JPH1181930A - Valve system of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a valve system of an internal combustion engine in which scavenging efficiency is not lowered when the opening valve of an exhaust valve is lagged. SOLUTION: An opening valve period of an exhaust valve is made to move to a lag side in an operation state in which an engine speed is low speed to middle speed and engine load is middle load to high load. But, because D1<D2 is determined when the diameter of an intake valve 10 is made D1 and the diameter of an exhaust valve 20 is made D2, an increase of an effective expansion stroke to be an effect on a plus side which can be obtained by the moving of the exhaust valve to the lag side for the opening valve period and deterioration of scavenging efficiency within deterioration of scavenging efficiency to be an effect on a minus side are improved by an increase of a valve diameter and the improvement of fuel consumption can be sufficiently obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve train for an internal combustion engine, and more particularly to a valve train having a variable valve timing mechanism for moving a valve opening period.

[0002]

2. Description of the Related Art Using a so-called variable valve timing mechanism, at low speed and low load, the opening period of the exhaust valve is moved to the advanced side to reduce internal EGR and stabilize combustion. 2. Description of the Related Art There is known an engine in which the opening of an exhaust valve is moved to a retard side to improve fuel efficiency by increasing an effective expansion stroke (see JP-A-7-301106). However, when the opening of the exhaust valve is retarded, the effective expansion stroke is increased as described above, but on the other hand, the scavenging efficiency is reduced, so that the net work is reduced, and as a result, the fuel consumption is reduced. There is a problem that improvement cannot be sufficiently obtained.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a valve train for an internal combustion engine in which the scavenging efficiency does not decrease when the exhaust valve is retarded.

[0004]

According to the first aspect of the present invention, there is provided an operating state detecting means for detecting an operating state of an engine, and an opening period of an exhaust valve when the engine is in a predetermined operating state. A valve train for an internal combustion engine comprising: a valve opening period moving unit that moves to a delay side, wherein the valve diameter of the exhaust valve is larger than the valve diameter of the intake valve. Is provided. In the valve train configured as described above, the valve diameter of the exhaust valve is set larger than the valve diameter of the intake valve. , The scavenging efficiency is prevented from deteriorating when moved to the delay side.

According to a second aspect of the present invention, in the first aspect of the invention, the opening period of the exhaust valve is delayed when the engine speed is low to medium and the engine load is medium to high. Is provided.
In the valve train configured as described above, scavenging when the opening period of the exhaust valve is moved to the delay side in the operating state where the engine speed is low to medium speed and the engine load is medium to high load. Deterioration in efficiency is prevented.

[0006]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows an intake valve 10 and an exhaust valve 2 for a combustion chamber 1 in an internal combustion engine to which the present invention is applied.
0 is schematically shown, and the diameter of the intake valve 10 is D
1. The characteristic is that D1 <D2 when the diameter of the exhaust valve 20 is D2.

FIG. 2 shows a variable valve which moves the valve opening period to a delay side when the exhaust valve 20 having a larger diameter than the intake valve 10 is in a predetermined operation state as shown in FIG. FIG. 3 is a diagram illustrating the structure and operation of a timing mechanism.
In FIG. 2, reference numeral 100 denotes an exhaust camshaft, and an exhaust cam 150 is formed integrally with the exhaust camshaft 100.

Reference numeral 200 denotes a pulley, and a tooth portion 250 is formed on the outer peripheral side of the outer base 210 of the pulley 200, and the tooth portion 250 meshes with a crankshaft (not shown) at a portion not shown. Toothed belt 40
The zero tooth 410 is engaged, and the pulley 200 is configured to make one rotation for every two rotations of the crankshaft.

The inner surface 2 of the inner base 220 of the pulley 200
Reference numeral 21 is supported by a pulley inner support member 110 fixed to the exhaust camshaft 100 so as to be movable in the axial direction and the rotational direction. On the other hand, the inner surface 211 of the outer base 210 of the pulley 200 is
Outer peripheral surface 121 of pulley outer support member 120 fixed to
It is made to slide on.

Reference numeral 300 denotes a piston, and a first
The spline 310 has a second spline 320 on the inner peripheral side. First spline 310 of piston 300
Engages with a spline 125 formed on the inner peripheral side of the central portion 122 of the pulley outer support member 120, and the second spline 320 engages with a spline 225 formed on the outer peripheral side of the inner base 220 of the pulley 200. doing.

The piston 300 is urged to the left in the figure by a spring 400, but hydraulic pressure is supplied through an oil passage 101 formed in the camshaft 100 and an oil passage 123 formed in the pulley outer support member 120. Then, it moves to the right in the figure. Here, each spline is a helical spline, and when the piston moves by supplying the hydraulic pressure as described above, the rotation phase of the exhaust camshaft 100 is delayed with respect to the pulley 200, that is, with respect to the crankshaft. Has been.

The supply and discharge of the hydraulic pressure are controlled by a hydraulic supply control valve 610, and the magnitude is controlled by a hydraulic adjustment valve 620. In addition, 630 is an oil pump that generates a base oil pressure, and 640 is a drain. The control of the hydraulic pressure supply control valve 610 and the hydraulic pressure adjustment valve 620 is performed by an electronic control unit (ECU) 700. The hydraulic supply control valve 610 has a solenoid so that hydraulic oil delivered from the oil pump 630 when energized and turned on is guided to the piston oil chamber 150 between the piston 300 and the pulley outer support member 120, At the time of OFF, the flow path is switched so that the hydraulic oil in the piston oil chamber 150 is discharged to the drain 640.

The ECU 700 includes an input interface circuit 710, a CPU 720, and a RAM 73, which are interconnected.
0, a ROM 740, and a digital computer having an output interface circuit 750. The CPU 720 includes an engine speed sensor 810 and a throttle opening sensor 820.
From the input signal from the ECU and a map as shown in FIG. 4 stored in advance in the ROM, and under the predetermined operating conditions, the exhaust camshaft 100
A signal for controlling the hydraulic pressure supply control valve 610 and the hydraulic pressure adjustment valve 620 is transmitted so that the phase is delayed by a predetermined amount with respect to the crankshaft. The ECU 700 also performs basic control of the fuel injection amount, the ignition timing, and the like, but is omitted because it is not relevant to the present invention.

FIG. 4 is a map showing an example of the amount of phase retardation corresponding to the engine speed and the throttle opening. In this example, a low to medium speed rotation and a low to high load are shown. In addition, the angle is delayed by up to 30 ° CA. The reason why the retard angle is limited to the above-described region is as follows.

First, while it is strongly desired to stabilize combustion during idling operation, if the opening of the exhaust valve is delayed, the exhaust valve is opened at the end of opening and at the beginning of opening of the intake valve. This is because the so-called overlap in which both the intake valve and the intake valve are open increases, the internal EGR amount increases, and the combustion becomes difficult to stabilize. Next, when the load is low, even if the opening of the exhaust valve is delayed, the merit is small and the pumping loss increases because the expansion work is small. Further, at the time of high rotation, since it is desired to lengthen the scavenging time as much as possible, it is preferable to obtain only the effect by increasing the valve diameter without causing a decrease in the scavenging efficiency without deteriorating the scavenging efficiency by delaying the opening of the exhaust valve. .

FIG. 3 shows that the piston 300 is driven by hydraulic pressure.
The right side of the drawing shows a state in which the exhaust camshaft 100 is pushed to the maximum limit.
For 0, ie, for the crankshaft, 3
It is retarded by 0 ° CA. 5 is an axial view of the state of FIG. 2 and FIG. 6 is an axial view of the state of FIG. FIG.
6 shows that the exhaust cam 150 operates with a delay of 30 ° CA in the case of FIG. 6 as compared with the case of FIG.

In FIGS. 2 and 3, reference numeral 150 denotes a damper, which is supplied with a hydraulic pressure as shown in FIG. 2 from a state where the hydraulic pressure as shown in FIG. 3 is supplied. When returning to a state in which the pulley 200 is not returned, the surface 124 on the outer peripheral side of the outer periphery of the pulley outer support member 120 (left side in the drawing) and the surface 231 on the inner side in the axial direction of the flange portion 230 of the pulley 200 (right side in the drawing) are aligned. This is to prevent a direct collision from generating noise. Also, 130, 330, 340
Is an oil seal for preventing the hydraulic pressure for operating the piston 300 from leaking.

Since the embodiment of the present invention is constructed and operates as described above, the exhaust camshaft opens with a predetermined delay in a predetermined operating state.
As shown in FIG. 1, the diameter D2 of the exhaust valve 20 is
, The deterioration of the scavenging efficiency is suppressed.

[0019]

According to the present invention, an increase in the effective expansion stroke, which is a positive effect obtained by moving the exhaust valve to the delay side of the valve opening period, and a deterioration in the scavenging efficiency, which is a negative effect, are obtained. Inside, the scavenging efficiency deteriorates due to the increase in the valve diameter.
As a result, the fuel efficiency can be sufficiently improved.

[Brief description of the drawings]

FIG. 1 is a diagram comparing the sizes of an intake valve and an exhaust valve of a valve train according to the present invention.

FIG. 2 is a diagram illustrating the structure and operation of a variable valve timing mechanism (non-retarded state).

FIG. 3 is a diagram illustrating the structure and operation of a variable valve timing mechanism (retarded state).

FIG. 4 is a diagram illustrating a retarded region.

FIG. 5 is a diagram showing a phase of a cam with respect to a pulley (non-retarded state).

FIG. 6 is a diagram showing a phase of a cam with respect to a pulley (retarded state).

[Explanation of symbols]

 Reference Signs List 100 exhaust cam shaft 125 helical spline 200 pulley 225 helical spline 300 piston 310 helical spline 320 helical spline 400 spring 500 toothed belt 610 hydraulic supply control valve 620 hydraulic adjustment valve 700 electronic control Unit 810: Engine speed sensor 820: Throttle opening sensor

Claims (2)

[Claims] An operating state detecting means for detecting an operating state of an engine, and a valve opening period moving means for moving an opening period of an exhaust valve to a delay side when the engine is in a predetermined operating state. A valve gear for an internal combustion engine, wherein the diameter of the exhaust valve is larger than the diameter of the intake valve. 2. The exhaust valve according to claim 1, wherein the opening period of the exhaust valve is shifted to a delay side in an operating state where the engine speed is low to medium speed and the engine load is medium to high load. Valve train.