JP3721466B2 - Valve drive apparatus for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a valve drive apparatus for an internal combustion engine that moves an exhaust valve and an intake valve.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, an example of a valve drive apparatus for an internal combustion engine that moves an exhaust valve and an intake valve by a cam is configured as shown in FIG.
In the valve drive apparatus 50 for an internal combustion engine shown in FIG. 5, when the camshaft 51 is rotated, the cam 52 formed on the camshaft 51 rotates the rocker arm 53 and biases it in the closing direction by the spring 54. The valve (intake valve, exhaust valve) 55 is operated.
An adjustment screw 56 screwed into the end of the rocker arm 53 is for adjusting a valve clearance described later.
[0003]
The valve drive device 50 configured as described above opens the intake valve in the intake process of the internal combustion engine, closes the mixture in the intake state, and then opens the exhaust valve after compression and explosion. Then, a series of processes of exhausting are repeated. In this series of strokes, the crank of the internal combustion engine is rotated, and the camshaft 51 is rotated once by the rotation of the crank. In addition, in order to efficiently perform the transition stroke when shifting from the exhaust stroke to the next intake stroke, an overlap region is provided in the operation region of the exhaust valve and the intake valve. In addition, in order for the cam 52 to open and close the valve 55 reliably, a valve clearance is provided for the base circle of the cam 52 in a region where the valve 55 does not operate. In the region, only the rocker arm 53 moves and the valve 55 does not operate. Then, the rocker arm 53 starts the operation of the valve 55 thereafter. When the rocker arm 53 starts the operation of the valve 55, if the relative speed between the two when the rocker arm 53 contacts the valve 55 increases, the impact sound at the time of contact increases. A section that operates at an equal speed, that is, a buffer zone is provided.
FIG. 6 is a characteristic diagram showing the operating range of the cam 52 and the buffer band, and FIG. 7 is a cam profile characteristic diagram in which the cam 52 operates the exhaust valve and the intake valve as described above.
[0004]
[Problems to be solved by the invention]
When the intake-compression-explosion-exhaust process is repeated in the internal combustion engine, the valve 55 and the valve seat 57 are worn due to heat from the combustion chamber of the internal combustion engine or a collision when seated on the valve seat 57. . Further, when the contact portion wears due to the sliding of the rocker arm 53 and the cam 52 or the collision between the rocker arm 53 and the valve 55, the above-described valve clearance changes.
After the top dead center of the piston of the internal combustion engine, combustion continues to at least a crank angle of 70 degrees. Therefore, the actual closing timing of the exhaust valve changes with the change of the valve clearance, and the exhaust valve is closed during combustion of the internal combustion engine. If not, the problem arises that the exhaust valve burns out because high-temperature combustion gas leaks from the gap. Therefore, the valve drive system is regularly inspected after a certain period of operation, and the valve clearance is adjusted to prevent exhaust valve burnout.
[0005]
In the sliding portion between the camshaft and the rocker arm, the moving distance of the contact point of the rocker arm portion is smaller than the moving distance of the contact point of the camshaft. That is, since it slides at the same point, the wear on the rocker arm side increases. On the other hand, the valve seat, the valve portion, and the valve rocker arm portion are worn by high temperature heat from the combustion chamber. In the case of the valve drive device 50, as shown in FIG. 8, when the valve seat 57 is worn, the valve clearance changes in the direction of decreasing, and the contact portions of the rocker arm 53 and the cam 52 and the rocker arm 53 and the valve 55 are changed. As the valve wears, the valve clearance changes in the direction of increasing. FIG. 9 shows that the contact start point of the rocker arm 53 and the cam 52 shifts from the point A to the point B due to wear of the cam 52.
[0006]
Thus, the change form of the valve clearance accompanying the wear of each contact portion of the valve drive device 50 is complicated. For example, even if the wear balance is balanced and the valve clearance is constant, if the contact portions of the rocker arm 53 and the cam 52 are worn, the rocker arm 53 and the cam 52 are in a circular motion relationship. The operating area for is shifted. As described above, the combustion of the internal combustion engine continues after the piston top dead center until the crank angle reaches 70 degrees. For example, even if the valve clearance is constant, the exhaust valve operating region shifts and the exhaust valve lift start point If it comes after the top dead center of the piston of the internal combustion engine and before the crank angle of 70 degrees, a problem arises that the high-temperature combustion gas leaks from the gap and the exhaust valve burns out.
Therefore, in order to cope with the change in the valve clearance, conventionally, a material for improving wear resistance is used and an additional surface treatment is performed, but it is expensive and it is possible to completely prevent wear. Can not. For this reason, means for using a hydraulic lash adjuster or the like for the adjusting screw 56 or the like has been proposed, but there is a problem that the structure is complicated and expensive.
[0007]
Therefore, in the present invention, it is a problem to be solved to provide a valve drive apparatus for an internal combustion engine that can recognize the check timing of the valve drive system before the exhaust valve burns out without performing a periodic check. To do.
[0008]
[Means for Solving the Problems]
The above-described problems can be solved by the valve drive apparatus for an internal combustion engine described in the claims.
[0009]
According to the valve driving apparatus for an internal combustion engine according to claim 1, since the change in the valve clearance and the change in the valve lift starting point are uniquely determined, the valve clearance is increased by the wear of the valve driving system. When the value is smaller than a certain value, the exhaust valve operation start point is advanced and the intake valve operation end point is delayed, so that the air-fuel mixture in the combustion chamber is returned from the intake valve by the rise of the piston of the internal combustion engine. The start-up time becomes longer. As a result, if wear of the valve drive system progresses and the valve clearance becomes smaller than a certain value, the internal combustion engine cannot be started. Therefore, if the valve clearance is inspected and adjusted at this point, the exhaust valve Burnout can be prevented.
Also, by setting the exhaust valve and intake valve so that the operating overlap angle is 150 degrees or more in the operating range above the lift point of 0.1mm from the base circle of the cam, ignition does not occur at the start. The unburned air-fuel mixture is discharged through the exhaust valve during the exhaust stroke, and after top dead center, can be led to the combustion chamber from the exhaust valve that overlaps the operation. As a result, the unburned air-fuel mixture whose temperature has risen is reintroduced into the combustion chamber to improve the startability. Therefore, the internal combustion engine is caused by the delay in the operation end point of the intake valve due to wear of the valve drive system. The rapid deterioration of startability can be alleviated.
[0010]
According to the valve drive apparatus for an internal combustion engine according to claim 2, since it includes means for measuring the start time of the internal combustion engine and alarm means for issuing an alarm when the start time exceeds a predetermined time, The check timing of the valve clearance due to wear of the valve drive system can be recognized by an alarm by an alarm means.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of the present invention will be described.
FIG. 1 is a configuration explanatory diagram schematically showing the configuration of a direct acting valve drive apparatus 1 for an internal combustion engine.
As shown in FIG. 1, the valve drive apparatus 1 has a camshaft 3 disposed on a shaft 2 a of a valve (exhaust valve, intake valve) 2, and is formed on the camshaft 3 by the rotation of the camshaft 3. The valve 2 is configured to open when the cam 4 pushes down the lifter 5. In the valve clearance region provided for the base circle of the cam 4, the lifter 5 is not pushed down even when the cam 4 enters the operation region, and the valve 2 is in a closed state in contact with the valve seat 6. Further, the valve 2 is biased in a closing direction by a spring 7. The shim 8 adjusts the valve clearance.
[0012]
FIG. 2 shows a cam profile of the valve drive apparatus 1.
According to the cam profile of the valve drive apparatus 1 shown in FIG. 2, the operation start point of the exhaust valve including the buffer zone from the base circle of the cam 4 is after the top dead center of the piston of the internal combustion engine (not shown). The crank angle is set to a point after 70 degrees. Further, the operation end point of the intake valve is set to a point at which the crank angle is 90 degrees or more after the bottom dead center of the piston of the internal combustion engine at a lift point of 0.1 mm from the base circle of the cam 4. Furthermore, the operation overlap angle of the exhaust valve and the intake valve is set to be 150 degrees or more in crank angle at a lift point of 0.1 mm from the base circle of the cam 4.
[0013]
Next, the operation of the valve drive device 1 will be described.
When the valve clearance provided with respect to the base circle of the cam 4 becomes smaller due to wear caused by sliding between the cam 4 and the lifter 5, the exhaust valve operation start point becomes earlier and the intake valve operation end point. Therefore, since the air-fuel mixture in the combustion chamber is returned from the intake valve due to the rise of the piston of the internal combustion engine, the compression pressure is reduced and the starting time is lengthened. In addition, since the rotation center of the camshaft is on the same line due to the extension of the valve shaft, wear between the valve seat and valve, wear between the valve and lifter, and changes in valve clearance are uniquely determined, and wear between the cam and shim However, since the moving distance between the contact points is sufficiently large, the wear is smaller than the former.
[0014]
FIG. 3 is a characteristic diagram showing a result of experimentally measuring a change in the start time of the internal combustion engine with respect to a change in the valve clearance of the valve drive apparatus 1.
Due to wear caused by sliding between the cam 4 and the lifter 5 or the like, the valve clearance of the valve drive device 1 becomes small, the starting time becomes longer from a point smaller than 0.3 mm, and the starting time becomes less than 0.1 mm. Extremely long. The reason for this is that if the valve clearance is smaller than a certain value, the exhaust valve operation start point becomes earlier and the intake valve operation end point becomes later, as described above. This is because since the pressure is returned from the intake valve, the compression pressure is reduced and the starting time is lengthened. As described above, when the starting time becomes long and becomes 0.1 mm or less, the starting becomes practically impossible. At this time, if the exhaust valve operation start point is after the top dead center of the piston and the crank angle is after 70 degrees, combustion of the air-fuel mixture has been completed, so that the exhaust valve can be prevented from being burned out. . At this time, the valve clearance of the valve drive system may be adjusted.
[0015]
In addition, the exhaust valve and intake valve operating overlap angle is set to be over 150 degrees in the operating range above the lift point of 0.1 mm from the base circle of the cam 4, so that ignition occurs at start-up. The unburned air-fuel mixture that has not been discharged is discharged through the exhaust valve during the exhaust stroke, and after top dead center, can be led to the combustion chamber from the exhaust valve that overlaps the operation. Thereby, since the unburned air-fuel mixture whose temperature has been increased improves the startability of the internal combustion engine, it is possible to mitigate the rapid change in the start time of the internal combustion engine, that is, the rapid deterioration of the startability.
[0016]
FIG. 4 shows a configuration of an alarm system 10 that issues an alarm when the valve clearance of the valve drive device 1 becomes small and the start time of the internal combustion engine exceeds a set time.
The control unit 11 of the alarm system 10 uses the applied voltage output to the starter 12 as a trigger, and the number of revolutions based on the signal from the rotation detection sensor 13 attached to the crankshaft or camshaft is 2 cranking revolutions. The time until it becomes double or more is measured, and when the time becomes 5 seconds or more, for example, an alarm signal is output to the alarm device 14 and an alarm is issued from the alarm device 14. Instead of using the rotation detection sensor 13, the rotation speed may be detected by an ignition signal from an ignition device.
[0017]
As described above, if the alarm system 10 is provided, the check timing of the valve clearance due to wear of the valve drive system can be known by the alarm.
[0018]
【The invention's effect】
According to the present invention, it is possible to recognize the inspection timing of the valve drive system before the exhaust valve burns out without performing periodic inspection.
[Brief description of the drawings]
FIG. 1 is a configuration explanatory diagram schematically showing the configuration of a valve drive device.
FIG. 2 is an operation explanatory view showing a cam profile of the valve drive device.
FIG. 3 is a characteristic diagram showing a change in start time of the internal combustion engine with respect to a change in valve clearance.
FIG. 4 is a system diagram showing a configuration of an alarm system.
FIG. 5 is an explanatory diagram of a configuration of a conventional valve drive apparatus.
FIG. 6 is an explanatory diagram of an operating range of a cam.
FIG. 7 is an explanatory view of a cam profile of a conventional valve drive apparatus.
FIG. 8 is an explanatory diagram of a change in valve clearance of the valve drive device.
FIG. 9 is an explanatory view of movement of the contact point of the cam due to wear of the valve drive system.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Valve drive device 2 Valve 3 Cam shaft 4 Cam 5 Lifter 6 Valve seat 7 Spring 10 Alarm system 11 Control unit 12 Starter 13 Rotation detection sensor 14 Alarm device

Claims (2)

A valve drive apparatus for an internal combustion engine that drives a lifter by a cam to move an exhaust valve and an intake valve,
Before the wear, the exhaust valve operating start point including the buffer zone from the cam base circle is after the top dead center of the piston of the internal combustion engine at a crank angle of 70 degrees or more, and the intake valve operating end point is After the piston bottom dead center of the internal combustion engine at a lift point of 0.1 mm from the base circle of the cam, the crank angle is 90 degrees or more, and in the operating range of the lift point of 0.1 mm or more from the base circle of the cam. A valve drive apparatus for an internal combustion engine in which a cam profile is set so that an operation overlap angle between the exhaust valve and the intake valve is 150 degrees or more in crank angle. A valve drive apparatus for an internal combustion engine that drives a lifter by a cam to move an exhaust valve and an intake valve,
The operation start point of the exhaust valve including the buffer zone from the base circle of the cam is after the top dead center of the piston of the internal combustion engine, the crank angle is 70 degrees or more, and the operation end point of the intake valve is from the base circle of the cam The exhaust valve at a lift angle of 0.1 mm after the piston bottom dead center of the internal combustion engine, at a crank angle of 90 degrees or more, and in an operating range at a lift point of 0.1 mm or more from the base circle of the cam. And setting the cam profile so that the operation overlap angle of the intake valve is 150 degrees or more in crank angle,
Means for measuring a starting time of the internal combustion engine, the valve operating drive of combustion engine among said start time and a warning means for issuing an alarm if it exceeds a predetermined time.

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