This invention relates to a method for the angular adjustment of transmission elements. It relates, more particularly, to a method for the relative angular adjustment of a first transmission element, which is rotatable about a first centre axis, and a last transmission element, which is rotatable about a last centre axis, the last centre axis being different from the first centre axis, and the first and the last transmission elements being rotationally interconnected by means of at least a second transmission element, which is rotatable about a second centre axis, and a penultimate transmission element, which is rotatable about a penultimate centre axis. The invention also includes a device for the relative angular adjustment of transmission elements.

When using co-rotating transmission elements, that is to say transmission elements that are rotationally interconnected by means of, for example, gears, a chain or toothed-belt transmission, there may be a need to change the angle of rotation, also called the phase angle, between the transmission elements. The relevant transmission elements often rotate at the same speed.

An example of such a change is known from combustion engines in which the angle of rotation of, for example, the camshaft for the suction valves is changed relative to the angle of rotation of the crankshaft or, alternatively, relative to the angle of rotation of the camshaft for the exhaust valves.

It is known to use a hydraulic actuator to turn the camshaft relative to the gear of the camshaft, which requires the supply of a pressure medium with associated control equipment, and which may often be complicating for the total design. Often, the lubricating oil is used as the pressure medium, if it is a question of a combustion engine. This may increase the risk of various faults in the lubrication system of the engine. Devices of this kind often have an on/off function, that is to say they have a discrete function, but also several devices exist in which the adjustment may be regulated continuously. In addition, a hydraulically operated system, for example, might require some maintenance, as hydraulic components are often sensitive to a deteriorated quality of the hydraulic medium and any particles present in it. This contributes to increasing the need for maintenance and to reducing the life of the solution, which is not desirable.

It is also known to use mechanical differential solutions and planetary-gear solutions and variations of these in order to change the relative angle of rotation of co-rotating transmission elements, see for example US 20120222513.

Such devices are often relatively complicated with gears and/or actuators in several planes.

The invention has for its object to remedy or reduce at least one of the drawbacks of the prior art.

The object is achieved according to the invention through the features that are specified in the description below and in the claims that follow.

According to a first aspect of the invention, a method is provided for the relative angular adjustment of a first transmission element, which is rotatable about a first centre axis, and a last transmission element, which is rotatable about a last centre axis, the last centre axis being different from the first centre axis, and the first and the last transmission elements being rotationaiiy interconnected by means of at least a second transmission element, which is rotatable about a second centre axis, and a penultimate transmission element, which is rotatable about a penultimate centre axis, the method being characterized by including :

- arranging the second centre axis in a manner that makes it rotatable about the first centre axis; and

- rotating the second centre axis about the first centre axis.

Below, a perpendicular line between the first centre axis and the last centre axis is called a first axis line. The first axis line has a length equal to the distance between the first centre axis and the last centre axis.

Correspondingly, a second axis line extends between the first centre axis and the second centre axis, a third axis line between the second centre axis and the penultimate centre axis, and a fourth axis line between the penultimate centre axis and the last centre axis.

By an angular deflection of the second axis line relative to the first axis line, that is to say the second centre axis being rotated about the first centre axis, the second transmission element is brought to rotate through an angle of rotation about the second centre axis. This angle of rotation is transmitted to the penultimate transmission element, which rotates through a corresponding angle of rotation about the penultimate centre axis. The angle of rotation is further transmitted to the last transmission element, which rotates about the last centre axis.

The method may include arranging the penultimate centre axis in a manner that makes it rotatable about the last centre axis.

In that case, the angular adjustment of the last transmission element comprises the sum of the angle of rotation transmitted from the second transmission element and an angle of deflection between the fourth axis line and the first axis line.

The total angle of rotation of the penultimate transmission element about the penultimate centre axis is given as a result of positional and rotational changes of the transmission elements relative to each other, changes that propagate through every link in the assembly of these. A further rotation of the last transmission element about the last centre axis may occur in consequence of the positional changes of the various engagement elements.

The gear ratio of said angular deflection of the second transmission element and the angular deflection of the last transmission element may be chosen by, for example, adjusting the angle between the second axis line and the fourth axis line. The change in the angle of rotation of the last transmission element is normally not linear relative to the angular deflection between the second axis line and the first axis line.

According to a second aspect of the invention, a device for the relative angular adjustment of a first transmission element, which is rotatable about a first centre axis, and a last transmission element, which is rotatable about a last centre axis, is provided, the last centre axis being different from the first centre axis, and the first and the last transmission elements being rotationally interconnected by means of at least a second transmission element, which is rotatable about a second centre axis, and a penultimate transmission element, which is rotatable about a penultimate centre axis, the device being characterized by the second centre axis being rotatable about the first centre axis.

The penultimate centre axis may be rotatable about the last centre axis.

If the penultimate centre axis is not rotatable about the last centre axis, the distance between the first centre axis and the last centre axis, the first axis line, may have to be changed when the second centre axis is rotated about the first centre axis.

The first and the last centre axes may advantageously have a fixed spacing.

The second transmission element and the penultimate transmission element may be rotationally interconnected via at least a third transmission element.

Such a solution makes it possible to choose the direction of rotation for the last transmission element relative to the first transmission element. Further, the angle between the first axis line and the fourth axis line may be fixed while, at the same time, the length of the first axis line is fixed, as the third centre axis of the third transmission element may be rotatable about the second centre axis.

The distances between the first and the second centre axes, the second and the penultimate centre axes, and between the penultimate and the last centre axes, respectively, are typically fixed, but may in some cases be variable.

At least one of the transmission elements may consist of a toothed wheel. In a preferred embodiment all the transmission elements consist of toothed wheels, all the toothed wheels having the same number of teeth. In some applications it may be practical for one or more of the transmission elements to have a different number of teeth.

In alternative embodiments, at least one of the transmission elements may consist of a toothed-belt wheel with an associated toothed belt or a chain wheel with an associated chain.

A change in the angle between the first axis line and the second axis line can be made by means of an actuator of any known kind, for example a mechanical, electric or hydraulic one. In the exemplary embodiment shown in the characterizing part of the description, arrangements have been made for using a so-called stepper motor.

In a further embodiment, a driving element may be fitted as well, for example a toothed wheel, sitting on the same axle as any one of the transmission elements mentioned. Such a driving element may be in further engagement with a driving source, which may also include an engagement device corresponding to the driving element, for example a toothed wheel.

A method and a device according to the invention enable interangular adjustment of co-rotating transmission elements by means of mechanical means. All transmission elements that are mutually in mesh are preferably in the same plane. The method and the device further enable a continuous adjustment between the transmission elements.

In what follows, an example of a preferred method and embodiment is described, which is visualized in the accompanying drawings, in which :

Figure 1 shows a side view of an angular-adjustment device according to the invention in a starting position;

Figure 2 shows a section I-I of figure 1;

Figure 3 shows a simplified sketch of transmission elements of figure 1;

Figure 4 shows the same as figure 3, but after a certain angular adjustment has taken place;

Figure 5 shows the same as figure 4, but after a further angular adjustment has taken place;

Figure 6 shows a simplified sketch of an alternative embodiment;

Figure 7 shows the device of figure 1 after an angular adjustment has taken place; and

Figure 8 shows the angular-adjustment device in a further exemplary embodiment.

In the drawings, the reference numeral 1 indicates an angular-adjustment device including a first transmission element 2, which is connected to a first axle 4, the first axle 4 having a first centre axis 6.

A second transmission element 8, which is in mesh with the first transmission element 2 is supported around a second axle 10 with a second centre axis 12.

A penultimate transmission element 14, which is in mesh with the second transmission element 8 is supported around a penultimate axle 16 with a penultimate centre axis 18.

A last transmission element 20, which is in mesh with the penultimate transmission element 14 is connected to a last axle 22, which has a last centre axis 24. The last centre axis 24 is at a distance from the first centre axis 6. In this preferred exemplary embodiment, all the transmission elements 2, 8, 14, 20 are toothed wheels with the same number of teeth.

The first axle 4 and the last axle 22 are both rotatably supported in a bracket 26. All bearings have been given the reference numeral 28 in the drawings, but will not be described any further as their operation and purpose are obvious to a person skilled in the art.

An adjusting arm 30 is supported around the first axle 4 and thereby rotatable about the first centre axis 6. The second axle 10 is attached to the adjusting arm 30. A link arm 32 is connected at its respective end portions to the second axle 10 and the penultimate axle 16, respectively.

The penultimate axle 16 is attached to a rotary arm 34, which is rotatably supported around the last axle 22.

The adjusting arm 30 is provided with a toothed sector 36, which is arranged for engagement with the toothed wheel of a step motor not shown. A spring 37 is arranged to ensure that the angular-adjustment device 1 is in the desired position, for example at the start or by a fault condition.

The operation of the angular-adjustment device 1 will now be explained with reference to the figures 3-5. It has been taken as a starting point here that the first transmission element 2 does not rotate.

In figure 3, the transmission elements 2, 8, 14, 20 are in the same position as shown in figure 1. A first axis line 38 extends between the first centre axis 6 and the last centre axis 24. A second axis line 40 extends between the first centre axis 6 and the second centre axis 12. Correspondingly, a third axis line 42 extends between the second centre axis 12 and the penultimate centre axis 18, and a fourth axis line 44 extends between the penultimate centre axis 18 and the last centre axis 24.

In figures 3-6, all transmission elements 2, 8, 14, 20 have been given marks 46 at their starting positions of engagement with respective adjacent transmission elements 2, 8, 14, 20. Also, marks 48 have been put on the first and last transmission elements 2, 20, the marks 48 corresponding, in the starting position, to the first axis line 38.

When the adjusting arm 30 and thereby the second axis line 40 are subjected to a first angular deflection 50, the second transmission element 8 is rotated through an angle of rotation 52 about the second centre axis 12, see figure 4. This rotation is transmit- ted to the penultimate transmission element 14, which rotates through the same angle of rotation 52; in the opposite direction, though.

Because of the link arm's 32 connecting the adjusting arm 30 and the rotary arm 34, the fourth axis line 44, too, is rotated through a first deflection angle 54. The total first angular adjustment of the last transmission element 20 comprises the angle of rotation 52 and the first deflection angle 54 and is indicated by the angle 56 in figure 4. The immediate angular deflection of the last transmission element 20 is thus dependent on both the deflection of the adjusting arm 30 and its given position when the rotation takes place.

In figure 5, the adjusting arm 30 and the second axis line 40 has been rotated to a second angular deflection 58, resulting in an adjustment of the last transmission element 20 as indicated by the angle 60.

In an alternative embodiment, see figure 6, a third transmission element 62 is arranged between the second transmission element 8 and the penultimate transmission element 14.

The inclusion of the third transmission element 62, changes the direction of rotation of the last transmission element 20. Otherwise, the operation is the same as that explained above.

Figure 8 shows a further exemplary embodiment, in which a chain 64 cooperates with the first transmission element 2 and the second transmission element 8, which are adapted for chain operation. A toothed belt 66 cooperates with the penultimate transmission element 14 and the last transmission element 20, which are adapted for toothed-belt operation. In figure 8, the first transmission element 2 and the last transmission element 20 are hidden behind the adjusting arm 30 and the rotary arm 34, respectively.

The bracket 26 may with advantage be provided with a leading mark 70 indicating a starting position for the angular-adjustment device 1.