JPS6052312B2 - Ignition timing control device for turbocharged engines - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ignition timing control device for an engine equipped with a supercharger, that is, an exhaust turbo supercharger, driven by an exhaust gas turbine.

In general, combustion in a spark ignition type engine is as shown in Fig. 1, where the air-fuel mixture is ignited at point B after a slight ignition delay period T from the spark ignition point A caused by the spark plug, and flame propagation from B to C occurs. After the period, the maximum explosion pressure is reached at point D through the direct combustion period of CD, and the process of reaching the afterburning period of DE takes place, and the point D of the maximum explosion pressure is set after the top dead center of the crank angle (
It is known that the maximum output of the engine can be obtained when the engine is set to about 100 (ATDC).

In this case, the ignition delay period T is approximately inversely proportional to the charging efficiency, which is the ratio of the weight of the intake fresh air mixture to the weight of the mixture occupying the stroke volume under standard conditions, and the charging efficiency is proportional to the rotation speed. is inversely proportional to the load, and directly proportional to the load, so the ignition delay period increases in proportion to the rotational speed and shortens in inverse proportion to the load. We have a relationship where this happens.

Therefore, in conventional ordinary engines (those without a turbocharger), a centrifugal advance mechanism is installed in the distributor to determine the rotation speed when the negative pressure in the intake pipe is set to atmospheric pressure. For example, the characteristics of the ignition timing for
While controlling the load as shown by the solid line in the figure,
The distributor is provided with a vacuum advance mechanism that uses the intake pipe negative pressure as an input signal to control the characteristics of the ignition timing when the rotational speed is kept constant, as shown by the solid line in FIG. 3, for example.

On the other hand, exhaust gas turbo superchargers have the advantage of being able to use the energy in the exhaust gas from the engine to improve engine output, but driving the exhaust gas turbine requires a considerable amount of exhaust gas energy. In an exhaust turbo type engine, turbocharging is not performed at low speeds and low load ranges where the amount of exhaust gas from the engine is small, so-called non-turbo state, and turbocharging is not performed at engine speeds and load ranges above a certain level. (on-turbo), the charging efficiency increases rapidly in the turbocharged state, and due to the rapid increase in the charging efficiency, the ignition delay period T becomes even more rapid than when the load increases in the non-turbo state. Therefore, if the conventional centrifugal and vacuum advance mechanism is directly applied to a turbocharged engine, the point D of the maximum explosion pressure in the turbocharged state will be the same as the ignition delay period due to supercharging. The shortening results in a transition to or near top dead center or even before top dead center (BTDC) as the case may be.

This shift of the highest explosion pressure point toward top dead center causes an explosion during compression during the upward stroke of the piston, which not only causes a sudden drop in engine output, but also increases noise due to knocking, and in some cases. This will eventually lead to damage to the engine, and an engine that can withstand this damage will be extremely heavy. Therefore, in order to prevent the maximum explosion pressure point D from shifting toward top dead center during turbocharging, the control characteristics of the ignition timing with respect to the rotation speed shown in FIG. It may be possible to move parallel to the retard direction by the amount of time it becomes shorter, as shown by the two-dot chain line, but in this case, the turbo supercharger will not operate or will operate sufficiently. In the low rotation/low load range where the engine speed is not reached, the optimal ignition timing cannot be controlled, resulting in negative results such as a decrease in output and an increase in fuel consumption.

Furthermore, when controlling the ignition timing of a turbocharged engine using the conventional method described above, it may be possible to prevent knocking during turbocharging by setting the compression ratio in the engine low. Lowering the compression ratio of the engine. This is not a good idea because the output will decrease over the entire operating range.

The present invention provides a turbocharged engine equipped with a throttle valve for controlling intake air amount upstream of a blower compressor of a turbocharger. In the non-turbo region where the opening of the throttle valve is small, the pressure of the throttle boat gradually approaches atmospheric pressure in proportion to the load on the vacuum side compared to atmospheric pressure, and the pressure from the blower compressor to the engine gradually approaches atmospheric pressure. Considering that in the turbocharging region when the throttle valve is wide open, the pressure in the intake passage changes to higher than atmospheric pressure as the turbocharging increases, the pressure in the intake passage is proportional to the engine speed. The ignition timing is controlled in the advance direction,
By controlling the ignition timing in the advance or retard direction depending on the pressure of both the throttle boat and the intake passage, the ignition timing during non-turbo is maintained at an optimal state, while the ignition timing during on-turbo is controlled by the turbo supercharging. The ignition timing is controlled in the retard direction by an amount commensurate with the shortening of the ignition delay period.

Next, an example of the present invention will be explained with reference to the drawings. In the drawing, 1 is an engine having an intake manifold 2 and an exhaust manifold 3, 36 is a fuel injection nozzle, and 4 is an engine having an exhaust turbine 5 and a blower compressor 6 directly connected. An exhaust turbo supercharger, 7 indicates a muffler or a catalytic converter that discharges exhaust gas into the atmosphere, and a collection part 8 of the intake manifold 2 is connected to the discharge side of the blower compressor 6 via an intake passage 9, and the blower A throttle valve 11 for controlling the amount of intake air, an air flow meter 10, and an air cleaner 12 are connected to the suction side of the compressor 6, and the exhaust side of the exhaust turbine 5 is connected to the muffler 7 via an exhaust pipe 13. 5 are connected to the exhaust manifold 3 via exhaust passages 14, respectively.

Reference numeral 15 denotes a distributor which is equipped with a centrifugal advance angle mechanism 17 having an advance angle characteristic, for example, as shown by the solid line in FIG. And, inside it, the ON. A breaker plate 19 having a breaker arm 18 with a contact point 1' that turns OFF is provided,
When the breaker plate 19 rotates in the direction of arrow 20, the ignition timing advances, and when it rotates in the direction of arrow 21, the ignition timing advances to retard.

Reference numeral 22 denotes a diaphragm type actuation mechanism for rotating the breaker plate attached to the side surface of the distributor 15. The actuation mechanism 22 includes a diaphragm case 23 and a diaphragm 25 connected to the breaker plate 19 via a quick rod 24.
and diaphragm chambers 26 and 27 formed on both sides thereof, one diaphragm chamber 26 includes a spring 28 that resists movement of the diaphragm 25 from the illustrated position in the advance angle direction, and the other diaphragm chamber 27 A spring 29 is provided in contact with each diaphragm 25 to resist movement of the diaphragm 25 in the retard direction from the illustrated position.

In this case, in another embodiment, as shown in FIG. 6, a spring 2' acting as a resistance in the retarding direction is provided in one diaphragm chamber 26 with both ends engaged with the case 23 and the diaphragm 25. Alternatively, as shown in FIG. 7, a spring 2' is provided in one diaphragm chamber 26, one end of which is engaged with the case 23, and the other end of which is engaged with the diaphragm 25, so that the spring 2' is moved in the advancing direction of the diaphragm 25. For the movement of the spring 2'
In other words, the compressive force of the spring 2' acts as a resistance to the movement of the diaphragm 25 in the retard direction. It can also be used for both. A throttle boat 30 is provided slightly upstream from the closed position of the throttle valve 11, and an intake pipe boat 31 is provided in the intake passage 9.
, 31 are connected to the passage 34 into the diaphragm chamber 26 in the actuating mechanism 22, when the pressure in the intake passage 9 is lower than atmospheric pressure, the pressure outlet passages 32, 33 from the throttle boat 30 are connected. A pilot switching valve 35 is provided to communicate the passage 32 with the passage 34 and to communicate the passage 33 from the intake pipe boat 31 with the passage 34 when the pressure in the intake passage 9 is higher than atmospheric pressure. .

Note that any mechanism other than the above may be used as a mechanism for detecting the turbocharging state based on a pressure change in the intake passage 9 and switching the pressure passage. In this configuration, the ignition timing of the engine is controlled by the centrifugal advance mechanism 17 in the distributor 15 as the engine speed increases according to the characteristics shown by the solid line in FIG. Controlled in the direction of travel.

On the other hand, in the region where the opening degree of the throttle valve 11 is small, the amount of intake air is small, and therefore the amount of exhaust gas is small and the rotation of the turbo supercharger 4 is slow, so supercharging by the turbo supercharger is not performed and the intake pipe The pressure of the boat 31 is below atmospheric pressure, and the switching valve 35 communicates the passages 32 and 34. The pressure of the throttle boat 30 is atmospheric pressure during idling when the throttle valve 11 is closed, but when the throttle valve 11 is slightly opened. This results in a high negative pressure, which acts via the passages 32, 34 on the diaphragm chamber 28 of the actuating mechanism 22, the diaphragm 25 of which is forced into one diaphragm chamber 26 against the spring 28 or the spring 2'. By pulling the breaker plate 19 and rotating it in the advance direction of the arrow 20, the ignition timing is advanced, but the pressure on the vacuum side of the throttle boat 30 increases as the throttle valve 11 opens. Since the pressure gradually changes to approach atmospheric pressure, the breaker plate 19 is sequentially rotated in the retard direction by the spring 28 or 28'' as the throttle valve 11 opens.Therefore, the ignition timing by the breaker plate 19 is controlled by the spring. 28
Or 2: By setting the free length and spring constant, it is possible to control the characteristics as shown by the solid line in Figure 3, so the actual ignition timing in the engine is determined by the advance control amount due to the increase in engine speed, It is possible to automatically control to a value obtained by subtracting the delay control amount due to an increase in . In other words, in the non-turbo region, ignition timing is controlled in the same way as a normal engine without a turbocharger. and,
When the throttle valve 11 is further opened, the amount of exhaust gas increases and the turbo supercharger 4 is driven to rotate sufficiently and shifts to the supercharging state, and the pressure in the intake passage 9 decreases from atmospheric pressure as the turbo supercharging increases. Since the pressure gradually increases, when this pressure rise reaches a predetermined value, the switching valve 35 detects the turbocharging state and switches the passage 3
2 and 34 are switched to communicate with each other.

Then, the supercharging pressure of the intake pipe boat 31 acts on the diaphragm chamber 26 in the actuating mechanism 22, and the diaphragm 25
The spring 29, 29'' or 2'' is pressed in the direction of the other diaphragm chamber 27 against the force of the breaker plate 1.
9 is rotated in the retarded direction of the arrow 21. Therefore, even in the turbocharging region, the ignition timing can be controlled in the retarded direction as the turbocharging increases, and the springs 29, 29
By setting the free length and spring constant of `` or 2'', it is possible to control the characteristics as shown by the two-dot chain line in Figure 3, so the actual ignition timing in the engine will change as the supercharging increases compared to the non-turbo mode. This control reduces the ignition delay period during turbocharging by setting the point D of maximum explosion pressure to about 10 minutes after top dead center, where the maximum output of the engine is obtained. As described above, according to the present invention, the ignition timing in a turbocharged engine can be accurately and automatically controlled over the entire operating range from non-turbo to on-turbo, so that the compression ratio of the engine can be maintained at It is possible to reliably prevent knocking and engine damage during turbocharging without having to set the engine too low, and it also provides maximum output and improved fuel efficiency in all operating ranges.
Moreover, since the diaphragm of the actuating mechanism in the present invention only needs to be provided with a spring that operates in the advance and retard directions, the structure is not only extremely simple, but it can operate reliably with few failures and can be provided at low cost. This has the effect that the control characteristics can be arbitrarily set according to the engine using the spring.

[Brief explanation of the drawing]

Figure 1 is a pressure diagram showing the process of ignition and combustion of air-fuel mixture;
The figure shows the advance angle characteristics with respect to the engine speed.
4 is a diagram showing the advance angle characteristics with respect to load, FIG. 4 is a diagram of the device according to the embodiment of the present invention, FIG.
FIG. 7 is a sectional view of another embodiment. 1... Engine, 4... Turbo supercharger,
5... Exhaust turbine, 6... Blower compressor, 9... Intake passage, 10... Air flow meter, 11... Scuttle valve, 15...・Distributor, 16...Camshaft, 17...
...Centrifugal advance mechanism, 18...Breaker arm, 1'...Contact, 19...Breaker plate, 22...Operating mechanism, 25... ...Diaphragm, 26...Diaphragm chamber, 28,
29,2',29゛...spring, 30...throttle boat.

Claims (1)

[Claims] 1. In a turbocharged engine in which a throttle valve for controlling the amount of intake air is provided upstream on the suction side of a blower compressor in an exhaust turbocharger, a throttle port is provided slightly upstream from the closed position of the throttle valve; The distributor with a centrifugal advance mechanism in the engine is provided with a diaphragm-type actuation mechanism that operates the breaker plate in the advance and retard directions, and the diaphragm of the actuator has a diaphragm that operates the breaker plate in both the advance and retard directions. An ignition timing control device for a turbocharged engine, characterized in that the diaphragm chamber is provided with a spring that operates, and the pressure from the throttle port and the pressure from the intake passage leading from the blower compressor to the engine are introduced into the diaphragm chamber. .