JPH0156255B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an intake system for a supercharged engine, and particularly to one that prevents excessive supercharging in high-speed operating ranges.

2. Description of the Related Art Conventionally, supercharged engines have been well known in which a supercharger is provided in an intake passage to perform intake supercharging in order to improve the output of the engine. And in this supercharged engine,
If the supercharging pressure increases too much, problems such as impairing the durability of the engine will occur, so the maximum supercharging pressure is controlled so that the supercharging pressure does not increase beyond a certain level. Conventionally, this type of control means includes a so-called supercharging relief method in which part of the intake air is relieved when the supercharging pressure in the intake passage exceeds a predetermined value, and a supercharging relief method in which the supercharger is driven by an exhaust turbine. A bypass passage that bypasses the exhaust turbine is provided in the exhaust system of an engine equipped with an exhaust turbo supercharger, and when the boost pressure exceeds a predetermined value, the bypass passage is opened and the exhaust turbine drives the supercharger. There is a so-called wastegate method that reduces the force, and all of these methods simply keep the boost pressure constant after the boost pressure reaches a preset value based on the intake pressure. It was designed to be maintained.

However, even if the boost pressure is maintained constant in this way, the intake air amount per unit time increases as the engine speed increases, so especially in high-speed operating ranges, the engine heat generation may increase excessively due to the increase in the intake air amount. There was a problem that this caused the fuel to rise, impairing the durability of the engine. In addition, in the high-speed operation range, the amount of exhaust gas per unit time increases and the exhaust temperature becomes excessive.This causes thermal deterioration of the catalyst installed in the exhaust system, and furthermore, the exhaust gas temperature per unit time increases. There were problems such as thermal deterioration of the exhaust turbine.

Therefore, in order to eliminate problems in the high-speed operating range of a supercharged engine that cannot be prevented simply by maintaining a constant maximum boost pressure value, the applicant has As the rotation speed increases, the amount of supercharging air relief is increased in the case of the supercharging relief method, and the amount of bypass of exhaust gas is increased in the case of the waste gate method.
By gradually lowering the boost pressure, we are able to prevent overcharging in high-speed operating ranges, improve engine durability, and prevent thermal deterioration of exhaust system catalysts, etc. (See the specification and drawings of Japanese Patent Application No. 56-25784).

The present invention has the same technical problem as the above-mentioned proposal, and as a means to solve the problem, the fully open position of a throttle valve provided in the intake passage for metering and controlling the amount of intake air is controlled in the high-speed operation region. By doing so, the supercharging pressure is reduced as the engine speed increases, thereby preventing excessive supercharging in high-speed operating ranges, improving engine durability and preventing thermal deterioration of exhaust system catalysts, etc. It is an object of the present invention to provide an intake system for a supercharged engine that can prevent such problems.

In this case, in the present invention, the fully open position of the throttle valve is controlled by an engine rotational speed signal and an intake pressure signal downstream of the throttle valve. At times, the throttle valve may be controlled to a fully open position even though the boost pressure has not risen sufficiently, creating a resistance to throttling the intake air, impeding boost response and deteriorating acceleration performance. There is.

Therefore, the present invention provides an intake system for a supercharged engine in which an intake passage is provided with a supercharger for supercharging the intake air and a throttle valve for metering and controlling the amount of intake air. In response to the intake pressure signal downstream of the throttle valve, the engine speed and intake pressure are set in advance so that the intake pressure downstream of the throttle valve at full load decreases as the rotation speed increases above a predetermined speed. The feature is that it is equipped with a control device that controls the fully open position of the throttle valve based on the function, thereby achieving the intended purpose of overcharging in the high-speed operation range without impeding the supercharging response. It is designed to prevent this.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

In FIG. 1, 1 is an engine, 2 is an intake passage, and 3 is an exhaust passage, a blower 4a is interposed in the intake passage 2, and a turbine 4b is interposed in the exhaust passage 3. The exhaust gas turbo supercharger is connected to via a connecting shaft 4c, a turbine 4b is rotated by the exhaust gas flow, and the rotation of the turbine 4b rotationally drives a blower 4a to open an intake passage. 4.

Further, the middle of the intake passage 2 downstream of the blower 4a of the exhaust turbocharger 4 is configured by arranging a primary side intake passage 2a and a secondary side intake passage 2b in parallel. A primary throttle valve 5 is interposed in conjunction with an accelerator pedal (not shown), and a secondary throttle valve 6 is interposed in the secondary intake passage 2b. An actuating device 7 constituted by a diaphragm device for opening and closing the secondary throttle valve 6 is connected to a valve lever 6b provided on the valve shaft 6a of the secondary throttle valve 6. The actuating device 7 is the valve lever 6b.
The diaphragm 7 is connected to the diaphragm 7 via the rod 7a.
b, an intake pressure chamber 7c and an atmospheric pressure chamber 7d defined by the diaphragm 7b, and the atmospheric pressure chamber 7
The intake pressure chamber 7c is connected to the upstream side of the secondary throttle valve 6 of the secondary intake passage 2b via the first intake pressure introduction passage 8. When the intake pressure (supercharging pressure) upstream of the secondary throttle valve 6 of the secondary intake passage 2b is below the setting, the intake pressure chamber 7c and the atmospheric pressure chamber 7d
The diaphragm 7b is biased to the right in the figure by the biasing force of the spring 7e, and the secondary throttle valve 6 is held in a fully closed state via the rod 7a. When exceeds the set value, a pressure difference occurs between the intake pressure chamber 7c and the atmospheric pressure chamber 7d, and this pressure difference causes the diaphragm 7b to shift to the left in the figure against the urging force of the spring 7e, and the rod 7a is configured to open the secondary throttle valve 6 via the above-mentioned boost pressure, and increase the opening degree of the secondary throttle valve 6 in response to an increase in the pressure difference accompanying the increase in the supercharging pressure. . The above-mentioned primary and secondary throttle valves 5 and 6 are used to quantitatively control the amount of intake air in the entire operating range of the engine 1.

Furthermore, 9 is a fuel injection valve disposed downstream of the primary throttle valve 5 of the primary intake passage 2a, and 10 is the blower 4a of the exhaust turbo supercharger 4.
The air flow meter 10 is arranged in the upstream intake passage 2 and detects the intake air amount, and the air flow meter 10 is connected to a fuel control circuit 11 that controls the fuel injection amount of the fuel injection valve 9. Therefore, a fuel injection type fuel supply device 12 is constructed, which injects fuel from the fuel injection valve 9 according to the amount of intake air and supplies it to the engine 1.

On the other hand, reference numeral 13 denotes an exhaust bypass passage provided in the exhaust passage 3 so as to bypass the turbine 4b, and a waste gate valve 14 constituted by a diaphragm device is provided at the branch part of the bypass passage 13 from the exhaust passage 3. is interposed. The waste gate valve 14 includes a valve body 14a that opens and closes the exhaust bypass passage 13 at the branch portion, a diaphragm 14c that supports the valve body 14a via a rod 14b, and a suction defined by the diaphragm 14c. Atmospheric pressure chamber 14d and atmospheric pressure chamber 14b
and a spring 14f compressed within the atmospheric pressure chamber 14e. ) to the upstream side of the secondary throttle valve 6 of the secondary side intake passage 2b, and the intake pressure (supercharging pressure) upstream of the secondary side throttle valve 6 of the secondary side intake passage 2b is set. When the value exceeds the value, the intake pressure chamber 14d and the atmospheric pressure chamber 14e
A pressure difference is generated between the two, and this pressure difference causes the diaphragm 14c to be biased to the left in the figure against the biasing force of the spring 14f, and the valve body 1 is pushed through the rod 14b.
4a to open the exhaust bypass passage 13, a part of the exhaust gas is transferred to the bypass passage 1.
A so-called waste gate system is configured in which the supercharging pressure is kept constant at the maximum supercharging pressure value by causing the supercharger to flow down by bypassing the turbine 4b, thereby reducing the supercharger driving force by the turbine 4b. ing.

As a feature of the present invention, 16 has a movable push rod 16a that comes into contact with the valve lever 6b of the secondary throttle valve 6 to regulate and control the fully open position of the secondary throttle valve 6. A control circuit 17 is connected to the proportional solenoid 16 for controlling the amount of protrusion of the push rod 16a, and a rotation speed sensor 18 for detecting the rotation speed of the engine 1 is connected to the control circuit 17. Signal (engine speed signal),
A detection signal (intake pressure signal) from an intake pressure sensor 19 that detects the intake pressure (supercharging pressure) downstream of the secondary throttle valve 6 of the secondary intake passage 2b is also input.

As shown in FIG. 2, the control circuit 17 is a function of the engine speed and intake pressure (corresponding to the supercharging pressure characteristic shown by the solid line in FIG. 3), which is preset based on the engine speed signal from the speed sensor 18. a set value circuit 20 that outputs a set value signal corresponding to the intake pressure value set based on
A comparator circuit 21 that compares the intake pressure signal from the set value circuit 20 with the set value signal from the set value circuit 20 and outputs a deviation signal as the deviation thereof, and an integral signal obtained by integrating the deviation signal of the comparator circuit 21 to calculate the proportional ratio. An integral circuit 22 for controlling the operation of the solenoid 16,
In response to the engine rotational speed signal and the intake pressure signal downstream of the secondary throttle valve 6, when the intake pressure signal has an output value greater than the set value signal based on the engine rotational speed signal, the push rod 16a of the proportional solenoid 16 protrudes. On the other hand, when the intake pressure signal has an output value smaller than the set value signal, the control is inverted to decrease the amount of protrusion of the push rod 16a of the proportional solenoid 16. As described above, at full load and above a predetermined rotation speed, the amount of protrusion of the push rod 16a of the proportional solenoid 16 is controlled to increase or decrease based on a preset function of the engine rotation speed and intake pressure, and as the rotation speed increases. The fully open position of the secondary throttle valve 6 is controlled to gradually decrease the opening degree from the maximum fully open position (the decreased opening degree is expressed as θ). A control device 23 is configured to gradually reduce the intake pressure as the rotational speed increases above a predetermined rotational speed.

Next, the operation of the above embodiment will be explained according to FIG. 3. When the engine 1 is in operation, as the engine speed increases, the rotation speed of the blower 4a of the exhaust turbo supercharger 4 increases and supercharging is performed. After the pressure (intake pressure) increases and the primary throttle valve 5 fully opens, the actuating device 7 operates to open the secondary throttle valve 6, which eventually becomes fully open.
Becomes fully loaded.

At full load, when the engine speed exceeds a predetermined speed, the intake passage 2 upstream of the primary and secondary throttle valves 5 and 6 (for example, A
In point), the waste gate valve 14
operates to reduce the supercharger driving force of the turbine 4b and maintain the rotation of the blower 4a almost constant, so that the supercharging pressure at point A increases as the engine speed increases, as shown by the broken line in Figure 3. It has a characteristic of maintaining almost constant (maximum intake pressure value) as the pressure increases.

On the other hand, the intake passage 2 downstream of the primary and secondary throttle valves 5 and 6 (for example, B in FIG.
At point), the amount of protrusion of the push rod 16a of the proportional solenoid 16 increases or decreases based on a preset function of the engine speed and the intake pressure by the operation of the control device 23, and increases or decreases as the engine speed increases. By gradually decreasing the fully open position of the next throttle valve 6, the supercharging pressure (intake pressure) at point B will gradually decrease as the engine speed increases, as shown in FIG. Intake pressure characteristics as shown by the solid line are obtained. In this case, the reason why the boost pressure (intake pressure) can be controlled to decrease by reducing the opening degree of the secondary throttle valve 6 is as follows.
When the opening degree of the secondary throttle valve 6 decreases,
The intake air flow rate first decreases, and the exhaust gas flow rate also decreases accordingly, so the energy for driving the turbine 4b of the exhaust turbo supercharger 4 decreases, and the supercharging pressure decreases. Furthermore, when the opening degree of the secondary throttle valve 6 decreases, a pressure loss occurs due to the throttling effect of the throttle valve 6, which actually affects the engine.
It depends on the reason why the pressure of intake air (supercharging pressure) drawn into the engine decreases.

At that time, at high speed, the secondary throttle valve 6
When the downstream intake pressure (supercharging pressure) is lower than the set value based on the engine speed, proportional solenoid 1
The amount of protrusion of the push rod 16a of No. 6 is reduced,
Since the fully open position of the secondary throttle valve 6 is controlled to be immediately increased to the maximum fully open position, the throttle resistance of the intake air is reduced and the intake pressure can be quickly increased to a predetermined value. Therefore, the supercharging response is good, and good acceleration performance can be ensured.

Therefore, in the high-speed operating range above a predetermined engine speed when the engine is fully loaded, the supercharging pressure (intake pressure) at point B acting on the engine 1 responds as the engine speed increases. Since the engine speed gradually decreases with good speed, excessive supercharging due to an increase in engine speed is prevented without impeding acceleration performance, and thus an excessive increase in engine heat generation or exhaust temperature is prevented, and the engine 1 The durability of the exhaust system can be improved, and thermal deterioration of the turbine 4b, catalyst (not shown), etc. provided in the exhaust system can be prevented.

In the above embodiment, the exhaust turbo supercharger 4 is used as the supercharger installed in the intake passage 2, but the same can be applied to a supercharging pump driven by another engine. It is.

Further, although a waste gate system is provided in the above embodiment, it is not necessarily necessary to provide the waste gate system, and the original purpose can be sufficiently achieved by using only the control device 23.

As explained above, according to the present invention, in a supercharged engine, the fully open position of the throttle valve is controlled in a high-speed operating region based on a function of a preset engine speed and the intake pressure downstream of the throttle valve. As a result, the intake pressure downstream of the throttle valve is reduced, ensuring good supercharging response, that is, good acceleration performance, and preventing excessive supercharging of the engine in high-speed operating ranges. It is possible to improve the durability of the exhaust system and prevent thermal deterioration of the exhaust system catalyst, etc.

[Brief explanation of drawings]

The drawings illustrate an embodiment of the present invention, and FIG. 1 is a general schematic diagram, FIG. 2 is a block diagram of a control device, and FIG. 3 is a graph showing boost pressure characteristics with respect to engine speed. 1...Engine, 2...Intake passage, 2a...Primary side intake passage, 2b...Secondary side intake passage, 3...Exhaust passage,
4... Exhaust turbo supercharger, 4a... Blower, 4b... Turbine, 5... Primary side throttle valve, 6... Secondary side throttle valve, 7... Actuating device, 12... Fuel supply device, 13... Exhaust bypass passage, 14...Wastegate valve, 16...Proportional solenoid, 17
... Control circuit, 18 ... Rotation speed sensor, 19 ... Intake pressure sensor, 20 ... Set value circuit, 21 ... Comparison circuit, 2
2... Integral circuit, 23... Control device.

Claims (1)

[Claims] 1. In an intake system for a supercharged engine in which a supercharger for supercharging the intake air and a throttle valve for metering and controlling the amount of intake air are interposed in the intake passage, the engine speed signal and the throttle valve downstream of the throttle valve are In response to the intake pressure signal of An intake system for a supercharged engine, characterized in that it is provided with a control device that controls the fully open position of a tutle valve.