JPS6052313B2 - 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, in combustion in a spark-ignition engine, as shown in Figure 1, 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 during the fire propagation period B-C. Next, 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 inversely 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 adjust the rotation speed, and when the negative pressure in the intake pipe is set to atmospheric pressure, the rotation speed increases. The characteristics of the ignition timing with respect to the engine speed are controlled, for example, as shown by the solid line in Figure 2. On the other hand, with respect to the load, a vacuum-type advance mechanism that uses the intake pipe negative pressure as an input signal is installed in the distributor to control the rotation. The characteristics of the ignition timing when the number is kept constant are controlled, for example, as shown by the solid line in FIG.

On the other hand, exhaust gas turbo superchargers have the advantage of being able to use the energy contained in the exhaust gas from the engine to improve the engine's 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 it is in a so-called non-turbo state, and turbocharging is performed above a certain speed and load range. (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 shift to top dead center, near top dead center, or in some cases before top dead center (Bm)C).

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-speed, low-load range where engine speed has not yet been reached, 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 will reduce engine output over the entire operating range. It's not a good idea.

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

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, 43 is a fuel injection nozzle, and 4 is an exhaust gas in which an exhaust turbine 5 and a blower compressor 6 and j are directly connected. A turbo supercharger, 7 indicates a muffler or a catalytic converter that discharges exhaust gas into the atmosphere, and a gathering 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 compressor A throttle valve 11 for controlling the intake air amount p, an air flow meter 10, and an air cleaner 12 are connected to the suction side of the engine 6, and an exhaust turbine 5 is connected to the suction side of the engine 6.
The exhaust side of the exhaust turbine 5 is connected to the muffler 7 via an exhaust pipe 13, and the inlet side of the exhaust turbine 5 is connected to the exhaust manifold 3 via an exhaust passage 14.

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. A breaker plate 20 having a breaker arm 19 with a contact 19'' that is turned on and off by rotation of the camshaft 16 is provided inside the breaker plate 20, and when the breaker plate 20 rotates in the direction of arrow 21, the ignition timing advances. If the angle direction is rotated in the direction of arrow 22, the angle shifts to the retard direction.

A first diaphragm type actuation mechanism 2f and a second diaphragm type actuation mechanism 24 are provided on the side surface of the distributor 15.
Both operating mechanisms 23 and 24 each consist of diaphragm cases 26 and 26, diaphragms 27 and 28, and diaphragm chambers 29 and 30, and the ends of connecting rods 31 and 32 connected to both diaphragms 27 and 28. lever 33
The central part of the lever 33 or the position that determines the amount of link movement according to the advance angle characteristic is connected to the breaker plate 20 via a rod 36. The first actuating mechanism 23 is provided with a spring 37 that resists movement of its diaphragm 21 from the illustrated position in the advanced angle direction, while the second actuating mechanism 24 is provided with a spring 37 that resists movement of its diaphragm 28 from the illustrated position in the retarded angle direction. A throttle boat 3 is provided with a spring 38 that resists movement and is provided in the diaphragm chamber 29 of the first actuating mechanism 23 slightly upstream from the closed position of the throttle valve 11.
9 is connected through a passage 40, and a boat 41 provided in the intake passage 9 is connected to the diaphragm chamber 30 of the second actuating mechanism 24 through a passage 42. 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 passage 9 is below atmospheric pressure, the second actuating mechanism 24 does not operate, and when idling with the throttle valve 11 closed, the pressure of the throttle boat 39 is atmospheric pressure, so the first actuating mechanism 23 also does not operate. When the throttle valve 11 is slightly opened, the throttle boat 39 becomes high negative pressure, and this negative pressure acts on the diaphragm chamber 29 of the first actuating mechanism 23 through the passage 40, and the diaphragm 27 resists the spring 37 and moves into the diaphragm chamber. 29, the lever 33 connected to this via the connecting rod 31 is pulled into the second position.
The ignition timing is advanced by rotating the breaker plate 20 connected to the lever 33 clockwise around the connecting pin 35 to the operating mechanism 24 in the advancing direction of the arrow 21.

Next, as the throttle valve 11 opens, the throttle boat 3
Since the pressure on the vacuum side of the breaker plate 9 gradually changes to approach atmospheric pressure, the diaphragm 27 of the first actuating mechanism 23 gradually moves to the left, thereby causing the breaker plate 20
are sequentially rotated in the slow direction via the lever 33 as the throttle valve 11 opens.

Therefore, the ignition timing by the breaker plate 20 is determined by the spring 3.
By setting the free length and spring constant of 7, it is possible to control the characteristics as shown by the solid line in Figure 3, so the actual ignition timing in the engine changes from the advance control amount due to an increase in engine speed to the increase in load. Automatic control can be performed to a value obtained by subtracting the delay control amount associated with this. That is, in the non-turbo region, ignition timing is controlled in the same way as a normal engine without a turbocharger. Then, when the throttle valve 11 is further opened, the amount of exhaust gas increases and the turbo supercharger 4 is sufficiently rotationally driven to enter a supercharging state. Throttle boat 39 due to large opening of throttle valve 11
The pressure in the intake passage 9 becomes atmospheric pressure, and the first actuating mechanism 23 stops operating at the illustrated position, while the pressure in the intake passage 9 gradually increases from atmospheric pressure as turbocharging increases, so the second actuating mechanism 24 The diaphragm 28 in is pressed to the left against the spring 38, and the lever 33 connected to it via the connecting rod 32 rotates to the left around the connecting pin 34 for the first actuating mechanism 23, and is interlocked with this. The breaker plate 20 is rotated in the retard direction of the arrow 22, and therefore, the ignition timing in the turbocharging region is added to the delay control of the first actuating mechanism 23 as the turbocharging increases. By setting the free length and spring constant of the spring 38, the actual ignition timing in the engine can be controlled to the characteristic shown by the two-point acute line in FIG. This control reduces the ignition delay period during turbocharging by setting the point D of maximum explosion pressure, and the top dead center at which the maximum pressure of the engine is obtained. It can be maintained at around 10. 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 turbocharging can be achieved without setting the compression ratio of the engine low. It is possible to reliably prevent knocking and engine damage during power-up, as well as obtain maximum output and improved fuel efficiency over the entire operating range.Furthermore, since the present invention uses two actuation mechanisms, the engine This has the effect that the characteristics during engine operation and on-turbo characteristics can be arbitrarily set to suit the engine.

[Brief explanation of the drawing]

Figure 1 is a pressure diagram showing the process of ignition and combustion of air-fuel mixture;
3 is a diagram showing advance angle characteristics with respect to engine speed, FIG. 3 is a diagram showing advance angle characteristics with respect to load, FIG. 4 is a diagram of an apparatus according to an embodiment of the present invention, and FIG. FIG. 1...Engine, 4...Turbocharger, 5...Exhaust turbine, 6...Blower compressor, 9...Intake passage, 10... Air flow meter, 11... Throttle valve, 15...
...Distributor, 16...Camshaft,
17...Centrifugal advance mechanism, 19...Breaker arm, 19''...Contact, 20...Breaker plate, 23...First operating mechanism ,2
4... Second operating mechanism, 27, 28... Diaphragm, 37, 38... Spring, 31, 32...
...Running rod, 33...Lever, 36...
・Rod, 39... Scuttle port.

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 includes a first actuation mechanism that operates the breaker plate in a retard direction by increasing the pressure of the throttle port, and an intake passage leading from the blower compressor to the engine. Ignition timing control for a turbocharged engine, characterized in that a second actuation mechanism is provided to actuate a breaker plate in a retarded direction by adding to the amount controlled by the first actuation mechanism due to the pressure increase. Device.