JPH0573899B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an intake system for a four-stroke engine, and particularly to the structure of its intake passage.

As this type of intake device, two
An intake passage is connected to each intake port, and a second throttle valve is connected to one of these two intake passages in addition to a first throttle valve that is controlled to open and close by throttle operation.
It is known that a throttle valve is provided and the second throttle valve is opened only during high negative operation.
By the way, in this device, the intake passages are communicated between the intake port and the second throttle valve, but during low-medium load operation, that is, when the second throttle valve is closed, the intake air flows only from one side of the intake passage. Therefore, even if the intake passage is communicated between the second throttle valve and the intake port as described above, there will be unevenness in the intake flow, which causes the intake air to be supplied to the combustion chamber from the two intake ports. It became difficult to do so, and there was room for improvement in terms of intake air filling efficiency.

The present invention was made based on the above circumstances, and when the second throttle valve is closed, the intake air can be evenly distributed toward the plurality of intake ports, and the flow velocity of the intake air can be sufficiently increased to improve combustion. The filling efficiency into the chamber can be increased, and the dead space between the intake passages can be used to form a wide passage, and this passage can be used as a flow passage for blow-by gas and oil. The purpose of the present invention is to provide an intake system for a four-stroke engine that can also reduce the weight of the head.

In order to achieve the above object, in the present invention,
A cylinder block consisting of multiple cylinders arranged side by side,
The cylinder head includes a plurality of combustion chambers connected to the cylinders, and a cylinder head having a plurality of intake ports opened to each of the combustion chambers, and the cylinder head includes:
A plurality of intake passages connected to the intake ports of each combustion chamber are provided, a common first throttle valve is provided upstream of these intake passages, and the first throttle valve is provided in some of these intake passages. The present invention is based on a four-cycle engine in which a second throttle valve is provided downstream of the engine, and the intake passages communicate with each other between the intake port and the second throttle valve for each combustion chamber.

A constricted portion is provided in the mutual communication portion of the intake passage, the passage area of which decreases as it progresses toward the intake port, and widens from the middle, and is sandwiched between adjacent mutual communication portions of the cylinder head. The cylinder is characterized in that a passage extending in the axial direction of the cylinder is formed in the closed portion.

The present invention will be explained below based on drawings in which the present invention is applied to a four-stroke, four-cylinder engine.

In the figure, 1 is a cylinder block, 2 is a cylinder head, and 3 is a piston. The cylinder head 2 has four cylinders 4 arranged in parallel inside the cylinder block 1.
Combustion chambers 5 are formed correspondingly. As shown in FIG. 2, each combustion chamber 5 is opened with two intake ports 6, 6 and two exhaust ports 7, 7. are intake valves 8, 8 and exhaust valve 9,
9 opens and closes at predetermined timing. In addition,
In FIG. 1, numeral 10 is an intake camshaft, and 11 is an exhaust camshaft.
It is located within 3.

A first intake passage 14 and a second intake passage 15 are connected to the intake ports 6, 6 for each cylinder 4, and the upstream ends of these two intake passages 14, 15 are connected to an intake chamber 16. There is. The intake chamber 16 is communicated with the atmosphere via an air cleaner and an air flow meter (not shown), and a pair of first throttle valves 1 are provided at the upstream end of the intake chamber 16.
7 and 18 are provided. First throttle valve 17,1
Reference numeral 8 is a valve that is opened and closed in conjunction with throttle operation, and when the throttle is in an idling state and reaches a certain opening, only one first throttle valve 17 operates to open and close, and when the throttle is opened wide beyond a certain opening. The other first throttle valve 18 is also opened.

Further, a second throttle valve 19 is provided in the first intake passage 14 connected to each cylinder 4 , located downstream of the first throttle valves 17 and 18 . The second throttle valves 19 are interlocked with each other, and are opened only during high-load operation of the engine by, for example, an actuator (not shown) that is operated depending on the magnitude of the intake air flow rate. This first intake passage 14
and the second intake passage 15 are communicated with each other by a communication passage 20 between the intake ports 16, 6 and the second throttle valve 19. The passageway has a long hole-like cross-sectional shape. The inner wall surface of the communication portion 21 has a constricted portion 22 whose passage area is continuously reduced as it advances toward the intake ports 6, 6, and which expands in a smooth curve from the middle. A fuel injection valve 23 is provided in this communication portion 21 so as to face the throttle portion 22 . Furthermore, the wall thickness between each communication portion 21 of the cylinder head 2 is increased by the constricted portion 22, and this thick portion 24 has a cooling water passage 26 connected to the water jacket 25 of the cylinder head 2 and a cooling water passage (not shown). A passage 27 is formed that connects the crank chamber and the camshaft chamber 13 and extends in the axial direction of the cylinder 4. This passage 27 is an oil passage that lubricates the suction and exhaust camshafts 10, 11, etc., and returns the oil accumulated in the camshaft chamber 13 to the oil pan at the bottom of the crank chamber. Therefore, the oil flowing from the camshaft chamber 13 to the crank chamber and the blowby gas rising from the crank chamber to the camshaft chamber 13 pass through a common passage 27. It's becoming like that.

Next, the operation of the above configuration will be explained.

Second throttle valve 19 for low and medium load operation of the engine
is closed, all of the intake air whose flow rate is controlled by the first throttle valve 17 passes through the second intake passage 15 and reaches the communication section 20, and is guided from this communication section 20 to the intake ports 6, 6. At this time, since a constriction part 22 is provided on the inner wall surface of the communication part 21 to reduce the passage area, the flow velocity of the intake air from the second intake passage 15 is increased and the flow direction is indicated by the arrow in FIG. As shown in FIG. As a result, the intake air is evenly distributed to the two intake ports 6, 6, and when the intake valves 8, 8 are opened, it is drawn into the combustion chamber 5 from these two intake ports 6, 6. The intake air filling efficiency is significantly improved, resulting in high output.

On the other hand, when the first throttle valves 17 and 18 are opened wide and the engine shifts to high-load operation, the intake flow rate increases further, so the second throttle valve 19 is opened. Therefore, the intake air flows into the first intake passage 14 in addition to the second intake passage 15, and the area of the passage increases.
Since the flow velocity is increased by passing through the constriction portion 22, more intake air can be guided to the intake ports 6, 6, contributing to an increase in output.

Further, since the fuel injection valve 23 is provided in the communication portion 21 toward the throttle portion 22, the fuel is injected into the portion where the intake air flow velocity is high, and the fuel and intake air are mixed well.

Further, according to the above configuration, the wall thickness between adjacent communication portions 21 in the cylinder head 2 increases by the amount that the throttle portion 22 is provided.
The passage area of the passage 27 passing through 4 can be expanded. That is, when oil and blow-by gas flow in opposite directions through a single passage 27, if the passage area is small, this passage 27 may be substantially blocked by the oil, or the oil may blow up due to the pressure of the blow-by gas. It may happen. However,
By providing the throttle portion 22 as described above, the passage area can be expanded by using the dead space created inside the cylinder head 2, so that the passage 27 is not blocked by oil or the oil is caused by blow-by gas. Both oil and blow-by gas can flow smoothly through the common passage 27 without the risk of being blown up.

Moreover, the presence of the passage 27 makes it possible for the thickened portion 24 to
The excess meat of cylinder head 2 is removed.
This will also effectively contribute to weight reduction.

Note that the number of intake ports and intake passages is not limited to two, but can be similarly implemented with three, for example.

According to the present invention described in detail above, when the second throttle valve is fully closed, the flow velocity of the intake air from the intake passage in the open state is increased when passing through the throttle part, and
Since the flow direction is shifted toward the center of the communication portion, the intake air is evenly distributed from here to the plurality of intake ports. Therefore, since the intake air is drawn into the combustion chamber through all the intake ports, the filling efficiency of the intake air is significantly improved, and high output can be obtained.

Moreover, due to the existence of the constricted portion, the wall thickness between adjacent communicating portions in the cylinder head becomes large, so the dead space created between the communicating portions of the cylinder head is utilized to secure a sufficient passage area through these portions. Therefore, the passage can be effectively used as a passage for passing blow-by gas or oil. At the same time, the presence of the passage removes excess meat between adjacent communicating portions, which has the advantage of reducing the weight of the cylinder head.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention; FIG. 1 is a partially sectional side view of the whole, FIG. 2 is a partially sectional plan view of the cylinder head and intake passage, and FIG. FIG. 4 is a sectional view taken along the line -- in FIG. 3. 1...Cylinder block, 2...Cylinder head,
4...Cylinder, 5...Combustion chamber, 6...Intake port, 14,
15... Intake passage, 17, 18... First throttle valve, 19
...second throttle valve, 21...communication part, 22...throttle part, 2
7...Aisle.

Claims (1)

[Scope of Claims] 1. A cylinder block comprising a plurality of cylinders arranged in parallel, a plurality of combustion chambers connected to the cylinders, and a cylinder head having a plurality of intake ports opened to each of the combustion chambers, The cylinder head is provided with a plurality of intake passages connected to the intake ports of each combustion chamber, and a common first throttle valve is provided upstream of these intake passages, and in some of these intake passages, A four-stroke engine, wherein a second throttle valve is provided downstream of the first throttle valve, and the intake passages communicate with each other between the intake port and the second throttle valve for each combustion chamber. In the mutual communication portion of the intake passage, a constriction portion having a shape that reduces the passage area as it advances toward the intake port side and widens from the middle is provided, and the intake passage is sandwiched between adjacent mutual communication portions in the cylinder head. An intake device for a four-cycle engine, characterized in that a passage extending in the axial direction of the cylinder is formed in the portion where the cylinder is inserted.