JPH0727401Y2 - Engine intake system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an engine intake device that supplies intake air to an engine combustion chamber together with EGR gas, blow-by gas, etc. introduced therein.

[Prior Art] The blow-by gas inside the crankcase is one of the causes of air pollution when it leaks, and therefore, in order to prevent this, the blow-by gas is guided to an intake device. Further, when the combustion temperature in the combustion chamber becomes high, the amount of nitric oxide contained in the exhaust gas increases, which also causes air pollution. Therefore, in order to lower the combustion temperature, a part of the exhaust gas as the EGR gas is similarly guided to the intake device.

By the way, if these blow-by gas and EGR gas are not evenly distributed and supplied to multiple cylinders, the combustion state of each cylinder will vary, causing abnormal wear of the piston ring, liner, and valve, and May cause significant damage.

On the other hand, the blow-by gas or EGR gas contains water vapor, oil mist, or the like. These water vapor, oil mist and the like are guided to the intake device together with the blow-by gas and the EGR gas, so that they are condensed in the intake device to become water drops, oil drops and the like. Further, in the intake device, there is also fuel and the like that has flowed back without being vaporized after being injected from the fuel injection valve. If a large amount of these water droplets, oil droplets, backflow fuel, etc. accumulate in the intake device, they will be sucked into the combustion chamber due to a temporary increase in negative pressure in the intake device, etc., causing deterioration of combustibility such as misfire, and performance and There is a risk of reducing reliability.

Therefore, in the conventional engine intake system, EGR gas and the like are introduced into the surge tank located at a position higher than the intake port, as disclosed in Japanese Utility Model Laid-Open No. 60-23240. It was That is, the intake air is introduced at a position on the upstream side of the position where the intake air is divided toward each cylinder, and at a position where there is no climb gradient in the intake passage up to the intake port, EGR gas, etc. was evenly distributed to each cylinder, and water, oil, backflow fuel, etc. could always move to the combustion chamber by their own weight.

[Problems to be solved by the device]

However, in the configuration in which the EGR gas or the like is guided into the surge tank as described above, if the surge tank is provided at a position lower than the intake port, moisture and oil, backflow fuel, etc. will not move into the combustion chamber due to its own weight. Accumulates in the surge tank or intake passage. Therefore, since the surge tank cannot be provided at a position lower than the intake port, there is a problem that layout in the engine room and external conditions such as height and shape of the bonnet are largely restricted.

Therefore, by using a distribution pipe, EGR gas, etc. is introduced into each cylinder just before the intake port, without impairing the distributability of EGR gas, etc., and regardless of the position of the surge tank. It is also possible to ensure that the oil, oil, backflow fuel, and the like can move into the combustion chamber by their own weight. However, in order to evenly distribute the EGR gas by the distribution pipe, it is necessary to use a distribution pipe having a complicated structure, which leads to an increase in manufacturing cost and a complicated layout in the engine room. .

It is also possible to introduce water, oil, backflow fuel, etc. into the crankcase located at a position lower than the intake device, but in this case, deterioration due to dilution of oil in the crankcase is caused. It will be.

[Means for Solving the Problems]

In order to solve the above problems, the EGR passage structure of the engine according to the present invention is provided with a low-load intake port that constantly allows intake air to flow, and an intake flow is blocked when the load is low, while the intake air flows only when the load is high. In an intake system for an engine provided with a high load intake port through which air flows, a portion of the intake passage upstream of each of the intake ports near a position where the height of the bottom is partially lowest and It is characterized in that a communication passage communicating with the intake port is provided.

[Action]

With the above configuration, in the vicinity of the position where the height of the bottom part is partially the lowest in the intake passage, the intake port for low load where the negative pressure increases due to high-speed intake air flow at low load through the communication conduit. It is in communication. Therefore, even if water, oil, backflow fuel, etc. collect in the intake passage,
Each time the engine load becomes low, it is reliably sucked out to the low load intake port and does not accumulate in large quantities.

Therefore, it is not necessary to allow water, oil, backflow fuel, etc. to move into the combustion chamber by its own weight.
It is possible to greatly reduce the geometrical and layout restrictions such as the gradient of the intake passage and the height with respect to the intake port.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

In the cylinder head 12 that constitutes the engine body 11, for example, as shown in FIG. 1 for one cylinder, an intake port 13 including a low load intake port 13a and a high load intake port 13b, and an exhaust port 14 are provided. Has been formed. The opening cross-sectional area of the low load intake port 13a is set to be smaller than that of the high load intake port 13b. The intake port 13 and the exhaust port 14 are connected to the combustion chamber by the intake valve 15 and the exhaust valve 16, respectively.
It is designed to communicate with or be disconnected from 17.

An upper portion of the cylinder head 12 is covered with a cylinder head cover 18 to form a space 19 communicating with the inside of a crankcase (not shown). An oil separator 20 is provided on the lower surface of the cylinder head cover 18.

On the exhaust port 14 side of the cylinder head 12, the exhaust port 14
An exhaust manifold 21 that communicates with the is attached.
On the other hand, on the intake port 13 side of the cylinder head 12, a low load passage 22a communicating with the low load intake port 13a and a high load passage 22b communicating with the high load intake port 13b are formed. The intake manifold 22 is installed.

In the high load passage 22b of the intake manifold 22, a rotatable shutter valve 23 is provided. This shutter valve 23 is closed when the load is low and the intake port 13 for high load is closed.
Block the flow of intake air to b and allow the intake air to flow only to the low load intake port 13a, while opening it at high load to allow the intake air to flow to the high load intake port 13b together with the low load intake port 13b. It has become.

The exhaust manifold 21 and the intake manifold 22 are
It is installed for each cylinder. That is, for example, in the case of a four-cylinder engine body 11, four intake manifolds 22 ... Are provided as shown in FIG.

A flange portion 24 is formed on the cylinder head 12 side of the intake manifold 22 ...
It is attached to the cylinder head 12 by 25 ...
Further, the sides of the intake manifolds 22 ... That are opposite to the cylinder head 12 each have a downwardly curved shape.

Each of the four intake manifolds 22 has an inlet-side opening 33 formed in a side portion thereof and is integrally formed with a surge tank 31 to which an air cleaner, a throttle valve and the like (not shown) are connected. That is, four inlet openings 32 for intake air are formed in the surge tank 31, and the intake manifolds 22 connected to the outlet openings 32 are connected to each other via the surge tank 13. Has become.

At the upper part of the surge tank 31, a communication passage 14 communicating with the space 19 above the cylinder head 12 via the oil separator 20 is connected, and the space 19 above the cylinder head 12 and
Blow-by gas in a crankcase (not shown) is introduced. A communication 42, which communicates with the exhaust manifold 21, is connected to the upper portion of the surge tank 31 so that a part of the exhaust gas inside the exhaust manifold 21 can be removed from the EGR.
It is being introduced as gas.

A communication passage 43 is connected to the lower portion of the surge tank 31, and the vicinity of the position where the height of the bottom portion of the intake passage is partially lowest, that is, between the inlet side opening 33 of the surge tank 31 and the intake port 13, for example. The low-load intake port 13a of the cylinder head 12 is in communication with the lowest part of the bottom wall surface 34 of the surge tank 31, which is near the lowest height of the bottom part.

The intake surge tank 31, the intake manifold 22, and the intake port 13 constitute an intake device for the engine.

In the above configuration, the intake air that has been dust-removed by the air cleaner and sent through the throttle valve or the like is at the inlet opening 33
Flows into the surge tank 31. The intake air that has flowed into the surge tank 31 is mixed with the blow-by gas sent from the space 19 above the cylinder head 12 via the oil separator 20 and the EGR gas sent from the exhaust manifold 21, and then split into each intake manifold 22. To do.

When the engine load is high, the intake valve flowing through the intake manifold 22 has the shutter valve 23 provided in the high load passage 22b open, so that the intake port 13b for high load and the low load It flows through both the intake port 13a and the intake port 13a and is sent to the combustion chamber 17 to secure the intake charge amount.

On the other hand, when the load of the engine is low, the shutter valve 23 is closed. So the intake manifold
All the intake air flowing through 22 is sent to the combustion chamber 17 via the low load intake port 13a. In this case, the opening cross-sectional area of the low-load intake port 13a is set to be smaller than the opening cross-sectional area of the high-load intake port 13b.
Even if the amount of intake air is small, the flow velocity does not drop, swirl is generated, and fuel flow is promoted.

Further, since the intake manifold 22 has a curved shape, the intake pipe length is secured while the entire intake device is compact in both the height direction and the width direction. Therefore, a high intake efficiency is obtained, especially when the engine is at low speed.

By the way, the blow-by gas or EGR gas introduced into the surge tank 31 contains water vapor, oil mist, or the like. Regarding the blow-by gas, for example, an oil separator 20 is provided, but the slightly sulfided oil still cannot be completely separated and is mixed in the blow-by gas. These water vapor, oil mist and the like are guided to the intake device together with the blow-by gas and the EGR gas, so that they are condensed in the intake device to become water drops, oil drops and the like. Also,
In the intake device, there is also fuel and the like that has flowed back without being vaporized after being injected from the fuel injection valve. These water and oil drops,
The backflow fuel and the like collect near the bottom of the bottom wall surface 34 of the surge tank 31.

On the other hand, the negative pressure inside the low load intake port 13a increases when the engine load is low because the intake air flows through the low load intake port 13a at a high speed as described above. Therefore, between the negative pressure inside the low load intake port 13a and the pressure inside the surge tank 31, according to Bernoulli's theorem,
The flow velocity and pressure of the intake air inside the surge tank 31 are v ₁ ,
P _1, the flow rate of the low-load intake port 13a inside the air intake, and pressure v _2, P _2, when the density of the intake air and _{ρ, P 1 -P 2 = ρ} (v 2 2 -v 1 2) / 2 A differential pressure of occurs.

The flow velocity v ₁ of the intake air inside the surge tank 31 and the flow velocity v ₂ of the intake air inside the low load intake port 13a are, for example, measured on an actual engine, v ₁ = 1.6 m / sec,
v ₂ = 55.9 m / sec. In this case, the differential pressure becomes _{P 1 -P 2 = 1873N / m} 2 = 14mmHg = 0.191mH 2 O.

Therefore, water drops and the like in the surge tank 31 are reliably sucked out through the communication passage 43 and sent to the combustion chamber 17. Therefore, a large amount of water or the like introduced along with the blow-by gas or EGR gas does not accumulate inside the surge tank 31.

[Effect of device]

As described above, the intake device for an engine according to the present invention has a low-load intake port that constantly allows intake air to flow, and a high-load intake port that interrupts intake air flow when the load is low, while allowing intake air to flow only when the load is high. In an intake device for an engine equipped with an intake port for a vehicle, the vicinity of a position where the height of the bottom is partly lowest in the intake passage upstream of the intake ports and the intake port for a low load are communicated with each other. The communication passage is provided.

As a result, even if water, oil, and backflow fuel, etc., are not allowed to move into the combustion chamber by their own weight, water, etc. can be reliably sucked out to the low-load intake port and accumulated in large quantities inside the intake passage. Since there is no such restriction, it is possible to greatly reduce the geometrical and layout restrictions such as the inclination of the intake passage and the height to the intake port. Therefore, the layout in the engine room, the height and the shape of the bonnet, etc. This has the effect of increasing the degree of freedom with respect to the appearance conditions and the like.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 and FIG. 2 show an embodiment of the present invention. FIG. 1 is a sectional side view showing the construction of an engine, and FIG.
The figure is a view on arrow A in FIG. 11 is the engine body, 13 is the intake port (intake device), 13a
Is a low load intake port, 13b is a high load intake port, 22
Is an intake manifold (intake device), 31 is a surge tank (intake device), and 34 is a bottom wall surface.

Continuation of front page (72) Inventor Taishi Tokushige 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Co., Ltd. (56) Reference JP-A-63-154813 (JP, A) JP-A-61-171872 (JP) , A) Jitsuko Sho 60-42217 (JP, Y2)

Claims (1)

[Scope of utility model registration request] 1. An intake air for an engine provided with an intake port for low load, which always allows intake air to flow, and an intake port for high load, which interrupts the flow of intake air when the load is low, while allowing intake air to flow only when the load is high. In the device, a communication passage that connects the vicinity of a position where the height of the bottom is partially lowest in the intake passages upstream of the respective intake ports and the low-load intake port is provided. Characteristic engine intake device.