JPH0533755A - Ignition device for internal combustion engine - Google Patents

Abstract

PURPOSE:To restrain knocking due to self ignition of end gas by always minifying end gas range to the utmost regardless of variation of the operating condition of an engine. CONSTITUTION:Eight pieces of optical fiber 4 are arranged extending over the full circumference of a cylinder bore 3 at every 45 deg., so as to face rheir extreme end parts in the nearly tangential direction of the cylinder bore 3. Photoelectric conversion devices 5 are connected to the base end parts of the respective optical fiber 4, and the contour of a flame propagating face is detected by means of a contour unit 6 based on their output signals. A laser ignition device 7 is provided with an adjustable-focus unit 12, and the focus position, namely, the ignition position is variably controlled by the output signal of the contour unit 6, so as to approximate the contour of the flame propagating face to a prescribed form.

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, such as a gasoline engine, which compulsorily ignites and burns a premixed gas in a combustion chamber, and more particularly to an ignition device for preventing knocking.

[0002]

2. Description of the Related Art In a premixed combustion engine such as a gasoline engine, the air-fuel mixture is generally ignited by a discharge spark of a spark plug, but when the compression ratio is increased, the ignition position is changed. In the peripheral portion of the distant cylinder bore, so-called end gas may self-ignite and knock may occur.

As a technique for reducing this knocking, various proposals have hitherto been made, for example, JP-A-61-3.
Japanese Patent No. 1941 discloses a configuration in which two spark plugs are used and flame propagation is performed from two points to narrow the end gas region. In addition, 62-59
Japanese Patent No. 775 discloses a configuration in which a pair of laser ignition devices are provided in place of the ignition plug, and similarly, two-point ignition is realized.

[0004]

However, in the above-mentioned conventional structure, the ignition position is fixedly set regardless of the actual knocking occurrence state, so that knocking cannot be suppressed surely. In particular, in the case where the site where the end gas is likely to change changes depending on the engine operating conditions or the like, there is no effect of suppressing knocking.

[0005]

Therefore, the present invention detects the actual distribution of the end gas that causes knocking, and changes the ignition position based on this.
That is, in the ignition device for an internal combustion engine according to the present invention, the tip portion is arranged so that the visual field region crosses the peripheral portion of the cylinder bore in a substantially tangential direction of the cylinder bore, and a plurality of portions are arranged at appropriate intervals all around the cylinder bore. Book optical fiber, photoelectric conversion device provided at the base end portion of the optical fiber, laser ignition device configured so that the focal position as an ignition position is movable, and outputs of the plurality of photoelectric conversion devices It comprises flame propagation surface detection means for detecting the shape of the flame propagation surface based on a signal, and control means for controlling the focal position of the laser ignition device according to the flame propagation surface shape.

Further, in the invention of claim 2, the flame propagation surface detecting means detects the deviation of the flame propagation surface from the shift of the peak timing of the output signal of each photoelectric conversion device, and the control means is configured to detect the deviation. The focus position is controlled in a direction to reduce the deviation.

[0007]

In the above structure, the field of view of each optical fiber crosses the peripheral portion of the cylinder bore, and a plurality of optical fibers are arranged around the entire circumference of the cylinder bore. The visual field area is formed in a polygonal shape.

At a certain point, when the air-fuel mixture is ignited by the laser igniter, the flame propagating surface spreads around this point, but when the flame propagating surface reaches the visual field area of the optical fiber, the optical fiber is An output signal corresponding to the flame is obtained from the connected photoelectric conversion device. That is, it is possible to know whether or not the flame propagation surface has reached the visual field area of each optical fiber, or when it has arrived, from the output signal of each photoelectric conversion device.

Therefore, the outline shape of the flame propagation surface and thus the distribution state of the end gas are detected based on the output signals of the plurality of photoelectric conversion devices. Then, the control means corrects the ignition position of the laser ignition device so that the flame propagation surface has an appropriate shape.

In particular, according to the second aspect of the invention, the deviation of the flame propagation surface is detected from the shift of the peak timing of the output signal of each photoelectric conversion device. In other words, if the flame propagation surface spreads evenly in the above-mentioned substantially polygonal field of view, the peaks of the output signals will be approximately the same, but if flame propagation is delayed in some areas, the output of the corresponding location The signal peak appears late.
Then, the ignition position is corrected in such a direction as to reduce this deviation, thereby locally suppressing the end gas from remaining.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

1 and 2 show the essential parts of an internal combustion engine equipped with an ignition device according to the present invention. In this embodiment, two intake valves 1 and two exhaust valves 2 are provided for each cylinder. They are provided one by one. Then, over the entire circumference of the cylinder bore 3, a total of eight optical fibers 4 (respectively denoted by 4a-4
(shown as h) are arranged at equal intervals, that is, every 45 °. As shown in the explanatory view of FIG. 3, this optical fiber 4 has a visual field region of a relatively narrow angle (θ), and a tip portion facing the combustion chamber is arranged so that each visual field region crosses the peripheral portion of the cylinder bore 3. The cylinder bore 3 is arranged substantially in the tangential direction. The tip of the optical fiber 4 is located above the cylinder bore 3 in correspondence with the flame formation position during ignition. Further, a photoelectric conversion device 5 including a phototransistor or the like for receiving the light that has passed through the optical fibers 4 is connected to the base end of each optical fiber 4. The output signals of the photoelectric conversion device 5 are input to the control unit 6, respectively.

On the other hand, a laser ignition device 7 is provided on the upper side surface of the cylinder bore 3 for each cylinder. The laser ignition device 7 includes a laser generator 8 for generating a laser beam, a condenser lens 10 formed of a convex lens fixed in a through hole 9 on the wall surface of the cylinder bore 3, and a concave lens forming an optical system together with the condenser lens 10. And a variable focus unit 12 provided with 11. The varifocal unit 12 has a pair of front and rear transparent glass plates 13 and 14 and a guide rod 15, and the concave lens 11 guided by the guide rod 15 is moved forward and backward by an actuator such as a servo motor (not shown). The position of the focal point S of the laser light can be moved back and forth. The laser generator 8 and an actuator (not shown) are controlled by an output signal from the control unit 6.
The optical axis of the laser ignition device 7 is directed so as to pass between the pair of intake valves 1 and between the pair of exhaust valves 2, as shown in FIG. That is, in the laser ignition device 7, the air-fuel mixture is ignited at the focal point S where the light energy is concentrated, and the focal point S becomes the ignition position. The ignition position can be moved along the optical axis by moving the focal point of the variable focus unit 12.

Next, the operation of the above embodiment will be described.

In the configuration in which the eight optical fibers 4 are arranged as described above, as shown in the explanatory view of FIG. 3, the field of view is formed in a substantially octagon as a whole, and the flame propagation is achieved. When the surface reaches this field of view, flame light is detected by the corresponding optical fiber 4. That is, the optical fiber 4
An output signal corresponding to the flame is obtained from the photoelectric conversion device 5 connected to. For example, if the flame propagating surface spreads substantially uniformly in each direction within the cylinder bore 3, the flame propagating surface reaches the field-of-view area of each optical fiber 4 at substantially the same time. Therefore, as shown in FIG. Output signal a of the converter 7
.About.h (the reference numerals correspond to the optical fibers 4a to 4h, respectively) at approximately the same time. With such a flame propagation surface shape, since the end gas does not locally remain, knocking is unlikely to occur. Incidentally, FIG. 4 also shows changes in the in-cylinder pressure.

On the other hand, when the flame propagation surface spreads in a biased manner as shown in FIG. 5, flame detection is delayed by some of the optical fibers 4, and as shown in FIG. There is a deviation in the rising edges of the output signals a to h of the converter 7. In such a flame propagation surface shape, the region indicated by reference character G in FIG. 5 becomes the end gas region, and knocking due to self-ignition easily occurs. Therefore, when such a flame propagation surface shape is detected, the ignition position of the laser ignition device 7 is corrected by the control unit 6 so as to reduce the deviation.

More specifically, as shown in the flow chart of FIG. 7, first, the deviation t ₁ between the peak times of the output signals a to h is set.
(See FIG. 6) is detected (step 1), and this is set value t
Compare with _c (step 2). Here, when the value is equal to or _smaller than the set value t _c , it is assumed that the flame propagation surface is substantially evenly spread, and the ignition position is not moved. On the other hand, when the set value t _c is exceeded, it is judged whether or not this state has continued for a predetermined number of cycles n ₁ or more (step 3), and the ignition position of the ignition position is limited only when it has continued for n ₁ times or more. Make a move. That is, the moving direction is determined based on which signal a to h is delayed (step 4), and the ignition position is moved by a fixed amount (step 5). In the example of FIG. 5, the ignition position is moved in the direction indicated by the arrow A, whereby the end gas region G
Is narrowed. When a strong swirl is given to the combustion chamber, the moving direction of the ignition position is determined in consideration of the swirl.

Therefore, in the above embodiment, the ignition position is constantly corrected so that the excessive end gas region G does not always occur, and even if the operating conditions change, an ideal combustion state in which the flame propagation surface spreads substantially evenly is obtained. To be kept. Therefore, knocking is surely suppressed.

In the above embodiment, the peak timings of the output signals a to h are compared, but the rising timings of the output signals a to h accompanying the arrival of the flame may be compared. Further, although the optical fibers 4 are arranged at the same inclination with respect to the cylinder bore 3 in the above-mentioned embodiment, the present invention is not necessarily limited to this, and may be arranged according to the shape of the combustion chamber.

Incidentally, the ignition energy provided by the laser ignition device 7 may be a constant value, but if the control unit 6 variably controls the ignition energy so as not to consume unnecessarily large energy,
The burden on the vehicle battery and alternator can be reduced. For example, when the air-fuel ratio is kept lean during steady operation, the amount of NO that easily ionizes in the residual gas increases, so that the ignition energy can be reduced. Further, in the variable compression ratio type engine in which the compression ratio can be changed by the vertical movement of the piston or the like, it is possible to ignite with a relatively small ignition energy at a high compression ratio.

Next, FIG. 8 shows a constitutional example in which one of the pair of intake ports 21 is provided with a swirl control valve 22 which is opened and closed by an actuator (not shown). This swirl control valve 22
In the case of the above, the gas flow in the combustion chamber greatly fluctuates between the open state and the closed state. Therefore, the optimum ignition position required to make the flame propagation surface shape unbalanced,
If the ignition position is gradually corrected as in the above-described embodiment, the deterioration of combustion and knocking are likely to occur temporarily at the time of valve switching. Therefore, in this embodiment, the optimum ignition position in the valve open state and the optimum ignition position in the valve closed state in the operation up to that time are always stored as learning values in the memory of the control unit 6 immediately after switching. Uses the learned value to control the ignition position. As a result, the ignition position can be immediately corrected to the optimum position even when the swirl control valve 22 is switched.

Next, FIGS. 9 and 10 show an embodiment in which the shape of the combustion chamber is changed by utilizing the above-mentioned laser ignition. That is, a four-valve engine having two intake valves 1 and two exhaust valves 2 generally has a pentroof type combustion chamber structure having an ignition plug at the center of the four valves, but in this embodiment, the pentroof is used. A smooth convex portion 23 is provided at the center of the die combustion chamber. According to this configuration, the swirls generated in the suction stroke remain without colliding with each other along the convex portion 23 as shown by the arrow in FIG. 10 in the compression stroke, and the gas flow in the combustion chamber is prevented. Be active. Further, the embodiment of FIG. 11 is formed by inclining the convex portion 23 to one side, and since the swirl that swirls along the up-down direction becomes a vortex that is obliquely inclined by the convex portion 23, it is further attenuated in the compression stroke. It becomes difficult to do.

[0023]

As is apparent from the above description, according to the ignition device for an internal combustion engine of the present invention, the ignition position is always set so that the end gas region becomes as small as possible even when the engine operating conditions, the cooling state, etc. change. Is variably controlled, so that a good combustion state is maintained and knocking is reliably suppressed.

[Brief description of drawings]

FIG. 1 is a structural explanatory view showing an embodiment of an ignition device according to the present invention.

FIG. 2 is a sectional view of a main part of an internal combustion engine equipped with this ignition device.

FIG. 3 is an explanatory view showing an example of a visual field region of an optical fiber and a flame propagation surface shape.

FIG. 4 is a waveform diagram showing an output signal waveform from each photoelectric conversion device.

FIG. 5 is an explanatory view showing an example of a flame propagation surface shape that spreads in one direction.

6 is a waveform diagram showing an output signal waveform corresponding to the flame propagation surface shape of FIG.

FIG. 7 is a flowchart showing a flow of control of an ignition position.

FIG. 8 is a structural explanatory view showing an embodiment including a swirl control valve.

FIG. 9 is an A- of FIG. 1 showing an embodiment in which the shape of the combustion chamber is changed.
Sectional drawing which followed the A line.

FIG. 10 is a sectional view taken along the line BB of FIG.

FIG. 11 is a sectional view similar to FIG. 10 showing a further different embodiment.

[Explanation of symbols]

3 ... Cylinder bore 4 ... Optical fiber 5 ... Photoelectric conversion device 6 ... Control unit 7 ... Laser ignition device

Claims (2)

[Claims] 1. A plurality of optical fibers, each of which is provided with its tip end portion oriented substantially in the tangential direction of the cylinder bore so that the field-of-view region crosses the peripheral portion of the cylinder bore, and which are arranged at appropriate intervals around the entire circumference of the cylinder bore. A photoelectric conversion device provided at each of the base end portions of the fibers, a laser ignition device configured so that the focal position as an ignition position is movable, and a flame propagation surface of the flame propagation surface based on each output signal of the plurality of photoelectric conversion devices. An ignition device for an internal combustion engine, comprising: flame propagation surface detection means for detecting a shape; and control means for controlling a focus position of the laser ignition device according to the flame propagation surface shape. 2. The flame propagation surface detecting means detects the deviation of the flame propagation surface from the shift of the peak time of the output signal of each photoelectric conversion device, and the control means reduces the deviation. The ignition device for an internal combustion engine according to claim 1, wherein a focal position is controlled.