JPS6252137B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an improvement in an ignition timing control device for an internal combustion engine, and in particular, to an improvement in an ignition timing control device for an internal combustion engine. The present invention relates to an ignition timing control device for an internal combustion engine equipped with a set centrifugal advance device.

[Technical Background of the Invention] Conventionally, gasoline engines and the like have been provided with an ignition timing control device to ignite at the optimum ignition timing according to the engine rotation speed and load in order to obtain the best output performance and fuel efficiency. .

Among ignition timing control devices, centrifugal advance devices that control ignition timing using rotational speed utilize the phenomenon in which a weight opens due to the centrifugal force of rotation, and apply the displacement to the timing lever using a cam mechanism. communicate,
The advance angle is given according to the rotation speed. This advance angle is determined to be the ignition timing that produces the maximum output at each rotational speed under full load, that is, the optimum ignition timing.

[Problems with the background technology] However, in recent years, there has been a tendency for gasoline engines to be designed with high compression ratios (specifically, 9.0 or higher) in order to improve fuel efficiency; When this happens, the gas temperature is high due to the high compression ratio, the combustion speed is fast, and the maximum pressure inside the cylinder is high, which increases the noise associated with combustion.

Setting the ignition control device to ignite at the optimal ignition timing mentioned above and increasing the compression ratio will increase output and improve fuel efficiency, but the maximum pressure in the cylinder will increase and combustion noise will increase. This is especially serious at high speed rotation, and causes practical problems.

This problem is even more serious in engines that use aluminum alloy for their cylinder blocks, which have a lower elastic modulus than iron, which results in louder noise.

Generally, when the amount of advance is large, combustion has already progressed considerably at the top dead center of the piston and the temperature is high, so the maximum pressure inside the cylinder becomes high and the combustion noise increases.

The amount of advance is determined by a centrifugal advance device that is set to almost pass through the optimal ignition timing (maximum output point) at each rotational speed under full load, and by a centrifugal advance device that is set to almost pass through the optimal ignition timing (maximum output point) at each rotation speed under full load. The advance angle is determined by combining the vacuum advance angle device, which is set to almost pass through the timing, but in this way, when the rotation is high and the load is medium to low, the centrifugal advance angle is also used due to the high rotation and high negative pressure. The vacuum advance angle also becomes maximum, the total advance angle amount becomes maximum, and the combustion noise becomes particularly large for the above-mentioned reason.

As described above, the conventional advance angle device that is a combination of a centrifugal advance device and a vacuum advance device cannot achieve both practical fuel efficiency improvement and noise reduction.

This drawback can be solved to some extent by introducing electronic control into the advance angle control so that the amount of advance angle can be determined freely, but at present, electronically controlled advance angle devices are complicated and expensive.

[Object of the Invention] Therefore, the object of this invention is to achieve a system without sacrificing fuel efficiency or power performance. This is intended to reduce combustion noise during high-speed rotation, which is a particular problem in practice.

[Structure of the Invention] In order to achieve this object, the present invention provides an ignition timing control device for an internal combustion engine in which the ignition timing is controlled by a centrifugal advance device so that the output decreases from the maximum output point at full load maximum output rotation speed. The ignition timing is set to the retard side from the optimum ignition timing so that it is within 4%, and the retard amount is gradually decreased at the rotation speed lower than the maximum output rotation speed to match the optimum ignition timing, and the ignition timing is set to be within 4%. The present invention is characterized in that it includes a centrifugal angle device that is set to gradually increase the retard angle amount (gradually decrease the advance angle amount) on the high speed rotation side.

[Embodiments of the Invention] Examples of the invention will be described below based on the drawings. FIG. 1 is an example in which the advance angle distribution of a power distributor equipped with a conventional vacuum advance angle device and a centrifugal advance angle device is expressed with engine rotational speed and output (load) as horizontal and vertical axes. In this case, the centrifugal advance angle should be advanced so that the line passes through the maximum output point at each rotational speed when the engine is operated at full load, as shown in Figure 2, that is, the line shown by the chain line in Figure 2. The amount of angle is determined. The solid line in Figure 1 is the full load output, and the advance angle on this line is determined by the chain line in Figure 2.
In the case of partial load, which is the actual operating condition, the vacuum advance device is activated and the advance angle is increased from this as shown in FIG.

The area indicated by B in Figure 1 is an area of medium to low speed and medium to low load, such as when driving in a city, and the centrifugal advance device does not operate much, but the vacuum advance device is activated to improve fuel efficiency. The advance angle is set to an appropriate value, but in the high-speed region shown in Figure 1A, both the centrifugal advance device and the vacuum advance device operate to their maximum, resulting in a large advance angle, which causes the gas temperature inside the cylinder to drop. Due to the increase in combustion rate, the combustion speed becomes faster, and as mentioned above, the maximum pressure increases, resulting in a significant increase in combustion noise.

As a measure to prevent this combustion noise, the case where the ignition timing is delayed is shown in FIGS. 3 and 4. Figure 3 shows the results of measuring the fuel consumption in 10 modes while keeping the centrifugal advance angle characteristics the same as before and changing the amount of vacuum advance. Delaying the ignition timing from the optimal ignition timing (MBT) reduces noise, but also reduces fuel consumption. Figure 4 shows the output when changing the use of the centrifugal advance angle during high-speed rotation. It can be seen that by reducing the advance angle amount, the noise is reduced, but the output is also reduced. Fifth
The figure shows the centrifugal advance angle characteristics with respect to the engine rotational speed for each advance angle shown in FIG.

Next, embodiments of the present invention are shown in FIGS. 6 to 9. FIG. 7 shows the centrifugal advance angle characteristics. The advance angle is zero at low speeds, and increases as the speed increases; in the conventional model, the advance angle is constant (30 degrees) above about 4,500 RPM, as shown by the broken line. In this example, at high speed, for example, 4500 RPM, as shown by the solid line.
at 28 degrees (point 1), at 5000 RPM 26 degrees (point 2),
The amount of advance angle decreases as the speed increases, such as 24 degrees at 5500 RPM (point 3).

As a procedure for determining this centrifugal advance angle characteristic, the eighth
In the ignition timing-output characteristic diagram at full load shown in the figure, the design maximum output rotation speed (in this example
5000RPM) to the maximum output point (30 degrees in this example, the output will decrease regardless of whether the advance angle increases or decreases from this point) to the ignition timing at which the output does not decrease much. Set the delayed point 2 (in this example, 4 degrees delayed from 30 degrees to 26 degrees). If the ignition timing is delayed, the output decreases as described above, but as a comprehensive evaluation, it is judged that an output decrease of 4% or less is acceptable, but a greater output decrease would be too costly.

At point 2 (26 degrees for 5000 RPM) determined as above, continue at a low speed (in this example
45000RPM), point 1 is on the advance side from the setting point 2.
(28 degrees in this example) and fast (in this example
5500RPM), set point 3 (24 degrees in this example) on the retard side of point 2.

FIG. 6 shows what the output will be when the centrifugal advance characteristic determined in this way is applied to the engine. In the figure, point 1 is
At 4500 RPM, the lead angle is 28 degrees, which is the highest output point, almost the same as before. Point 2 has a lead angle of 26 degrees at 5000 RPM, which is a slight decrease in output due to the output at the highest output point, and point 3 has a lead angle of 24 degrees at 5500 RPM.
The output has decreased considerably.

As described above, in the embodiment according to the present invention, from low speed to medium speed to high speed, the ignition is performed at the optimum ignition timing that provides the maximum output, as in the conventional case, and at the maximum output rotation speed, which is quite high, the output is slightly reduced. The advance angle is suppressed to such an extent that it causes a lag, and the advance angle is further suppressed at ultra-high speeds beyond that, resulting in a considerable drop in output, but this is unavoidable. Such an ultra-high-speed section has almost no chance of being used in practice, and this disadvantage can be easily tolerated in practice, as it also has effects such as over-speed prevention, which will be described later.

FIG. 9 shows an embodiment in which the centrifugal advance device according to the present invention is combined with a conventional vacuum advance device. 1st
Comparing with the figure, at low and medium speeds, there is no difference from the conventional one, and in high speed, medium and low load area A, the advance angle is, for example, 50 in Figure 1.
It can be seen that the angle has changed to 44 degrees in Figure 9.

In this way, the present invention aims to suppress the advance of the ignition timing in the ultra-high speed region and reduce combustion noise without sacrificing fuel efficiency and performance within the practical range.

As a specific mechanism for obtaining the centrifugal advance characteristic as shown in FIG. 7 according to the present invention, there are three possible mechanisms: (a) mechanical type, (b) electric type, and (c) mechanical + electric type.

The mechanical type (a) can provide the characteristics shown in Figure 7 by using a retard governor with a spring set to operate at a rotation speed higher than the rotation speed that reaches the maximum advance position. can. Alternatively, the shape of the window hole into which the weight pin fits may be formed so that the opening angle is delayed when the weight opens at high speed or higher (4500 RPM or higher in this example). Of course. Regarding the electric type (b), when an ignition signal obtained from the engine is input in the electrical distribution, a certain delay time "t" is provided so that the actual secondary side ignition voltage is delayed. The time it takes for the engine's crank angle to move becomes shorter in inverse proportion to the increase in rotational speed. Therefore, by providing a constant delay time "t", the amount of retardation from the conventional advance angle increases as the rotational speed increases.

Mechanical + electrical type (c) is a method that uses both types (a) and (b) together.

[Effects of the Invention] As explained above, according to the present invention, the following effects can be obtained.

(1) Combustion noise can be reduced by delaying the ignition timing at high speeds without sacrificing fuel efficiency or power performance.

In particular, combustion noise is generally large when the compression ratio is high, but the ignition timing control device according to the present invention has a significant noise reduction effect.

Further, even engines using aluminum alloy cylinder blocks are noisy, but the apparatus of the present invention has a remarkable noise reduction effect.

(2) According to this invention, the advance angle becomes smaller as the rotational speed increases during high-speed rotation, so it is possible to prevent damage to the engine due to overspeeding during practical operation.

(3) According to this invention, the design maximum output rotation speed can be clearly set.

[Brief explanation of the drawing]

Figure 1 is a graph showing the amount of advance with respect to rotational speed and output (load) of a conventional centrifugal/vacuum combination advance device. Figure 2 is a graph showing the change in output due to changes in ignition timing for each rotational speed at full load, and its The graph showing the maximum point, Figure 3, assumes that the centrifugal advance angle characteristics are the same.
A graph showing the results of measuring the 10-mode fuel efficiency when changing the amount of vacuum advance angle, Figure 4 is a graph showing the change in output when changing the amount of centrifugal advance angle at high speed rotation, and Figure 5 is a graph showing the change in output when changing the amount of centrifugal advance angle at high speed rotation. Figure 4 is a graph showing the centrifugal advance characteristic in the case of the present invention, Figure 6 is a graph showing the full load maximum output with respect to engine speed at high speed rotation using the centrifugal advance angle as a parameter, and Figure 7 is a graph showing the centrifugal advance angle characteristic according to the present invention. Graph showing the angle characteristics (solid line) and conventional characteristics (dotted line). Figure 8 is a graph showing the maximum output versus ignition timing using rotational speed as a parameter. Figure 9 is the same as the centrifugal advance device according to the present invention and the conventional one. 2 is a graph showing the distribution of advance angle with respect to rotational speed and output (load) of an internal combustion engine provided with a vacuum advance device.

Claims (1)

[Scope of Claims] 1. In an ignition timing control device for an internal combustion engine, the ignition timing is set by a centrifugal advance device to the optimum ignition timing so that the output decrease from the maximum output is within 4% at full load maximum output rotation speed. The retard angle is set to the retard side from
An ignition timing control device for an internal combustion engine, comprising a centrifugal advance device configured to gradually increase the retard amount (gradually decrease the advance amount) at a rotation speed higher than the maximum output rotation speed. 2. The ignition timing control device according to claim 1, wherein the compression ratio of the internal combustion engine is 9.0 or more. 3. The ignition timing control device according to claim 1, wherein the cylinder block of the internal combustion engine is made of aluminum alloy.