the ignition timing are constant. As shown in the figure, the discharge time threshold Td_fail is set to be lower as the in-cylinder gas flow rate is higher.

  FIG. 18 shows the characteristics of the corrected discharge time threshold Td_fail with respect to the in-cylinder gas density at the ignition timing under the condition that the in-cylinder gas flow velocity and the gap length at the ignition timing are constant. As shown in the figure, the discharge time threshold Td_fail is set to be lower as the in-cylinder gas density is higher.

  FIG. 19 shows the characteristics of the corrected discharge time threshold Td_fail with respect to the gap length between the electrodes under the condition that the in-cylinder gas density at the ignition timing and the in-cylinder gas flow velocity at the ignition timing are constant. As shown in the figure, the discharge time threshold Td_fail is set to be lower as the gap length is larger.

  FIG. 20 shows the characteristics of the corrected discharge time threshold Td_fail for the in-cylinder gas pressure at the ignition timing under the condition that the in-cylinder gas flow velocity and the gap length at the ignition timing are constant. As shown in the figure, the discharge time threshold Td_fail is set to be lower as the in-cylinder gas pressure is higher.

  FIG. 21 is a flowchart showing a specific processing flow of the second embodiment in which the diagnosis of the overlap voltage function is performed to determine whether exhaust gas recirculation is possible, and the in-cylinder gas density Ng and the ignition timing at the ignition timing are shown. The discharge time threshold value Td_fail is set based on the three parameters of the in-cylinder gas flow velocity Fg and the gap length Gp. The gap length Gp is estimated from other parameters as will be described later.

  In step 11, the engine operating conditions such as the rotational speed and load of the internal combustion engine 1 and other necessary water temperatures are read. In step 12, based on these conditions, intake pressure P1, ignition timing ADV, valve timing of a variable valve gear (not shown), and the like are determined.

  In step 13, the in-cylinder gas density Ng at the ignition timing is calculated.

  The in-cylinder gas density Ng at the ignition timing can be obtained by the following equation (1) using the in-cylinder gas pressure Pg at the ignition timing and the in-cylinder gas temperature Tg at the ignition timing. C1 is a constant.

Ng = Pg / Tg × C1 (1)
The in-cylinder gas pressure Pg at the ignition timing has the relationship of the following equation (2) with respect to the intake pressure P1, the actual compression ratio εign and the specific heat ratio κ at the ignition timing.

Pg = P1 × εsign ^κ (2)
The in-cylinder gas temperature Tg at the ignition timing has the following equation (3) with respect to the compression start in-cylinder gas temperature T1, the actual compression ratio εign and the specific heat ratio κ at the ignition timing.

Tg = T1 × εsign ^κ−1 (3)
Here, the intake pressure P1 and the specific heat ratio κ can be obtained, for example, with reference to a map or table created in advance using the engine speed and load or the ignition timing as parameters. The intake pressure P1 can be directly detected by providing an intake pressure sensor in the intake collector.

  The compression start in-cylinder gas temperature T1 can be obtained, for example, with reference to a map or table created in advance using the intake air temperature and the oil / water temperature as parameters.

  The actual compression ratio εsign at the ignition timing has the following relationship with the volume Vivc at the intake valve closing timing and the volume Vign at the ignition timing.

εsign = Vivc / Vign (4)
Next, at step 14, the cylinder gas flow rate Fg at the ignition timing is calculated. The in-cylinder gas flow rate has a relationship as shown in FIG. 22 with respect to the crank angle and the engine rotation speed. Therefore, if the ignition timing ADV is determined, the in-cylinder gas flow rate Fg at the ignition timing can be obtained from the relationship of FIG. 22 based on the engine speed at that time.

  In step 15, it is determined whether or not it is an operation region where a superposed voltage is to be applied. If “NO” here, the process proceeds to the steps 16 and 17 to estimate the gap length Gp. The estimation of the gap length Gp will be described later.

  If it is the operation region in which the overlap voltage is to be applied in step 15, the process proceeds to step 18, and the separately estimated gap length Gp is read.

  In step 19, a discharge time threshold value Td_fail is set in consideration of the in-cylinder gas density Ng at the ignition timing, the in-cylinder gas flow rate Fg at the ignition timing, and the gap length Gp based on the relationship shown in FIGS.

In step 20, the discharge time NowTd at a predetermined secondary current threshold value is calculated in the same manner as in the first embodiment described above. In step 21, the discharge time NowTd is compared with the discharge time threshold value Td_fail. If the discharge time NowTd is equal to or greater than the discharge time threshold value Td_fail, it is determined that the overlap voltage is normally applied, and the process proceeds to steps 23 and 24 to allow exhaust gas recirculation and to calculate the target exhaust gas recirculation rate. Do.

On the other hand, discharge time NowTd is less than the discharge time threshold Td_fail, it is determined that the overlapping voltage function is faulty, it prohibits the exhaust gas recirculation in step 2 2.

  Next, the estimation of the gap length Gp performed in steps 16 and 17 will be described.

  First, in step 16, as shown in FIG. 23, based on the secondary current value on which the superimposed voltage is not superimposed, the time during which the secondary current exceeding a predetermined threshold flows is read as the discharge time Tdis. The threshold value is set to an appropriate value so as to avoid erroneous detection, but may be a very small value close to 0. Since the capacity discharge period at the time of dielectric breakdown is very short, the above discharge time Tdis is generally an induction discharge period.

  In step 17, the gap length Gp is estimated using the discharge time Tdis, the in-cylinder gas density Ng at the ignition timing, and the in-cylinder gas flow velocity Fg at the ignition timing.

  That is, as shown in FIGS. 13 to 15, the discharge time Tdis correlates with the in-cylinder gas density Ng at the ignition timing, the in-cylinder gas flow rate Fg at the ignition timing, and the gap length Gp. As a result of multiple regression analysis of a large number of data on the discharge time Tdis, it has been found that the discharge time Tdis can be predicted with high accuracy based on these three parameters having relatively high sensitivity. Therefore, conversely, the gap length Gp at the time of discharge can be estimated based on the three parameters of the in-cylinder gas density Ng at the ignition timing, the in-cylinder gas flow rate Fg at the ignition timing, and the discharge time Tdis.

  The discharge time Tdis can be expressed by the following equation (5).

Tdis = -A * Gp-B * Ng-C * Fg + X (5)
Here, “−A”, “−B”, and “−C” are respective coefficients obtained by multiple regression analysis, and X is a constant obtained by multiple regression analysis.

  Accordingly, the gap length Gp can be obtained by the following equation (6).

Gp = (-Tdis-B.Ng-C.Fg + X) / A (6)
Note that the gap length Gp can be similarly estimated by using the in-cylinder gas pressure Pg at the ignition timing instead of the in-cylinder gas density Ng at the ignition timing.

  Thus, according to the second embodiment, the discharge time threshold value Td_fail is corrected based on the three parameters of the cylinder gas density Ng at the ignition timing, the cylinder gas flow velocity Fg at the ignition timing, and the gap length Gp. Therefore, erroneous determination due to these influences is prevented, and determination accuracy is further increased.

  In the second embodiment, the discharge time threshold value is considered in consideration of all three parameters that affect the discharge time, that is, the in-cylinder gas density Ng at the ignition timing, the in-cylinder gas flow rate Fg at the ignition timing, and the gap length Gp. Although Td_fail is set, the discharge time threshold Td_fail may be set based on any one parameter. In-cylinder gas pressure Pg at the ignition timing may be used instead of the in-cylinder gas density Ng at the ignition timing.

DESCRIPTION OF SYMBOLS 9 ... Spark plug 10 ... Engine control unit 11 ... Ignition unit 12 ... Overlap voltage control unit 15 ... Ignition coil 16 ... Igniter 17 ... Overlap voltage generation circuit 20 ... Resistance for secondary current detection

Claims (6)

An ignition device for an internal combustion engine that generates a discharge voltage between electrodes of an ignition plug connected to a secondary coil by energizing and interrupting a primary current to a primary coil of the ignition coil,
In an internal combustion engine ignition device comprising an overlap voltage generation circuit for continuing a discharge current by applying an overlap voltage in the same direction as the discharge voltage between the electrodes of the ignition plug after the start of discharge by the secondary coil,
The secondary current flowing between the electrodes is monitored to obtain a discharge time at a predetermined secondary current threshold, and the discharge time is compared with a predetermined discharge time threshold to determine whether or not the superimposed voltage is applied. As well as
The secondary current threshold, middle is set to be within a range of the secondary current, the ignition system of the internal combustion engine between a predetermined lower limit secondary current limit and the upper secondary current value. An ignition device for an internal combustion engine that generates a discharge voltage between electrodes of an ignition plug connected to a secondary coil by energizing and interrupting a primary current to a primary coil of the ignition coil,
In an internal combustion engine ignition device comprising an overlap voltage generation circuit for continuing a discharge current by applying an overlap voltage in the same direction as the discharge voltage between the electrodes of the ignition plug after the start of discharge by the secondary coil,
The secondary current flowing between the electrodes is monitored to obtain a discharge time at a predetermined secondary current threshold, and the discharge time is compared with a predetermined discharge time threshold to determine whether or not the superimposed voltage is applied. As well as
The secondary current threshold is set within the range of the secondary current and discharge time distribution do not overlap due to cyclic variation during discharging time distribution and superimposed voltage is applied by the cycle fluctuation during overlapping voltage application, the inner combustion engine Ignition device. The ignition device for an internal combustion engine according to claim 1 , wherein the upper limit secondary current value is at least 40 percent of the secondary current peak value. An ignition device for an internal combustion engine that generates a discharge voltage between electrodes of an ignition plug connected to a secondary coil by energizing and interrupting a primary current to a primary coil of the ignition coil,
In an internal combustion engine ignition device comprising an overlap voltage generation circuit for continuing a discharge current by applying an overlap voltage in the same direction as the discharge voltage between the electrodes of the ignition plug after the start of discharge by the secondary coil,
The secondary current flowing between the electrodes is monitored to obtain a discharge time at a predetermined secondary current threshold, and the discharge time is compared with a predetermined discharge time threshold to determine whether or not the superimposed voltage is applied. As well as
In terms of the time-series data of a discharge time at a given secondary current threshold obtained for each cycle processed leveled, with a predetermined discharge time threshold, the inner combustion engine ignition device. An ignition device for an internal combustion engine that generates a discharge voltage between electrodes of an ignition plug connected to a secondary coil by energizing and interrupting a primary current to a primary coil of the ignition coil,
In an internal combustion engine ignition device comprising an overlap voltage generation circuit for continuing a discharge current by applying an overlap voltage in the same direction as the discharge voltage between the electrodes of the ignition plug after the start of discharge by the secondary coil,
The secondary current flowing between the electrodes is monitored to obtain a discharge time at a predetermined secondary current threshold, and the discharge time is compared with a predetermined discharge time threshold to determine whether or not the superimposed voltage is applied. As well as
The discharge time threshold is corrected using at least one of the in-cylinder gas flow rate at the ignition timing, the in-cylinder gas density at the ignition timing, the in-cylinder gas pressure at the ignition timing, and the gap length between the electrodes of the spark plug . ignition system of the internal combustion engine. By energizing and interrupting the primary current to the primary coil of the ignition coil, a discharge voltage is generated between the electrodes of the spark plug connected to the secondary coil, and
In the ignition method of an internal combustion engine in which a discharge current is continued by applying a superimposed voltage in the same direction as the discharge voltage between the electrodes of the ignition plug after the start of discharge by the secondary coil.
The secondary current flowing between the electrodes is monitored to determine a discharge time at a predetermined secondary current threshold, and the discharge time is compared with a predetermined discharge time threshold to determine whether or not the superimposed voltage is applied ,
Here, the secondary current threshold is set within a range of intermediate current between a predetermined lower limit secondary current value and an upper limit secondary current value,
Ignition method for internal combustion engine.

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