JPH04362276A - Ignition device for internal combustion engine - Google Patents

Abstract

PURPOSE:To provide a device which can accmulate the ignition energy sufficiently in a short time, even in the state of an internal combustion engine where the time for accumulating the ignition energy is short such as in a high revolution region. CONSTITUTION:The number of turns of a primary coil 61, thickness of an air gap A, and the magnitude of the magnetic force of a permanent magnet 65 are set so that the inductance of the primary coil 61 becomes small when the electric current (primary electric current) which flows in the prmary coil 61 of an ignition coil 6 is small, in the characteristic of the ignition coil 6. With this constitution, in a high revolution region, the ignition energy is sufficiently secured by utilizing the high speed of the starting-up of the electric current in the region where the inductance is small. Further, the ignition energy corresponding to the necessity can be supplied to a spark plug by controlling the current-carrying time of the primary coil 61 according to the state of an internal combustion engine.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ignition system for an internal combustion engine that controls ignition energy supplied to a spark plug of an internal combustion engine so that good combustion can be achieved in the engine under all operating conditions.

0002

2. Description of the Related Art Conventionally, an ignition device for an internal combustion engine is provided with a constant current circuit inside an igniter, and is controlled so that the energy (ignition energy) supplied to the spark plug is always constant.

However, the ignition energy actually required varies greatly depending on the internal combustion engine state and the vehicle running state. For example, when an internal combustion engine is under high load, the voltage required to generate a discharge between the plug gaps in the ignition coil increases, and when the internal combustion engine is cold or idle, ignition performance is poor, so ignition energy is large. is necessary. Furthermore, in recent years, in lean-burn engines that operate with the air-fuel ratio on the lean side under certain internal combustion engine conditions to promote improved fuel efficiency, it has been found that complete combustion is not achieved when the air-fuel ratio is on the lean side (lean-burn region). To obtain ignition energy greater than that required at normal air-fuel ratios is required.

Therefore, as a method for supplying large ignition energy to the ignition plug, the value of the constant current flowing through the coil that stores ignition energy is increased, or in general, the primary current-ignition energy characteristic of the ignition coil is shown in FIG.
Therefore, the inductance L of the primary coil that stores ignition energy to supply to the spark plug
One possibility is to set 1 to a large value.

[0005]

However, in the above method, the current value flowing through the ignition device (especially the igniter) increases, so the ignition device itself generates a large amount of heat. There is a possibility that a problem such as the element not operating properly may occur.

Furthermore, in the latter case, as the inductance L1 of the primary coil increases, the current (primary current) I1 flowing through the primary coil becomes more difficult to flow, and the rising time of the primary current I1 becomes slower as shown in FIG. Therefore, Figure 1
1, the horizontal axis shows the engine speed Ne and the vertical axis shows the ignition energy. If the inductance L1 is large, a large ignition energy can be obtained, but the time from the previous ignition timing to the current ignition timing is In other words, in the high rotation range where the energization time is short, the primary current I1
The problem arises that ignition energy cannot be stored because of the slow start-up.

Furthermore, when the inductance L1 is small, the primary current I1 rises quickly, so ignition energy can be accumulated even in the high rotation range where the energization time is short; however, as shown in FIG. cannot store energy.

That is, ideally, an ignition device that switches the inductance L1 in accordance with the engine speed Ne may be used, but the device becomes complicated and the manufacturing cost increases. Furthermore, as shown in Japanese Unexamined Patent Publication No. 2-37705, a permanent magnet is provided that generates magnetic flux in the opposite direction to the magnetic flux generated by energizing the primary coil of the ignition coil, and the primary coil of the permanent magnet is There are some types that secure large ignition energy by the action of magnetic flux in the opposite direction to the magnetic flux generated by energization.

However, even in such a method, since the inductance L1 is set large, the rise of the primary current I1 is slow in a high rotation range where the energization time is short, making it impossible to store sufficient ignition energy.

[0010]The present invention was made to solve the above problems, and it is an object of the present invention to secure sufficient ignition energy in a short period of time even in a region where the time for accumulating ignition energy is short, such as in a high rotation region. An object of the present invention is to provide an ignition device for an internal combustion engine that can perform the following steps.

[0011]

[Means for Solving the Problems] In order to achieve the above object, an ignition device for an internal combustion engine according to the present invention has a primary coil and a secondary coil wound around it, and is excited by energizing the primary coil. an ignition coil comprising an iron core and a permanent magnet that generates a magnetic flux in the opposite direction to the magnetic flux generated when the iron core is excited; a control signal generating means for generating a control signal for energizing a coil and cutting off the energization at the ignition timing; and a spark plug for discharging sparks by a high voltage generated in the secondary coil when the energization of the primary coil is cut off. In an ignition system for an internal combustion engine equipped with
The characteristic of the ignition coil is that when the current value when the primary coil is energized is small, the inductance of the primary coil is small, and as the current value is increased thereafter, the inductance of the primary coil becomes large, and the inductance of the primary coil increases to a predetermined value. The strength of the magnetic force of the permanent magnet is set so that the inductance of the primary coil is maximum at a current value, and the control signal generating means is in an internal combustion engine state that requires a large spark discharge at the spark plug. The present invention is equipped with a discriminating means for discriminating whether or not the spark plug is in a state of an internal combustion engine that requires a large spark discharge.

0012

[Operation] According to the present invention, when the characteristics of the ignition coil are such that the value of the current flowing through the primary coil is small, the inductance of the primary coil is small, and as the current value increases thereafter, the inductance of the primary coil increases. The inductance of the primary coil is maximized at a predetermined current value, and it is determined whether or not the internal combustion engine is in a state that requires a large spark discharge at the ignition plug. If it is determined that the internal combustion engine is in a state that requires discharge, the energization time of the primary coil is increased.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained below based on embodiments shown in the drawings. FIG. 1 is an overall configuration diagram showing the configuration of the apparatus in this embodiment.

In FIG. 1, reference numeral 1 is arranged, for example, on the crankshaft or camshaft of an internal combustion engine (not shown), and detects a signal output at each predetermined angle of each cylinder to determine the rotational speed N of the internal combustion engine.
This is a crank angle sensor that determines e (hereinafter referred to as engine speed). 2 is an intake pressure sensor that detects the pressure in the intake pipe of the internal combustion engine, and 3 is a water temperature sensor that is disposed in a cooling water passage of the internal combustion engine and detects the temperature of cooling water.

4 sets appropriate control amounts for the fuel system and ignition system based on the detection signals of the above-mentioned sensors and sensors not shown, and outputs control signals for accurately controlling the igniter, injector, etc., which will be described later. This is a known electronic control unit (hereinafter referred to as ECU).

Reference numeral 5 denotes an igniter that switches and controls a primary coil of an ignition coil, which will be described later, into a energized state or a non-energized state based on a control signal from the ECU 4. In addition,
The igniter 5 has a predetermined current Ia for the purpose of preventing overcurrent.
It is equipped with a constant current control circuit that controls the current so that it does not flow more than (for example, 7.5 A).

Reference numeral 6 denotes an ignition coil, and the ignition coil 6 is controlled by the igniter 5 to be switched between a energized state and a non-energized state, and a primary coil 61 that stores energy in the coil. It includes a secondary coil 62 that generates a high voltage when switched from a energized state to a non-energized state.

Reference numeral 7 designates a spark plug that receives a high voltage generated in the secondary coil 62 and discharges sparks within the combustion chamber of the internal combustion engine. Note that 8 is a battery, 9 is an ignition switch, 10 is a fuse that protects the circuit by blowing, and 11 is an injector that supplies fuel into the combustion chamber of the internal combustion engine based on an output signal from the ECU 4.

Next, the ignition coil 6 used in this embodiment will be explained based on FIG. 2. The basic structure of the ignition coil 6 is already disclosed in Japanese Patent Laid-Open No. 1-257311.

In FIG. 2, a primary coil 61 is wound around an inner bobbin 50, and on the inner circumference of the primary coil 61,
An iron core 63 whose one end is wide and flat is disposed, and this iron core 63 is excited when the primary coil 61 is energized. Note that the iron core 63 is made by punching a thin plate-like magnetic material (for example, soft iron) with oriented particles into a T-shape using a press or the like, and then laminating a plurality of these and pressing and caulking them.

In the air gap A between one wide and flat end of the iron core 63 and a closed magnetic path forming portion 66 described later, there is a magnetic flux generated when the iron core 63 is excited by energizing the primary coil 61. The permanent magnets 65 are arranged in such a manner that their polarities are repellent, that is, their adjacent surfaces have the same polarity. The permanent magnet 65 mainly uses a neodymium magnet or a rare earth magnet such as a rare earth-cobalt magnet, which generates a large magnetic force even though it is thin.The permanent magnet 65 will be explained in detail later.

On the other hand, on the outer periphery of the primary coil 61, there is an outer circumferential bobbin 51 which is fitted onto the inner circumferential bobbin 50, and a secondary coil 63 is wound around the outer circumferential bobbin 51. On the outside of the primary coil 61 and the secondary coil 63, there is a
A closed magnetic path forming section 66 having an annular shape is provided to surround the secondary coil 61 and the secondary coil 63.
has the effect that the generated magnetic flux forms a closed magnetic path and prevents leakage of the magnetic flux.

The closed magnetic path forming portion 66 is formed by punching soft iron or the like into an annular shape using a press or the like, and then laminating a plurality of these and pressing and caulking the same as the iron core 63. And iron core 6
3. The primary coil 61 and secondary coil 62, the closed magnetic path forming part 66, and the permanent magnet 65 wound around the outer circumference are housed in an ignition coil case 67, and a cast resin is further placed in the ignition coil case 67. The ignition coil 6 is formed by injection hardening 68.

Next, the operation of the ignition coil 6 having the above configuration will be explained below. When the primary coil 61 is energized, the iron core 63 is excited and generates magnetic flux. As mentioned above, this magnetic flux repels the magnetic flux generated from the permanent magnet 65, so even if the magnetic flux generated by the primary coil 61 is small, the iron core 6
3 can store large magnetic energy when energized.

Then, when the primary coil 61 is de-energized by the igniter 5 at the ignition timing, the magnetic energy accumulated in the iron core 63 is released, and the magnetic energy stored in the iron core 63 is released. An induced electromotive force is generated in the next coil 62. Here, since the secondary coil 62 has a larger number of windings than the primary coil 61, a high voltage is generated in the secondary coil 62 due to the induced electromotive force.

The high voltage generated by the secondary coil 62 is applied to the spark plug 7, causing spark discharge within the combustion chamber of the internal combustion engine. Here, the feature of the present invention, which is different from the conventional ignition coil equipped with a permanent magnet, is that the characteristics of the ignition coil 6 are as shown in FIG.
The magnetic force of the permanent magnet 65 is set so that the magnitude of the inductance L1 is small when the value is small (near 0), and then the inductance L1 increases as the primary current I1 increases, and the permanent magnet 65 is connected to the air gap A. It is to be placed inside. In addition, in FIG. 3, the horizontal axis represents the primary current I1,
The vertical axis shows the inductance L1 of the primary coil 61,
Also, the broken line shows the characteristics of an ignition coil that does not have a permanent magnet.
The one-dot chain line shows the characteristics of the ignition coil equipped with a conventional permanent magnet, and the solid line shows the characteristics of the above-mentioned ignition coil 6 equipped with the permanent magnet 65 of this embodiment.

That is, as shown by the solid line in FIG.
When the inductance L1 is small, the inductance L1 is extremely small, and as the primary current I1 increases, the inductance L1 also increases, and at a predetermined primary current I10, the inductance L1 becomes maximum, and thereafter the inductance L1 becomes small. 6
5.

On the other hand, in the conventional ignition coil equipped with a permanent magnet, the inductance L remains constant even if the primary current I1 changes.
Permanent magnets are arranged so that 1 hardly changes.

Further, the characteristics of the ignition coil 6 of the present invention are controlled by changing the number of turns of the primary coil 61 of the ignition coil 6, the size of the air gap A, and the magnetic force of the permanent magnet 65 disposed there. Specifically, by increasing the number of turns of the primary coil 61 or by decreasing the air gap A, the maximum value of the inductance L1 can be increased, and by further increasing the magnetic force, the primary current I1 can be increased. Inductance L at a small value (near 0)
1 can be made smaller.

[0030] Also, the primary coil 61 or the secondary coil 6
In order to store the same ignition energy by reducing the number of turns of the ignition coil 6, in other words, by reducing the shape of the ignition coil 6, the characteristics of the ignition coil should be approximately equal to the constant current value Ia during constant current control. It is desirable to design so that the maximum value of the inductance L1 is obtained at half the current value.

Therefore, in this embodiment, taking these things into consideration, the primary coil 61 is wound with a copper wire having a diameter of 0.85 mm 130 times, while the secondary coil 62 is wound with a copper wire having a diameter of 0.06 mm.
The copper wire is wound 11,000 times, and the air gap A
By making the size of the permanent magnet 65 and the iron core 63 twice as large as those of the conventional one, the magnetic flux density in the iron core of the ignition coil equipped with the conventional permanent magnet is reduced to 1.2 mm. It was set to 1.1T, which is 5 times higher.

Next, the effects obtained by manufacturing the ignition coil 6 so as to have the characteristics shown by the solid line in FIG. 3 will be explained based on FIGS. 4 and 5. FIG. 4 is a characteristic diagram of the ignition coil, with the horizontal axis representing the energization time t and the vertical axis representing the primary current I1. Similarly to FIG. 3, the broken line is the characteristic of the ignition coil without a permanent magnet, and the solid line is The characteristics of an ignition coil 6 with a permanent magnet 65 are shown.

It can be seen from FIG. 4 that the characteristics of the ignition coil 6 equipped with the permanent magnet 65 are such that the current rises earlier at the start of energization than the characteristics of the ignition coil not equipped with a permanent magnet.

Furthermore, FIG. 5 is a characteristic diagram of the ignition coil in which the horizontal axis shows the energization time t and the vertical axis shows the ignition energy accumulated in the primary coil. It can be seen that a large ignition energy can be stored in the ignition coil compared to an ignition coil without a permanent magnet. This is because the inductance L1 is small in the region where the energization time t is small, as shown in FIG. This is because a large ignition energy can be obtained due to the characteristic that L1 also becomes large.

Therefore, in a high-speed region where the current application time t is short, sufficient ignition energy can be secured by utilizing the rapid rise of the primary current I1, while on the other hand, when the current application time t
In the medium/low speed region where the inductance is long, an excellent effect of securing high energy can be obtained by using a region with a large inductance L1.

In order to obtain the above-mentioned effects, it is necessary that the ignition coil 6 has the characteristics shown by the solid line in FIG. In order to secure energy and obtain large ignition energy in the medium/low speed range, the inductance L1 at the predetermined primary current I10 must be
It has been confirmed through experiments by the inventors that the ignition coil 6 needs to be set so that the inductance L1 is 1.5 times or more when the inductance L1 is small.

It has been explained above that by using the ignition coil 6 of the present invention, it is possible to sufficiently store ignition energy even in a high-speed range where the energization time t is short. Next, an ignition control method using the above-mentioned ignition coil 6 will be explained based on the drawings. Specifically, it is determined whether or not the engine is in the lean burn area, and if the engine is in the lean burn area, ignition control is performed to supply large ignition energy.

FIG. 6 is a flowchart showing a known process for determining the lean burn region and setting the fuel injection amount, and is a routine executed at every predetermined crank angle. In step 100, the engine rotation speed Ne determined based on the detection result of the crank angle sensor 1 is read, and in step 11
0, the previous engine rotational speed Ne-1, which was read during the previous execution of this routine and stored in a storage device (not shown) in the ECU 4, is read.

In step 120, the current engine speed Ne
The engine speed fluctuation amount ΔNe is determined by subtracting the previous engine speed Ne-1 from the previous engine speed Ne-1. In step 130, a lean burn region determination value LK is obtained by multiplying the engine speed fluctuation amount ΔNe by a constant α determined according to the engine speed Ne.

In step 140, the engine speed fluctuation amount ΔN
e is compared with the lean burn area determination value LK, and if the engine speed fluctuation amount ΔNe is smaller than the lean burn area determination value LK, it is determined that the internal combustion engine is currently in a steady state, and the process proceeds to step 150 to perform open control. is used to control the fuel injection amount so that the air-fuel ratio becomes lean (for example, excess air ratio λ=1.4). Then, the process proceeds to step 160, in which a lean burn detection flag LMX indicating that the current state is in the lean burn area is set, and step 1
Proceed to 90.

On the other hand, if the engine speed fluctuation amount ΔNe is larger than the lean burn region determination value LK, it is determined that the internal combustion engine is currently in a transient state, and the process proceeds to step 170, in which the air-fuel ratio is adjusted to be near the stoichiometric air-fuel ratio. Feedback control of fuel injection amount. The process then proceeds to step 180, where the lean burn detection flag LMX is reset, and the process proceeds to step 190.

In step 190, the current engine speed Ne
is stored in the storage device as the previous engine speed Ne-1,
Return to main routine. FIG. 7 is a flowchart showing the operation of controlling the ignition energy supplied to the spark plug 7, in other words, the ignition energy accumulated in the primary coil 61, depending on the state of the internal combustion engine. In addition, FIG.
This is a routine that handles interrupts every time.

In step 200, the engine speed Ne is read, and in step 210, a basic energization time TB to the primary coil 61 is set based on the engine speed Ne read in step 100 and the voltage VB of the battery 8.

In step 220, the lean burn detection flag LMX is detected, and it is determined whether or not the lean burn detection flag LMX is set. If it is set, the process proceeds to step 230, and if it is not set, the process proceeds to step 260. move on.

In step 230, the intake pressure Pm of the internal combustion engine is read from the intake pressure sensor 2, and in step 240, the intake pressure Pm of the internal combustion engine is read from a two-dimensional map of the engine rotation speed Ne and the intake pressure Pm, based on the engine rotation speed Ne and the intake pressure Pm. Correction coefficient K
Find ij. Note that the correction coefficient Kij is the basic energization time T.
This is a value set to make the energization time longer than B.

In step 250, the basic energization time TB is multiplied by the correction coefficient kij to find the energization time t to the primary coil 61, and the process proceeds to step 290. On the other hand, when it is determined in step 220 that the lean burn detection flag LMX is not set and the process proceeds to step 260, in step 260, based on the detection result of the water temperature sensor 3, it is determined that the cooling water temperature Thw of the internal combustion engine is equal to or lower than the predetermined water temperature Th1. It is determined whether or not there is, and if the water temperature is below the predetermined water temperature Th1, the process proceeds to step 270, and if it is not below the predetermined water temperature Th1, the process proceeds to step 280.

At step 270, the basic energization time TB is determined because the ignitability is poor when the internal combustion engine is cold.
In order to make the energization time longer, the basic energization time TB is multiplied by the correction coefficient Ri to find the energization time t to the primary coil 61, and the process proceeds to step 310.

Furthermore, in step 280, the basic energization time T
B is set as the energization time t and the process proceeds to step 290. In step 290, a control signal is output to the igniter 5 so that the energization time t set by the method described above is reached. That is, by controlling the energization time t, it is possible to control the amount of ignition energy that is accumulated using the characteristics shown in FIG. 5, or in other words, the amount of ignition energy that is supplied to the spark plug.

[0049] Therefore, it is possible to obtain complete combustion in the combustion chamber of the internal combustion engine by determining the internal combustion engine condition that requires large ignition energy and supplying large ignition energy to the spark plug in such internal combustion engine condition. Can be done. Furthermore, instead of always supplying large ignition energy, normal ignition energy is supplied in operating conditions where there is no need to supply large ignition energy to the spark plug, such as outside the lean burn operation region, so large ignition energy is always supplied. This can prevent problems such as wear of the spark plug electrodes and increased power consumption.

Furthermore, even when the current application time t is short, such as during high rotation, it is possible to always store sufficient ignition energy as required by the action of the permanent magnet 65 as described above.

Furthermore, due to the action of the permanent magnet 65, the discharge current flowing through the secondary coil 62 has characteristics as shown by the solid line in FIG. ), it can be seen that the current density immediately after the start of discharge is larger. In general, the larger the current density at the initial stage of discharge, the better the flame kernel growth within the combustion chamber of the internal combustion engine. Therefore, by disposing the permanent magnet 65 in the ignition coil, the combustion state is further improved due to the above effect.

[0052]

As described above, in the present invention, when the characteristic of the ignition coil is that the value of the current flowing through the primary coil is small, the inductance of the primary coil is small;
Thereafter, as the current value increases, the inductance of the primary coil increases, and the strength of the magnetic flux of the permanent magnet is set so that the inductance of the primary coil becomes maximum at a predetermined current value. This provides an excellent effect in that ignition energy can be secured in a short time even in a region where the time for accumulating ignition energy is short, such as during high rotation.

Furthermore, it is determined whether or not the internal combustion engine is in a state that requires a large spark discharge at the ignition plug, and if it is determined that the internal combustion engine is in a state that requires a large spark discharge at the ignition plug, the primary coil is energized. By lengthening the time, an excellent effect can be achieved in that ignition energy can be supplied as needed.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of an apparatus according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the ignition coil shown in FIG. 1.

FIG. 3 is a diagram showing primary current-inductance characteristics in an ignition coil.

FIG. 4 is a diagram showing energization time vs. primary current characteristics in an ignition coil.

FIG. 5 is a diagram showing energization time versus ignition energy characteristics in an ignition coil.

FIG. 6 is a flowchart illustrating an operation for determining a lean burn operation region.

FIG. 7 is a flowchart for explaining the operation of the apparatus shown in FIG. 1;

FIG. 8 is a diagram showing discharge time-discharge current characteristics in an ignition coil.

FIG. 9 is a diagram showing primary current-ignition energy characteristics in an ignition coil.

FIG. 10 is a diagram showing energization time vs. primary current characteristics in an ignition coil.

FIG. 11 is a diagram showing the engine speed-ignition energy characteristic in the ignition coil.

[Explanation of symbols]

4 Electronic control unit (ECU) 5 Igniter 6 Ignition coil 61 Primary coil 62 Secondary coil 63 Iron core 65 Permanent magnet

Claims (2)

[Claims] 1. An iron core around which a primary coil and a secondary coil are wound, which is excited by energizing the primary coil, and which emits magnetic flux in the opposite direction to the magnetic flux generated when the iron core is excited. An ignition coil comprising a permanent magnet that generates electricity, and a control signal generation that generates a control signal to energize the primary coil a predetermined time before the ignition timing and cut off the energization at the ignition timing, based on the state of the internal combustion engine. and an ignition plug for discharging sparks by a high voltage generated in the secondary coil when the primary coil is de-energized, wherein the characteristics of the ignition coil are different from the primary coil. When the current value when energized is small, the inductance of the primary coil is small, and as the current value is increased thereafter, the inductance of the primary coil increases, and at a predetermined current value, the inductance of the primary coil is maximum. The strength of the magnetic force of the permanent magnet is set so that the control signal generating means includes a determining means for determining whether or not the internal combustion engine is in a state that requires a large spark discharge at the spark plug, An ignition device for an internal combustion engine, characterized in that when it is determined that the internal combustion engine is in a state that requires a large spark discharge in the ignition plug, the energization time of the primary coil is lengthened. 2. The characteristics of the ignition coil are such that the inductance of the primary coil at the predetermined current value is 1.5 times or more the inductance of the primary coil when the current value is small. The ignition device for an internal combustion engine according to claim 1.