JPH0968060A - Valve system of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce any pump loss and improve fuel consumption under a low load condition by providing at least one scavenging valve and two exhaust gas valves and constructing one of the two exhaust gas valves in valve timing variable structure and controlling the concerned valve in response to an engine load, in a 2-cycle type internal combustion engine. SOLUTION: Two scavenging gas ports 20-1, 20-2 and two exhaust gas ports 22-1, 22-3 are respectively formed on the cylinder head 6 of a 2-cycle type internal combustion engine 2 and scavenging valves 30-1, 30-2 and exhaust gas valves 32-1, 33-2 are provided in those ports respectively. And one side exhaust gas valve 32-1 is set on the fixed side where the valve timing is fixed and the other side exhaust gas valve 32-2 is set on the variable side where the valve timing is variable. The variable side exhaust gas valve 32-2 is so constructed that by making feeding/discharging control on the pressure oil flowing through a control valve based on the output of a load detecting means, the helical piston of a valve timing varying means is moved in the axial direction to allow both a cam shaft 40 and a cam shaft pulley to make mutually relative rotation to vary valve timing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve operating system for an internal combustion engine, and more particularly, it can reliably perform scavenging of a two-cycle type internal combustion engine at a low load and can reduce pump loss at a low load. The present invention relates to a valve operating system for an internal combustion engine, which can improve the efficiency of scavenging, improve fuel efficiency, and eliminate the need for a throttle valve.

[0002]

2. Description of the Related Art As an internal combustion engine, there is a two-cycle engine in which fresh air and fuel are introduced into a combustion chamber for combustion and exhausted while a combustion gas is exhausted while the crankshaft makes one revolution.
There are two-cycle internal combustion engines in which gas is exchanged using a scavenging port and an exhaust port which communicate with the combustion chamber without using an intake valve and an exhaust valve, and in which gas is exchanged using a scavenging valve and an exhaust valve.

A two-cycle internal combustion engine in which gas is exchanged using the scavenging valve and the exhaust valve is disclosed in Japanese Patent Laid-Open No. 3-100.
316 and Japanese Patent Laid-Open No. 3-100338.

In the internal combustion engine disclosed in Japanese Patent Laid-Open No. 3-100316, a scavenging port and an exhaust port communicating with the combustion chamber are provided in a cylinder head, and a scavenging valve and an exhaust valve for opening and closing the scavenging port and the exhaust port are provided. Is provided, a supercharger is provided in the intake passage communicating with the scavenging port, a fuel injection valve for directly injecting fuel is provided in the combustion chamber, and the center line of the fuel injected from the fuel injection valve flows into the combustion chamber. It is provided so as to intersect with the scavenging air flow and to be oriented near the ignition plug facing the combustion chamber.

The internal combustion engine disclosed in Japanese Patent Laid-Open No. 3-100338 has a scavenging valve and an exhaust valve for opening and closing a combustion chamber in a cylinder head, and a fuel injection valve for directly injecting fuel into the combustion chamber. While moving each operating center angle of the scavenging valve and the exhaust valve to the advance side in accordance with the increase of the engine speed, the advance angle of the operation center angle of the scavenging valve with respect to the advance angle of the operation center angle of the exhaust valve Is set to 1/2.

[0006]

By the way, a scavenging valve and an exhaust valve are provided in a cylinder head, a fuel injection valve for directly injecting fuel is provided in a combustion chamber, and a supercharger is provided in an intake passage.
In a cycle type internal combustion engine, a throttle valve is provided in the intake passage on the upstream side of the supercharger, and the air amount is adjusted by the opening of this throttle valve.

However, the two-cycle type internal combustion engine has a problem that scavenging cannot be sufficiently performed when the load is low.
Therefore, the two-cycle type internal combustion engine has a disadvantage that the efficiency of scavenging decreases at low load, combustion becomes unstable, misfire occurs, and fuel efficiency deteriorates.

Further, like the internal combustion engine disclosed in the above-mentioned Japanese Patent Laid-Open No. 3-100338, the operating central angles of the scavenging valve and the exhaust valve are shifted to the advance side in accordance with the increase of the engine speed. If the advance angle of the operation center angle of the scavenging valve is set to 1/2 with respect to the advance angle of the operation center angle of the exhaust valve, the phase between the scavenging valve and the exhaust valve can be changed. Since the opening period of the exhaust valve is not changed according to the load, there is a disadvantage that it is difficult to reliably perform scavenging at low load.

[0009]

SUMMARY OF THE INVENTION In order to eliminate the above-mentioned disadvantages, the present invention is directed to at least one scavenging valve and at least two exhaust valves for opening and closing a combustion chamber in a cylinder head of a two-cycle internal combustion engine. And one of the two exhaust valves is set as a fixed exhaust valve with a fixed valve timing, and the other is set as a variable exhaust valve whose valve timing is variable. Valve timing varying means for varying the engine timing of the internal combustion engine, and load detecting means for detecting the engine load of the internal combustion engine. According to the engine load detected by the load detecting means, the valve timing of the variable side exhaust valve is changed to the fixed side exhaust gas. It is characterized in that control means for controlling the valve timing varying means is provided so as to be retarded with respect to the valve timing of the valve.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION A valve train according to the present invention sets one of two exhaust valves provided in a cylinder head of a two-cycle type internal combustion engine to a fixed side exhaust valve having a fixed valve timing and the other one. By setting the variable side exhaust valve with variable valve timing and controlling the valve timing of the variable side exhaust valve to be retarded with respect to the valve timing of the fixed side exhaust valve by the control means, The opening period of the exhaust valve can be changed according to the engine load, and the overlap between the scavenging valve and the exhaust valve can be changed according to the engine load. Can be controlled without.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 10 show an embodiment of the present invention. In FIG. 5, 2 is a two-cycle type internal combustion engine,
4 is a cylinder block, 6 is a cylinder head, 8 is a cylinder, 10 is a piston, 12 is a connecting rod,
14 is a combustion chamber. The internal combustion engine 2 has a spark plug 16 and a fuel injection valve 18 facing the combustion chamber 14 of the cylinder head 6. The fuel injection valve 18 is the combustion chamber 1
Directly inject fuel into No. 4.

The cylinder head 6 is provided with a scavenging port 20 and an exhaust port 22 which communicate with the combustion chamber 14. In this embodiment, as shown in FIG. 7, two scavenging ports 20-1 and 20-2 and two exhaust ports 2 are provided, respectively.
2-1 and 22-2 are provided. Two scavenging ports 2
An intake passage 24 is communicated with the 0-1 and 20-2. The two exhaust ports 22-1 and 22-2 are in communication with the exhaust passage 26.

A supercharger 28 is provided in the intake passage 24. The internal combustion engine 2 has no throttle valve in the intake passage 24 upstream of the supercharger 28.

The scavenging valves 20-1 and 20-2 and the exhaust ports 22-1 and 22-21 are connected to the scavenging valves 30- and 30-, respectively.
1.30-2 and exhaust valves 32-1 and 32-2 are provided.

The valve operating device 34 for opening and closing the scavenging valves 30-1, 30-2 and the exhaust valves 32-1, 32-2 has one of the two exhaust valves 32-1, 32-2 with a valve timing. The fixed side exhaust valve 32-1 is fixed, and the other side is set to the variable side exhaust valve 32-2 whose valve timing is variable.

The scavenging valves 30-1, 30-2, the fixed side exhaust valve 32-1 and the variable side exhaust valve 32-2 constitute a drive mechanism 36.
Is driven to open and close. The drive mechanism 36 is, for example, as shown in FIG.
As shown in FIG. 8, a fixed cam shaft 38 and a variable cam shaft 40, which are rotated in synchronization with the crank shaft by a timing belt (not shown), are provided on the cylinder head 6 so as to be pivotally supported.

A scavenging cam 42 is attached to the fixed side cam shaft 38.
-1 and 42-2 and the fixed side exhaust cam 44 are provided.
The fixed side cam shaft 38 includes a scavenging rocker arm 46 and a scavenging rocker arm 46 by a scavenging cams 42-1 and 42-2 and a fixed side exhaust cam 44, respectively.
-1 through 46-2 and the fixed rocker arm 48,
The scavenging valves 30-1 and 30-2 and the fixed side exhaust valve 32-1
Open and close and drive.

A variable side exhaust cam 50 is provided on the variable side cam shaft 40. The variable side exhaust cam shaft 40 drives the variable side exhaust cam 50 to open and close the variable side exhaust valve 32-2 via the variable side exhaust rocker arm 52.

The internal combustion engine 2 has a variable side exhaust valve 32-2.
A valve timing changing means 54 for changing the valve timing of is provided. Valve timing changing means 54
For example, as shown in FIG. 9, a variable cam shaft pulley 56 is rotatably provided at one end of the variable cam shaft 40, and a piston is provided between the variable cam shaft 40 and the variable cam shaft pulley 56. A chamber 58 is formed, and a helical piston 60 that internally rotates the variable side cam shaft 40 and the variable side cam shaft pulley 56 by axial movement is built in the piston chamber 58.

The helical piston 60 has a pressure chamber 62 at one end and a return spring 64 at the other end. The pressure chamber 62 includes an oil passage 6
6 communicates with the oil pump 68. A solenoid type control valve 70 for controlling the oil introduced into the pressure chamber 62 is provided in the middle of the oil passage 66.

The valve timing varying means 54 moves the helical piston 60 in the axial direction by supplying and stopping the oil to the pressure chamber 62 by the control valve 70, thereby moving the variable side cam shaft 40 and the variable side cam shaft pulley 56. By making relative rotation, as shown in FIG. 10, the valve timing of the variable side exhaust valve 32-2 is delayed relative to the valve timing of the fixed side exhaust valve 32-2.

The control valve 70 of the valve timing changing means 54 is controlled by the control means 72. Control means 7
2 is provided with load detection means 74 for detecting the engine load of the internal combustion engine 2. The load detecting means 74 can be constituted by, for example, an intake air amount detecting means, an engine speed detecting means, or the like (not shown) for obtaining the injection period of the fuel injection valve 18 and the ignition timing of the ignition plug 16.

The control means 72 delays the valve timing of the variable side exhaust valve 32-2 with respect to the valve timing of the fixed side exhaust valve 32-1 according to the engine load detected by the load detection means 74. Valve timing changing means 5
Control 4

That is, when the engine load detected by the load detecting means 74 is low, the valve timing of the variable side exhaust valve 32-2 is shifted to the retard side with respect to the valve timing of the fixed side exhaust valve 32-1. The control valve 70 of the valve timing changing means 54 is controlled. Also, the load detection means 7
When the engine load detected by No. 4 is high, the variable side exhaust valve 3
The control valve 70 of the valve timing changing means 54 is controlled so that the valve timing of 2-2 is synchronized with the valve timing of the fixed side exhaust valve 32-1.

Next, the operation of the embodiment will be described.

The control means 72 of the valve operating device 34 controls the control valve 70 of the valve timing varying means 54 according to the engine load detected by the load detecting means 74 during the operation of the internal combustion engine 2, and the variable side exhaust valve 32. The valve timing of -2 is controlled to be retarded with respect to the valve timing of the fixed side exhaust valve 32-1.

As shown in FIGS. 1 and 3, the control means 72 delays the valve timing of the variable side exhaust valve 32-2 with respect to the valve timing of the fixed side exhaust valve 32-1 when the internal combustion engine 2 has a low load. The control valve 70 of the valve timing changing means 54 is controlled so as to shift to the corner side.

As a result, when the internal combustion engine 2 with a small amount of air for combustion has a low load, the valve timings of the fixed side exhaust valve 32-1 and the variable side exhaust valve 32-2 deviate and the scavenging valve 30 is overloaded. The lap period can be lengthened and the valve opening period of the entire exhaust valve 32 can be lengthened, so that sufficient scavenging can be performed, and the amount of air supplied from the scavenging port 20 to the combustion chamber 12 can be increased. By blowing through the exhaust port 22, the amount of air can be reduced.

The control means 72 controls the valve timing variable means 54 to gradually shift the valve timing of the variable side exhaust valve 32-2 to the advance side when the internal combustion engine 2 gradually shifts from a low load to a high load. Control 70.

The control means 72 synchronizes the valve timing of the variable side exhaust valve 32-2 with the valve timing of the fixed side exhaust valve 32-1 when the internal combustion engine 2 with a large amount of air for combustion has a high load. , Valve timing changing means 5
4 controls the control valve 70.

As a result, when the internal combustion engine 2 with a large amount of air for combustion has a high load, the valve timings of the fixed side exhaust valve 32-1 and the variable side exhaust valve 32-2 match and the scavenging valve 30 and Since the overlap period can be shortened and the opening period of the exhaust valve 32 as a whole can be shortened, the amount of air supplied from the scavenging port 20 to the combustion chamber 12 is prevented from passing through to the exhaust port 22. Then
The amount of air can be increased.

As described above, the valve operating device 34 includes the control means 7
By controlling the valve timing of the variable side exhaust valve 32-2 to be retarded with respect to the valve timing of the fixed side exhaust valve 32-1 according to the engine load, the exhaust valve 32 of the exhaust valve 32 is controlled according to the engine load. The valve opening period can be changed, the overlap between the scavenging valve 30 and the exhaust valve 32 can be changed according to the engine load, and the amount of combustion air can be controlled without using a throttle valve. it can.

Therefore, the valve gear 34 can reliably perform the scavenging of the two-cycle type internal combustion engine 2 when the load is low, can reduce the pump loss when the load is low, and improve the efficiency of the scavenging. To improve fuel economy,
The throttle valve can be eliminated.

The reason why one of the two exhaust valves 32 is the fixed exhaust valve 32-1 is that the scavenging valve 30 and the exhaust valve 32 are over-exposed in the two-cycle internal combustion engine 2 as shown in FIG. Exhaust valve 3 when scavenging for a long lap period
This is because it is necessary to open the valve 2 before the scavenging valve 30.

Therefore, one of the two exhaust valves 32 is used as the fixed exhaust valve 32-1, and the fixed exhaust valve 32-1 is opened before the scavenging valve 30 and the two exhaust valves 32 are opened.
Of the variable side exhaust valve 32-2 is controlled so as to be retarded with respect to the valve timing of the fixed side exhaust valve 32-1. While ensuring the function of opening the scavenging valve 30 earlier, the opening period of the exhaust valve 32 is changed according to the engine load, and the scavenging valve 30 and the exhaust valve 32 are overlapped according to the engine load. It is changing.

[0036]

As described above, according to the present invention, in the valve gear, the valve timing of the variable side exhaust valve is retarded with respect to the valve timing of the fixed side exhaust valve by the control means in accordance with the engine load. The exhaust valve opening period can be changed according to the engine load, and the overlap between the scavenging valve and the exhaust valve can be changed according to the engine load. The quantity can be controlled without the throttle valve.

Therefore, this valve gear can reliably perform scavenging of the two-cycle type internal combustion engine when the load is low,
It is possible to reduce the pump loss at the time of low load, improve the efficiency of scavenging, improve the fuel consumption, and eliminate the need for the throttle valve.

[Brief description of drawings]

FIG. 1 is a diagram showing a lift amount of an exhaust valve at a low load showing an embodiment of the present invention.

FIG. 2 is a diagram showing a lift amount of an exhaust valve under high load.

FIG. 3 is a diagram showing a relationship between opening / closing timings of a scavenging valve and an exhaust valve at a low load, and an injection period and an ignition timing.

FIG. 4 is a diagram showing the relationship between the opening / closing timing of the scavenging valve and the exhaust valve and the injection period and the ignition timing under high load.

FIG. 5 is a schematic configuration diagram of a valve train of an internal combustion engine.

FIG. 6 is a diagram showing valve timings of a scavenging valve and an exhaust valve.

FIG. 7 is a plan view showing an arrangement state of a scavenging valve and an exhaust valve.

FIG. 8 is a cross-sectional view showing an arrangement state of a scavenging valve and an exhaust valve.

FIG. 9 is a sectional view of a variable valve timing mechanism.

FIG. 10 is a diagram showing valve timings of a scavenging valve and an exhaust valve.

[Explanation of symbols]

 2 Internal combustion engine 14 Combustion chamber 16 Spark plug 18 Fuel injection valve 20-1 ・ 20-2 Scavenging port 22-1 ・ 22-2 Exhaust port 24 Intake passage 26 Exhaust passage 28 Supercharger 30-1 ・ 30-2 Scavenging valve 32-1 fixed side exhaust valve 32-2 variable side exhaust valve 34 valve device 38 fixed side cam shaft 40 variable side cam shaft 42-1 ・ 42-2 scavenging cam 44 fixed side exhaust cam 50 variable side exhaust cam 54 valve timing Variable means 72 Control means 74 Load detection means

Claims (2)

[Claims] 1. A cylinder head of a two-cycle type internal combustion engine is provided with at least one scavenging valve for opening and closing a combustion chamber and at least two exhaust valves, and one of the two exhaust valves is fixed with a fixed valve timing. Side exhaust valve and the other is set as a variable side exhaust valve whose valve timing is variable, and valve timing varying means for varying the valve timing of the variable side exhaust valve is provided to detect the engine load of the internal combustion engine. A load detecting means is provided, and the valve timing changing means is controlled so as to delay the valve timing of the variable side exhaust valve with respect to the valve timing of the fixed side exhaust valve according to the engine load detected by the load detecting means. A valve operating system for an internal combustion engine, comprising a control means. 2. The control means shifts the valve timing of the variable side exhaust valve to a retard angle side with respect to the valve timing of the fixed side exhaust valve when the engine load detected by the load detecting means is low. The valve timing varying means controls the valve timing varying means and synchronizes the valve timing of the variable side exhaust valve with the valve timing of the fixed side exhaust valve when the engine load detected by the load detecting means is high. The valve operating system for an internal combustion engine according to claim 1, which is a control means for controlling the means.