JPH0625609Y2 - Valve forced opening / closing device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of use) The present invention relates to a valve forced opening / closing device for forcibly opening / closing an intake / exhaust valve of an internal combustion engine.

(Prior Art) In order to improve the followability of the intake and exhaust valves when the engine rotates at high speed,
Desmodromic type in which a cam for opening and closing is formed on the camshaft, and the intake and exhaust valves are forcibly opened and closed by these cams without the help of valve springs. Valve opening / closing device is known (for example, USP 4,471,729, JP-A-60-).
32910, JP-A-60-108513, etc.).

By forcibly opening and closing the intake / exhaust valve by each cam, the influence of surge of the valve spring in the high rotation range is eliminated, and the internal combustion engine can be rotated at a high speed.

(Problems to be solved by the invention) However, it is actually difficult to reduce the clearance between the valve opening cam and the valve closing cam to 0 due to the restriction of the processing accuracy of the cam and the rocker arm, and the intake and exhaust air is exhausted within this clearance. There is a problem that the valve flaps, the strength of the valve train is impaired, and the performance of the engine is deteriorated.

The present invention aims to solve these conventional problems.

(Means for Solving the Problems) In order to achieve the above object, in the present invention, in a valve forced opening / closing device of an internal combustion engine, a valve opening cam that pushes the valve open to a cam shaft that is rotationally driven in synchronization with the engine. And a valve closing cam for pulling up the valve, and a tappet for slidingly contacting the valve opening cam is provided on the top of the valve.
A guide part that inserts a cam shaft and connects a bucket that is slidable in the axial direction of the valve to the valve, and that provides a plunger that slides on the valve closing cam, and that slidably inserts the plunger into the bucket, Partition walls for partitioning the high pressure oil chamber and the low pressure oil chamber are formed inside and outside the plunger, respectively, and an oil passage for guiding pressurized oil to the low pressure oil chamber is formed.
A check valve is provided to open the oil that is about to flow into the high pressure oil chamber from the low pressure oil chamber.

(Operation) Based on the above configuration, as the camshaft rotates, the valve opening cam slides against the tappet and pushes down the tappet to lift the valve from the valve seat, and then the valve closing cam slides against the plunger. While pushing up the bucket while pulling up the valve, it is forced to sit on the valve seat.

Since the plunger is always in sliding contact with the valve closing cam by the oil pressure guided from the low pressure oil chamber to the high pressure oil chamber through the check valve, the valve flap is prevented from fluttering by making the clearance with the valve closing cam zero. At the same time, the hydraulic pressure presses the valve against the valve seat to seal the combustion chamber.

If the load acting on the plunger increases due to the inertial force of the valve and bucket, the check valve closes and the pressure in the high-pressure oil chamber rises to support this load. Prevent.

(Embodiment) An embodiment of the present invention will be described below with reference to the accompanying drawings.

In FIGS. 1 and 2, reference numeral 1 denotes a camshaft which is rotationally driven in synchronization with the engine. The camshaft 1 is provided with one valve opening cam 2 on the extension of the valve 4 and this valve opening cam. Two
Two cams 3 for closing the valve are formed so as to sandwich the cam.

A tappet 11 is interposed between the top of the valve 4 and the valve opening cam 2 and the valve opening cam 2 rotates to push down the tappet 11 while slidingly contacting the tappet 11, depending on the cam profile. The valve 4 is driven to open.

A bucket 7 through which the camshaft 1 is inserted is connected to an end of the valve 4 via a retainer 5. As shown in FIG. 3, four protrusions 8 are formed around the retainer 5, while the cylindrical bucket 7 is formed with a recess 9 that fits into each protrusion 8 by rotating in the circumferential direction. To be done. The retainer 5 is fitted into the groove portion 10 of the valve 4 via the split collet 6.

The bucket 7 is slidably supported by the cylinder head 12, and the tappet 11 is slidably fitted in the bucket 7. Bucket 7 and tappet 11 each have a valve 4
It is designed to slide in the axial direction.

The bucket 7 is located above each valve closing cam 3, and two guide portions 13 are integrally formed.
A cylindrical plunger 14 is slidably fitted into the shaft 3. Each plunger 14 is in sliding contact with each valve closing cam 3.

The bucket 7 is formed with a partition wall portion 15 slidably fitted inside the plunger 14, and a high-pressure oil chamber 16 is provided between the plunger 14 and the partition wall portion 15, and the partition wall portion 15 and the bucket 7 are provided.
A low pressure oil chamber 17 is defined between the ceiling portions 25 of the. A check valve 18 is interposed in the partition member 15, and the check valve 18 opens for hydraulic oil that is about to flow from the low pressure oil chamber 17 into the high pressure oil chamber 16.

Reference numeral 19 in the drawing denotes an oil gallery formed on the cylinder head 12, and pressurized oil is introduced from an oil pump (not shown). Pressurized oil from the oil gallery 19 is supplied to the low-pressure oil chamber 17 through a through hole 20 formed in the bucket 7.

With this configuration, the valve 4 is lifted from the valve seat 26 and then closed for valve closing by pushing down the tappet 11 while the valve opening cam 2 slides on the tappet 11 as the camshaft 1 rotates. By pushing up the bucket 7 while the cam 3 slidably contacts the plunger 14, the valve 4 is forcibly seated on the valve seat 26,
The valve 4 is opened and closed by a lift curve as shown in FIG.

From the low pressure oil chamber 17 through the check valve 18 to the high pressure oil chamber 16
Since the plunger 14 is always in sliding contact with the valve closing cam 3 by the hydraulic pressure introduced to the valve, the clearance with the valve closing cam 3 is always adjusted to 0, and the flap of the valve 4 is prevented.

The acceleration of the valve 4 is as shown by the broken line in FIG.
In the vicinity of the maximum lift amount of the valve 4 in the opening direction at the rotation angle of the first half (A part in the drawing) where the lift amount increases and the latter half (B part in the drawing) where the lift amount decreases Then
The acceleration of the valve 4 is reversed in the closing direction by the inertial force of the bucket 7 and the valve 4.

When the acceleration of the valve 4 is reversed, the load acting on the plunger 14 from the valve closing cam 3 also increases. At this time, the check valve 18 of the plunger 14 is closed and the high pressure oil chamber 16
By increasing the hydraulic pressure of the valve 14, the movement of the plunger 14 is locked to prevent the valve 4 from overlifting.

When the lift of the valve 4 is 0, the check valve 18 is opened, and the hydraulic pressure introduced from the oil gallery 19 to the high pressure oil chamber 16 via the low pressure oil chamber 17 causes the plunger 14 to apply a small load to the valve closing cam 3. The valve 4 is pressed against the valve seat 26 by being pressed with, and the sealing property of the combustion chamber 27 is ensured.

At this time, the lift curve of the valve opening cam 2 (shown by the solid line in FIG. 4) is slightly larger than the lift curve of the valve closing cam 3 (shown by the one-dot chain line in FIG. 4). Therefore, when the lift of the valve 4 is 0, the tappet 1
A minute gap is provided between the valve 1 and the valve opening cam 2 so as not to impair the sealing performance.

FIG. 5 and FIG. 6 show the driving torque of the camshaft in the present invention and the valve operating device having the conventional valve spring, respectively, in the shaded area. In the case of the conventional device, the valve spring is opposed to the valve spring in comparison with the present invention. The driving torque is increased by the amount. In the case of the present invention, as described above, the driving torque increases due to the inertial mass due to the acceleration and the amount that opposes the hydraulic pressure in the base circle, but the reduction in the driving torque due to the elimination of the valve spring is large, and the fuel consumption of the engine and The output is improved.

(Effects of the Invention) As described above, according to the present invention, in the valve forced opening / closing device of the internal combustion engine, the bucket through which the cam shaft is inserted is provided slidably in the axial direction of the valve, and the valve is connected to the bucket. A guide part that slidably fits a plunger that makes sliding contact with a valve-closing cam and a partition wall that separates the high-pressure oil chamber and the low-pressure oil chamber are formed inside and outside the plunger, and the low-pressure oil chamber is pressurized. Since the oil passage for guiding the oil is formed and the check valve for opening the oil that flows into the high pressure oil chamber from the low pressure oil chamber is provided, the clearance between the plunger and the valve closing cam is reduced by the oil pressure.
By adjusting to, it is possible to improve the sealing performance of the combustion chamber and prevent the valve from fluttering even at high rotation speed, which contributes to higher engine output and improved durability.

[Brief description of drawings]

1 is a sectional view showing an embodiment of the present invention, FIG. 2 is a perspective view of a camshaft, FIG. 3 is an exploded perspective view of a bucket and a retainer, and FIGS. 4, 5 and 6 are respectively. It is a diagram showing an action. 1 ... Casshaft, 2 ... Valve opening cam, 3 ... Valve closing cam, 4 ... Valve, 7 ... Bucket, 11 ... Tappet, 14 ... Plunger, 16 ... High pressure oil chamber, 17 ... …
Low-pressure oil chamber, 19 ... Oil gallery.

Claims (1)

[Scope of utility model registration request] 1. A camshaft, which is rotationally driven in synchronism with an engine, is provided with a cam for opening a valve that opens a valve and a cam for closing a valve that pulls up the valve. While a tappet for sliding contact is provided, a bucket that is slidable in the axial direction of the valve is connected to the valve by inserting a cam shaft, and a plunger that slides on the valve closing cam is provided and slides on the bucket. A guide part to be freely inserted and a partition part for partitioning the high pressure oil chamber and the low pressure oil chamber are formed inside and outside the plunger respectively, and an oil passage for guiding pressurized oil is formed in the low pressure oil chamber. A valve forced opening / closing device for an internal combustion engine, which is provided with a check valve for opening the oil that is about to flow into the high-pressure oil chamber.