EP0705382B1

EP0705382B1 - Variable action arrowhead shaped cam lobe system

Info

Publication number: EP0705382B1
Application number: EP94908472A
Authority: EP
Inventors: Christos Valasopoulos
Original assignee: Individual
Current assignee: Individual
Priority date: 1994-03-03
Filing date: 1994-03-03
Publication date: 1998-07-15
Anticipated expiration: 2014-03-03
Also published as: EP0705382A1; KR0160202B1; WO1995023912A1; AU6155494A; DE69411743T2; KR960702049A; JPH08511600A; DE69411743D1

Description

FIELD OF THE INVENTION

The invention refers to a new system that provides the capability to an arrowhead shaped cam lobe to move gradually between a lower and an upper position, changing therefore gradually and successively the lifting of the valves of the respective cylinder of an Internal Combustion Engine (I.C.E.), with the purpose of improving the basic operational characteristics and the efficiency of the I.C.E.

BACKGROUND OF THE INVENTION

Systems that would reduce the disadvantages occurring in the operation of I.C.E., equipped with conventional camshafts, have been applied in a very limited extend and in certain I.C.E. so far.

Referring to the invention with Patent No DE 42 22 477 A1 which refers to a variable cam, which operates whether through its fixed cam segment or through the combination of fixed-movable segment, we observe that in this invention:

a) The hydraulic means for transmitting moving action to the cam, succeeds in moving the cam to the "out" position and returning it to the "in" position, with result the limiting of the torque and power improvement of the engine, only in certain positions.

b) It has serious tightness problems in the hydraulic pressure chamber, due to the size of the chamber, the complicated system, the necessary high hydraulic pressure for holding the cam on the "out" position, where the cam is forced down from the respective valve lifter.

c) The cams due to the increased solid mass, especially in the configuration FIG. 9, will develop during their operation serious problems from inertia forces.

Consequently the embodiment (Fig. 2,3) introduces a problematic operation and in any case does not achieves gradual change in the respective valve movement (Fig. 8). Specifically it is noted that chamber (23), (Fig. 9) is practically impossible to achieve complete tightness, as demanded, and the hydraulic pressure supplied by the engine lubrication system, is impossible to hold the movable part cam in the intermediate positions, mentioned in the documents of said application (Fig. 8).

d) Obvious manufacturing and assembling difficulties. (Fig. 2,3,9).

e) It cannot be applied to engines where the distances between the cams are limited, as for example with the engines V6 and V8 used by the auto industries in the U.S.A., CANADA, AUSTRALIA etc.

Referring to the invention with Patent No US-A- 3523465 which presents an adjustable cam shaft wherein an axially slidable cam shaft inside an elongated tubular hub has a series of inclined recesses therein receiving the inner ends of the lobes respectively inserted from the respective tubular hub openings. We note that these inclined recesses are configured as T-splines and the respective inner ends of the lobes are configured as T-slots. During the axial movement of the camshaft connected with the timing spur gear, it is obvious that this design and arrangement of said T-shaped recesses is able to achieve the movement of the respective movable lobes in a gradual way and consequently the gradual movement change of the respective valves.

It is also obvious that this design and configuration of inclined T-shaped recesses do not allow the successive change of the valve movement in the same cylinder, in order to achieve a smooth torque and power distribution of the engine in the whole r.p.m. range.

In our present application the respective inclined surfaces on the reciprocating shaft are simple ramps reversed in the shaft and sliding only on a ball which controls the tightness of a hydraulic chamber achieving the successive change in the gradual movement of valves in the same cylinder.

The present invention respectively is successful in:

a) Smooth and gradual raising and returning of a properly shaped cam lobe employing also the important advantage, concerning the valves of the same cylinder, of having the gradual change of the valve lifting of one valve to be preceded by a proper time space to the other, in such a way as to result in smoother distribution of torque and power of the engine in its r.p.m. range.

b) Complete tightness of the small required hydraulic pressure chamber, in the lower cylindrical portion of the cam lobe, where it is required only the supplied hydraulic pressure from the lubrication system of the engine, resulting in the application of the invention without any problem.

c) Safe and smooth raising of the cam lobe and resting on the cylindrical recess of the rotating shaft. Minimisation of load and inertia forces problems.

d) The present invention allows also the simple, fast and economical manufacturing of the cam and the other elements and ease of assembling as it is obvious from the following drawings.

e) It is applied in all existing I.C.E. types without any need for design change.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1: Shows views of the rotating shaft.

FIG. 2: Shows the above mentioned system with the cam lobe on its initial position.

FIG. 3: Shows the above mentioned system with the cam lobe on its final position.

FIG. 4: Shows views of the longitudinal reciprocating shaft.

FIG. 5: Shows a special configuration of the above mentioned shaft.

FIG. 6: Shows several views of the arrowhead shaped cam lobe.

FIG. 7: Shows a special design of the cam lobe.

FIG. 8: Shows a mounting system of cam lobes on a simple construction allowing the grinding in pairs.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the

Drawings

1,2,3,4,6 we observe that the system consists of the rotating shaft (1), which is equipped with the arrowhead shaped movable cam lobes (2), the longitudinal reciprocating shaft (3), the ball (4) and the spring (5). The cam lobe has a special cylindrical configuration on its lower end, so that it can be assembled in the respective cylindrical opening of the shaft (1) in a secure way. It has also a longitudinal opening through which the shaft (3) passes. In the inside of the opening the inclined ramp (6) is shaped, and corresponds with the slope of the ramp (7) on shaft (3). This shaft has an appropriate number of longitudinal grooves, through these grooves the circulation under pressure of the hydraulic fluid, used also for I.C.E. lubrication, is eased, so that the areas on shaft (1) equipped with the cam lobes are always under hydraulic pressure, which pressure is also supplied for the lubrication of the engine. This pressure is adequate in any case to overcome the reaction of spring (5) and the hydraulic fluid passes through the vertical hole (11) of the lobe and floods the chamber (9) between the shaft (1) and the cam lobe (2). In this way the cam lobe (2), forced by the fluid, is raised until the lobe ramp (6) coincides with the ramp (7) of the shaft (3). In this position the lobe remains raised thanks to the following mechanism:

During the time that the cam lobe is not in contact with the respective valve lifter the lobe (2) and the shaft (3) remain in contact since the ramps (6) and (7) coincide. In this case the ball (4) is completely inside the vertical hole (11) (spring retracted) simply touching the ramp (7). As soon as the lobe comes in contact with the respective valve lifter, a force is applied on it greater that the force applied by the hydraulic fluid in chamber (9), and momentarily it gives in. This retreat results in the upward movement of the ball (4), through the spring (5), and the complete fit on the specially shaped, like a seating, upper part of hole (11), making the whole space tight and at the same time capturing the hydraulic fluid inside the chamber (9), so that no further retreat of the lobe is possible during the hole time of its contact with the valve lifter (Fig. 6).

Movement of the shaft (3) towards the direction (a) (Fig. 3) results in pushing back to a certain distance the ramp (7) from ramp (6). Respectively the under pressure hydraulic fluid passing through the vertical hole (11) forces the cam lobe upwards until the ramps (6) and (7) come again in contact. In this way and according to the mechanism we described earlier the lobe is secured in a new position during its contact with the respective valve lifter. This procedure can be repeated until the cam lobe takes its upper position, depending on the configuration (length, sloped) of the ramp (7) on shaft (3).

The gradual retraction of the lobe to its initial position is achieved by the gradual movement of the shaft (3) towards the opposite direction. Indeed this movement results initially in pushing the ball (4) by ramp (7) which penetrates inside the hole (11), and further more in pushing the ramp (6), with the final result the whole lobe to move downwards. The hydraulic fluid in chamber (9) can escape through the vertical hole (11), since the ball (4), being already pushed by the ramp (7) does not rest on the upper "seating" end of hole (11), and does not provide therefore any tightness in the chamber (9). In any intermediate position the lobe is secured by the mechanism already described (Page 4 lines 10 - 20).

Referring to Fig. 3 we observe a special configuration of the longitudinal shaft (3), which is foreseen so that the change in lifting of a valve through the ramp (7) to follow, at a proper time lapse, the change in lifting of another valve of the same cylinder through the ramp (7a), so that a smoother distribution of the torque and power of the engine is achieved through the whole range of its r.p.m. range.

Referring to Fig. 7 we see a configuration of the cam lobe consisting of two parts assembled together with a tight fit for reasons of manufacturing ease. The above mentioned cam lobe properly shaped, cooperates as its different positions completely with the cylindrical base of the rotating shaft (1). Obviously the above mentioned cam lobe can cooperate with fixed cams too.

Concerning the grinding of cams, as it is well known, this is executed with the method of copying tool machines through the respective PROFILE - MASTER CAM. With conventional cams the grinding procedure is executed on one cam each time (Fig. 8,b2) through the PROFILE - MASTER CAM (Fig. 8,b1). On the other hand with the cam lobe configuration of the present invention the grinding procedure is executed in pairs of cam lobes mounted on a simple construction (Fig. 8, a2, a3) through the special PROFILE - MASTER CAM (Fig. 8, a1) which method is obviously faster and more economical, than the conventional method usually applied.

Claims

Variable action arrowhead shaped cam lobe system comprising: a rotating shaft (1) with an axial longitudinal hole (Fig. 1) and transverse cylindrical opening on shaft (Fig. 1, section A-B), a first movable cam lobe (2) properly shaped to an arrowhead figure, a second cam lobe similar to the first cam lobe (2), a cylindrical arrow axle (Fig. 7) mounted on said arrowhead cam lobe, which inserted in said transverse cylindrical opening (Fig. 1) of rotating shaft (1) is able to move, a reciprocating shaft (3) moved by any means inside of said longitudinal hole, having on its surface two sliding ramps (7, 7a), corresponding to these two cam lobes, the inner surfaces of the movable lobe wings do not embrace the cylindrical surface of the cam shaft and do not come in contact with the said surface, characterized in that said cylindrical arrow axle has configured on its midlength an horizontal longitudinal opening through which the reciprocating shaft (3) slides, a ball (4) on spring (5) is placed inside the vertical hole (11) in the lower cylindrical part of said arrow axle, the two sliding ramps (7,7a) of said reciprocating shaft are inclined surfaces reversed to the contact surfaces of the movable cam lobe, a hydraulic action being required for the operation of said system whereby only the hydraulic pressure of hydraulic fluid supplied by the engine lubrication system is required, wherein said hydraulic fluid flowing through the longitudinal camshaft bearing lubrication bore floods a hydraulic chamber shaped in the lower cylindrical part of the camshaft transverse cylindrical opening (Fig. 1, section A-B), and wherein the ball on a spring in the lower cylindrical part of said arrow axle (Fig. 6,7) with the help of the reciprocating reverse ramp of said reciprocating shaft blocks and releases said hydraulic fluid, and wherein said combination of mechanical and hydraulic action, allows the gradual and successive change of the two respective valves movement in the same cylinder, through the successive arrangement of the two reverse ramps of said reciprocating shaft.
Variable action arrowhead shaped cam lobe system according to claim 1 wherein the cylindrical arrow axle is secured on the movable arrowhead shaped cam lobe (Fig. 7) characterized in that the retraction of said cylindrical arrow axle with the movable cam lobe of the cam shaft through the transverse cylindrical opening (Fig. 1) is the result of the mechanical and hydraulic action applied solely on the cylindrical base of said arrow axle (Fig. 3).
Variable action arrowhead shaped cam lobe system according to claim 1 characterized in that a variable action hydraulic chamber (9) is shaped between the lower circular surface of the arrow axle base and the circular surface of the base of the cam shaft transverse opening (Fig. 1), said chamber is successively being tight through the ball on spring blocking completely the flow of hydraulic fluid inside said variable chamber (9), said tightness through the ball being in control by the mechanical action of the reverse ramps on the reciprocating shaft does not allow the retraction of the movable cam lobe due to the application on said cam of the high loads by the valve train action during engine operation.
Variable action arrowhead shaped cam lobe system according to claim 1 characterized by the fact that the grinding process is possible to be applied on pairs of lobes mounted axially on the recess of a simple construction where the whole operation is done according to the method followed by the copying machines through the respective PROFILE - MASTER CAM, this method being obviously faster and more economical from the cam grinding of the conventional camshafts used by the autoindustry and general industry.
Variable action arrowhead shaped cam lobe system according to claim 1 characterized in that the reciprocating shaft inside the longitudinal camshaft lubrication bore has longitudinal grooves through which the hydraulic fluid supplied for the bearing lubrication flows, said lubrication fluid is intended also for the operation of the present system in combination with the mechanical action of the reciprocating shaft, the slide ramps on the surface of said shaft are reversed as to the contact surface of the movable lobe (Fig. 5), said ramps are successively arranged in pairs in a selected distance between them being in respect to the two valves of the same cylinder, the arrangement of said ramps offers an advantageous capability, in that the gradual movement of one valve precedes to a proper time lapse, the gradual movement of the other valve in the same cylinder, said successive movement allows the smooth engine power and torque distribution through the whole r.p.m. range.