JPH03182626A - Intake device of engine with mechanical type supercharger - Google Patents

Abstract

PURPOSE:To secure combustion stability by stopping driving of a mechanical type supercharger at the time of low load of idling and the like, and adjusting a bypass passage at a specified throttle opening. CONSTITUTION:At the time of low load of idling and the like, a bypass opening/ closing valve 16 is opened, and a throttle condition is secured by setting a bypass throttle valve 20 at a specified opening. A mechanical type supercharger 6 is set at non-driving condition when a clutch 11 is set OFF. Intake air is supplied to cylinders 2 by natural charge, and a bypass passage 14 is contracted by the throttle valve 20. Resistance of intake air which passes through the bypass passage 14 and resistance of intake air which passes through an intake passage 4 during rotation of a supercharger 6, become substantially the same. The intake air is flowed from up and down sides of collection intake passages 4m, 4n with respect to cylinders 2, and even if spitting toward ventilation passages 4a-4f of fuel at the cylinders 2 occurs, distribution is improved since the air is taken into by being taken into the cylinders 2 equally. An air-fuel ratio is equalized and combustion stability is secured.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an intake system for an engine equipped with a mechanical supercharger driven by the output of the engine.

(Prior art) Conventionally, in engines equipped with a mechanical supercharger, the drive of the mechanical supercharger is controlled by engaging and disengaging a clutch, and a bypass passage is provided to bypass the mechanical supercharger. For example, Japanese Patent Laid-Open No. 81-19935 discloses a technique in which the clutch is disengaged to stop driving the mechanical supercharger at the time of load, and the bypass passage is opened to supply intake air through the bypass passage. As seen, it is known.

The above technology improves fuel efficiency at low loads, such as when idling, when the engine output is small and the drive loss ratio of the mechanical supercharger increases. The mechanical supercharger, whose drive is stopped, acts as a resistance to natural intake and supplies intake air to the C engine through natural intake, which reduces charging efficiency. It opens.

(Problem to be Solved by the Invention) However, when the drive of the mechanical supercharger is stopped and the bypass passage is opened during low load, the air-fuel ratio becomes uneven between the cylinders, resulting in uneven engine rotation. There is a risk of stability.

That is, the intake passage that has passed through the bypass passage is connected to each cylinder in order from the upstream side to the downstream side, and the intake air always flows from one side of the cylinder arrangement to the other, and in particular, the intake passage is connected to each cylinder by branching. If the length of the independent intake passage is short, the -
The fuel that has previously flowed into the combustion chamber is blown back. The fuel blown back into the intake passage moves downstream according to the flow of the intake air and flows into the cylinders on the downstream side.As a result, the air-fuel ratio in the cylinders on the upstream side becomes thinner. On the other hand, a phenomenon occurs in which the air-fuel ratio becomes richer in the cylinders on the downstream side.

Combustion stability decreases due to the above-mentioned variation in the air-fuel ratio, and this phenomenon occurs particularly in the low-speed and light-load range.Also, the greater the overlap and the later the intake valve closing timing, the greater the amount of blowback, which increases the air-fuel ratio. The difference becomes large and noticeable.

Therefore, in view of the above circumstances, the present invention is a mechanical supercharger that stops driving the mechanical supercharger and opens a bypass passage when the load is low, thereby equalizing the air-fuel ratio between the cylinders. The object of the present invention is to provide an intake system for a fed engine.

(Means for Solving the Problems) In order to achieve the above object, an intake system for a mechanically supercharged engine according to the present invention is configured such that each cylinder is sequentially arranged from one side to the other in the cylinder arrangement direction from the upstream side to the downstream side. In the connected intake passage,
Equipped with a mechanical supercharger driven by engine output via a clutch, a bypass passage that bypasses the mechanical supercharger and supplies intake air, and a bypass opening/closing means for opening and closing the bypass passage, it has a low load. At the same time, the clutch is disengaged to put the mechanical supercharger in a non-driving state, and the bypass passage valve is opened to open the bypass passage, and the downstream end of the bypass passage is opened. The bypass throttle means is connected to the downstream side of the intake passage in the cylinder arrangement direction and throttles the bypass passage by a predetermined opening when a clutch for the mechanical supercharger is not engaged.

(Function) In the above-mentioned intake system, under high load conditions, the clutch is engaged to drive the mechanical supercharger and close the bypass passage, allowing air pressurized by the mechanical supercharger to flow into each cylinder. In this high-load state, there is little blowback of fuel into the intake passage, and even if intake is performed sequentially from the upstream side to the downstream side, the difference in air-fuel ratio between cylinders is small. On the other hand, in a low load region such as when idling, the clutch is disengaged to stop driving the mechanical supercharger, and at the same time the bypass passage is opened by the bypass passage opening/closing means, and the bypass passage is throttled to a predetermined value by the bypass throttle means. Adjust the opening.

As a result, in the intake passage for each cylinder, the resistance of the mechanical supercharger on the upstream side and the throttle resistance of the bypass passage on the downstream side become negative, and approximately the same amount of intake air is supplied from the upstream and downstream sides. Even if fuel is blown back, it is evenly drawn into each cylinder, which prevents air-fuel ratio differences between the cylinders and ensures combustion stability. Furthermore, in the above-mentioned low load state, the mechanical supercharger is placed in an idling state by narrowing the bypass passage, and the torque shock when the clutch is engaged from this state is alleviated.

(Example) The present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a mechanical supercharged engine (V
2 shows a schematic configuration of an intake system for a type 6-cylinder engine.

3 each in banks la and lb on both sides of engine body 1
Two cylinders 2 are installed, and short independent intake passages 4a to 4f are each independently connected to an intake boat (not shown) having a capacity of 2. Also, each bank la, lb
, the upstream ends of the independent intake passages 4a to 4f of each cylinder 2 are connected to collective intake passages 4m and 4n, and the collective intake passage 4m.

4n is connected to the downstream side, and the collective intake passages 4m and 4n on both sides are gathered on the upstream side, and the upstream intake passage 4 is equipped with an intercooler 5 and a mechanical supercharger 6 (roots type air pump).
, a throttle valve 7, and an air flow meter 8 are arranged in this order on the upstream side.

In the intake passage 4, a collective intake passage 4m passes through a mechanical supercharger 6 and an intercooler 5.

4n is connected to each cylinder 2 of banks la and lb in order from one side to the other in the cylinder arrangement direction, and is configured to supply intake air in order from the upstream side to the downstream side.

The mechanical supercharger 6 is driven by engine output transmitted through a power transmission system (not shown). A clutch 11 (electromagnetic clutch, etc.) is installed in the power transmission system, and a control signal is output from a controller 12 to the clutch 11, and a control signal is output from a controller 12 to the clutch 11.
The mechanical supercharger 6 is switched between a driven state and a non-driven state depending on whether the fastened state is on or off.

On the other hand, a bypass passage 14 that bypasses the mechanical supercharger 6 is connected. The bypass passage 14 has an upstream end connected to an intake passage downstream of the throttle valve 7, and a downstream end connected to a downstream communication portion of the collective intake passage 4m+4n.

A bypass opening/closing means 15 including a bypass opening/closing valve 16 for opening/closing the bypass passage 14 is installed at the downstream end of the bypass passage 14 . Moreover, a bypass throttle means 19 is interposed in the bypass passage 14, which is a bypass throttle valve 20 that throttles the bypass passage 14 to a predetermined opening degree.

The bypass opening/closing valve 16 of the bypass opening/closing means 15 is opened and closed by a diaphragm actuator 17,
A spring 17 that biases the negative pressure chamber 17a in the valve closing direction
b is compressed, and this negative pressure chamber 17a has an introduction passage 1.
．． Throttle valve 7 upstream of mechanical supercharger 6 via 7 c
Downstream suction pressure is introduced.

The opening degree control of the bypass opening/closing valve 16 by the bypass opening/closing means 15 is as shown by the solid line in FIG. 3(A).
Due to the action of the diaphragm actuator 17, it opens in a low load state where the intake negative pressure increases, and gradually closes to a fully closed state due to the supercharging pressure that increases as the load increases.

Moreover, the bypass throttle valve 20 of one of the bypass throttle means
is opened and closed by a solenoid actuator 21, and a control signal is output from the controller 12 to the solenoid actuator 21 to adjust its aperture opening degree.

The opening degree of the bypass throttle valve 20 is controlled by this single bypass throttle means, as shown by the broken line in FIG. While the bypass passage 14 is throttled, the bypass opening/closing valve 16 is fully opened before it starts to close in response to an increase in load.

Furthermore, a valve timing change device 23 is installed which changes the overlap with the intake valve by changing the closing timing of the exhaust valve of each cylinder 2, and its actuator 24 is operated by a control signal outputted from the controller 12. is controlled.

As shown in FIG. 4, the valve timing is such that the intake valve opens at an opening timing 10 before top dead center TDC, and closes at a closing timing IC after bottom dead center BDC. On the other hand, the exhaust valve is shown by the solid line EX
In the case of a low-load application shown in , it opens at an early opening timing EO before bottom dead center BDC and closes at an early closing timing EC after top dead center TDC, and the overlap with the intake valve at this time is θ.
1 is set to be as small as about 10°. In addition, in the case of a high-load exhaust valve indicated by the broken line EX', the bottom dead center BD
It opens at a late opening timing EO' before Ca\ and closes at a late closing timing EC' after top dead center TDC, and the overlap θ2 with the intake valve at this time is set at a maximum of about 30 degrees or more. has been done.

The closing timing IC of the intake valve is 70 minutes from the bottom dead center BDC.
It is set to close late at 6 to 100 degrees, and together with the cooling of the supercharged air by the intercooler 5, it lowers the air-fuel mixture temperature in the combustion chamber, suppresses the occurrence of knocking, and sets a high compression ratio. I have to.

Further, the controller 12 controls the drive of the mechanical supercharger 6 by the clutch 11, and controls the solenoid actuator 2.
1 controls the opening of the bypass throttle valve 20 and the actuator 23 controls the valve timing changing device 24, respectively.The controller 12 receives an intake air amount signal Q from the air flow meter 8 and an engine rotation speed signal Ne. Each is manually operated, and the second
Control is performed based on a map of engine speed and load (Q/Ne) as shown in the figure.

That is, line a in FIG. 2 indicates the operating range of the clutch 11, and the high-speed, high-resistance range I outside this line a is the range where the clutch 11 is connected to drive the mechanical supercharger 6, and the inner In the low load region (2), the clutch 11 is not engaged and the mechanical supercharger 6 is not driven.

Line b, which is on the lower speed and lower load side than line a, indicates the operating area of the bypass throttle valve 20, and the inner area (■) of line b is the area where the bypass throttle valve 20 is closed and throttled to a predetermined opening degree, and the outer area This region is the fully open region of the bypass throttle valve 20. Furthermore, a line C on the lower speed and lower load side than the above line b indicates an overlap change area of the valve timing change device 24, and an inner area (2) of line C is an area where the exhaust valve close timing is advanced to reduce the overlap, and an outer line C is an area where the overlap is reduced by advancing the exhaust valve closing timing. This is the region where the exhaust valve closing timing is delayed and the overlap is increased.

Next, the operation of the above embodiment will be explained. First, when the load is low, the bypass on-off valve 16 opens as shown in FIG. 3(A), the bypass throttle valve 20 closes to a predetermined opening degree and is in the throttle state, and the mechanical The type supercharger 6 is in a non-driving state with the clutch 11 OFF, and the
), the overlap is small. At this time, intake air is supplied to each cylinder 2 by natural intake, but the bypass passage 14 is throttled by the bypass throttle valve 20, and the resistance of the intake air passing through the bypass passage 14 and the mechanical supercharger 6 are reduced. The resistance of the intake air passing through the intake passage 4 while idling becomes a road gap, and the intake air flows into each cylinder 2 from both the upstream and downstream sides of each collective intake passage 4m and 4n, and Even if fuel blows back into the intake passages 43 to 4f, it is evenly sucked into each cylinder 2, improving distribution, and ensuring combustion stability by equalizing the air-fuel ratio.

Note that during sudden acceleration from a low load state, the intake resistance in both the intake passage 4 and the bypass passage 14 is large, causing a delay in acceleration, but in this case, the bypass throttle valve 20 is opened to promote an increase in the amount of intake air. You can do it like this.

On the other hand, when the load increases, after increasing the overlap, the bypass throttle valve 20 is opened to reduce the intake resistance, and then the clutch 11 is engaged to start driving the mechanical supercharger 6. As a result, the bypass on-off valve 16 gradually closes as the supercharging pressure increases, increasing the supercharging effect.

When a high load condition occurs, the resonance effect of the intake air by the short independent intake passages 4a to 4f creates positive pressure in the intake boat part during the overlap period, thereby increasing the scavenging action, reducing residual exhaust gas, and suppressing mucking. The supercharging pressure by the mechanical supercharger 6 can be set high, and high output can be obtained.

In the above embodiment, the bypass opening/closing means 15 and one bypass throttling means are constructed by separately interposing a valve in the bypass passage 14, but by using a common valve mechanism for both, the functions of both means can be improved. It may be possible to perform control with the following.

Further, as the mechanical supercharger 6, in addition to the Roots type, there are vane type, screw type, etc., but the present invention is a mechanical supercharger of a type that does not involve internal compression, or a type that is equipped with a compression control mechanism. Effective for mechanical superchargers.

(Effects of the Invention) According to the present invention as described above, a mechanical supercharger that is driven during high load through a clutch is provided in the intake passage, and the downstream end of the bypass passage that bypasses the mechanical supercharger is provided in the intake passage. a bypass opening/closing means that connects the bypass passage to an intake passage on the downstream side in the cylinder arrangement direction, and opens the bypass passage at low load; and a bypass throttle means that narrows the bypass passage to a predetermined opening when the mechanical supercharger is not driven. As a result, in low load ranges such as when idling, the drive of the mechanical supercharger is stopped and at the same time the bypass passage is adjusted to a predetermined throttle opening, thereby reducing the resistance of the upstream mechanical supercharger and the downstream The throttle resistance of the bypass passage on the side acts as a gap, and approximately the same amount of intake air is supplied from the upstream and downstream sides, and even if there is fuel blowback, it is evenly sucked into each cylinder, and the air-fuel ratio between the cylinders is maintained. This can prevent differences from occurring and ensure combustion stability.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram of an intake system of a mechanically supercharged engine according to an embodiment of the present invention, Fig. 2 is a characteristic diagram showing the control range for operating conditions, and Fig. 3 is a change characteristic in response to an increase in load. FIG. 4 is a pulp timing diagram showing changes in the overlap of intake and exhaust valves. 1...Engine body, 2...Cylinder, 4
a~4f...Independent intake passage, 4m, 4n...
...collective intake passage, 5...intercooler,
6...Mechanical supercharger, 7...Throttle valve, 1]...Clutch, 12...Controller, 14...Bypass al15...
... Bypass opening/closing means, 16... Bypass opening/closing valve, one... Bypass throttling means, 20...
...Bypass throttle valve, 23... Valve timing change device. #? -Heart

Claims (1)

[Claims] (1) A mechanical supercharger, which is driven by engine output via a clutch, is connected to an intake passage connected to each cylinder in order from one side to the other in the cylinder arrangement direction, from upstream side to downstream side, and the mechanical supercharger It is equipped with a bypass passage that bypasses the supercharger and supplies intake air, and a bypass opening/closing means that opens and closes the bypass passage, and operates the clutch in a disengaged state at low load to put the mechanical supercharger in a non-driving state. and an intake system for a mechanically supercharged engine which opens a bypass passage by opening a bypass control valve, the downstream end of the bypass passage being positioned downstream of the intake passage in the cylinder arrangement direction. 1. An air intake system for an engine with a mechanical supercharger, characterized in that the air intake device is equipped with a bypass throttle means for narrowing a bypass passage to a predetermined opening degree when a clutch for the mechanical supercharger is not engaged.