JPH08218879A - Intake structure of four-cycle engine - Google Patents

Abstract

PURPOSE: To further effectively improve fuel consumption and to reduce exhaust gas by a method wherein an intake air return valve and an exhaust valve are driven through a common cam shaft and a cam phase angle varying device is arranged on the common cam shaft. CONSTITUTION: During partial load running at a low and middle speed rotation, the opening closing timing of an intake air return valve 19 is delayed togetherwith the opening closing timing of an exhaust valve 10 by a cam phase angle varying device 13 and even after an intake valve 8 is closed, the intake air return valve 19 is opened. Thus, an engine is reversed at an intake delay close mirror cycle and fuel consumption is improved through reduction of an intake pumping loss. Besides, since the opening closing timing of the exhaust valve 10 is simultaneously delayed, an overlap between the opening states of the intake valve 8 and the exhaust valve 10 is increased. Thereby, a part of burnt exhaust gas is returned to the cylinder again and internal partial EGR (exhaust gas recirculation) is effected, fuel consumption is further improved, and the generation of exhaust gas is also reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake structure for a four-cycle engine, and more particularly, to an engine operating range provided with an intake recirculation passage for returning a part of the intake air sucked into a cylinder during a compression process to the intake passage. It relates to an intake structure of a four-cycle engine capable of changing the operation between the Otto cycle (normal cycle) and the Miller cycle according to.

[0002]

2. Description of the Related Art In engine operation, the expansion timing is made larger than the compression ratio by making the intake valve closing timing earlier or later than usual.
The so-called Miller cycle technology, which expands the energy of combustion gas sufficiently and takes it out to improve the thermal efficiency to improve the fuel consumption, has been generally known, and an engine operated by such a Miller cycle has been generally known. As a conventional method, it is known that the closing timing of the intake valve is delayed and supercharging is performed by a highly efficient supercharger using a Lisholm compressor.

However, in such a Miller cycle engine, at the time of partial load when the throttle is at an intermediate opening degree, the fuel consumption is not so much improved due to the drive loss of the Lisholm compressor, and the Lisholm compressor,
Since an intercooler and other equipment are required, there is a problem that the structure becomes very expensive.

Therefore, in order to achieve both the improvement of the fuel consumption at the time of partial load where the throttle opening is an intermediate opening and the output performance at the time of a high load when the throttle opening is fully opened, without requiring a supercharger or the like. Is provided with an intake air recirculation passage branched from a normal intake air passage to recirculate a part of the intake air in the cylinder to the intake air passage during the compression process, and by changing the opening / closing timing of the intake air recirculation passage, the mirror cycle during partial load Therefore, a three-valve four-cycle engine, which can be switched so as to be an Otto cycle (normal cycle) under high load, has been conventionally known. (JP-A-52-139819, JP-A-5-5
(See, for example, 8-122317)

On the other hand, in addition to the above technique, in a four-cycle engine having a twin cam (DOHC) type valve system, the phase of the cam sprocket meshing with the timing chain and the phase of the cam shaft itself are set in the operating range of the engine. A cam phase angle varying device (VVT) has been conventionally known in which the opening / closing timing of the exhaust valve is made to correspond to the operating region of the engine by changing it by means such as hydraulic pressure. (For example, actual fairness 6
(See No. 12240, etc.)

[0006]

By the way, regarding the conventional four-cycle engine capable of switching between the Miller cycle and the Otto cycle with the above-mentioned three valves, any one of them is required to switch its cycle. A control mechanism that is not installed in a conventional engine, such as changing the opening / closing timing of the on-off valve provided in the intake air recirculation passage or stopping the opening / closing of the intake air recirculation valve in accordance with the operating region, is required. There is a problem that it must be newly added in the form.

The present invention is intended to eliminate the above-mentioned inconvenience in the intake structure of a conventional four-cycle engine. Specifically, it can be operated in a mirror cycle at a partial load, and can be operated normally at a high load. The intake structure of a 4-cycle engine that can be operated in a cycle and effectively uses the device that has been conventionally installed in the engine to switch between the cycles to improve fuel efficiency and reduce exhaust gas more efficiently. It is intended to be provided.

[0008]

According to the present invention, in order to solve the above-mentioned problems and to achieve the object, an intake valve is arranged in an intake port communicating with an intake passage as described in claim 1. An exhaust valve is provided in an exhaust port communicating with the exhaust passage, the intake valve and the exhaust valve are driven by different cam shafts, respectively, and an intake recirculation passage is provided branching from the intake passage. In a four-cycle engine in which an intake recirculation valve is provided in an intake recirculation port communicating with the intake recirculation passage, the intake recirculation port and the exhaust recirculation valve are driven by a common camshaft. Is arranged on the side of, and a cam phase angle varying device is installed with respect to the common cam shaft.

Further, in the intake structure of such a four-cycle engine, as described in claim 2, an on-off valve is installed in the middle of the intake gas recirculation passage.

[0010]

[Operation] With the above-mentioned configuration, the cam phase angle varying device (V
VT) delays the opening / closing timing of the exhaust valve and the opening / closing timing of the intake recirculation valve, and the intake recirculation valve is open even after the main intake valve is closed. Therefore, the engine operates in the delayed intake closed mirror cycle. Is
Fuel consumption is improved by reducing intake pumping loss.

Moreover, since the opening / closing timing of the exhaust valve is delayed at the same time, the overlap of the open state of the intake valve and the exhaust valve is expanded, and therefore, a part of the combusted exhaust gas is again in the cylinder. Then, internal EGR (exhaust gas recirculation) is obtained, fuel efficiency is further improved, and exhaust gas is reduced.

On the other hand, when the rotation speed is high and the load is high, the opening / closing timing of the exhaust valve and the opening / closing timing of the intake recirculation valve are returned to the normal state by the cam phase angle varying device so that the main intake valve is closed and the intake air is closed. Since the recirculation valve is also closed, the engine operates in the Otto cycle, ensuring high-speed performance without the need for a highly efficient supercharger.

A cam phase angle varying device (VVT)
The opening and closing timing of each valve will be delayed under partial load (low load), but by setting so that the opening and closing timing of each valve will return to the normal state under extremely low load such as idle operation. It is possible to avoid deterioration of combustion due to expansion of overlap between the open state of the intake valve and the exhaust valve at the time of load.

Further, according to the structure described in claim 2, when the load is high or when the load is extremely low, the intake recirculation passage is closed by the opening / closing valve.
The intake air that has once flown into the cylinder from the intake passage does not return from the intake recirculation passage during the intake stroke, preventing the engine performance from deteriorating due to the return of the intake air. Prevents the flow of intake air flowing toward the cylinder from being dispersed in the middle by the intake air recirculation passage, and prevents the atomization from worsening and combustion efficiency to worsen due to further weakening of the intake air flow. To be done.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the intake structure for a 4-cycle engine of the present invention will be described below with reference to the drawings.

FIG. 1 shows a structure to which the intake structure of the present invention is applied.
1 shows an overall outline of an example of a cycle engine including a control system thereof. An air flow meter is provided in an intake passage 3 for supplying air sucked from the atmosphere through an air cleaner to a combustion chamber 2 of an engine body 1. 4, following the throttle valve 5, an injector 6 for injecting fuel is installed, and an injector drive signal from a control unit (ECU) based on input signals from various sensors is used to match the characteristics of the engine. Fuel is injected from the injector 6 so that the set air-fuel ratio is obtained, and the air-fuel mixture is supplied into the combustion chamber 2.

In such a fuel injection type four-cycle engine, the drive type of the intake valve 8 arranged in the intake port 7 and the exhaust valve 10 arranged in the exhaust port 9 is the intake valve 8 and the exhaust valve. 10 is another camshaft 1
Twin cams (DO
HC) type.

At the end of the camshaft 12 on the exhaust valve 10 side, each camshaft 11 is rotated by rotating the crankshaft in order to automatically adjust the opening / closing timing of the exhaust valve 10 in accordance with the operating region of the engine. Known from the related art, the phase of the cam shaft 12 itself is relatively changed according to the operating region of the engine with respect to the phase of a cam sprocket (neither is shown) meshing with a timing chain for driving the motors 12, 12. Cam phase angle varying device (VVT) 13 having the structure
Is provided.

2 and 3 show the outline of an embodiment of the intake structure of the present invention applied to the above-described four-cycle engine. As shown in FIG. 3 is branched downstream of the throttle valve 5 into a main intake passage 3a and an intake recirculation passage 3b, and an intake port 7 of the cylinder head following the main intake passage 3a is provided with a cam at its combustion chamber opening. An intake valve 8 that is opened / closed at a constant opening / closing timing by a cam 11a provided on the shaft 11 is provided.

An exhaust port 9 communicating with an exhaust passage 15 is formed in the cylinder head on the side opposite to the intake port 7 with an ignition plug 14 disposed substantially in the center of the combustion chamber interposed therebetween. An exhaust valve 10 that is opened / closed at a constant opening / closing timing by a cam 12a provided on a cam shaft 12 is provided at the combustion chamber opening of the exhaust port 9.

As for the intake recirculation passage 3b branched from the intake passage 3 downstream of the throttle valve 5, an opening / closing valve 17 for opening and closing the passage is provided in the middle of the intake recirculation passage 3b. Continued intake recirculation port 18
However, it is formed on the cylinder head at the side opposite to the exhaust port 9 on the side opposite to the intake port 7 side with the spark plug 14 interposed therebetween, and at the combustion chamber opening of the intake recirculation port 18. Is arranged so that an intake air recirculation valve 19 for opening and closing the opening at a constant opening / closing timing is driven by a cam 12b different from the cam 12a provided on the cam shaft 12 of the exhaust valve 10. ing.

In this embodiment, as shown in FIG.
The intake port 7 and the exhaust port 9 are each opened at two places on the top wall portion of the combustion chamber, and the intake valve 8 or the exhaust valve 10 is provided at each combustion chamber opening portion. Intake recirculation valve 1 of port 18
Together with 9, five valves are provided for each cylinder.

Regarding the basic valve opening / closing timing of each of the intake valve 8, the exhaust valve 10 and the intake recirculation valve 19, as shown in FIG. 4, the closing timing of the exhaust valve 10 is at the piston top dead center position. The intake recirculation valve is set such that its opening range is within the opening range of the intake valve 8 and its closing timing coincides with the closing timing of the intake valve 8.

Further, the on-off valve 17 provided in the middle of the intake air recirculation passage 3b is closed at the time of extremely low load and high load, and opened at the time of partial load, for example, related to the operation of the throttle valve 5 and the like. It is controlled to open and close automatically.

The operation of the intake structure of the four-cycle engine of the present embodiment having the above structure will be described below.

The intake valve 8 and the exhaust valve 1 are operated at a high load at a high speed and at an extremely low load such as an idle operation.
0 and the intake air recirculation valve 19 are opened and closed at the basic valve opening and closing timings of the pattern shown in FIG. 4, and the intake air recirculation passage 3b is closed by the on-off valve 17.

Therefore, the intake valve 8 and the intake recirculation valve 19 are closed at the same time, and the engine is operated in the Otto cycle (normal cycle). At this time, the intake recirculation passage 3b is closed by the opening / closing valve 17. ,
The intake air, which once flows into the combustion chamber 2 from the main intake passage 3a at the time of high load, does not return from the intake recirculation passage 3b during the intake stroke, and at the time of extremely low load, the intake passage 3
The flow of intake air inside is dispersed in the main intake passage 3a and the intake air recirculation passage 3b, so that the flow of intake air in the vicinity of the injector 6 does not become weaker.

At low / medium speed rotation and under partial load (low load), the phase angle of the cam shaft 12 is changed by the cam phase angle varying device (VVT) 13 installed at the end of the cam shaft 12, and the cam is rotated. Each cam 12a on the shaft 12,
As shown in FIG. 5, the opening / closing timings of the exhaust valve 10 and the intake recirculation valve 19 driven by 12b are simultaneously delayed, and the opening / closing valve 17 of the intake recirculation passage 3b is opened so that the intake recirculation port 3b is opened. 18 is the intake passage 3
Be communicated to.

Therefore, even after the intake valve 8 is closed, the intake recirculation valve 19 is open, and at the beginning of the compression process after intake, a part of the intake air in the combustion chamber 2 returns to the intake recirculation passage 3b, and the engine is The operation is performed in the mirror cycle of late intake closing, the closing timing of the exhaust valve 10 is delayed, and the overlap region of the open state of the exhaust valve 10 and the intake valve 8 is expanded. The part is returned to the combustion chamber 2.

According to the intake structure of the four-cycle engine of the present embodiment having the above-described operation, the engine is operated in the late intake closing mirror cycle at the partial load (low load), so that the intake pumping loss is reduced. As a result, the fuel efficiency can be improved, and the opening / closing timing of the exhaust valve 10 is delayed so that the intake valve 8 and the exhaust valve 1
Since the overlap of the open state of 0 is expanded, a part of the combusted exhaust gas is returned to the combustion chamber and the internal E
GR (exhaust gas recirculation) can be obtained, fuel efficiency can be further improved, and exhaust gas can be reduced.

On the other hand, when the load is high, the engine is operated in the Otto cycle, so high-speed performance can be ensured without the need for a high-efficiency supercharger, and the intake recirculation passage 3b is closed by the opening / closing valve 17. Therefore, the intake air that once flows into the combustion chamber 2 from the main intake passage 3a does not return from the intake recirculation passage 3b during the intake stroke, and deterioration of the engine performance due to the return of the intake air can be prevented. .

Further, when the load is extremely low, the opening / closing timing of the exhaust valve 10 is not delayed, so that deterioration of combustion due to expansion of the overlap region of the open state of the intake valve 8 and the exhaust valve 10 can be avoided, and intake air can be avoided. Since the recirculation passage 3b is closed by the opening / closing valve 17, it is prevented that the flow of intake air is further weakened, atomization is deteriorated, and combustion efficiency is deteriorated.

By the way, in the one-cylinder five-valve engine as in this embodiment, the intake passage 3 branches into the main intake passage 3a and the intake recirculation passage 3b, and the opening / closing valve 17 is provided in the middle of the intake recirculation passage 3b. With the structure provided, the opening area of the entire intake port 7 can be made larger than in the case of the conventional three-valve engine provided with the intake gas recirculation passage, and the spark plug 14 is arranged in the center of the combustion chamber 2. It becomes possible.

Therefore, for example, the opening / closing timing of the exhaust valve is set as shown in FIG. 4 without providing the cam phase angle varying device (VVT) 13, and the opening / closing timing of the intake valve and the intake recirculation valve is set as shown in FIG. By setting and operating the opening / closing valve 17 in the intake air recirculation passage 3b so as to open at partial load and close at other times without changing the valve timings thereof, switching operation between the Otto cycle and the Miller cycle is performed. It can be performed with higher performance than in the case of a 3-valve engine.

On the other hand, according to the intake structure of the present embodiment, the cam phase angle varying device (V which is conventionally used to make the opening / closing timing of the exhaust valve variable).
By simply using the VT) 13 as it is, it is possible to control the opening / closing timing of the exhaust valve 10 and the opening / closing timing of the intake air recirculation valve 19 at the same time. It becomes possible to carry out the switching operation between the Otto cycle and the Miller cycle with higher performance.

Although one embodiment of the intake structure for the four-cycle engine of the present invention has been described above, the present invention is not limited to the specific structure shown in the above embodiment, and for example, It is applicable not only to fuel injection type engines but also to engines using carburetors.
Not only 5 valve engine but 3 valve (intake valve 1,
It goes without saying that the design can be changed as appropriate, such as being applicable to an engine having an exhaust valve 1, an intake air recirculation valve 1) or other number of valves.

[0037]

According to the intake structure of the four-cycle engine of the present invention as described above, it is possible to operate in the Otto cycle when the load is high and to operate in the Miller cycle when the load is high, and to operate at high speed. It is possible to reduce pumping loss and improve fuel efficiency without deteriorating the performance at the time, and to switch from the Otto cycle to the Miller cycle, a new device is not required and the engine has been changed from before. By effectively utilizing the installed device, it is possible to more efficiently improve fuel efficiency and reduce exhaust gas.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an overall outline of an example of a four-cycle engine to which an intake structure of the present invention is applied.

FIG. 2 is a side view explanatory view showing the outline of an embodiment of the intake structure of the present invention applied to the 4-cycle engine shown in FIG.

3 is an explanatory plan view of the embodiment shown in FIG.

4 is a graph showing the opening / closing timing of each valve during the Otto cycle in the four-cycle engine of the embodiment shown in FIG.

5 is a graph showing the opening / closing timing of each valve during a Miller cycle in the four-cycle engine of the embodiment shown in FIG.

[Explanation of symbols]

 3 intake passage 3b intake recirculation passage 7 intake port 8 intake valve 9 exhaust port 10 exhaust valve 11 cam shaft (intake side) 12 cam shaft (exhaust side) 13 cam phase angle varying device 15 exhaust passage 17 intake recirculation passage opening / closing valve 18 Intake recirculation port 19 Intake recirculation valve

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical display area F02B 29/08 F02B 29/08 FF02D 13/02 F02D 13/02 L H K F02M 25/07 520 F02M 25/07 520A 580 580A

Claims (2)

[Claims] 1. An intake valve is provided in an intake port communicating with the intake passage, an exhaust valve is provided in an exhaust port communicating with the exhaust passage, and the intake valve and the exhaust valve are respectively driven by different camshafts. In addition, the intake recirculation valve is provided with an intake recirculation passage branching from the intake passage, and the intake recirculation valve is disposed in the intake recirculation port communicating with the intake recirculation passage. An intake recirculation port is arranged on the exhaust port side so as to be driven by a common cam shaft, and a cam phase angle varying device is installed with respect to the common cam shaft. Engine intake structure. 2. The intake structure for a four-cycle engine according to claim 1, wherein an on-off valve is installed midway in the intake air recirculation passage.