JPS6145048B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an intake mechanism for a diesel engine.

In order to improve performance such as fuel efficiency and output of a direct injection diesel engine, it is necessary to improve the dispersion of the fuel injected into the combustion chamber to ensure sufficient mixing of air and fuel, and to improve the air intake into the combustion chamber. It is necessary to increase the volumetric efficiency by increasing the amount. Conventionally,
In order to improve the dispersion of fuel in the combustion chamber, the intake port of the combustion chamber is made into a helical shape, and a swirl is generated in the air flowing into the combustion chamber from the helical intake port, and the swirl improves the fuel distribution in the combustion chamber. It is being dispersed into However, the helical intake port has a large flow loss of intake air, which reduces the amount of air taken into the combustion chamber and reduces volumetric efficiency.Furthermore, when the engine is running at low speed, the swirl speed is slow and fuel is not dispersed. On the other hand, during high-speed operation, the swirl speed is too high, resulting in so-called over-swirl, which causes the fuel sprayed in the swirl to interfere with each other, making the fuel dispersion worse. Therefore, in order to solve this problem, an intake port for generating swirl and an intake port that does not generate swirl are provided in communication with each other in the combustion chamber, and intake valves that open and close at the same time are provided for both intake ports. An inflow control valve that restricts the flow path of one of the intake ports is installed at the branch on the starting end side of the port, and when the engine is running at low speed, the flow path of the intake port that does not generate swirl is restricted and the intake port is used to generate swirl. An intake mechanism has been invented that allows a large amount of air to flow in, and conversely, during high-speed operation, constricts the flow path of the intake port for generating swirl so that a large amount of air flows into the intake port that does not generate swirl. This intake mechanism is intended to reduce the usage rate of the swirl-generating intake port, where there is a lot of intake air flow loss, and to generate swirl at a speed that matches the engine operating conditions. It is still difficult to say that this is sufficient because it is not possible to set the opening and closing timing of the intake valves of each intake port to the appropriate timing for each intake port, and it is not possible to narrow down the flow paths of both intake ports at the same time. .

In view of this conventional situation, an object of the present invention is to generate a swirl that improves the dispersion of fuel injected into the combustion chamber, and to reduce flow loss of intake air and improve the volumetric efficiency of the combustion chamber. It is an object of the present invention to provide an air intake mechanism for a diesel engine that can be increased.

In order to achieve the above object, the present inventor first focused on the opening/closing timing of the intake valve provided at the intake port of the combustion chamber. Near top dead center or bottom dead center, where the intake valve is generally open or closed, the speed of intake air flowing into the combustion chamber from the intake port is slow;
Although it is not suitable for creating a swirl, the flow loss of intake air is small. Conversely, near the middle between top dead center and bottom dead center, the speed of intake air is high and there is a lot of flow loss of intake air, but swirl Because it is suitable for the occurrence of
The idea was that the intake valve of the intake port for generating strong swirls should open later and close earlier than the intake valves for the intake ports for generating weak swirls.

That is, the first invention provides a combustion chamber of a diesel engine with a helical intake port for generating a strong swirl and a tangential intake port for generating a weak swirl in communication with each other, and an intake valve provided on the helical intake port. A diesel engine characterized in that the tangential intake port is set to open later and close earlier than the intake valve provided in the tangential intake port, and the tangential intake port is provided with a throttle valve that operates according to the operating conditions of the diesel engine. It is an intake mechanism.

In the intake mechanism of the first invention, the intake valve provided at the helical intake port through which a large amount of air flows in during low-speed operation of the engine opens only during a period suitable for generating swirl. It is possible to generate sufficient swirl to improve the dispersion of fuel in the combustion chamber during low-speed operation, which would otherwise be insufficient, and the intake valve installed at the tangential intake port, where a large amount of air flows in during high-speed operation, Since it is opened during a period when intake air flow loss is small, the intake air flow loss can be reduced and the volumetric efficiency of the combustion chamber can be increased during high-speed operation where intake air flow loss was conventionally large.

Next, the present inventor proposed that if a throttle valve is provided not only in the tangential intake port but also in the helical intake port for generating strong swirl, the amount of air flowing into the helical intake port can be controlled to reduce overswirl during high-speed operation. I thought about how this could be prevented.

That is, in the second invention, a helical intake port and a tangential intake port are provided in communication with each other in a combustion chamber of a diesel engine, and the intake valve provided in the helical intake port opens later than the intake valve provided in the tangential intake port. This is an intake mechanism for a diesel engine, which is set to close quickly when the engine is closed, and is characterized in that both the tangential intake port and the helical intake port are provided with throttle valves that operate according to engine operating conditions.

In the intake mechanism of the second invention, as with the first invention, it is possible to generate sufficient swirl during low-speed operation, reduce flow loss of intake air during high-speed operation, and Time overswirl can be prevented.

Next, examples of the present invention will be described.

First Embodiment (See Figures 1 to 3) The diesel engine intake mechanism of this example has a helical intake port 2 and a tangential intake port 3 in each combustion chamber 1 of a direct injection 4-cylinder in-line diesel engine. The upstream ends of each helical intake port 2 and each tangential intake port 3 are connected to the surge tank 4 connected to the intake pipe 5, respectively, and the downstream end of each helical intake port 2 formed in a helical shape is connected to the combustion chamber. Intake valves 6 and 7 are installed at the downstream end of each tangential intake port 3 that is curved in the circumferential direction of the chamber 1, and as shown in the valve lift diagram of both intake valves 6 and 7 in FIG. The opening timing of the intake valve 6 of the intake port 2 is set later than that of the intake valve 7 of the tangential intake port 3, and is set in the range from top dead center to 50 degrees after top dead center, and the intake valve of the helical intake port The valve closing timing of each tangential intake port 3 is set earlier than that of the intake valve 7 of the tangential intake port and within a range of 40 degrees from bottom dead center to the bottom dead center.
A throttle valve 8 is installed in the middle of each throttle valve 8.
The valve shafts of the valves are connected to the output rotating shaft 11 of the valve opening control device 10 via the link mechanism 9, and a swirl of the optimum speed is formed based on the operating conditions such as the engine fuel injection amount, intake pressure and rotation speed. A central processing unit, so-called CPU 12, is provided which calculates the opening degree of the throttle valve 8 and instructs the valve opening degree control device 10 to determine the opening degree. Note that each combustion chamber 1 is provided with two exhaust ports 13 each having an exhaust valve in communication with each other.

In the intake mechanism of this example, when the engine is operated at low speed, the throttle valve 8 of each tangential intake port 3 that causes a weak intake swirl closes, and the throttle valve 8 of each helical intake port 2 that causes a strong intake swirl closes.
Intake air flows into each combustion chamber 1 from the helical intake port, and the intake valve 6 of each helical intake port opens late and closes early, opening at a period suitable for generating swirl.
Each helical intake port 2 generates strong swirl
Intake air flows into each combustion chamber 1 during a period when a strong swirl is generated, a strong swirl is generated in each combustion chamber 1, and the fuel sprayed into each combustion chamber 1 is well dispersed by the strong swirl. . When the engine is running at high speed, the throttle valve 8 of each tangential intake port is opened, and a large amount of intake air is transferred to each combustion chamber 1 from the tangential intake port 3, which has a small intake air flow loss, and from the helical intake port 2, which has a large intake air flow loss. A small amount of intake air flows in from each, and
Since the intake valve 7 of each tangential intake port opens early and closes late, opening during a period when the flow loss of the intake air is small, the flow loss of the intake air flowing into each combustion chamber 1 is small, and the volumetric efficiency of each combustion chamber 1 is good.

Second Embodiment (See Figures 4 and 5) Compared to the previous example, the intake mechanism of the diesel engine of this example has a throttle valve 14 and a throttle valve not only in each tangential intake port 3 but also in each helical intake port 2. A valve opening control device 15 is also provided. Other points are the same as those of the previous example, so the same parts are given the same reference numerals in FIGS. 4 and 5, and their explanation will be omitted.

In the intake mechanism of this example, when the engine is operated at high speed, the throttle valve 8 of each tangential intake port is fully opened, while the throttle valve 14 of each helical intake port is slightly closed, causing a strong intake swirl in each helical intake. The amount of intake air flowing into each combustion chamber 1 from the port 2 is reduced, and overswirl is prevented from occurring in each combustion chamber 1.

[Brief explanation of the drawing]

Fig. 1 is a plan view of the intake mechanism of a diesel engine according to the first embodiment of the present invention, Fig. 2 is a partial perspective view of the same intake mechanism, and Fig. 3 is a valve lift diagram of both intake valves of the same intake mechanism. FIG. 4 is a plan view of the intake mechanism of the diesel engine of the second embodiment, and FIG. 5 is a partial perspective view of the intake mechanism. 1: Combustion chamber, 2: Helical intake port, 3: Tangential intake port, 6: Intake valve, 7: Intake valve, 8: Throttle valve, 14: Throttle valve.

Claims (1)

[Scope of Claims] 1. A helical intake port and a tangential intake port are provided in communication with each other in the combustion chamber of a diesel engine, and the opening timing of the intake valve provided in the helical intake port is determined by the opening timing of the intake valve provided in the tangential intake port. The closing timing of the intake valve of the helical intake port is set later than that and earlier than that of the intake valve of the tangential intake port, and the tangential intake port is provided with a throttle valve that operates according to the operating conditions of the diesel engine. A diesel engine intake mechanism featuring: 2. A helical intake port and a tangential intake port are provided in communication with each other in the combustion chamber of a diesel engine, and the opening timing of the intake valve provided in the helical intake port is later than that of the intake valve provided in the tangential intake port, and The closing timing of the intake valve of the helical intake port is set earlier than that of the intake valve of the tangential intake port, and the tangential intake port and the helical intake port are each equipped with a throttle valve that operates according to the operating conditions of the diesel engine. A distinctive feature of the diesel engine intake mechanism.