A method concerns producing a cam profile of a cam pack with at least two cam elements that can be adjusted relative to each other. The camshaft may comprise an outer shaft, a rotatable inner shaft, a fixed cam element connected to the outer shaft, and an adjustment cam element connected to the inner shaft. The method may comprise processing an adjustment cam contour by a continuous diameter reduction of a segment of the adjustment cam base circle, wherein the adjustment cam base circle is reduced to a diameter that is smaller than a fixed cam nominal circle diameter minus a doubled adjustment cam base circle tolerance. The method may comprise processing a fixed cam contour by reducing a fixed cam contour protrusion in a region between a transition point and a processing point. Upon reaching the transition point a tapping element for converting a revolving motion of the cam elements into a linear motion of the valves is transferred from the fixed cam element to the adjustment cam element.

An adjustable camshaft, which can be utilized in a motor vehicle, may include at least one fixed cam arranged rotationally fixed on at least one outer shaft segment and at least one adjusting cam arranged rotationally fixed to an inner shaft extending concentrically within the outer shaft segment. A method for producing such an adjustable camshaft may involve arranging an outer shaft segment on an inner shaft, generating a surface modification on a surface of the inner shaft to generate at least one arranging section, arranging a fixed cam on at least one section of the outer shaft segment, and arranging the adjusting cam on the arranging section of the inner shaft.

A variable valve gear for an internal combustion engine includes: a cam base portion integrally or separately provided in a camshaft, and immovably fixed to the camshaft; a cam lobe portion connected to the cam base portion so as to swing and shift between a first state where the cam lobe portion is positioned to project from an outer circumference of the base portion and a second state where the cam lobe portion is positioned to be lower than the cam base portion in the first state; a lock mechanism locking the cam lobe portion in the first and second state; and a biasing member biasing the cam lobe portion to be shifted to the first state, to such an extent that the cam lobe portion is shifted to the second state by reaction force from a cam follower when the locking mechanism is unlocked.

A composite profile evaluating method includes an adjusting step and a composite profile detecting step. In the adjusting step, a relative position between a fixed cam and a movable cam is adjusted. In the composite profile detecting step, at least either one of a first contact element, which is displaced along a diametrical direction of the fixed cam upon contacting a cam surface of the fixed cam, and a second contact element, which is displaced integrally with the first contact element and along a diametrical direction of the movable cam upon contacting a cam surface of the movable cam, is brought into contact with the cam surface of the fixed cam or the movable cam. In such a state, the composite profile is obtained by rotating the fixed cam and the movable cam, and detecting the amounts of displacement of the first and second contact elements.

A camshaft includes, as a cam that opens and closes an exhaust valve and an intake valve, a ball cam whose protrusion amount changes according to rotation of the camshaft, wherein the camshaft has a double structure consisting of an inner shaft and an outer shaft provided in a manner that the inner shaft is helically displaced with respect to the outer shaft around an axis of the camshaft according to a rotation speed of the camshaft, and the ball cam is accommodated movably in a guide groove provided in the inner shaft and protrudes from the outer shaft, and a protrusion amount of the ball cam from the outer shaft changes when the ball cam moves in the guide groove due to the helical displacement of the inner shaft with respect to the outer shaft.

In an exemplary embodiment, an internal combustion engine, in which a valve is opened and closed when a piston reciprocates in a cylinder, has a configuration to perform repeatedly the following combined strokes: an intake stroke.fwdarw.a compression stroke.fwdarw.a combustion stroke.fwdarw.an exhaust stroke in a four-cycle internal combustion engine are combined with an intake and compression stroke.fwdarw.a combustion and exhaust stroke in a two-cycle internal combustion engine. The internal combustion engine can reduce pumping loss in a six-cycle internal combustion engine and increase the output.

A camshaft includes, as a cam that opens and closes an exhaust valve and an intake valve, a ball cam whose protrusion amount changes according to rotation of the camshaft, wherein the camshaft has a double structure consisting of an inner shaft and an outer shaft provided in a manner that the inner shaft is helically displaced with respect to the outer shaft around an axis of the camshaft according to a rotation speed of the camshaft, and the ball cam is accommodated movably in a guide groove provided in the inner shaft and protrudes from the outer shaft, and a protrusion amount of the ball cam from the outer shaft changes when the ball cam moves in the guide groove due to the helical displacement of the inner shaft with respect to the outer shaft.

In an exemplary embodiment, an internal combustion engine, in which a valve is opened and closed when a piston reciprocates in a cylinder, has a configuration to perform repeatedly the following combined strokes: an intake stroke.fwdarw.a compression stroke.fwdarw.a combustion stroke.fwdarw.an exhaust stroke in a four-cycle internal combustion engine are combined with an intake and compression stroke.fwdarw.a combustion and exhaust stroke in a two-cycle internal combustion engine. The internal combustion engine can reduce pumping loss in a six-cycle internal combustion engine and increase the output.

A method concerns producing a cam profile of a cam pack with at least two cam elements that can be adjusted relative to each other. The camshaft may comprise an outer shaft, a rotatable inner shaft, a fixed cam element connected to the outer shaft, and an adjustment cam element connected to the inner shaft. The method may comprise processing an adjustment cam contour by a continuous diameter reduction of a segment of the adjustment cam base circle, wherein the adjustment cam base circle is reduced to a diameter that is smaller than a fixed cam nominal circle diameter minus a doubled adjustment cam base circle tolerance. The method may comprise processing a fixed cam contour by reducing a fixed cam contour protrusion in a region between a transition point and a processing point. Upon reaching the transition point a tapping element for converting a revolving motion of the cam elements into a linear motion of the valves is transferred from the fixed cam element to the adjustment cam element.

A camshaft for a valve drive of an internal combustion engine having a variable valve opening time may include an outer shaft and an inner shaft that extends through the outer shaft, with the inner shaft being held rotatably with respect to the outer shaft. The camshaft may further include a cam having a multiple-piece configuration, comprising a first part cam and a second part cam. Either the first part cam or the second part cam may be connected fixedly to the outer shaft so as to rotate with it, and the other part cam may be connected fixedly to the inner shaft so as to rotate with it. The camshaft may also include a bearing inner ring of a shaft bearing that is held on the outer shaft, with one of two second part cams comprising an axial attachment that forms at least one part of the bearing inner ring.