JP2012140924A - Ignition device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ignition device that achieves ignition having superior efficiency of energy.SOLUTION: The device includes: a main ignition coil 20 for generating a spark discharge by applying a voltage to an ignition plug 10 for each combustion cycle of each time; a sub-ignition coil 30 for increasing a discharge current by applying the voltage to the ignition plug 10 after waiting for a delay time TD to pass from the start of discharge by the main ignition coil 20 for each combustion cycle of each time; and an ignition control circuit 50 for setting the delay time TD, which is closely brought to a time TMAX that is the time from the start of discharge until when a spark S generated by the discharge becomes the maximum.

Description

  The present invention relates to an ignition device that repeats a combustion cycle in which an internal combustion engine is ignited by discharge of a spark plug.

  Conventionally, an ignition device that generates a spark discharge in an internal combustion engine by applying a voltage from an ignition coil to an ignition plug for each combustion cycle has been widely used. As a kind of such an igniter, Patent Document 1 discloses an apparatus configured to efficiently input discharge energy necessary for spark discharge by changing a discharge time according to a combustion pressure (in-cylinder pressure) in an internal combustion engine. It is disclosed.

JP 2001-153016 A

  In recent years, the flow of the air-fuel mixture in an internal combustion engine tends to increase as the output of the internal combustion engine increases and fuel consumption decreases. Here, the spark generated by the discharge is easily expanded by the flow of the air-fuel mixture, and once the expansion amount exceeds the limit, the spark is once cut and then appears in a reduced form by the second discharge. Therefore, in the method of Patent Document 1 in which the discharge time is changed according to the combustion pressure, even if the discharge energy is increased in a state where the spark is reduced by the second discharge, the combustion rate cannot be sufficiently increased, and the energy efficiency is improved. There was room for improvement.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide an ignition device that achieves ignition with excellent energy efficiency.

  The invention according to claim 1 is an ignition device that repeats a combustion cycle in which an internal combustion engine is ignited by discharge of the ignition plug, and the voltage is applied to the ignition plug by applying a voltage to the ignition plug at each combustion cycle. The main ignition coil that generates a spark discharge and the discharge current is increased by applying a voltage to the spark plug after waiting for the delay time to elapse from the start of the discharge by the main ignition coil at each combustion cycle. A sub-ignition coil and delay time setting means for setting a delay time close to the time from the start of discharge until the spark generated by the discharge is maximized.

  According to the present invention, at each combustion cycle, after the delay time has elapsed from the start of the discharge due to the voltage application from the main ignition coil to the spark plug, the discharge current is applied by the voltage application from the sub ignition coil to the spark plug. Is increased. At this time, since the delay time is set close to the time from the start of the discharge until the spark generated by the discharge becomes the maximum, the increase in the discharge energy given to the air-fuel mixture due to the increase of the discharge current causes the spark to It will be realized in the state of approaching the maximum. Here, according to the spark that is maximized when the expansion amount due to the flow of the air-fuel mixture reaches the limit, the heating area of the air-fuel mixture due to the initial flame is also maximized, so that the discharge energy increases in a state close to the maximum spark. According to this, the combustion rate of the air-fuel mixture can be maximized. Therefore, it is possible to achieve ignition with excellent energy efficiency.

  The invention according to claim 2 includes combustion time acquisition means for acquiring the combustion time of the air-fuel mixture in the internal combustion engine for each combustion cycle, and the delay setting means is provided by the combustion time acquisition means in the current combustion cycle. Based on the current combustion time, which is the acquired combustion time, a delay time in the next combustion cycle is set. As in the present invention, the combustion time acquired for each combustion cycle regarding the combustion of the air-fuel mixture in the internal combustion engine becomes shorter as the spark increases when the discharge energy increases due to the increase in the discharge current. Therefore, based on the current combustion time, which is the combustion time acquired in the current combustion cycle, the delay time as close as possible to the time from the start of discharge to the maximum spark is set in a predictive manner. it can. As a result, the discharge energy increases in a state close to the maximum spark and the combustion speed of the air-fuel mixture can be maximized, so that ignition with excellent energy efficiency can be achieved.

  According to the third aspect of the present invention, the delay time setting means performs the next combustion when the current combustion time is shorter than the previous combustion time that is the combustion time acquired by the combustion time acquisition means in the previous combustion cycle. While the delay time in the cycle is extended, the delay time in the next combustion cycle is shortened when the current combustion time is longer than the previous combustion time. As in the present invention, while the current combustion time is shorter than the previous combustion time, which is the combustion time acquired in the previous combustion cycle, by extending the delay time in the next combustion cycle, When the discharge energy increases due to the increase, the amount of expansion of the spark increases. On the other hand, if the current combustion time is longer than the previous combustion time, the spark is reduced beyond the limit when the discharge energy rises due to the increase in the discharge current, so the delay time is shortened in the next combustion cycle. Thus, at the time of the rise, the amount of expansion of the spark returns to below the limit. According to these, since the delay time can be as close as possible to the time from the start of discharge to the maximum spark, the discharge energy is increased in a state close to the maximum spark and the combustion speed of the mixture is increased. The effect of maximizing is assured. Therefore, ignition with excellent energy efficiency can be achieved.

  According to the invention described in claim 4, the combustion time acquisition means is the total heat generation during the period from the start of combustion to the end of combustion of the air-fuel mixture in the current combustion cycle. An initial period that is a predetermined proportion of the quantity is acquired as the combustion time. As in the present invention, of the period from the start of combustion of the air-fuel mixture to the end of combustion in the current combustion cycle, the length of the initial period in which the heat generation amount from the start of combustion is a predetermined ratio of the total heat generation amount during the period This greatly depends on the burning speed of the initial flame according to the amount of spark expansion. Therefore, based on the current combustion time which is such an initial period, the delay time as close as possible to the time from the start of discharge to the maximum spark can be set appropriately. As a result, the discharge energy increases in a state close to the maximum spark and the combustion speed of the air-fuel mixture can be maximized, so that ignition with excellent energy efficiency can be achieved.

  According to the invention described in claim 5, the combustion time acquisition means detects the combustion pressure in the internal combustion engine, and the combustion time for each combustion cycle based on the combustion pressure detected by the combustion pressure sensor. A combustion time calculating circuit for calculating As in the present invention, the combustion pressure detected by the combustion pressure sensor in the internal combustion engine is a physical quantity representing the combustion state of the air-fuel mixture, so the combustion time calculated for each combustion cycle based on the combustion pressure is The value correctly reflects the combustion rate. Therefore, based on the current combustion time which is such a combustion time, the delay time as close as possible to the time from the start of discharge to the maximum spark can be set appropriately. As a result, the discharge energy increases in a state close to the maximum spark and the combustion speed of the air-fuel mixture can be maximized, so that ignition with excellent energy efficiency can be achieved.

  According to the invention described in claim 6, the delay time setting means predicts in advance based on the size of the spark gap in the spark plug and the flow rate of the air-fuel mixture in the internal combustion engine as the time from the start of discharge to the maximum spark. Set the delay time to In the present invention, the time from the start of discharge to the maximum spark depends on the size of the spark gap in the spark plug and the flow rate of the air-fuel mixture in the internal combustion engine. Therefore, the delay time set in advance based on the spark gap size and the air-fuel mixture flow rate can be as close as possible to the actual time from the start of discharge to the maximum spark. Therefore, since the discharge energy can be increased in the state close to the maximum spark and the combustion speed of the air-fuel mixture can be maximized, ignition with excellent energy efficiency can be achieved.

It is a block diagram which shows the ignition device by 1st embodiment of this invention. It is a time chart for demonstrating the voltage application control of the ignition device by 1st embodiment of this invention. It is a characteristic view for demonstrating voltage application control of the ignition device by 1st embodiment of this invention. It is a schematic diagram for demonstrating voltage application control of the ignition device by 1st embodiment of this invention. It is a flowchart for demonstrating voltage application control of the ignition device by 1st embodiment of this invention. It is the schematic diagram (a) and table | surface (b) for showing a specific example about the voltage application control of the ignition device by 1st embodiment of this invention. It is a characteristic view for demonstrating the effect of the voltage application control of the ignition device by 1st embodiment of this invention. It is a flowchart for demonstrating the voltage application control of the ignition device by 2nd embodiment of this invention. It is a time chart for demonstrating the voltage application control of the ignition device by other embodiment of this invention.

  Hereinafter, a plurality of embodiments of the present invention will be described with reference to the drawings. In addition, the overlapping description may be abbreviate | omitted by attaching | subjecting the same code | symbol to the corresponding component in each embodiment. When only a part of the configuration is described in each embodiment, the configuration of the other embodiment described above can be applied to the other part of the configuration. In addition, not only combinations of configurations explicitly described in the description of each embodiment, but also the configurations of a plurality of embodiments can be partially combined even if they are not explicitly specified unless there is a problem with the combination. .

(First embodiment)
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an ignition device 1 according to an embodiment of the present invention. The ignition device 1 is applied to, for example, an internal combustion engine 2 mounted on an automobile, a two-wheeled vehicle, a cogeneration system, a gas pressure pump, or the like. The ignition device 1 controls the input of discharge energy required for discharge in order to repeat the combustion cycle in which the internal combustion engine 2 is ignited by discharge. The ignition device 1 includes a spark plug 10, a main ignition coil 20, a sub ignition coil 30, a combustion pressure sensor 40, and an ignition control circuit 50.

  The spark plug 10 is, for example, a nickel plug, a platinum plug, an iridium plug, or the like, and has a center electrode 10 a and a ground electrode 10 b that are exposed in the combustion chamber 2 b in the cylinder 2 a of the internal combustion engine 2. The spark plug 10 ignites the unburned air-fuel mixture introduced into the combustion chamber 2b by generating a spark discharge in the spark gap G formed between the electrodes 10a and 10b. As a result, the flame propagates to the air-fuel mixture in the combustion chamber 2b, and combustion of the air-fuel mixture in one combustion cycle is realized. The spark plug 10 may be applied to the internal combustion engine 2 as a component of the ignition device 1 or may be applied to the internal combustion engine 2 as a product different from the ignition device 1. May be.

  The main ignition coil 20 includes a primary coil 22, a secondary coil 24, and an igniter 26. For the primary coil 22 connected to the igniter 26, the secondary coil 24 is connected to the spark plug 10 via a diode D that rectifies a high voltage. In each combustion cycle, the igniter 26 induces a high voltage to the secondary coil 24 by cutting off the energization current to the primary coil 22 in accordance with the input signal from the ignition control circuit 50. As a result, a high voltage is applied from the secondary coil 24 to the spark plug 10, so that a discharge occurs in the spark gap G.

  The sub ignition coil 30 includes a primary coil 32, a secondary coil 34, and an igniter 36 that are connected to the main ignition coil 20. However, in each combustion cycle, the igniter 36 of the auxiliary ignition coil 30 cuts off the energization current to the primary coil 32 during the occurrence of discharge by the main ignition coil 20 in accordance with the input signal from the ignition control circuit 50, thereby increasing the high voltage. Is induced in the secondary coil 34. As a result, when a high voltage is applied from the secondary coil 34 to the spark plug 10, the discharge current flowing through the spark gap G increases.

  The combustion pressure sensor 40 is, for example, a capacitance type, a piezoelectric element type or the like, and detects a combustion pressure (in-cylinder pressure) P of the air-fuel mixture in the combustion chamber 2b in the cylinder 2a of the internal combustion engine 2. The combustion pressure sensor 40 outputs a signal representing the detected combustion pressure P. The combustion pressure sensor 40 is disposed separately from the spark plug 10 in FIG. 1, but may be built in the spark plug 10.

  The ignition control circuit 50 is an electronic circuit mainly composed of, for example, a microcomputer and having a memory 52, and is connected to the igniters 26 and 36 of the ignition coils 20 and 30 and the combustion pressure sensor 40. The ignition control circuit 50 generates an ignition control signal for controlling energization of the primary coils 22 and 32 of the ignition coils 20 and 30 based on the combustion pressure P represented by the input signal from the combustion pressure sensor 40. , 30 igniters 26 and 36. As a result, in each ignition coil 20, 30, a high voltage is applied from the secondary coil 24, 34 to the spark plug 10 by cutting off the energization to the primary coil 22, 32 according to the ignition control signal input to the igniters 26, 36. When applied, a spark discharge will occur. Therefore, in the following, the ignition control signal is output from the ignition control circuit 50 to the igniters 26 and 36 of the ignition coils 20 and 30, and from the secondary coils 24 and 34 of the ignition coils 20 and 30 to the ignition plug 10. This will be described in detail as controlling voltage application.

  In the voltage application control of the first embodiment, the timing and duration of voltage application from the ignition coils 20 and 30 to the ignition plug 10 are controlled as shown in FIG. 2 for each combustion cycle. Specifically, first, discharge is started by applying a voltage from the main ignition coil 20 to the spark plug 10, and after waiting for the delay time TD to elapse from the start time t0, the sub ignition coil 30 transfers to the spark plug 10. Is applied during the discharge. That is, while the voltage application from the main ignition coil 20 to the ignition plug 10 is continued from the discharge start time t0 for the main ignition time TM longer than the delay time TD, the voltage application from the sub ignition coil 30 to the ignition plug 10 is performed. It starts from the time t1 when the delay time TD elapses. As a result, in the auxiliary ignition time TA in which the voltage application from the auxiliary ignition coil 30 to the ignition plug 10 is continued after the elapse time t1 of the delay time TD in the main ignition time TM, The sum of the secondary currents Im and Ia flows through the spark gap G as the discharge current Id. Therefore, the discharge current Id in the main ignition time TM increases at the auxiliary ignition time TA rather than within the delay time TD, thereby increasing the discharge energy given to the air-fuel mixture in the combustion chamber 2b. Become.

  Here, in the voltage application control of the first embodiment, a time point at which voltage application from the main ignition coil 20 to the spark plug 10 is started is set as a discharge start time point t0. Further, in the voltage application control of the first embodiment, each ignition is performed so that the maximum peaks (for example, Im = 50 mA, Ia = 80 mA) of the secondary currents Im and Ia appear only once during the times TM and TA, respectively. Voltage application from the coils 20 and 30 to the spark plug 10 is controlled. Furthermore, in the voltage application control of the first embodiment, the ignition times TM and TA are defined in advance according to the specifications of the internal combustion engine 2, the specifications of the spark plug 10, and the like. About 5 ms, and the auxiliary ignition time TA is specified to be about 0.2 to 0.6 ms. Furthermore, in the voltage application control of the first embodiment, the delay time TD for waiting for the increase of the discharge current Id by the auxiliary ignition coil 30 is based on the combustion time TC of the air-fuel mixture in the combustion chamber 2b for each combustion cycle. Is set. Therefore, in the following, the correlation principle between the combustion time TC and the delay time TD will be described first.

  As shown in FIG. 3, in the voltage application control of the first embodiment, the heat generation amount Q from the start of combustion in the period from the start of combustion of the air-fuel mixture to the end of combustion in each combustion cycle is the total amount during the period. An initial period TE that is a predetermined ratio R of the heat generation amount is acquired as a combustion time TC. Acquisition of the initial period TE as the combustion time TC is performed as follows for each combustion cycle. First, based on the combustion pressure P represented by the input signal from the combustion pressure sensor 40, the heat generation rate (see FIG. 3A) in the combustion chamber 2b is sequentially calculated, and the calculated heat generation rate is burned. The heat generation amount Q is derived by integrating with the time from the start. Then, assuming that the heat generation amount Q in the period from the start of combustion to the end of combustion is the total heat generation amount, the combustion mass ratio of the heat generation amount Q to the total heat generation amount (see FIG. The initial period TE is determined as the combustion time TC. The ratio R defining the initial period TE as the combustion time TC is a ratio of a period in which the length of the initial period TE is greatly influenced by the combustion speed of the air-fuel mixture in the combustion chamber 2b, for example, about 10%. In advance.

  Regarding the combustion time TC (initial period TE) acquired in this way, as shown in FIG. 4, the spark S generated by the discharge in the spark gap G is mixed when the discharge energy increases due to the increase of the discharge current Id. The longer you expand, the shorter it gets. Thus, the shortening of the combustion time TC means that the area of the initial flame is increased with respect to the discharged discharge energy, and the combustion speed of the air-fuel mixture in the combustion chamber 2b is efficiently increased. To do. Therefore, in the voltage application control of the first embodiment, the delay time TD for waiting for the increase in the discharge current Id is changed from the discharge start time t0 to the maximum spark time TMAX until the spark S becomes the maximum due to the limit of the expansion amount. Predictively set based on the combustion time TC so as to approach. Hereinafter, a characteristic method for setting the delay time TD close to the maximum spark time TMAX will be described.

  As shown in FIG. 4, the spark S tends to expand as time elapses from the discharge start time t0, but when the amount of expansion exceeds the limit, that is, the elapsed time from the discharge start time t0 is the maximum spark time TMAX. If it exceeds, it will appear once in a reduced form due to re-discharge. Here, as the spark S expands at the time t1 when the delay time TD substantially coincides with the increase in the discharge current Id, the heating area of the air-fuel mixture due to the initial flame increases and the combustion speed increases. As described above, the combustion time TC is shortened. Therefore, in the voltage application control of the first embodiment, first, the previous combustion time TCl, which is the combustion time TC of the previous combustion cycle, is compared with the current combustion time TCp, which is the combustion time TC of the current combustion cycle. As a result, if the current combustion time TCp is shorter than the previous combustion time TCl, the amount of expansion of the spark S has not reached its limit at the time t1 when the delay time TD has elapsed, and the delay time TD is extended in the next combustion cycle. Thus, the amount of expansion of the spark S at the time point t1 is increased. On the other hand, if the current combustion time TCp is longer than the previous combustion time TCl, the spark S is reduced beyond the limit at the time t1 when the delay time TD has elapsed, and the delay time TD is shortened in the next combustion cycle. The amount of expansion of the spark S at the time point t1 is returned to the limit or less. By performing the extension or shortening process in this manner, the delay time TD approaches the maximum spark time TMAX at which the spark S is maximum from the discharge start time t0 as much as possible and reliably.

  From the above, in the voltage application control of the first embodiment, the ignition control circuit 50 executes the control flow as shown in FIG. 5 so as to realize the above characteristic method of setting the delay time TD close to the maximum spark time TMAX. To do. This control flow is started in response to an engine switch ON command for instructing start of the internal combustion engine 2 and then ended in response to an engine switch OFF command for instructing stop of the internal combustion engine 2.

  In S101 of the control flow, the combustion cycle number n and the delay time TD are initially set to 1 and TD0, respectively. Here, in particular, as the initial value TD0 of the delay time TD, for example, a value selected in advance as shown in FIG. 6 is adopted. Specifically, in order to set the initial value TD0, first, the amount of expansion of the spark S according to the elapsed time from the discharge start time t0 is set to the size δ of the spark gap G and the mixture in the combustion chamber 2b. Calculation is made based on the flow velocity Fm. From the calculation result, a range (a range indicated by a gray scale in FIG. 6) effective for increasing the discharge energy due to the increase of the discharge current Id when the expansion amount of the spark S is less than the maximum is derived. Then, a suitable range (a range indicated by a white arrow in FIG. 6) for the delay time TD is predicted from the derived effective range, and a value within the suitable range is selected as the initial value TD0. FIG. 6 shows a preferable range for selecting the initial value TD0 from 0.1 to 0 from the effective range in which the amount of expansion of the spark S is 2 to 10 mm when the size δ of the spark gap G is 1 mm. The example predicted for 4 ms is shown.

  In S102 of FIG. 5 executed after such initial setting, the first combustion cycle is started so that the auxiliary ignition time TA is started after waiting for the time TD0 currently set as the delay time TD from the start of the main ignition time TM. Execute. At this time, in the first embodiment, the heat generation amount Q based on the combustion pressure P detected by the combustion pressure sensor 40 is sequentially derived.

  In subsequent S103, an initial period TE, which is the combustion time TC, is calculated based on the heat generation amount Q derived during the first combustion cycle, and the value stored in the memory 52 as the previous combustion time TCl used in S108. Is updated by the calculation period TE. In subsequent S104, the delay time TD is extended by a time ΔT from the current value TD0. Here, the time ΔT is defined in advance to a length that is sufficiently shorter than the preferable range of the delay time TD predicted as described above (see FIG. 6) and that the change of the initial period TE can appear.

  Thereafter, in S105, the combustion cycle number n is incremented, and in S106, from the start of the main ignition time TM, the auxiliary ignition time TA is started after waiting for the currently set delay time TD. Run the combustion cycle. Here, in S106, the heat generation amount Q based on the combustion pressure P is sequentially derived in the same manner as in S102.

  In the subsequent S107, the initial period TE, which is the combustion time TC, is calculated based on the heat generation amount Q derived during the nth combustion cycle, and the value stored in the memory 52 as the current combustion time TCp used in S108. Is updated by the calculation period TE. In S108, the previous combustion time TCl and the current combustion time TCp currently stored in the memory 52 are compared to determine whether the current combustion time TCp is shorter than the previous combustion time TCl.

  If an affirmative determination is made in S108, that is, if the current combustion time TCp is shorter than the previous combustion time TCl, S109 and S110 are sequentially executed, and the process returns to S105. Here, in S109, in accordance with S104, the delay time TD is extended by a time ΔT from the current value. In the subsequent S110, the previous combustion time TCl stored in the memory 52 is updated by the current combustion time TCp currently stored in the memory 52.

  On the other hand, if a negative determination is made in S108, that is, if the current combustion time TCp is longer than the previous combustion time TCl, S111 is executed and the process returns to S105. Here, in S111, contrary to S104 and S109, the delay time TD is shortened by the time ΔT from the current value.

  Thus, according to the control flow for realizing the voltage application control of the first embodiment, when the current combustion time TCp is shorter than the previous combustion time TCl, the delay time TD is extended in the next combustion cycle, The amount of expansion of the spark S when the discharge current Id increases is increased. On the other hand, when the current combustion time TCp is longer than the previous combustion time TCl, the amount of expansion of the spark S when the discharge current Id increases returns to below the limit by reducing the delay time TD in the next combustion cycle. It becomes. According to these, since the delay time TD can be reliably brought close to the time TMAX from the discharge start time t0 until the spark S becomes the maximum, the discharge energy is increased in a state where the spark S and its heating area are close to the maximum. There is a certain effect on maximizing the burning rate.

  Here, as a specific example, the internal combustion engine 2 that realizes the configuration of the above-described example of FIG. 6 is visualized, and the flame area 1.5 ms after the discharge start time t0 is expressed at two engine speeds (1000 rpm and 3000 rpm). The examination results are shown in FIG. In FIG. 7, the flame area (numerator) when the discharge current Id is increased by the auxiliary ignition coil 30 after the delay time TD from the discharge start time t0, and the case where the increase of the discharge current Id is not executed. The ratio with the flame area (denominator) is shown as the flame area increase rate. As is apparent from the results of FIG. 7, in the preferable range of 0.1 to 0.4 ms as the delay time TD illustrated in FIG. 6, the flame area increase rate increases, that is, the burning rate of the initial period TE due to the initial flame. It can be seen that can be increased. Therefore, according to such 1st embodiment, ignition excellent in energy efficiency can be achieved.

  The combustion times TCp and TCl used for setting the delay time TD are the initial period TE that depends on the combustion speed in the period from the start of combustion of the mixture to the end of combustion, and the combustion state of the mixture The initial period of acquisition TE is based on the combustion pressure P representing Therefore, based on the combustion times TCp and TCl, which are the initial periods TE, the delay time TD that is as close as possible to the time from the discharge start time t0 to the maximum spark S is set appropriately. As a result, it is possible to greatly contribute to the achievement of ignition with excellent energy efficiency.

  In the first embodiment described above, the ignition control circuit 50 that executes S101 to S111 of the control flow corresponds to the “delay time setting means” recited in the claims, and S103, S104, and S106 of the control flow. , S107, the ignition control circuit 50 corresponds to “combustion time acquisition means” and “combustion time calculation circuit” recited in the claims.

(Second embodiment)
As shown in FIG. 8, the second embodiment of the present invention is a modification of the first embodiment. As shown in FIG. 8, S103, S104, and S107 to S111 are not executed in the control flow for realizing the voltage application control of the second embodiment. Thereby, in S106 in which the n-th combustion cycle is executed, the same initial value TD0 as S101 in the preferred range (see FIG. 6) of the delay time TD predicted in advance as in the first embodiment is delayed. Used as time TD. Accordingly, in the second embodiment, the detection result of the combustion pressure P by the combustion pressure sensor 40 is not used for setting the delay time TD, and therefore the combustion pressure sensor 40 may be omitted as a component of the ignition device 1. .

  As described above, according to the control flow for realizing the voltage application control of the second embodiment, a value predicted based on the size δ of the spark gap G and the flow velocity Fm of the air-fuel mixture is used as the delay time TD. Will be. Here, since the size δ of the spark gap G and the flow velocity Fm of the air-fuel mixture are physical quantities that correlate with the time TMAX from the discharge start time t0 until the spark S reaches the maximum, the prediction is based on the size δ and the flow velocity Fm. Accordingly, the delay time TD can be as close as possible to the actual time TMAX. Thereby, since the discharge energy can be increased and the combustion speed can be increased to the maximum with the spark S close to the maximum, ignition with excellent energy efficiency can be achieved.

(Other embodiments)
Although a plurality of embodiments of the present invention have been described above, the present invention is not construed as being limited to these embodiments, and various embodiments and combinations can be made without departing from the scope of the present invention. Can be applied.

  Specifically, a sensor that detects a physical quantity other than the combustion pressure P as a combustion state of the air-fuel mixture in the combustion chamber 2b is used instead of the combustion pressure sensor 40, and the combustion time TC (initial period) is based on the detected physical quantity. TE) may be calculated by the ignition control circuit 50. Further, as shown in FIG. 9, the voltage application from the secondary ignition coil 30 to the spark plug 10 is controlled so that the maximum peak of the secondary current Ia appears a plurality of times during the auxiliary ignition time TA. It is good.

1 ignition device, 2 internal combustion engine, 2a cylinder, 2b combustion chamber, 10 spark plug, 10a center electrode, 10b ground electrode, 20 main ignition coil, 22, 32 primary coil, 24, 34 secondary coil, 26, 36 igniter, 30 sub-ignition coil, 40 combustion pressure sensor, 50 ignition control circuit (delay time setting means / combustion time acquisition means / combustion time calculation circuit), 52 memory, Fm flow velocity, G spark gap, Ia, Im secondary current, Id discharge Current, P Combustion pressure, Q Heat generation, R ratio, S Spark, TC combustion time, TCl Last combustion time, TCp Current combustion time, TD delay time, TE initial period, TMAX maximum spark time, δ Spark gap size

Claims (6)

An ignition device that repeats a combustion cycle for igniting an internal combustion engine by discharging a spark plug,
A main ignition coil that generates a spark discharge in the spark plug by applying a voltage to the spark plug at each combustion cycle;
A sub-ignition coil that increases a discharge current by applying a voltage to the spark plug after waiting for a delay time to elapse from the start of discharge by the main ignition coil for each combustion cycle;
A delay time setting means for setting the delay time close to the time from the start of the discharge until the spark generated by the discharge is maximized,
An ignition device comprising: Combustion time acquisition means for acquiring the combustion time of the air-fuel mixture in the internal combustion engine for each combustion cycle,
The delay setting means sets the delay time in the next combustion cycle based on the current combustion time that is the combustion time acquired by the combustion time acquisition means in the current combustion cycle. The ignition device according to claim 1. The delay time setting means includes
When the current combustion time is shorter than the previous combustion time, which is the combustion time acquired by the combustion time acquisition means in the previous combustion cycle, the delay time in the next combustion cycle is extended,
The ignition device according to claim 2, wherein when the current combustion time is longer than the previous combustion time, the delay time in the next combustion cycle is shortened.   The combustion time acquisition means is configured such that, in the period from the start of combustion of the air-fuel mixture to the end of combustion in the current combustion cycle, the heat generation amount from the start of combustion becomes a predetermined ratio of the total heat generation amount during the period. The ignition apparatus according to claim 2, wherein an initial period is acquired as the combustion time. The combustion time acquisition means includes
A combustion pressure sensor for detecting a combustion pressure in the internal combustion engine;
A combustion time calculation circuit for calculating the combustion time for each combustion cycle based on the combustion pressure detected by the combustion pressure sensor;
It has, The ignition device as described in any one of Claims 2-4 characterized by the above-mentioned.   The delay time setting means is a time estimated in advance based on the size of the spark gap in the spark plug and the flow rate of the air-fuel mixture in the internal combustion engine as the time from the start of discharge to the maximum spark. The ignition device according to claim 1, wherein a delay time is set.

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