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(11) | EP 0 033 748 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
| published in accordance with Art. 158(3) EPC |
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| (54) | DEVICE FOR CONTROLLING IGNITION TIMING |
| (57) A leading angle control system of low voltage distribution type in which there is
no high voltage distribution by means of a distributor. This system provides an ignition
reference signal having a predetermined angular duration not on the basis of the rotational
position of the rotary shaft of a distributor but on the basis of the position of
a crankshaft through a plurality of proximity switches, thereby eliminating an error
between the position of the crankshaft and the rotational position of the engine.
Thus, this system can accurately and stably control the ignition timing of the engine
to effect high practical value. |
TECHNICAL FIELD
BACKGROUND ART
[0002] For the purpose of controlling the ignition timing of engines, it has come to use a centrifugal advance mechanism and a vacuum advance mechanism disposed within the distributor mechanically coupled to engines. However, it is said that only the abovementioned mechanical control is insufficient and the electronic control is indispensable for the demands for motor vehicles of these days that harmful exhaust gases decrease and the operating performance and fuel characteristics are improved. General electronically controlled ignition control apparatus control the ignition timing by having, as one input, a reference position sensor disposed within the distributor and futther, as the other input, another sensor for sensing the operating status of engines, for example, a negative pressure in the suction manifold or like, calculating electrically the ignition timing and intermitting the primary current through the ignition coil. In this case a high voltage generated on the secondary side of the ignition coil is distributed among individual cylinders through a high voltage distribution mechanism for the distributor as usual. In this system, as the reference ignition signal has been obtained from a position of rotation of the rotary shaft of the distributor, there is the possibility of causing an error between it and the position of rotation of the engine and also the distributor is still required for the purpose of distributing a high voltage regardless of an advance mechanism being disused.
DISCLOSURE OF THE INVENTION
[0003] The present invention relates to an advance control system of a low voltage distribution system without the high voltage distribution effected through a distributor and makes it possible to control an ignition timing highly stably with an extremely high accuracy by obtaining reference ignition signals with predetermined angle widths from positions of a crank shaft through a plurality of access switches but not from positions of rotation of a rotary shaft of a distributor. Thus the practical merit is extremely great.
BRIEF DESCRIPTION OF-THE DRAWINGS
[0005] Figs. 2, 3 and 4 are diagrams of waveforms explaining the operation of the apparatus shown in Fig. 1. BEST MODE FOR CARRYING OUT THE INVENTION
[0006] Fig. 1 is a structural view illustrating an embodiment of the present invention. In Fig. 1 (1) is a rotary member mounted to a crank shaft (4) for a four-cylinder four cycle engine (not shown) and having a portion (100) with a different electrical property on one part of its periphery. (2) and (3) are access switches - mounted at positions symmetric with respect to the center of the rotary member (1) and disposed so as to generate outputs having pulse widths corresponding to the angle width of the portion (100) having the different electrical property at the periphery of the rotary member (1) in synchronization with the rotation of the rotary member (1). (5) is a negative pressure sensor for measuring a pressure in a suction manifold for the engine. (6) is an ignition control device having, as inputs, signals provided from the access switches (2) and (3) and the negative pressure sensor (6) and effecting the supply and interruption of currents to ignition coils (7) and (8) at proper timings. The ignition coils (7) and (8) have primary windings (70) and (80) and secondary windings (71) and (81) respectively. The primary winding (70) or (80) is connected at one end (700) or (800) to that side of an electric source (10) not connected to ground and the other end (701) or (801) to the ignition control device (6). The secondary windings (71) and (81) of the ignition coils (7) and (8) have output terminals (710), (711), (810) and (811) connected to ignition plugs (90), (91), (92) and (93) respectively. In Fig. 1 it is assumed that an ignition sequence is in the order of the ignition plugs (90), (91), (92) and (93). When the rotary member (1) is rotated in the direction of the arrow as shown in Fig. 1, electrical signals provided from the access switches (2) and (3) have waveforms such as shown in Fig. 2. If the tailing edge (100-T) of the portion with the different electrical property formed on the rotary member (1) is now set to a reference ignition position (for example, an upper dead point) of each cylinder, then points P90, P91, P92 and P93 coincide with the upper dead points of the cylinders corresponding to the ignition plugs (90), (91), (92) and (93) respectively. Accordingly if the primary current through the ignition coil (7) is interrupted, for example, at the point P90 then a high voltage is generated across the secondary winding (71) and the corresponding cylinder is ignited through the ignition plug (90). In this case the high voltage is also generated on the ignition.plug (91), but that cylinder corresponding to the ignition plug (91) is in its exhaust stroke at that time point. Therefore, an electric discharge occurs at a low voltage because a pressure within the clyinder is low. For this reason, the greater part of the high voltage generated across the secondary winding (71) of the ignition coil (7) is applied to the ignition plug (90) to supply to the ignition plug (90) energy required for an ignition. Also the reverse affair occurs at the point P91 in Fig. 2. That is, the point P91 is equal to the upper dead point of that cylinder corresponding to the ignition plug (91) and a greater part generated across the secondary winding (71) of the ignition coil (70) is applied to the ignition plug (91). Also a similar affair is also said with respect to the points P92 and P93 in Fig. 2. Thus, by interrupting the primary currents through the ignition coils (7) and (8) at the tailing edges of the electrical signals provided from the access switches (2) and (3) respectively, high voltages can be applied to the four ignition plugs (90), (91), (92) and (93) in the proper order. In the actual engines, the ignition timing is not fixed to the upper dead point as described above and it is required to cause the ignition at the proper timing in accordance with the operating status (the number of revolution, loading etc.) of the engines. In the embodiment of Fig. 1 the ignition control device (6) is used for this purpose. Namely the ignition control device (6) forms inputs of the reference position signal provided from the access switches (2) and (3), a signal for the number of revolution of the engine obtained by measuring the period of the reference position signals and a signal from the other sensor (the negative pressure sensor (5) in Fig. 2) for sensing the operating status of the engine, calculates the proper ignition position and controls currents through the ignition coils (7) and (8). That is, ignition signals are generated at points Q90, Q91, Q92 and Q93 leading tailing edges P90' P91' P92 and P93 of signal waveforms provided from the access switches (2) and (3) by angles of 8A as shown in Fig. 3 and interrupt the primary current through the ignition coil (7) or (8). In Fig. 3 the angle θA is an angle calculated and controlled by the ignition control device (6) and called generally an advance angle.
[0007] It is generally required to control the ignition timing to a position leading the reference ignition position (a temporally faster position) but in Fig. 3, for example, it is impossible to control the point Q91 by referring to the point P91 lagging behind the point Q91 and the control is effected as a delay time (or an angle) from the point P90 or P91 leading the point P91. In this case, a difference of at most 180° in angle of the crank shaft exists between the P90 and the point P91 and it is extremely difficult to control the point Q91 with a good accuracy. This is conspicuous particularly with the engine rotated non-smoothly. Also with the rotation of the engine varied abruptly, an abnormal advance is caused to stop the engine. In the extreme case the engine may be broken. Another object of the present invention is to eliminate such objections. In Fig. 1 the tailing edge (100-T) of the portion (100) having the different electrical property and disposed on the rotary member (1) is determined so as to correspond to the reference ignition position as described above, but a leading edge (100-L) is determined so as to correspond to a maximum advance required for the engine or a position leading the maximum advance by a constant magnitude. From this it is possible to avoid the abovementioned objections. In this case, the relationship between the signal waveforms provided from the access switches (2) and (3) and the ignition signal outputted from the ignition control device 6 is substantially as shown in Fig. 4. In Fig. 4 θM is of a magnitude of the maximum advance or a magnitude larger a constant angle than it. In the relationship between the waveforms such as shown in Fig. 4, the ignition timings Q90, Q91, Q92 and Q93 can be controlled as delays from the R90, R91, R92 and R93 by the ignition control device (6) respectively. Thus the control accuracy is sharply improved. Further, by limiting the ignition timings Q90, Q91, Q92 and Q93 so as not to advance beyond the R90, R91, R92 and R93 respectively, an abnormal advance can be prevented even with the rotation changed abnormally. Thus the great effect is present in the stable operation of the engine. Further, as the access switches (2) and (3) one can use the oscillation type sensing the access of a metal, or the Hall element type sensing the access of a magnetic material or the like.
[0008] As described above, the present invention relates to an advance control system of a low voltage distribution system without a high voltage distribution effected through a distributor and makes it possible to control the ignition timing highly stably with an extremely accuracy by providing reference ignition signals with predetermined angle widths from positions of a crank shaft through a plurality of access switches but not from positions of rotation of a rotary shaft of a distributor. Therefore the practical merit is extremely great.
INDUSTRIAL APPLICABILITY
[0009] The present invention is not restricted to an ignition timing control apparatus having a negative pressure sensor adopted as a sensor for sensing the operating status of an engine but it is equally applicable to ignition timing control apparatus inputted with a signal from the sensor for a temperature of cooling water, the atmospheric pressure, the air temperature or the like to control the ignition timing. Also regarding the number of cylinders of an engine there is no limitation and one can cope with six- or eight-cylinder engines by increasing the number of access switches and increasing the number of ignition coils. That is, three access switches and three ignition coils may be used with six-cylinder engines and four access switches and four ignition coils may be used with eight-cylinder engines thereby to realize similar affairs as in the four-cylinder engine.
(1) An ignition timing control apparatus consisting of a rotary member mounted to
a crank shaft for an engine, a portion having a different electrical property and
disposed on one part of said rotary member through a constant angle relative to a
direction of rotation, access switches disposed so as to sense the portion with the
difference electrical property on said rotary member, the number of said access switches
equaling one half the number of cylinders of the engine, at least one sensor disposed
so as to sense the operating state of said engine, an ignition timing control circuit
inputted with outputs from said plurality of access siwtches and said at least one
sensor, and a plurality of ignition coils connected to said ignition timing control
circuit.
(2) An ignition timing control apparatus according to claim (1), wherein a tailing
edge of the portion having the different electrical porperty with respect to the direction
of rotation of said rotary member is set to a reference ignition position of each
cylinder.
(3) An ignition timing conrol apparatus according to claim (2), wherein an electrical
signal provided from said reference ignition position is changed in accordance with
the operating status of the engine.
(4) An ignition timing control apparatus according to claim (1), wherein said ignition
timing circuit has inputs formed of reference position signals provided from said
access switches, a signal for the number of rotation of the engine obtained by measuring
the period of the reference position signals and an output signal from the sensor
for sensing the operating status of the engine.
(5) An ignition timing control apparatus according to claim (2), wherein a leading
edge of said portion with the different electrical property corresponds to a maximum
advance angle required for the engine or a position leading it by a constant magnitude.
(6) An ignition timing control apparatus according to claim (3), wherein the ignition
timing is set by a position leading a position of the electrical signal corresponding
to said reference ignition position by a predetermined angle calculated by said ignition
timing control circuit.
(7) An ignition timing control apparatus according to claim (1), wherein said access
switch senses the access of a metal.
(8) An ignition timing control apparatus according to claim (1), wherein said access
switch senses the access of a magnetic material.