JPS60108513A - Cam structure in valve forcedly opening and closing mechanism in internal-combustion engine - Google Patents

Abstract

PURPOSE:To reduce a shock accompanied with jumping of a rocker arm slipper from a valve closing cam to a valve opening cam, by setting the point of the jumping in a steeply inclined part before a point of inflexion of a cam shape. CONSTITUTION:The curvature of a valve closing cam from the maximum lift point PE thereof to the jump starting point PD of a slipper on the cam curved line D of the valve closing cam, in changed in the direction in which the clearance with respect to the cam curved line A of a valve opening cam gradually increases. Further, the jump starting point PD is set nearer to the maximum lift side than a point PB of inflexion on the cam curved line B of the valve closing cam, and as well the shifting point of the slipper to the cam curved line A of the valve opening cam is set nearer to the maximum lift side than a point PA2 of inflexion on the curved line A of the valve opening cam. With this arrangement the shifting part is in a steeply inclined position, the slipper may be grounded without impact force being generated in the cam surfaces.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cam structure in a forced valve opening/closing device for an internal combustion engine.

Conventionally, slippers of a valve-opening rocker arm and a valve-closing rocker arm are brought into sliding contact with the cam surfaces of a rotating valve-opening cam and a valve-closing cam. A valve forced opening/closing device for an internal combustion engine is known in which an intake valve or an exhaust valve can be forcibly opened and closed by the swinging motion of these two-end hook arms.

In such a forced valve opening/closing device, it is ideal to set the clearance between the valve opening cam and the valve closing cam, that is, the distance between the cam curves of both cams, to zero, but the camshaft, rocker arm, etc. Considering the current production technology and costs in terms of machining and assembly accuracy, it is actually difficult to reduce the clearance to zero by increasing the accuracy of each part. Cam curve A of the valve opening cam as shown in the figure
The actual situation is that a certain clearance Δy is provided between the cam curve B of the valve-closing cam and the cam curve B of the valve-closing cam.

These cam curves A and B each consist of three types of curves: a cam profile curve A, a ramp curve (buffer curve) opening, and a curve C that connects these two curves A and the opening. A cam curve A like this.

In a conventional forced valve opening/closing device using a valve opening cam and a valve closing cam with B, when the rotation of both the valve opening and closing cams is in a low speed rotation range, the biasing force of the spring Since the sliding surface of the slipper of the valve opening rocker arm is pressed against the cam surface of the valve opening cam, the valve lift curve of the intake or exhaust valve is.

The cam curve A of the intermediate valve cam in FIG. 1 traces the same trajectory over the entire range of the cam curve A.

Next, when the rotation of both cams is in the medium speed range, the inertial weight of the rocker arm and poppet valve acts instead of the spring that biases the intake valve or exhaust valve in the valve closing direction. The valve lift curve of the exhaust valve becomes curve C shown by the solid line in FIG. That is, through the vertical axis y indicating the lift amount of the cam curves A and B of both cams, go to the range of the climb on the left side of Fig. 2, that is, from the minimum lift point closest to the cam rotation center to the maximum lift point farthest In the range, the slipper of the rocker arm follows the same trajectory as the cam curve A of the valve opening cam from the ramp curve opening of the cam curve A to the curve C connecting the cam profile curve A and the ramp curve opening. After that, the cam curve A of the valve opening cam is
In the unfolded state, the FIfi line and cam profile [
An inflection point near the boundary with 11a (a point where the acceleration of the cam curve shifts from the plus side to the minus side or the opposite direction,
In other words, the point where the curvature changes in the opposite direction) begins to shift to the cam curve B of the valve-closing cam near PA, and the maximum lift point of the cam curve B of the valve-closing cam (the point farthest from the center of rotation of the cam) The transition of the valve-closing cam to the cam line B of cam a11 is completed in the vicinity of a point PC in front of PE in the rotational direction, and from the point PC to the maximum lift point PE of the cam curve B of the valve-closing cam and the point shown in FIG. The cam profile curve I in the developed state of the cam curve B of the valve-closing cam in the range of descent on the right side of the vertical axis y, that is, in the range from the maximum lift point farthest to the minimum lift point closest to the rotation center of the cam. The inflection point near the boundary between Pa and curve C (the point where the acceleration of the cam curve shifts from the plus side to the minus side or the opposite direction, that is, the point where the curvature changes in the opposite direction) , the cam curve A of the valve opening cam is returned to the vicinity of the hind leg inflection point PB, which follows the same trajectory as the cam curve B of the valve closing cam.
The transition of the valve-opening cam to the cam curve A is completed near the point PAI near the boundary between curve No. 1 of the cam curve A of the valve-opening cam and the ramp curve opening, and the transition to the cam curve A of the valve-opening cam is completed at the point F.A.I.
The curve C of the cam curve A of the valve opening cam and the ramp curve end follow the same trajectory as the cam curve A of the valve opening cam.

Furthermore, when the rotation of both cams reaches a high speed range, the inertial weight of the rocker arm and poppet valve acts greatly, so that the valve opening cam changes from the inflection point PB of the cam curve B of the valve closing cam in Fig. 2. When the slipper of the rocker arm moves to point FAI on the cam curve A, the area near the point PAL has the largest change in acceleration in the entire cam curve, and is at the inflection point P8.
As a result of the energy acting strongly on the cam surface during the transition of the slipper from point PAI to point PAI, the transition state to point PAI is accompanied by an impact, and the transition to point PAI is not performed smoothly, causing the slipper to move from point F As a result, the cam fluttering between the clearances of the cam curves A and B of the same cam, causing a valve bounce phenomenon, which is harmful to the strength of the valve train and the performance of the internal combustion engine. there were.

The present invention was made in view of the above circumstances, and aims to improve the performance and durability of an internal combustion engine by reducing the valve bounce phenomenon that occurs in the high rotation range. By sliding the slippers of the valve-opening rocker arm and the valve-closing rocker arm on the cam surfaces of the valve cam and valve-closing cam, the intake valve or exhaust valve is forcibly closed by the rocking motion of these double-ended lock arms. In a forced valve opening/closing device for an internal combustion engine, the slipper of the rocker arm determines the jump start point when transitioning from the cam surface of the valve-closing cam to the cam surface of the valve-opening cam. The curvature of the cam curve of the valve-closing cam is set to be offset toward the front in the rotational direction from the inflection point where the curvature changes in the opposite direction in the deployed state, and the slipper of the jumped Lonca arm is set to the cam surface of the valve-opening cam. A valve for an internal combustion engine, characterized in that a point at which the cam curve of the valve opening cam changes to the front side in the rotational direction from an inflection point at which the curvature of the cam curve of the valve opening cam changes in the opposite direction in the deployed state. The present invention provides a cam structure for a forced opening/closing device.

An embodiment of the present invention will be described below with reference to FIGS. 3 to 5. In the present invention, the same parts in the drawings are denoted by the same reference numerals, and detailed explanation thereof will be omitted. FIG. 3 is a longitudinal sectional view of a forced valve opening/closing device for an internal combustion engine equipped with the cam structure of the present invention, and FIG. 4 is a plan view thereof. In both figures, 1 is an intake valve, 2 is an exhaust valve, and each of these valves 1, 2
are forcibly opened and closed by the respective valve forced opening/closing devices 3 and 4.

Note that since the forced valve opening/closing devices 3 and 4 of both valves have the same structure and function, the forced valve opening/closing device 3 of the intake valve 1 will be explained, and the forced valve opening/closing device @4 of the exhaust valve 2 will be explained with reference to the drawings. The same parts are given the same reference numerals and their explanations will be omitted. The forced valve opening/closing device 3 has a valve opening cam 6 and a valve closing cam 7 arranged on the outer periphery of a rotating camshaft 5 in the axial direction thereof. The valve opening cam 6 and the valve closing cam 7 have cam curves that correspond to the valve lift curve shown by the solid line in FIG.

That is, the valve opening cam 6 has a cam curve A that sets a valve lift curve using cam specifications effective for expected performance of the internal combustion engine, similar to the conventional cam curve A.

On the other hand, the valve-closing cam 7 has a cam curve that is the same as the conventional cam curve B, with a part modified, in order to eliminate the valve bounce phenomenon in the high-speed rotation range. More specifically, the cam curve of the valve-closing cam 7 is such that when the slipper of the rocker arm moves from the cam surface of the valve-closing cam 7 to the cam surface of the valve-opening cam 6, the jump start point PD is set to the valve-closing cam 7. It is set so as to be offset from the inflection point PB of the cam curve B in the same portion as in the conventional art in the rotational direction, that is, toward the maximum lift point PE of the cam curve B. Also, the point where the slipper of the rocker arm jumps from the jump start point Po of the cam curve of the valve closing cam 7 and transfers to the cam curve A of the valve opening cam 6 is defined as the cam curve A of the valve opening cam 6.
Before the inflection point P A 2 in the rotational direction, that is, the cam curve A
The valve closing cam 7 is deviated toward the maximum lift point Pp side.
The valve closing cam 7 is divided into four equal parts of the cam rotation angle between the inflection point PB and the maximum lift point PE of the cam curve B.
It is set within the range of the first area E counting from the inflection point Pe. The cam curve of the corrected portion of the valve closing cam 7 is determined based on the curvature of the second range between the highest lift point PE and the jump start point Pa of the cam curve B of the valve closing cam 7. The clearance with respect to the cam curve A of No. 6 is changed to gradually increase.

With this configuration, when the slipper of the rocker arm moves from the cam surface of the valve-closing cam 7 to the cam surface of the valve-opening cam 6, the slipper that has jumped from the jump start point moves to the cam surface of the valve-opening cam 6. Since the setting position of the point where the slipper moves to the cam surface is at a steep slope position, no impact is generated when the slipper moves to the cam surface of the valve opening cam.

A slipper 9 of the valve-opening rocker arm 8 is in sliding contact with the cam surface of the valve-opening cam 6, and a slipper 11 of the valve-closing rocker arm JO is in sliding contact with the cam surface of the valve-closing cam 7. These double-ended hook arms 8.degree. 10 are rotatably attached to a common shaft 12.

The double-ended hook arms 8 and 10 are interlocked with each other via an adjustment bolt 13.

An end 8a of the valve opening rocker arm 8 opposite to the slipper 9 is connected to the upper end of the intake valve 1 via an adjustment collar 14 and an adjustment nut 15. 16 is intake valve 1
and a spring that biases the exhaust valve 2 in the valve closing direction; 17 is a guide tube for the intake valve 1 and exhaust valve 2; 18 is an intake port that connects the intake passage 1;
9, and 20 is an exhaust port that communicates with an exhaust passage 21. 22 is a cylinder of an internal combustion engine, and a piston 23 is fitted inside the cylinder. 24 is a cylinder head, 25 is a cylinder head cover, and 26 is a lid fitted into the window hole 25a of the cylinder head cover 25.

Next, the operation of the forced valve opening/closing device 3 for the intake valve 1 having the cam structure of the present invention will be explained. As the camshaft 5 rotates, the large diameter portion of the cam surface of the valve-closing cam 7 comes into sliding contact with the slipper 11 of the valve-closing arm 10.

The valve-closing roller force arm 10 rotates counterclockwise in FIG. 3 about the shaft 12, and presses the valve-opening rocker arm 8 counterclockwise in FIG. 1 via the adjustment bolt 13.

At this time, since the small diameter portion of the cam surface of the valve opening cam 6 is in sliding contact with the slipper 9 of the valve opening rocker arm 8, the rotation of the valve opening rocker arm 8 in the counterclockwise direction in FIG. If the valve opening rocker arm 8 is allowed to rotate counterclockwise in FIG. 1 about the shaft 12, the intake valve 1 is pulled up and the intake port 8 is closed.

Next, when the large diameter portion of the cam surface of the valve opening cam 6 comes into sliding contact with the slipper 9 of the valve opening rocker arm 8, the valve opening rocker arm 8 is pushed up and rotated clockwise in FIG. 1 to close the intake valve. 1 against the biasing force of the spring 16, and press down the intake port 1.
Open 8.

At this time, since the small diameter portion of the cam surface of the valve-closing cam 7 is in sliding contact with the slipper 11 of the valve-closing rocker arm 10, the pressure applied to the valve-closing rocker arm 10 via the adjustment bolt 13 causes the Rotation of the valve closing rocker arm 10 in the clockwise direction in FIG. 1 is permitted.

In the above action, the curvature between the maximum lift point PE of the cam curve of the valve-closing cam 7 and the jump start point PD of the slipper of the rocker arm on the cam curve of the valve-opening cam 6 is controlled by the valve-opening cam. The clearance with respect to the cam curve of 6 is changed in the direction of increasing slightly, and the jump start point PD is set to be deviated from the inflection point PB of the cam surface B of the valve-closing cam 7 toward the maximum lift point side, and the slipper - is the valve opening cam 6
Cam curve A of the valve opening cam 6 at the point where it transitions to the cam curve A of
Since the inflection point PA2 is set to be deviated from the inflection point PA2 to the maximum lift point side, the part where the slipper of the 50-tsuka arm transitions from the valve-closing cam 7 side to the valve-opening cam 6 side becomes a steep slope position, and therefore the jump start point. The slipper that jumps from the cam surface will land immediately when an impact force is generated on the cam surface, so it can smoothly transition from the valve-closing cam 7 side to the valve-opening cam 6 side.
No valve bounce phenomenon occurs.

As mentioned above, the cam structure of the forced valve opening/closing device for an internal combustion engine of the present invention has a rocker arm for opening a valve and a slipper of a 40-arm for closing a valve slidingly connected to the cam surfaces of the cam for opening the valve and the cam for closing the valve, which rotate once. In a forced valve opening/closing device for an internal combustion engine, in which an intake valve or an exhaust valve can be forcibly opened and closed by the rocking motion of the two-end hook arm, the slipper of the rocker arm moves against the valve closing cam. The jump start point when transitioning from the cam surface to the cam surface of the valve-opening cam is biased toward the front side in the rotational direction from the inflection point where the curvature of the cam curve of the valve-closing cam changes in the opposite direction in the deployed state. The point where the slipper of the jumped rocker arm moves to the cam surface of the valve opening cam is set from the inflection point where the curvature of the cam curve of the valve opening cam changes in the opposite direction in the deployed state. Since it is set so as to be offset toward the front in the rotational direction, no impact is generated when the slipper of the rocker arm moves from the cam surface of the valve-closing cam to the cam surface of the valve-opening cam. This allows a smooth transition and therefore prevents the valve bounce phenomenon that occurs in the high rotation range.

It can improve the performance and durability of internal combustion engines.6

[Brief explanation of the drawing]

1 and 2 are diagrams showing valve lift curves using a conventional valve-opening cam and a valve-closing cam, and FIGS. 3 to 5 show an embodiment of the present invention. A vertical sectional view of a forced valve opening/closing device equipped with the cam structure of the invention, FIG. 4 is an open plan view,
FIG. 5 is a diagram showing a valve lift curve. DESCRIPTION OF SYMBOLS 1... Intake valve, 2... Exhaust valve, 3, 4... Valve forced opening/closing device, 6... Valve opening cam, 7... Valve closing cam,
8...Rocker arm for opening the valve, 10...Rocker arm for closing the valve, A...Cam curve of the cam for opening the valve, B, D...
Cam curve of the valve closing cam, Pa...Inflection point of the valve closing cam, Po...Jump start point, PA2...Inflection point of the valve opening cam, PE, PF...Maximum lift Point 2...Between the inflection point and the maximum lift point. Applicant Honda Motor Co., Ltd. Agent Patent Attorney Iihiko Watanabe Figure 4 6 Figure 5 shows yF (rotation angle)

Claims (1)

[Scope of Claims] 1. Swinging of these double-ended lock arms by slidingly contacting the slinters of the valve-opening rocker arm and the valve-closing rocker arm with the cam surfaces of the rotating valve-opening cam and valve-closing cam. In a valve forced opening/closing device for an internal combustion engine that is capable of forcibly opening and closing an intake valve or an exhaust valve by dynamic motion, the slipper of the rocker arm slides from the cam surface of the valve closing cam to the cam of the valve opening cam. The jumping start point when transitioning to the surface is set to be offset to the front side in the rotational direction from the inflection point where the curvature of the cam curve of the valve closing cam changes in the opposite direction in the deployed state. The point where the slipper of the jumped rocker arm moves to the cam surface of the valve opening cam is biased toward the front side in the rotational direction from the inflection point where the curvature of the cam curve of the valve opening cam changes in the opposite direction in the deployed state. A cam structure in a forced valve opening/closing device for an internal combustion engine, characterized in that the cam structure is configured to be set in a fixed position.