JPS6189929A - Intake device of supercharged engine - Google Patents

Abstract

PURPOSE:To obtain preferable accelerating characteristics by delaying a closing timing of a bypass valve when an engine is accelerated over a specified speed so as to quickly increase supercharging pressure when the bypass valve is closed. CONSTITUTION:When the quantity of intake air is low (that is, then an engine runs at a low speed) because a throttle valve 14 is opened at only a small angle, a bypass valve 18 is opened to supply natural intake air from a bypass passage 17 having a low intake resistance. The charging efficiency of intake air can thereby be improved. When the quantity of intake air is high (that is, when the engine runs at a high speed) because the throttle valve 14 is opened widely, the bypass valve 18 is closed to prevent a reflux of supercharged intake air into the bypass valve 18. A supercharged intake air of a specified pressure can thereby be supplied. If a throttle sensor 24 senses that the engine is accelerated over a specified speed, a timing at which the bypass valve 18 is to be closed is delayed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an intake system for a supercharged engine that supplies pressurized air from a turbocharger in addition to naturally aspirated air.

(Prior Art) Conventionally, a supercharged engine that supplies pressurized air in addition to naturally aspirated air is disclosed in, for example, Japanese Patent Laid-Open No. 57-203.
It is known as seen in No. 819. In such an engine that uses natural intake and intake supercharging, in order to improve the output over the entire range from low speeds to high speeds, since the characteristics of the turbocharger are low at low speeds, natural intake is used to improve the output over the entire range from low speeds to high speeds. While supplying air to the engine, at high speeds, in addition to this naturally aspirated air, pressurized air from a turbocharger is supplied to improve the filling amount. In other words, if air is supplied to the engine only through a supercharging passage equipped with a turbo supercharger, the turbo supercharger will act as resistance to intake air at low speeds, reducing charging efficiency. This is to improve the natural aspiration. On the other hand, at high speeds, intake air is insufficient with natural intake alone, so charging efficiency is increased by intake supercharging using a turbo supercharger.

In other words, the natural intake passage is opened and closed with a characteristic opposite to the opening degree of the throttle valve.

However, in the intake system of a supercharged engine as described above, if the natural intake passage is immediately closed in response to the opening of the throttle valve during acceleration, the turbine output of the turbocharger will decrease. Therefore, sufficient acceleration cannot be obtained.

(Object of the Invention) In view of the above circumstances, the present invention provides an intake air intake for a supercharged engine that rapidly increases supercharging pressure by a turbo supercharger to obtain good acceleration performance when acceleration exceeds a predetermined value. The purpose is to provide a device.

(Structure of the Invention) The intake system of the present invention comprises an engine intake passage including a supercharging passage provided with a turbo supercharger and a bypass passage bypassing the turbo supercharger, and a bypass passage provided in the bypass passage. Regarding opening the bypass valve at low speeds and opening the valve at high speeds, the control device controls the closing timing of the bypass valve to be delayed by a predetermined time when the acceleration detected by the acceleration sensor is equal to or higher than a predetermined value. It is something.

(Effect of the invention) According to the present invention, at low speeds, the bypass valve is opened to perform natural intake, and at high speeds, the bypass valve is closed to perform intake supercharging, and the charging amount is increased from low to high speeds to improve the output characteristics. In addition to improving, when sudden acceleration exceeds a specified value,
By delaying the timing of closing the bypass valve, the bypass valve closes when the rotational speed of the turbo supercharger has sufficiently increased, and when it closes, the supercharging pressure increases rapidly, resulting in good acceleration. At other times of acceleration, the supercharging pressure gradually increases in accordance with the acceleration state, and smooth acceleration is obtained without the shock when the bypass valve closes.

(Example) Hereinafter, the present invention will be explained in detail with reference to the drawings.

Figure 1 shows a schematic configuration of an engine equipped with an exhaust turbo supercharger, and a cylinder 2 of the engine 1 has a primary intake boat 3.
．． A secondary intake port 4 and an exhaust port 5 are opened.

The intake passage 7 that supplies intake air to the intake boats 3 and 4 is
The intermediate section is composed of a supercharging passage 16 with a turbo supercharger 8, and a bypass passage 17 that bypasses the turbo supercharger 8 of this supercharging passage 16 and joins at a surge tank 9 on the downstream side. There is.

The intake passage 7 on the downstream side of the surge tank 9 is a primary passage 7a connected to the primary intake port 3 of the cylinder 2.
and a secondary passage 7b connected to the secondary intake port 4. A fuel injection nozzle 10 is provided in each of the primary and secondary passages 7a and 7b, and the secondary passage 7b
An on-off valve 11 for opening and closing this secondary passage 7b is interposed, and the on-off valve 11 is opened in response to an increase in the amount of intake air.

On the other hand, in the intake passage 7 on the upstream side of the supercharging passage 16, an air cleaner 12, an air flow meter 13 that detects the intake air amount, and a throttle valve 1 that opens and closes depending on the load are installed.
4 are arranged.

The supercharging passage 16 also includes a blower 8a of the turbo supercharger 8.
, and an intercooler 15 for cooling intake air are arranged in this order. In this turbo supercharger 8, a turbine 8b interposed in an exhaust passage 6 connected to an exhaust port 5 is driven by exhaust gas, and a blower 8a connected to the turbine 8b.
This pressurizes the intake air.

- A bypass valve 18 that opens and closes the bypass passage 17 is interposed in a bypass passage 17 that bypasses the blower 8a of the turbocharger 8 and is connected to the surge tank 9. An actuator 19 that opens and closes the bypass valve 18 is connected to the bypass valve 18 .

The actuator 19 is driven by a control signal from a control device 22 (control unit), and the opening/closing operation of the bypass valve 18 is controlled. This control device 22
In addition to the intake air amount signal from the air flow meter 13, a signal from the pressure sensor 23 that detects boost pressure, and a signal from the throttle sensor 24 that detects the opening degree of the throttle valve 14 to detect the acceleration state. , and a signal from a rotational speed sensor 25 that detects the engine rotational speed are respectively input.

Based on these signals, the control device 22 operates the bypass valve 18 basically as shown in solid lines in FIG.
The opening degree of the bypass valve 18 is controlled to be set in accordance with the intake air amount based on the signal from the air flow meter 3. That is, at low intake times (at low speeds) when the throttle opening is small, the bypass valve 18 is used to perform natural intake through the bypass passage 17 with low intake resistance to improve charging efficiency, and the throttle opening is increased. When the intake port is increased (high speed), the bypass valve 18 is closed to prevent intake supercharging from flowing back to the bypass valve 18, thereby supplying supercharging air at a predetermined pressure.

■ Also, when the throttle sensor 24 detects an acceleration of more than a predetermined value, as shown by the broken line ■ in FIG. This is a correction to shift it to the child side, that is, to the delay side.

When the opening and closing of the bypass valve 18 is controlled based on the characteristics shown in FIG. 2 in accordance with the acceleration state as described above, the increase in supercharging pressure during acceleration is as shown in FIG. 3. However, as shown in Figure 3C, during sudden acceleration when the throttle opening suddenly changes to full open, the throttle opens fully as shown by the broken line in No. 3N8, and the intake port reaches the predetermined intake port. If the conventional control characteristic is to close the bypass valve 18 as soon as the bypass valve 18 is opened (the characteristic shown in As a result, the boost pressure gradually increases. On the other hand,
As shown by the solid line in FIG. 3B, the bypass valve 18 of the present invention is closed after a delay of a predetermined time t until a predetermined intake ω that has been corrected to a large value is reached after the throttle opening reaches the full nU. With the control characteristics (characteristics shown in ■ in Figure 2), as shown by the solid line in Figure 3A, the throttle valve 1
2 opens, the intake pressure rises from a negative pressure state to atmospheric pressure, and this atmospheric pressure state is maintained until the bypass valve 18 closes, but the amount of intake air, that is, the amount of exhaust gas increases. Since then, the rotational speed of the turbocharger 8 has become high. When the bypass valve 18 is closed from this state, the supercharging pressure increases rapidly, and the high supercharging pressure provides good acceleration performance.

Furthermore, when intake supercharging is being performed and the signal from the pressure sensor 23 indicates that the supercharging pressure has increased to a set value or higher, the actuator 19 opens the bypass valve 18 . When the bypass valve 18 is opened, a portion of the pressurized air supplied from the blower 8a to the surge tank 9 is relieved upstream by the bypass passage 17 and introduced into the blower 8a again, and is then introduced into the intake port of the engine 1. On the other hand, the feed amount by the blower 8a is increased to control the supercharging pressure.

The closing characteristic of the bypass valve 18 depending on the acceleration state is as shown in FIG. 2, in which the valve closing speed is constant in any acceleration state, and the valve closing speed may be variable in addition to a characteristic in which the valve closing speed is delayed as a whole. That is, as shown in Fig. 4, under normal conditions, the bypass valve 18 is gradually closed at a small closing speed when the set intake air amount is reached, as shown by the solid line ■, but when accelerating, the broken line ■ shows an even more rapid acceleration. Sometimes dashed line■
While delaying the valve closing start time as in
8 may be closed rapidly at a large valve closing speed.

When the bypass valve 18 is abruptly closed in this manner, the degree of increase in supercharging pressure is also large, and a rapid pressure increase characteristic is obtained.

Furthermore, when the timing of closing the bypass valve 18 is delayed when acceleration exceeds a predetermined value, the timing of closing the bypass valve 18 is delayed depending on the degree of acceleration as described above, and the longer the sudden acceleration is, the longer the delay is. The amount of delay may be changed accordingly. That is, when accelerating from a low engine speed, it takes time for the turbocharger 8 to increase its rotation, so the amount of delay is increased, and after the rotation has increased sufficiently, the bypass valve 18 is closed and the supercharging pressure is increased. On the other hand, when accelerating from a state where the engine speed is high to a certain extent, the speed of the turbocharger 8 also increases to a certain extent, so even if the delay is small, the boost pressure will not rise sufficiently. That's what you get.

Furthermore, the closing timing of the bypass valve 18 is set so that it operates according to the set value for each intake as described above, and the set value is corrected according to the acceleration state.
4 is fully opened or the intake pressure becomes atmospheric pressure, and the delay reference time may be controlled to be delayed in time depending on the acceleration state (also, the timing may be controlled to be delayed in time based on the engine speed). It is also possible to control the delay.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram of a supercharged engine according to an embodiment of the present invention, Fig. 2 is an explanatory diagram showing an example of control characteristics of a bypass valve, and Fig. 3 A, B, and C are illustrations of the throttle during acceleration. FIG. 4 is an explanatory diagram showing the other side of the control characteristics of the bypass valve. 1... Engine 6... Exhaust passage 7... Intake passage 8...
Supercharger 8a...Blower 8b...
... Turbine 13 ... Air flow meter 14 ... Throttle valve 16 ... Supercharging passage 17 ... Bypass passage 18 ... Bypass valve 19 ... Actuator 22 ... Control device Fig. 2

Claims (1)

[Claims] (1) The intake passage of the engine consists of a supercharging passage equipped with a turbo supercharger and a bypass passage that bypasses the turbo supercharger and merges downstream of it, and the bypass provided in the bypass passage at low speeds. In a supercharged engine that opens a valve and closes the bypass valve at high speed, an acceleration sensor that detects acceleration is provided, and when the acceleration exceeds a predetermined value, the closing timing of the bypass valve is determined. 1. An intake system for a supercharged engine, characterized in that it is provided with a control device that delays the time for a predetermined period of time.