JPS60198325A - Intake device for engine - Google Patents

Abstract

PURPOSE:To reduce the deterioration of engine output and the vibration by communicating a surge tank through two communication paths and opening a changeover valve provided in one communication path continuously under such operating region where the engine load is lower than setting level. CONSTITUTION:Under operation of engine, the outputs from a rotation sensor 14 and a negative pressure 15 are fed to a control circuit 16. The control circuit 16 will read out an open or close signal from a changeover control map thus to open/close the changeover valve 12 through an actuator 13. Here, said valve 12 is closed under heavy load low rotation region of engine, for example, to produce the primary resonance of the intake air in a surge tank 1 with inherent primary frequency to be determined by the shape of first communication path 9 thus to perform highly efficient resonance supercharge to each cylinder through each suction manifold 5a-5f. Said valve 12 is opened continuously under low load region to feed the intake air between each chamber 3, 4 of surge tank 1 through second communication path 10 thus to feed same volume of intake air to each cylinder.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an intake system for an engine.

[Prior art]

-a The engine intake system is intended to efficiently supply intake air to the engine. By the way, there have been various methods for supplying intake air to the engine. One example is that the intake air resonates at a natural frequency determined by the shape of the intake passage, causing pressure fluctuations in the intake air. This phenomenon is utilized to efficiently push intake air into the cylinder due to its dynamic effect, thereby improving the filling efficiency.

As an intake system for an engine that employs the resonance supercharging method, which uses the resonance effect among the above-mentioned dynamic effects,
Conventionally, as shown in Japanese Unexamined Patent Publication No. 56-115818, a surge tank is provided for each cylinder group in which the ignition order is not consecutive, and a first tank is provided for communicating between the surge tanks.
A second communication path is provided, and the first communication path is provided. The passage length and cross-sectional area of the second communication passage are set so that resonance of the intake air is obtained in the ranges below the set rotation speed and above the set rotation speed, respectively, and the switching valve provided in the second communication passage is set so that the engine speed increases. There was one that opened and closed depending on whether the value was below or above a set value, and resonant supercharging was performed over a wide range of engine speeds.

However, conventional intake systems simply perform resonance supercharging over the entire operating range of the engine, and when the engine is under low load, the engine output is not as high (and
There has been a problem in that the pumping loss that occurs to obtain resonance of the intake air is large compared to the engine output, resulting in a noticeable drop in the engine output. Also, if there are variations in intake air distribution to each cylinder group due to the shape of the intake passage, etc.
Engine torque fluctuations due to differences in output between cylinder groups become noticeable, potentially increasing unpleasant engine vibrations, and this is particularly noticeable when the engine is under low load with a small amount of intake air.

[Purpose of the invention]

SUMMARY OF THE INVENTION In view of these problems, it is an object of the present invention to provide an engine intake system that can reduce the reduction in engine output and also reduce the occurrence of engine vibrations caused by variations in intake air distribution.

[Structure of the Invention] Therefore, the present invention provides an engine intake system in which a surge tank is connected to the first surge tank. A switching valve is provided in the second communication passage, and the shape of the first communication passage is designed so that resonance of intake air can be obtained in a predetermined rotation range, while the second communication passage is The system communicates between the surge tanks and detects the load condition of the engine, and when the load is below a set value, the switching valve is opened when the load is lower than the set value. At the same time, the intake air is supplied between the surge tanks through the second communication passage, thereby making the amount of intake air in each surge tank uniform.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

1 to 4 show an engine intake system according to an embodiment of the present invention. In the figure, 1 is a surge tank,
The surge tank 1 is divided into a first chamber 3 and a second chamber 4 by a partition wall 2.
It is defined as On the bottom of the first chamber 3, there are 1st, 3rd, and 3rd cylinders with discontinuous ignition order. The upstream ends of intake manifolds 5a, 5b, and 5c extending to each of the fifth cylinders are connected to the bottom of the second chamber 4, and the second, fourth, and fourth cylinders, which also have non-consecutive ignition orders, are connected to the upstream ends of intake manifolds 5a, 5b, and 5c extending to each of the fifth cylinders. Intake manifolds 5d, 5 extending to each sixth cylinder
The upstream ends of e and 5f are connected. Here, the engine is the first. Second. Third. 4th. Fifth. It is assumed that the 6th cylinder is ignited at every 120° crank angle in the ignition order.

Further, a downstream end of an intake pipe 6 is connected to a side surface of the surge tank 1. The downstream end of this intake pipe 6 is formed into two intake passages 7.8, which are connected to the first chamber 3 and the second chamber 4 of the surge tank 1, respectively.
Both intake passages 7.8 are connected to the first chamber 3 and the second chamber of the surge tank 1.
A first communication path 9 communicates with the chamber 4. This first
The passage length Ll and passage cross-sectional area S1 of the communication passage 9 are set in a low engine rotation range of 2700 rpm or less, and 5200 rpm.
The length and cross-sectional area are set such that gas resonance can be obtained in a high rotation range of pm or higher. In addition, both the intake passages 7
, 8 are respectively provided with throttle valves 11a and 1ib.

Further, an opening 10 is formed in the partition wall 2, and the opening IO serves as a second communication passage that connects the first chamber 3 and the second chamber 4 of the surge tank (2) in parallel with the first communication passage 9. , the second
The passage length of the communication passage (the thickness of the partition wall 2) L2 and the passage cross-sectional area (area of the opening 10) S2 are determined when the engine rotation speed is 270 or
The length and cross-sectional area are set so that gas resonance can be obtained in a medium rotation range of 5200 rpm or more. Further, this opening 10 is provided with a switching valve 12 for opening and closing it, and the switching valve 12 is opened and closed by an actuator 13.

In the figure, 14 is a rotation speed sensor that detects the engine rotation speed, 15 is a negative pressure sensor (load sensor number) that detects the intake negative pressure downstream of the throttle, and 16 is the engine rotation speed and intake negative pressure as parameters. This is a control circuit that has a switching valve control map, receives the outputs of both the sensors 14 and 15, reads an open signal or a close signal, and applies it to the actuator 13.

Here, as shown in Fig. 4, the switching valve control map stores all open signals regardless of the engine speed at low loads when the intake negative pressure is less than the set value -100 mmHg, and the intake negative pressure is set to When the load is high (value - 100mm 1g or more), a close signal is stored in the low rotation range where the engine rotation speed is 270 Orpm or less and a high rotation area of 5200 rpm or more, and an open signal is stored in the medium rotation range where the engine rotation speed is 270 Orpm or more and 520 Orpm or less. There is.

Next, the operation will be explained.

When the engine is running, the outputs of both the rotational speed sensor 14 and the negative pressure sensor 15 are applied to the control circuit 16;
Then, an open signal or a close signal is read out from the switching control map (see Fig. 4) depending on the load state and rotational state of the engine, and this signal is applied to the actuator 13 to control the switching valve 1.
2 is opened and closed.

Then, in the high load and low speed range of the engine, the switching valve 1
2 is closed, and the intake air in the surge tank 1 resonates first at a first natural frequency determined by the shape of the first communicating passage 9, etc., and each cylinder is efficiently resonantly supercharged. In addition, in the high-load and medium-speed range of the engine, the switching valve 12 opens, and the intake air in the surge tank 1 resonates first at the first natural frequency determined by the shape of the second communication passage 10. Resonant supercharging will be performed efficiently in each cylinder.

Furthermore, in the high-load, high-speed range of the engine, the switching valve 12 closes as in the low-speed range, but in this case, the intake air is 2 at the secondary natural frequency determined by the shape of the first communication passage 9, etc. Since next resonance occurs, in this case as well, efficient (resonant supercharging) is performed in each cylinder.

On the other hand, in the low engine load range, the switching valve 12 is always kept open, so the first chamber 3 of the surge tank 1
Intake air is supplied between the and second chamber 4 through the second communication passage 10, and the pressure in the first chamber 3 and the pressure in the second chamber 4 are approximately equal, so each cylinder has approximately the same pressure. This results in a large amount of intake air being supplied.

In the device of this embodiment as described above, the secondary resonance of the intake air is used to perform resonant supercharging in the engine high speed range, so it is more efficient than the conventional device without complicating the structure. Resonant supercharging can be achieved in a wide rotation range, and as a result, the engine output, particularly in the high rotation range, can be improved as shown by the solid line a in FIG. In FIG. 5, the dashed dotted line C and the dashed line indicate the 1st line, respectively. Second communication path 9
This figure shows the change in engine output obtained by using the resonance of the intake air determined by 10°.

In addition, in this device, when the engine is under low load in the low speed range and high speed range, the switching valve 12 is opened so that resonant supercharging is hardly performed. This does not mean that the output will decrease significantly (also, the first chamber 3 and the second chamber 4
Since the intake air amount is corrected between the two, even if variations in intake air distribution occur in the intake passage, unpleasant engine vibrations will not increase. Furthermore, at low loads in the mid engine speed range, it is preferable to close the switching valve 12 in order to reduce the pumping loss caused by the resonance effect, but at low loads with a small amount of intake air, the above-mentioned variation in intake air distribution is more important. It is preferable to take countermeasures from the viewpoint of engine stability, and in this device, the switching bone 12 is in an open state.

Note that in the above embodiment, the inside of the surge tank is separated from the first
Although the surge tank is divided into a chamber and a second chamber, the surge tank may of course be formed separately in the present invention. Further, the number of surge tanks may be more than two. Furthermore, instead of providing two throttle valves in the first communication passage, one throttle valve may be provided in the intake passage upstream of the first communication passage. Furthermore, the opening/closing control of the switching valve when the engine is under high load may be performed using a method different from that of the above embodiment.

Further, in the above embodiment, the first. The shape etc. of the second communication passage are set so as to obtain resonance of the intake air in the low, high and medium rotation ranges, but the present invention is designed such that the shape etc. of the first communication passage causes the resonance of the intake air in the predetermined rotation range. The second communication path may be configured to simply communicate between the surge tanks.

〔Effect of the invention〕

As described above, according to the engine intake system according to the present invention, the surge tank is connected to the first. A switching valve is provided in the second communication passage, and the shape of the first communication passage is designed to obtain intake resonance in a predetermined rotation range, while the second communication passage The tanks are communicated with each other, and the switching valve is always open in the operating range below the engine's set load, which prevents a drop in engine output and reduces the occurrence of engine vibration caused by variations in intake air distribution. There is an effect that can be done.

[Brief explanation of the drawing]

1 and 2 are a cross-sectional plan view and a cross-sectional side view of an engine intake system according to an embodiment of the present invention, respectively.
4 is a diagram showing the circuit configuration of the above device, FIG. 4 is a diagram showing the opening/closing signals of the control circuit 16 in the above device, and FIG. 5 is a diagram for explaining the effects of the above embodiment. 3.4...1st chamber, 2nd chamber (surge tank), 9...
・First communicating path, 10...Opening (second communicating path), 12・
...Switching valve, 15...Negative pressure sensor (load sensor), 1
6...Control circuit. Patent Applicant: Toyo Kogyo Co., Ltd. Agent, Patent Attorney Ken Hayase - Figure 1 Figure 3 Figure 4 Engine (rpm) - Only Figure 5 Engine RPM -

Claims (1)

[Claims] (11) A plurality of surge tanks, each of which communicates with each cylinder whose firing order is not consecutive, and whose passage length and passage cross-sectional area are set so as to obtain gas resonance in a predetermined rotation range. A first communicating path, a second communicating path that communicates between the surge tanks in parallel with the first communicating path, a switching valve that opens and closes the second communicating path, and a load sensor that detects the load state of the engine. and a control circuit that receives the output of the sensor and always opens the switching valve when the load is below a set value.