JPS6132482B2 - - Google Patents

Description

Detailed Description of the Invention The present invention forms an intake passage downstream of a throttle valve operated in conjunction with an accelerator pedal into a primary intake passage and a secondary intake passage, and a secondary intake passage is formed in the secondary intake passage. This invention relates to an intake system for an engine equipped with a throttle valve.

The intake system for this type of engine is known;
When the engine is idling with a small amount of intake air or operating at extremely low load, the sub-throttle valve should be fully closed.
By supplying intake air only from the next intake passage and increasing the intake flow rate, it is possible to form a swirl in the combustion chamber and improve the combustion rate of the air-fuel mixture, improving fuel efficiency. In a high-load operating range of the engine, the sub-throttle valve is fully opened to supply intake air from the secondary intake passage, thereby increasing charging efficiency and improving output.

However, as mentioned above, with the control method that controls the opening and closing of the sub-throttle valve on and off, when the sub-throttle valve is fully opened, a large amount of intake air is suddenly supplied from the secondary intake passage, resulting in swirl. There is a problem that the combustion characteristics of the engine become temporarily unstable due to the rapid weakening.

In order to solve this problem and improve fuel efficiency, Japanese Patent Application Laid-Open No. 54-74021 states that the sub-throttle valve should be maintained at a constant minimum opening in the extremely low load operating range of the engine, including idling. In the engine's low-to-medium load operating range, the sub-throttle valve is gradually opened at a relatively small slope as the load increases, and in the engine's high-load operating range, the sub-throttle valve is opened rapidly and fully opened. A control method for a throttle valve is disclosed.

This control method for the sub-throttle valve is designed to reduce intake air flowing down the secondary intake passage to increase the flow velocity in the engine's low-medium load operating range, where the amount of intake air is not large enough to fully open the sub-throttle valve. Since the swirl of intake air flowing into the combustion chamber from the next intake passage can be accelerated, combustibility can be maintained favorably, which has the advantage of further improving fuel efficiency.

Against this background, the present inventors conducted various tests on the relationship between fuel efficiency and sub-throttle valve opening, particularly in the low-medium load operating range of engines that are most frequently used. It has been found that fuel efficiency can be minimized by holding the sub-throttle valve at a constant opening rather than gradually opening the sub-throttle valve according to the load,
This has led to the completion of the present invention.

That is, the present invention provides an air intake system for an engine of the type described above, in which the opening degree of the sub-throttle valve is controlled in three stages depending on the engine load. In the range, the sub-throttle valve is almost fully closed, and in the low-medium load operating range, which is the normal operating range of the engine, the sub-throttle valve opening is kept constant at a predetermined opening. It is therefore an object of the present invention to provide an intake system for an engine that is equipped with a sub-throttle valve control device that opens the sub-throttle valve rapidly and fully opens the sub-throttle valve.

As explained below, such a sub-throttle valve control method not only can minimize fuel consumption, but also simplify the control structure of the sub-throttle valve itself and improve control stability. There are advantages.

Next, the results of experiments regarding fuel consumption rates conducted by the present inventors will be explained.

In this experiment, as shown in Figures 1 to 7, the average effective pressure Pe (Kg/cm ² ) and engine speed (rpm) were used as parameters, and the auxiliary throttle valve opening was measured under various intake negative pressures. Fuel consumption rate (/hr...at no load, gr/
This is a measurement of changes in ps/hr (under load).

As shown by the dots in Fig. 1 and Fig. 2, respectively, during idling operation when the intake negative pressure is -520 mmHg or more and during extreme load operation, the fuel consumption rate is minimum when the sub-throttle valve opening is 0°. Become.

On the other hand, as shown by dots ~ in Figures 3 to 7, when the engine is operated at low to medium load where the intake negative pressure is in the range of -520 to -150 mmHg, the auxiliary throttle valve opening is approximately 20 degrees in both cases. The fuel consumption rate is minimum at . The reason why the fuel consumption rate worsens when the angle is 20 degrees or less is thought to be that the swirl generated within the cylinder is too strong, causing an excessive increase in cooling loss.

From the results of this experiment, the points at which the fuel consumption rate is minimum are plotted with the horizontal axis representing the intake negative pressure corresponding to the engine load and the vertical axis representing the sub-throttle valve opening, as shown in Figure 8. becomes.

That is, during very low load operation of the engine, including idling operation with an intake negative pressure of -520 mmHg or more, the fuel consumption rate can be minimized by keeping the sub-throttle valve fully closed (0°);
The most frequently used intake negative pressure -520 to -150mmH
During low to medium load operation of the engine in the range of g, the fuel consumption rate in this operating range can be minimized by keeping the auxiliary throttle valve constant at a relatively low opening of about 20 degrees, contrary to expectations. be.

It is true that this experimental result cannot be asserted to be applicable to all engines equipped with the above-mentioned type of intake system, but as disclosed in the above-mentioned Japanese Patent Application Laid-open No. 74021/1983, it is This is extremely interesting as it qualitatively shows data that contradicts the prediction that fuel consumption can be minimized by gradually increasing the sub-throttle valve opening in the operating range as the load increases (intake negative pressure decreases). It is something. The reason why it is better to keep the opening degree of the sub-throttle valve constant regardless of the increase in load is because even if the opening degree is constant, the strength of the swirl increases as the load (intake air amount) increases. This increase characteristic is considered to be caused by the fact that it roughly matches the required swirl strength of the engine.

Examples of the present invention based on such experimental facts will be described below.

In the engine shown in FIG. 9, 1 is the combustion chamber 2
The intake passage 1 has a carburetor 3 equipped with a bench lily portion 4, a nozzle 5, a throttle valve 6, etc., and is connected downstream of the throttle valve 6 and from the intake manifold 7 to the cylinder head 8. A portion near the combustion chamber 2 formed inside is divided by a partition wall 9 into a primary side intake passage 1a with a relatively small passage area and a secondary side intake passage 1b with a relatively large passage area. The area is divided into sections.

A sub-throttle valve 10 for opening and closing the passage 1b is provided in the secondary intake passage 1b, and the sub-throttle valve 10 is controlled to open and close by a sub-throttle valve control device 11. The sub-throttle valve control device 11 is configured, for example, as a diaphragm device 12 having a double diaphragm structure in which a casing 12a is fixed on the intake manifold 7, as shown in the drawing.

The diaphragm device 12 has two upper and lower diaphragms 12b and 12c that connect the casing 12.
In order from the top of the figure, the inside of the first negative pressure chamber 12
d. It is partitioned into a second negative pressure chamber 12e and an atmospheric chamber 12f, and the intake negative pressure downstream of the throttle valve 6 of the carburetor 3 is constantly introduced into the first negative pressure chamber 12d through the first negative pressure conduit 13. The throttle valve 6 is connected to the second negative pressure chamber 12e through the second negative pressure conduit 14.
In other words, when the engine is idling or operating at a very low load, the throttle is The intake negative pressure downstream of the valve 6 is introduced.

In addition, coil springs are installed inside the first and second negative pressure chambers 12d and 12e as shown in the figure to constantly bias each diaphragm 12b and 12c downward, and the lower diaphragm 12c is The upper end of the actuating rod 15 is fixedly supported in the center, and the lower end of the actuating rod is connected to the valve shaft 1 of the sub-throttle valve 10.
It is connected to the free end side of the opening/closing lever 16 whose base is attached to the shaft end of 0a, and basically connects to the lower diaphragm 1.
The opening and closing of the sub-throttle valve 10 is controlled via the actuating rod 15 and the opening/closing lever 16 in accordance with the displacement of the throttle valve 2c.

The lift amount _l1 of the upper diaphragm 12b of the diaphragm device 12 is set by a stopper 12g fixed to the casing 12a, and
The lower diaphragm 12c has both diaphragms 1
The second diaphragm 12b is connected to the upper diaphragm 12b by the amount of play l set in the interlocking mechanism 12h provided between _2b and 12c.
It is designed to be able to be displaced against the spring force of the coil spring of the negative pressure chamber 12c.

In FIG. 9, 17 is an intake valve that opens and closes the intake port 1c at the downstream end of the intake passage 1, 18 is an exhaust valve that opens and closes the exhaust port 19a of the exhaust passage 19, and 2
0 is a valve operating mechanism that opens and closes the intake valve 17 and the exhaust valve 18 at predetermined timings in synchronization with the rotation of the engine, 21 is a cylinder block, and 22 is a piston.

Next, the opening/closing control of the sub-throttle valve 10 by the sub-throttle valve control device 11 will be explained with reference to FIGS. 9 and 10.

Now, when the engine is idling or operating at a very low load, when the throttle valve 6 is almost fully closed as shown in FIG.
3. Throttle valve 6 from both second negative pressure conduit 14
The high intake pressure downstream is the first and second negative pressure chambers 12d,
12e, the lower diaphragm 12c is lifted by the lift amount _l1 of the upper diaphragm 12b by the linkage mechanism 12h, and is further lifted by the amount of play _l2 of the linkage mechanism 12h. . Therefore, as shown in Figure 10,
The lift amount of the lower diaphragm 12c is (l ₁ +
l ₂ ), and the operating rod 15 and opening/closing lever 1
The sub-throttle valve 10 interlocked via the ninth
It is fully closed as shown by A in the figure.

Therefore, the small amount of air-fuel mixture supplied by the carburetor 3 is narrowed down by the primary intake passage 1a, which has a relatively small passage area, and the intake valve 17 is opened by the valve mechanism 20. Sometimes, it flows into the combustion chamber 2 at a high flow velocity and generates a swirl.

In this case, the primary side intake passage 1a is set to have a relatively flat passage cross section, and furthermore, as shown in FIG. To improve the combustion chamber of an engine by generating a strong swirl S by setting the passage width so that it becomes gradually narrower toward the end and oriented in the circumferential direction of the combustion chamber 2. is preferred.

Next, as shown in FIG. 9, the throttle valve 6
When the valve is opened beyond the set opening corresponding to the intake negative pressure, for example -520 mmHg, and the engine is shifted to low-medium load operation, the negative pressure outlet of the second negative pressure conduit 14 is opened from the throttle valve 6. Since it is located upstream, the second negative pressure chamber 1 is connected from the second negative pressure conduit 14.
The introduction of negative pressure to 2e is stopped.

Therefore, the lower diaphragm 12c, which had reached the maximum lift amount up to that point, is displaced downward by the play _l2 of the linkage mechanism 12h due to the spring force of the coil spring compressed in the second negative pressure chamber 12e, as shown in FIG. As shown in FIG. 3, the lift amount is maintained by the upper diaphragm 12b via the linkage mechanism 12h at a lift amount equal to the lift amount _l1 . Therefore, the sub-throttle valve 10
As shown in FIG. 9(b), the opening is opened to a constant opening degree of, for example, about 20 degrees from the fully closed state (a).

The opening degree of the auxiliary throttle valve 10 is such that the intake negative pressure downstream of the throttle valve 6 introduced into the first negative pressure chamber 12d by the first negative pressure conduit 13 is -520 to -150 mm.
The set load of the coil spring in the first negative pressure chamber 12d is determined so that it is kept constant as long as the Hg is within the range.

With this setting, the auxiliary throttle valve 10 is maintained at the opening that minimizes the fuel consumption rate during low-medium load operation of the engine corresponding to an intake negative pressure of -520 to -150 mmHg, and as a result, the fuel efficiency of the engine is improved. It can be the best one. As mentioned above, this driving range is the most frequently used driving range, and can improve fuel efficiency.

On the other hand, the throttle valve 6 is wide open as shown by the solid line in FIG. 9, and the intake negative pressure is -150 mmHg.
During high-load operation of the engine, the pressure inside the first negative pressure chamber 12d overcomes the low intake negative pressure introduced into the first negative pressure chamber 12d of the diaphragm device 12 through the first negative pressure conduit 13. The coil spring pushes down the upper diaphragm 12b, and the lower diaphragm 1
2c also follows this and the lift amount becomes zero, and as a result, the sub-throttle valve 10 is fully opened as shown by the solid line in FIG.

Therefore, during high-load operation where high engine output is required, a large amount of air-fuel mixture is supplied from the secondary side intake passage 16 to increase charging efficiency and ensure high engine output.

In the above embodiment, the diaphragm device 12 with a double diaphragm structure was used as the sub-throttle valve control device 11, but the present invention is not limited to this. It consists of a combination of a solenoid device and a detection device that detects the engine load condition, etc.
It goes without saying that it can be implemented in various ways.

As is clear from the above description, according to the present invention, fuel consumption can be effectively reduced during low-medium load operation, which is the normal operating range, and the sub-throttle valve control device can also be used to control the sub-throttle valve at three opening levels. Since it is not necessary to continuously change the opening degree, it is possible to obtain the advantage that the control can be performed easily and stably.

[Brief explanation of the drawing]

Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6, and Fig. 7 respectively show the fuel consumption rate when the sub-throttle valve opening is changed in a certain operating state of the engine. FIG. 8 is a graph plotting the sub-throttle valve opening at which the fuel consumption rate is minimized when the intake negative pressure is changed. FIG. 9 is a cross-section of an engine showing an embodiment of the present invention. FIG. 10 is a graph showing a method of setting the lift amount of the sub-throttle control device, and FIG. 11 is a plan view showing a preferred setting example of the primary intake passage. 1...Intake passage, 1a...Primary side intake passage, 1b...
Secondary intake passage, 6... Throttle valve, 10... Sub-throttle valve, 11... Sub-throttle valve control device.

Claims (1)

[Scope of Claims] 1. An intake passage downstream of a throttle valve operated in conjunction with an accelerator pedal is formed into a primary intake passage and a secondary intake passage, and the secondary intake passage has a passage of the intake passage. In addition to intervening a sub-throttle valve that changes the area, the sub-throttle valve is closed almost completely in the extremely low load range depending on the engine load condition, is kept at a predetermined constant low opening degree in the low and medium load range, and is An intake system for an engine, characterized in that it is provided with an auxiliary throttle valve control device that controls the throttle valve to be fully open in a load range. 2 The passage area of the primary intake passage is narrower than the passage area of the secondary intake passage, and the opening of the primary intake passage to the combustion chamber allows the intake air flowing down the primary intake passage to circulate within the combustion chamber. An intake system for an engine according to claim 1, which is configured to rotate in a direction.