JP2000291519A - Ignition device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an ignition characteristic which responds to an operation state of an internal combustion engine. SOLUTION: At starting, before completion of warming-up (S12) or in time of stratified charge combustion (S15), the current-carrying time of an ignition coil capable of generating large ignition energy is set to a longish base current carrying time to have a characteristic that a secondary voltage quickly rises and a discharge time is long. Then, the base current-carrying time is reduced for correction according to reduction of an EGR rate or increase of a target equivalence ratio (S11, S14), the current-carrying time is increased for correction at misfiring (S20), and the current-carrying time is reduced for correction at the time of knocking (S22).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ignition device for an internal combustion engine, and more particularly, to a technology for obtaining an ignition characteristic according to an operation state of the engine.

[0002]

2. Description of the Related Art The characteristics of an ignition coil in an ignition device for an internal combustion engine are required to have a fast rising speed of a secondary voltage in order to obtain good ignition characteristics against smoldering of an ignition plug, and to be stable after ignition. In order to obtain improved flammability, a characteristic requiring a long discharge time is required.

[0003] In particular, in order to improve fuel efficiency and exhaust gas purifying performance, in recent years, in order to improve fuel efficiency and exhaust gas purification performance, leaning is promoted as homogeneous lean combustion or stratified combustion, or a large amount of EGR is performed by homogeneous stoichiometric combustion. However, in order to increase the combustion stability limit, a longer discharge time is required, but on the other hand, the gap between the spark plug electrodes is increased for the above purpose,
In the case of a gasoline in-cylinder combustion method in which a large amount of carbon is generated, there is also a demand for increasing the rising speed of the secondary voltage of the ignition coil in order to prevent starting failure due to smoldering of the ignition plug and fluctuation in rotation during idling.

As described above, in order to simultaneously secure the characteristics that the secondary voltage rises fast and the discharge time is long, the turn ratio between the primary side and the secondary side of the ignition coil must be reduced and It is necessary to increase the inductance of the primary side of the ignition coil so that large ignition energy is generated.

[0005]

However, by using the ignition coil having the increased ignition energy as described above, the ignition coil is controlled with a constant energizing time irrespective of the operating state as in the case of ordinary ignition control, so that the maximum value is always obtained. When the ignition energy is generated, not only does the power consumption increase and the fuel efficiency deteriorates, but also the heat generation of the ignition coil and the wear of the spark plug electrode pose a problem.

Further, the current supply time of the ignition coil is variably controlled in accordance with the required discharge voltage determined by the ignition timing and the spark plug voltage (JP-A-10-471263).
Japanese Patent Application Laid-Open No. HEI 6-129333, or a device in which control is variably performed according to the presence or absence of misfire (see Japanese Patent Application Laid-Open No. 6-129333). In control in which ignition energy is required and the energizing time is increased after misfire detection, misfire cannot be suppressed beforehand.

The present invention has been made in view of such a conventional problem, and an internal combustion engine which solves the above problem by supplying a minimum necessary ignition energy according to the operating state of the engine. It is an object of the present invention to provide an ignition device.

[0008]

Therefore, according to the present invention, as shown in FIG. 1, an operating state detecting means for detecting an operating state of an engine and an energizing time of an ignition coil are determined by the operating state detecting means. And a power-on time control means for controlling the secondary voltage rise rate and the discharge time for each operating state detected by the means in accordance with a request.

According to the first aspect of the present invention, the primary current at the time of energization interruption increases as the energization time of the ignition coil increases, and accordingly, the rising speed of the secondary voltage, the discharge time, and the power consumption increase. Increase.

Therefore, in order to satisfy the requirements of the secondary voltage rise speed and the discharge time for each engine operating state, the power supply time is controlled so as to generate the minimum necessary ignition energy, thereby reducing power consumption as much as possible. Thus, it is possible to maintain good ignition performance in all operating states while maintaining good durability of the ignition coil and the spark plug.

In the invention according to a second aspect, the energization time control means controls the basic energization time set at a large value at the time of starting, before completion of warm-up, and at the time of stratified combustion. The basic energization time is reduced and controlled according to the EGR rate at the time and according to the equivalent ratio at the time of homogeneous lean combustion.

According to the second aspect of the present invention, the ignition coil is energized for a relatively large basic energizing time at the time of starting or before the completion of warm-up, so that the rising speed of the secondary voltage is controlled sufficiently fast. Good smoldering resistance is ensured and good ignition performance is obtained.

In addition, during stratified combustion, for a rich air-fuel mixture around the ignition plug, a characteristic that the secondary voltage rises quickly is required so as to obtain good ignition performance against smoldering. For the lean mixture on the outside, a characteristic that a long discharge time is required to maintain a stable combustion state, but by controlling the energization time to the basic energization time to, both these characteristics are satisfied simultaneously. It is.

Further, when performing EGR in homogeneous stoichiometric combustion, it is necessary to increase the discharge time of the ignition coil in order to ensure stable combustion, but as shown in FIG. 2, as the EGR rate decreases, Since the stable limit discharge time is reduced, the basic energization time is shortened and corrected in accordance with the EGR rate, so that necessary and sufficient ignition energy is generated and good ignition performance can be obtained.

In homogeneous lean combustion, it is necessary to increase the discharge time of the ignition coil in order to ensure stable combustion. As shown in FIG. 3, as the target equivalent ratio increases, the stable limit discharge time increases. Therefore, by shortening and correcting the basic energizing time according to the target equivalent ratio, a necessary and sufficient ignition energy is generated, and good ignition performance can be obtained.

Further, the invention according to claim 3 is characterized in that the ignition control means performs control by increasing and correcting the energization time when a misfire occurs.

According to the third aspect of the present invention, there is a need to increase the rising speed of the secondary voltage for misfire due to smoldering, and to require a longer discharge time for misfire due to excessive lean. But in each case,
By increasing the ignition energy by increasing the energization time and increasing the ignition energy, it is possible to satisfy these requirements and quickly prevent misfire.

Further, the invention according to claim 4 is characterized in that the ignition control means performs control by reducing and correcting the energization time when knocking occurs.

According to the fourth aspect of the present invention, that is, when knocking occurs, the tip of the spark plug, which becomes high in temperature, becomes a hot surface ignition source that is induced by the continuous occurrence of knocking and causes preignition. By shortening and correcting the energization time to shorten the discharge time, the temperature of the tip end of the spark plug is reduced, and preignition can be avoided.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an ignition device for an internal combustion engine according to the present invention will be described below. FIG. 4 shows a system configuration of an internal combustion engine provided with an ignition device according to one embodiment of the present invention. In the figure, an accelerator opening sensor 1 detects the amount of depression of an accelerator pedal depressed by a driver.

The crank angle sensor 2 generates a position signal for each unit crank angle and a reference signal for each cylinder stroke phase difference, and measures the number of the position signals generated per unit time, or generates the reference signal. By measuring the period, the engine rotation speed Ne can be detected.

The air flow meter 3 detects the amount of intake air to the engine 4 per unit time. The water temperature sensor 5 detects the temperature of the cooling water of the engine 4. In the cylinder part of the engine 4,
A fuel injection valve 7 for directly injecting fuel into the combustion chamber 6 and an ignition plug 8 for performing spark ignition in the combustion chamber 6 are provided. Also, 1
By reducing the turns ratio between the secondary coil and the secondary coil and increasing the inductance of the primary coil,
When the energization time is maximized, an ignition coil 9 is provided which has a characteristic that the rising speed of the secondary voltage is extremely fast and the discharge time is extremely long. -It is configured to be energized and driven via off.

In the low / medium load range, fuel is injected into the combustion chamber 6 in the compression stroke to form a flammable mixture around the spark plug 8 in the combustion chamber 6 to perform stratified combustion. In the high load region, fuel is injected into the combustion chamber 6 during the intake stroke to form a mixture having a substantially uniform mixture ratio over the entire cylinder, thereby enabling homogeneous combustion.

A throttle valve 12 is interposed in the intake passage 11 of the engine 4, and a throttle valve control device 13 capable of electronically controlling the opening of the throttle valve 12 and an opening of the throttle valve 12 are detected. A throttle sensor 14 is provided.

On the other hand, an exhaust passage 15 of the engine 4 has an air-fuel ratio sensor 16 for detecting an air-fuel ratio from a specific component such as oxygen in the exhaust gas, an upstream exhaust purification catalyst 17, and a downstream exhaust purification catalyst 1.
8. A muffler 19 is provided. In addition, a knock sensor 20 for detecting a knocking occurrence state is provided.

The various sensors and ignition switch ING SW, starter switch ST SW, battery voltage Vb
And the like, are input to the control unit 21. The control unit 21 opens the throttle valve 9 via the throttle valve control device 13 in accordance with the operating state detected based on the signals from the sensors. The fuel injection valve 7 is driven to control the fuel injection amount, the ignition timing is set, and the ignition plug 8 is ignited at the ignition timing.

Further, an EGR passage 22 for recirculating a part of the exhaust gas from the exhaust passage 15 of the engine to the intake passage 11 is provided.
EG comprising an EGR valve 23 interposed in the R passage 22
An R device is provided. The EGR is performed based on a control signal from the control unit 21. During homogeneous stoichiometric combustion by feedback control at a stoichiometric air-fuel ratio, the EGR control is performed at a large EGR rate. EGR control is also performed during stratified combustion, but is prohibited in homogeneous lean combustion that is switched from stratified combustion.

FIG. 5 shows a functional configuration of the embodiment.
The target torque setting unit sets the target torque of the engine by searching a map or the like based on the accelerator opening and the engine speed.

The target EGR amount and the target fresh air amount calculation unit calculates the target EGR amount and the target fresh air amount based on the calculated target torque and engine speed. The EGR valve opening and throttle opening calculating section calculates the calculated target E
A target EGR rate is calculated based on the GR amount and the target fresh air amount, and an EGR valve opening and a throttle opening corresponding to the target EGR rate are calculated.

The target equivalence ratio calculation section calculates the target equivalence ratio based on the engine speed, target torque, water temperature and the like. More specifically, a determination is made as to switching between the combustion states [stratified combustion and homogeneous combustion (homogeneous lean combustion, homogeneous stoichiometric combustion, homogeneous rich combustion)] based on each of the above parameters, and a target equivalence ratio corresponding to each combustion state is set. .

The ignition timing calculating section includes a target injection ratio, a target EGR rate, a knocking signal from a knock detecting section, and the like, in addition to the basic injection pulse width and the engine rotational speed, which are load signals of the engine from the intake air amount measuring section. Is calculated based on the ignition timing. Here, the ignition timing is calculated for the first ignition coil 9 and the second ignition coil 10 as the respective power cutoff timings.

The ignition signal output section outputs the ignition timing signal, the knocking signal, the target EGR rate signal, the target equivalence ratio signal,
Either the first ignition coil 9 or the second ignition coil 10 based on each signal of an ignition switch, a starter switch, and a battery voltage from a misfire determination result from a misfire determination unit that determines the presence or absence of a misfire due to engine rotation fluctuation or the like. One or both drives are selected, and the selected ignition coil is driven to cause ignition at the calculated ignition timing.

Hereinafter, specific ignition timing control by the above-described device will be described with reference to flowcharts shown in FIGS. In step 1, the ignition switch ING S
It is determined whether or not W is on. If it is off, this routine ends. If it is on, the routine proceeds to step 2.

In step 2, the basic energizing time to of the energizing time t of the ignition coil 9 is set. The basic energizing time to
Is set to a value that is shorter than the energization time for saturating the ignition coil 9 with the maximum ignition energy, but is sufficiently large as shown in FIG.

In step 3, the basic energization time to is corrected according to the battery voltage Vb. That is, the lower the battery voltage Vb, the longer it takes to accumulate the same ignition energy, so that a correction is made to prolong the energization time.

Next, at step 4, the starter switch
It is determined whether or not the ST SW is on. If it is on, the process proceeds to step 5 and subsequent steps. In step 5, since the correction based on the combustion state, the correction based on the presence or absence of the misfire, and the correction based on the presence or absence of the knocking are not performed at the time of starting in the arithmetic expression of the energization time described later, the combustion correction coefficient k1 and the misfire correction coefficient k
2. The knocking correction coefficient k3 is set to 1.

In step 6, the final energizing time t is calculated by the following equation. t = to × k1 × k2 × k3 In step 7, the engine speed Ne is read.

In step 8, the energization time t is converted into an energization crank angle cat based on the engine speed Ne and set. Thus, after the ignition coil 9 is energized for the energization time t, the energization is cut off at the set ignition timing and ignition is performed.

As described above, at the time of starting (at the time of cranking), the ignition coil 9 is energized for a sufficiently large basic energizing time to, as shown in FIG.
The rising speed of the next voltage is controlled to be sufficiently fast, smoldering resistance is secured, and good ignition performance and good startability are obtained.

In step 3, the starter switch ST
If it is determined that the SW is off, that is, after the start, the process proceeds to step 9 and subsequent steps. In step 9, it is determined whether the target equivalent ratio is 1 or more.

When it is determined that the target equivalence ratio is equal to or greater than 1 for homogeneous stoichiometric combustion or homogeneous rich combustion, the routine proceeds to step 10, where it is determined whether the warming-up is completed at a predetermined temperature, for example, 60 ° C. or more. If it is determined that the warm-up has been completed, the process proceeds to step 11 where the power supply time is shortened so that the combustion correction rate is less than 1 based on the EGR rate correction table. That is, as shown in FIG. 2, when a large amount of EGR is performed by homogeneous stoichiometric combustion, the discharge time of the ignition coil 9 needs to be sufficiently long to ensure stable combustion, but the EGR rate decreases. Therefore, the combustion limit coefficient k1 is correspondingly reduced to shorten and correct the energization time.

If it is determined in step 10 that the warming-up has not been completed yet, the process proceeds to step 12 in order to secure stable ignition and combustion performance during cooling, so that the energizing time is maintained at the basic energizing time to. The combustion correction coefficient k1 is set to 1.

If it is determined in step 9 that the target equivalent ratio is lean combustion which is less than 1, the routine proceeds to step 13, where it is determined whether or not homogeneous lean combustion is performed. Proceeding to 14, the power supply time is shortened and corrected so that the combustion correction rate ≤ 1 based on the target equivalence ratio correction table. That is, as shown in FIG. 3, when performing lean combustion, the ignition coil 9 is used to secure stable combustion.
It is necessary to make the discharge time sufficiently long, but as the target equivalent ratio increases (lean degree decreases), the stable limit discharge time decreases, and accordingly the combustion correction coefficient k1 is reduced to shorten the energization time. to correct.

If it is determined in step 13 that the combustion is not homogeneous lean combustion, it means that stratified combustion is being performed. In this case, the routine proceeds to step 15 where the combustion correction factor k1
Is set to 1. That is, in the stratified combustion, a characteristic in which the rising speed of the secondary voltage is high is required for a rich mixture around the spark plug so as to obtain good ignition performance against smoldering. In order to maintain a stable combustion state with respect to air, a characteristic that a discharge time is long is required. Therefore, the energizing time is maintained at the basic energizing time to so that both these characteristics are satisfied simultaneously.

After setting the energizing time in accordance with the combustion state and the EGR rate in this way, the routine proceeds to step 16, where the presence or absence of a misfire is determined based on the engine speed fluctuation level and the like. Since the misfire correction is not performed, the routine proceeds to step 17, where the misfire correction coefficient k2 is set to 1. Next, the routine proceeds to step 18, where it is determined whether knocking has occurred. Here, when knocking of a predetermined level or more occurs, for example, when the knocking occurrence state continues for a predetermined time, it is determined that knocking is present. If it is determined that knocking does not occur, no knocking correction is performed, so that the routine proceeds to step 19, where the knocking correction coefficient k3 is set to 1.

As described above, when neither misfire nor knocking has occurred, the process proceeds to step 6 and thereafter, and the energization of the ignition coil 9 is controlled for an energization time according to the combustion state and the EGR rate. If it is determined in step 16 that a misfire has occurred, the process proceeds to step 20 to set the misfire correction coefficient k2 to a value larger than 1 in order to increase and correct the energization time, and sets the knocking correction coefficient k3 to 1 in step 21. After setting
Proceeding to step 6 and thereafter, the energization of the ignition coil 9 is controlled.

That is, two types of misfires are assumed: a misfire due to smoldering and a misfire due to an excessively lean air-fuel ratio. For misfiring due to smoldering, the rising speed of the secondary voltage is made faster. There is a demand, and there is a demand for a longer discharge time for misfire due to excessive lean.In each case, by increasing the energization time and increasing the ignition energy, these demands are satisfied and the misfire occurs. To prevent promptly. In this case, at the time of stratified combustion, or at the time of combustion in a state where the EGR rate and the degree of homogeneous lean are sufficiently increased, as shown in FIG. 9C, the energizing time is increased to the maximum longer than the basic energizing time to, Thereby, the rising speed of the secondary voltage is reduced to the maximum, and the discharge time is increased to the maximum. Note that, in order to simply and more reliably prevent a misfire, when a misfire occurs, a correction for maximizing the energizing time may be performed unconditionally.

On the other hand, if it is determined in step 18 that knocking has occurred, the process proceeds to step 22 in which the knocking correction coefficient k3 is set to a value smaller than 1 in order to reduce and correct the energization time. Go to ignition coil 9
Is controlled. That is, when knocking occurs, pre-ignition is caused by continuous occurrence of knocking and causes engine damage. At this time, the hot surface ignition source causing preignition is the tip portion of the ignition plug, which becomes high in temperature, and it is effective to reduce the discharge time as a means for lowering the tip portion temperature. To shorten. As a result, as shown in FIG. 9A, a characteristic is obtained in which the rising speed of the secondary voltage is increased and the discharge time is shortened. When knocking occurs, retard control of the ignition timing that is performed separately is also used.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration and functions of the present invention.

FIG. 2 is a diagram showing a relationship between a discharge time of an ignition coil and an EGR limit.

FIG. 3 is a view showing a relationship between a discharge time of an ignition coil and a lean equivalent ratio.

FIG. 4 is a diagram showing a system configuration of an ignition device for an internal combustion engine according to one embodiment of the present invention.

FIG. 5 is a block diagram showing a functional configuration of the embodiment.

FIG. 6 is a flowchart showing an ignition control routine according to the embodiment.

FIG. 7 is a flowchart showing an ignition control routine according to the embodiment;

FIG. 8 is a diagram showing the relationship between the energizing time, the secondary voltage rising speed, and the discharging time according to the embodiment.

FIG. 9 is a diagram showing the relationship between the energization time and discharge characteristics of the ignition coil of the embodiment.

[Explanation of symbols]

 Reference Signs List 4 internal combustion engine 7 fuel injection valve 8 spark plug 9 ignition coil 21 control unit 22 EGR passage 23 EGR valve

Claims (4)

[Claims] 1. An operating state detecting means for detecting an operating state of an engine, and an energizing time of an ignition coil is determined based on a request for a secondary voltage rising speed and a discharging time for each operating state detected by the operating state detecting means. An ignition device for an internal combustion engine, comprising: an energization time control unit that performs control in accordance with the ignition timing. 2. The energization time control means controls a basic energization time set at a large value at the time of starting, before completion of warm-up, and during stratified combustion, and according to an EGR rate during homogeneous stoichiometric combustion. 2. The ignition device for an internal combustion engine according to claim 1, wherein during the homogeneous lean combustion, the basic energization time is reduced and corrected according to the equivalence ratio. 3. An ignition device for an internal combustion engine according to claim 1, wherein said ignition control means performs control by increasing and increasing an energization time when a misfire occurs. 4. The ignition device for an internal combustion engine according to claim 1, wherein said ignition control means performs control by decreasing and correcting an energization time when knocking occurs.