RU2391519C2 - Gas-distributing mechanism of internal combustion engine - Google Patents

Abstract

FIELD: engines and pumps.

SUBSTANCE: gas-distributing mechanism of internal combustion engine (ICE) includes distributing shaft, shell of pusher with spherical operating surface, a rod, beam mechanism and valve with contact spring. Profile of cams is as follows: Y-Y line of symmetry axis is drawn through O centre of initial circle of R radius. An arc is drawn from O centre with the radius equal to the sum of R radius and h height of valve lift. Symmetric arc lengths CY and YD are marked on the arc from Y-Y line, and they are equal to the half of the valve coverage angle. YOA and YOB angles equal to the half of the rotation angle of cam from the beginning of valve opening to its closing are marked from Y-Y line. AOB sector corresponds to cam operation from the beginning of valve opening to its closing. DOB sector is divided with lines drawn from O centre of initial circle into any quantity of equal elementary angles. On the continued part of OB radius there marked is h length which is divided into equal lengths corresponding to the number of equal elementary angles in DOB sector. Arcs are drawn with radii from O centre of initial circle to obtained points in h length till they cross the appropriate radial line limiting the next elementary angle in DOB sector. Crossing points of drawn arcs with the specified radial lines are connected with the curve passing through them. The obtained curve is lateral arc of DB cam profile. A and C are connected symmetrically to DB arc relative to Y-Y. Valve drive can be provided with elastic element in the form of plate spring with trapezoidal blades between the rod and bottom of pusher shell.

EFFECT: increasing the time of valve section, coefficient of filling the cylinders with incoming charge and cleaning degree of cylinders from waste gases, and slower wear of cam top and low level of operating inertia forces.

2 cl, 2 dwg

Description

The present invention relates to the field of engine manufacturing, namely to a gas distribution mechanism of an internal combustion engine.

The gas distribution mechanism of an internal combustion engine is widely known, containing valves with clamping springs, a camshaft with conical cams and a glass located between them with a spherical working surface, a rod and a rocker (see, for example, Prince Y.B. Barsky and others. "Design, Fundamentals of the theory and calculation of tractors "," Higher School "publishing house, Moscow, 1971, p. 46, Fig. 5.4).

Its disadvantage is that the tops of its cams are outlined by a small radius, in which the maximum opening of the valve is achieved only with one position of the cam, which limits the valve’s time-section and, accordingly, the coefficient of filling the cylinders with a fresh charge and the degree of purification of the cylinders from exhaust gases. In addition, high specific pressures acting on the tops of small radius cams contribute to their faster wear, which leads to a decrease in engine power and efficiency.

Its other disadvantage is the high level of inertia forces acting in it, which necessitate the use of valve springs pre-tightened by a tightening force, 5-7 times higher than the force of separation of the valve from the seat at the suction stroke, which leads to faster wear of all friction couples of the gas distribution mechanism .

The aim of the present invention is to remedy these disadvantages.

This goal is achieved in that the cam profile of the gas distribution mechanism is made with points of the start and end of the valve lift symmetrically located on the initial circumference relative to the plane of symmetry, contains a vertex defined by a radius equal to the sum of the radius of the initial circumference and the valve lift height, located symmetrically with respect to the symmetry plane of the profile in the limits of the angle of overlap of the valves and the side arcs that match the latter with the initial circle at points having common normals, the passage They are through the center of the initial circle, and the pusher glasses are made with built-in springs, which limit the inertia forces transmitted to the valve.

Each pusher cup contains two built-in springs, one of which is located between the bar and the guide of the pusher cup, and the second is between the bar and the bottom of the pusher cup.

The invention is illustrated by drawings, where in a diagrammatic embodiment it is shown: in Fig. 1 - the proposed cam profile and its construction, in Fig. 2 - the device of the pusher cup with integrated springs and its interaction with the camshaft cam.

Figure 1 marked:

h - valve lift to a fully open position;

point A - the point corresponding to the beginning of the valve opening;

point C is the point corresponding to the initial position of the valve in the fully open position;

point D - a point corresponding to the final location of the valve in a fully open position;

point B is the point corresponding to the end of valve closure;

AOS sector - a sector corresponding to the valve opening arc;

SOC sector - sector corresponding to the valve closing arc.

The profile of the cams is as follows: through the center O of the initial circle of radius R, a line Y-U is drawn corresponding to the plane of symmetry of the cam. An arc is drawn from the center of the initial circle O with a radius equal to the sum of the radius R of the initial cam circumference and the valve lift height h, on which symmetrical arc segments equal to half the valve overlap angle are laid off from the U-Y line, with the formation of the SOD sector with an arc of constant radius SD . Within the angle of the SOD sector, the valve is in the fully open position. The angles of UOA and UOV, equal to half of the angle of rotation of the cam from the beginning of opening the valve to its closure, are laid off from the U-Y line in both directions, with the sector AOB corresponding to the operation of the cam from the beginning of the opening of the valve to its closing. The DOM sector by lines drawn from the center O of the initial circle is divided by an arbitrary number of equal elementary angles. On the extension of the radius ОB, the segment h is laid out, which is divided into equal segments corresponding to the number of equal elementary angles in the DOM sector, while the radii from the center O of the initial circle to the points obtained on the segment h draw arcs to the intersection with the corresponding radial line bounding the next elementary angle in the sector of disabled children. The intersection points of the drawn arcs with the indicated radial lines are connected by a curve passing through them, to obtain a side arc of the cam profile of the DW. An arc, a symmetrical arc of the DW relative to the line U-U, connects points A and C.

With this construction of the cam profile, each angular movement of the cam by the elementary angle of the side cam profile corresponds to the same valve movement. If we assume that the speed of rotation of the cam shaft is constant, this corresponds to a constant value of accelerations obtained on the side surfaces of the cam, which is the smallest possible for the selected value of the angular sector of the SOD, within which the valve is in each fully open position for each cam cycle. The possible obtaining of higher accelerations and, correspondingly, higher inertia forces transmitted to the valve from the side surfaces of the cam is compensated by elastic elements built into the pusher barrel made in the form of springs, which provide a decrease in the inertia forces acting on the valve.

In some engine designs, for this purpose, a spring is installed between the guide of the pusher and the rod resting on the bottom of the pusher cup. This reduces the effect of inertial forces from the valve actuator by the amount of force compressing the spring brought to the valve, and reduces the stiffness of the valve springs, which reduces valve wear. At the same time, the wear on the tops of the cams operating in widely used engines at high specific pressure increases significantly due to the fact that the sum of forces begins to act on the cam - the compression force of the valve spring brought to the cam and the interaction force of the rod with the guide of the pusher cup.

The proposed device to reduce the inertia transmitted to the valve (Figure 2), includes a pusher cup 1, interacting with a cam 2, a spring 3, one end through a washer 4 and a retaining ring 5, resting on a guide 6 of the pusher cup, and the other through the ring 7 on the rod 8, interacting through a movable support 9 and a conical spring 10 with the bottom of the pusher cup 1. The conical spring is of greater stiffness than the spring 3. Preloading the springs by the estimated value of the valve unloading from the action of inertial forces they simultaneously tighten the springs 3 and 10 to the same force when installing the snap ring 5. This, due to the additional deformation of the spring 3, reduces the transfer of inertia to the valve without increasing the forces of interaction of the pusher 1 with the cam 2. This reduces the level of dynamic loads, transmitted to the valve, the maximum of which is achieved at the time of the start of the valve lift, due to the running of the cam profile on the pusher and the choice of the gap between the valve and the rocker. The selection of the characteristics of the spring 10 is carried out on the basis of obtaining the greatest effect from its effect on gas exchange in the engine cylinder in the range of high-speed engine operation from idle to revolutions corresponding to the engine speed at maximum power, guided by the following.

As a rule, they strive to obtain maximum engine power at the smallest engine size and weight, at higher engine speeds, and since this also increases the hydraulic resistance of the engine intake tract, the valve timing of the engine is also set from these conditions, which ensure that the pressure rises above the rated engine speed air or a combustible mixture in front of the intake valve above the residual gas pressure in the cylinder. With an increase in the load on the engine shaft, the cyclic fuel supply increases, and the engine shaft speed decreases, theoretically, in proportion to the square of the decrease in the engine shaft speed, and in fact, the inertial pressure of the combustible mixture decreases to a greater extent due to the resistance of the inlet tract before opening the inlet valve three times, with an increased pressure of residual gases when more fuel is burned in the cylinder. At the beginning of valve closure, the pressure of the residual gases in the cylinder exceeds the pressure of the gases in front of the inlet valve, and part of the residual gases from the cylinder enters the inlet tract, and then, with increasing vacuum in the cylinder, it is sucked into the cylinder together with the combustible mixture. The same thing happens when the engine is running in all partial modes and at idle.

The valve actuator with integrated elastic elements operates as follows. On the arc of the occipital part of the cam, made with a radius of the initial circle R, reduced by a value of 0.4-0.6 mm, the angular movement of the cam is carried out without lifting the pusher. The valve is in the closed position under the action of pressure springs. The value of the thermal gap in the valve actuator is provided automatically by the value of the specified gap between the tip of the rod 8 and its surrounding parts 7 and 9.

The pusher 1, which is in contact with the occipital part of the cam, goes to the working part of the profile, of the cam in a gently sloping section, the length of which sets the acceleration of the pusher cup, which deforms the spring 10 by a predetermined amount with an almost stationary rod 8. The pulse of additional acceleration of the pusher during its further sliding along the side profile of the cam is quickly eliminated by increasing deformation forces of the valve spring and spring 5, but during this time the acceleration pulse received by the pusher and leading to aderzhke beginning of the valve opening, provides a rapid opening of the valve directly with a larger opening it.

This valve operation limits the possibility of residual gases entering the intake manifold, reduces the throttling losses of the gases in the suction and exhaust valves, and provides greater energy for the air or fuel mixture to enter the engine cylinder and exhaust gas. The delay in opening the valve is compensated by the selection of the valve timing, which provides for its earlier opening.

When using a pusher cup in a valve actuator with two springs integrated in it, it should be borne in mind that the stroke of the rod is always less than the stroke of the pusher cup 10 and depends on the choice of the elastic characteristics of the springs used. The higher the stiffness of the spring 10, the greater the stroke of the rod approaches the stroke of the rod, rigidly interacting with the pusher cup. This difference is compensated by a corresponding increase in the height of the cam profile.

In another embodiment, a decrease in the maximum inertia force acting on the valve is provided by a single spring made, for example, of a trapezoidal plate with elastic petals, mounted between the movable support 9 of the rod 8 and the bottom of the pusher cup 1 without preliminary tightening, whose elastic properties up to maximum deformation, along with the length and steepness of the pusher exit to the beginning of the cam profile, they are set to provide a predetermined delay for the start of the movement of the rod 8 along the angle of rotation of the cam profile, which disappear when you select the height of the cam profile.

Such a timing device makes it possible to increase the exhaust gas flow rate, increase the air or combustible mixture intake rate into the cylinder, thereby increasing the valve time-section, not only by increasing the cam operating time, when the valve is fully open, but also due to its more efficient operation lateral surfaces of the cam, as well as improve the quality of the timing by reducing the possibility of exhaust gases penetrating the inlet tract, causing dilution of the air or combustible mixture entering the cylinder exhaust gases and the grinding of the fuel equipment located in the inlet tract and by reducing the power losses therein for throttling the inlet and outlet gases.

A decrease in the maximum inertia forces in the proposed timing is achieved by eliminating the hard interaction of the valve with its actuator when it is opened, installing between the movable support of the rod and the bottom of the pusher of the elastic element and performing a cycle of additional acceleration of the valve after delaying the start of its rise with relatively small elastic deformations of the valve spring.

Claims (2)

1. The gas distribution mechanism of the internal combustion engine, including a camshaft with conical cams, a pusher barrel with a spherical working surface, a rod, a rocker mechanism and a valve with a clamping spring, characterized in that the profile of the cams is made as follows: through the center O of the initial circle of radius R is drawn line Y-U, corresponding to the plane of symmetry of the cam, from the center of the initial circumference About a radius equal to the sum of the radius R of the initial circumference of the cam and the valve lift height h, pr an arc is drawn on which symmetrical arc segments equal to half the valve overlap angle are laid off from the U-U line, with the formation of the SOD sector with an arc of constant radius SD, within the angle of which the valve is in the fully open position, from the U-U line in both directions angles of UOA and UOV equal to half the angle of rotation of the cam from the beginning of the valve opening to its closure are postponed, with the sector AOW corresponding to the work of the cam from the beginning of the valve opening to its closure, the DOV sector by lines drawn from the center O started of a circle, is divided by an arbitrary number of equal elementary angles, on the continuation of the radius ОВ, a segment h is laid out, which is divided into equal segments corresponding to the number of equal elementary angles in the DOV sector, while arcs are drawn from the center О of the initial circle to the points obtained on the segment h to the intersection with the corresponding radial line, bounding the next elementary angle in the SAD sector, the intersection points of the arcs drawn with the indicated radial lines are connected passing through them with a curve to obtain a lateral arc of the cam profile of the DW, and points A and C are connected with a symmetrical arc relative to the U-Y line. 2. The gas distribution mechanism according to claim 1, characterized in that the valve actuator is made with an elastic element, for example, in the form of a leaf spring with trapezoidal petals located between the rod and the bottom of the pusher cup.

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