JPS61169605A - Tappet of internal-conbustion engine - Google Patents

Abstract

PURPOSE:To always keep the normal open condition of a valve by slanting at a fixed angle the axis of a hydraulic tappet, to which one end of a cam follower is fixed, while the other end activates opening and closing of a valve during a cam rotation. CONSTITUTION:The upper end of a valve 4 which is energized to a valve closing direction by a valve spring 7 is engaged with one end of a cam follower 10 with the other end removably supported by a hydraulic tappet 9, and the valve 4 is activated by the rotation of a cam shaft 11 provided with a cam 11a which is engaged with a slipper face 10a of the cam follower 10. The joint (P) between the cam 11a and the above-mentioned slipper face 10a of a base circle is set with an offset to the side of the valve 4 from the center of the longitudinal direction of the cam follower 10. In this case, the angle between the axis (C) of a hydraulic tappet (g) and the axis (B) of the valve 4 is beta, bigger than the angle alpha, between the line of action (A) of pushing pressure and the axis (B), and preferably the angle beta is to match the angle theta, between the line of reaction (D) of the hydraulic tappet 9 and the axis (B).

Description

Detailed Description of the Invention A0 Object of the Invention (1) Industrial Application Field The present invention relates to a valve train for an internal combustion engine, and in particular, to a cam follower, one end of which is supported on a hydraulic tappet, and a valve closing mechanism that is connected to the other end of a cam follower by a valve spring. The cam of the camshaft is engaged with the upper end of the valve that is biased in the direction, and the cam of the camshaft is engaged with the slipper surface of the cam follower on the opposite side of the valve and hydraulic tappet, and the contact point between the cam and the slipper surface of the cam follower at the base circle is The cam follower is biased toward the valve side from the center in the longitudinal direction, and the line of action of the pressing force applied by the cam to the cam follower at the contact point is inclined by a certain angle α with respect to the axis of the valve.

Here, by deviating the contact point between the cam and the slipper surface of the cam follower from the longitudinal center of the cam follower toward the valve side, it is possible to minimize the pressing force applied from the cam to the cam follower while giving the valve as large a valve opening lift as possible. In addition, the line of action of the pressing force of the cam on the cam follower is tilted at a certain angle α with respect to the axis of the loop.When the cam opens and closes the valve, the pressing force from the cam to the cam follower and the line between the two are This is to make the line of action of the resultant force with the frictional force parallel to the axis of the valve, and to efficiently transmit the valve opening force to the valve.

(2) Prior Art Conventionally, in such a valve train, as shown in FIG. 2, the axis C of the hydraulic tappet 9 is similar to the line of action A of the pressing force FI of the cam 11α on the cam follower 10 in the base circle. ,
It is inclined at a constant angle α with respect to the axis B of the valve 4.

The hydraulic tappet 9 is therefore arranged parallel to the line of action A of the force Fl.

(3) Problems to be Solved by the Invention In such conventional valve train systems, valve closing failure occurs at low temperatures, which often results in starting failure and a drop in output due to a drop in pressure in the combustion chamber.

The cause of this is when the camshaft eccentrically moves toward the cam follower when the valve is closed due to slight center runout or deflection of the camshaft.
This is because the hydraulic tappet senses the eccentricity as the lift action of the camshaft and presses on it, causing the cam follower to swing toward the valve opening side.

In order to avoid such inconveniences, general hydraulic tappets have a structure that contracts when a load of a predetermined value or more is applied. However, the contraction characteristics of a hydraulic tappet are determined not only by the stroke of the check valve in the hydraulic tappet and the oil leakage gap around the plunger, but also by the magnitude of the load to which the hydraulic tappet is subjected, the loading speed, and the oil temperature in the hydraulic tappet. Since the oil pressure changes greatly, when the temperature is low or the viscosity of the oil is high, the amount of contraction of the hydraulic tappet is small, and the eccentricity of the camshaft cannot be fully absorbed, which may cause the valve to be slightly pushed open.

The following measures are usually taken to deal with such problems.

■ Increase the set load of the valve spring and make it difficult to open the knob.

■ By increasing the stroke of the check knob in the hydraulic tappet or by increasing the volume of the hydraulic chamber,
Increase the amount of contraction of the hydraulic tappet.

■ By moving the contact point between the cam and cam follower closer to the hydraulic tappet side (reducing the lever ratio), the load acting on the hydraulic tappet is increased.

However, countermeasure (■) increases the frictional force between the cam and cam follower, which not only accelerates their wear but also reduces the output performance of the engine. If the amount becomes too large, the opening stroke of the valve will be reduced, resulting in a decrease in output performance. Countermeasure (2) will not only increase the load on the cam, which will be disadvantageous in terms of wear resistance of the cam and cam follower, but also reduce the cam shape. Both measures have drawbacks, such as manufacturing errors that appear noticeably in the lift characteristics of the valve.

The present invention was made in view of the above circumstances, and it is possible to increase the thrust load acting on the hydraulic tappet as much as possible without increasing the set load of the valve spring or changing the lever ratio of the cam follower, thereby increasing the hydraulic pressure even at low temperatures. It is an object of the present invention to provide the above-mentioned valve operating device in which the tappet contracts to absorb eccentric movement of the camshaft, thereby ensuring a normal valve closing state of the valve.

B1 Structure of the Invention (1) Means for Solving the Problems In order to achieve the above object, the present invention provides an angle α in which the axis of the hydraulic tappet is oriented in the same direction as the line of action of the pressing force with respect to the axis of the valve. It is characterized by being inclined at a larger angle β.

(2) Effect According to the above configuration, the thrust load applied from the cam follower to the hydraulic tappet is equal to or extremely close to the reaction force exerted by the hydraulic tappet on the cam follower.

Therefore, when the camshaft is eccentric toward the cam follower due to core runout or the like when the valve is closed, a large thrust load is applied from the cam follower to the hydraulic tappet, which contracts the hydraulic tappet and effectively corrects the eccentricity of the camshaft. can be absorbed and ensure the normal closed state of the valve.

(3) Embodiment An embodiment of the present invention will be described below with reference to FIG. 1. A cylinder head 1 of an internal combustion engine has a combustion chamber 2 and an intake (exhaust) port 3 opening into the combustion chamber 2. The intake (exhaust) port 3 is opened and closed by a valve 4.

The valve 4 is supported by the cylinder head 1 via a valve guide 5 so as to be able to move up and down, and is driven by a valve train 6.

The valve train 6 includes a valve spring 7 that is compressed between a retainer 4α attached to the upper end of the valve 4 and the cylinder head 1 and biases the valve 4 in the closing direction, and a support hole of the cylinder head 1. A hydraulic tappet 9 is attached to the valve 8, and the base end is swingably supported by the hydraulic tappet 9, and the distal end is supported by the valve 4.
A cam follower 10 that is engaged with the upper end, and a slipper surface 1 that is supported by the cylinder head 1 and rotationally driven by a crankshaft (not shown) and formed on the upper side of the cam follower 10.
0α and a cam shaft 11 that engages a cam 11α.

The hydraulic tappet 9 is connected to a cylinder 20 as usual,
The main component is a plunger 22 that slides on the inner peripheral surface of the cylinder and defines a hydraulic chamber 21 therein.The cylinder 20 is fitted into the support hole 8 of the cylinder head 1, and the plunger 22 is attached to the outer end of the cylinder The spherical end 22α is engaged with the spherical recess 10b at the base end of the cam follower 100.

The plunger 22 is formed with an oil reservoir chamber 23 and a valve hole 24 that communicates the oil reservoir chamber 23 with the hydraulic chamber 21.
The oil reservoir chamber 23 communicates with an oil supply passage 27 bored in the cylinder head 1 via an oil hole 25 on the side wall of the plunger 22 and an oil hole 26 on the side wall of the cylinder 20, and oil is sent from the oil supply passage 27. Always filled with reason.

A knot-shaped knob cage 28 is fitted into the inner end of the granger 22, and a spherical check valve 29 that opens and closes the valve hole 24 is inserted into the knot-shaped knob cage 28. The check valve 29 opens when the pressure in the hydraulic chamber 21 is reduced and closes when the pressure increases.

Furthermore, a push-up spring 31 is housed in the hydraulic chamber 21 and urges the plunger 22 to protrude above the cylinder 20 .

As the camshaft 110 rotates, the cam 11α applies a pressing force to the slipper surface 10α of the cam follower 10 due to its lifting action.
is pressed toward the hydraulic chamber 21, but the check valve 29 remains closed, so hydraulic pressure is generated in the hydraulic chamber 21, and the hydraulic pressure causes the plunger 22 to press down on the cam follower 10.
As a result of supporting the zero base end, the cam follower 10 is swung downward by the cam 11α using the spherical end 22α of the plunger 220 as a fulcrum, and opens the valve 4 against the force of the valve spring 7. During this time, the oil in the hydraulic chamber 21 slightly leaks from between the sliding surfaces of the cylinder 20 and plunger 22.

Next, when the cam 11α releases the lift action on the cam follower 10, the valve spring 7 pushes up the Z-lube 4 together with the cam follower 10 to return it to the valve closed position.

On the other hand, in the hydraulic tappet 9, the push-up spring 31 pushes up the plunger 22 to bring the slipper surface 10α of the cam follower 10 into contact with the cam 11α. In this way, the valve head gap, that is, the gap between the opposing portions of the cam follower 10, the cam 11α, and the valve 4 is eliminated.

Then, when the pressure in the hydraulic chamber 21 is reduced due to the push-up action of the push-up spring 31 against the plunger 22, the check valve 29 opens, so that the oil in the oil reservoir chamber 23 is supplied to the hydraulic chamber 21 through the valve hole 24, and the oil pressure is The amount of oil leaked from the chamber 21 is supplemented.

In such a valve train 6, the cam 11 at the base circle
(Contact point P between Z and slipper surface 11a of cam follower 10
is offset from the center in the longitudinal direction of the cam follower 10 toward the valve 4, and the line of action A of the pressing force of the cam 11α on the cam follower 10 at the contact point P is parallel to both lines A, It is inclined at a constant angle α so that the gap B widens toward the umbrella portion side of the bulb 4. In this case, the camshaft 11 moves the cam 11α to the slipper surface 10α so that the resultant force of the pressing force of the valve 4 against the cam follower 10 and the frictional force between the cam 11α and the cam follower 10 is applied to the axis B of the valve 4.
The valve 4 can be opened efficiently in the direction parallel to the above.

Furthermore, the axis C of the hydraulic tappet 9 is connected to the axis C of the valve 4, II! , 4 are inclined at an angle β larger than the angle α so that the space between the valves 4 and 4 widens toward the umbrella portion side of the bulb 4.

Here, the load that the hydraulic tappet 9 receives from the cam follower 10 side will be considered in comparison with a conventional device.

First, considering the equilibrium state of forces in the cam follower 10, the pressing force FI exerted by the cam 11α on the cam follower 10 is
is balanced by the resultant force of the reaction forces F2 and F3 that the cam follower 10 receives from the valve 4 and the hydraulic tappet 9, respectively.
The line of action A of the force F1, the line of action of the force F2 (ie, the axis B of the valve 4), and the line of action of the force F3 intersect at a point O. From this, the angle θ of the line of action of the force F with respect to the axis B of the valve 4 is uniquely determined, and is clearly larger than the angle α. In this respect, the conventional device is no different from the present invention.

However, in the conventional device, as shown in FIG. The axial load applied to the hydraulic tappet 9 from the thrust force Fy is Fy=F, ・cos α −F2...
...(A), and this force Fy becomes a force that tries to contract the hydraulic tappet 9.

In contrast, in the present invention, as shown in FIG. 1, the angle β between the axis C of the hydraulic tappet 9 and the axis B of the valve 4 is made to match the angle θ.
If the axis C of is made to coincide with the line of action of the reaction force F3, the thrust load F,) applied from the cam follower 10 to the hydraulic tappet 9 becomes as follows.

As is clear from the above equations (a) and (b), when β=θ, the thrust load Fy of the undercut hydraulic β tappet 9 can be increased by '/cos times compared to the conventional case. As a result, when the camshaft 11 is eccentric toward the cam follower 10 due to core runout or the like while the valve 4 is closed, the ability of the hydraulic tappet 9 to contract and absorb the eccentricity of the camshaft 11 is clearly superior to that of the conventional case. T-ru.

It is best to make the mounting angle β of the hydraulic tappet 9 coincide with the angle θ of the line of action of the reaction force F3, but in practice, if the relationship α〈β〈2α is satisfied, the desired result can be achieved. effect can be achieved.

C0 Effects of the Invention As described above, according to the present invention, the axis of the hydraulic tappet is inclined with respect to the axis of the valve in the same direction as the line of pressure action of the round four tappets at an angle β larger than the angle α. The thrust load acting on the hydraulic tappet from the cam follower can be increased as much as possible without increasing the set load of the cam follower or changing the lever ratio of the cam follower.As a result, the ability of the hydraulic tappet to absorb eccentric movement of the camshaft is improved. improve,
It is possible to ensure the normal valve closing state of the valve even at low temperatures.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional front view of a main part showing an embodiment of a valve train according to the present invention, and FIG. 2 is a front view of a conventional valve train. A... Line of action of the cam's pressing force, B... Axis of the valve,
C: Axis of hydraulic tappet, D: Line of action of force F3, Fl: Pressing force of cam against cam follower, F2
...Reaction force of the valve against the cam follower, F3...
Reaction force on the hydraulic tappet cam follower, Fy...
Thrust load of hydraulic tappet, P... Contact point of cam and cam follower at base circle, α... Axis line B and line of action A
Angle formed by the axis BC, β... Angle formed by the axis BC, θ...
Angle between axis B and line of action, 1...7 cylinder head, 4...valve, 6...valve train, 7...valve spring, 9...hydraulic tappet, 10... cam follower,
10cL...Suritsuno surface, 11...Camshaft, 11
a... cam

Claims (3)

[Claims] (1) The other end of the cam follower, one end of which is supported by the hydraulic tappet, is engaged with the upper end of the valve that is biased in the valve closing direction by the valve spring, and the cam is attached to the slipper surface of the cam follower on the opposite side of the valve and the hydraulic tappet. The cam of the shaft is engaged, and the contact point between the cam and the slipper surface of the cam follower at the base circle is shifted from the longitudinal center of the cam follower toward the valve side, and the line of action of the pressing force applied by the cam to the cam follower at the contact point is In a valve train for an internal combustion engine, the axis of a hydraulic tappet is inclined at a certain angle α with respect to the axis of the valve in the same direction as the line of action of the pressing force with respect to the axis of the valve at an angle β larger than the angle α. A valve train for an internal combustion engine, characterized by: (2) In what is stated in claim (1),
A valve train for an internal combustion engine, wherein the angle β is made to match an angle θ between a line of action of a reaction force exerted on a cam follower from a hydraulic tappet and an axis of a valve. (3) In what is stated in claim (1),
A valve train for an internal combustion engine, wherein the angle β is set to be smaller than twice the angle α.